JPH11273867A - Organic electroluminescent device - Google Patents

Abstract

(57) [Problem] To provide an organic electroluminescent device capable of achieving blue emission with good color purity and having improved stability. SOLUTION: An organic electroluminescent device including at least a hole transporting layer sandwiched by an anode and a cathode, a light emitting layer and a hole blocking layer on a substrate, wherein the light emitting layer contains an aromatic amine compound, An organic electroluminescent device, wherein the ionization potential of the hole transport layer is 0.1 eV or more greater than the ionization potential of the light emitting layer, and the ionization potential of the hole blocking layer is 0.2 eV or more greater than the ionization potential of the light emitting layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device, and more particularly to a thin film device which emits light by applying an electric field to a light emitting layer made of an organic compound.

[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 (50-1000Hz), 2) High drive voltage (up to 200V), 3) It is difficult to make full color (especially blue), 4) High cost of peripheral drive circuit. I have.

However, in recent years, in order to improve the above problems,
Development of EL devices using organic thin films has been started. In particular, in order to enhance the luminous efficiency, the type of the 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 luminescent layer composed of an aluminum complex of 8-hydroxyquinoline were used. Of an organic electroluminescent device provided with an electrode (Appl. Phys. Lett., 51
Vol., Pp. 913, 1987), the luminous efficiency has been greatly improved as compared with a conventional EL device using a single crystal such as anthracene. For example, doping a fluorescent dye for laser such as coumarin using an aluminum complex of 8-hydroxyquinoline as a host material (J. Appl. Phy.
s., 65, p. 3610, 1989), the 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) (Nature, 347, 539, 1990), poly [2 -Methoxy-5- (2-ethylhexyloxy) -1,4-phenylene vinylene] (Appl. Phys. Lett., 58, 1982)
P., 1991 et al.), Poly (3-alkylthiophene) (Jpn.
J. Appl. Phys, Vol. 30, L1938, 1991), and the development of an electroluminescent device using a polymer material, 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, 61, 1044, 1992).

[0005]

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-mentioned element deterioration is deterioration of the thin film shape of the organic layer. This 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.
It is thought to be caused by such factors. 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. The compound used for the light-emitting layer of the blue light-emitting element has a low molecular weight and a low melting point due to a restriction that the pi-electron conjugation cannot be expanded.
Many materials have low Tg. At present, it is not sufficiently stable chemically.

Heretofore, compounds used in blue organic electroluminescent devices include anthracene, tetraphenylbutadiene, pentaphenylcyclopentadiene, distyrylbenzene derivative, oxadiazole derivative, azomethine zinc complex, benzazole metal complex, Ligand aluminum complex, N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-biphenyl-4,4'-diamine, polyvinylcarbazole, 1,2,4-triazole derivative , Aminopyrene dimers, distyrylbiphenyl derivatives, silole derivatives and the like have been reported. Among the above blue light-emitting materials,
Representative compounds whose device characteristics have been well studied are shown below:

[0008]

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[0009]

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[0010]

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Distyrylbiphenyl derivative (B-1)
Has a strong fluorescence intensity and does not form an exciplex even when used in a device, and has been reported to emit blue light (Appl.
Phys. Lett., Vol. 67, p. 3853, 1995), the ionization potential in the thin film state is as high as 5.9 eV, and it is difficult for holes to be injected from the hole transport layer.
There is a problem that a broad peak having a light emission maximum is shown in the vicinity and the color purity of blue is not good. This color purity is not improved by doping. Bis (2-methyl-8
-Quinolinolato) (p-phenylphenolato) aluminum complex (B-2) also has insufficient blue color purity, and although the color purity is improved by doping with perylene, the driving stability is at a practical level. Has not been reached (Japanese Unexamined Patent Application Publication No.
No. 8377). N, N'-diphenyl- which is an aromatic diamine
N, N '-(3-methylphenyl) -1,1'-biphenyl-4,4'-diamine (usually referred to as TPD) (B-3), when combined with a triazole derivative as a hole blocking layer Four
An EL spectrum having an emission peak at 64 nm is shown (Jp
n. J. Appl. Phys., 32, L917, 1993), TPD
Has a thermal instability such as crystallization because its Tg is as low as 63 ° C. 85 ° C as Tg value from the high temperature characteristics of automotive display elements
The above is required.

For the above-mentioned reasons, 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 blue purity of the organic electroluminescent device is not improved,
Unstable heat resistance and drive characteristics are undesirable characteristics as display elements such as flat panel displays aiming at full color display.

In view of the above situation, the present inventors have conducted intensive studies with the aim of providing an organic electroluminescent device having high blue purity and heat resistance. As a result, holes sandwiched between an anode and a cathode on a substrate are disclosed. In an organic electroluminescent device including at least a transport layer, a light-emitting layer, and a hole-blocking layer, an aromatic amine compound is used as the light-emitting layer, and the relative relationship between the ion transport potentials of the hole-transport layer, the light-emitting layer, and the hole-blocking layer is specified. By doing so, they found that the above problem could be solved, and completed the present invention.

