Light-emitting element light-emitting device electronic device and lighting device

One aspect of the present invention relates to a light emitting element in which an organic compound capable of emitting light by applying an electric field is sandwiched between a pair of electrodes, and a light emitting device, an electronic device, and a lighting device having such a light emitting element.

Light emitting devices that use organic compounds as light emitters, which are thin and lightweight, have high-speed responsiveness, and are driven by DC low voltage, are expected to be applied to next-generation flat panel displays. In particular, a display device in which light emitting elements are arranged in a matrix is considered to be superior in that it has a wide viewing angle and excellent visibility as compared with a conventional liquid crystal display device.

In the light emitting mechanism of the light emitting element, by sandwiching an EL layer containing a light emitter between a pair of electrodes and applying a voltage, electrons injected from the cathode and holes injected from the anode are regenerated at the light emitting center of the EL layer. It is said that they combine to form a molecular exciter, and when the molecular excitator relaxes to the ground state, it releases energy and emits light. Singlet and triplet excitations are known as excited states, and it is considered that light emission is possible through either excited state.

With respect to such a light emitting element, in order to improve the element characteristics, improvement of the element structure and material development are actively carried out (see, for example, Patent Document 1).

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2010-182699</text></patcit></p>

<p> However, the light extraction efficiency of the light emitting element at present is said to be about 20% to 30%, and even considering the absorption of light by the reflective electrode and the transparent electrode, the external quantum efficiency of the light emitting element using the phosphorescent compound. The limit of is considered to be about 25%.</p><p> Therefore, in one aspect of the present invention, a light emitting device having high external quantum efficiency is provided. Further, one aspect of the present invention provides a light emitting device having a long life.</p>

<p> One aspect of the present invention has a light emitting layer between a pair of electrodes, wherein the light emitting layer has a phosphorescent compound, a first organic compound having electron transportability (host material), and a second light emitting layer having hole transportability. The light emitting layer has at least an organic compound (assist material) of the above, and the light emitting layer has a laminated structure of a first light emitting layer and a second light emitting layer, and the first light emitting layer has a higher light emitting layer than the second light emitting layer. It is a light emitting element characterized by containing a large amount of a second organic compound. Further, in the light emitting layer (the first light emitting layer and the second light emitting layer), the first organic compound and the second organic compound are characterized by being a combination forming an excitation complex.</p><p> Further, another aspect of the present invention has a light emitting layer between the anode and the cathode, a hole transport layer between the anode and the light emitting layer, and electron transport between the cathode and the light emitting layer. It has a layer, and the light emitting layer contains at least a phosphorescent compound, a first organic compound having electron transporting property, and a second organic compound having hole transporting property, and is formed in contact with the hole transporting layer. A first light emitting layer containing at least a phosphorescent compound, a first organic compound having an electron transporting property, and a second organic compound having a hole transporting property, and formed in contact with the electron transporting layer. It is a stack with the second light emitting layer, and the first organic compound and the second organic compound form an excitation complex, and the first light emitting layer has more second organic compounds than the second light emitting layer. It is a light emitting element characterized by being included.</p><p> In each of the above configurations, the emission wavelengths of the excitation complex formed by the first organic compound (host material) and the second organic compound (assist material) are the first organic compound (host material) and the second organic compound (host material). Since it exists on the longer wavelength side than each emission wavelength (fluorescence wavelength) of the organic compound (assist material), by forming an excitation complex, the fluorescence spectrum of the first organic compound (host material) and the first The fluorescence spectrum of the organic compound (assist material) of 2 can be converted into an emission spectrum located on the longer wavelength side.</p><p> Therefore, the light emitting element according to one aspect of the present invention exists on the longer wavelength side than the emission wavelength (fluorescence wavelength) of each of the first organic compound and the second organic compound by forming an excited complex in the light emitting layer. Energy transfer can be performed using the overlap between the emission spectrum of the excited complex and the absorption spectrum of the phosphorescent compound (guest material), and it is possible to realize a light emitting element with high energy transfer efficiency and high external quantum efficiency. can.</p><p> In the above configuration, the phosphorescent compound contained in the light emitting layer may be the same as or different between the substance contained in the first light emitting layer and the substance contained in the second light emitting layer. However, when they are different, the light emitted from the first light emitting layer is characterized by having a shorter wavelength than the light emitted from the second light emitting layer.</p><p> The above configuration is characterized in that an excited complex is formed from the anion of the first organic compound and the cation of the second organic compound.</p><p> Further, in the above configuration, the phosphorescent compound is an organometallic complex, and the first organic compound is mainly 10^-6cm²An electron-transporting material having electron mobility of / Vs or more, specifically, a π-electron-deficient heteroaromatic compound, and the second organic compound is mainly 10^-6cm²It is characterized by being a hole transporting material having a hole mobility of / Vs or more, specifically, a π-electron excess type heteroaromatic compound or an aromatic amine compound.</p><p> Further, one aspect of the present invention includes not only a light emitting device having a light emitting element but also an electronic device having a light emitting device and a lighting device. Therefore, the light emitting device in the present specification refers to an image display device, a light emitting device, or a light source (including a lighting device). In addition, a module in which a connector such as FPC (Flexible printed circuit) or TCP (Tape Carrier Package) is attached to the light emitting device, a module in which a printed wiring board is provided at the end of TCP, or COG (Chip On Glass) in the light emitting element. All modules to which an IC (integrated circuit) is directly mounted by the method shall be included in the light emitting device.</p>

<p> The light emitting element according to one aspect of the present invention exists on the longer wavelength side than the emission wavelength (fluorescence wavelength) of each of the first organic compound and the second organic compound by forming an excited complex in the light emitting layer. Since energy transfer can be performed by utilizing the overlap between the emission spectrum of the excited complex and the absorption spectrum of the phosphorescent compound (guest material), it is possible to realize a light emitting element having high energy transfer efficiency and high external quantum efficiency. Can be done.</p><p> Further, the light emitting layer in one aspect of the present invention has a laminated structure of a first light emitting layer and a second light emitting layer, and both the first light emitting layer and the second light emitting layer have electron transportability. It contains a first organic compound (host material) and a second organic compound (assist material) having hole transport properties, and the first light emitting layer is a second organic compound (a second light emitting layer) rather than the second light emitting layer. By adopting a configuration containing a large amount of assist material), the balance of carriers (both holes and electrons) in the light emitting layer is improved, and the exciters formed in the light emitting layer are separated into the first light emitting layer and the second light emitting layer. It can be distributed at the interface of the layer. This makes it possible to prevent deterioration of the light emitting layer due to the local increase in exciton density.</p>

<figref num="1">The figure explaining the concept of one aspect of this invention.</figref><figref num="2">The figure which shows the calculation result which concerns on one aspect of this invention.</figref><figref num="3">The figure which shows the calculation result which concerns on one aspect of this invention.</figref><figref num="4">The figure explaining the energy level of the excitation complex applied in one aspect of this invention.</figref><figref num="5">The figure explaining the structure of a light emitting element.</figref><figref num="6">The figure explaining the structure of a light emitting element.</figref><figref num="7">The figure explaining the light emitting device.</figref><figref num="8">The figure explaining the light emitting device.</figref><figref num="9">The figure explaining the electronic device.</figref><figref num="10">The figure explaining the electronic device.</figref><figref num="11">The figure explaining the lighting equipment.</figref><figref num="12">The figure explaining the structure of a light emitting element 1.</figref><figref num="13">The figure which shows the current density-luminance characteristic of a light emitting element 1.</figref><figref num="14">The figure which shows the voltage-luminance characteristic of a light emitting element 1.</figref><figref num="15">The figure which shows the luminance-current efficiency characteristic of a light emitting element 1.</figref><figref num="16">The figure which shows the voltage-current characteristic of a light emitting element 1.</figref><figref num="17">The figure which shows the emission spectrum of a light emitting element 1.</figref><figref num="18">The figure which shows the reliability of a light emitting element 1.</figref><figref num="19">The figure which shows the current density-luminance characteristic of a light emitting element 2.</figref><figref num="20">The figure which shows the voltage-luminance characteristic of a light emitting element 2.</figref><figref num="21">The figure which shows the luminance-current efficiency characteristic of a light emitting element 2.</figref><figref num="22">The figure which shows the voltage-current characteristic of a light emitting element 2.</figref><figref num="23">The figure which shows the emission spectrum of a light emitting element 2.</figref><figref num="24">The figure explaining the structure of a light emitting element 3.</figref><figref num="25">The figure which shows the current density-luminance characteristic of a light emitting element 3.</figref><figref num="26">The figure which shows the voltage-luminance characteristic of a light emitting element 3.</figref><figref num="27">The figure which shows the luminance-current efficiency characteristic of a light emitting element 3.</figref><figref num="28">The figure which shows the voltage-current characteristic of a light emitting element 3.</figref><figref num="29">The figure which shows the emission spectrum of a light emitting element 3.</figref><figref num="30">The figure which shows the current density-luminance characteristic of a light emitting element 4.</figref><figref num="31">The figure which shows the voltage-luminance characteristic of a light emitting element 4.</figref><figref num="32">The figure which shows the luminance-current efficiency characteristic of a light emitting element 4.</figref><figref num="33">The figure which shows the voltage-current characteristic of a light emitting element 4.</figref><figref num="34">The figure which shows the emission spectrum of a light emitting element 4.</figref><figref num="35">The figure which shows the reliability of a light emitting element 4.</figref><figref num="36">The figure which shows the current density-luminance characteristic of a light emitting element 5.</figref><figref num="37">The figure which shows the voltage-luminance characteristic of a light emitting element 5.</figref><figref num="38">The figure which shows the luminance-current efficiency characteristic of a light emitting element 5.</figref><figref num="39">The figure which shows the voltage-current characteristic of a light emitting element 5.</figref><figref num="40">The figure which shows the emission spectrum of a light emitting element 5.</figref><figref num="41">The figure which shows the reliability of a light emitting element 5.</figref><figref num="42">The figure which shows the current density-luminance characteristic of a light emitting element 6.</figref><figref num="43">The figure which shows the voltage-luminance characteristic of a light emitting element 6.</figref><figref num="44">The figure which shows the luminance-current efficiency characteristic of a light emitting element 6.</figref><figref num="45">The figure which shows the voltage-current characteristic of a light emitting element 6.</figref><figref num="46">The figure which shows the emission spectrum of a light emitting element 6.</figref><figref num="47">The figure which shows the reliability of a light emitting element 6.</figref>

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and its form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention is not construed as being limited to the description of the embodiments shown below.

(Regarding the elementary process of light emission in a light emitting device) First, a general elementary process of light emission in a light emitting device using a phosphorescent compound as a guest material will be described. Here, the molecule that gives the excitation energy is referred to as a host molecule, and the molecule that receives the excitation energy is referred to as a guest molecule.

(1) When electrons and holes (holes) are recombined in the guest molecule and the guest molecule is in an excited state (direct recombination process).

(1-1) When the excited state of the guest molecule is the triplet excited state, the guest molecule emits phosphorescence.

(1-2) When the excited state of the guest molecule is the singlet excited state The guest molecule in the singlet excited state crosses the triplet excited state between the terms and emits phosphorescence.

That is, in the direct recombination process of (1) above, high luminous efficiency can be obtained as long as the intersystem crossing efficiency of the guest molecule and the phosphorescence quantum yield are high. The T1 level of the host molecule is preferably higher than the T1 level of the guest molecule.

(2) When electrons and holes (holes) recombine in the host molecule and the host molecule becomes excited (energy transfer process).

(2-1) When the excited state of the host molecule is the triple-term excited state When the T1 level of the host molecule is higher than the T1 level of the guest molecule, the excitation energy is transferred from the host molecule to the guest molecule, and the guest molecule moves. It becomes a triplet excited state. The guest molecule in the triplet excited state emits phosphorescence. Note that energy transfer from the T1 level of the host molecule to the level (S1 level) of the single-term excitation energy of the guest molecule is prohibited unless the host molecule emits phosphorescence, and it is unlikely to become the main energy transfer process. It is omitted here. That is, as shown in the following equation (2-1), the energy transfer from the triplet excited state (3H *) of the host molecule to the triplet excited state (3G *) of the guest molecule is important (in the equation, 1G is the guest). The singlet ground state of the molecule, 1H represents the singlet ground state of the host molecule).

3H * + 1G 1H + 3G * (2-1)

(2-2) When the excited state of the host molecule is the single-term excited state When the S1 level of the host molecule is higher than the S1 level and T1 level of the guest molecule, the excited energy is transferred from the host molecule to the guest molecule. , The guest molecule is in a single-term excited state or a triple-term excited state. The guest molecule in the triplet excited state emits phosphorescence. In addition, the guest molecule in the singlet excited state crosses the triplet excited state between the terms and emits phosphorescence.

That is, as shown in the following equation (2-2A), energy is transferred from the singlet excited state (1H *) of the host molecule to the singlet excited state (1G *) of the guest molecule, and then the triplet of the guest molecule is transferred by intersystem crossing. The process of generating the excited state (3G *) and the direct energy transfer from the singlet excited state (1H *) of the host molecule to the triplet excited state (3G *) of the guest molecule as shown in the following equation (2-2B). The process is conceivable.

1H * + 1G 1H + 1G * (intersystem crossing) 1H + 3G * (2-2A) 1H * + 1G 1H + 3G * (2-2B)

If all the energy transfer processes described in (2) above occur efficiently, both the triplet excited energy and the singlet excited energy of the host molecule are efficiently converted into the triplet excited state (3G *) of the guest molecule. Therefore, highly efficient light emission is possible. On the contrary, if the host molecule itself emits the excitation energy as light or heat and is inactivated before the excitation energy is transferred from the host molecule to the guest molecule, the luminous efficiency is lowered.

Next, the governing factors of the energy transfer process between the host molecule and the guest molecule described above will be described. The following two mechanisms have been proposed as the mechanism of energy transfer between molecules.

First, the Felster mechanism (dipole-dipole interaction), which is the first mechanism, does not require direct contact between molecules for energy transfer, and the resonance of dipole vibration between host and guest molecules. It is a mechanism in which energy transfer occurs through a phenomenon. Due to the resonance phenomenon of bipolar vibration, the host molecule transfers energy to the guest molecule, the host molecule becomes the ground state, and the guest molecule becomes the excited state. The rate constant k of the Felster mechanism_{h * g}Is shown in the formula (1).

<maths num="1"><img file="JP6972276B2_D0001.tif" /></maths>

In equation (1), ν represents the frequency and f'_h(ν) represents the standardized emission spectrum of the host molecule (fluorescence spectrum when discussing energy transfer from singlet excited state, phosphorescence spectrum when discussing energy transfer from triplet excited state)._g(ν) represents the molar absorption coefficient of the guest molecule, N represents the avocadro number, n represents the refractive index of the medium, R represents the intermolecular distance between the host molecule and the guest molecule, and τ represents the intermolecular distance between the host molecule and the guest molecule. The measured lifetime of the excited state (fluorescence lifetime or phosphorescent lifetime) is represented, c is the light velocity, and φ is the emission quantum yield (fluorescence quantum yield when discussing energy transfer from the singlet excited state, triplet). When discussing energy transfer from the term excited state, it represents phosphorous quantum yield), and K²Is a coefficient (0 to 4) representing the orientation of the transition dipole moment between the host molecule and the guest molecule. In the case of random orientation, K²= 2/3.

Next, in the second mechanism, the Dexter mechanism (electron exchange interaction), the host molecule and the guest molecule approach the contact effective distance where the orbital overlap occurs, and the electron in the excited state and the guest molecule in the ground state are approached. Energy transfer occurs through the exchange of electrons in. The speed constant k of the Dexter mechanism_{h * g}Is shown in the formula (2).

<maths num="2"><img file="JP6972276B2_D0002.tif" /></maths>

In equation (2), h is Planck's constant, K'is a constant with the dimension of energy, ν is the frequency, and f'_h(ν) represents the standardized emission spectrum of the host molecule (fluorescence spectrum when discussing energy transfer from singlet excited state, phosphorescence spectrum when discussing energy transfer from triplet excited state)._g(ν) represents the normalized absorption spectrum of the guest molecule, L represents the effective molecular radius, and R represents the intermolecular distance between the host molecule and the guest molecule.

Here, the energy transfer efficiency Φ from the host molecule to the guest molecule_ETIs considered to be expressed by the formula (3). k_rRepresents the rate constant of the emission process of the host molecule (fluorescence when discussing energy transfer from the singlet excited state, phosphorescence when discussing energy transfer from the triplet excited state)._nRepresents the rate constant of the non-luminescence process (heat deactivation and intersystem crossing) of the host molecule, and τ represents the lifetime of the actually measured excited state of the host molecule.

<maths num="3"><img file="JP6972276B2_D0003.tif" /></maths>

From equation (3), energy transfer efficiency Φ_ETTo increase the energy transfer rate constant k_{h * g}And other competing rate constants k_r+ k_nIt can be seen that (= 1 / τ) should be relatively small.

(Regarding the energy transfer efficiency of (2-1)) First, let us consider the energy transfer process of (2-1). In this case, the Felster type (Equation (1)) is prohibited, so only the Dexter type (Equation (2)) needs to be considered. According to equation (2), the rate constant k_{h * g}Emission spectrum of host molecule (phosphorescence spectrum because we discuss energy transfer from triplet excited state) and absorption spectrum of guest molecule (corresponding to direct transition from singlet ground state to triplet excited state) It can be seen that the larger the overlap with (absorption), the better.

