Electroluminescent devices with low work function anode

The present invention relates to display technology. In particular, the present invention relates to an organic electroluminescent device.

Organic luminescence or organic electroluminescence is, for example, the conversion of an electric current into visible light by an internal process of an organic compound. The fluorescence or phosphorescence of an organic compound emits light when an electric current is applied. Both organic fluorescent and phosphorescent molecules are called organic luminescent compounds.

<p num="0003"> Organic or electroluminescent devices are generally composed of two counter electrodes and one or more layers inserted between the electrodes. One or more layers between the two electrodes contain one or more organic luminescent compounds. The electrons and holes are collectively called a carrier, and are injected into the above-mentioned layer from both electrodes, and both electrodes are a cathode and an anode. Upon application of appropriate power, the cathode injects electrons into the insertion layer and the anode injects holes into this layer.</p><p num="0004"> The performance of an organic electroluminescent device depends on the amount of carriers injected from the electrode among many factors. The more carriers injected, the more likely it is to have higher luminescence or brightness. In order to inject a large amount of carriers from the electrodes at a low drive voltage, select an electrode material from which the carriers are easily injected. The anode is generally made of a material with a high work function. The cathode is generally made of a substance with a low work function. In a single electroluminescent device, the work function of the anode material is higher than the work function of the cathode material.</p><p num="0005"> In addition, a carrier injection layer can be introduced in order to inject a large amount of carriers from the electrode at a low drive voltage. The carrier injection layer promotes carrier injection from the electrode. The hole injection layer can be formed on one surface of the anode facing the cathode. The electron injection layer can be formed on one surface of the cathode facing the anode. The material for the carrier injection layer is also selected so that the carrier injection layer easily receives carriers from the electrodes. The hole injection layer is generally formed of a substance having a low oxidation potential, which is easily oxidized at a low potential. The electron injection layer is generally formed of a substance having a low reduction potential, which is easily reduced at a low potential.</p>

<p num="0006"> According to embodiments of the present invention, the components of the electroluminescent device include: a cathode; an anode facing the cathode and substantially containing a reflective material; and a functional layer with the anode. Those arranged between the cathodes and containing the compounds of the general formula I defined above are included. The reflectance of the substantially reflective material is from about 0.4 to 1. The substantial reflective material is selected from aluminum, silver, gold, nickel, chromium, molybdenum, tantalum, titanium and zinc which make up the choice. The substantially reflective material reflects substantially all wavelength components of visible light. [General formula I]<chemistry num="1"><img id="000002" he="56" wi="59" file="JP5259128B2_D0001.tif" img-format="tif" img-content="drawing" /></chemistry></p><p num="0007"> According to another embodiment, the electroluminescent device is: The substantially reflective material is a conductive material having a work function of 4.5 eV or less; the cathode is substantially composed of the conductive material; the functional layer is at least one located between the anode and the cathode. A light emitting layer; and a buffer layer that is in contact with one of the anode or cathode on one surface thereof and is oriented toward the at least one light emitting layer, the anode injecting holes toward the at least one light emitting layer. Arranged to inject, the cathode is arranged to inject electrons towards the at least one light emitting layer; the buffer layer is composed of at least one substantially non-conductive substance. To. The buffer layer comes into contact with the anode. The anode contains aluminum and the buffer layer contains aluminum oxide. The device includes a hole injection layer located between the buffer layer and the at least one light emitting layer, and the hole injection layer contains a compound of the general formula I defined above. The device comes into contact with the cathode and additionally comprises another buffer layer located between the cathode and the at least one light emitting layer. The buffer layer has a substantially thin thickness sufficient to allow holes to pass through. The buffer layer has a thickness of about 5 Å to about 40 Å. The buffer layer has a thickness of about 10 Å to about 20 Å.</p><p num="0008"> In the device, the at least one substantially non-conductive substance is aluminum oxide, titanium oxide, zinc oxide, ruthenium oxide, nickel oxide, zirconium oxide, tantalum oxide, magnesium oxide. , Calcium oxide, strontium oxide, vanadium oxide, iturium oxide, lithium oxide, cesium oxide, chromium oxide, silicon oxide, barium oxide, manganese oxide, cobalt oxide, copper oxide, placeodium Oxides, Tungsten Oxides, Germanium Oxides, Potassium Oxides, Lithium Fluoride, Magnesium Fluoride, Cesium Fluoride, Calcium Fluoride, Sodium Chloride, Potassium Chloride, Lithium Metaborate (BiBO)₂), Potassium silicate (K₂SiO₃), Silicon-germanium oxide, barium titanate, lithium tantalate (LiTaO)₃), Silicon Nitride (Si)₃N₄), Borone nitride (BN), Nitride of elements belonging to groups 3 and 4 of the Periodic Table of the Elements, Zinc sulfide (ZnS), Cadmium sulfide (CdS), Cadmium selenide (CdSe), Gallium phosphate (GaP) , And gallium nitride (GaN).</p><p num="0009"> According to another embodiment, the electroluminescent element: the functional layer is located between the anode; the cathode; the anode and the cathode; the anode contact layer in contact with the anode; the anode and the cathode; A cathode contact layer located between the two and in contact with the cathode; and means for forming a virtual electrode within at least one layer of the anode contact layer and the cathode contact layer.</p><p num="0010"> Another aspect of the invention provides a variety of electronic displays. The display includes electroluminescent devices according to the various embodiments. The display additionally includes an electronic circuit connected to the electroluminescent element.</p><p num="0011"> Another aspect of the invention provides a method of operating an electronic element that includes the following steps: an anode, a cathode, and a functional layer between the anode and the cathode, wherein the functional layer is functional with the anode. A step of providing an intervening layer located between the layers or an electronic element having an interface with the anode; a step of applying a forward electric field between the anode and the cathode; where electrons are transferred from the anode to the function. It is injected into the sex layer and substantially stays in the region near the interface to form a virtual cathode.</p><p num="0012"> In the above method, the continuous application of the forward electric field promotes hole injection from the anode into the functional layer. By continuously applying the forward electric field, hole transfer is promoted in the direction of the cathode in the functional layer. The functional layer contains substances having (low) reduction potential, (low) electron mobility, and (high) hole mobility. The functional layer comprises a compound of the general formula I. The functional layer comprises a compound of the general formula Ia. The functional layer contains at least one compound having a reduction potential range of about -0.4 to about 0 V. The functional layer contains at least one compound having a reduction potential of about -0.3 to about 0 V. The anode comprises at least one substance having a work function in the range of about 3.5 to about 4.5 eV. The functional layer has an electron mobility of about 10 in it.^-5Contains at least one compound lower than cm / Vs. The functional layer has an electron mobility of about 10 in it.^-10~ About 10^-6Contains at least one compound that is cm / Vs. The functional layer contains at least one compound in which the hole mobility is higher than about 10-4 cm / Vs. The functional layer has a hole mobility of about 10 in it.^-4Includes at least one compound ranging from to about 1 cm / Vs.</p>

