JP2001076880A - Organic exectroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element superior in luminescence efficiency and service life and in high-temperature storage stability. SOLUTION: An organic electroluminescent element comprises at least one layer containing a luminescent material, a buffer layer adjacent to a positive electrode, and a layer containing positive hole transporting high polymers adjacent to the buffer layer provided between electrodes consisting of a pair of positive electrodes one of which is transparent or semitransparent and a negative electrode, the buffer layer containing organic material having a decrease of 5 wt.% or less in weight at 100 through 150 degrees C and Lb/Lh being 0.5-1.5 where Lb is the thickness of the buffer layer and Lh is the thickness of the layer containing the positive hole transporting high polymers. A decrease in weight at 100 through 150 degrees C means that the organic material has a decrease in weight at 150 degrees C in terms of 100 wt.% at 100 degrees C when the organic material has temperature rise at a constant speed of 5 degrees C per minute under a helium gas atmosphere, using a thermal analyzer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device (hereinafter, sometimes referred to as an organic EL device).

[0002]

2. Description of the Related Art Organic EL devices have attracted attention because they can easily emit multicolor light in addition to low-voltage direct current drive and high luminance, and include organic fluorescent dyes as backlights and flat displays. A device having a two-layer structure in which a layer is used as a light emitting layer and the light emitting layer and a layer containing an organic compound having a charge transporting property are reported (JP-A-59-194393). Among the organic EL devices, a device using a low-molecular compound as a light-emitting body has a problem that depending on the low-molecular compound used, the luminous efficiency of the device is reduced due to the crystallization of the low-molecular compound, or the charge transport layer / light-emitting layer is used. There is a problem that it is costly because it is formed by a vacuum deposition method. In order to solve these problems, to enhance the thermal stability of the organic EL device, and to make it easier to manufacture, an organic EL device using a polymer compound as a light emitter (WO90 / 13148, JP-A-3-244630). And a device used as a hole transport material (JP-A-3-19088, WO9
No. 5/01871).

However, devices using a polymer compound as a hole transporting material or a light emitting material have been pointed out with problems such as low efficiency and short life, and a device having high efficiency and excellent life is required. Further, in order to put the organic EL device into practical use, it has been desired that the organic EL device be stable against storage at high temperatures.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic EL device having excellent luminous efficiency and device life, and excellent storage stability at high temperatures.

[0005]

Means for Solving the Problems The present inventors have proposed an organic EL device.
As a result of intensive studies to improve the luminous efficiency of the device, the device life, and the storage stability at high temperatures, a buffer layer containing a specific organic material was placed adjacent to the anode between the anode and the layer containing the hole transporting polymer. It has been found that by providing such an organic EL device, an organic EL device having excellent luminous efficiency, device life, and storage stability at high temperatures can be obtained.

That is, the present invention relates to [1] a layer containing at least one luminous body, a buffer layer adjacent to the anode, between a pair of anodes and cathodes, at least one of which is transparent or translucent; A layer containing a hole-transporting polymer adjacent to the buffer layer, wherein the buffer layer contains an organic material whose weight loss from 100 ° C. to 150 ° C. is 5% by weight or less, and a thickness of the buffer layer Is L _b , and when the thickness of the layer containing the hole transporting polymer is L _h , L _b
The present invention relates to an organic electroluminescence device having / L _h in the range of 0.5 to 1.5. Here, from 100 ° C to 15
The weight loss of 0 ° C. means that the weight of the organic material at 100 ° C. when the organic material is heated at a constant rate of 5 ° C./min in a helium gas atmosphere using a thermal analyzer is defined as 100% by weight. The weight loss of the organic material at 150 ° C. Further, the present invention provides [2] a buffer layer adjacent to the anode, a hole transporting polymer adjacent to the buffer layer, and an electrode comprising a pair of anodes and cathodes, at least one of which is transparent or translucent. A layer containing an illuminant (hereinafter, also referred to as a hole transporting luminescent layer), wherein the buffer layer has a weight loss of 5 ° C from 100 ° C to 150 ° C;
Weight percent or less, and the thickness of the buffer layer is L _b , and the thickness of the hole transporting luminescent layer is L _h ,
L _b / L _h is an organic electroluminescent device in the range of 0.5 to 1.5. Here, 100 ° C ~ 1
The weight loss at 50 ° C. is the same as that in [1].

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. As the organic material used for the buffer layer of the organic electroluminescence device of the present invention, known low molecular weight compounds and high molecular weight compounds can be used as long as the organic material has a weight loss of 5% by weight or less from 100 ° C. to 150 ° C. However, it is preferable that the organic material has a weight loss of 3% by weight or less at 150 ° C. Here, the buffer layer refers to a layer provided adjacent to the anode and having a function of improving charge injection efficiency and the like.