In one aspect of the present invention, the phosphorescent compound is used as a guest material, but in the absorption spectrum of the phosphorescent compound, absorption corresponding to a direct transition from the singlet ground state to the triplet excited state may be observed. , It is the absorption band that appears on the longest wavelength side. In particular, in a luminescent iridium complex, the absorption band on the longest wavelength side often appears as a broad absorption band near 500 to 600 nm (of course, depending on the emission wavelength, it appears on the shorter wavelength side or the longer wavelength side. In some cases). This absorption band is mainly a triplet MLCT (Metal to Ligand Charge). Transfer) Derived from the transition. However, the absorption band also includes some absorption derived from the triplet π-π * transition and the singlet MLCT transition, and these overlap to form a broad absorption band on the longest wavelength side of the absorption spectrum. It is thought that there is. In other words, the difference between the lowest singlet excited state and the lowest triplet excited state is small, and it is considered that the absorptions derived from these overlap to form a broad absorption band on the longest wavelength side of the absorption spectrum. Therefore, when an organic metal complex (particularly an iridium complex) is used as the guest material, the rate constant k is due to the large overlap between the broad absorption band existing on the longest wavelength side and the phosphorescence spectrum of the host material._{h * g}Can be increased and energy transfer efficiency can be improved.

Furthermore, since a fluorescent compound is usually used as the host material, the phosphorescence lifetime (τ) is as long as milliseconds (k)._r+ k_nIs small). This is because the transition from the triplet excited state to the ground state (singlet state) is a forbidden transition. From equation (3), this means energy transfer efficiency Φ_ETWorks in favor of.

Considering the above, the energy transfer from the triplet excited state of the host material to the triplet excited state of the guest material, that is, the process of Eq. (2-1) is the phosphorescence spectrum of the host material and the singlet of the guest material. As long as the absorption spectrum corresponding to the direct transition from the ground state to the triplet excited state is superimposed, it tends to occur as a whole.

(Regarding the energy transfer efficiency of (2-2)) Next, consider the energy transfer process of (2-2). The process of equation (2-2A) is affected by the intersystem crossing efficiency of the guest material. Therefore, in order to increase the luminous efficiency to the utmost limit, the process of Eq. (2-2B) is considered to be important. In this case, the Dexter type (Equation (2)) is prohibited, so only the Felster type (Equation (1)) needs to be considered.

Eliminating τ from equations (1) and (3), energy transfer efficiency Φ_ETIt can be said that the higher the quantum yield φ (fluorescence quantum yield because we are discussing the energy transfer from the singlet excited state), the better. However, in reality, as more important factors, the emission spectrum of the host molecule (fluorescence spectrum because we are discussing the energy transfer from the singlet excited state) and the absorption spectrum of the guest molecule (directly from the singlet ground state to the triplet excited state). It is also necessary to have a large overlap with the absorption corresponding to the transition (note that it is preferable that the molar absorption coefficient of the guest molecule is also high). This means that the fluorescence spectrum of the host material and the absorption band appearing on the longest wavelength side of the phosphorescent compound, which is the guest material, overlap.

However, it has been very difficult to achieve this in the past. This is because, in order to efficiently perform both the process (2-1) and the process (2-2) described above, from the above discussion, not only the phosphorescence spectrum of the host material but also the fluorescence spectrum of the guest material is used. This is because it must be designed so as to overlap with the absorption band on the longest wavelength side. In other words, the host material must be designed so that the fluorescence spectrum of the host material is at a position similar to the phosphorescence spectrum.

However, in general, since the S1 level and the T1 level are significantly different (S1 level&gt; T1 level), the emission wavelength of fluorescence and the emission wavelength of phosphorescence are also significantly different (emission wavelength of fluorescence &lt;emission wavelength of phosphorescence). For example, 4,4'-di (N-carbazolyl) biphenyl (abbreviation: CBP), which is often used as a host material in a light emitting element using a phosphorescent compound, has a phosphorescent spectrum near 500 nm, but on the other hand, a fluorescence spectrum. Is around 400 nm, with a gap of 100 nm. Considering this example as well, it is extremely difficult to design the host material so that the fluorescence spectrum of the host material is located at the same position as the phosphorescence spectrum. Therefore, improving the efficiency of energy transfer from the singlet excited state of the host material to the guest material is very important.

Therefore, one aspect of the present invention provides a useful method capable of overcoming the problem of energy transfer efficiency from the singlet excited state of the host material to the guest material. The specific embodiment will be described below.

(Embodiment 1) In the present embodiment, a concept and a specific configuration of a light emitting element for configuring a light emitting element, which is one aspect of the present invention, will be described. The light emitting element according to one aspect of the present invention is formed by sandwiching an EL layer including a light emitting layer between a pair of electrodes, and the light emitting layer is formed by a guest material which is a phosphorescent compound and a first organic compound. And a second organic compound.

First, the element structure of the light emitting device, which is an example of the present invention, will be described with reference to FIG. 1 (A).

In the element structure shown in FIG. 1 (A), an EL layer 103 including a light emitting layer 106 is sandwiched between a pair of electrodes (anode 101, cathode 102), and the EL layer 103 has holes (holes) from the anode 101 side. ) It has a structure in which an injection layer 104, a hole transport layer 105, a light emitting layer 106 (106a, 106b), an electron transport layer 107, an electron injection layer 108, and the like are sequentially laminated.

Further, the light emitting layer 106 in one aspect of the present invention is a layer containing a phosphorescent compound 109, which is a guest material, a first organic compound 110, and a second organic compound 111, as shown in FIG. 1 (A). The first organic compound 110 is mainly 10^-6cm²Using an electron transporting material with electron mobility of / Vs or higher, the second organic compound 111 is mainly 10^-6cm²A hole transporting material having a hole mobility of / Vs or higher shall be used. Further, in the present specification, the first organic compound 110 is referred to as a host material, and the second organic compound 111 is referred to as an assist material.

In the above configuration, the triplet excitation energy level (T1 level) of each of the first organic compound (host material) 110 and the second organic compound (assist material) 111 is a phosphorescent compound (guest material). ) Preferably higher than the T1 level of 109. When the T1 level of the first organic compound 110 (or the second organic compound 111) is lower than the T1 level of the phosphorescent compound 109, the triple-term excitation energy of the phosphorescent compound 109 that contributes to light emission is the first. This is because the organic compound 110 (or the second organic compound 111) is extinguished (quenched), resulting in a decrease in light emission efficiency.

Further, the light emitting layer 106 according to one aspect of the present invention is characterized by having a structure in which light emitting layers having different proportions of the second organic compound (assist material) 111 contained in the light emitting layer 106 are laminated. Specifically, as shown in FIG. 1A, the light emitting layer 106 has a laminated structure of the first light emitting layer 106a and the second light emitting layer 106b, and the second organic layer in the first light emitting layer 106a. The proportion of the compound (assist material) 111 contained is larger than the proportion of the second organic compound (assist material) 111 contained in the second light emitting layer 106b.

Further, each of the first light emitting layer 106a and the second light emitting layer 106b constituting the light emitting layer 106 contains the first organic compound (host material) 110 and the second organic compound (assist material) 111. In the present invention, either case may be included.

If the ratio of the second organic compound (assist material) 111, which is a hole transporting material, is small in the first light emitting layer 106a having the above structure, the light emitting region is the anode of the first light emitting layer 106a. It will be biased to the side (hole transport layer 105 side). On the other hand, if the amount of the second organic compound (assist material) 111 in both the first light emitting layer 106a and the second light emitting layer 106b becomes too large, carriers (both holes and electrons) easily penetrate the light emitting layer 106. This will reduce the recombination efficiency. However, by adopting the configuration of one aspect of the present invention described in FIG. 1 (A), the hole transport property of the first light emitting layer 106a is relative to the hole transport property of the second light emitting layer 106b. Since the electron transportability is reversed, the excitons are not biased around the interface between the first light emitting layer 106a and the second light emitting layer 106b, and do not deviate from the inside of the light emitting layer 106. Can be distributed. As a result, it is possible to prevent bias of excitons inside the light emitting layer 106, and it is possible to prevent deterioration of the light emitting layer 106 due to an increase in the density of excitons. Further, since the carrier can be prevented from penetrating from the light emitting layer 106, the luminous efficiency can be kept high.

Here, in both the first light emitting layer 106a and the second light emitting layer 106b, the first organic compound (host material) 110 and the second organic compound (assist material) 111 are excited complexes (exciplex:: It is characterized by being a combination that forms an excimer (also called an excimer). Further, the emission wavelength of the formed excitation complex is on the longer wavelength side than the emission wavelengths (fluorescence wavelengths) of the first organic compound (host material) 110 and the second organic compound (assist material) 111. Since it exists, the fluorescence spectrum of the first organic compound (host material) 110 and the fluorescence spectrum of the second organic compound (assist material) 111 can be converted into an emission spectrum located on the longer wavelength side.

This means that, as shown in FIG. 1 (B), the fluorescence spectrum of the first organic compound 110 (or the second organic compound 111) is located on the longest wavelength side of the phosphorescent compound (guest material) 109. Even if there is no overlap with the absorption band located on the short wavelength side of the absorption band and located on the longest wavelength side of the phosphorescent compound (guest material) 109, the overlap can be achieved by forming an excitation complex. It means that you can make it bigger. This makes it possible to improve the energy transfer efficiency of the above-mentioned equation (2-2B).

Furthermore, it is considered that the difference between the singlet excitation energy and the triplet excitation energy of the excitation complex is extremely small. In other words, the emission spectra from the singlet state and the emission spectra from the triplet state of the excited complex are very close to each other. Therefore, as described above, when the emission spectrum of the excited complex (generally, the emission spectrum from the single-term state of the excited complex) is designed to be superimposed on the absorption band located on the longest wavelength side of the phosphorescent compound, the excited complex The emission spectrum from the tripled state (which is not observed at room temperature and is often not observed at low temperature) also overlaps with the absorption band located on the longest wavelength side of the phosphorescent compound. In other words, not only the energy transfer from the singlet excited state ((2-2)) but also the efficiency of the energy transfer from the triplet excited state ((2-1)) is increased, and as a result, the singlet / triplet Both can be efficiently converted into light emission.

Therefore, whether or not the excited complex actually has such characteristics is verified below using molecular orbital calculation. In general, the combination of a heteroaromatic compound and an aromatic amine is a LUMO level (easy to enter electrons) of a complex aromatic compound that is deeper than the lowest unoccupied molecular orbital (LUMO) level of the aromatic amine. Forming an excited complex due to the influence of the HOMO level (property of easy hole entry) of aromatic amines that are shallower than the HOMO (Highest Occupied Molecular Orbital) level of complex aromatic compounds. There are many. Therefore, as a model of the first organic compound 110 in one aspect of the present invention, dibenzo [f, h] quinoxalin (abbreviation: DBq) having a typical skeleton constituting LUMO of a heteroaromatic compound is used, and one of the present inventions is used. As a model of the second organic compound 111 in the embodiment, triphenylamine (abbreviation: TPA) having a typical skeleton constituting the HOMO of aromatic amine was used, and the calculation was performed by combining these.

First, the time-dependent density functional theory (TD) is used to determine the optimum molecular structure and excitation energy in the lowest excited singlet state (S1) and lowest excited triplet state (T1) of one DBq (abbreviation) molecule and one TPA (abbreviation) molecule. -Calculated using DFT). In addition, the excitation energies were calculated for the DBq (abbreviation) and TPA (abbreviation) dimers.

The total energy of DFT (density general function method) is expressed by the sum of potential energy, electron-electron electrostatic energy, electron kinetic energy, and exchange correlation energy including all complex electron-electron interactions. In DFT, the calculation is fast and highly accurate because the exchange correlation interaction is approximated by a functional of one-electron potential (meaning a function of a function) expressed by electron density. Here, the weight of each parameter related to exchange and correlation energy is specified using B3LYP, which is a mixed functional.

In addition, as a basis function, 6-311 (a basis function of a triple split valence basis set using three shortening functions for each valence orbital) was applied to all atoms.

According to the above-mentioned basis function, for example, in the case of a hydrogen atom, the orbitals of 1s to 3s are considered, and in the case of a carbon atom, the orbitals of 1s to 4s and 2p to 4p are considered. Furthermore, in order to improve the calculation accuracy, a p function was added to hydrogen atoms and a d function was added to other than hydrogen atoms as a polarization basis set.

Gaussian 09 was used as the quantum chemistry calculation program. The calculation was performed using a high performance computer (Altix 4700 manufactured by SGI).

First, the HOMO level and LUMO level were calculated for one molecule of DBq (abbreviation), one molecule of TPA (abbreviation), and a dimer of DBq (abbreviation) and TPA (abbreviation). The HOMO level and LUMO level are shown in Fig. 2, and the distribution of HOMO and LUMO is shown in Fig. 3, respectively.

FIG. 3 (A1) shows the distribution of LUMO of one molecule of DBq (abbreviation), FIG. 3 (A2) shows the distribution of HOMO of one molecule of DBq (abbreviation), and FIG. 3 (B1) shows the distribution of TPA (abbreviation). ) The distribution of one molecule of LUMO is shown, Fig. 3 (B2) shows the distribution of one molecule of HOMO (abbreviation), and Fig. 3 (C1) shows the dimer of DBq (abbreviation) and TPA (abbreviation). The distribution of LUMO is shown in Fig. 3 (C2), and the distribution of HOMO of the dimer of DBq (abbreviation) and TPA (abbreviation) is shown.

As shown in Figure 2, the DBq (abbreviation) and TPA (abbreviation) dimer has a deeper (lower) DBq (abbreviation) LUMO level (-1.99eV) than the TPA (abbreviation) LUMO level. It is suggested that the HOMO level (-5.21eV) of TPA (abbreviation), which is shallower (higher) than the HOMO level of DBq, forms an excited complex of DBq (abbreviation) and TPA (abbreviation). Will be done. As can be seen from FIG. 3, LUMO, which is a dimer of DBq (abbreviation) and TPA (abbreviation), is distributed on the DBq (abbreviation) side, and HOMO is distributed on the TPA (abbreviation) side.

Next, the excitation energies obtained from the optimum molecular structure at the S1 and T1 levels of one DBq (abbreviation) molecule are shown. Here, the excitation energies of the S1 level and the T1 level correspond to the wavelengths of fluorescence and phosphorescence emitted by one molecule of DBq (abbreviation), respectively. The excitation energy of the S1 level of one molecule of DBq (abbreviation) was 3.294 eV, and the fluorescence wavelength was 376.4 nm. The excitation energy of the T1 level of one DBq (abbreviation) molecule was 2.460 eV, and the phosphorescence wavelength was 504.1 nm.

In addition, the excitation energy obtained from the optimum molecular structure at the S1 level and T1 level of one TPA (abbreviation) molecule is shown. Here, the excitation energies of the S1 level and the T1 level correspond to the wavelengths of fluorescence and phosphorescence emitted by one TPA (abbreviation) molecule, respectively. The excitation energy of the S1 level of one TPA (abbreviation) molecule was 3.508 eV, and the fluorescence wavelength was 353.4 nm. The excitation energy of the T1 level of one TPA (abbreviation) molecule was 2.610 eV, and the phosphorescence wavelength was 474.7 nm.

Furthermore, the excitation energies obtained from the optimum molecular structures at the S1 and T1 levels of the DBq (abbreviation) and TPA (abbreviation) dimers are shown. The excitation energies of the S1 and T1 levels correspond to the wavelengths of fluorescence and phosphorescence emitted by the DBq (abbreviation) and TPA (abbreviation) dimers, respectively. The excitation energy of the S1 level of the DBq (abbreviation) and TPA (abbreviation) dimers was 2.036 eV, and the fluorescence wavelength was 609.1 nm. The excitation energy of the T1 level of the dimer of DBq (abbreviation) and TPA (abbreviation) was 2.030 eV, and the phosphorescence wavelength was 610.0 nm.

From the above, it can be seen that the phosphorescence wavelength is shifted by a long wavelength of nearly 100 nm in both the DBq (abbreviation) single molecule and the TPA (abbreviation) single molecule. This is the same tendency as the above-mentioned CBP (abbreviation) (actual measurement value), and is a result supporting the validity of the calculation.

On the other hand, it can be seen that the fluorescence wavelength of the dimer of DBq (abbreviation) and TPA (abbreviation) exists on the longer wavelength side than the fluorescence wavelength of one molecule of DBq (abbreviation) or one molecule of TPA (abbreviation). The difference between the fluorescence wavelength and the phosphorescence wavelength of the dimer of DBq (abbreviation) and TPA (abbreviation) is only 0.9 nm, which shows that they are almost the same wavelength.

From this result, it can be said that the excitation complex can consolidate the singlet excitation energy and the triplet excitation energy into almost the same energy. Therefore, as described above, it is suggested that the excited complex can efficiently transfer energy to the phosphorescent compound from both the singlet state and the triplet state.

As described above, the light emitting element according to one aspect of the present invention transfers energy by utilizing the overlap between the light emitting spectrum of the excited complex formed in the light emitting layer and the absorption spectrum of the phosphorescent compound (guest material). , High energy transfer efficiency. Therefore, it is possible to realize a light emitting device having high external quantum efficiency.

Moreover, since the excited complex exists only in the excited state, there is no ground state that can absorb energy. Therefore, energy transfer from the singlet and triplet excited states of the phosphorescent compound (guest material) to the excited complex deactivates the phosphorescent compound (guest material) 109 before it emits light (that is, impairs the emission efficiency). It is considered that this phenomenon does not occur in principle. This is also one of the reasons why the external quantum efficiency can be increased.

The above-mentioned excited complex is formed by the interaction between different molecules in the excited state. Further, it is generally known that the excited complex is easily formed between a material having a relatively deep LUMO level and a material having a shallow HOMO level.

The emission wavelength of the excited complex depends on the energy difference between the HOMO level and the LUMO level. As a general tendency, when the energy difference is large, the emission wavelength becomes short, and when the energy difference is small, the emission wavelength becomes long.

Therefore, the HOMO level and the LUMO level of the first organic compound (host material) 110 and the second organic compound (assist material) 111 in the present embodiment are different from each other. Specifically, the order is HOMO level of the first organic compound 110 &lt;HOMO level of the second organic compound 111 &lt;LUMO level of the first organic compound 110 &lt;LUMO level of the second organic compound 111. The energy levels are different (see Fig. 4).

