Organic electroluminescent element

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an organic electroluminescent device, and more particularly to a thin film type device that emits light by applying an electric field to a light emitting layer made of an organic compound.

【0002】

[Conventional technology]

Conventionally, thin-film electroluminescent (EL) devices include inorganic materials such as ZnS, CaS, and SrS, which are group II-VI compound semiconductors, as well as Mn and rare earth elements (Eu, Ce, Tb, Sm, etc.), which are the centers of light emission. ) Is generally doped, but EL devices made from the above inorganic materials are 1) AC drive required (50 ~ 1000Hz), 2) High drive voltage (~ 200V), 3) Difficult to make full color (especially blue), 4) The cost of peripheral drive circuits is high, It has a problem.

【0003】

However, in recent years, in order to improve the above problems, EL devices using organic thin films have been developed. In particular, in order to increase the luminous efficiency, the type of electrode was optimized for the purpose of improving the efficiency of carrier injection from the electrode, and a hole transport layer composed of an aromatic diamine and a luminous layer composed of an aluminum complex of 8-hydroxyquinoline were used. By developing an organic electroluminescent device (Appl. Phys. Lett., Vol. 51, p. 913, 1987), the luminous efficiency is significantly improved compared to the conventional EL device using a single crystal such as anthracene. Has been made. Further, for example, by doping a laser fluorescent dye such as coumarin using an aluminum complex of 8-hydroxyquinoline as a host material (J. Appl. Phys., Vol. 65, p. 3610, 1989), the emission efficiency is improved. And the conversion of the emission wavelength are also performed, and it is approaching the practical characteristics.

【0004】

In addition to the electroluminescent elements using low molecular weight materials as described above, poly (p-phenylene vinylene) and poly [2-methoxy-5- (2-ethylhexyloxy) -1,4 can be used as materials for the light emitting layer. -Development of electroluminescent devices using polymer materials such as [phenylene vinylene] and poly (3-alkylthiophene), and development of devices in which low molecular weight light emitting materials and electron transfer materials are mixed with polymers such as polyvinylcarbazole. It is done.

【0005】

As an attempt to increase the luminous efficiency of the device, the use of phosphorescence instead of fluorescence is also being studied. If phosphorescence is used, that is, light emission from a triplet excited state is used, efficiency improvement of about 3 times is expected as compared with a device using conventional fluorescence (singlet term). For this purpose, it was considered to use a coumarin derivative or a benzophenone derivative as a light emitting layer (51st Japan Society of Applied Physics Joint Lecture, 28a-PB-7, 1990), but very low brightness was obtained. .. Since then, the use of a europium complex has been studied as an attempt to utilize the triplet state, but this also did not lead to highly efficient light emission.

【0006】

Recently, it has been reported that highly efficient red emission is possible by using the platinum complex (T-1) shown below (Nature, 395, 151, 1998). After that, by doping the light emitting layer with the iridium complex (T-2) shown below, the efficiency was further greatly improved by green light emission (Appl. Phys. Lett., Vol. 75, p. 4, 1999).

【0007】

[Chemical 8]

<img file="JP2002305083A_D0001.tif" />【0008】

[Problems to be Solved by the Invention]

In order to apply an organic electroluminescent element to a display element such as a flat panel display, it is necessary to improve the luminous efficiency of the element and at the same time ensure sufficient stability during driving. However, although the organic electroluminescent device using the phosphorescent molecule (T-2) described in the above-mentioned document emits high-efficiency light, its drive stability is insufficient for practical use (Jpn. J. Appl. Phys). ., Vol. 38, L1502, 1999), it is difficult to realize a highly efficient display element.

【0009】

It is presumed that the main cause of the above drive deterioration is the deterioration of the light emitting layer. The electric charge injected from the electrode becomes an electron-hole pair (exciton) with a certain probability. In general, emission by triplet excitons (phosphorescence) has a longer lifetime than emission by singlet excitons (fluorescence), and conversely, singlet excitons are more thermally stable than triplet excitons. Is also expensive. Here, as the current applied to the device increases, the charge injected into the light emitting layer increases, and the amount of charge that does not become an exciton also increases accordingly. In addition, among the excitons, those that do not contribute to light emission and are heat-deactivated in the light emitting layer increase. Therefore, the temperature of the light emitting layer rises, and in particular, the triplet excitons are inferior in thermal stability as compared with the singlet excitons, so that it is considered that the device deteriorates. This is also estimated from the fact that the luminous efficiency of the organic electroluminescent device using phosphorescent molecules (T-2) decreases significantly as the injection current increases (Appl. Phys. Lett., Vol. 75, p. 4, 1999). Year).

【0010】

Most of the organic electroluminescent devices using phosphorescent molecules developed so far are characterized in that a material containing a carbazolyl group is used as a host of the light emitting layer. For example, the above document (Appl. Phys. Lett., Vol. 75, p. 4, 1999) uses the following biphenyl derivatives as host materials.

【0011】

[Chemical 9]

<img file="JP2002305083A_D0002.tif" />However, it is known that the above (H-1) is very easy to crystallize and the stability of the film is poor. For the above reasons, the actual situation is that the organic electroluminescent device using phosphorescent molecules has a big problem in the drive stability of the device toward practical use.

【0012】

In view of the above circumstances, the present inventor has diligently studied for the purpose of providing an organic electroluminescent device having high efficiency and high drive stability. As a result, by using a specific compound for the light emitting layer, it is difficult to crystallize and is stable. They have found that a light emitting layer can be obtained and the above problems can be solved, and have completed the present invention.

【0013】

[Means for solving problems]

That is, the gist of the present invention is an organoelectroluminescent element in which at least an anode, a light emitting layer, and a cathode are sequentially laminated on a substrate, and the light emitting layer is at least one selected from groups 7 to 11 of the periodic table. An organic electroluminescent element comprising an organometallic complex containing a metal and an organometallic complex represented by the following general formula (I).

