JP2000239291A - Metal-complex compound and organic electroluminenscent element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject element useful for flat-panel displays or multicolor displays or the like, capable of being driven at a high emission efficiency and of maintaining steady emission characteristics for a long time, by including a layer having a specific metal-complex compound. SOLUTION: This element is obtained by including a layer having a metal- complex compound of formula I [R1 to R6 are each H, a halogen or a (substituted) alkyl or the like; R7 to R9 are each a (substituted) alkyl, a (substituted) aralkyl, a (substituted) alkenyl or the like, and have no possibility of being the same group; M is Al or Ga] [e.g. bis(2-methyl-8-quinolinolato) (diphenylmethylsilanolato)aluminum]. The compound of formula I is obtained, for example, by reacting the compound of formula III produced by hydrolyzing a compound of formula II (e.g. a diphenylmethylchlorosilane) in the presence of aniline, with a compound of formula IV (e.g. 2-methyl-8-hydroxyquinoline) and a metal alkoxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal complex compound and an organic electroluminescent device, and more particularly, to a metal complex compound having a specific structure and an organic electroluminescent device having a layer containing the organic compound. It relates to an element.

[0002]

2. Description of the Related Art Conventionally, as a thin film type electroluminescent (EL) element, an inorganic II-VI compound semiconductor such as Zn
It is generally known that S, CaS, SrS, or the like is doped with Mn or a rare earth element (Eu, Ce, Tb, Sm, or the like) as an emission center. However, EL elements made from such inorganic materials are useful as such, but they require (1) AC drive (50 to 1000 Hz), (2) high drive voltage (up to 200 V), and (3) Further improvement in performance is demanded because it is difficult to achieve full color (particularly blue) and (4) the cost of the peripheral drive circuit is high.

[0003] In recent years, in order to improve the above problems, EL devices using organic thin films have been developed. In particular, in order to increase the luminous efficiency, optimize the type of electrode to improve the efficiency of carrier injection from the electrode,
Development of an organic electroluminescent device provided with a hole transporting layer composed of an aromatic diamine and a light emitting layer composed of an aluminum complex of 8-hydroxyquinoline (Appl. Phys. Lett., 51, 913)
(1987, p. 1987), the luminous efficiency has been greatly improved as compared with a conventional EL device using a single crystal such as anthracene. Also, 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., 65)
Vol. 3610, 1989), improvement of luminous efficiency and conversion of luminous wavelength are also performed.

In addition to the electroluminescent device using a low molecular material as described above, poly (p-phenylenevinylene) and poly [2-methoxy-5- (2-ethylhexyloxy)- Development of electroluminescent devices using polymer materials such as 1,4-phenylenevinylene] and poly (3-alkylthiophene), and mixing of low-molecular light-emitting materials and electron transfer materials with polymer materials such as polyvinylcarbazole Devices are also being developed.

Recently, an electroluminescent device having an electron transporting layer (light emitting layer) comprising an aluminum complex in which a substituted 8-hydroxyquinoline and a silanol group are bonded to aluminum is disclosed in US Pat. No. 5,484,922. It is described that it has excellent performance.

[0006]

One of the major problems in applying the organic electroluminescent device to the field of flat panel displays is to improve the luminous efficiency. In application to a display device of a portable device, low power consumption is particularly important. In addition, in the application to a small character display element, a simple matrix driving method is mainly employed. In this method, it is necessary to illuminate the element with a high duty ratio at a high luminance in an extremely short time. It has been pointed out that the power luminous efficiency is reduced due to the increase (LCD Intelligence, Monthly, 1997, 5
Monthly, p. 84).

Further, in order to apply an organic electroluminescent device to a full-color or multi-color flat panel display, high color purity is required. However, in the conventional organic electroluminescent device, especially, the color purity of the blue device is insufficient, and therefore, the improvement has been required.

For example, the organic electroluminescent device using the aluminum complex compound described in the above-mentioned US Pat. No. 5,484,922 is known from the present inventors to be capable of emitting light when applied to a full-color or multi-color panel. The efficiency and color purity seem to be insufficient.

Compounds used in blue organic electroluminescent devices include anthracene, tetraphenylbutadiene, pentaphenylcyclopentadiene, distyrylbenzene derivatives, oxadiazole derivatives, azomethine zinc complexes, and benzazole metal complexes (Japanese Patent Application Laid-open No. 8-814
No. 72), mixed ligand type aluminum complex (J. SID,
5, p. 11, 1997), N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-biphenyl-4,4'-diamine, polyvinylcarbazole, 1,2, 4-triazole derivative, aminopyrene dimer, distyrylbiphenyl derivative (App
l. Phys. Lett., 67, 3853, 1995), silole derivatives and the like.

[0010] Among the above blue light-emitting materials, representative compounds whose element characteristics are well studied include the following compounds.

[0011]

Embedded image It has been reported that the distyrylbiphenyl derivative (B-1) has high fluorescence intensity and does not form an exciplex even when used in a device, and emits blue light (Appl. Phys. Lett.,
67, p. 3853, 1995), the ionization potential in the thin film state is as high as 5.9 eV, it is difficult to inject holes from the hole transport layer, and the EL spectrum has a broad peak with a light emission maximum near 480 nm. Therefore, it is hard to say that it is advantageous for improving the color purity of blue. This color purity does not seem to be improved by doping. Bis (2-methyl-8-quinolinolato) (p-phenylphenolato) aluminum complex (B-2) also has insufficient blue color purity, and the color purity is improved by doping perylene, It seems that the stability has not yet reached a practical level (JP-A-5-198377). N, N'-diphenyl-N, N '-(3-methylphenyl) -1,1'-biphenyl-4,4'-diamine which is an aromatic diamine (usually "TP
(D-3) (B-3) shows an EL spectrum having an emission peak at 464 nm when combined with a triazole derivative as a hole blocking layer (Jpn.J. Appl. Phy.
s., 32, L917, 1993), and the Tg of TPD is as low as 63 ° C., which is disadvantageous in terms of thermal stability such as crystallization.