When an excited complex is formed by these two organic compounds, the LUMO level of the excited complex is derived from the first organic compound (host material) 110, and the HOMO level is the second organic compound (assist). Material) Derived from 111 (see Figure 4). Therefore, the energy difference of the excited complex is smaller than the energy difference of the first organic compound (host material) 110 and the energy difference of the second organic compound (assist material) 111. That is, the emission wavelength of the excitation complex is longer than the emission wavelengths of the first organic compound (host material) 110 and the second organic compound (assist material) 111.

The following two processes can be considered as the process of forming the excited complex in one aspect of the present invention.

The first formation process is a formation process in which the first organic compound (host material) and the second organic compound (assist material) form an excited complex from a carrier-carrying state (cation or anion).

Generally, when electrons and holes (holes) are recombined in the host material, the excitation energy is transferred from the excited state host material to the guest material, and the guest material reaches the excited state and emits light. Before the excitation energy is transferred to the guest material, the host material itself emits light, or the excitation energy becomes heat energy, so that a part of the excitation energy is deactivated. In particular, when the host material is in a singlet excited state, energy transfer is unlikely to occur as described in (2-2). Such deactivation of excitation energy is one of the factors leading to a decrease in the life of the light emitting device.

However, in one aspect of the present invention, since the first organic compound (host material) and the second organic compound (assist material) form an excited complex from a carrier-carrying state (cation or anion), the first step is made. The formation of single-term excitons of the organic compound (host material) of 1 can be suppressed. That is, there may be a process of directly forming an excited complex without forming singlet excitons. Thereby, the deactivation of the singlet excitation energy can also be suppressed. Therefore, it is possible to realize a light emitting element having a long life.

For example, the first organic compound 110 is an electron-trapping compound (with a deep LUMO level) having the property of easily capturing electrons (carriers) among electron-transporting materials, and the second organic compound 111 is Among the hole-transporting materials, when the hole-trapping compound has the property of easily capturing holes (carriers) (shallow HOMO level), the anion of the first organic compound and the second organic compound are used. A direct excitation complex will be formed from the cations of. The excited complex formed in such a process is particularly called an electroplex. By suppressing the generation of the singlet excited state of the first organic compound (host material) and transferring energy from the electroplex to the phosphorescent compound (guest material) in this way, a light emitting element with high luminous efficiency can be obtained. Be done. In this case, the generation of the triplet excited state of the first organic compound (host material) is similarly suppressed, and a directly excited complex is formed. Therefore, when energy is transferred from the excited complex to the phosphorescent compound (guest material), energy is transferred. Conceivable.

In the second formation process, one of the first organic compound (host material) and the second organic compound (assist material) forms singlet excitons and then interacts with the other in the ground state to excite the complex. It is an elementary process that forms. Unlike the electroplex, in this case, a singlet excited state of the first organic compound (host material) or the second organic compound (assist material) is once generated, but this is rapidly converted into an excited complex. Therefore, the deactivation of the singlet excitation energy can also be suppressed. Therefore, it is possible to suppress the deactivation of the excitation energy by the first organic compound (host material) or the second organic compound (assist material). In this case, it is considered that the triplet excited state of the host material is also rapidly converted into the excited complex, and the energy is transferred from the excited complex to the phosphorescent compound (guest material).

The first organic compound (host material) is an electron trapping compound, while the second organic compound (assisting material) is a whole trapping compound, and the difference in HOMO levels of these compounds and the difference in HOMO levels and When the difference in LUMO level is large (specifically, the difference is 0.3 eV or more), the electron selectively enters the first organic compound (host material), and the hole selectively enters the second organic compound (assist material). )to go into. In this case, it is considered that the process of forming the electroplex is prioritized over the process of forming the excited complex via the singlet excitons.

In order to sufficiently overlap the emission spectrum of the excitation complex with the absorption spectrum of the phosphorescent compound (guest material), the energy value of the peak of the emission spectrum and the energy value of the peak of the absorption band on the lowest energy side of the absorption spectrum. The difference from is preferably within 0.3 eV. It is more preferably within 0.2 eV, and most preferably within 0.1 eV.

Further, in the light emitting element according to one aspect of the present invention, it is preferable that the excitation energy of the excitation complex is sufficiently transferred to the phosphorescent compound (guest material), and light emission from the excitation complex is substantially not observed. Therefore, it is preferable that energy is transferred to the phosphorescent compound (guest material) via the excitation complex so that the phosphorescent compound (guest material) emits phosphorescence. The phosphorescent compound (guest material) is preferably an organometallic complex.

Further, in the light emitting element according to one aspect of the present invention, when a phosphorescent compound is used as the first organic compound (host material), the first organic compound (host material) itself easily emits light, and the phosphorescent compound (host material) It becomes difficult for energy to be transferred to the guest material). In this case, it is sufficient that the first organic compound emits light efficiently, but it is difficult to achieve high luminous efficiency because the host material has a problem of concentration quenching. Therefore, at least one of the first organic compound (host material) and the second organic compound (assist material) may be a fluorescent compound (that is, a compound that easily emits light or is thermally deactivated from a singlet excited state). It becomes valid. Therefore, it is preferable that at least one of the first organic compound (host material) and the second organic compound (assist material) is a fluorescent compound.

Therefore, it is preferable that the first organic compound (host material) is a fluorescent compound and the excitation complex is used as a medium for energy transfer.

The configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 2) In the present embodiment, an example of a light emitting device, which is one aspect of the present invention, will be described with reference to FIG.

In the light emitting element shown in the present embodiment, as shown in FIG. 5, an EL layer 203 including a light emitting layer 206 is sandwiched between a pair of electrodes (a first electrode (anode) 201 and a second electrode (cathode) 202). In addition to the light emitting layer 206 having a laminated structure of the first light emitting layer 206a and the second light emitting layer 206b, the EL layer 203 includes a hole (or hole) injection layer 204 and a hole (or). , Hole) Transport layer 205, electron transport layer 207, electron injection layer 208 and the like.

The light emitting layer 206 (first light emitting layer 206a and second light emitting layer 206b) shown in the present embodiment includes a phosphorescent compound 209 as a guest material, a first organic compound 210 as a host material, and a host material. Each contains a second organic compound 211, which is an assist material. In the present embodiment, the first organic compound 210 is contained in the light emitting layer 206 (in any of 206a and 206b) in a larger proportion than the second organic compound 211.

Further, the light emitting layer 206 shown in the present embodiment has a laminated structure of the first light emitting layer 206a and the second light emitting layer 206b, but the second organic compound (assist material) in the first light emitting layer 206a. The proportion of the second light emitting layer 206b containing 211 is characterized by being higher than the proportion of the second organic compound (assist material) 211.

In the light emitting layer 206 (first light emitting layer 206a and second light emitting layer 206b), the phosphorescent compound 209 is dispersed in the first organic compound (host material) 210 and the second organic compound (assist material) 211. The crystallization of the light emitting layer 206 can be suppressed by adopting the configuration. Further, it is possible to suppress the concentration quenching due to the high concentration of the phosphorescent compound 209 and increase the luminous efficiency of the light emitting device.

Further, it is preferable that the triplet excitation energy level (T1 level) of each of the first organic compound 210 and the second organic compound 211 is higher than the T1 level of the phosphorescent compound 209. When the T1 level of the first organic compound 210 (or the second organic compound 211) is lower than the T1 level of the phosphorescent compound (guest material) 209, the phosphorescent compound (guest material) 209 that contributes to light emission This is because the first organic compound 210 (or the second organic compound 211) extinguishes (quenches) the triplet excitation energy, resulting in a decrease in light emission efficiency.

In the light emitting layer 206 in the present embodiment, when the carriers (electrons and holes) injected from both electrodes are recombined, an excited complex (excitplex) is formed from the first organic compound 210 and the second organic compound 211. Is formed. Thereby, the fluorescence spectrum of the first organic compound 210 and the fluorescence spectrum of the second organic compound 211 in the light emitting layer 206 can be converted into the emission spectrum of the excitation complex located on the longer wavelength side. Therefore, in order to maximize the energy transfer from the single-term excited state, the overlap between the emission spectrum of the excitation complex and the absorption spectrum of the phosphorescent compound (guest material) 209 is increased so that the first organic compound 210 and the compound 210 are overlapped with each other. The second organic compound 211 and the second organic compound 211 will be selected respectively. Here, it is considered that energy transfer occurs not from the host material but from the excited complex also in the triplet excited state.

The phosphorescent compound 209 is preferably an organometallic complex. Further, as the first organic compound (host material) 210, it is preferable to use an electron transporting material. Further, as the second organic compound (assist material) 211, it is preferable to use a hole transporting material.

Examples of the organometallic complex include bis [2- (4', 6'-difluorophenyl) pyridinato-N, C.^2’] Iridium (III) Tetrakis (1-Pyrazolyl) Borato (abbreviation: FIR6), Bis [2- (4', 6'-difluorophenyl) Pyridinato-N, C^2’] Iridium (III) picolinate (abbreviation: FIRpic), bis [2- (3', 5'-bistrifluoromethylphenyl) pyridinato-N, C^2’] Iridium (III) picolinate (abbreviation: Ir (CF)₃ppy)₂(pic)), Bis [2- (4', 6'-difluorophenyl) pyridinat-N, C^2’] Iridium (III) Acetylacetonate (abbreviation: FIracac), Tris (2-phenylpyridinato) Iridium (III) (abbreviation: Ir (ppy)₃), Bis (2-phenylpyridinato) Iridium (III) Acetylacetonate (abbreviation: Ir (ppy)₂(acac)), bis (benzo [h] quinolinato) iridium (III) acetylacetonate (abbreviation: Ir (bzq))₂(acac)), bis (2,4-diphenyl-1,3-oxazolato-N, C^2’) Iridium (III) Acetylacetone (abbreviation: Ir (dpo))₂(acac)), Bis {2- [4'-(Perfluorophenyl) Phenyl] Pyridinato-N, C^2’} Iridium (III) Acetylacetonate (abbreviation: Ir (p-PF-ph))₂(acac)), Bis (2-Phenylbenzothiazolato-N, C^2’) Iridium (III) Acetylacetone (abbreviation: Ir (bt))₂(acac)), bis [2- (2'-benzo [4,5-α] thienyl) pyridinat-N, C^3’] Iridium (III) Acetylacetone (abbreviation: Ir (btp))₂(acac)), Bis (1-Phenylisoquinolinato-N, C^2’) Iridium (III) Acetylacetone (abbreviation: Ir (piq))₂(acac)), (Acetylacetoneto) bis [2,3-bis (4-fluorophenyl) quinoxalinato] iridium (III) (abbreviation: Ir (Fdpq))₂(acac)), (Acetylacetonato) Bis (2,3,5-triphenylpyrazinato) Iridium (III) (abbreviation: Ir (tppr))₂(acac)), 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphyrin platinum (II) (abbreviation: PtOEP), tris (acetylacetonato) (monophenanthroline) terbium ( III) (Abbreviation: Tb (acac)₃(Phen)), Tris (1,3-diphenyl-1,3-propanedionat) (monophenanthroline) Europium (III) (abbreviation: Eu (DBM))₃(Phen)), Tris [1- (2-tenoyl) -3,3,3-trifluoroacetonato] (monophenanthroline) Europium (III) (abbreviation: Eu (TTA))₃(Phen)) and so on.

Further, as the electron transporting material, a π-deficient heteroaromatic compound such as a nitrogen-containing heteroaromatic compound is preferable, and for example, 2- [3- (dibenzothiophen-4-yl) phenyl] dibenzo [f, h] Quinoxaline (abbreviation: 2mDBTPDBq-II), 2- [3'-(dibenzothiophen-4-yl) biphenyl-3-yl] dibenzo [f, h] quinoxaline (abbreviation: 2mDBTBPDBq-II), 2- [4 -(3,6-diphenyl-9H-carbazole-9-yl) phenyl] dibenzo [f, h] quinoxaline (abbreviation: 2CzPDBq-III), 7- [3- (dibenzothiophen-4-yl) phenyl] dibenzo [ Quinoxaline or dibenzoquinoxaline such as f, h] quinoxaline (abbreviation: 7mDBTPDBq-II) and 6- [3- (dibenzothiophen-4-yl) phenyl] dibenzo [f, h] quinoxaline (abbreviation: 6mDBTPDBq-II) Derivatives can be mentioned.

Further, as the hole transporting material, a π-excessive heteroaromatic compound (for example, a carbazole derivative or an indole derivative) or an aromatic amine compound is preferable, and for example, 4-phenyl-4'-(9-phenyl). -9H-carbazole-3-yl) triphenylamine (abbreviation: PCBA1BP), 4,4'-di (1-naphthyl) -4''- (9-phenyl-9H-carbazole-3-yl) triphenylamine (Abbreviation: PCBNBB), 3- [N- (1-naphthyl) -N- (9-phenylcarbazole-3-yl) amino] -9-phenylcarbazole (abbreviation: PCzPCN1), 4,4', 4'' -Tris [N- (1-naphthyl) -N-phenylamino] triphenylamine (abbreviation: 1'-TNATA), 2,7-bis [N- (4-diphenylaminophenyl) -N-phenylamino]- Spiro-9,9'-bifluorene (abbreviation: DPA2SF), N, N'-bis (9-phenylcarbazole-3-yl) -N, N'-diphenylbenzene-1,3-diamine (abbreviation: PCA2B), N- (9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl) diphenylamine (abbreviation: DPNF), N, N', N''-triphenyl-N, N', N''- Tris (9-phenylcarbazole-3-yl) benzene-1,3,5-triamine (abbreviation: PCA3B), 2- [N- (9-phenylcarbazole-3-yl) -N-phenylamino] Spiro-9 , 9'-bifluorene (abbreviation: PCASF), 2- [N- (4-diphenylaminophenyl) -N-phenylamino] Spiro-9,9'-bifluolene (abbreviation: DPASF), N, N'-bis [ 4- (Carbazole-9-yl) phenyl] -N, N'-diphenyl-9,9-dimethylfluorene-2,7-diamine (abbreviation: YGA2F), 4,4'-bis [N- (3-methyl) Phenyl) -N-phenylamino] biphenyl (abbreviation: TPD), 4,4'-bis [N- (4-diphenylaminophenyl) -N-phenylamino] biphenyl (abbreviation: abbreviation:)DPAB), N- (9,9-dimethyl-9H-fluoren-2-yl) -N- {9,9-dimethyl-2- [N'-phenyl-N'-(9,9-dimethyl-9H-) Fluoren-2-yl) amino] -9H-fluoren-7-yl} phenylamine (abbreviation: DFLADFL), 3- [N- (9-phenylcarbazole-3-yl) -N-phenylamino] -9-phenyl Carbazole (abbreviation: PCzPCA1), 3- [N- (4-diphenylaminophenyl) -N-phenylamino] -9-Phenylcarbazole (abbreviation: PCzDPA1), 3,6-bis [N- (4-diphenylaminophenyl) )-N-Phenylamino] -9-Phenylcarbazole (abbreviation: PCzDPA2), 4,4'-bis (N- {4- [N'-(3-methylphenyl) -N'-phenylamino] phenyl}- N-Phenylamino) Biphenyl (abbreviation: DNTPD), 3,6-bis [N- (4-diphenylaminophenyl) -N- (1-naphthyl) amino] -9-Phenylcarbazole (abbreviation: PCzTPN2), 3, 6-Bis [N- (9-Phenylcarbazole-3-yl) -N-Phenylamino] -9-Phenylcarbazole (abbreviation: PCzPCA2) can be mentioned.4'-Bis (N- {4- [N'-(3-Methylphenyl) -N'-Phenylamino] Phenyl} -N-Phenylamino) Biphenyl (abbreviation: DNTPD), 3,6-Bis [N- (4-Diphenylaminophenyl) -N- (1-naphthyl) amino] -9-Phenylcarbazole (abbreviation: PCzTPN2), 3,6-bis [N- (9-Phenylcarbazole-3-yl) -N-phenyl Amino] -9-Phenylcarbazole (abbreviation: PCzPCA2) can be mentioned.4'-Bis (N- {4- [N'-(3-Methylphenyl) -N'-Phenylamino] Phenyl} -N-Phenylamino) Biphenyl (abbreviation: DNTPD), 3,6-Bis [N- (4-Diphenylaminophenyl) -N- (1-naphthyl) amino] -9-Phenylcarbazole (abbreviation: PCzTPN2), 3,6-bis [N- (9-Phenylcarbazole-3-yl) -N-phenyl Amino] -9-Phenylcarbazole (abbreviation: PCzPCA2) can be mentioned.

However, the materials that can be used for the phosphorescent compound 209, the first organic compound (host material) 210, and the second organic compound (assist material) 211, respectively, are not limited to these, and are not limited to the excitation complex. The emission spectrum of the excitation complex overlaps with the absorption spectrum of the phosphorescent compound 209, and the peak of the emission spectrum of the excitation complex has a longer wavelength than the peak of the absorption spectrum of the phosphorescent compound 209. Just do it.

Further, when an electron transporting material is used for the first organic compound 210 and a hole transporting material is used for the second organic compound 211, the carrier balance can be controlled by the mixing ratio. Specifically, the range of the first organic compound 210: the second organic compound 211 = 1: 9 to 9: 1 is preferable.

A specific example for manufacturing the light emitting device shown in the present embodiment will be described below.

Metals, alloys, electrically conductive compounds, and mixtures thereof can be used for the first electrode (anode) 201 and the second electrode (cathode) 202. Specifically, indium tin oxide (ITO: Indium Tin Oxide), indium tin oxide containing silicon or silicon oxide, indium zinc oxide (Indium Zinc). Oxide), indium oxide containing tungsten oxide and zinc oxide, gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt In addition to (Co), copper (Cu), palladium (Pd), and titanium (Ti), elements belonging to Group 1 or Group 2 of the Periodic Table of the Elements, that is, alkali metals such as lithium (Li) and cesium (Cs). , And alkaline earth metals such as magnesium (Mg), calcium (Ca), strontium (Sr), and rare earth metals such as alloys containing them (MgAg, AlLi), europium (Eu), itterbium (Yb) and these. Including alloys, other graphenes and the like can be used. The first electrode (anode) 201 and the second electrode (cathode) 202 can be formed by, for example, a sputtering method, a vapor deposition method (including a vacuum vapor deposition method), or the like.