【0014】

[Chemical 10]

<img file="JP2002305083A_D0003.tif" />(In the equation, M represents a metal selected from Group 1, Group 2, Group 3, Group 12, or Group 13 of the Periodic Table, n represents the valence of the metal, L represents any substituent, j Represents the number of substituents L and is 0 or 1. X represents a carbon atom or a nitrogen atom. Ring A represents a nitrogen-containing heterocycle and may have substituents. Ring B represents aromatic carbonation. It represents a hydrogen ring or an aromatic heterocycle and may have a substituent.)

【0015】

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, the light emitting layer contains an organometallic complex represented by the general formula (I) and an organometallic complex containing at least one metal selected from groups 7 to 11 of the periodic table, that is, an organic using so-called phosphorescence. Regarding the electroluminescent element, it preferably contains an organometallic complex represented by the general formula (I) as a main component and an organometallic complex containing at least one metal selected from the groups 7 to 11 of the periodic table as a subcomponent. Has a light emitting layer.

【0016】

Here, the "main component" means a material that occupies 50% by weight or more of the materials forming the layer, and the "sub-component" means a material that occupies less than 50% by weight of the materials forming the layer. To do. In the organic electric field light emitting element of the present invention, the organic metal complex represented by the general formula (I) contained in the light emitting layer is an excitation of a phosphorescent organic metal complex containing a metal selected from groups 7 to 11 contained in the layer. It is basically necessary to have an excited triplet level with a higher energy state than the triplet level. It also needs to be a compound that provides a stable thin film shape, has a high glass transition temperature (Tg), and is capable of efficiently transporting holes and / or electrons. Further, it is required to be a compound that is electrochemically and chemically stable, and that impurities that act as traps or quench light emission are less likely to be generated during production or use.

【0017】

In the present invention, an organometallic complex compound represented by the general formula (I) is used as a material for forming a light emitting layer satisfying these conditions. In particular, as the organometallic complex compound represented by the general formula (I), an organometallic complex (hereinafter, general formula (II)), a mixed ligand complex (hereinafter, general formula (III)), or a dinuclear metal complex (hereinafter, general). The organometallic complex compound represented by the formula (IV)) is preferable.

[Organometallic complex] [0018]

[Chemical 11]

<img file="JP2002305083A_D0004.tif" />(In the formula, M¹Is a monovalent to trivalent metal, and n, X, ring A and ring B are synonymous with in formula (I).

[Mixed ligand complex] [0019]

[Chemical 12]

<img file="JP2002305083A_D0005.tif" />(In the formula, M²Represents a trivalent metal. X, ring A and ring B are synonymous with in equation (I). L¹Represents the following general formula (IIIa), (IIIb) or (IIIc).

【0020】

[Chemical 13]

<img file="JP2002305083A_D0006.tif" />(During the ceremony, Ar¹~ Ar⁵Represents an aromatic hydrocarbon ring group which may have a substituent or an aromatic heterocyclic group which may have a substituent, and Z¹Represents silicon or germanium.

[2 nuclear metal complex] [0021] [0021]

[Chemical 14]

<img file="JP2002305083A_D0007.tif" />(In the formula, M³And M³ Represents a trivalent metal. X, ring A and ring B are synonymous with in equation (I), X'is synonymous with X, ring A'is synonymous with ring A, and ring B'is synonymous with ring B. ) In addition, a plurality of the following structural parts contained in one molecule of the compound represented by the general formulas (I) to (IV). [0022]

[Chemical 15]

<img file="JP2002305083A_D0008.tif" />【0023】

(In the general formula (IV), the following structural parts are present in two in one compound. [0024]

[Chemical 16]

<img file="JP2002305083A_D0009.tif" />【0025】

), That is, ring A, ring B, and X (in the case of equation (IV), ring A, ring A', ring B, ring B', X, and X') may be the same. It may be different. From the viewpoint of ease of synthesis, it is preferable that they are all the same. Similarly, M in the compound represented by the general formula (IV)³And M³The may be the same or different, and is preferably the same from the viewpoint of easy synthesis. The rings A, ring A', ring B, and ring B'of the compounds represented by the general formulas (I) to (IV) are preferably selected from the following, respectively.

It is a 5- or 6-membered nitrogen-containing aromatic heterocycle which may have a [ring A and ring A'] substituent, and the ring is a 5- or 6-membered aromatic hydrocarbon ring or aromatic ring. One or two group heterocycles may be fused to form a fused ring.

It is a 6-membered aromatic hydrocarbon ring or aromatic heterocycle which may have a [ring B and ring B'] substituent, and the ring is a 5- or 6-membered aromatic hydrocarbon ring or aromatic. One or two heterocycles may be fused to form a fused ring.

【0026】

The rings A, A', B, and B'of the compounds represented by the general formulas (I) to (IV) are more preferably monocyclic, and among them, rings selected from the following are preferable. ..

[Ring A and Ring A'] A diazole ring, a thiazole ring, an oxazole ring, a thiadiazole ring, an oxadiazole ring, a triazole ring, a pyridine ring, a diazine ring, and a triazine ring, which may have substituents, respectively.

[Ring B and Ring B'] A benzene ring, a pyridine ring, a diazine ring, and a triazine ring, each of which may have a substituent.

【0027】

Further, the rings A, ring A', ring B, and ring B'of the compounds represented by the general formulas (I) to (IV) are most preferably selected from the following structural formulas, respectively.

[Ring A and Ring A'] [0028]

[Chemical 17]

<img file="JP2002305083A_D0010.tif" />(In the formula, R₁~ R₇Independently, hydrogen atom, halogen atom, alkyl group, aralkyl group, alkenyl group, cyano group, amino group, acyl group, alkoxycarbonyl group, carboxyl group, alkoxy group, alkylamino group, aralkylamino group, haloalkyl group, An aromatic hydrocarbon ring group which may have a hydroxyl group, an aryloxy group, a substituent or an aromatic heterocyclic group which may have a substituent, or R₁And R₂, R₁And R₃, R₄And R₅, R₅And R₆, Or R₆And R₇May combine to form a ring.

