JPH11312586A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance blue purity, increase heat resistance, and keep stable blue luminescent characteristics for a long time by including an aromatic diamine compound a luminescent layer. SOLUTION: The luminescent layer of a luminescent element contains a compound represented by the formula. In the formula, Ar<1> and Ar<2> each represents an aromatic hydrocarbon group or an aromatic heterocyclic group which may be independent and have a substitutional group. R<1> to R<18> represent an alkyl group, an aralkyl group, an alkenyl group, an amine group, an amide group, an alkoxy carbonyl group, an alkoxy group, which may independently have a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, or a substitutional group, an aromatic hydrocarbon group which may have a substitutional group, or an aromatic heterocyclic group which may have a substitutional group. X represents divalent aromatic ring residue, which may have a substitutional group, and is preferably selected from among a phenylene group, biphenylene group, or a terphenylene group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an organic electroluminescent device. More specifically, the present invention relates to an organic electroluminescent device having a light emitting layer containing a specific aromatic diamine. The organic electroluminescent device of the present invention can achieve blue light emission with good color purity and improved stability.
It is expected to be applied to a display, a multi-color display element, or a light source utilizing the features of a surface light emitter.

[0002]

2. Description of the Related Art Conventionally, as a thin film type electroluminescent (EL) element, Zn, which is a group II-VI compound semiconductor of an inorganic material, is used.
In general, S, CaS, SrS, and the like are doped with Mn or a rare earth element (Eu, Ce, Tb, Sm, or the like) which is a luminescence center. However, EL devices manufactured from the above inorganic materials include: 1) AC drive is required (50-1000 Hz), 2) High drive voltage (up to 200 V), 3) It is difficult to achieve full color (especially blue), 4) Cost of peripheral drive circuit is high. ing.

However, in recent years, in order to improve the above problems,
Development of EL devices using organic thin films has been started. In particular, the electrode type was optimized for the purpose of improving the efficiency of carrier injection from the electrode in order to increase the luminous efficiency, and the hole transport layer composed of an aromatic diamine and the luminescent layer composed of an aluminum complex of 8-hydroxyquinoline were used. Of an organic electroluminescent device provided (Appl. Phys. Let
t. , Vol. 51, p. 913, 1987), the luminous efficiency is greatly improved as compared with a conventional electroluminescent device using a single crystal such as anthracene or the like, and the practical characteristics are approached. Further, for example, doping a fluorescent dye for laser such as coumarin using an aluminum complex of 8-hydroxyquinoline as a host material (J. Appl. Phys.
s. , 65, 3610, 1989), improvement of luminous efficiency, conversion of luminous wavelength, and the like are also performed. In addition to the electroluminescent device using a low molecular material as described above, poly (p-phenylenevinylene) (Na
cure, 347, 539, 1990 et al.), poly [2-methoxy-5- (2-ethylhexyloxy)-
1,4-phenylenevinylene] (Appl. Phys.
Lett. 58, 1982, 1991, etc.),
Poly (3-alkylthiophene) (Jpn. J. App
l. Phys, 30, L1938, 1991
Development of an electroluminescent device using a polymer material such as E.C. and others, and a device in which a low molecular light emitting material and an electron transfer material are mixed with a polymer such as polyvinyl carbazole (Applied Physics, Vol. 61, 10
44, 1992).

[0004]

In order to apply an organic electroluminescent device to a display device such as a flat panel display, it is necessary to ensure sufficient reliability of the device. However, the heat resistance of the conventional organic electroluminescent device is insufficient, and the current-voltage characteristic shifts to a higher voltage side due to an increase in the ambient temperature or process temperature of the device, or local Joule heat generated when the device is driven. Deterioration such as shortening of service life and generation and increase of non-light emitting portions (dark spots) was inevitable. In particular, regarding the blue light emitting element, 8-
At present, the stability of the device is inferior to that of a green light-emitting device using an aluminum complex of hydroxyquinoline. The main cause of the above device deterioration is deterioration of the thin film shape of the organic layer. It is considered that the deterioration of the thin film shape is caused by crystallization (or aggregation) of the organic amorphous thin film due to heat generated during driving of the element. This low heat resistance is considered to be due to the low glass transition temperature (hereinafter abbreviated as Tg) of the material. Tg generally has a linear correlation with the melting point.
Many of the compounds used for the light emitting layer of the blue light emitting element have a low molecular weight and a low melting point and low Tg because of the restriction that pi electron conjugation cannot be expanded. At present, it is not sufficiently stable chemically.

[0005] Compounds used in blue organic electroluminescent devices include anthracene (Jpn. J. Ap.).
pl. Phys. 27, L269, 1988.
Year), tetraphenylbutadiene, pentaphenylcyclopentadiene (Appl. Phys., Lett.,
56, 799, 1990), distyrylbenzene derivative (Journal of the Chemical Society of Japan, p. 1162, 1992), oxadiazole derivative (Jpn. J. Appl. Phy.
s. , 31, 1812, 1992; Journal of the Chemical Society of Japan, 1540, 1991), azomethine zinc complex (Jpn. J. Appl. Phys., 32, L51).
1, 1993), a benzazole metal complex (JP-A-8-81472), a mixed-ligand aluminum complex (JP-A-5-198377; JP-A-5-1983).
JP-A-78-214; JP-A-5-214332; JP-A-6-214332
-172751), N, N'-diphenyl-N,
N '-(3-methylphenyl) -1,1'-biphenyl-4,4'-diamine (Jpn. J. Appl. Phys.
s. 32, L917, 1993), polyvinyl carbazole (Appl. Phys. Lett., 63).
Vol., P. 2627, 1993), 1,2,4-triazole derivatives (Chem. Lett., P. 47, 1996).
Year), aminopyrene dimer (Jpn.J. Appl.P
hys. , 35, 4819, 1996), distyrylbiphenyl derivatives (Applied Physics, 62, 1015).
1993; Appl. Phys. Lett. , 6
7, 3853, 1995), silole derivatives (J. Am. Chem. Soc., 118, 1197).
4, p. 1996). Among the blue light-emitting materials described above, typical compounds whose device characteristics are well studied are shown below.