[0014]

That is, the gist of the present invention is to provide an organic electroluminescent device including at least a hole transport layer, a light emitting layer and a hole blocking layer sandwiched between an anode and a cathode on a substrate. The light emitting layer contains an aromatic amine compound, the ionization potential of the hole transport layer is 0.1 eV or more larger than the ionization potential of the light emitting layer, and the ionization potential of the hole blocking layer is 0.2 eV or more larger than the ionization potential of the light emitting layer. An organic electroluminescent device characterized by the above.

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 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 6 is The hole blocking layers, 8 each represent a cathode. The substrate 1 serves as a support for the organic electroluminescent element, and is made of a quartz or glass plate, a metal plate or a metal foil, a plastic film or a sheet, or the like. Especially glass plates,
A plate of a transparent synthetic resin such as polyester, polymethacrylate, polycarbonate and polysulfone is preferred. 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 small, the organic electroluminescent device may be deteriorated by the outside air passing through the substrate, which is not preferable. For this reason, a method of providing a dense silicon oxide film or the like on at least one surface of the synthetic resin substrate to secure gas barrier properties is also a preferable method.

An anode 2 is provided on a substrate 1, and the anode 2 plays a role of injecting holes into a hole transport layer. 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; (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 metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, or conductive polymer fine powder, they are dispersed in a suitable 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 (Appl. Phys. Lett. 60, 2711,
1992). 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, the transmittance of visible light is usually 60% or more, preferably 80% or more. In this case, the thickness is usually 5 to 1000 nm, preferably 10 to 1000 nm. 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 a different conductive material on the anode 2.

On the anode 2, a hole transport layer 4 is provided. In the present invention, the ionization potential of the hole transport layer needs to be 0.1 eV or more higher than the ionization potential of the light emitting layer for the reasons described below. Further, 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 transport the injected holes efficiently. For that purpose, the ionization potential is small, the transparency to visible light is high, and the hole mobility is large.
Further, it is required that the material be excellent in stability and hardly generate impurities serving as traps during production or use. In addition to the above general requirements, when considering applications for in-vehicle display, the element is required to have further heat resistance. Therefore, a material having a Tg of 85 ° C. or more is desirable.

As such a hole transport material, for example, an aromatic diamine compound in which a tertiary aromatic amine unit such as 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane is linked (Japanese Patent Laid-Open Publication No. JP-A-59-194393), 4,4'-
Aromatic amines containing two or more tertiary amines represented by bis [N- (1-naphthyl) -N-phenylamino] biphenyl and having two or more condensed aromatic rings substituted with nitrogen atoms (Japanese Patent Laid-Open No. -234681), an aromatic triamine having a starburst structure as a derivative of triphenylbenzene (U.S. Pat. No. 4,923,774), N, N'-diphenyl-N, N'-bis (3
Aromatic diamines such as (-methylphenyl) biphenyl-4,4'-diamine (U.S. Pat. No. 4,764,625), triphenylamine derivatives which are sterically asymmetric as a whole molecule (JP-A-4-129271), and pyrenyl groups. Compounds in which a plurality of aromatic diamino groups are substituted (JP-A-4-175395), aromatic diamines in which tertiary aromatic amine units are linked by ethylene groups (JP-A-4-264189), and aromatics having a styryl structure Aromatic diamines (JP-A-4-290851), those obtained by linking aromatic tertiary amine units with thiophene groups (JP-A-4-304466), and starburst-type aromatic triamines (JP-A-4-308688) Benzylphenyl compounds (JP-A-4-364153), tertiary amines linked by a fluorene group (JP-A-5-25473), and triamine compounds (JP-A-5-239455). Broadcast),
Bisdipyridylaminobiphenyl (JP-A-5-320634), N, N, N-triphenylamine derivative (JP-A-6-320634)
1972), an aromatic diamine having a phenoxazine structure (JP-A-7-138562), a diaminophenylphenanthridine derivative (JP-A-7-252474),
Examples thereof include silazane compounds (U.S. Pat. No. 4,950,950), silanamin derivatives (JP-A-6-49079), phosphamine derivatives (JP-A-6-25659), 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 (Appl. Ph.
ys. Lett., 59, 2760, 1991), polyphosphazene (JP-A-5-310949), polyamide (JP-A-5-310949), polyvinyl triphenylamine (JP-A-7-53953). Gazette), a polymer having a triphenylamine skeleton (Japanese Patent Application Laid-Open No. 4-130665), and a polymer in which triphenylamine units are linked by a methylene group or the like (Synt
hetic Metals, 55-57, 4163, 1993), polymethacrylate containing an aromatic amine (J. Polym. Sci.,
Polym. Chem. Ed., 21, 969, 1983).