The fact that the luminous efficiency, heat resistance, driving characteristics and blue purity of the organic electroluminescent device are not improved is undesirable characteristics as a display device such as a flat panel display aiming at full color.

SUMMARY OF THE INVENTION <Summary> In view of the above circumstances, the present invention provides a metal complex compound and an organic electroluminescent device which can be driven with high luminous efficiency and can maintain stable luminescent characteristics for a long period of time. It is an object of the present invention to provide a metal complex compound having a specific ligand introduced therein and an organic electroluminescent device using the same.

[0014]

That is, an organic electroluminescent device according to the present invention is characterized by having a layer containing a metal complex compound represented by the following general formula (I).

[0015]

Embedded image (Wherein, R ^{1 to} R ⁶ are each independently a hydrogen atom,
Halogen atom, alkyl group, aralkyl group, alkenyl group, alkynyl group, cyano group, amino group, amide group, nitro group, acyl group, alkoxycarbonyl group, carboxyl group, alkoxy group, alkylsulfonyl group, hydroxyl group, aromatic hydrocarbon Represents a group or an aromatic heterocyclic group. R ¹ and R ² or R ² and R ³ may be bonded to form a ring, and any one of R ^{1 to} R ⁶ may be an alkyl group, an aralkyl group, or an alkenyl group. An alkynyl group, a secondary or tertiary amino group, an amide group, an acyl group,
When it represents an alkoxycarbonyl group, an alkoxy group, an alkylsulfonyl group, an aromatic hydrocarbon group or an aromatic heterocyclic group, these may further have a substituent in the hydrocarbon moiety. R ^{7 to} R ⁹ are each independently
Which may have a substituent, an alkyl group, an aralkyl group, an alkenyl group, an alkynyl group, a cyano group, an amino group, an amide group, a nitro group, an alkoxycarbonyl group, a carboxyl group, an alkoxy group, an alkylsulfonyl group,
It represents an aromatic hydrocarbon group or an aromatic heterocyclic group, R ⁷ ~
R ⁹ cannot all be the same group. M represents an Al atom or a Ga atom. The present invention also relates to a specific metal complex compound, and the metal complex compound is represented by the following general formula (II).

[0016]

Embedded image (In the formula, R ¹ represents a methyl group or an ethyl group, R ⁷
To R ⁹ are each independently a methyl group, an ethyl group, a branched alkyl group having 3 to 6 carbon atoms or —AR ¹⁰ (A is a direct bond or an alkylene group having 1 to 4 carbon atoms, and R ¹⁰ is Represents an aromatic hydrocarbon group having 6 to 12 carbon atoms, which may be substituted with an alkyl group of 1 to 3 or a dialkylamino group). R ^{7 to} R ⁹ are not all the same group. )

<Effects> According to the organic electroluminescent device of the present invention, since it has a layer containing a specific compound, blue luminescence can be achieved due to high luminous efficiency and color purity, and thermal stability can be achieved. A device with good quality can be obtained.

Therefore, the organic electroluminescent device according to the present invention can be used as a light source (for example, 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.
It can be applied to light sources for copiers, backlight sources for liquid crystal displays and instruments, display boards, and sign lamps.
As an in-vehicle or outdoor display element requiring high heat resistance, its technical value is great.

[0019]

DETAILED DESCRIPTION OF THE INVENTION [Metal Complex Compound of General Formula (I)] The metal complex compound used in the present invention is represented by the general formula (I). In the general formula (I), the details of the substituents represented by R ^{1 to} R ⁶ are as follows. Examples of the halogen atom represented by R ^{1 to} R ⁶ include a chlorine atom, a bromine atom and an iodine atom. Examples of the alkyl group include an alkyl group having 1 to 10 carbon atoms,
Preferable examples include a methyl group, an ethyl group, and a tertiary butyl group. Examples of the alkoxy group include an alkoxy group having 1 to 7 carbon atoms, preferably a methoxy group and an ethoxy group. Examples of the alkoxycarbonyl group include an alkoxycarboxyl group having an alkyl group having 1 to 7 carbon atoms, preferably a methoxycarbonyl group and an ethoxycarbonyl group. Examples of the aralkyl group include an aralkyl group in which the allyl moiety is a phenyl group and the alkyl moiety has about 1 to 4 carbon atoms, preferably a benzyl group, a phenethyl group, a phenylpropyl group, a diphenylmethyl group and the like. As the alkenyl group,
For example, a lower alkenyl group having 2 to 10 carbon atoms, preferably a vinyl group, an allyl group and the like can be mentioned. Examples of the alkynyl group include a lower alkenyl group having 2 to 10 carbon atoms,
Preferable examples include an ethynyl group and a propynyl group. Examples of the acyl group include those derived from a monocarboxylic acid having 1 to 4 carbon atoms or benzenecarboxylic acid, preferably a formyl group, an acetyl group, a propionyl group, a benzoyl group and the like. As the aromatic hydrocarbon group, a phenyl group, a biphenyl group, a naphthyl group and the like are preferably mentioned. Examples of the aromatic heterocyclic group include a pyridyl group, a quinolyl group, a thienyl group, and a carbazolyl group.
As the secondary or tertiary amino group, for example, those having 1 to 7 carbon atoms
Having an alkyl group or an aryl group, preferably a methylamino group, an ethylamino group, a dimethylamino group, a diethylamino group, a diphenylamino group and the like. Examples of the amide group include an acetylamino group, and examples of the alkylsulfonyl group include a methylsulfonyl group.