[0006]

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[0007]

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[0008]

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Distyrilbiphenyl derivative (B-1)
Has a high fluorescence intensity and does not form an exciplex even when used in a device, and emits blue light.
l. Phys. Lett. , 67, 3853, 19
1995), ionization potential in thin film state is 5.9
Because of its high eV, it is difficult to inject holes from the hole transport layer. In addition, the EL spectrum shows a broad peak having a light emission maximum near 480 nm, and the blue color purity is poor. This color purity is not improved by doping. Bis (2-methyl-8-quinolinolato) (p-phenylferrite) aluminum complex (B
-2), the color purity of blue is also insufficient. Although the color purity is improved by doping with perylene, the stability at the time of driving does not reach a practical level (Japanese Patent Laid-Open No. 5-198377).
No.). N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-biphenyl-4,4'-diamine which is an aromatic diamine (commonly called TPD)
Shows an EL spectrum having an emission peak at 464 nm when combined with a triazole derivative layer as a hole blocking layer (Jpn. J. Appl. Phys., 3).
2, L917, 1993), and the Tg of TPD is 63.
Due to its low temperature of ℃, it has thermal instability such as crystallization. From the high temperature characteristics of display elements for use in vehicles, a value of Tg of 85 ° C. or higher is required. For the above-mentioned reason, the blue organic electroluminescent device has a problem of color purity of light emission and a serious problem in heat resistance and driving life of the device for practical use. The fact that the blue purity of the organic electroluminescent device is not improved and the heat resistance and the driving characteristics are unstable are undesirable characteristics as a display device such as a full-color flat panel display. An object of the present invention is to provide an organic electroluminescent device having high blue purity, heat resistance, and capable of maintaining stable blue light emitting characteristics for a long period of time.

[0010]

Means for Solving the Problems The inventors of the present invention have made intensive studies in view of the above situation, and as a result, have found that the use of a light emitting layer containing a specific aromatic diamine compound having a blue fluorescence and a high Tg has been proposed. The present inventors have found that the above problems can be solved, and have completed the present invention.

That is, the gist of the present invention is an organic electroluminescent device including at least a hole transporting layer, a light emitting layer and an electron transporting layer sandwiched between an anode and a cathode on a substrate. An organic electroluminescent device comprising a compound represented by the formula (I),

[0012]

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[0013] (wherein, Ar ¹ and Ar ² are independently each may have a substituent group, an aromatic hydrocarbon group or an aromatic heterocyclic group, to no R ¹ R ¹⁸ is Each independently a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, or an alkyl group, an aralkyl group, an alkenyl group, an amino group, an amide group, an alkoxycarbonyl group, and an alkoxy group, each of which may have a substituent. A group, an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent, and X represents a divalent aromatic group which may have a substituent Group ring residue).

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an organic electroluminescent device of the present invention using the above general formula (I) will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing an example of the structure of a general organic electroluminescent device used in the present invention, wherein 1 is a substrate, 2 is an anode, 4 is a hole transport layer, 5 is a light emitting layer, and 7 is The electron transport layer 8 represents a cathode. The substrate 1 serves as a support for the organic electroluminescent device, and is made of a quartz or glass plate,
A metal plate, a metal foil, a plastic film, a sheet, or the like is used. Particularly, a glass plate or a plate of a transparent synthetic resin such as polyester, polymethacrylate, polycarbonate, and polysulfone is preferable. When using a synthetic resin substrate, it is necessary to pay attention to gas barrier properties. If the gas barrier property of the substrate is too low, the organic air-emitting device may be deteriorated by outside air passing through the substrate, which is not preferable. Therefore, a method of providing a dense silicon oxide film or the like on one or both sides of the synthetic resin substrate to secure gas barrier properties is also one of the preferable methods.

An anode 2 is provided on a substrate 1, and the anode 2 plays a role of injecting holes into a hole transport layer 4. This anode is usually made of a metal such as aluminum, gold, silver, nickel, palladium and platinum, a metal oxide such as an oxide of indium and / or tin, a metal halide such as copper iodide, carbon black, or poly. (3-methylthiophene), conductive polymers such as polypyrrole and polyaniline. Usually, the formation of the anode 2 is often performed by a sputtering method, a vacuum evaporation method, or the like.
In the case of fine particles of metal such as silver, fine particles of copper iodide or the like, carbon black, fine particles of a conductive metal oxide, fine particles of a conductive polymer, or the like, they are dispersed in an appropriate binder resin solution and To form the anode 2. Further, in the case of a conductive polymer, a thin film can be formed directly on the substrate 1 by electrolytic polymerization, or the conductive polymer can be applied on the substrate 1 to form the anode 2 (Ap).
pl. Phys. Lett. 60, 2711, 1
992). The anode 2 can be formed by laminating different materials. The thickness of the anode 2 depends on the required transparency. When transparency is required, it is desirable that the visible light transmittance is usually 60% or more, preferably 80% or more. In this case, the thickness is usually 5 to 10%.
00 nm, preferably about 10 to 500 nm. If opaque, the anode 2 may be the same as the substrate 1. Further, it is also possible to laminate a different conductive material on the anode 2.

On the anode 2, a hole transport layer 4 is provided. As a condition required for the material of the hole transport layer, it is necessary that the material has a high hole injection efficiency from the anode and can efficiently transport the injected holes. Therefore, the ionization potential is small, the transparency to visible light is high, the hole mobility is large, the stability is further improved, and impurities serving as traps are hardly generated at the time of manufacture or use. Required. In addition to the above general requirements, when considering applications for in-vehicle display, the element is required to have further heat resistance. Therefore, Tg is 85
A material having a value of at least C is desirable.