The hole transport layer 4 is formed by laminating the above hole transport material on the anode 2 by a coating method or a vacuum evaporation method. In the case of the coating method, one hole transport material is used.
A seed or two or more, and if necessary, an additive such as a binder resin or a coatability improver that does not trap holes are added and dissolved to prepare a coating solution, and the solution is formed on the anode 2 by a method such as spin coating. And dried to form a hole transport layer 4
To form Examples of the binder resin include polycarbonate, polyarylate, and polyester. If the amount of the binder resin is large, the hole mobility is reduced. Therefore, a small amount is desirable, and usually 50% by weight or less is preferable.

In the case of the vacuum evaporation method, the hole transporting material is put into a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is evacuated to about 10 ^-4 Pa by a suitable vacuum pump, and then the crucible is heated. Then, the hole transport material is evaporated to form the hole transport layer 4 on the anode 2 on the substrate 1 placed facing the crucible. When the hole transport layer 4 is formed, a metal complex and / or metal salt of an aromatic carboxylic acid (JP-A-4-320484), a benzophenone derivative and a thiobenzophenone derivative (JP-A-5-295361) are further used as acceptors.
Publication), fullerenes (JP-A-5-331458) and the like are doped at a concentration of 10 ^-3 to 10% by weight to generate holes as free carriers, thereby enabling low-voltage driving. be able to.

When the above-described additives and doping agents are used in combination in the hole transporting layer, the ionization potential of the entire hole transporting layer is 0.1% higher than the ionization potential of the light emitting layer.
If the range is 1 eV or more, it can be appropriately selected and used. The thickness of the hole transport layer 4 is usually 10 to 300 nm.
, 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 the contact with the anode can be made well, a uniform thin film can be formed, and it is 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-63-295695), starbust-type aromatic triamines (JP-A-4-308688), and hydrazone compounds (JP-A-4-320483) have been used. Gazette),
Alkoxy-substituted aromatic diamine derivatives (Japanese Unexamined Patent Publication No.
No. 0995), p- (9-anthryl) -N, N-di-p-tolylaniline (JP-A-3-111485), polythienylenevinylene and poly-p-phenylenevinylene (JP-A-4-111).
No. 145192), polyaniline (Appl. Phys. Lett., 6
4, p. 1245, 1994), sputtered carbon films (JP-A-8-31573), and metal oxides such as vanadium oxide, ruthenium oxide and molybdenum oxide (No. 43). JSCE Lecture Meeting, 27a-SY
-9, 1996).

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. Preferred specific examples of these compounds include porphine, 5,
10,15,20-tetraphenyl-21H, 23H-porphine, 5,1
0,15,20-tetraphenyl-21H, 23H-porphine cobalt (II), 5,10,15,20-tetraphenyl-21H, 23H-porphine copper (II), 5,10,15,20-tetraphenyl -21H, 23H
-Porphine zinc (II), 5,10,15,20-tetraphenyl
-21H, 23H-porphine vanadium (IV) oxide, 5.1
0,15,20-tetra (4-pyridyl) -21H, 23H-porphine, 29H, 31H-phthalocyanine, copper (II) phthalocyanine, zinc (II) phthalocyanine, titanium phthalocyanine oxide, magnesium phthalocyanine, lead phthalocyanine, copper (II ) Compounds such as 4,4 ', 4 ", 4"'-tetraaza-29H, 31H-phthalocyanine. In the case of the 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. The light emitting layer 5 is provided on the hole transport layer 4. The light emitting layer 5 is transported between the electrodes to which the electric field is applied, the holes injected from the anode 2 and transported through the hole transport layer, and the holes injected from the cathode 8 and transported through the hole blocking layer 6. It is formed from a compound that emits blue light by efficiently recombining the electrons. For this purpose, a compound having both hole-transporting properties and electron-transporting properties, having high hole mobility and electron mobility, and having excellent stability and being less likely to generate trapping impurities during production or use. Is required. Further, in order to enable blue light emission, it is necessary that the fluorescence wavelength in a thin film state is in the range of 400 to 500 nm.

In the present invention, a fluorescent aromatic amine compound is used as a material satisfying the above conditions. Conventionally,
Attempts have been made to use an aromatic amine compound as a light-emitting layer having a hole-transport property, but the hole-transport layer was not provided between the anode and the anode (Jpn. J. Appl. Phys., 32, L917, 199
3 years), the ionization potential of the light-emitting layer is higher than the ionization potential of the hole transport layer (Jpn. J. Appl.
Phys., 35, 4819, 1996), so that only a blue light-emitting device having low luminous efficiency and low stability was obtained.

In the present invention, in order to effectively use the hole transporting aromatic amine compound as the light emitting layer, the ionization potential of the hole transport layer is lower than the ionization potential of the hole transport layer by 0.1 eV or more. 0.2 eV
It has been found that it is preferable to use a fluorescent aromatic amine having a small ionization potential. With this element structure, it is possible to simultaneously increase the hole concentration in the light emitting layer when the element is energized, and to prevent extinction of the exciton at the anode due to recombination in the light emitting layer.