[Ring B and Ring B'] [0029]

[Chemical 18]

<img file="JP2002305083A_D0011.tif" />(In the formula, R₈~ R₁₁Independently, hydrogen atom, halogen atom, alkyl group, aralkyl group, alkenyl group, cyano group, amino group, acyl group, alkoxycarbonyl group, carboxyl group, alkoxy group, alkylamino group, aralkylamino group, haloalkyl group, It represents an aromatic hydrocarbon ring group which may have a hydroxyl group, an aryloxy group, a substituent or an aromatic heterocyclic group which may have a substituent, or R.₈And R₉ , R₉And R₁₀ , Or R₁₀ And R₁₁May combine to form a ring. ) Note that the two bonds in the structure of the above [ring B and ring B'] are oxygen atoms or ring A as long as they satisfy the definitions of the ring B and ring B'structures in the above formulas [I] to [IV]. And any of the atoms X in the ring A'may be bonded to any of them.

【0030】

R₁ ~ R₁₁Specifically, hydrogen atom; halogen atom; alkyl group having 1 to 6 carbon atoms such as methyl group and ethyl group; aralkyl group such as benzyl group; alkenyl group having 2 to 6 carbon atoms such as vinyl group; cyano group. Amino group; acyl group; carboxyl group; alkoxy group having 1 to 6 carbon atoms such as methoxy group and ethoxy group; alkoxycarbonyl group having 2 to 6 carbon atoms such as methoxycarbonyl group and ethoxycarbonyl group; phenoxy group and benzyloxy Aryloxy groups such as groups; Dialkylamino groups such as diethylamino groups and diisopropylamino groups; Diaralkylamino groups such as dibenzylamino groups and diphenethylamino groups; α-haloalkyl groups such as trifluoromethyl groups; hydroxyl groups; substituents An aromatic hydrocarbon ring group such as a phenyl group or a naphthyl group which may have a substituent; an aromatic heterocyclic group such as a thienyl group or a pyridyl group which may have a substituent.

【0031】

Examples of the substituent that the aromatic hydrocarbon ring group and the aromatic heterocyclic group can have include a halogen atom such as a fluorine atom; an alkyl group having 1 to 6 carbon atoms such as a methyl group and an ethyl group; and a carbon such as a vinyl group. Alkenyl group of number 2 to 6; alkoxycarbonyl group having 2 to 6 carbon atoms such as methoxycarbonyl group and ethoxycarbonyl group; alkoxy group having 1 to 6 carbon atoms such as methoxy group and ethoxy group; phenoxy group, benzyloxy group, etc. Aryloxy group; dialkylamino group such as dimethylamino group and diethylamino group; acyl group such as acetyl group; haloalkyl group such as trifluoromethyl group; cyano group and the like.

【0032】

In addition, R₁And R₂ , R₁And R₃, R₄And R₅, R₅And R₆, R₆And R₇, R₈And R₉ , R₉And R₁₀ , R₁₀And R₁₁Examples of the ring formed by bonding adjacent groups to each other include a benzene ring, a cyclohexane ring, and the like. R₁Or R₁₁It is preferably an aromatic hydrocarbon group which may have a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a haloalkyl group or a substituent, or is bonded to adjacent groups to form a ring. ..

【0033】

Metals M (M) of compounds represented by general formulas (I) to (IV)¹, M², M³And M³) Is not particularly limited as long as it is a metal selected from Group 1, Group 2, Group 3, Group 12 and Group 13 of the periodic table, but zinc, aluminum, gallium, beryllium, and magnesium are preferable. Preferred specific examples of the compounds represented by the general formulas (I) to (IV) are shown below, but the present invention is not limited thereto.

【0034】

[Chemical 19]

<img file="JP2002305083A_D0012.tif" />【0035】

[Chemical 20]

<img file="JP2002305083A_D0013.tif" />【0036】

[Chemical 21]

<img file="JP2002305083A_D0014.tif" />【0037】

[Chemical 22]

<img file="JP2002305083A_D0015.tif" />In addition, these compounds may be used alone as a main component in a light emitting layer, or may be mixed and used as needed. Further, the organic electroluminescent device of the present invention contains a phosphorescent organometallic complex containing a metal selected from Groups 7 to 11 of the Periodic Table as a subcomponent in the light emitting layer. Preferred examples of the metal include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum, and gold. Examples of these organometallic complexes include compounds represented by the following general formulas (Va), (Vb), and (VI).

【0038】

[Chemical 23]

<img file="JP2002305083A_D0016.tif" />(In the formula, M⁴Is a metal and n is the valence of the metal. Ring A1 represents an aromatic hydrocarbon ring or an aromatic heterocycle and may have a substituent. Ring A2 represents a nitrogen-containing aromatic heterocycle and may have a substituent.

【0039】

[Chemical 24]

<img file="JP2002305083A_D0017.tif" />(In the formula, M⁵Is a metal and n is the valence of the metal. Ring A1 represents an aromatic hydrocarbon ring or an aromatic heterocycle and may have a substituent. Ring A2 represents a nitrogen-containing aromatic heterocycle and may have a substituent.

【0040】

[Chemical 25]

<img file="JP2002305083A_D0018.tif" />(In the formula, M⁷Represents metal and T represents carbon or nitrogen. R if T is nitrogen₂₀Or R₂₃If T is carbon, then R₂₀Or R₂₃Are independently hydrogen atom, halogen atom, alkyl group, aralkyl group, alkenyl group, cyano group, amino group, acyl group, alkoxycarbonyl group, carboxyl group, alkoxy group, alkylamino group, aralkylamino group, haloalkyl group, hydroxyl group. , An aryloxy group, an aromatic hydrocarbon ring group which may have a substituent, or an aromatic heterocyclic group which may have a substituent.