Examples of the highly hole-transporting substance used for the hole injection layer 204 and the hole transport layer 205 include 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (abbreviation: NPB). Or α-NPD) or N, N'-bis (3-methylphenyl) -N, N'-diphenyl- [1,1'-biphenyl] -4,4'-diamine (abbreviation: TPD), 4,4 ', 4''-Tris (carbazole-9-yl) triphenylamine (abbreviation: TCTA), 4,4', 4''-tris (N, N-diphenylamino) triphenylamine (abbreviation: TDATA), 4,4', 4''-Tris [N- (3-methylphenyl) -N-phenylamino] Triphenylamine (abbreviation: MTDATA), 4,4'-Bis [N- (Spiro-9,9') -Aromatic amine compounds such as bifluoren-2-yl) -N-phenylamino] biphenyl (abbreviation: BSPB), 3- [N- (9-phenylcarbazole-3-yl) -N-phenylamino] -9- Phenylcarbazole (abbreviation: PCzPCA1), 3,6-bis [N- (9-phenylcarbazole-3-yl) -N-phenylamino] -9-phenylcarbazole (abbreviation: PCzPCA2), 3- [N- (1) -Naphthyl) -N- (9-phenylcarbazole-3-yl) amino] -9-phenylcarbazole (abbreviation: PCzPCN1) and the like can be mentioned. In addition, 4,4'-di (N-carbazolyl) biphenyl (abbreviation: CBP), 1,3,5-tris [4- (N-carbazolyl) phenyl] benzene (abbreviation: TCPB), 9- [4- ( 10-Phenyl-9-anthrasenyl) phenyl] -9H-carbazole (abbreviation: CzPA) and other carbazole derivatives can be used. The substances mentioned here are mainly 10^-6cm²It is a substance with hole mobility of / Vs or higher. However, any substance other than these may be used as long as it is a substance having a higher hole transport property than electrons.

In addition, poly (N-vinylcarbazole) (abbreviation: PVK), poly (4-vinyltriphenylamine) (abbreviation: PVTPA), poly [N- (4- {N'-[4- (4-diphenylamino)) Phenyl] Phenyl-N'-Phenylamino} Phenyl) Methacrylamide]

Polymer compounds such as (abbreviation: PTPDMA), poly [N, N'-bis (4-butylphenyl) -N, N'-bis (phenyl) benzidine] (abbreviation: Poly-TPD) can also be used.

Examples of the acceptor substance that can be used for the hole injection layer 204 include transition metal oxides and oxides of metals belonging to Groups 4 to 8 in the Periodic Table of the Elements. Specifically, molybdenum oxide is particularly preferable.

The light emitting layer 206 (206a, 206b) is as described above, and is formed by including the phosphorescent compound 209, the first organic compound (host material) 210, and the second organic compound (assist material) 211.

The electron transport layer 207 is a layer containing a substance having a high electron transport property. Alq on the electron transport layer 207₃, Tris (4-methyl-8-quinolinolat) aluminum (abbreviation: Almq)₃), Bis (10-Hydroxybenzo [h] quinolinato) Beryllium (abbreviation: BeBq)₂), BAlq, Zn (BOX)₂, Bis [2- (2-Hydroxyphenyl) benzothiazolato] Zinc (abbreviation: Zn (BTZ))₂) And other metal complexes can be used. In addition, 2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole (abbreviation: PBD), 1,3-bis [5- (p-tert-butyl) Phenyl) -1,3,4-oxadiazole-2-yl] benzene (abbreviation: OXD-7), 3- (4-tert-butylphenyl) -4-phenyl-5- (4-biphenylyl) -1 , 2,4-Triazole (abbreviation: TAZ), 3- (4-tert-butylphenyl) -4- (4-ethylphenyl) -5- (4-biphenylyl) -1,2,4-triazole (abbreviation:: Also complex aromatic compounds such as p-EtTAZ), vasofenantroline (abbreviation: BPhen), vasocuproin (abbreviation: BCP), 4,4'-bis (5-methylbenzoxadiazole-2-yl) stilben (abbreviation: BzOs) Can be used. In addition, poly (2,5-pyridine-diyl) (abbreviation: PPy), poly [(9,9-dihexylfluorene-2,7-diyl) -co- (pyridine-3,5-diyl)] (abbreviation:: PF-Py), like poly [(9,9-dioctylfluorene-2,7-diyl) -co- (2,2'-bipyridine-6,6'-diyl)] (abbreviation: PF-BPy) High polymer compounds can also be used. The substances mentioned here are mainly 10^-6cm²It is a substance with electron mobility of / Vs or higher. A substance other than the above may be used as the electron transport layer 207 as long as it is a substance having a higher electron transport property than holes.

Further, the electron transport layer 207 is not limited to a single layer, but may be a layer in which two or more layers made of the above substances are laminated.

The electron injection layer 208 is a layer containing a substance having a high electron injection property. The electron injection layer 208 contains lithium fluoride (LiF), cesium fluoride (CsF), and calcium fluoride (CaF).₂), Alkali metals such as lithium oxide (LiOx), alkaline earth metals, or compounds thereof can be used. Also, erbium fluoride (ErF)₃) Can be used as a rare earth metal compound. Further, the substance constituting the electron transport layer 207 described above can also be used.

Alternatively, a composite material obtained by mixing an organic compound and an electron donor (donor) may be used for the electron injection layer 208. Such a composite material is excellent in electron injecting property and electron transporting property because electrons are generated in an organic compound by an electron donor. In this case, the organic compound is preferably a material excellent in transporting generated electrons, and specifically, for example, a substance (metal complex, heteroaromatic compound, etc.) constituting the electron transport layer 207 described above is used. Can be used. The electron donor may be any substance that exhibits electron donating property to the organic compound. Specific examples thereof include alkali metals, alkaline earth metals and rare earth metals, and examples thereof include lithium, cesium, magnesium, calcium, erbium and ytterbium. Further, alkali metal oxides and alkaline earth metal oxides are preferable, and lithium oxides, calcium oxides, barium oxides and the like can be mentioned. It is also possible to use a Lewis base such as magnesium oxide. Further, an organic compound such as tetrathiafulvalene (abbreviation: TTF) can also be used.

The hole injection layer 204, the hole transport layer 205, the light emitting layer 206 (206a, 206b), the electron transport layer 207, and the electron injection layer 208 are described by a vapor deposition method (including a vacuum vapor deposition method) and an inkjet method, respectively. , Can be formed by a method such as a coating method.

The light emitted from the light emitting layer 206 of the light emitting element described above is taken out to the outside through either or both of the first electrode 201 and the second electrode 202. Therefore, one or both of the first electrode 201 and the second electrode 202 in the present embodiment is a translucent electrode.

Since the light emitting element shown in the present embodiment can improve the energy transfer efficiency by energy transfer using the overlap between the emission spectrum of the excited complex and the absorption spectrum of the phosphorescent compound, the light emitting element having high external quantum efficiency. Can be realized.

The light emitting device shown in the present embodiment is one aspect of the present invention, and is particularly characterized by the configuration of the light emitting layer. Therefore, by applying the configuration shown in the present embodiment, a passive matrix type light emitting device, an active matrix type light emitting device, and the like can be manufactured, both of which are included in the present invention. ..

In the case of the active matrix type light emitting device, the structure of the TFT is not particularly limited. For example, a staggered type or reverse staggered type TFT can be appropriately used. Further, the drive circuit formed on the TFT substrate may also be composed of N-type and P-type TFTs, or may be composed of only one of N-type TFTs and P-type TFTs. .. Further, the crystallinity of the semiconductor film used for the TFT is not particularly limited. For example, an amorphous semiconductor film, a crystalline semiconductor film, an oxide semiconductor film, or the like can be used.

The configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 3) In the present embodiment, as one aspect of the present invention, a light emitting device having a structure having a plurality of EL layers sandwiching a charge generating layer (hereinafter referred to as a tandem type light emitting device) will be described.

In the light emitting element shown in the present embodiment, as shown in FIG. 6A, a plurality of EL layers (first EL layer 302 (first EL layer 302) are provided between a pair of electrodes (first electrode 301 and second electrode 304). It is a tandem type light emitting device having 1) and a second EL layer 302 (2)).

In the present embodiment, the first electrode 301 is an electrode that functions as an anode, and the second electrode 304 is an electrode that functions as a cathode. The first electrode 301 and the second electrode 304 can use the same configuration as that of the first embodiment. Further, the plurality of EL layers (first EL layer 302 (1), second EL layer 302 (2)) have the same configuration as the EL layer shown in the first embodiment or the second embodiment. However, either of them may have the same configuration. That is, the first EL layer 302 (1) and the second EL layer 302 (2) may have the same configuration or different configurations, and the configurations are the same as those of the first embodiment or the second embodiment. Similar ones can be applied.

Further, a charge generation layer (I) 305 is provided between the plurality of EL layers (first EL layer 302 (1), second EL layer 302 (2)). The charge generation layer (I) 305 has a function of injecting electrons into one EL layer and injecting holes into the other EL layer when a voltage is applied to the first electrode 301 and the second electrode 304. Have. In the case of the present embodiment, when a voltage is applied to the first electrode 301 so that the potential is higher than that of the second electrode 304, the charge generation layer (I) 305 to the first EL layer 302 (1) are applied. Electrons are injected into the second EL layer 302 (2), and holes are injected into the second EL layer 302 (2).

The charge generation layer (I) 305 has translucency with respect to visible light from the viewpoint of light extraction efficiency (specifically, the transmittance of visible light with respect to the charge generation layer (I) 305 is determined. 40% or more) is preferable. Further, the charge generation layer (I) 305 functions even if the conductivity is lower than that of the first electrode 301 and the second electrode 304.

The charge generation layer (I) 305 has a structure in which an electron acceptor is added to an organic compound having a high hole transport property, but an electron donor is added to the organic compound having a high electron transport property. It may be a configured configuration. Further, both of these configurations may be laminated.

In the case where an electron acceptor is added to an organic compound having a high hole transport property, examples of the organic compound having a high hole transport property include NPB, TPD, TDATA, MTDATA, 4,4'-bis [ Aromatic amine compounds such as N- (spiro-9,9'-bifluoren-2-yl) -N-phenylamino] biphenyl (abbreviation: BSPB) can be used. The substances mentioned here are mainly 10^-6cm²It is a substance with hole mobility of / Vs or higher. However, a substance other than the above may be used as long as it is an organic compound having a higher hole transport property than electrons.

Examples of the electron acceptor include 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation: F4-TCNQ), chloranil and the like. Also, transition metal oxides can be mentioned. In addition, oxides of metals belonging to Group 4 to Group 8 in the Periodic Table of the Elements can be mentioned. Specifically, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, and renium oxide are preferable because they have high electron acceptability. Among them, molybdenum oxide is particularly preferable because it is stable in the atmosphere, has low hygroscopicity, and is easy to handle.

On the other hand, in the case where the electron donor is added to the organic compound having high electron transport property, examples of the organic compound having high electron transport property include Alq and Almq.₃, BeBq₂, BAlq and the like, a metal complex having a quinoline skeleton or a benzoquinoline skeleton can be used. In addition, Zn (BOX)₂, Zn (BTZ)₂Oxazole-based, thiazole-based metal complexes having a thiazole-based ligand, and the like can also be used. Further, in addition to the metal complex, PBD, OXD-7, TAZ, BPhen, BCP and the like can also be used. The substances mentioned here are mainly 10^-6cm²It is a substance with electron mobility of / Vs or higher. A substance other than the above may be used as long as it is an organic compound having a higher electron transport property than holes.

Further, as the electron donor, an alkali metal, an alkaline earth metal, a rare earth metal, a metal belonging to Group 13 in the Periodic Table of the Elements, an oxide thereof, or a carbonate can be used. Specifically, it is preferable to use lithium (Li), cesium (Cs), magnesium (Mg), calcium (Ca), ytterbium (Yb), indium (In), lithium oxide, cesium carbonate and the like. Further, an organic compound such as tetrathianaphthalene may be used as an electron donor.

By forming the charge generation layer (I) 305 using the above-mentioned material, it is possible to suppress an increase in the drive voltage when the EL layers are laminated.

In the present embodiment, a light emitting device having two EL layers has been described, but as shown in FIG. 6 (B), the EL layers (302 (1), 302) of n layers (where n is 3 or more) are described. The same can be applied to a light emitting element in which (2) to 302 (n-1) and 302 (n)) are laminated. When a plurality of EL layers are provided between a pair of electrodes as in the light emitting element according to the present embodiment, the charge generation layers (I) (305 (1), 305 (2)) are provided between the EL layers. By arranging ~ 305 (n-2), 305 (n-1)), it is possible to emit light in a high brightness region while keeping the current density low. Since the current density can be kept low, a long-life element can be realized. Further, when lighting is used as an application example, the voltage drop due to the resistance of the electrode material can be reduced, so that uniform light emission over a large area becomes possible. In addition, it is possible to realize a light emitting device that can be driven at a low voltage and has low power consumption.

Further, by making the emission color of each EL layer different, it is possible to obtain emission of a desired color as the entire light emitting element. For example, in a light emitting element having two EL layers, a light emitting element that emits white light as a whole by making the light emitting color of the first EL layer and the light emitting color of the second EL layer have a complementary color relationship. It is also possible to obtain. The complementary color refers to the relationship between colors that become achromatic when mixed. That is, when a color having a complementary color relationship is mixed with light obtained from a substance that emits light, white light emission can be obtained.

The same applies to a light emitting element having three EL layers. For example, the light emitting color of the first EL layer is red, the light emitting color of the second EL layer is green, and the third EL layer. When the emission color of is blue, white emission can be obtained for the entire light emitting element.

The configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 4) In the present embodiment, a light emitting device according to an aspect of the present invention will be described.

The light emitting device shown in the present embodiment has a micro-optical cavity structure that utilizes the resonance effect of light between a pair of electrodes, and has a pair of electrodes (reflection) as shown in FIG. It has a plurality of light emitting elements having a structure having at least an EL layer 405 between the electrode 401 and the semi-transmissive / semi-reflective electrode 402). Further, the EL layer 405 has at least a light emitting layer 404 (404R, 404G, 404B) which is a light emitting region, and in addition, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, and a charge generation layer ( E) etc. may be included.

In the present embodiment, as shown in FIG. 7, a light emitting element having a different structure (first light emitting element (R) 410R, second light emitting element (G) 410G, third light emitting element (B) 410B) is provided. The light emitting device configured by the above will be described.

The first light emitting element (R) 410R has a first transparent conductive layer 403a, a first light emitting layer (B) 404B, a second light emitting layer (G) 404G, and a third light emitting layer on the reflective electrode 401. It has a structure in which an EL layer 405 containing (R) 404R as a part and a semi-transmissive / semi-reflective electrode 402 are sequentially laminated. Further, the second light emitting element (G) 410G has a structure in which the second transparent conductive layer 403b, the EL layer 405, and the transflective / semi-reflective electrode 402 are sequentially laminated on the reflective electrode 401. Further, the third light emitting element (B) 410B has a structure in which the EL layer 405 and the semi-transmissive / semi-reflective electrode 402 are sequentially laminated on the reflective electrode 401.

In the above light emitting element (first light emitting element (R) 410R, second light emitting element (G) 410G, third light emitting element (B) 410B), the reflective electrode 401, the EL layer 405, and the semi-transmissive / semi-transmissive element. The reflective electrode 402 is common. In the first light emitting layer (B) 404B, light (λ) having a peak in the wavelength region of 420 nm or more and 480 nm or less._B) Is emitted, and in the second light emitting layer (G) 404G, light (λ) having a peak in the wavelength region of 500 nm or more and 550 nm or less._G) Is emitted, and in the third light emitting layer (R) 404R, light (λ) having a peak in the wavelength region of 600 nm or more and 760 nm or less is emitted._R) Is emitted. As a result, in any of the light emitting elements (first light emitting element (R) 410R, second light emitting element (G) 410G, third light emitting element (B) 410B), the first light emitting layer (B) 404B, It is possible to emit a broad light in which the light emitted from the second light emitting layer (G) 404G and the third light emitting layer (R) 404R is superimposed, that is, over the visible light region. From the above, the wavelength length is λ._B&lt;λ_G&lt;λ_RIt is assumed that the relationship is.

Each light emitting element shown in the present embodiment has a structure in which an EL layer 405 is sandwiched between a reflective electrode 401 and a semi-transmissive / semi-reflective electrode 402, and each light emitting layer included in the EL layer 405. The light emitted from the light in all directions is resonated by the reflective electrode 401 having a function as a micro-optical resonator (micro-cavity) and the semi-transmissive / semi-reflective electrode 402. The reflective electrode 401 is formed of a conductive material having reflectivity, and the reflectance of visible light to the film is 40% to 100%, preferably 70% to 100%, and the resistivity is 1 ×. Ten^-2It is assumed that the film is Ω cm or less. Further, the semi-transmissive / semi-reflective electrode 402 is formed of a conductive material having reflectivity and a conductive material having light transmissivity, and the reflectance of visible light to the film thereof is 20% to 80%, preferably 40. % ~ 70% and its reflectance is 1 × 10^-²It is assumed that the film is Ω cm or less.