The material of the light emitting layer in the organic electroluminescent device of the present invention is not particularly limited as long as it satisfies the ionization potential relationship with the hole transport layer and the hole blocking layer. It is desirable to have a high glass transition temperature (Tg) in consideration of prevention of crystallization and thermal stability. As the aromatic amine compound having a high Tg, it is useful to contain a tertiary nitrogen atom having at least one condensed aromatic ring group as a substituent. In particular, it is more preferable that the light emitting layer contains an aromatic amine compound represented by the following general formula (I).

[0029]

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In the above formula (I), X represents a divalent aromatic hydrocarbon group or an aromatic heterocyclic group which may have a substituent, and preferably a substituent. Divalent benzene ring, naphthalene ring, anthracene ring,
A binaphthyl, a fluorene ring, a phenanthrene ring, a pyrene ring, an acridine ring, a phenazine ring, a phenanthridine ring, a phenanthroline ring, a bipyridyl ring, or a biphenyl; and the substituent is a halogen atom; An alkenyl group such as a vinyl 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 phenoxy group and a benzyloxy group; and a dialkylamino group such as a diethylamino group and a diisopropylamino group. Particularly preferred examples of the substituent include a methyl group, a phenyl group and a methoxy group.

Ar ¹ to Ar ⁴ each represent an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent. Preferably, Ar ¹ to Ar ⁴ each independently have a substituent. Good phenyl group, biphenyl group, naphthyl group, anthryl group, phenanthryl group, pyrenyl group, pyridyl group, triazyl group, pyrazyl group, quinoxalyl group, thienyl group are mentioned, and the substituent is a halogen atom; methyl group, ethyl group, etc. An alkyl group having 1 to 6 carbon atoms; an alkenyl group such as a vinyl 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 Aryloxy groups such as phenoxy group and benzyloxy group; dialkylamino groups such as diethylamino group and diisopropylamino group And a no group. Particularly preferred examples of the substituent include a methyl group, a phenyl group and a methoxy group.

Further, at least X and Ar ^{1 to} Ar ⁴
One of benzene ring, naphthalene ring, anthracene ring, binaphthyl, fluorene ring, phenanthrene ring, pyrene ring, acridine ring, phenazine ring, phenanthridine ring, phenanthroline ring, selected from condensed aromatic ring groups such as bipyridyl ring It is. It is also preferable that the aromatic amine compound having a high Tg is selected from aromatic amine compounds represented by the following general formula (II), which is called a star burst type.

[0033]

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In the general formula (II), Y is selected from a nitrogen atom or a trivalent benzene ring bonded at the 1,3,5-position. Ar ⁵ and Ar ⁶ each represent an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent, preferably a phenyl group which may each independently have a substituent , A biphenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a pyrenyl group, a pyridyl group, a triazyl group, a pyrazyl group, a quinoxalyl group, and a thienyl group, wherein the substituent is a halogen atom; a methyl group;
An alkyl group having 1 to 6 carbon atoms such as an ethyl group; an alkenyl group such as a vinyl group; an alkoxycarbonyl group having 1 to 6 carbon atoms such as a methoxycarbonyl group and an ethoxycarbonyl group; 6 represents an alkoxy group; an aryloxy group such as a phenoxy group and a benzyloxy group; and a dialkylamino group such as a diethylamino group and a diisopropylamino group. Particularly preferred examples of the substituent include a methyl group, a phenyl group and a methoxy group.

In the present invention, the molecular structure represented by the general formula (I) or (II) allows the Tg to be 85 ° C. or higher, and the improvement in heat resistance makes the non-crystallizable non-crystallizable non-crystallizable non-crystallizable compound. It is possible to provide a crystalline thin film, and to reduce the mutual diffusion of molecules between the hole transport layer and the electron transport layer.
It can be sufficiently suppressed even at a high temperature of at least ℃. In addition, the ionization potential is 0.1% lower than that of the hole transport layer.
eV or more and 0.2
It is possible to design a light emitting layer having a maximum of eV or more and having a fluorescence maximum in a wavelength region of 400 to 500 nm.

Preferred specific examples of the aromatic amine compounds represented by the above general formulas (I) and (II) are shown in Tables 1 to 5, but are not limited thereto.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4]

[0041]

[Table 5]

These compounds may be used alone or, if necessary, may be used as a mixture. The light emitting layer 5 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.

The thickness of the light emitting layer 5 is usually 5 to 300 nm, preferably 10 to 100 nm. In order to uniformly form such a thin film, generally, a vacuum deposition method is often used. Doping a fluorescent dye with the light emitting layer material as a host material is an effective method for improving the luminous efficiency of blue light, improving the color purity, and further improving the driving life of the device. As doped dyes having blue fluorescence, condensed polycyclic aromatic rings such as perylene (JP-A-5-19)
No. 8377), coumarin derivatives, naphthalimide derivatives (JP-A-4-320486), aromatic amine derivatives (JP-A-8-199162) and the like. The proportion of these doped dyes contained in the host material is 0.1 to 10
Preferably it is in the range of weight%. Of course, in order to obtain green or red light emission, it is also possible to dope a green fluorescent dye or a red fluorescent dye. 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 the above dopants are doped in the light emitting layer, they are uniformly doped in the thickness direction of the light emitting layer, but may have 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, may be doped near the interface with the electron transport layer. When the above-mentioned additives and the like are used in combination in the light emitting layer, the ionization potential of the entire light emitting layer is 0.1 e than that of the hole transport layer.
V and 0.2 eV lower than that of the hole blocking layer.
If it is smaller than the above range, it can be appropriately selected and used.