【0041】

R₁₂Or R₁₉Independently, hydrogen atom, halogen atom, alkyl group, aralkyl group, alkenyl group, cyano group, amino group, acyl group, alkoxycarbonyl group, carboxyl group, alkoxy group, alkylamino group, aralkylamino group, haloalkyl group, It represents a hydroxyl group, an aryloxy group, an aromatic hydrocarbon ring group which may have a substituent, or an aromatic heterocyclic group which may have a substituent, or among these, adjacent groups are adjacent to each other. They may be connected to each other to form a ring. ) The ring A1 in the general formulas (Va) and (Vb) is preferably a 5- or 6-membered aromatic hydrocarbon ring or aromatic heterocycle which may have a substituent, and 5 or 6 in the ring. One or two aromatic hydrocarbon rings or aromatic heterocycles of member rings may be fused to form a fused ring. Specific examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, a thiophene ring, a furan ring, a benzothiophene ring, a benzofuran ring, a pyridine ring, a quinoline ring, and an isoquinoline ring.

【0042】

Further, the ring A2 is preferably a 5- or 6-membered nitrogen-containing aromatic heterocycle which may have a substituent, and the ring is a 5- or 6-membered aromatic hydrocarbon ring or an aromatic heterocycle. May be fused to form a fused ring. Specific examples thereof include a pyridine ring, a pyrimidine ring, a pyrazil ring, a triazine ring, a benzothiazole ring, a benzoxazole ring, a benzimidazole ring, a quinoline ring, an isoquinoline ring, a quinoxaline ring, and a phenanthridine ring.

【0043】

The substituents that the ring A1 and the ring A2 may have include a halogen atom such as a fluorine atom; an alkyl group having 1 to 6 carbon atoms such as a methyl group and an ethyl group; and a vinyl group having 2 to 6 carbon atoms. Alkenyl group; alkoxycarbonyl group having 2 to 6 carbon atoms such as methoxycarbonyl group and ethoxycarbonyl group; alkoxy group having 1 to 6 carbon atoms such as methoxy group and ethoxy group; aryloxy group such as phenoxy group and benzyloxy group; Examples thereof include a dialkylamino group such as a dimethylamino group and a diethylamino group; an acyl group such as an acetyl group; a haloalkyl group such as a trifluoromethyl group; a cyano group; an aryl group such as a phenyl group, and these are linked to each other to form a ring. It may be formed.

【0044】

The substituent of the ring A1 and the substituent of the ring A2 may be combined to form one fused ring, and examples thereof include a 7,8-benzoquinoline group. Substituents of rings A1 and A2 are more preferably alkyl groups, alkoxy groups, aromatic hydrocarbon ring groups, cyano groups, halogen atoms, or haloalkyl groups.

【0045】

M in equations (Va) and (Vb)⁴Or M⁵Preferred include ruthenium, rhodium, palladium, silver, rhenium, osmium, iridium, platinum or gold. M in equation (IV)⁷Preferable examples thereof include ruthenium, rhodium, palladium, silver, renium, osmium, iridium, platinum and gold, and particularly preferably divalent metals such as platinum and palladium.

【0046】

Specific examples of the organometallic complexes represented by the general formulas (Va) and (Vb) are shown below, but the present invention is not limited to the following compounds.

【0047】

[Chemical 26]

<img file="JP2002305083A_D0019.tif" />Specific examples of the organometallic complex represented by the general formula (IV) are shown below, but the present invention is not limited to the following compounds.

【0048】

[Chemical 27]

<img file="JP2002305083A_D0020.tif" />Hereinafter, the organic electroluminescent device of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a structural example of a general organic electroluminescent device used in the present invention, in which 1 is a substrate, 2 is an anode, 4 is a hole transport layer, 5 is a light emitting layer, and 6 is. The hole blocking layer, 8 represents the cathode, respectively.

【0049】

The substrate 1 serves as a support for an organic electroluminescent element, and a quartz or glass plate, a metal plate or metal leaf, a plastic film or a sheet or the like is used. In particular, a glass plate or a transparent synthetic resin plate such as polyester, polymethacrylate, polycarbonate, or polysulfone is preferable. When using a synthetic resin substrate, it is necessary to pay attention to the gas barrier property. If the gas barrier property of the substrate is too small, the organic electroluminescent element may be deteriorated by the outside air passing through the substrate, which is not preferable. Therefore, a method of providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate to ensure gas barrier properties is also one of the preferable methods.

【0050】

An anode 2 is provided on the substrate 1, and the anode 2 plays a role of injecting holes into the hole transport layer. The anode is usually a metal such as aluminum, gold, silver, nickel, palladium, platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide, carbon black, or poly. It is composed of conductive polymers such as (3-methylthiophene), polypyrrole, and polyaniline. The anode 2 is usually formed by a sputtering method, a vacuum vapor deposition method, or the like. In the case of metal fine particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, conductive polymer fine powder, etc., they are dispersed in an appropriate binder resin solution and placed on the substrate 1. The anode 2 can also be formed by applying to. Further, in the case of a conductive polymer, a thin film can be formed directly on the substrate 1 by electrolytic polymerization, or an anode 2 can be formed by applying a conductive polymer on the substrate 1 (Appl. Phys. Lett. , Volume 60, p. 2711, 1992). The anode 2 can also be formed by laminating different substances. The thickness of anode 2 depends on the transparency required. When transparency is required, it is desirable that the transmittance of visible light is usually 60% or more, preferably 80% or more, in which case the thickness is usually 5 to 1000 nm, preferably 10 to. It is about 500 nm. If opaque, the anode 2 may be the same as the substrate 1. Further, it is also possible to laminate different conductive materials on the above-mentioned anode 2.

【0051】

A hole transport layer 4 is provided on the anode 2. As a condition required for the material of the hole transport layer, it is necessary that the material has high hole injection efficiency from the anode and can efficiently transport the injected holes. For that purpose, the ionization potential is small, the transparency to visible light is high, the hole mobility is high, the stability is excellent, and impurities that become traps are unlikely to be generated during manufacturing or use. Required. Further, when it is provided in contact with the light emitting layer 5, it is required not to quench the light emitted from the light emitting layer or form an exciplex with the light emitting layer to reduce the efficiency. In addition to the above general requirements, the device is further required to have heat resistance when considering applications for in-vehicle display. Therefore, a material having a Tg value of 85 ° C or higher is desirable.