Various aspects of the invention will be described in more detail below. It should be understood from the art herein that one of ordinary skill in the art can modify the inventions articulated herein to obtain the advantageous effects of the present invention. Therefore, the following techniques are broad and teach those skilled in the art of appropriate art, and do not limit the invention. The titles used in the following techniques are intended to refer to what is generally discussed and do not define or limit the content of the discussion.

<u style="single">Configuration of organic EL element</u> The organic EL device according to various embodiments of the present invention can be configured by various methods. A typical configuration of an organic EL device includes two opposing electrodes and one or more functional layers inserted between the two electrodes. The term "layer" means a deposit, coat or film of one substance or a mixture of two or more substances. FIGS. 1 to 6 show an exemplary cross-sectional configuration of an organic EL device capable of realizing various aspects of the present invention. In the drawings, the same drawing code is used to refer to a layer or component. It should be noted that these configurations are not leftover deformations of the organic EL device according to the present invention.

The illustrated organic EL element 10 has a substrate 1, an anode 3, a cathode 15, and one or more functional layers arranged between the anode 3 and the cathode 15. The one or more intervening functional layers include a hole injection layer 5, a hole transfer layer 7, a light emitting layer 9, an electron transfer layer 11, and an electron injection layer 13, and are multifunctional having the functions of the two or more layers. Includes sex layer. Even in the inadequate list of multifunctional layers, a layer having a hole injection and hole transfer function, a layer having a hole injection and light emitting function, a layer having a hole injection and hole transfer and light emitting function, and an electron. It includes a layer having an injection and electron transfer function, a layer having an electron transfer and a light emitting function, a layer having an electron injection, an electron transfer and a light emitting function, and the like.

The substrate 1 (FIGS. 1 to 6) supports a laminated structure of organic EL elements 10. Although the drawing shows that the substrate 1 is arranged on the side of the anode 3, the substrate 1 may be arranged on the side of the cathode 15. In either case, the substrate 1 provides a support capable of forming a laminated structure of organic EL elements. Anode 3 (FIGS. 1-6) and cathode 15 (FIGS. 1-6) are electrically connected to power supply 17 (FIGS. 1-6) via switch 19 (FIG. 6), and the switch is connected by a controller (not shown). Be controlled. Although not shown, one or both of electrodes 3 and 15 can be formed with multiple layers, the so-called "buffer layer". It may or may not contain a non-conductive layer called. The hole injection layer 5 (FIGS. 1 to 3) promotes hole injection from the anode 3 into the hole transfer layer 7 (FIGS. 1 to 5). Similarly, the electron injection layer 13 (FIGS. 1 and 4) facilitates electron injection from the cathode 15 into the electron transfer layer 13. The hole transfer layer 7 accelerates the movement of holes from the anode 3 and / or the hole injection layer 5 toward the light emitting layer 9 (FIGS. 1 to 6). The electron transfer layer 11 (FIGS. 1, 2, 4 and 5) accelerates the movement of electrons from the cathode 15 and / or the electron injection layer 13 to the light emitting layer 9 (FIGS. 1-6). For functional layers and other features of organic EL devices, filed March 14, 2002, US Patent Application No. 10 / 099,781, US Patent Application Gazette No. ___, and May 6, 2003, See U.S. Patent Application Gazette No. ___ of U.S. Patent Application No. 10 / 431,349, which is incorporated herein by reference in its entirety.

When an appropriate voltage is applied between the electrodes 3 and 15, electrons and holes are injected into the intervening layer from the cathode 15 and the anode 3, respectively. The holes and electrons move to luminescent molecules in the intervening layer and recombine. The pair of recombined electrons and holes, the excitons, transfers the rebinding energy to the luminescent molecule where they are recombined. Alternatively, excitons travel for a short time to transfer recombination energy to other luminescent molecules, especially luminescent molecules with smaller interstitial spaces than the luminescent molecules they recombinated. The transferred energy is used to excite the valence electrons of the luminescent molecule, which produces photons when the electrons return to the bottom state.