The above R¹~ R⁶Carbonization of the substituent represented by
Other substituents may be further bonded to the hydrogen moiety.
Such as a halogen atom, a hydroxyl group, an alcohol
Xy group, aryloxy group, aromatic hydrocarbon group, aromatic
And a heterocyclic group. Those having substituents are preferred
Specific examples include a chloromethyl group and phenyl
Examples include an ethynyl group and a methoxyphenyl group. Ma
R¹~ R⁶Is an aralkyl group or an aromatic carbonized
If it is a hydrogen group or an aromatic heterocyclic group,
Substituents bonded to these groups may be other than those described above.
Examples include alkyl groups and primary to tertiary amino groups.
You. Also, R¹And R^Two And R^TwoAnd R ^ThreeAnd join
To form a ring. Typical examples of such things
Is R¹And R ^Two And (or R^TwoAnd R^ThreeAnd)
Those forming a 6-membered ring, especially a benzene ring
Can be

Of the groups listed as R ^{1 to} R ⁶ ,
More preferably, R ¹ is any of an amino group, an alkyl group or an alkoxy group, and R ² and R ³ are any of an amino group, an alkyl group, an alkoxy group or a hydrogen atom. R ^{4 to} R ⁶ represent a hydrogen atom, a cyano group, a nitro group, a halogen atom, an amino group, an alkyl group, an alkoxy group, an alkyl group or an alkoxy group optionally substituted with a halogen atom (that is, preferably α -Haloalkyl group, α-haloalkoxy group), amide group, alkylsulfonyl group, carboxyl group or alkoxycarbonyl group.

In the general formula (I), R ^{7 to} R ⁹ are an alkyl group, an aralkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a secondary or tertiary amino group, an amide group, an alkoxycarbonyl group, an alkylsulfonyl group, When it represents an aromatic hydrocarbon group or an aromatic heterocyclic group, these represent the same as those described above for R ^{1 to} R ⁶ . Examples of the substituent further substituting the same as those described above with respect to the substituents bonded to R ^{1 to} R ⁶ . Among them, as R ^{7 to} R ⁹ , an alkyl group, an amino group, an alkoxy group, an aromatic hydrocarbon group, or an aromatic heterocyclic group is preferable. R ^{7 to} R ⁹ may not all be the same group,
^At least one of ^{7 to} R ⁹ is preferably an aromatic hydrocarbon group or an aromatic heterocyclic group, and more preferably two are an aromatic hydrocarbon group or an aromatic heterocyclic group. The aromatic hydrocarbon group preferably has 6 to 20 carbon atoms. In the general formula (I), R ^{7 to} R ⁹ are preferably a somewhat bulky group. Therefore, when the group is an alkyl group, an alkoxy group, or the like, a branched group is preferable to a linear group. M represents an Al atom or a Ga atom, preferably an Al atom.

[0023] Preferred as the metal complex compound used in the present invention, in the above general formula (I), R ¹ is an amino group, an alkyl group or an alkoxy group, R ²
And R ³ are each independently an amino group, an alkyl group,
An alkyl group or an alkoxy group, an amide group, or an alkyl group, wherein R ^{4 to} R ⁹ are each independently substituted with a cyano group, a nitro group, a halogen atom, an amino group, or a halogen atom; A sulfonyl group, a carboxyl group, an alkoxycarbonyl group or a hydrogen atom, and each of R ^{7 to} R ⁹ is independently an alkyl group, an amino group, an alkoxy group, an aromatic hydrocarbon group or an aromatic heterocyclic group. is there.

Particularly preferred metal complex compounds are those represented by the general formula (II). The compound of the general formula (I) is prepared by, for example, hydrolyzing a compound represented by the general formula (III) in the presence of aniline (J. Am. Chem. Soc., 8).
1, 2359, 1959) to give a compound represented by the general formula (IV), and reacting the compound with a quinoline compound represented by the general formula (V) and a metal alkoxide.

Embedded image The following are preferred specific examples of the compound represented by the general formula (I). These are examples and thus are not limiting.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

[0028]

[Table 4]

[0029]

[Table 5]

[0030]

[Table 6]

[0031]

[Table 7]

[0032]

[Table 8]

[0033]

[Table 9]

[0034]

[Table 10]

[0035]

[Table 11]

[0036]

[Table 12]

[0037]

[Table 13]

[0038]

[Table 14]

[0039]

[Table 15]

[0040]

[Table 16] Each of the above compounds has a high fluorescence intensity, a high luminous efficiency and a high color purity in a dispersed state, and is hardly crystallized. This is considered to be due to the asymmetric structure of the cyanol moiety of the complex and the low symmetry of the structure. It is considered that such a compound and its effect have not been known before. These compounds may be used alone, or may be used as a mixture as necessary.