【0052】

Such hole transporting materials include, for example, two or more tertiary amines represented by 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl, and two or more. Aromatic having a starburst structure such as aromatic diamine (Japanese Patent Laid-Open No. 5-234681) in which the fused aromatic ring is replaced with a nitrogen atom, 4,4', 4 "-tris (1-naphthylphenylamino) triphenylamine, etc. Group amine compounds (J. Lumin., Vol. 72-74, pp. 985, 1997), aromatic amine compounds consisting of triphenylamine tetramers (Chem. Commun., P. 2175, 1996), 2,2 Spiro compounds such as',7,7'-tetrax- (diphenylamino) -9,9'-spirobifluorene (Synth. Metals, Vol. 91, p. 209, 1997) and the like. It may be used alone, or may be mixed and used as required.

【0053】

In addition to the above compounds, polyarylene ether sulfone (Polym. Adv. Tech.) Containing polyvinylcarbazole, polyvinyltriphenylamine (Japanese Patent Laid-Open No. 7-53953), and tetraphenylbenzidine as materials for the hole transport layer 4. , Volume 7, page 33, 1996). In the case of the coating method, one or more types of hole transporting materials and, if necessary, additives such as a binder resin and a coating property improving agent that do not trap holes are added and dissolved to prepare a coating solution. Then, it is applied onto the anode 2 by a method such as a spin coating method and dried to form the hole transport layer 4. Examples of the binder resin include polycarbonate, polyarylate, polyester and the like. A large amount of the binder resin reduces the hole mobility, so a small amount is desirable, and usually 50% by weight or less is preferable.

【0054】

In the case of the vacuum vapor deposition method, the hole transport material is placed in a crucible installed in the vacuum vessel, and the inside of the vacuum vessel is pumped with an appropriate vacuum pump.^-4After exhausting to about Pa, the crucible is heated to evaporate the hole transport material, and the hole transport layer 4 is formed on the substrate 1 on which the anode is formed, which is placed facing the crucible. The film thickness of the hole transport layer 4 is usually 5 to 300 nm, preferably 10 to 100 nm. In order to uniformly form such a thin film, a vacuum vapor deposition method is generally often used.

【0055】

A light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 contains an organic metal complex represented by the general formula (I) and an organic metal complex containing a metal selected from the above-mentioned groups 7 to 11 of the periodic table, and is an anode between the electrodes to which an electric field is applied. It is excited by the recombination of the holes injected from and moving through the hole transport layer and the electrons injected from the cathode and moving through the hole blocking layer 6, and exhibits strong light emission. The light emitting layer 5 may contain other components such as another host material (which functions in the same manner as the general formula (I)) as long as the performance of the present invention is not impaired.

【0056】

Further, the organic electroluminescent device of the present invention may contain a fluorescent dye as one of the subcomponents in the light emitting layer. The fluorescent dye referred to here is a fluorescent dye for laser such as xanthene. For example, the fluorescent dye that gives blue light emission includes perylene, pyrene, anthracene and derivatives thereof, and the green fluorescent dye includes a quinacridone derivative and coumarin. Examples of the yellow fluorescent dye such as a derivative include rubrene and a perimiden derivative, and examples of the red fluorescent dye include a coumarin derivative, a benzopyran derivative, a rhodamine derivative, a phenoxazone derivative, a benzothioxanthene derivative, and an azabenzothianthene.

【0057】

In addition to the above fluorescent dyes for doping, depending on the host material and organometallic complex, Laser Research, Vol. 8, p. 694, p. 803, p. 958 (1980); Vol. 9, p. 85 (1981), The fluorescent dyes listed in can be used as a dope material for the light emitting layer. The amount of the organometallic complex contained as an accessory component in the light emitting layer is preferably in the range of 0.1 to 30% by weight. If it is less than 0.1% by weight, it may not be possible to contribute to the improvement of the luminous efficiency of the device, and if it exceeds 30% by weight, concentration quenching may occur due to reasons such as the formation of dimers between organometallic complexes, which may lead to a decrease in luminous efficiency. There is sex. In a conventional device using fluorescence (singlet term), it tends to be preferable that the amount is slightly larger than the amount of the fluorescent dye (dopant) contained in the light emitting layer. When a known fluorescent dye is contained in the light emitting layer, the amount thereof is preferably 0.05 to 10% by weight, more preferably 0.05 to 2% by weight. These organometallic complexes and fluorescent dyes may be partially contained in the light emitting layer in the film thickness direction or may be unevenly distributed.

【0058】

The film thickness of the light emitting layer 5 is usually 10 to 200 nm, preferably 20 to 100 nm. A thin film is formed in the same manner as the hole transport layer 4. The hole blocking layer 6 is laminated on the light emitting layer 5 so as to be in contact with the interface on the cathode side of the light emitting layer 5, but prevents holes moving from the hole transport layer from reaching the cathode. It is formed of a role and a compound capable of efficiently transporting electrons injected from the cathode toward the light emitting layer. As the physical properties required for the material constituting the hole blocking layer, it is required that the electron mobility is high and the hole mobility is low. The hole blocking layer 6 has a function of confining holes and electrons in the light emitting layer to improve the luminous efficiency. As the hole blocking material satisfying such a condition, preferably, a mixed ligand complex represented by the following general formula (VII) can be mentioned.

【0059】

[Chemical 28]

<img file="JP2002305083A_D0021.tif" />(In the formula, R₂₄~ R₂₉Represents a hydrogen atom or any substituent. M⁸Represents a metal atom selected from aluminum, gallium, and indium. L³Is expressed by any of the following general formulas (VIIa), (VIIb), and (VIIc).