As such a hole transporting material, for example, aromatic diamine compounds linked with tertiary aromatic amine units such as 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane (particularly, Kaisho 59-194393
Publication), 4,4'-bis [N- (1-naphthyl) -N
[Phenylamino] biphenyl, aromatic amines containing two or more tertiary amines and two or more condensed aromatic rings substituted with nitrogen atoms (JP-A-5-234681); Aromatic triamines having a starburst structure in derivatives (US Pat. No. 4,92
3,744), N, N'-diphenyl-N,
N'-bis (3-methylphenyl) biphenyl-4,
Aromatic diamines such as 4'-diamine (U.S. Pat.
No. 64,625), a triphenylamine derivative which is sterically asymmetric as a whole molecule (JP-A-4-12927).
No. 1), a compound in which a pyrenyl group is substituted with a plurality of aromatic diamino groups (JP-A-4-175395), and an aromatic diamine in which a tertiary aromatic amine unit is linked by an ethylene group (JP-A-4-264189). Japanese Patent Application Laid-Open No. 4-290466), aromatic diamines having a styryl structure (Japanese Patent Application Laid-Open No. Hei 4-290851), those obtained by linking aromatic tertiary amine units with thiophene groups (Japanese Patent Application Laid-Open No. 4-304466), starburst type aromatics Triamines (JP-A-4-308688) and benzylphenyl compounds (JP-A-4-36415)
No. 3), a compound in which a tertiary amine is linked by a fluorene group (Japanese Patent Application Laid-Open No. 5-25473), a triamine compound (Japanese Patent Application Laid-Open No. 5-239455), and a bisdipyridylaminobiphenyl (Japanese Patent Application Laid-Open No. 5-320634). ),
N, N, N-triphenylamine derivatives (Japanese Unexamined Patent Publication No.
No. 972), aromatic diamines having a phenoxazine structure (JP-A-7-138562), diaminophenylphenanthridine derivatives (JP-A-7-25247).
No. 4), silazane compounds (US Pat. No. 4,950,
950), silanamine derivatives (JP-A-6-49)
079), phosphamine derivatives (JP-A-6-25)
659) and quinacridone compounds.
These compounds may be used alone, or may be used as a mixture as necessary.

In addition to the above compounds, polyvinyl carbazole and polysilane (App
l. Phys. Lett. 59, 2760, 19
1991), polyphosphazene (JP-A-5-31094)
No. 9), polyamide (JP-A-5-310949), polyvinyl triphenylamine (JP-A-7-53).
No. 953), a polymer having a triphenylamine skeleton (Japanese Patent Laid-Open No. 4-133065), and a polymer in which triphenylamine units are linked by a methylene group (Synth
etic Metals, 55-57, 4163,
1993), polymethacrylates containing aromatic amines (J. Polym. Sci., Polym. Che.
m. Ed. , 21, 969, 1983).

The hole transport layer 4 is formed by laminating on the anode 2 by a coating method or a vacuum evaporation method. In the case of the coating method, one or more hole transport materials and, if necessary, an additive such as a binder resin or a coating property improving agent which does not trap holes are added and dissolved to prepare a coating solution. Is applied on the anode 2 by a method such as spin coating, and dried to form the hole transport layer 4. Examples of the binder resin include polycarbonate, polyarylate, and polyester. If the amount of the binder resin is large, the hole mobility is lowered, so that a smaller amount is preferable.
Usually, 50% by weight or less is preferable.

In the case of the vacuum vapor deposition method, the hole transporting material is put into a crucible placed in a vacuum vessel, evacuated to 10 ^-6 Torr by a suitable vacuum pump in the vacuum vessel, and then the crucible is heated. Then, the hole transporting material is evaporated to form the hole transporting layer 4 on the anode 2 on the substrate 1 placed facing the crucible. The thickness of the hole transport layer 4 is usually 10 to 300 n.
m, preferably 30 to 100 nm. In order to uniformly form such a thin film, generally, a vacuum deposition method is often used.

In order to improve the contact between the anode 2 and the hole transport layer 4, it is conceivable to provide an anode buffer layer 3 as shown in FIG. The conditions required for the material used for the anode buffer layer are that a uniform thin film can be formed with good contact with the anode and thermally stable, that is, the melting point and the glass transition temperature are high, and the melting point is 300 ° C. or more, A glass transition temperature of 100 ° C. or higher is required. In addition, the ionization potential is low, holes can be easily injected from the anode, and the hole mobility is high. To this end, porphyrin derivatives and phthalocyanine compounds (JP-A-63-29569) and star-burst-type aromatic triamines (JP-A-Hei.
308688), hydrazone compounds (Japanese Unexamined Patent Publication No.
No. 320483), an alkoxy-substituted aromatic diamine derivative (Japanese Patent Application Laid-Open No. 4-220995), p- (9
-Anthryl) -N, N-di-p-tolylaniline (JP-A-3-111485), polythienylenevinylene and poly-p-phenylenevinylene (JP-A-4-145)
192), polyaniline (Appl. Phys.
Lett. 64, p. 1245, 1994), and sputtered carbon films (JP-A-8-3).
No. 1573) and metal oxides such as vanadium oxide, ruthenium oxide, and molybdenum oxide (the 43rd Alliance Lecture Meeting on Applied Physics, 27a-SY-9, 1996)
Year) has been reported.

Examples of the compound often used as the material of the anode buffer layer include a porphyrin compound and a phthalocyanine compound. These compounds may have a central metal or may be non-metallic. Specific examples of preferred such compounds include the following compounds: porphine 5,10,15,20-tetraphenyl-21H, 23
H-porphine 5,10,15,20-tetraphenyl-21H, 23
H-porphine cobalt (II) 5,10,15,20-tetraphenyl-21H, 23
H-porphine copper (II) 5,10,15,20-tetraphenyl-21H, 23
H-porphine zinc (II) 5,10,15,20-tetraphenyl-21H, 23
H-porphine vanadium (IV) oxide 5,10,15,20-tetra (4-pyridyl) -21
H, 23H-porphine 29H, 31H-phthalocyanine copper (II) phthalocyanine zinc (II) phthalocyanine titanium phthalocyanine oxide magnesium phthalocyanine lead phthalocyanine copper (II) 4,4 ′, 4 ″, 4 ″ ″-tetraaza-2
In the case of the 9H, 31H-phthalocyanine anode buffer layer, a thin film can be formed in the same manner as the hole transport layer. However, in the case of an inorganic substance, a sputtering method, an electron beam evaporation method, or a plasma CVD method is used. The thickness of the anode buffer layer 3 formed as described above is usually 3 to 100 nm, preferably 10 to 50 nm.
It is.

The light emitting layer 5 is provided on the hole transport layer 4. In the present invention, the light-emitting layer 5 includes, between the electrodes to which an electric field is applied, holes injected from the anode 2 and transported through the hole transport layer, and holes injected from the cathode 8 and the electron transport layer 7.
Is formed from a compound that emits blue light by efficiently recombining electrons transported through the compound. Therefore, it is a compound that has both hole transporting properties and electron transporting properties, has high hole mobility and electron mobility, and has excellent stability and is less likely to generate impurities that become traps during production or use. Is required. Further, in order to enable blue light emission, the fluorescence wavelength in a thin film state is 400 to 500.
It needs to be in the range of nm. In the present invention, the light emitting layer 5 of the organic electroluminescent device is provided with the above-mentioned general formula (I)
By containing the compound represented by the formula, stable blue light emission characteristics and improved heat resistance can be brought about.