The hole blocking layer 6 is provided on the light emitting layer 5. The hole blocking layer 6 has a role of preventing holes moving from the light emitting layer from reaching the cathode, and a compound capable of efficiently transporting electrons injected from the cathode toward the light emitting layer 5. It is formed. The physical properties required for the material constituting the hole blocking layer are that the electron mobility is high and the hole mobility is low, and in order to efficiently confine holes in the light emitting layer, the ionization potential of the light emitting layer is It is necessary to have a value of the ionization potential larger than 0.2 eV. Since the hole transporting layer is made of a material having no electron transporting ability, 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 (III):

[0046]

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(Wherein R ^{1 to} R ⁶ each 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, a carboxyl group, an alkoxy group, Group, alkylsulfonyl group, α-haloalkyl group, hydroxyl group, amide group optionally having substituent (s), aromatic hydrocarbon ring group optionally having substituent (s) or optionally having substituent (s) Represents an aromatic heterocyclic group, M represents an Al atom or a Ga atom, and L represents the following general formulas (IIIa) and (II)
Ib) or (IIIc). )

[0048]

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(In the formula, Z represents any atom of Si, Ge, and Sn, and Ar ^{9 to} Ar ¹⁰ represent an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent. Represents a binuclear metal complex represented by the following general formula (IV):

[0050]

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(Wherein, R ^{1 to} R ⁶ each 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, a carboxyl group, an alkoxy group, A group, an alkylsulfonyl group, an α-haloalkyl group, a hydroxyl group, an amide group which may have a substituent, an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent, Represents an Al atom or a Ga atom.) A compound having at least one 1,2,4-triazole ring represented by the following structural formula (V),

[0052]

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

[0054]

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(In the formula, Ar ¹² represents a divalent aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent, and Ar ^{13 to} Ar ¹⁶ each have a substituent. Represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may be

Specific examples of the mixed ligand complex represented by the general formula (III) include bis (2-methyl-8-quinolinolato) (phenolato) aluminum and bis (2-methyl-8-
Quinolinolato) (ortho-cresolato) aluminum,
Bis (2-methyl-8-quinolinolato) (meta-cresolato) aluminum, bis (2-methyl-8-quinolinolato)
(Para-cresolate) 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-dimethylphenolate) (Rat) 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) (triphenylgermanolato) 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-cresolato) aluminum, bis (2-methyl-6-trifluoromethyl-8-quinolinolato) (2-naphthrat) aluminum, bis (2-methyl-8-quinolinolato) (phenolato) gallium, bis ( 2-methyl-8-quinolinolato) (ortho-cresolate)
Gallium, bis (2-methyl-8-quinolinolato) (para-
Phenylphenolatogallium, bis (2-methyl-8-quinolinolato) (1-naphthrat) gallium, bis (2-methyl)
-8-Quinolinolato) (2-naphtolat) gallium, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) gallium, bis (2-methyl-8-quinolinolato) (tris (4,4-biphenyl) silanolate Gallium). 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 (IV), bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinolato) aluminum , Bis (2,4-dimethyl-8-quinolato)
Aluminum-μ-oxo-bis- (2,4-dimethyl-8-
Quinolilat) aluminum, bis (4-ethyl-2-methyl)
-8-quinolinolato) aluminum-μ-oxo-bis-
(4-ethyl-2-methyl-8-quinolinolato) 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 preferred is bis (2-methyl-8-quinolato) aluminum-μ-oxo-bis- (2-methyl-8-quinolinato) aluminum. 1, represented by the structural formula (V)
Specific examples of the compound having at least one 2,4-triazole ring are shown below.

[0058]

Embedded image

Specific examples of the styryl compound represented by the general formula (VI) include a distyrylbiphenyl compound (B-1) exemplified as a conventional blue light-emitting material. The thickness of the hole blocking layer 6 is usually 0.3 to 100 nm, 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.

In order to further improve the luminous efficiency of the device, an electron transport layer 7 is provided between the hole blocking layer 6 and the cathode 8.
May be provided. 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 hole blocking layer 6. The electron transport layer has an effect of preventing excitons generated by recombination in the light emitting layer from being diffused and quenched by the cathode 8.