【0060】

[Chemical 29]

<img file="JP2002305083A_D0022.tif" />(During the ceremony, Ar¹¹~ Ar¹⁵Represents an aromatic hydrocarbon ring group which may have a substituent or an aromatic heterocyclic group which may have a substituent, and Z³Represents silicon or germanium. ) In the general formula (VII), R₂₄~ R₂₉Represents a hydrogen atom or any substituent, preferably a hydrogen atom; a halogen atom such as chlorine or bromine; an alkyl group having 1 to 6 carbon atoms such as a methyl group or an ethyl group; an aralkyl group such as a benzyl group; a vinyl group. Alkenyl group having 2 to 6 carbon atoms; cyano group; amino group; acyl group; alkoxy group having 1 to 6 carbon atoms such as methoxy group and ethoxy group; 2 to 6 carbon atoms such as methoxycarbonyl group and ethoxycarbonyl group Alkoxycarbonyl group; carboxyl group; aryloxy group such as phenoxy group and benzyloxy group; dialkylamino group such as diethylamino group and diisopropylamino group; dialalkylamino group such as dibenzylamino group and diphenethylamino group; trifluoro Α-Haloalkyl groups such as methyl groups; hydroxyl groups; aromatic hydrocarbon ring groups such as phenyl groups and naphthyl groups which may have substituents; thienyl groups and pyridyl groups which may have substituents, etc. Represents an aromatic heterocyclic group.

【0061】

Examples of the substituent that the aromatic hydrocarbon ring group and the aromatic heterocyclic group can have include a halogen atom such as a fluorine atom; an alkyl group having 1 to 6 carbon atoms such as a methyl group and an ethyl group; and a carbon such as a vinyl group. Alkenyl group of number 2 to 6; alkoxycarbonyl group having 2 to 6 carbon atoms such as methoxycarbonyl group and ethoxycarbonyl group; alkoxy group having 1 to 6 carbon atoms such as methoxy group and ethoxy group; phenoxy group, benzyloxy group, etc. Aryloxy group; dialkylamino group such as dimethylamino group and diethylamino group; acyl group such as acetyl group; haloalkyl group such as trifluoromethyl group; cyano group and the like. R₂₄~ R₂₉More preferably, a hydrogen atom, an alkyl group, a halogen atom or a cyano group can be mentioned. Also R₂₇The cyano group is particularly preferable.

【0062】

In the above equation (VII), Ar¹¹~ Ar¹⁵Specifically, it represents an aromatic hydrocarbon ring group such as a phenyl group, a biphenyl group or a naphthyl group which may have a substituent or an aromatic heterocyclic group such as a thienyl group or a pyridyl group. Preferred specific examples of the compound represented by the general formula (VII) are shown below, but the present invention is not limited thereto.

【0063】

[Chemical 30]

<img file="JP2002305083A_D0023.tif" />【0064】

[Chemical 31]

<img file="JP2002305083A_D0024.tif" />These compounds may be used alone in the hole blocking layer, or may be mixed and used as required. As the hole blocking material, in addition to the mixed ligand complex of the general formula (VII), a compound having at least one 1,2,4-triazole ring residue represented by the following structural formula can be used. it can.

【0065】

[Chemical 32]

<img file="JP2002305083A_D0025.tif" />Specific examples of the compound having at least one 1,2,4-triazole ring residue represented by the structural formula are shown below.

【0066】

[Chemical 33]

<img file="JP2002305083A_D0026.tif" />Further, examples of the hole blocking material include compounds having at least one phenanthroline ring represented by the following structural formula.

【0067】

[Chemical 34]

<img file="JP2002305083A_D0027.tif" />Specific examples of the compound having at least one phenanthroline ring represented by the structural formula are shown below.

【0068】

[Chemical 35]

<img file="JP2002305083A_D0028.tif" />The film thickness of the hole blocking layer 6 is usually 0.3 to 100 nm, preferably 0.5 to 50 nm. The hole blocking layer can also be formed in the same manner as the hole transporting layer, but a vacuum deposition method is usually used.

【0069】

The cathode 8 serves to inject electrons into the light emitting layer 5 via the hole blocking layer 6. As the material used as the cathode 8, the material used for the anode 2 can be used, but in order to efficiently inject electrons, a metal having a low work function is preferable, and tin, magnesium, indium, calcium, etc. Suitable metals such as aluminum and silver or alloys thereof are used. Specific examples include low work function alloy electrodes such as magnesium-silver alloys, magnesium-indium alloys, and aluminum-lithium alloys.

【0070】

At the interface on the light emitting layer side of the cathode, LiF and MgF₂, Li₂Inserting an ultra-thin insulating film (0.1 to 5 nm) such as O is also an effective method for improving the efficiency of the device (Appl. Phys. Lett., Vol. 70, p. 152, 1997; JP-A-10- No. 74586; IEEE Trans. Electron. Devices, Vol. 44, p. 1245, 1997). The film thickness of the cathode 8 is usually the same as that of the anode 2. For the purpose of protecting the cathode made of a low work function metal, it is preferable to further laminate a metal layer having a high work function and stable with respect to the atmosphere because it increases the stability of the device. Metals such as aluminum, silver, copper, nickel, chromium, gold and platinum are used for this purpose.

【0071】

For the purpose of further improving the luminous efficiency of the device, it is conceivable to provide an electron transport layer 7 between the hole blocking layer 6 and the cathode 8 (see FIG. 2). The electron transport layer 7 is formed of a compound capable of efficiently transporting electrons injected from the cathode between electrodes to which an electric field is applied in the direction of the hole blocking layer 6. The electron-transporting compound used in the electron-transporting layer 7 is a compound that has high electron-injection efficiency from the cathode 8 and has high electron mobility and can efficiently transport the injected electrons. is necessary.

【0072】

Materials that satisfy these conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (Japanese Patent Laid-Open No. 59-194393), metal complexes of 10-hydroxybenzo [h] quinoline, oxadiazole derivatives, and di. Styrylbiphenyl derivative, silol derivative, 3- or 5-hydroxyflavon metal complex, benzoxazole metal complex, benzothiazole metal complex, trisbenzimidazolylbenzene (US Patent No. 5,645,948), quinoline compound (Japanese Patent Laid-Open No. 6-207169) , Phenantroline derivative (Japanese Patent Laid-Open No. 5-331459), 2-t-butyl-9,10-N, N'-dicyanoanthraquinone diimine, n-type hydride amorphous silicon carbide, n-type zinc sulfide, n-type Examples include zinc selenium. In addition, electron transport with enhanced electron transport capability by doping a phenanthroline derivative or metal complex with an alkali metal, or doping an organic substance having a high electron transport property and a small molecular weight such as an oxadiazole derivative, a quinoxaline compound, or a phenanthroline derivative. Layers can also be formed. The film thickness of the electron transport layer 6 is usually 5 to 200 nm, preferably 10 to 100 nm.