<Organic Electroluminescent Device> The organic electroluminescent device according to the present invention is characterized by having a layer containing the metal complex compound represented by the general formula (I).
Here, “comprising” means that the layer is composed of only the metal complex compound of the general formula (I), and the metal complex compound of the formula (I) and a metal complex compound other than the metal complex compound. Also means those consisting of various components or compounds. Representative of such purposeful components or compounds are, for example, various fluorescent dyes (described in detail below). In addition, “having” in the above refers to the general formula (I)
Has at least one layer containing the metal complex compound represented by Accordingly, the organic electroluminescent device according to the present invention includes a device having a multilayer structure including the layer and other layers. Further, the present invention also encompasses a structure in which a plurality of layers including the metal complex compound of the general formula (I) are stacked.

FIG. 1 is a cross-sectional view schematically showing a typical example of the structure of such an organic electroluminescent device according to the present invention. The organic electroluminescent device has a light emitting layer sandwiched between an anode and a cathode on a substrate. An element, wherein the light-emitting layer has a general formula (I)
This is a preferred example of an organic electroluminescent device containing the metal complex compound represented by the following formula. 1 is a substrate, 2
Represents an anode, 4 represents a hole transport layer, 5 represents a light emitting layer, 6 represents an electron transport layer, and 7 represents a cathode.

The substrate 1, the anode 2, the hole transport layer 4, the electron transport layer 6, and the cathode 7 may be any of those conventionally used in this type of EL device. Preferred in the present invention are as follows.

The substrate 1 serves as a support for the organic electroluminescent device, and for example, a quartz or glass plate, a metal plate or a metal foil, a plastic film or a sheet, or the like is used.
Especially glass plate, polyester, polymethacrylate,
A transparent synthetic resin plate such as polycarbonate or polysulfone is preferred. In addition, in order to improve the durability of the organic electroluminescent device according to the present invention, for example, in order to prevent performance deterioration due to outside air, moisture, heat, etc., various suitable materials or layer configurations may be added. For example, a method in which a dense silicon oxide film or the like is provided on at least one surface of the substrate to ensure gas barrier properties is also one of the preferable methods. This is particularly useful when a synthetic resin having insufficient gas barrier properties is used as the substrate.

An anode 2 is provided on a substrate 1. The anode 2 plays a role of injecting holes into the hole transport layer 4. The anode is typically made of a metal such as aluminum, gold, silver, nickel, palladium, platinum, indium and / or
Alternatively, it is composed of a metal oxide such as a tin oxide, a metal halide such as copper iodide, carbon black, or a conductive polymer such as poly (3-methylthiophene), polypyrrole, or polyaniline. The formation of the anode 2 is usually performed by a sputtering method, a vacuum evaporation method, or the like in many cases. In the case of fine metal particles such as silver, fine particles such as copper iodide, carbon black, conductive metal oxide fine particles, and conductive polymer fine powder, these fine particles are dispersed in an appropriate binder resin solution. In this state, the anode 2 can be formed by coating on the substrate 1. Furthermore, 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 as a laminate of 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, and in this case, the thickness is usually 5 to 1000 nm.
Degree, preferably 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.

The hole transport layer 4 is provided on the anode 2. As a condition required for the material of the hole transport layer, it is necessary that the material has a high hole injection efficiency from the anode 2 and can efficiently transport the injected holes. For that, the ionization potential is small,
It is required that the material has high transparency to visible light, high hole mobility, excellent 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 further required to have heat resistance. Therefore, as Tg
A material having a value of 85 ° C. or more is desirable.

Examples of such a hole transport material include 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane, 4,4′-bis [N- (1-naphthyl) -N- Phenylamino] aromatic amines containing two or more tertiary amines represented by biphenyl and having two or more condensed aromatic rings substituted with nitrogen atoms (JP-A-5-234681), and derivatives of triphenylbenzene Aromatic triamines having a starburst structure (US Pat. No. 4,923,774), N, N′-diphenyl-N, N′-bis (3-methylphenyl) biphenyl-4,
Compounds in which a pyrenyl group is substituted with a plurality of aromatic diamino groups, such as 4'-diamine, aromatic diamines having a styryl structure (JP-A-4-290851), and aromatic tertiary amine units linked by a thiophene group (JP-A-4-304466)
JP-A-5-239455), a starburst type aromatic triamine (JP-A-4-308688), a tertiary amine linked by a fluorene group (JP-A-5-25473), and a triamine compound (JP-A-5-239455) ), Bisdipyridylaminobiphenyl, N, N, N-triphenylamine derivatives (JP-A-6-1972), aromatic diamines having a phenoxazine structure (JP-A-7-138562), diaminophenylphenanthridine Derivatives (JP-A-7-252474), silazane compounds (US Pat. No. 4,950,950), silanamine derivatives (JP-A-6-49079),
And phosphamine derivatives (JP-A-6-25659). These compounds may be used alone,
If necessary, they may be mixed and used.

In addition to the above compounds, materials for the hole transport layer 4 include polyvinyl carbazole, polysilane, polyphosphazene (JP-A-5-310949), polyamide (JP-A-5-310949), and polyvinyl triphenyl. Polymer materials such as amines (JP-A-7-53953), polymer materials having a triphenylamine skeleton (JP-A-4-1303065), and polymethacrylates containing aromatic amines are exemplified. The hole transport layer 4 can be 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 or two or more hole transporting materials and, if necessary, additives such as a binder resin which does not trap holes and a coating property improving agent are added.
The solution is dissolved to prepare a coating solution, applied to the anode 2 by a method such as spin coating, and dried to form the hole transport layer 3b. As the binder resin, polycarbonate,
Examples include polyarylate and polyester. If the amount of the binder resin is large, the hole mobility is reduced, so that 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 placed 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, and the hole transport layer 4 is formed on the substrate 1 on which the anode is formed, which is placed facing the crucible.
Is formed.