Further, in the present embodiment, in each light emitting element, the transparent conductive layer (first transparent conductive layer 403a, first transparent conductive layer 403a, first) provided on the first light emitting element (R) 410R and the second light emitting element (G) 410G, respectively. By changing the thickness of the transparent conductive layer 403b) of 2, the optical distance between the reflective electrode 401 and the semi-transmissive / semi-reflective electrode 402 is changed for each light emitting element. That is, the broad light emitted from each light emitting layer of each light emitting element enhances the light having a wavelength that resonates between the reflecting electrode 401 and the semitransmissive / semi-reflecting electrode 402, and attenuates the light having a wavelength that does not resonate. Therefore, light of different wavelengths can be extracted by changing the optical distance between the reflective electrode 401 and the semi-transmissive / semi-reflective electrode 402 for each element.

The optical distance (also referred to as the optical path length) is an actual distance multiplied by a refractive index, and in the present embodiment, represents an actual film thickness multiplied by n (refractive index). .. That is, "optical distance = actual film thickness x n".

In the first light emitting element (R) 410R, the total thickness from the reflective electrode 401 to the semi-transmissive / semi-reflective electrode 402 is mλ._R/ 2 (however, m is a natural number), in the second light emitting element (G) 410G, the total thickness from the reflective electrode 401 to the semi-transmissive / semi-reflective electrode 402 is mλ._G/ 2 (however, m is a natural number), in the third light emitting element (B) 410B, the total thickness from the reflective electrode 401 to the semi-transmissive / semi-reflective electrode 402 is mλ._B/ 2 (however, m is a natural number).

From the above, the light (λ) emitted from the first light emitting element (R) 410R mainly by the third light emitting layer (R) 404R contained in the EL layer 405._R) Is taken out, and the light (λ) emitted from the second light emitting element (G) 410G is mainly emitted by the second light emitting layer (G) 404G contained in the EL layer 405._G) Is taken out, and the light (λ) emitted from the first light emitting layer (B) 404B mainly contained in the EL layer 405 from the third light emitting element (B) 410B._B) Is taken out. The light taken out from each light emitting element is emitted from the semitransparent / semi-reflecting electrode 402 side, respectively.

Further, in the above configuration, the total thickness from the reflective electrode 401 to the semi-transmissive / semi-reflective electrode 402 is, strictly speaking, the total thickness from the reflective region of the reflective electrode 401 to the reflective region of the semi-transmissive / semi-reflective electrode 402. can. However, since it is difficult to accurately determine the position of the reflection region on the reflection electrode 401 and the semi-transmissive / semi-reflection electrode 402, it is assumed that any position of the reflection electrode 401 and the semi-transmissive / semi-reflection electrode 402 is the reflection region. By doing so, the above-mentioned effect can be sufficiently obtained.

Next, in the first light emitting element (R) 410R, the optical distance from the reflective electrode 401 to the third light emitting layer (R) 404R is set to the desired film thickness ((2m'+ 1) λ._RBy adjusting to / 4 (where m'is a natural number)), the light emission from the third light emitting layer (R) 404R can be amplified. Of the light emitted from the third light emitting layer (R) 404R, the light reflected and returned by the reflective electrode 401 (first reflected light) is semi-transmitted / semi-reflected from the third light emitting layer (R) 404R. Since it causes interference with the light directly incident on the electrode 402 (first incident light), the optical distance from the reflecting electrode 401 to the third light emitting layer (R) 404R is set to a desired value ((2m'+ 1) λ._RBy adjusting to / 4 (however, m'is a natural number)), the phase of the first reflected light and the first incident light are matched, and the light emitted from the third light emitting layer (R) 404R is amplified. Can be made to.

Strictly speaking, the optical distance between the reflecting electrode 401 and the third light emitting layer (R) 404R is the optical distance between the reflecting region of the reflecting electrode 401 and the light emitting region of the third light emitting layer (R) 404R. Can be done. However, since it is difficult to precisely determine the positions of the reflection region on the reflection electrode 401 and the light emission region on the third light emitting layer (R) 404R, any position of the reflection electrode 401 can be set as the reflection region and the third light emission. It is assumed that the above-mentioned effect can be sufficiently obtained by assuming an arbitrary position of the layer (R) 404R as a light emitting region.

Next, in the second light emitting element (G) 410G, the optical distance from the reflective electrode 401 to the second light emitting layer (G) 404G is set to the desired film thickness ((2m'' + 1) λ._GBy adjusting to / 4 (where m'' is a natural number)), the light emission from the second light emitting layer (G) 404G can be amplified. Of the light emitted from the second light emitting layer (G) 404G, the light reflected and returned by the reflective electrode 401 (second reflected light) is semi-transmitted / semi-reflected from the second light emitting layer (G) 404G. Since it causes interference with the light directly incident on the electrode 402 (second incident light), the optical distance from the reflecting electrode 401 to the second light emitting layer (G) 404G is set to a desired value ((2m'' + 1) λ._GBy adjusting to / 4 (however, m'' is a natural number)), the phase of the second reflected light and the second incident light are matched, and the light emitted from the second light emitting layer (G) 404G is emitted. It can be amplified.

Strictly speaking, the optical distance between the reflecting electrode 401 and the second light emitting layer (G) 404G is the optical distance between the reflecting region of the reflecting electrode 401 and the light emitting region of the second light emitting layer (G) 404G. Can be done. However, since it is difficult to precisely determine the position of the reflection region on the reflection electrode 401 and the light emission region on the second light emitting layer (G) 404G, any position of the reflection electrode 401 can be set as the reflection region and the second light emission. It is assumed that the above-mentioned effect can be sufficiently obtained by assuming an arbitrary position of the layer (G) 404G as a light emitting region.

Next, in the third light emitting element (B) 410B, the optical distance from the reflective electrode 401 to the first light emitting layer (B) 404B is set to the desired film thickness ((2 m'''' + 1) λ._BBy adjusting to / 4 (however, m''' is a natural number), the light emission from the first light emitting layer (B) 404B can be amplified. Of the light emitted from the first light emitting layer (B) 404B, the light reflected by the reflective electrode 401 and returned (third reflected light) is semi-transmitted / semi-reflected from the first light emitting layer (B) 404B. Since it causes interference with the light directly incident on the electrode 402 (third incident light), the optical distance from the reflective electrode 401 to the first light emitting layer (B) 404B is set to a desired value ((2 m'''+ 1). λ_BBy adjusting to / 4 (however, m'''is a natural number)), the phases of the third reflected light and the third incident light are matched, and the light emitted from the first light emitting layer (B) 404B. Can be amplified.

In the third light emitting element, the optical distance between the reflecting electrode 401 and the first light emitting layer (B) 404B is, strictly speaking, the light emitting region in the reflecting electrode 401 and the light emitting in the first light emitting layer (B) 404B. It can be said that it is the optical distance from the area. However, since it is difficult to precisely determine the positions of the reflection region on the reflection electrode 401 and the light emission region on the first light emitting layer (B) 404B, any position of the reflection electrode 401 can be set as the reflection region and the first light emission. It is assumed that the above-mentioned effect can be sufficiently obtained by assuming an arbitrary position of the layer (B) 404B as a light emitting region.

In the above configuration, each light emitting device has a structure having a plurality of light emitting layers in the EL layer, but the present invention is not limited to this, and for example, the tandem type described in the third embodiment is described. In combination with the configuration of the light emitting element, one light emitting element may be provided with a plurality of EL layers with a charge generation layer interposed therebetween, and a single or a plurality of light emitting layers may be formed in each EL layer.

The light emitting device shown in the present embodiment has a microcavity structure, and even if it has the same EL layer, it is possible to extract light having a different wavelength for each light emitting element, so that it is not necessary to separately paint RGB. Will be. Therefore, it is advantageous to realize full color because it is easy to realize high definition. In addition, since it is possible to increase the emission intensity in the front direction of a specific wavelength, it is possible to reduce power consumption. This configuration is particularly useful when applied to a color display (image display device) using pixels of three or more colors, but it may also be used for applications such as lighting.

(Embodiment 5) In the present embodiment, a light emitting device having a light emitting element, which is one aspect of the present invention, will be described.

Further, the light emitting device may be a passive matrix type light emitting device or an active matrix type light emitting device. The light emitting element described in another embodiment can be applied to the light emitting device shown in the present embodiment.

In the present embodiment, the active matrix type light emitting device will be described with reference to FIG.

8 (A) is a top view showing a light emitting device, and FIG. 8 (B) is a cross-sectional view of FIG. 8 (A) cut along the chain line A-A'. The active matrix type light emitting device according to the present embodiment includes a pixel unit 502 provided on the element substrate 501, a drive circuit unit (source line drive circuit) 503, and a drive circuit unit (gate line drive circuit) 504 ( 504a and 504b) and. The pixel unit 502, the drive circuit unit 503, and the drive circuit unit 504 are sealed between the element substrate 501 and the sealing substrate 506 by the sealing material 505.

Further, on the element substrate 501, an external input terminal for transmitting an external signal (for example, a video signal, a clock signal, a start signal, a reset signal, etc.) or a potential to the drive circuit unit 503 and the drive circuit unit 504 is provided. A routing wire 507 for connection is provided. Here, an example of providing an FPC (flexible printed circuit) 508 as an external input terminal is shown. Although only the FPC is shown here, a printed wiring board (PWB) may be attached to the FPC. The light emitting device in the present specification includes not only the light emitting device main body but also a state in which an FPC or a PWB is attached to the light emitting device main body.

Next, the cross-sectional structure will be described with reference to FIG. 8 (B). A drive circuit unit and a pixel unit are formed on the element substrate 501, and here, a drive circuit unit 503, which is a source line drive circuit, and a pixel unit 502 are shown.

The drive circuit unit 503 shows an example in which a CMOS circuit in which an n-channel type TFT 509 and a p-channel type TFT 510 are combined is formed. The circuit forming the drive circuit unit may be formed by various CMOS circuits, MOSFET circuits, or NMOS circuits. Further, in the present embodiment, the driver integrated type in which the drive circuit is formed on the substrate is shown, but it is not always necessary, and the drive circuit can be formed on the outside instead of on the substrate.

Further, the pixel unit 502 has a plurality of pixels including a switching TFT 511 and a first electrode (anode) 513 electrically connected to the wiring (source electrode or drain electrode) of the current control TFT 512 and the current control TFT 512. Is formed by. The insulator 514 is formed so as to cover the end portion of the first electrode (anode) 513. Here, it is formed by using a positive type photosensitive acrylic resin.

Further, in order to improve the covering property of the film laminated and formed on the upper layer, it is preferable to form a curved surface having a curvature on the upper end portion or the lower end portion of the insulating material 514. For example, when a positive photosensitive acrylic resin is used as the material of the insulator 514, it is preferable to have a curved surface having a radius of curvature (0.2 μm to 3 μm) at the upper end of the insulator 514. Further, as the insulator 514, either a negative type photosensitive resin or a positive type photosensitive resin can be used, and not only organic compounds but also inorganic compounds such as silicon oxide and silicon oxynitride can be used. Can be used.

An EL layer 515 and a second electrode (cathode) 516 are laminated and formed on the first electrode (anode) 513. The EL layer 515 is provided with at least a light emitting layer, and the light emitting layer has a laminated structure as shown in the first embodiment. Further, in the EL layer 515, in addition to the light emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, a charge generation layer and the like can be appropriately provided.

The light emitting element 517 is formed by a laminated structure of the first electrode (anode) 513, the EL layer 515, and the second electrode (cathode) 516. As the material used for the first electrode (anode) 513, the EL layer 515 and the second electrode (cathode) 516, the material shown in the first embodiment can be used. Further, although not shown here, the second electrode (cathode) 516 is electrically connected to the FPC 508 which is an external input terminal.

Further, although only one light emitting element 517 is shown in the cross-sectional view shown in FIG. 8B, it is assumed that a plurality of light emitting elements are arranged in a matrix in the pixel unit 502. A light emitting element capable of obtaining three types of light emission (R, G, B) can be selectively formed in the pixel unit 502 to form a light emitting device capable of full-color display. Further, it may be a light emitting device capable of full-color display by combining with a color filter.

Further, by bonding the sealing substrate 506 to the element substrate 501 with the sealing material 505, the light emitting element 517 is provided in the space 518 surrounded by the element substrate 501, the sealing substrate 506, and the sealing material 505. ing. In addition to the case where the space 518 is filled with an inert gas (nitrogen, argon, etc.), it is assumed that the space 518 is filled with the sealing material 505.

It is preferable to use an epoxy resin or low melting point glass for the sealing material 505. Further, it is desirable that these materials are materials that do not allow moisture or oxygen to permeate as much as possible. Further, as the material used for the sealing substrate 506, in addition to the glass substrate and the quartz substrate, a plastic substrate made of FRP (Fiberglass-Reinforced Plastics), PVF (polyvinyl fluoride), polyester, acrylic or the like can be used.

As described above, an active matrix type light emitting device can be obtained.

In addition, the configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 6) In the present embodiment, FIGS. 9 and 10 show examples of various electronic devices completed by using a light emitting device manufactured by applying a light emitting element according to an aspect of the present invention. It will be explained using.

Electronic devices to which a light emitting device is applied include, for example, television devices (also referred to as televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (mobile phones, mobile phones). (Also called a telephone device), a portable game machine, a mobile information terminal, a sound reproduction device, a large game machine such as a pachinko machine, and the like. Specific examples of these electronic devices are shown in FIG.

FIG. 9A shows an example of a television device. In the television device 7100, the display unit 7103 is incorporated in the housing 7101. The display unit 7103 can display an image, and the light emitting device can be used for the display unit 7103. Further, here, a configuration in which the housing 7101 is supported by the stand 7105 is shown.

The operation of the television device 7100 can be performed by the operation switch provided in the housing 7101 or the separate remote control operation machine 7110. The operation key 7109 provided in the remote controller 7110 can be used to operate the channel and volume, and the image displayed on the display unit 7103 can be operated. Further, the remote controller 7110 may be provided with a display unit 7107 for displaying information output from the remote controller 7110.

The television device 7100 is configured to be equipped with a receiver, a modem, and the like. The receiver can receive general television broadcasts, and by connecting to a wired or wireless communication network via a modem, one-way (sender to receiver) or two-way (sender and receiver). It is also possible to perform information communication between (or between receivers, etc.).

FIG. 9B shows a computer, which includes a main body 7201, a housing 7202, a display unit 7203, a keyboard 7204, an external connection port 7205, a pointing device 7206, and the like . The computer is manufactured by using a light emitting device for the display unit 7203.

FIG. 9C shows a portable gaming machine, which is composed of two housings, a housing 7301 and a housing 7302, and is connected by a connecting portion 7303 so as to be openable and closable. The display unit 7304 is incorporated in the housing 7301, and the display unit 7305 is incorporated in the housing 7302. In addition, the portable gaming machine shown in FIG. 9C has a speaker unit 7306, a recording medium insertion unit 7307, an LED lamp 7308, an input means (operation key 7309, a connection terminal 7310, and a sensor 7311 (force, displacement, position). , Speed, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, voice, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, smell or infrared Includes a function to measure), microphone 7312), etc. Of course, the configuration of the portable game machine is not limited to the above, and it is sufficient that a light emitting device is used for at least both the display unit 7304 and the display unit 7305, or a configuration in which other auxiliary equipment is appropriately provided. can do. The portable game machine shown in FIG. 9 (C) has a function of reading a program or data recorded on a recording medium and displaying it on a display unit, and wirelessly communicates with other portable game machines to share information. Has a function. The functions of the portable gaming machine shown in FIG. 9 (C) are not limited to this, and can have various functions.

FIG. 9 (D) shows an example of a mobile phone. The mobile phone 7400 is equipped with an operation button 7403, an external connection port 7404, a speaker 7405, a microphone 7406, and the like, in addition to the display unit 7402 built into the housing 7401. The mobile phone 7400 is manufactured by using a light emitting device for the display unit 7402.

In the mobile phone 7400 shown in FIG. 9 (D), information can be input by touching the display unit 7402 with a finger or the like. In addition, operations such as making a phone call or composing an e-mail can be performed by touching the display unit 7402 with a finger or the like.

The screen of the display unit 7402 mainly has three modes. The first is a display mode mainly for displaying an image, and the second is an input mode mainly for inputting information such as characters. The third is a display + input mode in which two modes, a display mode and an input mode, are mixed.

For example, when making a phone call or composing an e-mail, the display unit 7402 may be set to a character input mode mainly for inputting characters, and the characters displayed on the screen may be input. In this case, it is preferable to display the keyboard or the number button on most of the screen of the display unit 7402.

In addition, by providing a detection device having a sensor that detects the tilt of the gyro, acceleration sensor, etc. inside the mobile phone 7400, the orientation (vertical or horizontal) of the mobile phone 7400 can be determined and the screen display of the display unit 7402 can be determined. Can be switched automatically.

The screen mode can be switched by touching the display unit 7402 or by operating the operation button 7403 of the housing 7401. It is also possible to switch depending on the type of image displayed on the display unit 7402. For example, if the image signal displayed on the display unit is moving image data, the display mode is switched, and if the image signal is text data, the input mode is switched.

Also, in the input mode, the signal detected by the optical sensor of the display unit 7402 is detected, and if there is no input by the touch operation of the display unit 7402 for a certain period, the screen mode is switched from the input mode to the display mode. You may control it.

The display unit 7402 can also function as an image sensor. For example, the person can be authenticated by touching the display unit 7402 with his / her palm or finger and taking an image of a palm print, a fingerprint, or the like. Further, if a backlight that emits near-infrared light or a sensing light source that emits near-infrared light is used for the display unit, the finger vein, palm vein, and the like can be imaged.

FIGS. 10 (A) and 10 (B) are tablet terminals that can be folded in half. FIG. 10A shows the open state, and the tablet terminal has a housing 9630, a display unit 9631a, a display unit 9631b, a display mode changeover switch 9034, a power switch 9035, a power saving mode changeover switch 9036, and a fastener 9033. , Has an operation switch 9038. The tablet terminal is manufactured by using a light emitting device for one or both of the display unit 9631a and the display unit 9631b.