【0073】

The electron transport layer 7 is formed by laminating on the hole blocking layer 6 by a coating method or a vacuum vapor deposition method in the same manner as the hole transport layer 4. Usually, a vacuum deposition method is used. An anode buffer layer 3 is also inserted between the hole transport layer 4 and the anode 2 for the purpose of further improving the efficiency of hole injection and improving the adhesion of the entire organic layer to the anode. (See Figure 3). By inserting the anode buffer layer 3, the drive voltage of the initial element is lowered, and at the same time, the voltage rise when the device is continuously driven at a constant current is also suppressed. The conditions required for the material used for the anode buffer layer are that it can form a uniform thin film with good contact with the anode and is thermally stable, that is, it has a high melting point and glass transition temperature, and the melting point is 300 ° C or higher. , The glass transition temperature is required to be 100 ° C or higher. Further, the ionization potential is low, holes can be easily injected from the anode, and the hole mobility is high.

【0074】

For this purpose, tarocyanine compounds such as copper phthalocyanine (Japanese Patent Laid-Open No. 63-295695), polyaniline (Appl. Phys. Lett., Vol. 64, p. 1245, 1994), polythiophene (Optical Materials, 1994). Organic compounds such as Vol. 9, p. 125, 1998), spatter-carbon films (Synth. Met., Vol. 91, p. 73, 1997), and metals such as vanadium oxide, ruthenium oxide, and molybdenum oxide. Oxides (J. Phys. D, Vol. 29, p. 2750, 1996) have been reported. It is also possible to facilitate hole injection by doping an aromatic diamine-containing polyether with an electron-accepting group such as DDQ.

【0075】

In the case of the anode buffer layer, a thin film can be formed in the same manner as the hole transport layer, but in the case of an inorganic substance, a sputtering method, an electron beam deposition method, or a plasma CVD method is further used. The film thickness of the anode buffer layer 3 formed as described above is usually 3 to 100 nm, preferably 5 to 50 nm.

【0076】

It should be noted that the structure opposite to that of FIG. 1, that is, the cathode 8, the hole blocking layer 6, the light emitting layer 5, the hole transport layer 4, and the anode 2 can be laminated in this order on the substrate, as described above. It is also possible to provide the organic electroluminescent device of the present invention between two substrates having at least one highly transparent substrate. Similarly, it is also possible to stack the layers in a structure opposite to that of the respective layer configurations shown in FIGS. 2 and 3.

【0077】

The present invention can be applied to any of a single element, an element having a structure arranged in an array, and a structure in which an anode and a cathode are arranged in an XY matrix. According to the organic electroluminescent device of the present invention, by incorporating a compound having a specific skeleton in the light emitting layer and a phosphorescent metal complex, an device having high luminous efficiency and greatly improved drive stability can be obtained. Therefore, it can exhibit excellent performance in application to full-color or multi-color panels.

【0078】

[Example]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to the description of the following examples as long as the gist of the present invention is not exceeded. Example 1 An organic electroluminescent device having the structure shown in FIG. 3 was manufactured by the following method.

【0079】

Indium tin oxide (ITO) transparent conductive film deposited at 150 nm on a glass substrate (manufactured by Geomatec; electron beam film formed; sheet resistance 15 Ω) with a width of 2 mm using ordinary photolithography technology and hydrochloric acid etching. The anode 2 was formed by patterning the stripes. The patterned ITO substrate is cleaned in the order of ultrasonic cleaning with acetone, water washing with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally UV ozone cleaning is performed in the vacuum vapor deposition apparatus. installed. After the rough exhaust of the above device is performed by the oil rotary pump, the degree of vacuum inside the device is 2x10.^-6Torr (about 2,7x10)^-4Pa) Exhausted using an oil diffusion pump equipped with a liquid nitrogen trap until the following was achieved. As a material for the anode buffer layer 3, copper phthalocyanine (HI-1) having the structural formula shown below [0080] [0080]

[Chemical 36]

<img file="JP2002305083A_D0029.tif" />Was formed on the anode 2 with a film thickness of 10 nm at a vapor deposition rate of 0.1 nm / sec and a vacuum degree of 1.0x10-6 Torr (about 1.3x10-4 Pa) using a molybdenum boat. The 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl shown below was placed in a ceramic crucible placed in the above device. [0081]

[Chemical 37]

<img file="JP2002305083A_D0030.tif" />The tantalum wire heater around the crucible was used to heat the crucible for vapor deposition. The temperature of the crucible at this time was controlled in the range of 240 to 260 ° C. Vacuum degree 0.8x10 during vapor deposition^-6Torr (about 1.1x10)^-4Pa), a hole transport layer 4 having a film thickness of 60 nm was obtained at a vapor deposition rate of 0.2 nm / sec. Subsequently, the example compound (H-4) was placed as the main component of the light emitting layer 5, and the iridium complex shown by (T-2) in the text was placed as a phosphorescent organometallic complex as a sub-component in separate ceramic crucibles. The film was formed by the two-way simultaneous vapor deposition method. The crucible temperature of compound (H-4) is controlled to 350 ° C, the deposition rate is controlled to 0.2 nm / sec, and the temperature range of iridium complex (T-2) is controlled to 290 to 300 ° C, with a film thickness of 30 nm. A light emitting layer 5 containing 5% by weight of the iridium complex (T-2) was laminated on the hole transport layer 4. The degree of vacuum during vapor deposition is 1.0x10^-6Torr (about 1.3x10)^-4It was Pa).