The organic electroluminescent device according to the present invention is characterized in that the luminescent material comprises one selected from the compounds represented by the above general formula (I) or a mixture of two or more compounds. In the general formula (I), preferably, Ar ¹ and Ar ² are each independently a phenyl group, a naphthyl group, an anthryl group, a biphenyl group, a pyridyl group or a thienyl, each of which may have a substituent. A halogen atom; an alkyl group having 1 to 6 carbon atoms such as a methyl group and an ethyl group; an alkenyl group such as a vinyl group; an alkoxy group having 1 to 6 carbon atoms such as a methoxy group and an ethoxy group. An alkoxycarbonyl group having 1 to 6 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group; an aryloxy group such as a phenoxy group and a benzyloxy group; a dialkylamino group such as a diethylamino group and a diisopropylamino group; a dibenzylamino group; And a diaralkylamino group such as a diphenethylamino group. Particularly preferably, it is selected from a phenyl group and a naphthyl group, each of which may have a substituent. R ¹ to R ¹⁸ are preferably each independently a hydrogen atom; a halogen atom; a hydroxyl group; an alkyl group having 1 to 6 carbon atoms such as a methyl group and an ethyl group; an α-haloalkyl group; An aromatic hydrocarbon group such as a phenyl group and a biphenyl group; an alkoxycarbonyl group having 1 to 6 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group; an alkoxy group having 1 to 6 carbon atoms such as a methoxy group and an ethoxy group; An aryloxy group such as a benzyloxy group; a dialkylamino group such as a diethylamino group or a diisopropylamino group; a dibenzylamino group;
A diarylamino group such as a diphenylamino group, and a saturated or unsaturated aliphatic hydrocarbon group, aromatic hydrocarbon group, alkoxy group, aryloxy group, dialkylamino group, diarylamino group has a substituent. Is also good. Particularly preferably, it has 1 carbon atom such as a methyl group or an ethyl group.
And C6 to C6 alkoxy groups such as methoxy and ethoxy groups, and aromatic hydrocarbon groups such as phenyl and biphenyl groups. X is preferably selected from a phenylene group, a biphenylene group, a terphenylene group, an anthrylene group, a thienylene group, and a naphthylene group, each of which may have a substituent. Particularly preferably,
It is selected from a phenylene group, a biphenylene group and a terphenylene group. The compound represented by the general formula (I) is, for example, a diamine derivative represented by the following general formula (VI):

[0025]

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An iodine compound represented by the following general formula (VII)

[0027]

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The Ullmann (Ollmann) reaction (O
rgnic Synthesis, 1, 544)
The resulting monosubstituted compound represented by the following general formula (VIII)

[0029]

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After separation by column chromatography,
Similarly to the iodine form represented by the following general formula (IX),

[0031]

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The aromatic amine compound represented by the general formula (I) is obtained by Ullmann reaction. In the present invention, Tg is 1 according to the molecular structure represented by the general formula (I).
The temperature can be as high as 00 ° C. or higher, and the improved heat resistance can provide an amorphous thin film that is not easily crystallized, and the mutual interaction of molecules between the hole transport layer, the electron transport layer, and the like can be provided. Diffusion can be sufficiently suppressed even at a high temperature of 100 ° C. or higher. Preferred specific examples of the derivative represented by the general formula (I) are shown in Tables 1 to 13, but are not limited thereto. In the table, with respect to R ¹ to R ¹⁸ , when a substituent is not particularly indicated, a hydrogen atom is substituted.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

[0037]

[Table 5]

[0038]

[Table 6]

[0039]

[Table 7]

[0040]

[Table 8]

[0041]

[Table 9]

[0042]

[Table 10]

[0043]

[Table 11]

[0044]

[Table 12]

[0045]

[Table 13]

The light emitting layer 5 of the general formula (I) is formed by laminating on the hole transport layer 4 by a coating method or a vacuum evaporation method in the same manner as the hole transport layer 4. However, in the case of the coating method, it is necessary to use a solvent that does not dissolve the hole transport layer already formed as a thin film. Light emitting layer 5
Is usually 5 to 300 nm, preferably 10 to 1 nm.
00 nm. In order to uniformly form such a thin film, generally, a vacuum deposition method is often used.

In order to improve the luminous efficiency of blue light and the color purity at the same time, and further to improve the driving life of the device,
Doping a fluorescent dye using the light emitting layer material as a host material is an effective method. As doped dyes having blue fluorescence, condensed polycyclic aromatic rings such as perylene (Japanese Patent Laid-Open No. 5-198377), coumarin derivatives, naphthalic imide derivatives (Japanese Patent Laid-Open No. 4-320486), aromatic amine derivatives ( JP-A-8-199162). The content of these doped dyes in the host material is preferably in the range of 0.1 to 10% by weight. Of course, it is also possible to dope a green fluorescent dye or a red fluorescent dye in order to obtain green or red light emission.
As a method of performing the above-mentioned doping by a vacuum evaporation method, there are a method of co-evaporation and a method of previously mixing an evaporation source at a predetermined concentration. When each of the above dopants is doped in the light emitting layer, the dopant is uniformly doped in the thickness direction of the light emitting layer, but there may be a concentration distribution in the film thickness direction. For example, doping may be performed only near the interface with the hole transport layer, or conversely, doping may be performed near the electron transport interface.