A part of the display unit 9631a can be used as the touch panel area 9632a, and data can be input by touching the displayed operation key 9637. The display unit 9631a shows, for example, a configuration in which half of the area has a display-only function and the other half of the area has a touch panel function, but the configuration is not limited to this. The entire area of the display unit 9631a may have a touch panel function. For example, the entire surface of the display unit 9631a can be displayed as a keyboard button to form a touch panel, and the display unit 9631b can be used as a display screen.

Further, in the display unit 9631b as well, a part of the display unit 9631b can be used as the touch panel area 9632b in the same manner as the display unit 9631a. In addition, the keyboard button can be displayed on the display unit 9631b by touching the position where the keyboard display switching button 9639 on the touch panel is displayed with a finger or a stylus.

It is also possible to simultaneously perform touch input to the touch panel area 9632a and the touch panel area 9632b.

In addition, the display mode changeover switch 9034 can switch the display orientation such as vertical display or horizontal display, and can select switching between black-and-white display and color display. The power saving mode changeover switch 9036 can optimize the brightness of the display according to the amount of external light during use detected by the optical sensor built in the tablet terminal. The tablet-type terminal may incorporate not only an optical sensor but also another detection device such as a sensor for detecting tilt such as a gyro and an acceleration sensor.

Further, FIG. 10A shows an example in which the display areas of the display unit 9631b and the display unit 9631a are the same, but the display area is not particularly limited, and one size and the other size may be different, and the display quality is also good. It may be different. For example, one may be a display panel capable of displaying a higher definition than the other.

FIG. 10B shows a closed state, and the tablet terminal has a housing 9630, a solar cell 9633, a charge / discharge control circuit 9634, a battery 9635, and a DCDC converter 9636. Note that FIG. 10B shows a configuration having a battery 9635 and a DCDC converter 9636 as an example of the charge / discharge control circuit 9634.

Since the tablet terminal can be folded in half, the housing 9630 can be closed when not in use. Therefore, since the display unit 9631a and the display unit 9631b can be protected, it is possible to provide a tablet-type terminal having excellent durability and high reliability from the viewpoint of long-term use.

In addition, the tablet terminals shown in FIGS. 10 (A) and 10 (B) have a function to display various information (still images, moving images, text images, etc.), a calendar, a date, or a time. It can have a function of displaying on a display unit, a touch input function of performing a touch input operation or editing information displayed on the display unit, a function of controlling processing by various software (programs), and the like.

A solar cell 9633 mounted on the surface of a tablet terminal can supply electric power to a touch panel, a display unit, a video signal processing unit, or the like. The solar cell 9633 can be provided on one side or both sides of the housing 9630, and can be configured to efficiently charge the battery 9635. As the battery 9635, if a lithium ion battery is used, there are advantages such as miniaturization.

Further, the configuration and operation of the charge / discharge control circuit 9634 shown in FIG. 10 (B) will be described by showing a block diagram in FIG. 10 (C). FIG. 10C shows the solar battery 9633, the battery 9635, the DCDC converter 9636, the converter 9638, the switches SW1 to SW3, and the display unit 9631, and the battery 9635, the DCDC converter 9636, the converter 9638, and the switches SW1 to SW3 are shown. , Corresponding to the charge / discharge control circuit 9634 shown in FIG. 10 (B).

First, an example of operation when power is generated by the solar cell 9633 by external light will be described. The power generated by the solar cell 9633 is stepped up or down by the DCDC converter 9636 so that it becomes the voltage for charging the battery 9635. Then, when the power from the solar cell 9633 is used for the operation of the display unit 9631, the switch SW1 is turned on, and the converter 9638 steps up or down the voltage required for the display unit 9631. When not displaying on the display unit 9631, the switch SW1 may be turned off and the switch SW2 may be turned on to charge the battery 9635.

The solar cell 9633 is shown as an example of a power generation means, but is not particularly limited, and the battery 9635 is charged by another power generation means such as a piezoelectric element (piezo element) or a thermoelectric conversion element (Peltier element). There may be. For example, a non-contact power transmission module that wirelessly (non-contactly) transmits and receives power for charging may be used, or a configuration may be performed in combination with other charging means.

Further, it goes without saying that the electronic device shown in FIG. 10 is not particularly limited as long as it is provided with the display unit described in the above embodiment.

As described above, an electronic device can be obtained by applying the light emitting device according to one aspect of the present invention. The range of application of the light emitting device is extremely wide, and it can be applied to electronic devices in all fields.

The configuration shown in this embodiment can be used in combination with the configurations shown in other embodiments as appropriate.

(Embodiment 7) In the present embodiment, an example of a lighting device to which a light emitting device including a light emitting element, which is one aspect of the present invention, is applied will be described with reference to FIG.

FIG. 11 shows an example in which the light emitting device is used as an indoor lighting device 8001. Since the light emitting device can have a large area, it is possible to form a lighting device having a large area. In addition, by using a housing having a curved surface, it is possible to form a lighting device 8002 having a curved light emitting region. The light emitting element included in the light emitting device shown in the present embodiment is in the form of a thin film, and has a high degree of freedom in the design of the housing. Therefore, it is possible to form a lighting device with various elaborate designs. Further, a large lighting device 8003 may be provided on the wall surface of the room.

Further, by using the light emitting device on the surface of the table, the lighting device 8004 having a function as a table can be obtained. By using a light emitting device for a part of other furniture, it is possible to obtain a lighting device having a function as furniture.

As described above, various lighting devices to which the light emitting device is applied can be obtained. It should be noted that these lighting devices are included in one aspect of the present invention.

Moreover, the configuration shown in this embodiment can be used in combination with the configuration shown in other embodiments as appropriate.

<p> In this embodiment, the light emitting device 1 which is one aspect of the present invention will be described with reference to FIG. The chemical formulas of the materials used in this example are shown below.</p><p><chemistry num="1"><img file="JP6972276B2_D0004.tif" /></chemistry></p><p>&lt;&lt; Fabrication of light emitting element 1 &gt;&gt; First, indium tin oxide (ITSO) containing silicon oxide was formed on a glass substrate 1100 by a sputtering method to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm × 2 mm.</p><p> Next, as a pretreatment for forming the light emitting element 1 on the substrate 1100, the surface of the substrate was washed with water, fired at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.</p><p> Then 10^-4The substrate was introduced into a vacuum vapor deposition apparatus whose internal pressure was reduced to about Pa, and after vacuum firing at 170 ° C. for 30 minutes in a heating chamber inside the vacuum vapor deposition apparatus, the substrate 1100 was allowed to cool for about 30 minutes.</p><p> Next, the substrate 1100 was fixed to a holder provided in the vacuum vapor deposition apparatus so that the surface on which the first electrode 1101 was formed was facing down. In this embodiment, a case where the hole injection layer 1111, the hole transport layer 1112, the light emitting layer 1113, the electron transport layer 1114, and the electron injection layer 1115 constituting the EL layer 1002 are sequentially formed by the vacuum vapor deposition method will be described. ..</p><p> 10 inside the vacuum device^-4After depressurizing to Pa, 1,3,5-tri (dibenzothiophen-4-yl) -benzene (abbreviation: DBT3P-II) and molybdenum oxide (VI), DBT3P-II (abbreviation): molybdenum oxide = 4 A hole injection layer 1111 was formed on the first electrode 1101 by co-depositing so as to have a ratio of: 2 (mass ratio). The film thickness was 40 nm. Co-deposited is a vapor deposition method in which a plurality of different substances are simultaneously evaporated from different evaporation sources.</p><p> Next, a hole transport layer 1112 was formed by depositing 4-phenyl-4'-(9-phenylfluorene-9-yl) triphenylamine (abbreviation: BPAFLP) at 20 nm.</p><p> Next, a light emitting layer 1113 was formed on the hole transport layer 1112. 2- [3'-(dibenzothiophen-4-yl) biphenyl-3-yl] dibenzo [f, h] quinoxaline (abbreviation: 2mDBTBPDBq-II), 4,4'-di (1-naphthyl) -4'' -(9-Phenyl-9H-carbazole-3-yl) triphenylamine (abbreviation: PCBNBB), (acetylacetonato) bis (6-tert-butyl-4-phenylpyrimidinat) iridium (III) (abbreviation:: [Ir (tBuppm)₂(acac)]), 2mDBTBPDBq-II (abbreviation): PCBNBB (abbreviation): [Ir (tBuppm)₂(acac)]</p><p>(Abbreviation) = 0.7: 0.3: 0.05 (mass ratio) co-deposited to form the first light emitting layer 1113a with a film thickness of 15 nm, then 2mDBTBPDBq-II (abbreviation): PCBNBB (abbreviation): [Ir (tBuppm)₂(acac)] (abbreviation) = 0.8: 0.2: 0.05 (mass ratio) and co-deposited to form the second light emitting layer 1113b with a film thickness of 25 nm to form a light emitting layer 1113 having a laminated structure. bottom.</p><p> Next, after depositing 2mDBTBPDBq-II (abbreviation) at 10 nm on the light emitting layer 1113, bassophenanthroline (abbreviation: Bphen) was deposited at 20 nm to form an electron transport layer 1114. Further, an electron injection layer 1115 was formed by depositing lithium fluoride at 1 nm on the electron transport layer 1114.</p><p> Finally, aluminum was deposited on the electron injection layer 1115 so as to have a film thickness of 200 nm to form a second electrode 1103 to be a cathode, and a light emitting device 1 was obtained. In the above-mentioned vapor deposition process, the resistance heating method was used for all the vapor deposition.</p><p> Table 1 shows the element structure of the light emitting element 1 obtained as described above.</p><p><tables num="1"><img file="JP6972276B2_D0005.tif" /></tables></p><p> In addition, the produced light emitting element 1 was sealed in a glove box having a nitrogen atmosphere so as not to be exposed to the atmosphere (a sealing material was applied around the element and heat-treated at 80 ° C for 1 hour at the time of sealing).</p><p>&lt;&lt; Operating characteristics of the light emitting element 1 &gt;&gt; The operating characteristics of the manufactured light emitting element 1 were measured. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> First, FIG. 13 shows the current density-luminance characteristics of the light emitting element 1. In FIG. 13, the vertical axis is the luminance (cd / m).²), The horizontal axis is the current density (mA / cm)²) Is shown. Further, the voltage-luminance characteristic of the light emitting element 1 is shown in FIG. In FIG. 14, the vertical axis is the luminance (cd / m).²), The horizontal axis shows the voltage (V). Further, FIG. 15 shows the luminance-current efficiency characteristics of the light emitting element 1. In FIG. 15, the vertical axis is the current efficiency (cd / A), and the horizontal axis is the luminance (cd / m).²) Is shown. The voltage-current characteristics of the light emitting element 1 are shown in FIG. In FIG. 16, the vertical axis represents current (mA) and the horizontal axis represents voltage (V).</p><p> From FIG. 14, it was found that the light emitting device 1 which is one aspect of the present invention is a highly efficient device. Also, 1000cd / m²Table 2 below shows the main initial characteristic values of the light emitting element 1 in the vicinity.</p><p><tables num="2"><img file="JP6972276B2_D0006.tif" /></tables></p><p> From the above results, it can be seen that the light emitting device 1 manufactured in this embodiment shows high external quantum efficiency, and therefore shows high light emitting efficiency. Further, regarding the color purity, it can be seen that the yellow-green emission with good purity is exhibited.</p><p> In addition, 25mA / cm for the light emitting element 1.²The emission spectrum when a current is passed at the current density of is shown in FIG. As shown in FIG. 17, the emission spectrum of the light emitting device 1 has a peak near 550 nm, and the phosphorescent organometallic iridium complex [Ir (tBuppm).₂It is suggested that it is derived from the emission of (acac)].</p><p> The results of the reliability test for the light emitting device 1 are shown in FIG. In FIG. 18, the vertical axis shows the normalized luminance (%) when the initial luminance is 100%, and the horizontal axis shows the driving time (h) of the element. Also, for comparison, the light emitting layer is 2mDBTBPDBq-II (abbreviation): PCBNBB (abbreviation): [Ir (tBuppm)₂(acac)] (abbreviation) = 0.8: 0.2: 0.05 (mass ratio) co-deposited to form a film thickness of 40 nm, and the other structures are the same as those of the light emitting element 1 to make a comparative light emitting device. A reliability test was conducted in the same manner. In the reliability test, the initial brightness was 5000 cd / m.²The light emitting element 1 and the comparative light emitting element were driven under the condition that the current density was constant. As a result, the brightness of the comparative light emitting element after 500 hours maintained about 85% of the initial brightness, whereas the brightness of the light emitting element 1 after 500 hours kept about 90% of the initial brightness. ..</p><p> Therefore, it was found that the light emitting element 1 is a highly reliable and long-life light emitting element.</p><p> A mixed film of 2mDBTBPDBq-II (abbreviation), PCBNBB (abbreviation), 2mDBTBPDBq-II (abbreviation) and PCBNBB (abbreviation) was prepared, and the photoluminescence (PL) of each was measured. As a result, the photoluminescence (PL) peak wavelength of the 2mDBTBPDBq-II (abbreviation) vapor deposition film is 428 nm, and the PL peak wavelength of the PCBNBB (abbreviation) vapor deposition film is 428 nm, whereas these are co-deposited and mixed. The PL peak wavelength of the film was 501 nm, which was largely shifted by a long wavelength. Therefore, it was found that 2mDBTBPDBq-II (abbreviation) and PCBNBB (abbreviation) are combinations that form an excited complex.</p>

<p> In this embodiment, the light emitting device 2 which is one aspect of the present invention will be described. For the explanation of the light emitting element 2 in this embodiment, FIG. 12 used for the explanation of the light emitting element 1 in the first embodiment will be used. The chemical formulas of the materials used in this example are shown below.</p><p><chemistry num="2"><img file="JP6972276B2_D0007.tif" /></chemistry></p><p>&lt;&lt; Fabrication of light emitting element 2 &gt;&gt; First, indium tin oxide (ITSO) containing silicon oxide was formed on a glass substrate 1100 by a sputtering method to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm × 2 mm.</p><p> Next, as a pretreatment for forming the light emitting element 2 on the substrate 1100, the surface of the substrate was washed with water, fired at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.</p><p> Then 10^-4The substrate was introduced into a vacuum vapor deposition apparatus whose internal pressure was reduced to about Pa, and after vacuum firing at 170 ° C. for 30 minutes in a heating chamber inside the vacuum vapor deposition apparatus, the substrate 1100 was allowed to cool for about 30 minutes.</p><p> Next, the substrate 1100 was fixed to a holder provided in the vacuum vapor deposition apparatus so that the surface on which the first electrode 1101 was formed was facing down. In this embodiment, a case where the hole injection layer 1111, the hole transport layer 1112, the light emitting layer 1113, the electron transport layer 1114, and the electron injection layer 1115 constituting the EL layer 1002 are sequentially formed by the vacuum vapor deposition method will be described. ..</p><p> 10 inside the vacuum device^-4After depressurizing to Pa, 4-phenyl-4'-(9-phenylfluoren-9-yl) triphenylamine (abbreviation: BPAFLP) and molybdenum oxide (VI) were added to BPAFLP (abbreviation): molybdenum oxide = 1: The hole injection layer 1111 was formed on the first electrode 1101 by co-depositing to 0.5 (mass ratio). The film thickness was 50 nm. Co-deposited is a vapor deposition method in which a plurality of different substances are simultaneously evaporated from different evaporation sources.</p><p> Next, the hole transport layer 1112 was formed by depositing BPAFLP (abbreviation) at 20 nm.</p><p> Next, a light emitting layer 1113 was formed on the hole transport layer 1112. 2- [3- (Dibenzothiophen-4-yl) phenyl] dibenzo [f, h] quinoxaline (abbreviation: 2mDBTPDBq-II), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl) Triphenylamine (abbreviation: PCBA1BP), (acetylacetonato) bis (6-methyl-4-phenylpyrimidinat) iridium (III) (abbreviation: [Ir (mppm))₂(acac)]), 2mDBTPDBq-II (abbreviation): PCBA1BP (abbreviation): [Ir (mppm)₂(acac)] (abbreviation) = 0.7: 0.3: 0.06 (mass ratio), co-deposited to form the first light emitting layer 1113a with a film thickness of 20 nm, then 2mDBTPDBq-II (abbreviation), PCBA1BP (abbreviation) ), Bis (2,3,5-triphenylpyrazinato) (dipivaloylmethanato) Iridium (III) (abbreviation: [Ir (tppr))₂(dpm)]), 2mDBTPDBq-II (abbreviation): PCBA1BP (abbreviation): [Ir (tppr)₂(dpm)] (abbreviation) = 0.8: 0.2: 0.03 (mass ratio) co-deposited to form the second light emitting layer 1113b with a film thickness of 20 nm to form a light emitting layer 1113 having a laminated structure. bottom.</p><p> Next, after depositing 2mDBTPDBq-II (abbreviation) at 15 nm on the light emitting layer 1113, bassophenanthroline (abbreviation: Bphen) was deposited at 15 nm to form an electron transport layer 1114. Further, an electron injection layer 1115 was formed by depositing lithium fluoride at 1 nm on the electron transport layer 1114.</p><p> Finally, aluminum was deposited on the electron injection layer 1115 so as to have a film thickness of 200 nm to form a second electrode 1103 as a cathode, and a light emitting device 2 was obtained. In the above-mentioned vapor deposition process, the resistance heating method was used for all the vapor deposition.</p><p> Table 3 shows the element structure of the light emitting element 2 obtained as described above.</p><p><tables num="3"><img file="JP6972276B2_D0008.tif" /></tables></p><p> In addition, the produced light emitting element 2 was sealed in a glove box having a nitrogen atmosphere so as not to be exposed to the atmosphere (a sealing material was applied around the element and heat-treated at 80 ° C for 1 hour at the time of sealing).</p><p>&lt;&lt; Operating characteristics of the light emitting element 2 &gt;&gt; The operating characteristics of the manufactured light emitting element 2 were measured. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> First, FIG. 19 shows the current density-luminance characteristics of the light emitting element 2. In FIG. 19, the vertical axis is the luminance (cd / m).²), The horizontal axis is the current density (mA / cm)²) Is shown. The voltage-luminance characteristics of the light emitting element 2 are shown in FIG. In FIG. 20, the vertical axis is the luminance (cd / m).²), The horizontal axis shows the voltage (V). Further, FIG. 21 shows the luminance-current efficiency characteristics of the light emitting element 2. In FIG. 21, the vertical axis is the current efficiency (cd / A), and the horizontal axis is the luminance (cd / m).²) Is shown. Further, FIG. 22 shows the voltage-current characteristics of the light emitting element 2. In FIG. 22, the vertical axis represents current (mA) and the horizontal axis represents voltage (V).</p><p> From FIG. 21, it was found that the light emitting device 2 which is one aspect of the present invention is a highly efficient device. Also, 1000cd / m²Table 4 below shows the main initial characteristic values of the light emitting element 2 in the vicinity.</p><p><tables num="4"><img file="JP6972276B2_D0009.tif" /></tables></p><p> From the above results, it can be seen that the light emitting device 2 manufactured in this embodiment shows high external quantum efficiency, and therefore shows high light emitting efficiency.</p><p> In addition, 25mA / cm for the light emitting element 2.²The emission spectrum when a current is passed at the current density of FIG. 23 is shown in FIG. As shown in FIG. 23, the emission spectra of the light emitting device 2 have peaks near 550 nm and 620 nm, respectively, and the phosphorescent organometallic iridium complex [Ir (mppm)).₂(acac)] (abbreviation), [Ir (tppr)₂It is suggested that it is derived from the emission of (dpm)] (abbreviation).</p><p> A mixed film of 2mDBTPDBq-II (abbreviation), PCBA1BP (abbreviation), 2mDBTPDBq-II (abbreviation) and PCBA1BP (abbreviation) was prepared, and the photoluminescence (PL) of each was measured. As a result, the photoluminescence (PL) peak wavelength of the 2mDBTPDBq-II (abbreviation) vapor deposition film is 426 nm, and the PL peak wavelength of the PCBA1BP (abbreviation) vapor deposition film is 416 nm, whereas these are co-deposited and mixed. The PL peak wavelength of the film was 519 nm, which was a large long wavelength shift. Therefore, it was found that 2mDBTPDBq-II (abbreviation) and PCBA1BP (abbreviation) are combinations that form an excited complex.</p>