The electron transporting compound used for the electron transporting layer 7 has a high electron injection efficiency from the cathode 8 and
It is necessary that the compound has high electron mobility and can efficiently transport injected electrons. Materials satisfying such conditions include metal complexes such as aluminum complexes of 8-hydroxyquinoline (JP-A-59-1943).
No. 93), a metal complex of 10-hydroxybenzo [h] quinoline (JP-A-6-322362), an oxadiazole derivative (JP-A-2-2176791), and a distyrylbiphenyl derivative (JP-A-3-231970). Publication), silole derivatives (JP-A-9-87616), 3- or 5-hydroxyflavone metal complexes (Appl. Phys. Lett., Vol. 71, p. 3338,
1997), benzoxazole metal complex (JP-A-6-33)
No. 6586), a benzothiazole metal complex (Japanese Unexamined Patent Publication No.
279134), trisbenzimidazolylbenzene (US Pat. No. 5,645,948), quinoxaline compounds (JP-A-6-207169), phenanthroline derivatives (JP-A-5-331459), 2-t-butyl-9,10 -N, N'-dicyanoanthraquinone diimine (Phys. Stat. Sol. (A),
142, p. 489, 1994), n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, n-type zinc selenide and the like. The thickness of the electron transport layer 7 is usually 5 to 200 nm, preferably 10 to 100 nm.

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. Furthermore, LiF, Li ₂ O is formed at the interface between the cathode and the light emitting layer or the electron transporting layer.
Inserting an ultrathin film (0.1 to 5 nm) of an alkali metal compound such as an alkaline earth halide or the like is an effective method for improving the efficiency of the device (Appl. Phys. Lett., 7).
0, 152, 1997; IEEE Trans. Electron. Devices
44, 1245, 1997; Japanese Patent Application No. 9-86662). The thickness of the 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, metals such as aluminum, silver, nickel, chromium, gold, platinum and the like are used. It is to 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 on the substrate in this order, as described above. It is also possible to provide the organic electroluminescent device of the present invention between two substrates, at least one of which is highly transparent. Similarly, FIG.
And it is also possible to laminate | stack in the structure opposite to the said each layer structure shown in FIG.

According to the organic electroluminescent device of the present invention, blue light emission with good color purity can be obtained, and not only can it function as a full-color or multi-color blue sub-pixel,
It is also possible to produce a full-color display element by combining with a fluorescence conversion dye (see Japanese Patent Application Laid-Open No. Hei 3-152897).

[0064]

EXAMPLES Next, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the description of the following examples unless it exceeds the gist.

Reference Example 1 A glass substrate was ultrasonically washed with acetone, washed with pure water, ultrasonically washed with isopropyl alcohol, dried with dry nitrogen, and dried.
After performing the V / ozone cleaning, the apparatus was set in a vacuum vapor deposition 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 (I-3) was placed in a ceramic crucible, and heated by a tantalum wire heater around the crucible to perform vapor deposition. At this time, the temperature of the crucible was controlled in the range of 200 to 260 ° C. The degree of vacuum during evaporation
At 1.8 × 10 ^-6 Torr (about 2.3 × 10 ^-4 Pa), the deposition rate is 0.3 nm /
In seconds, a uniform and transparent film having a thickness of 82 nm was obtained. The ionization potential of this thin film sample was measured using an ultraviolet electron analyzer (AC-1) manufactured by Riken Keiki Co., Ltd.
The value of was shown. Mercury lamp (wavelength 350nm)
The maximum of the fluorescence wavelength measured by excitation at 465 nm was blue fluorescence. Further, for the powder sample of the exemplified compound,
Tg showed a high value of 93 ° C. as measured by differential thermal analysis using DSC-20 manufactured by Seiko Instruments Inc. Similarly, ionization potential, fluorescence maximum wavelength, Tg
Are shown in Table-6.

[0066]

[Table 6]

Reference Example 2 As a material for the hole transport layer, the following 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl ( A deposited film was prepared in the same manner as in Reference Example 1 except that H-1) was used as the deposition source.

[0068]

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When the ionization potential of this thin film sample was measured, it showed a value of 5.25 eV.

Reference Example 3 As a material for the hole blocking layer, the following bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum complex (HB-1) was used in place of the exemplary compound (I-3). )
A vapor-deposited film was prepared in the same manner as in Reference Example 1 except that a vapor source was used, and a distyrylbiphenyl derivative (HB-2).

[0071]

Embedded image

[0072]

Embedded image

Table 7 shows the results of measuring the ionization potentials of these thin film samples.

[0074]

[Table 7]

Example 1 An organic electroluminescent device having the structure shown in FIG. 2 was manufactured by the following method. A transparent conductive film of indium tin oxide (ITO) deposited on a glass substrate with a thickness of 120 nm (Geomatec Co., Ltd .; electron beam filmed product; sheet resistance of 15Ω) was fabricated using ordinary photolithography and hydrochloric acid etching.
An anode was formed by patterning into a stripe having a width of mm.
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 performing rough exhaust of the above device by an oil rotary pump,
Evacuation was performed using an oil diffusion pump equipped with a liquid nitrogen trap until the degree of vacuum in the apparatus became 2 × 10 ⁻⁶ Torr (about 2.7 × 10 ⁻⁴ Pa) or less.