The electron transport layer 7 is provided on the light emitting layer 5. The electron transport layer 7 is formed of a compound capable of efficiently transporting electrons injected from the cathode between the electrodes to which an electric field is applied in the direction of the light emitting layer 5. The electron transporting compound used for the electron transporting layer 7 needs to be a compound having high electron injection efficiency from the cathode 8 and capable of efficiently transporting the injected electrons. Materials satisfying such conditions include metal complexes such as aluminum complex of 8-hydroxyquinoline (JP-A-59-194393) and metal complexes of 10-hydroxybenzo [h] quinoline (JP-A-6-322362). Gazette), oxadiazole derivatives (JP-A-2-2167)
No. 91), distyrylbiphenyl derivatives (Japanese Unexamined Patent Application Publication No.
231970), silole derivatives (Japanese Unexamined Patent Publication No.
87616), a metal complex of 3- or 5-hydroxyflavone (Appl. Phys. Lett., Vol. 71,
3338, 1997), benzoxazole metal complex (JP-A-6-336586), benzothiazole metal complex (JP-A-9-279134), trisbenzimidazolylbenzene (US Pat. No. 5,645,645).
948), quinoxaline compounds (JP-A-6-2
07169), a phenanthroline derivative (Japanese Patent Application Laid-Open No. 5-331559), 2-t-butyl-9,10
-N, N'-dicyanoanthraquinone diimine (Phy
s. Stat. Sol. (A), vol. 142, p. 489,
1994), n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide, and the like. The film thickness of the electron transport layer 7 is usually 5 to 200 nm, preferably 10 to 200 nm.
100 nm.

As a method for further improving the luminous efficiency of the organic electroluminescent device, it is very effective to laminate the hole blocking layer 6 between the light emitting layer 5 and the electron transport layer 7 (FIGS. 2 and 3).
Shows the structure). The hole blocking layer 6 has a role of blocking injection of holes moving from the light emitting layer into the electron transport layer,
It is formed of a compound capable of efficiently transporting electrons injected from the cathode toward the light emitting layer 5. The hole blocking layer has a function of confining holes and electrons in the light emitting layer and improving luminous efficiency. As a hole blocking layer material satisfying such conditions, a mixed ligand complex represented by the following general formula (II):

[0050]

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(Wherein R ¹⁹ to R ²⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, an allyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, Carboxyl group, alkoxy group, alkylsulfonyl group, α-haloalkyl group, hydroxyl group, amide group optionally having substituent (s), aromatic hydrocarbon group optionally having substituent (s) or substituent (s) M represents an Al atom or a Ga atom; and Z represents the following general formula (IIa) or (II
(b) or (IIc)

[0052]

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(Where Y is any of Si, Ge or Sn
Represents an atom of^ThreeOr Ar ⁷Are independent
An aromatic hydrocarbon group or a substituent which may have a substituent
Represents an aromatic heterocyclic group which may have a substituent)

A binuclear metal complex represented by the following general formula (III):

[0055]

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(Wherein R ¹⁹ to R ²⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an alkenyl group, an allyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, Carboxyl group, alkoxy group, alkylsulfonyl group, α-haloalkyl group, hydroxyl group, amide group optionally having substituent (s), aromatic hydrocarbon group optionally having substituent (s) or substituent (s) Represents an aromatic heterocyclic group which may be substituted, and M represents an Al atom or a Ga atom)

1,2,4 represented by the following structural formula (IV)
A compound having at least one triazole ring,

[0058]

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A styryl compound represented by the following general formula (V) is exemplified.

[0060]

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(Wherein, Ar ⁸ to Ar ¹² represent an aromatic hydrocarbon group which may have a substituent or an aromatic heterocyclic group which may have a substituent)

Specific examples of the mixed ligand complex represented by the general formula (II) include bis (2-methyl-8-quinolinolato) (phenolato) aluminum, bis (2-methyl-
8-quinolinolato) (ortho-cresolato) aluminum, bis (2-methyl-8-quinolinolato) (meta-cresolato) aluminum, bis (2-methyl-8-quinolinolato) (para-cresolato) aluminum, bis (2-methyl) -8-quinolinolato) (ortho-phenylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (meta-phenylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (para-phenylphenolato) Aluminum, bis (2-methyl-
8-quinolinolato) (2,3-dimethylphenolato) aluminum, bis (2-methyl-8-quinolinolato)
(2,6-dimethylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (3,4-dimethylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (3,5-dimethylphenolato) ) Aluminum, bis (2-methyl-8-quinolinolato) (3,5
-Di-tert-butylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (2,6-diphenylphenolato) aluminum, bis (2-methyl-8)
-Quinolinolato) (2,4,6-triphenylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (2,4,6-trimethylphenolato) aluminum, bis (2-methyl-8-quinolinolato) (2,3
6-trimethylphenolato) aluminum, bis (2-
Methyl-8-quinolinolato) (2,3,5,6-tetramethylphenolato) aluminum, bis (2-methyl-
8-quinolinolato) (1-naphthrat) aluminum,
Bis (2-methyl-8-quinolinolato) (2-naphthrat) aluminum, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum, bis (2-methyl-8-quinolinolato) (triphenylgermanola) G) aluminum, bis (2-methyl-8-quinolinolato) (tris (4,4-biphenyl) silanolato) aluminum, bis (2,4-dimethyl-8-quinolinolato) (ortho-phenylphenolato) aluminum, bis ( 2,4-dimethyl-8-quinolinolato) (para-phenylphenolato) aluminum, bis (2,4
-Dimethyl-8-quinolinolato) (meta-phenylphenolato) aluminum, bis (2,4-dimethyl-8-)
Quinolinolato) (3,5-dimethylphenolato) aluminum, bis (2,4-dimethyl-8-quinolinolato)
(3,5-di-tert-butylphenolato) aluminum, bis (2-methyl-4-ethyl-8-quinolinolato) (para-cresolato) aluminum, bis (2-methyl-4-methoxy-8-quinolinolato) (Para-phenylphenolato) aluminum, bis (2-methyl-5)
-Cyano-8-quinolinolato) (ortho-cresolate)
Aluminum, bis (2-methyl-6-trifluoromethyl-8-quinolinolato) (2-naphthrat) aluminum, bis (2-methyl-quinolinolato) (phenolato) gallium, bis (2-methyl-8-quinolinolato)
(Ortho-cresolato) gallium, bis (2-methyl-)
8-quinolinolato) (para-phenylphenololato) gallium, bis (2-methyl-8-quinolinolato) (1-naphthrat) gallium, bis (2-methyl-8-quinolinolato) (2-naphthrat) gallium, bis (2 -Methyl-8-quinolinolato) (triphenylsilanolato) gallium, bis (2-methyl-8-quinolinolato) (tris (4,4-biphenyl) silanolato) gallium and the like. Particularly preferably, bis (2-methyl-8-quinolinolato) (2-naphthrat) aluminum, bis (2
-Methyl-8-quinolinolato) (triphenylsilanolato) aluminum.