【0082】

Further, as the hole blocking layer 6, the example compound (HB-12) was laminated with a crucible temperature of 240 ° C. and a film thickness of 10 nm at a vapor deposition rate of 0.1 nm / sec. The degree of vacuum during vapor deposition is 0.7x10^-6Torr (about 0.9x10)^-4It was Pa). On the hole blocking layer 6, the 8-hydroxyquinoline complex of aluminum represented by the following structural formula (ET-1), Al (C), is used as the electron transport layer 7.₉H₆NO)₃ 【0083】

[Chemical 38]

<img file="JP2002305083A_D0031.tif" />Was deposited in the same manner. At this time, the crucible temperature of the 8-hydroxyquinoline complex of aluminum is controlled in the range of 270 to 290 ° C, and the degree of vacuum during vapor deposition is 0.7x10.^-6Torr (about 0.9x10)^-4Pa), the vapor deposition rate was 0.2 nm / sec, and the film thickness was 35 nm.

【0084】

The substrate temperature at the time of vacuum-depositing the hole transport layer, the light emitting layer, the hole blocking layer and the electron transport layer was maintained at room temperature. Here, the element that has been vapor-deposited up to the electron transport layer 7 is once taken out into the atmosphere from the vacuum vapor deposition apparatus, and a 2 mm wide striped shadow mask is used as a mask for cathode vapor deposition. What is the ITO stripe of the anode 2? It is closely attached to the element so that it is orthogonal to each other, and it is installed in another vacuum deposition apparatus, and the degree of vacuum in the apparatus is 2x10 in the same way as the organic layer.^-6Torr (about 2.7x10)^-4Pa) Exhausted until it became less than or equal to. As the cathode 8, first, magnesium fluoride (MgF)₂) Using a molybdenum boat, vapor deposition rate 0.1 nm / sec, vacuum degree 7.0x10^-⁶Torr (about 9.3x10)^-4In Pa), a film was formed on the electron transport layer 7 with a film thickness of 1.5 nm. Next, the aluminum is similarly heated by a molybdenum boat, and the deposition rate is 0.5 nm / sec and the degree of vacuum is 1x10.^-5Torr (about 1.3x10)^-3An aluminum layer having a film thickness of 40 nm was formed in Pa). Furthermore, on top of that, silver is similarly heated by a molybdenum boat to increase the conductivity of the cathode, with a deposition rate of 0.3 nm / sec and a degree of vacuum of 1x10.^-5Torr (about 1.3x10)^-3A silver layer having a film thickness of 40 nm was formed in Pa) to complete the cathode 8. The substrate temperature at the time of vapor deposition of the above three-layer cathode 8 was maintained at room temperature.

【0085】

As described above, an organic electroluminescent device having a light emitting area portion having a size of 2 mm x 2 mm was obtained. Table 1 shows the light emission characteristics of this device. In Table-1, the luminous efficiency is 100 cd / m.²The value at, the brightness / current is the slope of the brightness-current density characteristic, and the voltage is 100 cd / m.²The values in are shown respectively. The maximum wavelength of the emission spectrum of the device was 518 nm, which was identified as being from the iridium complex (T-2).

【0086】

After sealing this device, it was stored in an environment of 85 ° C for 500 hours. Even after storage for 500 hours, less than 1% of the non-light emitting part was practically usable as an element. Comparative example 1 An element was produced in the same manner as in Example 1 except that (H-4), which is the main component of the light emitting layer, was replaced with (H-1). Table 1 shows the light emission characteristics of this device. The maximum wavelength of the emission spectrum of the device was 512 nm, which was almost the same as in Example 1, and it was identified as being from the iridium complex (T-2). The luminous efficiency is low and the drive voltage is high as compared with Example 1.

【0087】

Example 2 The device was produced in the same manner as in Example 1 except that the main component of the light emitting layer was replaced with (H-12) and the subcomponent was replaced with a platinum complex (T-8). Table 1 shows the light emission characteristics of this device. The maximum wavelengths of the emission spectrum of the device were 588 nm and 637 nm, which were identified as from the platinum complex (T-8).

【0088】

Comparative example 2 An element was produced in the same manner as in Example 2 except that (H-12), which is the main component of the light emitting layer, was replaced with (H-1). Table 1 shows the light emission characteristics of this device. The maximum wavelengths of the emission spectrum of the device were 585 nm and 634 nm, which were almost the same as in Example 3, and were identified as being from the platinum complex (T-8). Compared with Example 2, the drive voltage is high and the luminous efficiency is low.

【0089】

Example 3 An element was produced in the same manner as in Example 2 except that the subcomponent of the light emitting layer was replaced with a platinum complex (T-1). Table 1 shows the light emission characteristics of this device. The emission spectrum of the device showed a sharp peak with a maximum wavelength of 651 nm and was identified as from the platinum complex (T-1).

【0090】

Comparative example 3 The device was manufactured in the same manner as in Example 3 except that (H-12), which is the main component of the light emitting layer, was replaced with (ET-1), which was used as the electron transport layer in Example 1. Table 1 shows the light emission characteristics of this device. The maximum wavelength of the emission spectrum of the device was 651 nm, which was the same as in Example 3, and it was identified as being from the platinum complex (T-1). Luminous efficiency is low as compared with Example 3.

【0091】

[table 1]

<img file="JP2002305083A_D0032.tif" />【0092】

[Effect of the invention]

According to the light emitting layer of the organic electroluminescent device of the present invention, it is possible to emit light with high brightness and high efficiency at a low voltage, and further, the stability of the device is improved. Therefore, the organic electroluminescent element according to the present invention is a flat panel display (for example, for an OA computer or a wall-mounted television), an in-vehicle display element, a light source utilizing the characteristics of a mobile phone display or a surface illuminant (for example, a light source of a copying machine). It can be applied to liquid crystal displays and backlit light sources of instruments), display boards, and indicator lights, and its technical value is great.

[Simple explanation of drawings]

[Figure 1]

Schematic cross-sectional view showing an example of an organic electroluminescent device.

[Figure 2]

Schematic cross-sectional view showing another example of an organic electroluminescent device.

[Fig. 3]

Schematic cross-sectional view showing another example of an organic electroluminescent device.

[Explanation of symbols]

1 board 2 Anode 3 Anode buffer layer 4 hole transport layer 5 light emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Cathode