As a material for the hole transport layer, 4,4′-bis [N-
(1-Naphthyl) -N-phenylamino] biphenyl (H-
1) was placed in a ceramic crucible, and heated by a tantalum wire heater around the crucible to perform vapor deposition. At this time, the temperature of the crucible was controlled in the range of 250 to 265 ° C. The degree of vacuum at the time of vapor deposition is 1.4 × 10 ^-6 Torr (about 1.9 × 10 ^-4 Pa), and the vapor deposition rate is 0.
A hole transport layer 4 having a thickness of 60 nm was obtained at a rate of 3 nm / sec.

Next, as a material for the light emitting layer 5, the exemplified compound (I-3) was vapor-deposited on the hole transport layer 4 in the same manner. At this time, the temperature of the crucible was controlled in the range of 220 to 260 ° C. The degree of vacuum during vapor deposition is 1.0 × 10 ^-6 Torr (about 1.3x
10 ^-4 Pa) at a deposition rate of 0.1 to 0.2 nm / sec and a film thickness of 30 nm.
Met.

Subsequently, as a material for the hole blocking layer 6, bis (2-methyl-8-quinolinolato) (triphenylsilanolato) aluminum complex (HB-1) was used.
Was deposited in the same manner as above. At this time, the temperature of the crucible was controlled in the range of 180 to 190 ° C. The degree of vacuum during evaporation
1.0 × 10 ^-6 Torr (about 1.3 × 10 ^-4 Pa), deposition rate 0.2nm /
In seconds, the film thickness was 20 nm. Further, as a material of the electron transport layer 7, the following 8-hydroxyquinoline complex (E-1) of aluminum was vapor-deposited on the hole blocking layer 6 in the same manner.

[0079]

Embedded image

At this time, the temperature of the crucible is in the range of 310 to 320 ° C.
Controlled by the box. The degree of vacuum during evaporation is 7.7 × 10^-7Torr (about 1.
0x10^-FivePa) at a deposition rate of 0.3 nm / sec and a film thickness of 25 nm.
Was. Vacuum deposition of the electron transport layer 7 from the hole transport layer 4
The substrate temperature at this time was kept at room temperature. Where electron transport
The element on which the deposition up to the layer 7 has been performed is once placed in the vacuum deposition apparatus.
Take it out into the atmosphere and use it as a mask for cathode deposition.
A mm-wide stripe-shaped shadow mask is
Closely contact the element so that it is perpendicular to the stripe,
Installed in a vacuum evaporation system and the same as the organic layer
2x10 vacuum^-6Torr (about 2.7x10^-FourPa)
I noticed. As the cathode 8, first, magnesium fluoride (Mg
F_Two) Using a molybdenum boat at a deposition rate of 0.01 nm /
Sec, vacuum 2.0x10 ^-6Torr (about 2.7x10^-FourPa), 0.5nm
A film was formed on the electron transport layer 7 with a film thickness. Next, aluminum
The molybdenum boat in the same
 0.6nm / sec, vacuum degree 1.0x10^-FiveTorr (about 1.3x10^-3Pa) with membrane
An aluminum layer having a thickness of 40 nm was formed. Moreover
Copper to increase the conductivity of the cathode, as well as molybdenum
Heating with a vacuum pump, deposition rate 0.6nm / sec, vacuum
Degree 8.0x10^-6Torr (about 1.1x10^-3Pa) to form a 40nm thick copper layer
Thus, the cathode 8 was completed. Above deposition of three-layer cathode 8
The substrate temperature at that time was kept at room temperature.

As described above, an organic electroluminescent device having a light emitting area of 2 mm × 2 mm was obtained. Table 8 shows the light emission characteristics of this device. In Table 8, the emission luminance is a value at a current density of 250 mA / cm ² , and the emission efficiency is 100 cd
The value at / m ² , the luminance / current indicates the slope of the luminance-current density characteristic, and the voltage indicates the value at 100 cd / m ² . EL spectrum peak maximum wavelength and CIE chromaticity coordinate value (JIS Z8701)
Are also shown. The emission color was blue. This device did not show a remarkable rise in drive voltage even after storage for a long period of time, and did not decrease in luminous efficiency or luminance, and stable storage stability of the device was obtained.

[0082]

[Table 8]

Examples 2 to 5 Illustrative compounds (I-5), (I-10), (I
-27) and (I-28) were each used in the same manner as in Example 1 except that Exemplified Compound (I-3) was used instead.
Table 8 shows the light emission characteristics of each element.

Example 6 A distyrylbiphenyl derivative (HB-
An element was fabricated in the same manner as in Example 3, except that 2) was used. Table 8 shows the emission characteristics of the device.