<u style="single">Organic EL device using the compound of general formula I</u> One aspect of the present invention provides an organic EL device containing at least one compound represented by the general formula I in one or more functional layers located between two opposing electrodes 3 and 15.<chemistry num="2"><img id="000003" he="56" wi="59" file="JP5259128B2_D0001.tif" img-format="tif" img-content="drawing" /></chemistry> In the above formula R1-R6 independently hydrogen, halo, nitrile (-CN), nitro (-NO)₂), Sulfonyl (-SO₂R), sulfoxide (-SOR), sulfonamide (-SO)₂NR), sulfonate (-SO)₃R), trifluoromethyl (-CF)₃), Ester (-CO-OR), Amide (-CO-NHR or -CO-NRR'), Linear or branched (substituted or unsubstituted) C₁-C₁₂Alkoxy, linear or branched (substituted or unsubstituted) C₁-C₁₂Alkyl, aromatic or non-aromatic (substituted or unsubstituted) heterocycles, substituted or unsubstituted aryl, mono- or di- (substituted or unsubstituted) aryl-amines, and (substituted or unsubstituted) alkyl- (substituted or unsubstituted) Or unsubstituted) Selected from the group composed of aryl-amines. In the substituents, R and R'are, for example, substituted or unsubstituted C.₁-C₆₀Alkyl, substituted or unsubstituted aryl, substituted or unsubstituted 5-7-membered heterocycles. The replaced C₁-C₆₀Alkyl, aryl and heterocycles are optionally substituted with one or more amine, amide, ether and ester groups. Alternatively, R1-R6 is independently selected from substituted or unsubstituted electron-withdrawing substituents, which will be well understood by those skilled in the art. The aryl group comprises phenyl, bipenyl, terphenyl, benzyl, naphthyl, anthracenyl, tetrasenyl, pentasenyl, perylenel and coronenyl, which are single or multiple substituted or not substituted.

Non-restrictive examples of general formula I compounds are the following general formulas Ia to If.<chemistry num="3"><img id="000004" he="64" wi="64" file="JP5259128B2_D0001.tif" img-format="tif" img-content="drawing" /></chemistry><chemistry num="4"><img id="000005" he="65" wi="72" file="JP5259128B2_D0001.tif" img-format="tif" img-content="drawing" /></chemistry><chemistry num="5"><img id="000006" he="57" wi="72" file="JP5259128B2_D0001.tif" img-format="tif" img-content="drawing" /></chemistry><chemistry num="6"><img id="000007" he="68" wi="78" file="JP5259128B2_D0001.tif" img-format="tif" img-content="drawing" /></chemistry><chemistry num="7"><img id="000008" he="62" wi="78" file="JP5259128B2_D0001.tif" img-format="tif" img-content="drawing" /></chemistry><chemistry num="8"><img id="000009" he="61" wi="68" file="JP5259128B2_D0001.tif" img-format="tif" img-content="drawing" /></chemistry>

Other examples of General Formula I, the synthesis and various characteristics of such compounds, are additionally disclosed in U.S. Patent Application No. US2002 / 0158242A1 and U.S. Patent Applications Nos. 6436559 and 4780536. All are integrated into this application as a whole for reference.

In one embodiment of the invention, the organic EL device 10 comprises at least one compound of the general formula Ia-If. Optionally, at least one compound of the general formula Ia-If is included in one layer of the layer alone or in combination with one or more of the compounds of the general formula I or other compounds. Optionally, the compound of the general formula Ia may be combined with one or more other compounds represented by the general formula I or not, or alone contained in at least one of the layers of the organic EL device 10. Is done.

In general, the compound of general formula I can be used in one of the functional or multifunctional layers of the organic EL device 10. Optionally, the compound is of the general formula Ia-If. Optionally, one or more compounds represented by the general formula I are contained within one of the layers in contact with the anode 3. In one embodiment, the organic EL device includes a hole injection layer 5 as shown in FIGS. 1 to 3, and at least one compound represented by the general formula I is contained in the hole injection layer 5. Optionally, the hole injection layer is formed of at least one compound represented by the general formula I, which is substantially free of other substances. Instead, the hole injection layer is combined with one or more other substances and formed of at least one compound represented by the general formula I.

In another embodiment, the organic EL device includes a hole transfer layer 7 as shown in FIGS. 1 to 5, and at least one compound represented by the general formula I is contained in the hole transfer layer 7. Optionally, the compound is of the general formula Ia-If. Optionally, the hole transfer layer is substantially free of other substances or is combined with one or more other substances to form at least one compound of general formula I. In another embodiment, the organic EL device comprises a layer that functions to include hole injection and hole transfer, such a multifunctional layer comprising at least one compound represented by the general formula I. The multifunctional layer is substantially free of other substances or combined with one or more other substances and is formed of at least one compound of the general formula I.

<u style="single">Virtual electrode</u> Another aspect of the present invention relates to the formation of virtual electrodes in the operation of electronic devices, including organic EL devices. The term "virtual electrode" means the accumulation of charged carriers in the internal region of an electronic element that looks like an electrode, based on the concept of a real electrode. The virtual electrode actually enhances or facilitates carrier injection from the electrode.

The formation of virtual electrodes will be discussed with reference to the exemplary structure of the organic EL device 16 in FIG. Although such discussions relate to EL devices, virtual electrodes are not an inherent phenomenon in organic EL devices and can occur in any other electronic device. The organic EL element 16 includes an anode 3 and a cathode 15 located so as to face each other. Each of the electrodes 3 and 15 is connected to the power source 17 via the control switch 19. The first layer 21 and the second layer 23 are inserted between the opposing electrodes 3 and 15. At least one of the first layer 21 and the second layer 23 contains a luminescent substance.