[0008] The weight loss of the organic material can be measured using a thermogravimetric method (Thermogravimetry) using a thermal analyzer.
y; TG). That is, from 100 ° C to 1
The weight loss of 50 ° C. means that the weight of the organic material at 100 ° C. when the organic material is heated at a constant rate of 5 ° C./min using a thermal analyzer in a helium gas atmosphere is 100% by weight. The weight loss of the organic material at 150 ° C.

In the present invention, examples of the low molecular weight compound among the organic materials used for the buffer layer include porphyrin compounds, aromatic amine compounds and derivatives thereof, and porphyrin compounds are preferred. Examples of the porphyrin compound include a porphyrin compound not coordinating a metal represented by the following formula (2) and a porphyrin compound coordinating a metal represented by the following formula (3).

[0010]

Embedded image Here, X represents a nitrogen atom or a group represented by C—R. R represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or 7
Represents an aralkyl group having up to 32 carbon atoms. Y ₁ and Y ₂ each independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an alkoxyalkyl group having 1 to 20 carbon atoms , An aryl group having 6 to 30 carbon atoms, an aralkyl group having 7 to 32 carbon atoms, a nitro group or a cyano group. Y ₁ and Y ₂ bonded to adjacent carbon atoms may be bonded to each other to form a fused polycyclic aromatic ring such as an unsaturated 6-membered ring such as a benzene ring or a naphthalene ring. Y ₁ bonded to an adjacent carbon atom
And Y ₂ may be interchanged with each other. Further, the aryl group, the unsaturated six-membered ring, and the fused polycyclic aromatic ring,
It may have a substituent such as an alkyl group, an alkoxy group, a carboxyl group, a nitro group, and a halogen atom.

Examples of the porphyrin compound represented by Chemical formula 2 include tetraphenylporphyrin, tetracarboxyphenylporphyrin, tetradimethylaminophenylporphyrin, tetranitrophenylporphyrin and the like. Furthermore, as a porphyrin compound,
And phthalocyanine compounds such as phthalocyanine and naphthalocyanine.

[0012]

Embedded image Here, X, Y ₁ and Y ₂ are the same as those of the porphyrin compound represented by the above formula (2), M represents a metal, a metal oxide or a metal halide, and copper, zinc, lead, iron, platinum, magnesium , Silver, silicon, titanium, vanadium,
Examples thereof include chromium, manganese, germanium, cadmium, indium, tin, gallium, cobalt, palladium, nickel, titanium oxide, vanadium oxide, iron chloride, and zinc chloride.

Examples of the porphyrin compound represented by the above formula 3 include cobalt octaethylporphyrin, zinc tetraphenylporphyrin, copper phthalocyanine, copper chlorophthalocyanine, oxytitanyl phthalocyanine, copper tetracarboxyphthalocyanine, and cobalt tetraaminophthalocyanine. Phthalocyanines are preferred.

Among the organic materials used for the buffer layer in the present invention, examples of the polymer compound include a conductive polymer. As the conductive polymer, polyacetylene and its derivatives, polyacetylene-based conductive polymers such as polydiacetylene and its derivatives, polyparaphenylene and its derivatives, polyphenylene-based conductive polymers such as polyphenylenevinylene and its derivatives, polypyrrole and its Derivatives, polythiophene and its derivatives, heterocyclic conductive polymers such as polyfuran and its derivatives, ionic conductive polymers such as polyaniline and its derivatives, and those which can be formed into a film by a coating method are preferable, and polythiophene and Derivatives thereof, polyaniline and derivatives thereof are more preferred. Also,
The conductive polymer may be used by increasing the conductivity by doping an appropriate dopant. As a dopant used for doping, from the viewpoint of thermal stability,
It is preferable to use those having a low vapor pressure, such as polysulfonic acid, polystyrenesulfonic acid, naphthalenesulfonic acid, and alkylnaphthalenesulfonic acid.

In the present invention, the thickness of the buffer layer is set to L
_b , when the film thickness of the hole transport layer or the hole transport light emitting layer is L _h , L _b / L _h is in the range of 0.5 to 1.5;
5 to 1.0 is preferred. When L _b / L _h is less than 0.5,
When the buffer layer is too thin, high heat resistance cannot be obtained, and when the hole transporting layer or the hole transporting light emitting layer is too thick, the driving voltage increases, which is not preferable. When it exceeds 1.5, the buffer layer is too thick. If the hole transport layer is too thin, the electron blocking property is undesirably reduced.