As a specific example of the binuclear metal complex represented by the general formula (III), bis (2-methyl-8-quinolato)
Aluminum-μ-oxo-bis (2-methyl-8-quinolylato) aluminum, bis (2,4-dimethyl-8)
-Quinolinato) aluminum-μ-oxo-bis (2,
4-dimethyl-8-quinolinato) aluminum, bis-
(4-ethyl-2-methyl-8-quinolylato) aluminum-μ-oxo-bis (4-ethyl-2-methyl-8
-Quinolinato) aluminum, bis (2-methyl-4-)
(Methoxyquinolinolato) aluminum-μ-oxo-bis (2-methyl-4-methoxyquinolinolato) aluminum, bis (5-cyano-2-methyl-8-quinolinolato) aluminum-μ-oxo-bis (5- Cyano-2
-Methyl-8-quinolinolato) aluminum, bis (5
-Chloro-2-methyl-8-quinolinolato) aluminum-μ-oxo-bis (5-chloro-2-methyl-8-
Quinolinolato) aluminum, bis (2-methyl-5-
Trifluoromethyl-8-quinolinolato) aluminum-μ-oxo-bis (2-methyl-5-trifluoromethyl-8-quinolinolato) aluminum and the like. Particularly preferably, bis (2-methyl-8-quinolinolato) aluminum-μ-oxo-bis (2-methyl-
8-quinolinolato) aluminum. Specific examples of the compound having at least one 1,2,4-triazole ring represented by the structural formula (IV) are shown below.

[0064]

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As a specific example of the styryl compound represented by the general formula (V), for example, a distyrylbiphenyl compound (B-1) exemplified as a conventional blue light-emitting material can be given. The thickness of the hole blocking layer is usually 0.3 to 100 n.
m, preferably 0.5 to 10 nm. The hole blocking layer can be formed in the same manner as the hole transporting layer, but usually, a vacuum evaporation method is used.

The cathode 8 plays a role of injecting electrons into the electron transport layer 7. As the material used for the cathode 8, the material used for the anode 2 can be used, but for efficient electron injection, a metal having a low work function is preferable, and tin, magnesium, indium, calcium, A suitable metal such as aluminum or silver or an alloy thereof is used. Specific examples include a low work function alloy electrode such as a magnesium-silver alloy, a magnesium-indium alloy, and an aluminum-lithium alloy. Further, the interface between the cathode and the light emitting layer or the electron transport layer is LiF, LiF.
Inserting an ultra-thin film (0.1-5 nm) such as ₂ O
This is an effective method for improving the efficiency of the device (Appl.
Phys. Lett. 70, 152, 1997.
Year; IEEE Trans. Electron. Dev
ices, 44, 1245, 1997). Cathode 8
Is usually the same as that of the anode 2. In order to protect the cathode made of a low work function metal, further laminating a metal layer having a high work function and being stable to the atmosphere increases the stability of the device. For this purpose, aluminum,
Metals such as silver, nickel, chromium, gold, and platinum are used.

The structure reverse to that of FIG. 1, ie, the cathode 8, the electron transport layer 7, the light emitting layer 5, the hole transport layer 4, the anode 2
And the organic electroluminescent device of the present invention can be provided between two substrates, at least one of which has high transparency, as described above. Similarly, it is also possible to laminate in a structure opposite to the above-mentioned respective layer constitutions shown in FIGS. According to the organic electroluminescent device of the present invention, blue light emission with good color purity is obtained, and not only functions as a full-color or multi-color blue sub-pixel, but also produces a full-color display device by combining with a fluorescent conversion dye. (Japanese Patent Laid-Open No. 3-1
No. 52897).

[0068]

Next, the present invention will be described in more detail with reference to Synthesis Examples and Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

[Production Example of Exemplified Compound (2)] N, N'-
3.36 g of diphenylbenzidine, 7.61 g of 9-iodophenanthrene, 2.12 g of potassium carbonate, and copper powder 1.
67 g, 18-crown-6-ether 0.27 g
Add 5 ml of nitrobenzene, and add
The reaction was performed for 7 hours. After completion of the reaction, methanol 200 ml
The reaction solution was discharged therein, and the precipitated dark brown product was dissolved in chloroform. The solvent was distilled off, and the residue was washed with methanol. Thereafter, purification was carried out by column chromatography using silica gel to obtain 4.63 g of a yellow powder. The yield was 67%. This compound was analyzed by mass spectrometry and found to have a molecular weight of 688, FT-IR and ¹ H-
NMR confirmed that it was target compound (2). The melting point was measured and found to be 283 ° C. Further, Tg showed a high value of 146 ° C. as a result of differential thermal analysis measurement using DSC-20 manufactured by Seiko Instruments Inc. Compound (2)
The structure of is shown below.

[0070]

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Example 1 A glass substrate was subjected to ultrasonic cleaning with acetone, water cleaning with pure water, ultrasonic cleaning with isopropyl alcohol, drying with dry nitrogen,
After performing the V / ozone cleaning, the apparatus was set in a vacuum evaporation apparatus, and evacuated using an oil diffusion pump until the degree of vacuum in the apparatus became 2 × 10 ⁻⁶ Torr or less. Exemplified compound (2) was placed in a ceramic crucible, and vapor deposition was performed by heating with a tantalum wire heater around the crucible. The crucible temperature at this time was 346
The temperature was controlled in the range of ３５354 ° C. The degree of vacuum during evaporation is 1.4
A uniform and transparent film having a film thickness of 91 nm was obtained at a deposition rate of 0.3 to 0.5 nm / sec at × 10 ⁻⁶ Torr (about 1.9 × 10 ⁻⁴ Pa). The ionization potential of this thin film sample was measured using an ultraviolet electron analyzer (AC-1) manufactured by Riken Keiki Co., Ltd., and showed a value of 5.22 eV. The result of fluorescence measurement obtained by exciting this vapor-deposited film with a mercury lamp (wavelength: 350 nm) showed blue fluorescence at 450 nm. The deposited film was uniform and no crystallization was observed even after storage in the air for 120 days, and the fluorescence and the fluorescence intensity were maintained.

Comparative Example 1 Bis (2-methyl-8-quinolinolato) (para-phenylphenolato) aluminum (III) (B-2) shown below was used in place of Exemplified Compound (2) as a vapor deposition raw material.