The thickness of the hole transport layer 4 is usually 10 to 300 n
m, preferably 30-100 nm. In order to uniformly form such a thin film, a vacuum deposition method is generally used.

The light emitting layer 5 is formed on the hole transport layer 4. The light-emitting layer 5 is excited by recombination between holes injected from the anode and traveling through the hole transport layer and electrons injected from the cathode and traveling through the electron transport layer 6 between the electrodes to which an electric field is applied. Formed from a compound that emits strong light.

In general, the compound used in the light emitting layer 5 is a compound having a stable and uniform thin film shape, exhibiting a high fluorescence yield in a solid state, and capable of efficiently transporting holes and / or electrons. Specifically, a fluorescent material is effective. It is also electrochemically and chemically stable,
It is required that the impurities serving as traps are compounds that hardly occur during production or use.

The compound represented by the general formula (I) according to the present invention conforms to these required characteristics and can form an excellent light emitting layer. These may be used alone or in combination with a known fluorescent material. Known fluorescent materials include, for example, aromatic compounds such as tetraphenylbutadiene (JP-A-57-51781) and metal complexes such as aluminum complex of 8-hydroxyquinoline (JP-A-59-51781).
194393), a metal complex of 10-hydroxybenzo [h] quinoline (JP-A-6-322362), a mixed-ligand aluminum chelate complex (JP-A-5-198377,
JP-A-5-198378, JP-A-5-214332, JP-A-6-172751), cyclopentadiene derivative (JP-A-2-289675), perinone derivative (JP-A-2-289676), Oxadiazole derivatives (JP-A-2-217679), bisstyrylbenzene derivatives (JP-A-245087, JP-A-2-222484), and perylene derivatives (JP-A-2-189890, 3-791) Coumarin compound (JP-A-2-191694, JP-A-2-191694)
-792, a rare earth complex (JP-A-1-256584), a distyrylpyrazine derivative (JP-A-2-252793), a p-phenylene compound (JP-A-3-33183), a thiadiazolopyridine Derivative (JP-A-3-37292)
JP, JP-A-3-37293), naphthyridine derivative (JP-A-3-203982), silole derivative (The 70th Annual Meeting of the Chemical Society of Japan, 2D)
102 and 2D103, 1996). Also,
Among the compounds that can be used in the above-described hole transport layer, an aromatic amine compound having fluorescence can be used together with the compound of the present invention.

The thickness of the light emitting layer 5 is usually 10 to 200 nm, preferably 30 to 100 nm. The light emitting layer 5 is formed by laminating on the hole transport layer 4 by a coating method or a vacuum deposition method in the same manner as the hole transport layer 4. It is necessary to use a solvent that does not dissolve the hole transport layer.

In order to improve the luminous efficiency of blue light, the color purity, and the driving life of the device, the compound represented by the general formula (I) is used as a host material in the light-emitting layer. Doping with a dye is an effective method. As a doped dye having blue fluorescence,
Condensed polycyclic aromatic rings such as perylene (JP-A-5-198377), coumarin derivatives, naphthalimide derivatives (JP-A-4-320486), and aromatic amine derivatives (JP-A-8-1983)
-199162). The proportion of these doped dyes in the host material is
Preferably it is in the range of 0.1 to 10% by weight.

The compound of the present invention has a feature that it has good color purity especially when used for a blue device, but it is of course possible to obtain a green device or a red device by doping a green or 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 each of the above dopants is doped in the light emitting layer, it is usually doped uniformly in the thickness direction of the light emitting layer. However, 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, may be doped near the interface with the electron transport layer.

The electron transport layer 6 is provided on the light emitting layer 5. The electron transport layer 6 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 and efficiently performing recombination with holes. .

The electron transporting compound used in the electron transporting layer 6 has a high electron injection efficiency from the cathode 7 and
It is necessary that the compound has high electron mobility and can efficiently transport injected electrons.

As a material satisfying such conditions, 8
Metal complexes such as aluminum complexes of -hydroxyquinoline (JP-A-59-194393);
[h] quinoline metal complex, oxadiazole derivative, distyrylbiphenyl derivative, silole derivative, 3- or
5-hydroxyflavone metal complex, benzoxazole metal complex, benzothiazole metal complex, 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'-dicyanoanthraquinonediimine,
Examples include n-type hydrogenated amorphous silicon carbide, n-type zinc sulfide, and n-type zinc selenide. The thickness of the electron transport layer 6 is
Usually, it is 5 to 200 nm, preferably 10 to 100 nm.

The electron transporting layer 6 is laminated on the light-emitting layer 5 by a coating method or a vacuum deposition method in the same manner as the hole transporting layer 4, but usually, a vacuum deposition method is used.

The cathode 7 plays a role of injecting electrons into the electron transport layer 6. As the material used for the cathode 7, 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. In addition, LiF, Mg
Inserting an ultra-thin insulating film (0.1 to 5 nm) such as F ₂ or Li ₂ O is also an effective method for improving the efficiency of the device (Appl.
Phys. Lett., 70, 152, 1997; JP-A-10-74586
Issue; IEEETrans. Electron. Devices, 44, 1245
P. 1997). The thickness of the cathode 7 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, silver, copper, nickel, chromium, gold,
A metal such as platinum is used.