As the illuminant used in the organic EL device of the present invention, known low-molecular compounds and high-molecular compounds can be used as long as they exhibit fluorescence in a solid state, but a conjugated compound soluble in an organic solvent can be used. Polymer fluorescent material consisting of molecules emits light,
It is preferable because it can form a film by thermal stability and a coating method. Examples of the polymeric fluorescent substance include polyarylene and derivatives thereof, polymers and derivatives of 5-membered heterocyclic compounds at 2- and 5-positions, and polymers and derivatives thereof in which a polycyclic aromatic compound is bonded by a carbon-carbon bond. Or polyarylene vinylene and its derivatives, and polyarylene vinylene and its derivatives are particularly preferable. In order for the polymeric fluorescent substance to be soluble, each derivative having a long-chain substituent on the side chain is preferable.

The polymeric fluorescent substance comprising polyarylene and its derivative, polyarylenevinylene and its derivative, contains one or more kinds of repeating units represented by the following formula (1), and the total of the repeating units is all repeating units. Polymers containing at least 50 mol% of units are preferred. Although it depends on the structure of the repeating unit, the repeating unit represented by the formula (1) is more preferably 70 mol% or more of all the repeating units.

[0018]

Embedded image ・ ・ ・ ・ ・ (1)

The polymeric fluorescent substance may be a divalent aromatic compound group or a derivative thereof, a divalent heterocyclic compound group or a derivative thereof, or a repeating unit other than the repeating unit represented by the general formula (1). It may contain a group obtained by combining them. Equation (1)
May be linked with a non-conjugated unit having an ether group, an ester group, an amide group, an imide group, or the like, or the repeating unit may include a non-conjugated portion thereof. May be.

When the luminous body contains a repeating unit of the formula (1)
In the case of a molecular phosphor, Ar of the formula (1) ₁As the main chain
Whether the number of carbon atoms contained in the conjugated bond is 6 or more and 60 or less
Arylene group consisting of 4 or more and 60 or more carbon atoms
Heterocyclic compound groups consisting of:
Alkyl groups having 20 carbon atoms, 1-20 carbon atoms
An alkoxy group having an elemental atom, 7 to 26 carbon atoms
Alkylphenyl groups, having from 7 to 26 carbon atoms
Having at least one substituent such as an alkoxyphenyl group
May be.

In the above formula (1), n represents 0 or 1. R ₁ and R ₂ bonded to the vinylene group in the repeating unit of the formula (1) are each independently a hydrogen atom,
A group selected from the group consisting of an alkyl group having 0 carbon atoms, an aryl group having 6 to 20 carbon atoms, a heterocyclic compound group having 4 to 20 carbon atoms, and a cyano group.

Examples of the alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group and a dodecyl group. , Methyl group,
Ethyl, pentyl, hexyl, heptyl and octyl groups are preferred. Moreover, the Examples of the aryl group having 6 to 20 carbon atoms, a phenyl group, 4-C ₁ ~C ₁₄ alkoxyphenyl group (C ₁ -C ₁₄ here are 1 to 14 number of carbon atoms shown. also used in the same sense hereinafter), 4-C ₁ ~C ₁₄ alkyl phenyl group, 1-naphthyl group, 2-naphthyl groups. Furthermore, 4 ~
Heterocyclic compound groups having 20 carbon atoms include 2-
Examples thereof include a pyridyl group and a 2-quinolyl group.

Examples of the polymeric fluorescent substance containing the repeating unit of the formula (1) include JP-A-3-244630 and JP-A-5-244630.
JP-A-202355, JP-A-6-73374, JP-A-7-147190, JP-A-7-278276, JP-A-7-300580, JP-A-9-3587
0, JP-A-9-45478, JP-A-9-111
233, JP-A-10-114891, JP-A-1
0-324870, WO94 / 29883, WO98 / 212262, WO98
/ Arylenevinylenes described in JP-A- / 18996 and WO98 / 27136, and fluorene-based polymers described in JP-A-10-36487 can be suitably used.

Regarding the molecular weight of the polymeric fluorescent substance used for the luminous body of the present invention, the number average molecular weight in terms of polystyrene is 1
The range is preferably from 0 ³ to 10 ⁸ , more preferably from 10 ³ to 10 ⁷ , still more preferably 10 ^{3 to} 10 8.
５5 × 10 ⁶ . On the other hand, the weight average molecular weight is in the range of 10 ³ to 10 ⁸ , preferably 1
0 ³ to 10 ⁷ .