[0073]

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A vapor deposition film was prepared in the same manner as in Example 1 except that the above was used. The ionization potential of this thin film sample was measured using an ultraviolet electron analyzer (AC-1) manufactured by Riken Keiki Co., Ltd., and showed a value of 5.35 eV. The result of fluorescence measurement obtained by exciting this vapor deposited film with a mercury lamp (wavelength: 350 nm) showed blue-green fluorescence at 500 nm. When this deposited film was stored in the air for 7 days, the transparency of the film was lost and the fluorescence was lost. In addition, dot-like defects also occurred.

Example 2 An organic electroluminescent device having the structure shown in FIG. 2 was manufactured by the following method. Indium tin oxide (ITO) transparent conductive film deposited on a glass substrate with a thickness of 120 nm (Geomatec; electron beam filmed product; sheet resistance 15Ω)
Was patterned into 2 mm wide stripes using ordinary photolithographic techniques and hydrochloric acid etching to form anodes. The patterned ITO substrate is cleaned in the order of ultrasonic cleaning with acetone, water cleaning with pure water, and ultrasonic cleaning with isopropyl alcohol, dried with nitrogen blow, and finally cleaned with ultraviolet and ozone, and placed in a vacuum evaporation apparatus. installed. After the rough exhaust of the above apparatus is performed by an oil rotary pump, the degree of vacuum in the apparatus is 2 × 10 ⁻⁶ Torr (about ^2.10 Torr).
Evacuation was performed using an oil diffusion pump equipped with a liquid nitrogen trap until the pressure became 7 × 10 ⁻⁴ Pa) or less. As a hole transport layer material, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (H-1) shown below is used.

[0076]

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It was placed in a ceramic crucible and heated by a tantalum wire heater around the crucible to perform vapor deposition. The temperature of the crucible at this time was controlled in the range of 251 to 270 ° C. The degree of vacuum at the time of vapor deposition is 0.9 × 10 ⁻⁶ Torr (about 1.2 × 10 ⁻⁴ Torr).
Pa) at a deposition rate of 0.1 to 0.5 nm / sec and a film thickness of 60
As a result, a hole transport layer 4 having a thickness of nm was obtained. Next, as a material of the light emitting layer 5, the exemplified compound (2) was vapor-deposited on the hole transport layer 4 in the same manner. The temperature of the crucible at this time is 278-30.
The temperature was controlled within a range of 4 ° C. The degree of vacuum during the deposition is 6.5 × 10
^-7 Torr (approximately 8.7 × 10 ^-5 Pa) at a deposition rate of 0.
The film thickness was 30 nm at 1 to 0.4 nm / sec. Subsequently, bis (2-methyl-8) is used as a material for the hole blocking layer 6.
-Quinolinolato) (triphenylsilanolato) aluminum

[0078]

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Was deposited on the light emitting layer 5 in the same manner. At this time, the temperature of the crucible was controlled in the range of 180 to 190 ° C. The degree of vacuum during deposition is 7.0 × 10 ⁻⁷ Torr
(About 9.3 × 10 ⁻⁵ Pa) and a deposition rate of 0.1 to 0.5.
At nm / sec, the film thickness was 20 nm. The ionization potential of this compound was 5.5 eV. Further, as a material of the electron transport layer 7, an 8-hydroxyquinoline complex of aluminum (E-1)

[0080]

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Then, vapor deposition was performed on the hole blocking layer 6 in the same manner. At this time, the temperature of the crucible was controlled in the range of 303 to 317 ° C. The degree of vacuum during the deposition is 7.0 × 10 ⁻⁷ Torr
r (about 9.3 × 10 ⁻⁵ Pa) at a deposition rate of 0.1 to 0.1.
At 4 nm / sec, the film thickness was 25 nm. The substrate temperature during vacuum deposition of the electron transport layer 7 from the hole transport layer 4 was kept at room temperature. Here, the element on which the vapor deposition up to the electron transporting layer 7 has been performed is once taken out of the vacuum vapor deposition apparatus into the atmosphere, and a 2 mm wide stripe-shaped shadow mask is used as a cathode vapor deposition mask. It is closely attached to the element so as to be orthogonal to each other, installed in another vacuum deposition apparatus, and the degree of vacuum in the apparatus is set to 2 × 10
Evacuation was performed until the pressure became ^-6 Torr (about 2.7 × 10 ^-4 Pa) or less. As the cathode 8, first, magnesium fluoride (M
gF ₂ ) using a molybdenum board at a deposition rate of 0.0
6 nm / sec, degree of vacuum 2.0 × 10 ⁻⁶ Torr (about 2.7
(× 10 ⁻⁴ Pa) at a thickness of 0.5 nm on the electron transport layer 7. Next, the aluminum was similarly heated by a molybdenum boat, and the deposition rate was 0.2 to 0.8 nm /
Second, degree of vacuum 1 × 10 ⁻⁵ Torr (about 1.3 × 10 ⁻³ P
In a), an aluminum layer having a thickness of 40 nm was formed. Furthermore, copper is further heated thereon by a molybdenum board to increase the conductivity of the cathode, and the deposition rate is 0.3 to
A 40 nm-thick copper layer was formed at 1.0 nm / sec and a degree of vacuum of 8.0 × 10 ⁻⁶ Torr (about 1.1 × 10 ⁻³ Pa) to complete the cathode 8. The substrate temperature during the deposition of the above three-layer cathode 8 was kept at room temperature. 2mm × 2
An organic electroluminescent device having a light-emitting area with a size of mm was obtained. The light emission characteristics of this device include a light emission start voltage, luminance at a current density of 250 mA / cm ² , and 100 c
Table 14 shows the values of the luminous efficiency at d / m ² and the slope of the luminance-current density characteristics. In addition, CIE chromaticity coordinates (JIS
Table 14 shows the values of x and y for Z8701). This device shows uniform blue light emission, and the peak wavelength of the light emission is 45.
It emitted blue light at 5 nm. Even after long-term storage, no remarkable rise in driving voltage was observed, and there was no decrease in luminous efficiency, and stable storage stability of the device was obtained. FIG. 4 shows driving time-luminance characteristics. When this device was continuously driven at a constant current of 250 mA / cm ² , the luminance after 40 seconds was 58% of the initial luminance.