<p> In this embodiment, the light emitting element 3 shown in FIG. 24 was manufactured, and its operating characteristics and reliability were measured. The light emitting element 3 produced in this embodiment is a light emitting element having a structure having a plurality of EL layers sandwiching a charge generating layer (hereinafter referred to as a tandem type light emitting element) described in the third embodiment. The chemical formulas of the materials used in this example are shown below.</p><p><chemistry num="3"><img file="JP6972276B2_D0010.tif" /></chemistry></p><p><chemistry num="4"><img file="JP6972276B2_D0011.tif" /></chemistry></p><p>&lt;&lt; Fabrication of Light Emitting Element 3 &gt;&gt; First, indium tin oxide (ITSO) containing silicon oxide was formed on a glass substrate 3000 by a sputtering method to form a first electrode 3001 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm × 2 mm.</p><p> Next, as a pretreatment for forming the light emitting element 3 on the substrate 3000, the surface of the substrate was washed with water, fired at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.</p><p> Then 10^-4The substrate was introduced into a vacuum vapor deposition apparatus whose internal pressure was reduced to about Pa, and in a heating chamber inside the vacuum vapor deposition apparatus, vacuum firing was performed at 170 ° C. for 30 minutes, and then the substrate 3000 was allowed to cool for about 30 minutes.</p><p> Next, the substrate 3000 was fixed to a holder provided in the vacuum vapor deposition apparatus so that the surface on which the first electrode 3001 was formed was facing down. In this embodiment, the first hole injection layer 3011a, the first hole transport layer 3012a, the light emitting layer (A) 3013a, and the first electron transport layer constituting the first EL layer 3002a by the vacuum vapor deposition method. After 3014a and the first electron injection layer 3015a are sequentially formed, a charge generation layer 3004 is formed, and then a second hole injection layer 3011b and a second hole transport layer constituting the second EL layer 3002b. A case where the light emitting layer (B) 3013b, the second electron transport layer 3014b, and the second electron injection layer 3015b are formed will be described.</p><p> 10 inside the vacuum device^-4After depressurizing to Pa, 9- [4- (9-phenylcarbazole-3-yl)] phenyl-10-phenylanthracene (abbreviation: PCzPA) and molybdenum oxide (VI), PCzPA (abbreviation): molybdenum oxide = The first hole injection layer 3011a was formed on the first electrode 3001 by co-depositing to a ratio of 1: 0.5 (mass ratio). The film thickness was 90 nm. Co-deposited is a vapor deposition method in which a plurality of different substances are simultaneously evaporated from different evaporation sources.</p><p> Next, the first hole transport layer 3012a was formed by depositing PCzPA (abbreviation) at 30 nm.</p><p> Next, a light emitting layer (A) 3013a was formed on the first hole transport layer 3012a. 9- [4- (10-Phenyl-9-anthrasenyl) phenyl] -9H-carbazole (abbreviation: CzPA), N, N'-bis (3-methylphenyl) -N, N'-bis [3- (9) -Phenyl-9H-Fluorene-9-yl) Phenyl] -Phenyl-1,6-diamine (abbreviation: 1,6mMemFLPAPrn), CzPA (abbreviation): 1,6mMemFLPAPrn (abbreviation) = 1: 0.05 (mass ratio) The light emitting layer (A) 3013a was formed by co-depositing so as to be. The film thickness was 30 nm.</p><p> Next, after 5 nm vapor deposition of CzPA (abbreviation) on the light emitting layer (A) 3013a, further 15 nm vapor deposition of vasophenanthroline (abbreviation: Bphen) formed the first electron transport layer 3014a. Further, on the first electron transport layer 3014a, lithium oxide (Li)₂The first electron injection layer 3015a was formed by depositing O) at 0.1 nm.</p><p> Next, a charge generation layer 3004 was formed by depositing copper phthalocyanine (abbreviation: CuPc) on the first electron injection layer 3015a at a film thickness of 2 nm.</p><p> Next, 4-phenyl-4'-(9-phenylfluoren-9-yl) triphenylamine (abbreviation: BPAFLP) and molybdenum oxide (VI) are placed on the charge generation layer 3004, and BPAFLP (abbreviation): oxidation. A second hole injection layer 3011b was formed by co-depositing molybdenum at 1: 0.5 (mass ratio). The film thickness was 60 nm.</p><p> Next, a second hole transport layer 3012b was formed by depositing BPAFLP (abbreviation) at 20 nm.</p><p> Next, a light emitting layer (B) 3013b was formed on the second hole transport layer 3012b. 2- [3- (Dibenzothiophen-4-yl) phenyl] dibenzo [f, h] quinoxaline (abbreviation: 2mDBTPDBq-II), 4-phenyl-4'-(9-phenyl-9H-carbazole-3-yl) Triphenylamine (abbreviation: PCBA1BP), (acetylacetonato) bis (6-methyl-4-phenylpyrimidinat) iridium (III) (abbreviation: [Ir (mppm))₂(acac)]), 2mDBTPDBq-II (abbreviation): PCBA1BP (abbreviation): [Ir (mppm)₂(acac)] (abbreviation) = 0.6: 0.4: 0.06 (mass ratio) after co-depositing to form the first light emitting layer (first light emitting layer) 3013 (b1) with a film thickness of 10 nm. , 2mDBTPDBq-II (abbreviation), PCBA1BP (abbreviation), (acetylacetonato) bis (4,6-diphenylpyrimidinat) iridium (III) (abbreviation: [Ir (dppm))₂(acac)]), 2mDBTPDBq-II (abbreviation): PCBA1BP (abbreviation): [Ir (dppm)₂(acac)] (abbreviation) = 0.8: 0.2: 0.06 (mass ratio) co-deposited to form the second light emitting layer (second light emitting layer) 3013 (b2) with a film thickness of 30 nm. As a result, a light emitting layer (B) 3013b having a laminated structure was formed.</p><p> Next, a second electron transport layer 3014b was formed by depositing 2mDBTPDBq-II (abbreviation) at 15 nm on the light emitting layer (B) 3013b and then depositing Bphen (abbreviation) at 15 nm. Further, a second electron injection layer 3015b was formed by depositing lithium fluoride (LiF) at 1 nm on the second electron transport layer 3014b.</p><p> Finally, aluminum was deposited on the second electron injection layer 3015b so as to have a film thickness of 200 nm to form a second electrode 3003 as a cathode, and a light emitting device 3 was obtained. In the above-mentioned vapor deposition process, the resistance heating method was used for all the vapor deposition.</p><p> Table 5 shows the element structure of the light emitting element 3 obtained as described above.</p><p><tables num="5"><img file="JP6972276B2_D0012.tif" /></tables></p><p> In addition, the produced light emitting element 3 was sealed in a glove box having a nitrogen atmosphere so as not to be exposed to the atmosphere (a sealing material was applied around the element and heat-treated at 80 ° C for 1 hour at the time of sealing).</p><p>&lt;&lt; Operating characteristics of the light emitting element 3 &gt;&gt; The operating characteristics of the manufactured light emitting element 3 were measured. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> First, FIG. 25 shows the current density-luminance characteristics of the light emitting element 3. In FIG. 25, the vertical axis is the luminance (cd / m).²), The horizontal axis is the current density (mA / cm)²) Is shown. Further, FIG. 26 shows the voltage-luminance characteristics of the light emitting element 3. In FIG. 26, the vertical axis is the luminance (cd / m).²), The horizontal axis shows the voltage (V). Further, FIG. 27 shows the luminance-current efficiency characteristics of the light emitting element 3. In FIG. 27, the vertical axis is the current efficiency (cd / A) and the horizontal axis is the luminance (cd / m).²) Is shown. The voltage-current characteristics of the light emitting element 3 are shown in FIG. 28. In FIG. 28, the vertical axis represents current (mA) and the horizontal axis represents voltage (V).</p><p> From FIG. 27, it was found that the light emitting device 3 which is one aspect of the present invention is a highly efficient device. Also, 1000cd / m²Table 6 below shows the main initial characteristic values of the light emitting element 3 in the vicinity.</p><p><tables num="6"><img file="JP6972276B2_D0013.tif" /></tables></p><p> From the above results, it can be seen that the light emitting device 3 manufactured in this embodiment shows high external quantum efficiency, and therefore shows high light emitting efficiency.</p><p> In addition, 25mA / cm for the light emitting element 3²The emission spectrum when a current is passed at the current density of FIG. 29 is shown in FIG. As shown in FIG. 29, the emission spectra of the light emitting device 3 have peaks at 467 nm and 587 nm, respectively, suggesting that they are derived from the emission of the phosphorescent organometallic iridium complex contained in each light emitting layer.</p><p> As shown in Example 2, 2mDBTPDBq-II (abbreviation) and PCBA1BP (abbreviation) are combinations that form an excited complex.</p>

<p> In this embodiment, the light emitting device 4 which is one aspect of the present invention will be described with reference to FIG. The chemical formulas of the materials used in this example are shown below.</p><p><chemistry num="5"><img file="JP6972276B2_D0014.tif" /></chemistry></p><p>&lt;&lt; Fabrication of light emitting element 4 &gt;&gt; First, indium tin oxide (ITSO) containing silicon oxide was formed on a glass substrate 1100 by a sputtering method to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm × 2 mm.</p><p> Next, as a pretreatment for forming the light emitting element 4 on the substrate 1100, the surface of the substrate was washed with water, fired at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.</p><p> Then 10^-4The substrate was introduced into a vacuum vapor deposition apparatus whose internal pressure was reduced to about Pa, and after vacuum firing at 170 ° C. for 30 minutes in a heating chamber inside the vacuum vapor deposition apparatus, the substrate 1100 was allowed to cool for about 30 minutes.</p><p> Next, the substrate 1100 was fixed to a holder provided in the vacuum vapor deposition apparatus so that the surface on which the first electrode 1101 was formed was facing down. In this embodiment, a case where the hole injection layer 1111, the hole transport layer 1112, the light emitting layer 1113, the electron transport layer 1114, and the electron injection layer 1115 constituting the EL layer 1102 are sequentially formed by the vacuum vapor deposition method will be described. ..</p><p> 10 inside the vacuum device^-4After depressurizing to Pa, 1,3,5-tri (dibenzothiophen-4-yl) -benzene (abbreviation: DBT3P-II) and molybdenum oxide (VI), DBT3P-II (abbreviation): molybdenum oxide = 4 A hole injection layer 1111 was formed on the first electrode 1101 by co-depositing so as to have a ratio of: 2 (mass ratio). The film thickness was 20 nm. Co-deposited is a vapor deposition method in which a plurality of different substances are simultaneously evaporated from different evaporation sources.</p><p> Next, a hole transport layer 1112 was formed by depositing 4-phenyl-4'-(9-phenylfluorene-9-yl) triphenylamine (abbreviation: BPAFLP) at 20 nm.</p><p> Next, a light emitting layer 1113 was formed on the hole transport layer 1112. 2- [3'-(dibenzothiophen-4-yl) biphenyl-3-yl] dibenzo [f, h] quinoxaline (abbreviation: 2mDBTBPDBq-II), 4, 4'-di (1-naphthyl) -4'' -(9-Phenyl-9H-carbazole-3-yl) triphenylamine (abbreviation: PCBNBB), (acetylacetonato) bis (4,6-diphenylpyrimidinat) iridium (III) (abbreviation: [Ir (dppm) )₂(acac)]), 2mDBTBPDBq-II (abbreviation): PCBNBB (abbreviation): [Ir (dppm)₂(acac)] (abbreviation) = 0.7: 0.3: 0.05 (mass ratio), co-deposited to form the first light emitting layer 1113a with a film thickness of 20 nm, and then 2mDBTBPDBq-II (abbreviation): PCBNBB (abbreviation) ): [Ir (dppm)₂(acac)] (abbreviation) = 0.8: 0.2: 0.05 (mass ratio) and co-deposited to form the second light emitting layer 1113b with a film thickness of 20 nm to form a light emitting layer 1113 having a laminated structure. bottom.</p><p> Next, 2mDBTBPDBq-II (abbreviation) was vapor-deposited on the light emitting layer 1113 at 20 nm, and then bassophenanthroline (abbreviation: Bphen) was vapor-deposited at 20 nm to form an electron transport layer 1114. Further, an electron injection layer 1115 was formed by depositing lithium fluoride at 1 nm on the electron transport layer 1114.</p><p> Finally, aluminum was deposited on the electron injection layer 1115 so as to have a film thickness of 200 nm to form a second electrode 1103 as a cathode, and a light emitting device 4 was obtained. In the above-mentioned vapor deposition process, the resistance heating method was used for all the vapor deposition.</p><p> Table 7 shows the element structure of the light emitting element 4 obtained as described above.</p><p><tables num="7"><img file="JP6972276B2_D0015.tif" /></tables></p><p> In addition, the produced light emitting element 4 was sealed in a glove box having a nitrogen atmosphere so as not to be exposed to the atmosphere (a sealing material was applied around the element and heat-treated at 80 ° C for 1 hour at the time of sealing).</p><p>&lt;&lt; Operating characteristics of the light emitting element 4 &gt;&gt; The operating characteristics of the manufactured light emitting element 4 were measured. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> First, FIG. 30 shows the current density-luminance characteristics of the light emitting element 4. In FIG. 30, the vertical axis is the luminance (cd / m).²), The horizontal axis is the current density (mA / cm)²) Is shown. Further, FIG. 31 shows the voltage-luminance characteristics of the light emitting element 4. In FIG. 31, the vertical axis is the luminance (cd / m).²), The horizontal axis shows the voltage (V). Further, FIG. 32 shows the luminance-current efficiency characteristics of the light emitting element 4. In FIG. 32, the vertical axis is the current efficiency (cd / A) and the horizontal axis is the luminance (cd / m).²) Is shown. The voltage-current characteristics of the light emitting element 4 are shown in FIG. 33. In FIG. 33, the vertical axis represents current (mA) and the horizontal axis represents voltage (V).</p><p> From FIG. 32, it was found that the light emitting device 4, which is one aspect of the present invention, is a highly efficient device. Also, 1000cd / m²Table 8 below shows the main initial characteristic values of the light emitting element 4 in the vicinity.</p><p><tables num="8"><img file="JP6972276B2_D0016.tif" /></tables></p><p> From the above results, it can be seen that the light emitting device 4 manufactured in this embodiment shows high external quantum efficiency, and therefore shows high light emitting efficiency. Further, regarding the color purity, it can be seen that the orange emission with good purity is exhibited.</p><p> In addition, 25mA / cm for the light emitting element 4.²The emission spectrum when a current is passed at the current density of is shown in FIG. 34. As shown in FIG. 34, the emission spectrum of the light emitting device 4 has a peak near 586 nm, and the phosphorescent organometallic iridium complex [Ir (dppm).₂(acac)]</p><p>It is suggested that it is derived from the luminescence of.</p><p> The results of the reliability test for the light emitting device 4 are shown in FIG. 35. In FIG. 35, the vertical axis shows the normalized luminance (%) when the initial luminance is 100%, and the horizontal axis shows the driving time (h) of the element. In the reliability test, the initial brightness was 5000 cd / m.²The light emitting element 4 was driven under the condition that the current density was constant. As a result, the brightness of the light emitting element 4 after 1610 hours maintained about 94% of the initial brightness.</p><p> Therefore, it was found that the light emitting element 4 is a highly reliable and long-life light emitting element.</p><p> In addition, as shown in Example 1, 2mDBTBPDBq-II (abbreviation) and PCBNBB (abbreviation) are combinations forming an excited complex.</p>