It is not necessary to be bound by any theory as to why the present invention works, and in one embodiment, the first layer 21 is formed of a substance that is more stable in its neutral state and in a more reducing state. Here, if a substance spontaneously converts from its neutral state to the reduced state, the substance is more stable in the reduced state in the neutral state. Further, for example, it is assumed that electrons have a very low mobility in the first layer 21 material, while holes have a very high mobility in it. When the anode 3 and the first layer 21 come into contact with each other, the free electrons of the anode 3 are transferred to the first layer 21 for the reduction of the substance of the first layer 21. Due to the low electron mobility in the material, the transferred electrons hardly move in the first layer 21 after crossing the boundary 27 between the anode 3 and the first layer 21. Instead, the transmitted electrons stay near the boundary 27 on the side of layer 21. Therefore, the electrons transferred from the anode 3 to the first layer 21 are accumulated along the boundary 27 as illustrated by reference numeral 25.

According to the concept of the anode 3, the electrons or negative charges 25 accumulated along the boundary 27 are such that the source of the electrons, that is, the cathode of the element, is located very close to the boundary 27 due to the large amount of negative charges. Looks like. In this sense, the accumulated electron 25 region is called a virtual electrode. When the switch 19 is operated to apply a forward electric field between the anode 3 and the cathode 15, the anode 3 injects holes along the virtual electrode 25 toward the first layer 21. Since the negative charge of the virtual electrode is close to the anode 3, the injection of holes from the anode 3 is promoted. The holes injected into the first layer 21 actually move toward the cathode 15 or the second layer 23 due to the injection momentum from the anode and the forward electric field between the anodes 3 and 15. The high hole mobility of the first layer 21 material actually promotes hole transfer towards the electrode 15 or the second layer 23.

A similar phenomenon occurs in the second layer 23 and a virtual anode can be formed by the accumulation of holes along the boundary 29 between the cathode 15 and the second layer 23. The 23 substances in the second layer are selected from substances that are more stable in the oxidized state in the neutral state, and have low hole mobility and high electron mobility among them. Holes are transmitted from the cathode 15 to the second layer 23 and accumulate near the boundary between the cathode 15 and the second layer 23. The accumulated holes look like a virtual anode from the perspective view of the cathode 15. When an appropriate electric field is applied in the forward direction, the cathode 15 causes electrons to be injected into the second layer 23.

According to various embodiments of the present invention, charge carriers are accumulated in the internal region of the device to form a virtual electrode. In the organic EL element 16 (FIG. 7), for example, the first layer 21 can form a hole injection layer, a hole transfer layer, a light emitting layer, or a multifunctional stratification having the functions of the above-mentioned layer. Instead, the first layer 21 may be absent and the anode 3 contacts the second layer 23. The second layer 23 constitutes, for example, a hole transfer layer, a light emitting layer, an electron transfer layer, an electron injection layer, or a multifunctional stratification having one or more functions of the above-mentioned layer. Instead, the second layer 23 may not be present and the cathode 15 comes into contact with the first layer. The phenomenon is discussed for organic EL devices with one or more layers 21 and 23, but for organic EL devices with other configurations, for example, devices with two or more layers between the anode 3 and the cathode 15. Applies to the same.

In the embodiment of the organic EL device forming the virtual electrode, the first layer 21 contains a compound that is more stable in its neutral state and in its reduced state. Optionally, such compounds are selected from the compounds represented by the general formula I. Preferably, the first layer comprises a compound of the general formula Ia. In other embodiments, the compound for layer 1 21 has a reduction potential of about -0.6 to about 0 V, preferably about -0.2 to about 0 V. Instead, the reduction potential of the compound for layer 1 21 is about -0.3 to about 0 V, optionally about -0.1 to about 0 V. In the first layer 21, electrons have low mobility, while holes contain compounds having high mobility. About 10 compounds for layer 1 21^-5Same as or lower than, preferably about 10^-10~ About 10^-6It has electron mobility of cm / Vs. 10 compounds for layer 1 21^-4Has hole mobility equal to or higher than cm / Vs. About 10 compounds for layer 1 21^-4Equal to or higher than cm / Vs, preferably about 10^-4It has a hole mobility of up to about 1 cm / Vs.

In one embodiment of the organic EL device forming the virtual electrode, the second layer 23 contains a compound that is more stable in its neutral state and in its oxidized state. In other embodiments, the second layer 23 comprises a second layer 23 compound having an oxidation potential equal to or lower than about 0.5 V. Instead, the oxidation potential of the compound is from about 0 to about 0.4 V, preferably from about 0 to about 0.3 V. In the second layer 23, holes have low mobility, while electrons contain compounds having high mobility. Layer 2 23 compounds are about 10^-4Same as or lower than, preferably about 10^-10~ About 10^-5It has a hole mobility of cm / Vs. Layer 2 23 compounds are about 10^-5Same as or higher than cm / Vs, preferably 10^-5It has electron mobility of up to about 1 cm / Vs.