As shown in FIG. 2, in order to lower the driving voltage of the device and to improve the driving stability, in order to improve the contact between the anode 2 and the hole transport layer 4, the anode buffer layer 3 is required. It is preferred to provide. 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 glass transition temperature are high, and the melting point is 3
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. For this purpose, porphyrin derivatives and phthalocyanine compounds (JP-A-63-295695) and star-bust-type aromatic triamines (JP-A-4-3069) have been used.
No. 8688), hydrazone compounds, alkoxy-substituted aromatic diamine derivatives, p- (9-anthryl) -N, N-di-p-tolylaniline, polythienylenevinylene, poly-p-phenylenevinylene, polyaniline and the like. Organic compounds, sputtered carbon films, and metal oxides such as vanadium oxide, ruthenium oxide, and molybdenum oxide have 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 compounds include the following compounds.

Porphine 5,10,15,20-tetraphenyl-21H, 23H-porphine 5,10,15,20-tetraphenyl-21H, 23H-porphineCobalt (II) 5,10,15,20-tetraphenyl -21H, 23H-porfin copper (I
I) 5,10,15,20-Tetraphenyl-21H, 23H-porphine zinc (II) 5,10,15,20-Tetraphenyl-21H, 23H-porphine vanadium (IV) oxide 5,10,15,20 -Tetra (4-pyridyl) -21H, 23H-porphine 29H, 31H-Phthalocyanine Copper (II) phthalocyanine Zinc (II) phthalocyanine Titanium phthalocyanine oxide Magnesium phthalocyanine Lead phthalocyanine Copper (II) 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, 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 also possible to laminate the structure opposite to that of FIG. 1, that is, to stack the cathode 7, the electron transport layer 6, the light emitting layer 5, the hole transport layer 4, and the anode 2 in this order on the substrate. As described above, it is also possible to provide the organic electroluminescent device of the present invention between two substrates, at least one of which has high transparency. Similarly, it is also possible to laminate in a structure opposite to the above-mentioned respective layer constitutions shown in FIG.

The metal complex compound according to the present invention used in the light emitting layer 5 has an electron transporting property. If the light emitting layer itself has a sufficient electron transporting property, the electron transporting layer 6 is omitted. Can be. Therefore, FIG.
As shown in the above, it is also possible to form an organic electroluminescent device with a layer structure of substrate 1 / anode 2 / hole transport layer 4 / light emitting layer 5 / cathode 7.

According to the organic electroluminescent device of the present invention,
Since a compound having a specific skeleton having a high melting point is used for the light-emitting layer, the heat resistance of the element is improved, and blue light emission with good color purity can be obtained. As a full-color or multi-color blue sub-pixel, In addition to functioning, it is also possible to produce a full-color display element by combining with a fluorescent conversion dye (Japanese Patent Laid-Open No. 3-152897).

[0073]

The following examples are provided to further illustrate the present invention. Therefore, the present invention is not limited only to the specific description of the following Examples unless it exceeds the gist.

Example 1 Synthesis of bis (2-methyl-8-quinolinolato) (diphenylmethylsilanolato) aluminum (compound (1)); 1.1 g (12 mmol) of aniline and 0.1 ml of demineralized water in 15 ml of ether.
3 g and a small amount of acetone were added, cooled to 0 ° C. or lower, and stirred. To this solution, a solution of 2.9 g (12.5 mmol) of diphenylmethylchlorosilane dissolved in 9 ml of dry ether was added, and the mixture was stirred at 0 ° C. or lower for 3.5 hours. The reaction solution was filtered, the filtrate was collected, the organic layer was separated, and the solvent was removed to obtain 1.04 g (yield 39%) of diphenylmethylsilanol as a light brown liquid. Subsequently, 1.55 g of 2-methyl-8-hydroxyquinoline was added to 22 ml of dry toluene under a nitrogen atmosphere.
(9.7 mmol) and 1.07 g of aluminum isopropoxide
(5.2 mmol) was added and dissolved by stirring at room temperature for 10 minutes.
To this solution was added dropwise a solution prepared by dissolving 1.04 g (4.8 mmol) of diphenylmethylsilanol prepared above in 9 ml of dry toluene. Then, the mixture was refluxed for 3 hours with stirring, and allowed to cool. The precipitate formed is filtered off and dried to give milky crystals
1.22 g were obtained. When 1.17 g of these crystals were purified by sublimation, 1.00 g of milky white crystals were obtained. The melting point was measured and found to be 231 ° C. This had a molecular weight of 556 as determined by mass spectrometry and was confirmed to be Compound (1).

[0075]

Embedded image The FT-IR spectrum of this compound was as shown in FIG. In addition, in the fluorescence measurement of this compound in a solid state, the excitation of the compound was measured using a mercury lamp (wavelength: 350 nm). As a result, the maximum fluorescence wavelength (λmax) was 484 nm, and blue fluorescence was exhibited. The band gap of this compound determined from the light absorption edge was 2.74 eV, and the ionization potential determined using an atmospheric photoelectron spectrometer ("AC-1") manufactured by Riken Keiki was 5.40 eV.