Example 3 Perylene which is a blue fluorescent dye in the light emitting layer 5

[0083]

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Example 2 except that was doped 1.2%
In the same manner as in the above, an organic electroluminescent device was produced. Table 14 shows the results of the light emission characteristics of the above devices. Table 14 shows the values of x and y in the CIE chromaticity coordinates (JIS Z8701).
Shown in By doping perylene, the luminous efficiency was improved with little change in color purity. FIG. 4 shows driving time-luminance characteristics. When this device was continuously driven at a constant current of 250 mA / cm ² , the brightness after 40 seconds was 65% of the initial brightness, and the stability of the device was improved by doping perylene.

Comparative Example 2 Bis (2-methyl-8-quinolinolato) (para-phenylphenolate) was used in the light-emitting layer 5 in place of the exemplified compound (2).
An organic electric field device was manufactured in the same manner as in Example 2 except that aluminum (III) (E-2) was used. Table 14 shows the emission characteristics of this device. In addition, CIE chromaticity coordinates (JIS
Table 14 shows the values of x and y for Z8701). This device emitted blue-green light. FIG. 4 shows driving time-luminance characteristics. When the device was continuously driven at a constant current of 250 mA / cm ² , the luminance after 40 seconds was reduced to 44% of the initial luminance.

Comparative Example 3 Bis (2-methyl-8-quinolylato) aluminum-μ-oxo-bis (2-methyl-8-quinolylato) aluminum (Ip) was used in the light-emitting layer 5 in place of the exemplified compound (2).
5.33 eV)

[0087]

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An organic electroluminescent device was produced in the same manner as in Example 2 except that the above was used. CIE chromaticity coordinates (JIS Z8
The values of x and y in 701) are v = 0.26 and y = 0.4
In 1, the device emitted blue-green light.

[0089]

[Table 14]

[0090]

According to the organic electroluminescent device of the present invention, since the device has a light emitting layer containing a specific aromatic amine, blue light with good color purity can be achieved, and a device having improved stability can be obtained. Obtainable. Accordingly, the organic electroluminescent device according to the present invention can be used as a light source (for example, a light source of a copier, a liquid crystal display) such as a flat panel display (for example, for an OA computer or a wall-mounted television), a multi-color display device, or a surface light emitter. And light sources for backlights of instruments and the like, display boards, and marker lights. Particularly, as a display element for a vehicle or an outdoor which requires high heat resistance, its technical value is great.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of the organic electroluminescent device of the present invention.

FIG. 2 is a schematic sectional view showing another example of the organic electroluminescent device of the present invention.

FIG. 3 is a schematic sectional view showing another example of the organic electroluminescent device of the present invention.

FIG. 4 is a graph showing driving time-luminance characteristics.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Anode buffer layer 4 Hole transport layer 5 Emitting layer 6 Hole blocking layer 7 Electron transport layer 8 Cathode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C07D 215/48 C07D 215/48 215/50 215/50 215/54 215/54 249/08 512 249/08 512 537 537 C09K 11 / 06 620 C09K 11/06 620 660 660 H05B 33/22 H05B 33/22 B

Claims (5)

[Claims] 1. An organic electroluminescent device comprising at least a hole transporting layer, a light emitting layer and an electron transporting layer sandwiched between an anode and a cathode on a substrate, wherein the light emitting layer has the following general formula (I)
An organic electroluminescent device comprising a compound represented by the formula: Embedded image (Wherein, Ar ¹ and Ar ² each independently represent an aromatic hydrocarbon group or an aromatic heterocyclic group, each of which may have a substituent, and R ¹ to R ¹⁸ are each independently And a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, or
An alkyl group, an aralkyl group, an alkenyl group, an amino group, an amide group, an alkoxycarbonyl group, an alkoxy group, an aromatic hydrocarbon group or a substituent, each of which may have a substituent; Represents an aromatic heterocyclic group which may have a substituent, and X represents a divalent aromatic ring residue which may have a substituent) 2. In the general formula (I), X is a phenylene group, a biphenylene group, a terphenylene group, an anthrylene group or a naphthylene group, each of which may have a substituent. Item 2. The organic electroluminescent device according to Item 1. 3. The organic electroluminescent device according to claim 1, wherein a hole blocking layer is provided between the light emitting layer and the electron transporting layer. 4. The method according to claim 1, wherein the hole blocking layer has the following general formula (II) or
A metal complex represented by the formula (III),
At least one triazole derivative and the following general formula
At least one styryl compound represented by (V)
The organic electric field according to claim 3, wherein the organic electric field is constituted.
Light emitting element. Embedded image(Where R¹⁹Or R^{twenty four}Is independently a hydrogen atom,
Halogen atom, alkyl group, aralkyl group, alkenyl
Group, allyl group, cyano group, amino group, acyl group, alcohol
Xycarbonyl group, carboxyl group, alkoxy group,
Alkylsulfonyl group, α-haloalkyl group, hydroxyl group,
An amide group which may have a substituent,
May have an aromatic hydrocarbon group or a substituent
Represents an aromatic heterocyclic group, M represents an Al atom or a Ga atom
And Z represents the following general formula (IIa), (IIb) or (IIc)
Represents any of the groups )(Wherein, Y represents any atom of Si, Ge or Sn.
I, Ar^ThreeOr Ar ⁷Is each independently a substituent
Having an aromatic hydrocarbon group or a substituent which may have
Represents an aromatic heterocyclic group which may be present)(Where R¹⁹Or R^{twenty four}Is independently a hydrogen atom,
Halogen atom, alkyl group, aralkyl group, alkenyl
Group, allyl group, cyano group, amino group, acyl group, alcohol
Xycarbonyl group, carboxyl group, alkoxy group,
Alkylsulfonyl group, α-haloalkyl group, hydroxyl group,
An amide group which may have a substituent,
May have an aromatic hydrocarbon group or a substituent
Represents an aromatic heterocyclic group, M represents an Al atom or a Ga atom
(Shown)Embedded image(Wherein, Ar⁸Or Ar¹²Is each independently a substituent
Having an aromatic hydrocarbon group or a substituent which may have
Represents an optionally substituted aromatic heterocyclic group) 5. The film thickness of the hole blocking layer is 0.5 to 30 nm.
The organic electroluminescent device according to claim 3, wherein