<u style="single">Work function of electrode material</u> Another aspect of the invention relates to the use of substances with a low work function within anode 3. It is generally known in the art that the anodic material is selected from materials with a relatively high work function, while the cathodic material is selected from materials with a relatively low work function. However, according to embodiments of the present invention, organic EL devices include an anode that uses a material with a relatively low work function. For example, the work function of the anode material is about 4.5 eV or less, preferably about 4.3 eV or less. In other cases, the work function of the anodic material is about 3.5 to about 4.5 eV, preferably about 3.8 to about 4.3 eV. Materials for use in the anode include, for example, aluminum (Al, 4.28eV), silver (Ag, 4.26eV), zinc (Zn, 4.33eV), niobium (Nb, 4.3eV), zirconium (Zr, 4.05eV). ), Tin (Sn, 4.42eV), Tantal (Ta, 4.25eV), Vanadium (V, 4.3eV), Mercury (Hg, 4.49eV), Gallium (Ga, 4.2eV), Indium (In, 4.12eV), Cadmium (Cd, 4.22eV), Boron (B, 4.4eV), Hafnium (Hf, 3.9eV), Lantern (La, 3.5eV), Niobium (Nb, 4.3eV), Titanium (Ti, 4.3eV), or these Includes an alloy of one of them with neodymium (Nd) or palladium (Pd).

A possible non-restrictive explanation for the use of a relatively low work function material in the anode is that the low work function anode material facilitates the formation of the virtual electrode. With reference to FIG. 7 again, the low work function anode 3 material easily transfers electrons to the first layer 21 when a contact is formed between the anode 3 and the first layer 21. Electron transfer from the anode 3 to the first layer 21 is enhanced by the application of an appropriate voltage. The electrons transferred from the virtual electrode 25 into the first layer 21 promote hole injection from the anode 3 into the first layer 21 toward the actual cathode 15.

According to one embodiment of the invention, the work function of the cathode material is less than about 4.5 eV. Substances for use in the cathode 15 include, for example, magnesium, calcium, sodium, potassium, titanium, indium, iturium, lithium, gadolinium, aluminum, silver, tin, lead, similar metals, CsF, and one or more of the above metals. Contains alloys, or LiF / Al and Li₂It is a multi-layer containing one or more of the metals containing O / Al. Depending on the light-transmitting structure of the organic EL device discussed above, a transparent or opaque material can be used for the cathode 15. One of ordinary skill in the art can recognize any other substance that can be used within the cathode 15 and select the appropriate cathode material.

According to one embodiment of the invention, the anode 3 has a monolayer structure formed of a single material that can be a substantially pure elemental material or a homogeneous or heterogeneous alloy. In other embodiments, the anode 3 can include multiple sublayers with or without non-conductive sublayers. Optionally, the above discussion of the work function of the anode material applies only to the conductive portion of the anode 3 and not to the non-conductive sublayer or portion of the anode. Optionally, the anode 3 can have one or more conductive material sublayers. If the anode contains a multi-conductive material sublayer, the above discussion of the work function of the anode material applies to at least one conductive material.

Another aspect of the invention relates to the use of substances with a high work function within the cathode 15. Similar to the low work function anode, the high work function cathode material assists in the formation of the virtual anode. According to one embodiment of the invention, the organic EL device 10 includes a cathode 15 that uses a substance with a high work function. For example, the work function of the cathode material is about 3.5 eV, preferably about 4 eV. Otherwise, the work function of the cathode material is about 4.1 to about 5.0 eV, preferably about 4.1 to about 4.8 eV.

<u style="single">Anode reflective material</u> Another aspect of the present invention relates to the use of reflective material in the anode 3 of the organic EL device. In one embodiment of the organic EL device according to the invention, the anode is made of one or more substances with high reflectance. For example, the reflectance, which is the ratio of the reflected light intensity to the input light intensity, is about 0.2, for example, about 0.4 to 1. Reflective materials for use within the anode 3 include, for example, aluminum, silver, gold, nickel, chromium, molybdenum, tantalum, titanium and zinc. Optionally, the material has reflectance for virtually all wavelength components of visible light. Optionally, the material has equivalent reflectance for virtually all wavelength components of visible light. Preferably, the anodic reflective material is, for example, aluminum, silver, platinum, chromium and nickel.

In one embodiment of the invention, the anode 3 can include multiple sublayers. Optionally, the anode 3 is formed of at least one transparent and reflective sublayer. The at least one transparent sublayer is formed of a transparent material containing, for example, ITO (indium tin oxide), IZO (indium zinc oxide), and fluorotin oxide. As an alternative embodiment, the anode 3 is a single layer formed of a reflective material. The single-layered anode is advantageous over the multi-layered structure in terms of simplicity in the manufacturing process.

<u style="single">Top radiation</u> In the configuration shown in FIGS. 1 to 6 in which the anode 3 instead of the cathode 15 contacts the substrate 1, the light generated by the use of the reflective substance in the anode 3 is radiated through the cathode 15 or in a direction not passing through the anode 3. In FIGS. 1 to 6, the radiation through the cathode 15 is called the top radiation, and the radiation through the anode 3 and the substrate 1 is called the bottom radiation. Optionally, the OLED device 10 can be configured with a top radiation design. Due to the apical radiation, the cathode 15 is substantially transparent.

In one embodiment, the substantially transparent cathode 15 is formed of a single layer of one or more transparent conductive materials. Examples of transparent conductive materials include ITO, IZO and tin fluoride oxide. In other cases, a substantially transparent cathode 15 is formed with multiple layers (not shown). For example, the multi-layered cathode 15 can include a thin layer and a transparent material layer formed of an opaque material under normal conditions. The thin layer of the opaque substance in the normal state is formed with a thickness that allows visible light emitted from the organic EL substance to pass through. Optionally, the thickness of the thin layer is from about 10 Å to 500 Å, preferably from about 10 Å to 200 Å. Normal and opaque substances for use in said thin layers include, for example, magnesium (Mg), calcium (Ca), lithium (Li), aluminum (Al), indium (In), potassium (K), samarium. Includes (Y), strontium (St), europium (Eu), sodium (Na), gallium (Ga), samarium (Sm) or alloys or mixtures of two or more of the elements described above. The transparent material layer is formed of, for example, one or more substances such as indium tin oxide (ITO), indium zinc oxide (IZO), and tin oxide oxide. The thickness of the transparent material layer is about 100 to 5000 Å. The cathode 15 in the multi-layer structure includes one or more layers.