Example 2 Synthesis of bis (2-methyl-8-quinolinolato) (tert-butyldiphenylsilanolato) aluminum (compound (23)); aniline 2.1 g (22 m
mol), 0.6 g of demineralized water and a small amount of acetone were added, and the mixture was cooled to 0 ° C. or lower and stirred. To this solution was added tert-butyldiphenylchlorosilane 5.5 dissolved in 10 ml of dry ether.
g (22 mmol) solution, and the mixture was stirred at 0 ° C. or lower for 5 hours. The reaction solution was filtered, the filtrate was collected, the organic layer was separated, and the solvent was removed to obtain 5.1 g of tertiary butyl diphenylsilanol (90% yield) as yellow needle crystals.

Subsequently, under a nitrogen atmosphere, dry toluene 21
3.14 g of 2-methyl-8-hydroxyquinoline (1 ml)
9.7 mmol) and 2.02 g of aluminum isopropoxide (9.
9 mmol), and dissolved by stirring at room temperature for 10 minutes. To this solution, a solution prepared by dissolving 2.61 g (10.2 mmol) of tert-butyldiphenylsilanol prepared above in 10 ml of dry toluene was added dropwise. Then, the mixture was refluxed for 3 hours with stirring, and allowed to cool. The resulting precipitate was collected by filtration, washed with acetone, dried and purified by sublimation to obtain 0.81 g of a pale yellow powder. The melting point was measured and found to be 205 ° C. It had a molecular weight of 598 by mass spectrometry and was identified as compound (2
3) was confirmed.

[0078]

Embedded image The FT-IR spectrum of this compound was as shown in FIG. In addition, in the fluorescence measurement of this compound in a solid state, the excitation of the compound was measured using a mercury lamp (wavelength: 350 nm). As a result, the maximum fluorescence wavelength (λmax) was 484 nm, and blue fluorescence was exhibited. The band gap of this compound determined from the light absorption edge was 2.90 eV, and the ionization potential determined using an atmospheric photoelectron spectrometer (“AC-1”) manufactured by Riken Keiki was 5.50 eV.

Example 3 An organic electroluminescent device having the structure shown in FIG. 1 was produced by the following method.

Substrate with electrodes on which a transparent conductive film 2 of indium tin oxide having a thickness of 120 nm is formed on a glass substrate 1 (manufactured by Geomatech, electron beam film-formed product, sheet resistance
15Ω) was patterned into a 2 mm wide stripe by conventional photolithography and hydrochloric acid etching. This is subjected to ultrasonic cleaning in acetone, cleaning with pure water, and ultrasonic cleaning in isopropyl alcohol in order, and then dried by blowing nitrogen gas, and then irradiated by ultraviolet rays in the atmosphere. The substrate was washed with ozone.

4,4'-bis [N- (1-naphthyl) -N-
Phenylamino] biphenyl (H-1)

Embedded image Was placed in a ceramic crucible equipped with a tantalum wire heater, placed in a vacuum evaporation apparatus, and the electrode surface of the substrate that had undergone the above-described treatment was placed facing the crucible. After the vacuum evaporation apparatus was evacuated with an oil rotary pump, the vacuum evaporation apparatus was evacuated with an oil diffusion pump equipped with a liquid nitrogen trap until the degree of vacuum in the apparatus became 2 × 10 ⁻⁶ Torr or less. Energize the crucible tantalum wire heater and heat the crucible at 223 to 256 ° C to obtain 4,4'-bis [N-
(1-Naphthyl) -N-phenylamino] biphenyl was deposited. The degree of vacuum during this deposition is 2.7 × 10 ^-6 Torr
(About 3.6 × 10 ⁻⁴ Pa). 6 minutes by vapor deposition for 2 minutes 24 seconds
A 0 nm hole transport layer 4 was formed on the electrode.

Subsequently, the compound (1) prepared above was heated at a temperature of 167 to 187 ° C. and a degree of vacuum of 2.7 × 10 ⁻⁶ Torr (about 3.6 × 10 ⁻⁴ P
Vapor deposition for 1 minute and 26 seconds in a), 30 nm thick on the hole transport layer
And the 8-hydroxyquinoline complex of aluminum (E-1)

Embedded image Is deposited at a temperature of 290 to 310 ° C. and a degree of vacuum of 2.2 × 10 ⁻⁶ Torr for 1 minute and 50 seconds to form a 45 nm-thick electron transport layer 6 on the light emitting layer 5.
Was formed. Note that the substrate was kept at room temperature during the deposition of the hole transport layer 4, the light emitting layer 5, and the electron transport layer 6.

The substrate was taken out of the vapor deposition apparatus, and a striped shadow mask having a width of 2 mm was brought into close contact with the striped anode so as to be perpendicular to the stripe-shaped anode, and was loaded into the vacuum vapor deposition apparatus. After the inside of the apparatus was evacuated to 2 × 10 ⁻⁶ Torr or less, magnesium and silver were evaporated by a binary simultaneous evaporation method. The vapor deposition was performed using a molybdenum board, and a vacuum of 1 × 10 ⁻⁵ Torr, a vapor deposition time of 3 minutes and 20 seconds, and a 44 nm-thick magnesium-silver (atomic ratio)
10: 1.4) An alloy electrode was formed. Subsequently, aluminum was moistened using a molybdenum board to a degree of vacuum of 1.5 × 10 ⁻⁵ Torr
For 1 minute and 20 seconds to form an aluminum layer having a thickness of 40 nm on the alloy electrode. During the deposition of magnesium-silver and aluminum, the temperature of the substrate was kept at room temperature.