<p> In this embodiment, the light emitting device 5 which is one aspect of the present invention will be described with reference to FIG. The chemical formulas of the materials used in this example are shown below.</p><p><chemistry num="6"><img file="JP6972276B2_D0017.tif" /></chemistry></p><p>&lt;&lt; Fabrication of Light Emitting Element 5 &gt;&gt; First, indium tin oxide (ITSO) containing silicon oxide was formed on a glass substrate 1100 by a sputtering method to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm × 2 mm.</p><p> Next, as a pretreatment for forming the light emitting element 5 on the substrate 1100, the surface of the substrate was washed with water, fired at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.</p><p> Then 10^-4The substrate was introduced into a vacuum vapor deposition apparatus whose internal pressure was reduced to about Pa, and after vacuum firing at 170 ° C. for 30 minutes in a heating chamber inside the vacuum vapor deposition apparatus, the substrate 1100 was allowed to cool for about 30 minutes.</p><p> Next, the substrate 1100 was fixed to a holder provided in the vacuum vapor deposition apparatus so that the surface on which the first electrode 1101 was formed was facing down. In this embodiment, a case where the hole injection layer 1111, the hole transport layer 1112, the light emitting layer 1113, the electron transport layer 1114, and the electron injection layer 1115 constituting the EL layer 1102 are sequentially formed by the vacuum vapor deposition method will be described. ..</p><p> 10 inside the vacuum device^-4After depressurizing to Pa, 1,3,5-tri (dibenzothiophen-4-yl) -benzene (abbreviation: DBT3P-II) and molybdenum oxide (VI), DBT3P-II (abbreviation): molybdenum oxide = 4 A hole injection layer 1111 was formed on the first electrode 1101 by co-depositing so as to have a ratio of: 2 (mass ratio). The film thickness was 20 nm. Co-deposited is a vapor deposition method in which a plurality of different substances are simultaneously evaporated from different evaporation sources.</p><p> Next, a hole transport layer 1112 was formed by depositing 4-phenyl-4'-(9-phenylfluorene-9-yl) triphenylamine (abbreviation: BPAFLP) at 20 nm.</p><p> Next, a light emitting layer 1113 was formed on the hole transport layer 1112. 2- [3'-(dibenzothiophen-4-yl) biphenyl-3-yl] dibenzo [f, h] quinoxalin (abbreviation: 2mDBTBPDBq-II), N- (1,1'-biphenyl-4-yl)- N- [4- (9-Phenyl-9H-carbazole-3-yl) phenyl] -9,9-dimethyl-9H-fluorene-2-amine (abbreviation: PCBBiF), (acetylacetonato) bis (4,6) -Diphenylpyrimidinat) Iridium (III) (abbreviation: [Ir (dppm))₂(acac)]), 2mDBTBPDBq-II (abbreviation): PCBBiF (abbreviation): [Ir (dppm)₂(acac)] (abbreviation) = 0.7: 0.3: 0.05 (mass ratio), co-deposited to form the first light emitting layer 1113a with a film thickness of 20 nm, and then 2mDBTBPDBq-II (abbreviation): PCB BiF (abbreviation) ): [Ir (dppm)₂(acac)] (abbreviation) = 0.8: 0.2: 0.05 (mass ratio) and co-deposited to form the second light emitting layer 1113b with a film thickness of 20 nm to form a light emitting layer 1113 having a laminated structure. bottom.</p><p> Next, 2mDBTBPDBq-II (abbreviation) was vapor-deposited on the light emitting layer 1113 at 20 nm, and then bassophenanthroline (abbreviation: Bphen) was vapor-deposited at 20 nm to form an electron transport layer 1114. Further, an electron injection layer 1115 was formed by depositing lithium fluoride at 1 nm on the electron transport layer 1114.</p><p> Finally, aluminum was deposited on the electron injection layer 1115 so as to have a film thickness of 200 nm to form a second electrode 1103 as a cathode, and a light emitting device 5 was obtained. In the above-mentioned vapor deposition process, the resistance heating method was used for all the vapor deposition.</p><p> Table 9 shows the element structure of the light emitting element 5 obtained as described above.</p><p><tables num="9"><img file="JP6972276B2_D0018.tif" /></tables></p><p> In addition, the produced light emitting element 5 was sealed in a glove box having a nitrogen atmosphere so as not to be exposed to the atmosphere (a sealing material was applied around the element and heat-treated at 80 ° C for 1 hour at the time of sealing).</p><p>&lt;&lt; Operating characteristics of the light emitting element 5 &gt;&gt; The operating characteristics of the manufactured light emitting element 5 were measured. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> First, FIG. 36 shows the current density-luminance characteristics of the light emitting element 5. In FIG. 36, the vertical axis is the luminance (cd / m).²), The horizontal axis is the current density (mA / cm)²) Is shown. Further, the voltage-luminance characteristic of the light emitting element 5 is shown in FIG. 37. In FIG. 37, the vertical axis is the luminance (cd / m).²), The horizontal axis shows the voltage (V). Further, FIG. 38 shows the luminance-current efficiency characteristics of the light emitting element 5. In FIG. 38, the vertical axis is the current efficiency (cd / A) and the horizontal axis is the luminance (cd / m).²) Is shown. The voltage-current characteristics of the light emitting element 5 are shown in FIG. 39. In FIG. 39, the vertical axis represents current (mA) and the horizontal axis represents voltage (V).</p><p> From FIG. 38, it was found that the light emitting device 5, which is one aspect of the present invention, is a highly efficient device. Also, 1000cd / m²Table 10 below shows the main initial characteristic values of the light emitting element 5 in the vicinity.</p><p><tables num="10"><img file="JP6972276B2_D0019.tif" /></tables></p><p> From the above results, it can be seen that the light emitting device 5 produced in this embodiment shows high external quantum efficiency, and therefore shows high light emitting efficiency. Further, regarding the color purity, it can be seen that the orange emission with good purity is exhibited.</p><p> In addition, 25mA / cm for the light emitting element 5.²The emission spectrum when a current is passed at the current density of is shown in FIG. 40. As shown in FIG. 40, the emission spectrum of the light emitting device 5 has a peak near 583 nm, and the phosphorescent organometallic iridium complex [Ir (dppm).₂(acac)]</p><p>It is suggested that it is derived from the luminescence of.</p><p> The results of the reliability test for the light emitting device 5 are shown in FIG. 41. In FIG. 41, the vertical axis shows the normalized luminance (%) when the initial luminance is 100%, and the horizontal axis shows the driving time (h) of the element. In the reliability test, the initial brightness was 5000 cd / m.²The light emitting element 5 was driven under the condition that the current density was constant. As a result, the brightness of the light emitting element 5 after 1980 hours maintained about 92% of the initial brightness.</p><p> Therefore, it was found that the light emitting element 5 is a highly reliable and long-life light emitting element.</p><p> A mixed film of 2mDBTBPDBq-II (abbreviation), PCBBiF (abbreviation), 2mDBTBPDBq-II (abbreviation) and PCBBiF (abbreviation) was prepared, and the photoluminescence (PL) of each was measured. As a result, the photoluminescence (PL) peak wavelength of the 2mDBTBPDBq-II (abbreviation) vapor deposition film is 428 nm, and the PL peak wavelength of the PCB BiF (abbreviation) vapor deposition film is 415 nm and 436 nm, whereas these are co-deposited. The PL peak wavelength of the mixed film was 512 nm, which was greatly shifted by a long wavelength. Therefore, it was found that 2mDBTBPDBq-II (abbreviation) and PCB BiF (abbreviation) are combinations that form an excited complex.</p>

<p> In this embodiment, the light emitting device 6 which is one aspect of the present invention will be described with reference to FIG. The chemical formulas of the materials used in this example are shown below.</p><p><chemistry num="7"><img file="JP6972276B2_D0020.tif" /></chemistry></p><p>&lt;&lt; Fabrication of light emitting element 6 &gt;&gt; First, indium tin oxide (ITSO) containing silicon oxide was formed on a glass substrate 1100 by a sputtering method to form a first electrode 1101 that functions as an anode. The film thickness was 110 nm, and the electrode area was 2 mm × 2 mm.</p><p> Next, as a pretreatment for forming the light emitting element 6 on the substrate 1100, the surface of the substrate was washed with water, fired at 200 ° C. for 1 hour, and then subjected to UV ozone treatment for 370 seconds.</p><p> Then 10^-4The substrate was introduced into a vacuum vapor deposition apparatus whose internal pressure was reduced to about Pa, and after vacuum firing at 170 ° C. for 30 minutes in a heating chamber inside the vacuum vapor deposition apparatus, the substrate 1100 was allowed to cool for about 30 minutes.</p><p> Next, the substrate 1100 was fixed to a holder provided in the vacuum vapor deposition apparatus so that the surface on which the first electrode 1101 was formed was facing down. In this embodiment, a case where the hole injection layer 1111, the hole transport layer 1112, the light emitting layer 1113, the electron transport layer 1114, and the electron injection layer 1115 constituting the EL layer 1102 are sequentially formed by the vacuum vapor deposition method will be described. ..</p><p> 10 inside the vacuum device^-4After depressurizing to Pa, 1,3,5-tri (dibenzothiophen-4-yl) -benzene (abbreviation: DBT3P-II) and molybdenum oxide (VI), DBT3P-II (abbreviation): molybdenum oxide = 4 A hole injection layer 1111 was formed on the first electrode 1101 by co-depositing so as to have a ratio of: 2 (mass ratio). The film thickness was 20 nm. Co-deposited is a vapor deposition method in which a plurality of different substances are simultaneously evaporated from different evaporation sources.</p><p> Next, a hole transport layer 1112 was formed by depositing 4-phenyl-4'-(9-phenylfluorene-9-yl) triphenylamine (abbreviation: BPAFLP) at 20 nm.</p><p> Next, a light emitting layer 1113 was formed on the hole transport layer 1112. 2- {3- [3- (6-Phenyldibenzothiophen-4-yl) phenyl] phenyl} dibenzo [f, h] quinoxalin (abbreviation: 2mDBTBPDBq-IV), N- (1,1'-biphenyl-4- Il) -N- [4- (9-phenyl-9H-carbazole-3-yl) phenyl] -9,9-dimethyl-9H-fluorene-2-amine (abbreviation: PCBBiF), (acetylacetonato) bis ( 4,6-Diphenylpyrimidinat) Iridium (III) (abbreviation: [Ir (dppm))₂(acac)]), 2mDBTBPDBq-IV (abbreviation): PCBBiF (abbreviation): [Ir (dppm)₂(acac)] (abbreviation) = 0.7: 0.3: 0.05 (mass ratio) co-deposited to form the first light emitting layer 1113a with a film thickness of 20 nm, then 2mDBTBPDBq-IV (abbreviation): PCBBiF (abbreviation) ): [Ir (dppm)₂(acac)] (abbreviation) = 0.8: 0.2: 0.05 (mass ratio) and co-deposited to form the second light emitting layer 1113b with a film thickness of 20 nm to form a light emitting layer 1113 having a laminated structure. bottom.</p><p> Next, 2mDBTBPDBq-IV (abbreviation) was vapor-deposited on the light emitting layer 1113 at 20 nm, and then bassophenanthroline (abbreviation: Bphen) was vapor-deposited at 20 nm to form an electron transport layer 1114. Further, an electron injection layer 1115 was formed by depositing lithium fluoride at 1 nm on the electron transport layer 1114.</p><p> Finally, aluminum was deposited on the electron injection layer 1115 so as to have a film thickness of 200 nm to form a second electrode 1103 as a cathode, and a light emitting device 6 was obtained. In the above-mentioned vapor deposition process, the resistance heating method was used for all the vapor deposition.</p><p> Table 11 shows the element structure of the light emitting element 6 obtained as described above.</p><p><tables num="11"><img file="JP6972276B2_D0021.tif" /></tables></p><p> The produced light emitting element 6 was sealed in a glove box having a nitrogen atmosphere so as not to be exposed to the atmosphere (a sealing material was applied around the element and heat-treated at 80 ° C for 1 hour at the time of sealing).</p><p>&lt;&lt; Operating characteristics of the light emitting element 6 &gt;&gt; The operating characteristics of the manufactured light emitting element 1 were measured. The measurement was performed at room temperature (atmosphere maintained at 25 ° C).</p><p> First, FIG. 42 shows the current density-luminance characteristics of the light emitting element 6. In FIG. 42, the vertical axis is the luminance (cd / m).²), The horizontal axis is the current density (mA / cm)²) Is shown. Further, the voltage-luminance characteristic of the light emitting element 6 is shown in FIG. 43. In FIG. 43, the vertical axis is the luminance (cd / m).²), The horizontal axis shows the voltage (V). Further, FIG. 44 shows the luminance-current efficiency characteristics of the light emitting element 6. In FIG. 44, the vertical axis is the current efficiency (cd / A) and the horizontal axis is the luminance (cd / m).²) Is shown. The voltage-current characteristics of the light emitting element 6 are shown in FIG. 45. In FIG. 45, the vertical axis represents current (mA) and the horizontal axis represents voltage (V).</p><p> From FIG. 44, it was found that the light emitting device 6 which is one aspect of the present invention is a highly efficient device. Also, 1000cd / m²Table 12 below shows the main initial characteristic values of the light emitting element 6 in the vicinity.</p><p><tables num="12"><img file="JP6972276B2_D0022.tif" /></tables></p><p> From the above results, it can be seen that the light emitting device 6 manufactured in this embodiment shows high external quantum efficiency, and therefore shows high light emitting efficiency. Further, regarding the color purity, it can be seen that the orange emission with good purity is exhibited.</p><p> In addition, 25mA / cm for the light emitting element 6²The emission spectrum when a current is passed at the current density of FIG. 46 is shown in FIG. As shown in FIG. 46, the emission spectrum of the light emitting device 6 has a peak near 587 nm, and the phosphorescent organometallic iridium complex [Ir (dppm).₂(acac)]</p><p>It is suggested that it is derived from the luminescence of.</p><p> The results of the reliability test for the light emitting element 6 are shown in FIG. 47. In FIG. 47, the vertical axis shows the normalized luminance (%) when the initial luminance is 100%, and the horizontal axis shows the driving time (h) of the element. In the reliability test, the initial brightness was 5000 cd / m.²The light emitting element 6 was driven under the condition that the current density was constant. As a result, the brightness of the light emitting element 6 after 833 hours maintained about 91% of the initial brightness.</p><p> Therefore, it was found that the light emitting element 6 is a highly reliable and long-life light emitting element.</p>

101 Electrode 102 Electrode 103 EL layer 104 Hole injection layer 105 Hole transport layer 106 Light emitting layer 106a First light emitting layer 106b Second light emitting layer 107 Electron transport layer 108 Electron injection layer 109 Phosphoric compound 110 First organic compound 111 Second organic compound 201 First electrode (anodode) 202 Second electrode (cathode) 203 EL layer 204 Hole injection layer 205 Hole transport layer 206 Light emitting layer 206a First light emitting layer 206b Second light emitting layer 207 Electron transport layer 208 Electron injection layer 301 First electrode 302 (1) First EL layer 302 (2) Second EL layer 304 Second electrode 305 Charge generation layer (I) 305 (1) First charge Generation layer (I) 305 (2) Second charge generation layer (I) 401 Reflective electrode 402 Semi-transmissive / semi-reflection electrode 403a First transparent conductive layer 403b Second transparent conductive layer 404B First light emitting layer (B) ) 404G Second light emitting layer (G) 404R Third light emitting layer (R) 405 EL layer 410R First light emitting element (R) 410G Second light emitting element (G) 410B Third light emitting element (B) 501 Element board 502 Pixel part 503 Drive circuit part (source) Wire drive circuit) 504a, 504b Drive circuit section (gate wire drive circuit) 505 Sealing material 506 Sealing board 507 Routing wiring 508 FPC (Flexible print circuit) 509 n Channel type TFT510 p Channel type TFT511 Switching TFT512 Current control TFT513 1 Electrode (anodole) 514 Insulation 515 EL layer 516 Second electrode (cathode) 517 Light emitting element 518 Space 1100 Substrate 1101 First electrode 1102 EL layer 1103 Second electrode 1111 Hole injection layer 1112 Hole transport layer 1113 Light emitting layer 1114 Electron transport layer 1115 Electron injection layer 3000 Substrate 3001 First electrode 3002a First EL layer, 3002b 2nd EL layer, 3011a 1st hole injection layer, 3011b 2nd hole injection layer 3012a 1st hole transport layer, 3012b 2nd hole transport layer 3013a light emitting layer (A), 3013b light emitting layer (B) 3014a first electron transport layer, 3014b second electron transport layer 3015a first electron injection layer, 3015b second electron injection layer 3003 second electrode 3004 charge generation layer 7100 television device 7101 housing 7103 Display 7105 Stand 7107 Display 7109 Operation key 7110 Remote control operation device 7201 Main unit 7202 Housing 7203 Display 7204 Keyboard 7205 External connection port 7206 Pointing device 7301 Housing 7302 Housing 7303 Connection 7304 Display 7305 Display 7306 Speaker 7307 Recording medium insertion part 7308 LED lamp 7309 Operation key 7310 Connection terminal 7311 Sensor 7312 Microphone 7400 Mobile phone 7401 Housing 7402 Display 7403 Operation button 7404 External connection port 7405 Speaker 7406 Microphone 8001 Lighting device 8002 Lighting device 8003 Lighting device 8004 Lighting device 9033 Fastener 9034 Display mode changeover switch 9035 Power switch 9036 Power saving mode changeover switch 9038 Operation Switch 9630 Housing 9631 Display 9631a Display 9631b Display 9632a Touch panel area 9632b Touch panel area 9633 Solar cell 9634 Charge / discharge control circuit 9635 Battery 9636 DCDC converter 9637 Operation key 9638 Converter 9639 button