<u style="single">Control circuit position and type</u> The top radiating design of an OLED device is generally more suitable for active matrix driving of the device than the bottom radiating design. The active matrix drive requires a layer 31 for an integrated circuit or transistor between the substrate 1 and the anode 3 as illustrated in FIG. In an organic EL device having a bottom emission design, the integrated circuit layer 31 blocks at least part of the light emitted from the luminescent compound. However, the top radiation design is unaffected by the presence of the integrated circuit layer 31 under the anode 3. The top radiation design is also unaffected by techniques for forming integrated circuit layers 31, such as the use of amorphous silicon or polysilicon, which affect the aperture ratio of layer 31.

In one embodiment of the top radiation design, the OLED device uses a manual matrix or active matrix circuit design. Optionally, the top radiation design uses an active matrix circuit design. Optionally, an integrated circuit for active matrix drive is located between substrate 1 and anode 3. Optionally, the integrated circuit is formed by amorphous silicon technology.

<u style="single">Sealing layer</u> In certain embodiments of the organic EL device, it is advantageous to have a sealing layer between the substrate 1 and the anode 3 to prevent moisture or other contaminants from penetrating into the complex regions of the laminated structure. .. Such a sealing layer is even more important, especially if the material constituting the substrate 1 is more permeable. Such substances are, for example, aluminum, aluminum oxide, strontium oxide, barium oxide, silicon oxide, silicon nitride. The sealing layer can be composed of a multi-layer including at least one organic sublayer and at least one inorganic sublayer. The organic sublayer can be formed, for example, from polyphenylethylene, a polymerized epoxy compound and / or a polycyclic alkane. The inorganic sublayer can be formed of, for example, silicon nitride, silicon oxide and / or barium oxide. A material that is substantially impermeable or semi-permeable, and where it can be used as an anode material, the anode 3 itself forms a sealing layer. Therefore, it is not necessary to form a separate sealing layer. In one embodiment of the invention, the anode 3 is made of aluminum, aluminum-neodymium alloy or aluminum-palladium alloy, which also functions as a sealing layer. The anode 3, which also functions as a sealing layer, is used with any suitable substrate material with or without an integrated circuit layer 31 between the substrate 1 and the anode 3.

<u style="single">Non-conductive anode sublayer</u> In any organic EL device embodiment of the present invention, one or both of the anode 3 and the cathode 15 can be formed of multiple sublayers. Referring to FIG. 9, for example, the anode 3 of the illustrated organic EL device includes a conductive sublayer 33 and a non-conductive sublayer 35. Anode 3 can have more than two sublayers, even if shown in two sublayers. As shown, the non-conductive sublayer 35 is located between the hole injection layer 5 and the conductive sublayer 33 and contacts the anode 3 on the side facing the cathode 15. The hole injection layer 5 in the laminated anode structure can be replaced by a hole transfer layer 7 (FIGS. 4 and 5), a light emitting layer 9 (FIG. 6), or a multifunctional stratification (not shown). On the other hand, the non-conductive sublayer 35 can be regarded as a separate layer inserted between the layers 5, 7 or 9 in contact with the anode 3 and the anode 3.

The non-conductive sublayer 35, which is considered a separate layer, is called the buffer layer. Regardless of its name, the non-conductive sublayer, also known as buffer layer 35, enhances the interfacial strength between the conductive sublayer 33 (or anode 3) and the layers 5, 7 or 9 in contact with anode 3. It is formed to make it. The non-conductive sublayer, also known as the buffer layer 35, also provides an energy barrier for hole injection into layers 5, 7 or 9 in contact with the non-conductive sublayer 35 from the conductive sublayer 33. Help lower. In one embodiment, the non-conductive sublayer or buffer layer 35 is formed of one or more inorganic materials. Optionally, the material for the buffer layer is, for example, aluminum oxide, titanium oxide, zinc oxide, ruthenium oxide, nickel oxide, zirconium oxide, tantalum oxide, magnesium oxide, calcium oxide, Strontium oxide, vanadium oxide, yttrium oxide, lithium oxide, cesium oxide, chromium oxide, silicon oxide, barium oxide, manganese oxide, cobalt oxide, copper oxide, placeodym oxide, tungsten oxide Things, germanium oxide, potassium oxide, lithium fluoride, magnesium fluoride, cesium fluoride, calcium fluoride, sodium chloride, potassium chloride, lithium metaboron (BiBO)₂), Potassium silicate (K₂SiO₃), Silicon-germanium oxide, barium titanate, lithium tantalate (LiTaO)₃), Silicon Nitride (Si)₃N₄), Borone nitride (BN), Nitride of elements belonging to groups 3 and 4 of the Periodic Table of the Elements, Zinc sulfide (ZnS), Cadmium sulfide (CdS), Cadmium selenide (CdSe), Gallium phosphate (GaP) , And two or more combinations of gallium nitride (GaN) and the above-mentioned materials.