As the hole transporting polymer used in the organic EL device of the present invention, polyvinyl carbazole or a derivative thereof, polysilane or a derivative thereof, polyaniline or a derivative thereof, polythiophene or a derivative thereof, poly (p-phenylene vinylene) Or a derivative thereof, poly (2,5-thienylenevinylene) or a derivative thereof, a siloxane-based hole-transporting polymer, and the like. The molecular weight of the hole transporting polymer may be a high molecular weight, and the number average molecular weight in terms of polystyrene is 10 ³ or more.
The range of 10 ⁷ is preferred, and more preferably 10 ³ to 10 ⁶
And more preferably in the range of 10 ^{3 to} 5 × 10 ⁵ . On the other hand, there is no limitation on the weight average molecular weight, 10 ³ to 10 ⁷ are exemplified, preferably 10 ³ to 10 ⁶
It is. Further, a polymer having a hole transporting compound group in a side chain, a polymer having a hole transporting compound group in a main chain, and the like can be given. Among these hole-transporting polymers, a siloxane-based hole-transporting polymer is preferable, and a siloxane-based hole-transporting polymer having a hole-transporting compound group in a main chain and / or a side chain is more preferable. Further, a siloxane-based hole transporting polymer having an aromatic amine compound group in the main chain and / or side chain is more preferable.

As the siloxane-based hole transporting polymer having an aromatic amine compound group in the side chain, (A) the aromatic ring of the aromatic amine compound group is directly bonded to the silicon atom of the siloxane polymer forming the main chain. (B) a polymer in which the aromatic ring of the aromatic amine compound group is bonded to the silicon atom through an alkylene group, and (C) a nitrogen atom of the aromatic amine compound group Examples include a polymer directly bonded to a silicon atom and a polymer in which the nitrogen atom of the aromatic amine compound group (D) is bonded to the silicon atom via an alkylene group.

As the siloxane-based hole transporting polymer having an aromatic amine compound group in the main chain, (E) those in which the nitrogen atom of the aromatic amine compound group forms the main chain,
(F) an aromatic amine compound group in which an aromatic ring forms a main chain; and (G) an aromatic amine compound group in which a nitrogen atom and an aromatic ring form a main chain. Among these, (A) the polymer in which the aromatic ring of the aromatic amine compound group is directly bonded to the silicon atom of the siloxane polymer forming the main chain, and (G) the nitrogen atom and the aromatic atom of the aromatic amine compound group Those in which the aromatic ring forms the main chain are preferred. Among these, those represented by the following general formulas (2) (included in the above (A)) and (6) (included in the above (G)) are preferable.

More preferably, in the following general formula (6), Ar ₁₀ and / or Ar ₁₂ is a siloxane compound containing an aromatic amine group represented by the following general formula (7) in the main chain.

[0029]

Embedded image (2) In the general formula (2), R ₃ is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, and 6 to 30 carbon atoms. An aryl group having a carbon atom or an aralkyl group having 7 to 32 carbon atoms is shown. Ar ₂ is an arylene group having 6 to 30 carbon atoms or a group having an aromatic ethenylene skeleton represented by the following general formula (3), and Ar ₃ and Ar ₄
Is independently an aryl group having 6 to 30 carbon atoms, a group having an aromatic amine skeleton represented by the following general formula (4), or an aromatic group represented by the following general formula (5) It shows a group having an ethenylene skeleton. Further, between Ar ₂ and Ar ₃ , between Ar ₂ and Ar ₄ , or between Ar ₃ and A
It may form a ring between r _4.

[0030]

Embedded image (3) In the general formula (3), Ar ₅ and Ar ₆ each independently represent an arylene group having 6 to 30 carbon atoms, and R ₄ and R ₅ each independently represent A hydrogen atom, an alkyl group having 1 to 20 carbon atoms, 3 to 2
A cycloalkyl group having 0 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms is shown.

[0031]

Embedded image (4) In the general formula (4), Ar ₇ represents an arylene group having 6 to 30 carbon atoms, and R ₆ and R ₇ are
Each independently an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or 7
Aralkyl groups having up to 32 carbon atoms. Further, between Ar ₇ and R ₆ , between Ar ₇ and R ₇ , or between R ₆ and R ₇
May form a ring therebetween.

[0032]

Embedded image (5) In the general formula (5), Ar ₈ represents an arylene group having 6 to 30 carbon atoms, and R ₈ and R ₉ each independently represent a hydrogen atom, 1 to 20. An alkyl group having 3 carbon atoms, a cycloalkyl group having 3-20 carbon atoms, an aryl group having 6-30 carbon atoms or an aralkyl group having 7-32 carbon atoms, and Ar ₉ Represents an aryl group having 6 to 30 carbon atoms.