Example 7 Example 1 was repeated except that the compound (I-27) was used as a light emitting layer, and that perylene was uniformly doped in a thickness direction at a concentration of 1.2% by weight in the light emitting layer by a binary vapor deposition method. A device was produced in the same manner as described above. Table 8 shows the light emission characteristics of this device. Due to the perylene doping, the chromaticity coordinates completely entered the blue region.

Comparative Example 1 An element was produced in the same manner as in Example 4 except that the hole blocking layer was not provided and the thickness of the electron transport layer was changed to 45 nm. Table 8 shows the light emission characteristics of this device. Blue light emission was not obtained, and green light emission from the 8-hydroxyquinoline complex of aluminum used as the electron transport layer was observed.

Comparative Example 2 An element was produced in the same manner as in Example 4 except that the hole transport layer was not provided and the thickness of the light emitting layer was changed to 60 nm. Table 8 shows the light emission characteristics of this device. The emission luminance was very low.

Comparative Example 3 Bis (2-methyl-8-quinolinolato) (p-phenylphenolato) aluminum complex (ionization potential: 5.35 eV) (B-2) having a thickness of 45 nm was used as a light emitting layer, and electron transport was performed. A device was produced in the same manner as in Example 3, except that 30 nm of (E-1) was used as the layer. Table 8 shows the light emission characteristics of this device. Both the luminance and the luminous efficiency were low, and the luminescent color was bluish green.

[0089]

According to the organic electroluminescent device of the present invention, it is possible to obtain blue light with good color purity and to obtain a device with improved stability because of having a light emitting layer having a specific ionization potential. Can be. Accordingly, the organic electroluminescent device according to the present invention can be used as a flat panel display (for example, for an OA computer or a wall-mounted television), a multi-color display device, or a light source (for example, a light source of a copier, a liquid crystal display) utilizing a feature as 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 cross-sectional view showing an example of an organic electroluminescent device.

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

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

[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

Claims (8)

[Claims] 1. An organic electroluminescent device comprising at least a hole transport layer, a light emitting layer and a hole blocking layer sandwiched between an anode and a cathode on a substrate, wherein the light emitting layer contains an aromatic amine compound. An organic electroluminescent device, wherein the ionization potential of the hole transport layer is 0.1 eV or more greater than the ionization potential of the light emitting layer, and the ionization potential of the hole blocking layer is 0.2 eV or more greater than the ionization potential of the light emitting layer. 2. The organic electroluminescent device according to claim 1, wherein the light emitting layer contains an aromatic amine having a tertiary nitrogen atom having at least one condensed aromatic ring group as a substituent. 3. The organic electroluminescent device according to claim 2, wherein the light emitting layer contains an aromatic amine compound represented by the following general formula (I). Embedded image (In the formula, X represents a divalent aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent, and Ar ^{1 to} A ¹
r ⁴ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent, and X and Ar ¹
At least one of Ar ⁴ to Ar ⁴ is selected from a condensed aromatic ring group. ) 4. The organic electroluminescent device according to claim 1, wherein the light emitting layer contains an aromatic amine compound represented by the following general formula (II). Embedded image (Wherein, Y is selected from a nitrogen atom or a benzene ring bonded at the 1,3,5-position, and Ar ⁵ and Ar ⁶ are each an aromatic hydrocarbon ring group or an aromatic group which may have a substituent. Represents a group heterocyclic group.) 5. The hole transport layer contains an aromatic amine compound different from that of the light emitting layer.
The organic electroluminescent device according to any one of the above. 6. A metal complex represented by the following general formula (III) or (IV), a triazole derivative containing at least one structural formula (V):
The organic electroluminescent device according to any one of claims 1 to 5, comprising at least one compound of a styryl compound represented by the following formula: Embedded image (Wherein, R ^{1 to} R ⁶ each 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, a carboxyl group, an alkoxy group, an alkyl group, A sulfonyl group, an α-haloalkyl group, a hydroxyl group, an amide group optionally having a substituent, an aromatic hydrocarbon ring group optionally having a substituent or an aromatic heterocyclic group optionally having a substituent M represents an Al atom or a Ga atom;
L is represented by any of the following general formulas (IIIa), (IIIb), and (IIIc). ) (In the formula, Z represents any atom of Si, Ge, and Sn, and Ar ^{9 to} Ar ¹⁰ represent an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent. ) (Wherein, R ^{1 to} R ⁶ each 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, a carboxyl group, an alkoxy group, an alkyl group, Represents a sulfonyl group, an α-haloalkyl group, a hydroxyl group, an amide group which may have a substituent, an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent, and M is Al
Represents an atom or a Ga atom. ) Embedded image (In the formula, Ar ¹² represents a divalent aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent, and Ar ¹³ to
Ar ¹⁶ represents an aromatic hydrocarbon ring group or an aromatic heterocyclic group which may have a substituent. ) 7. The organic electroluminescent device according to claim 1, wherein an electron transport layer is provided between the hole blocking layer and the cathode. 8. The organic electroluminescent device according to claim 1, wherein the thickness of the hole blocking layer is in the range of 0.5 to 30 nm.