<u style="single">Manufacture of elements</u> The various layers of the organic EL element of the present invention include sputtering, electron beam deposition, and other types of physical vapor deposition, chemical vapor deposition, spin coating, dip coating, doctor blades, inkjet printing, etc. It can be manufactured using any film forming technique, including screen-printing, roll-coating and heat transfer. Such techniques are generally described in the following references, which are collectively integrated with reference to the present application: Applied Physic Letters, 73, 18, 1998, 2561-2563; Applied Physics Letters, 78, 24. , 2001, 3905-3907. Those skilled in the art will understand the conditions for layer formation and suitable film forming techniques in the environment.

[Example] Various aspects and features of the invention are additionally discussed through the following examples. The following examples are intended to illustrate various aspects and features of the invention and do not limit the scope of the invention.

<u style="single">Example 1</u> A glass substrate (Corning 7059) was coated with approximately 1300 Å indium tin oxide (ITO) and ultrasonically cleaned in Fisher Co.'s aqueous cleaning agent. The washed ITO layered substrate was dried and transferred to a plasma cleaning device. The substrate was additionally washed with argon-oxygen (2: 1) plasma at 50 W at 14 mtorr for 5 minutes. The substrate was then moved to a vacuum deposition chamber.

A translucent aluminum anode was formed by hot-vacuum deposition of an aluminum layer of about 100 Å on the ITO layer. The aluminum layer was exposed to oxygen gas under atmospheric pressure for 5 minutes to form an aluminum oxide layer of about 20 Å. A hole-injected layer of a compound of general formula Ia (hexanitrile hexazatriphenylene or HAT) was formed on the aluminum oxide layer by thermal vacuum deposition at about 500 Å. A hole transfer layer was formed on the hole injection layer by thermal vacuum deposition at about 400 Å using NPB. Alq is formed on the hole transfer layer by thermal vacuum deposition of a light emitting layer.₃Was formed at about 300 Å. A compound of general formula II (2- [4-[(N-phenylbenzimidazol-2-yl) phenyl-9,10-bis (2-naphthyl) anthracene) was deposited on the light emitting layer by hot vacuum deposition. ] Was formed at about 200 Å. For cathode formation, about 10 Å of lithium fluoride (LiF) layer was formed on the electron transfer layer, and then about 2500 Å of aluminum layer was additionally deposited. During vapor deposition, the pressure in the vapor deposition chamber is 5-8 x 10^-7Maintained to torr. Organic material was deposited at a rate of 1 Å / sec. Lithium fluoride was deposited at a rate of 0.3 Å / sec and aluminum was deposited at a rate of 3-7 Å / sec.<chemistry num="9"><img id="000010" he="73" wi="71" file="JP5259128B2_D0001.tif" img-format="tif" img-content="drawing" /></chemistry>The resulting laminated structure of organic EL elements is "glass substrate / ITO (1300 Å) / Al (100 Å) / Al.₂O₃(20 Å) / HAT (500 Å) / NPB (400 Å) / Alq₃(300 Å) / General formula II (200 Å) / LiF (10 Å) / Al (2500 Å) . Observed through a clear aluminum layer. Emission color was confirmed at x = 0.4460, y = 0.550 in 1931 CIE color coordinates. Current density during operation was 50mA / cm.²Met.

<u style="single">Example 2</u> Al without forming an ITO layer₂O₃The element was manufactured in the same manner as in Example 1 except that no layer was formed. The obtained structure is "Glass substrate / Al (100 Å) / HAT (500 Å) / NPB (400 Å) / Alq₃(300 Å) / General formula II (200 Å) / LiF (10 Å) / Al (2500 Å) .

When applied to the device obtained a forward electric field of 5.0 V, 1,010 nit emission was observed through the translucent aluminum layer. The emission color was confirmed at x = 0.417 and y = 0.534 in 1931 CIE color coordinates. Current density during operation is 50mA / cm²Met.

<u style="single">Comparative example 1</u> The device was manufactured by the same method as in Example 1 except that the HAT hole injection layer was not formed. The structure of the obtained device is "Glass substrate / ITO (1300 Å) / Al (100 Å) / Al₂O₃(20Å) / NPB (400Å) / Alq₃(300 Å) / General formula II (200 Å) / LiF (10 Å) / Al (2500 Å) . When a forward electric field of 20 V was applied to the device, no light emission was observed. A forward electric field was applied. Current density is 0.1mA / cm²Was less than.

<u style="single">Comparative example 2</u> The device was manufactured by the same method as in Example 1 except that an aluminum and aluminum oxide layer was not formed between ITO and NPB. The resulting structure is "Glass substrate / ITO (1300 Å) / HAT (500 Å) / NPB (400 Å) / Alq₃(300 Å) / General formula II (200 Å) / LiF (10 Å) / Al (2500 Å) . When applied to a device with a forward electric field of 5.37 V, x = 0.345 in 1931 CIE color coordinates, Green light emission corresponding to y = 0.553 was observed. The current density during operation was 50 mA / cm.²Met. 100mA / cm²At a constant DC current density, it took 23 hours for the initial brightness of 3399 nits to drop to the 80% level.

<u style="single">Example 5</u> The device was manufactured by the same method as in Example 1 except that silver having a thickness of 100 Å was formed as a translucent anode instead of aluminum and aluminum oxide. The structure of the obtained device is "Glass substrate / ITO (1300 Å) / Ag (100 Å) / HAT (500 Å) / NPB (400 Å) / Alq₃(300 Å) / General formula II (200 Å) / LiF (10 Å) / Al (2500 Å) . When applied to a device with a forward electric field of 5.1 V, x = 0.420 in 1931 CIE color coordinates, Emissions with a brightness of 800 nits corresponding to y = 0.516 were observed. The current density during operation was 50 mA / cm.²Met.