The organic electroluminescent device having a light emitting area of 2 mm × 2 mm manufactured as described above has a light emitting characteristic of 100 cd / m 2.
² , each value of the luminous efficiency and the slope of the luminance-current density characteristic, C
The values of x and y in the IE chromaticity coordinates (JIS Z8701) are as shown in Table 2.

Example 4 Compound (1) was used as the light emitting layer 5
An organic electroluminescent device was prepared in the same manner as in Example 3, except that Compound (23) was used instead of Compound (23). Its properties are as shown in Table 2.

Comparative Example 1 Bis (2-methyl-8-quinolinolato) (triphenylsilanolato) represented by the following formula as a material of the light emitting layer 5
aluminum

Embedded image At 170-190 ° C, vacuum 2.0 × 10 ^-6 Torr
An organic electroluminescent device was prepared in exactly the same manner as in Example 3, except that the light emitting layer 5 having a film thickness of 45 nm was formed by vapor deposition for 1 minute and 20 seconds. Its properties are as shown in Table 2.

[0087]

[Table 17] Table 2 shows that the organic electroluminescent device according to the present invention has excellent luminous efficiency and blue color with good color purity, and is therefore suitable for producing a full-color or multi-color display device.

[0088]

According to the organic electroluminescent device of the present invention, since the device has a light emitting layer containing a specific compound, it is possible to achieve blue light emission and to obtain a device having high luminous efficiency.
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 backlights for instrumentation), display boards, and sign lights. Especially, as a display element for in-vehicle and outdoor use that requires high heat resistance, its technical value is large. Is as described above in the section of “Summary of the Invention”.

[Brief description of the drawings]

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

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

FIG. 3 is an infrared absorption spectrum of compound (1).

FIG. 4 is an infrared absorption spectrum of compound (23).

FIG. 5 is a schematic sectional view showing another example of the organic electroluminescent device according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 anode 3 anode buffer layer 4 hole transport layer 5 light emitting layer 6 electron transport layer 7 cathode

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tomoyuki Ogata 1000-term Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Chemical Corporation Yokohama Research Laboratory F-term (reference) 3K007 AB03 AB04 AB14 CA01 CB01 DA01 DB03 EB00 4H049 VN01 VP01 VQ07 VQ08 VQ29 VQ31 VQ37 VQ38 VQ60 VQ97 VR23 VR41 VU24 VU29 VW02 4H050 AA01 AA03 AB78 AB92 WB13 WB14 WB21

Claims (4)

[Claims] 1. An organic electroluminescent device comprising a layer containing a metal complex compound represented by the following general formula (I). Embedded image (Wherein, R ^{1 to} R ⁶ are each independently a hydrogen atom,
Halogen atom, alkyl group, aralkyl group, alkenyl group, alkynyl group, cyano group, amino group, amide group, nitro group, acyl group, alkoxycarbonyl group, carboxyl group, alkoxy group, alkylsulfonyl group, hydroxyl group, aromatic hydrocarbon Represents a group or an aromatic heterocyclic group. R ¹ and R ² or R ² and R ³ may be bonded to form a ring, and any one of R ^{1 to} R ⁶ may be an alkyl group, an aralkyl group, or an alkenyl group. An alkynyl group, a secondary or tertiary amino group, an amide group, an acyl group,
When it represents an alkoxycarbonyl group, an alkoxy group, an alkylsulfonyl group, an aromatic hydrocarbon group or an aromatic heterocyclic group, these may further have a substituent in the hydrocarbon moiety. R ^{7 to} R ⁹ are each independently
Which may have a substituent, an alkyl group, an aralkyl group, an alkenyl group, an alkynyl group, a cyano group, an amino group, an amide group, a nitro group, an alkoxycarbonyl group, a carboxyl group, an alkoxy group, an alkylsulfonyl group,
It represents an aromatic hydrocarbon group or an aromatic heterocyclic group, R ⁷ ~
R ⁹ cannot all be the same group. M represents an Al atom or a Ga atom. ) 2. The metal complex compound according to claim 1, wherein R ¹ is an amino group, an alkyl group or an alkoxy group, and R ² and R ³ are each independently an amino group, An alkyl group, an alkoxy group, or a hydrogen atom, wherein R ^{4 to} R ⁹ are each independently substituted with a cyano group, a nitro group, a halogen atom, an amino group, or a halogen atom; group, an alkylsulfonyl group, a carboxyl group, an alkoxycarbonyl group or a hydrogen atom, R ⁷ to R ⁹ is each independently an alkyl group, an amino group, an alkoxy group, an aromatic hydrocarbon group or an aromatic heterocyclic group (However,
Characterized in that R ⁷ to R ⁹ is not that all have the same group) are those organic electroluminescent device according to claim 1. 3. An organic electroluminescent device having at least a light emitting layer sandwiched between an anode and a cathode on a substrate, wherein the light emitting layer contains a compound represented by the general formula (I). The organic electroluminescent device according to claim 1 or 2, wherein 4. A metal complex compound represented by the following general formula (II). Embedded image (In the formula, R ¹ represents a methyl group or an ethyl group, R ⁷
To R ⁹ are each independently a methyl group, an ethyl group, a branched alkyl group having 3 to 6 carbon atoms or —AR ¹⁰ (A is a direct bond or an alkylene group having 1 to 4 carbon atoms, and R ¹⁰ is Represents an aromatic hydrocarbon group having 6 to 12 carbon atoms, which may be substituted with an alkyl group of 1 to 3 or a dialkylamino group). R ^{7 to} R ⁹ are not all the same group. )