<u style="single">Example 6</u> The element was manufactured by the same method as in Example 1 except that the ITO layer was not formed. The resulting structure is "Glass substrate / Ag (100 Å) / HAT (500 Å) / NPB (400 Å) / Alq₃(300 Å) / General formula II (200 Å) / LiF (10 Å) / Al (2500 Å) . Visible light was observed when applied to the device in which a forward electric field was obtained.

<u style="single">Example 7</u> A glass substrate (Corning 7059) coated with approximately 1300 Å of indium tin oxide (ITO) was ultrasonically cleaned in Fisher Co.'s aqueous cleaning agent. The washed ITO layered substrate was dried and transferred to a plasma cleaning device. Substrates were additionally washed with argon-oxygen (2: 1) plasma at 50 W under 14 mtorr for 15 minutes. The substrate was then moved to a vacuum deposition chamber.

A compound of the general formula Ia (hexanitrile hexazatriphenylene or HAT) was formed on the ITO layer by thermal vacuum deposition at about 2000 Å. About 500 Å of aluminum was deposited on the compound layer to form a cathode. During deposition, the pressure in the deposition chamber is 5-8 x 10^-7Maintained in torr.v. Organic matter was deposited at a rate of 1 Å / sec and aluminum was deposited at a rate of 3-7 Å / sec.

The laminated structure of the obtained organic EL element was "glass substrate / ITO (1300 Å) / HAT (2000 Å) / Al (500 Å)". When a forward electric field was applied to the device, a current was observed with a potential difference just above 0V. The voltage-current relationship is shown in Fig. 10.

<u style="single">Comparative example 3</u> The device was manufactured by the same method as in Example 7, except that an NPB having a thickness of 1600 Å was formed instead of the HAT. The structure of the obtained device was "glass substrate / ITO (1300 Å) / NPB (1600 Å) / Al (500 Å)". When a forward electric field was applied to the device, a current was observed with a potential difference of about 1 V. The voltage-current relationship is shown in Fig. 10.

<u style="single">Example 9</u> The device was manufactured in the same manner as in Example 7, except that a 500 Å aluminum layer was formed as an anode instead of the ITO layer. The obtained structure was "glass substrate / Al (500 Å) / HAT (2000 Å) / Al (500 Å)". When a forward electric field was applied to the device, a current was observed with a potential difference just above 0V. The voltage-current relationship is shown in Fig. 11.

<u style="single">Comparative example 4</u> The device was manufactured in the same manner as in Example 9 except that a 2000 Å thick NPB was formed in place of the HAT. The structure of the resulting device was "glass substrate / Al (500 Å) / NPB (2000 Å) / Al (500 Å)". When a forward electric field was applied to the device, no current was observed even with a potential difference of more than 20V. The voltage-current relationship is shown in Fig. 11.

<u style="single">Example 11</u> An electric potential is applied to the element manufactured in Example 9 having a structure of "glass substrate / Al (500 Å) / HAT (2000 Å) / Al (500 Å)" with the opposite polarity to that of Example 9, where the glass substrate and HAT are applied. The aluminum located between and acted as a cathode, and the aluminum located on the HAT acted as an anode. When a forward electric field was applied, a current began to flow directly above 0V. The voltage-current relationship is shown in Fig. 12. The results, together with the results of Example 9, indicate that the aluminum layer is deposited above or below the HAT layer, or that the HAT layer causes the aluminum layer to inject holes into it.

<u style="single">Comparative example 5</u> An electric potential was applied to the element manufactured in Comparative Example 4 having the configuration of "glass substrate / Al (500 Å) / NPB (2000 Å) / Al (500 Å)" with the opposite polarity to that of Comparative Example 4, and the glass substrate and NPB were applied here. The aluminum located between the layers acted as a cathode and the aluminum located on the HAT acted as an anode. When a forward electric field was applied, no current was observed with a potential difference of 20 V or more. The voltage-current relationship is shown in Fig. 12.

[Related application] This application claims foreign priority based on Republic of Korea Patent Application No. 2002-78809 filed on December 11, 2002, which is incorporated herein by reference in its entirety.

<figref num="1">It is the schematic sectional drawing of the organic EL element and the like by embodiment of this invention.</figref><figref num="2">It is the schematic sectional drawing of the organic EL element and the like by embodiment of this invention.</figref><figref num="3">It is the schematic sectional drawing of the organic EL element and the like by embodiment of this invention.</figref><figref num="4">It is the schematic sectional drawing of the organic EL element and the like by embodiment of this invention.</figref><figref num="5">It is the schematic sectional drawing of the organic EL element and the like by embodiment of this invention.</figref><figref num="6">It is the schematic sectional drawing of the organic EL element and the like by embodiment of this invention.</figref><figref num="7">The formation of a virtual electrode in an electronic device according to the embodiment of the present invention is shown.</figref><figref num="8">It is the schematic sectional drawing of the active matrix drive organic EL element by embodiment of this invention.</figref><figref num="9">FIG. 5 is a schematic cross-sectional view of an organic EL device using a non-conductive sublayer in the anode according to the embodiment of the present invention.</figref><figref num="10">The voltage-current relationship is shown in the element operation of Example 7 and Comparative Example 3.</figref><figref num="11">The voltage-current relationship is shown in the operation of the elements of Example 9 and Comparative Example 4.</figref><figref num="12">The voltage-current relationship is shown in the operation of the elements of Example 11 and Comparative Example 5.</figref>

Code description

1 board 3 Anode 5 hole injection layer 7 Hole transfer layer 9 light emitting layer 11 Electron transfer layer 13 Electron injection layer 15 Cathode