[0033]

Embedded image... (6) In the above general formula (6), Ar_TenAnd Ar₁₂Is
Each independently having 6 to 30 carbon atoms
Group, an aromatic amine skeleton represented by the following general formula (7):
Group or an aromatic ether represented by the following general formula (8)
It shows a group having a tenylene skeleton. Also, Ar₁₁Is 6 ~
An aryl group having 30 carbon atoms, represented by the following general formula
A group having an aromatic amine skeleton represented by (9), or
An aromatic ethenylene skeleton represented by the following general formula (10)
The following shows the group. Also, Ar_TenAnd Ar ₁₁During, Ar_TenWhen
Ar₁₂Or Ar₁₁And Ar₁₂Form a ring between
May be. R_Ten, R₁₁, R₁₂And R₁₃Respectively
Independently, a hydroxyl group, an alkyl having 1 to 20 carbon atoms
Having 3 to 20 carbon atoms
Cycloalkyl group having 6 to 30 carbon atoms
Aryl, aralkyl having 7 to 32 carbon atoms
A group represented by the following general formulas (11) and (13);
Is cross-linked in the molecule and bonded to the silicon atom in the molecule.
Or the cross-linking of molecules between molecules
It represents a divalent oxygen atom which may be bonded to an element atom.

[0034]

Embedded image (7) In the general formula (7), Ar ₁₃ and Ar ₁₄ each independently represent an arylene group having 6 to 30 carbon atoms, and R ₁₄ represents 1 to 20 carbon atoms. An alkyl group having carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group having 7 to 32 carbon atoms.
Further, a ring may be formed between Ar ₁₃ and Ar ₁₄ , between Ar ₁₃ and R ₁₄ , or between Ar ₁₄ and R ₁₄ .

[0035]

Embedded image (8) In the general formula (8), Ar ₁₅ and Ar ₁₆ each independently represent an arylene group having 6 to 30 carbon atoms, and R ₁₅ and R ₁₆ are each independently A hydrogen atom, an alkyl group having 1 to 20 carbon atoms,
Cycloalkyl groups having 20 carbon atoms, 6-30
An aryl group having 7 carbon atoms or an aralkyl group having 7 to 32 carbon atoms.

[0036]

Embedded image (9) In the general formula (9), Ar ₁₇ represents an arylene group having 6 to 30 carbon atoms, and R ₁₇ and R _17
18 is each independently an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or 7 to 32 An aralkyl group having a carbon atom is shown. Further, a ring may be formed between Ar ₁₇ and R ₁₇ , between Ar ₁₇ and R ₁₈ , or between R ₁₇ and R ₁₈ .

[0037]

Embedded image (10) In the general formula (10), Ar ₁₈ represents an arylene group having 6 to 30 carbon atoms, and R ₁₉ and R ₂₀
Is independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or 7 to 32 Represents an aralkyl group having 6 carbon atoms, and Ar ₁₉ represents an aryl group having 6 to 30 carbon atoms.

[0038]

Embedded image (11) In the general formula (11), Ar ₂₀ and Ar ₂₂ are
Each independently an arylene group having 6 to 30 carbon atoms, a group having an aromatic amine skeleton represented by the above general formula (7), or an aromatic ethenylene skeleton represented by the above general formula (8) A group having the formula: In the formula, Ar
₂₁ is an aryl group having 6 to 30 carbon atoms, a group having an aromatic amine skeleton represented by the general formula (9),
Or a group having an aromatic ethenylene skeleton represented by the general formula (10). Also, between Ar ₂₀ and Ar ₂₁ , A
A ring may be formed between r ₂₀ and Ar ₂₂ or between Ar ₂₁ and Ar ₂₂ . R ₂₁ and R ₂₂ are each independently a hydroxyl group, an alkyl or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, 6 to 30 carbon atoms Or an aralkyl group having 7 to 32 carbon atoms, which may be cross-linked in a molecule and bonded to a silicon atom in the molecule, or a silicon atom of an adjacent molecule which is cross-linked between molecules. And a divalent oxygen atom which may be bonded to. In the formula, R ₂₃ represents a hydrogen atom or the following general formula (12).

[0039]

Embedded image (12) In the above general formula (12), R ₂₄ , R ₂₅ and R
₂₆ is each independently a hydroxyl group, an alkyl or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, or An aralkyl group having 7 to 32 carbon atoms is shown.

[0040]

Embedded image (13) In the general formula (13), R ₂₇ , R ₂₈ and R
₂₉ is independently an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms, 7
An aralkyl group having up to 32 carbon atoms, a group having an aromatic ethenylene skeleton represented by the general formula (10),
Or a group having an aromatic amine skeleton represented by the following general formula (14).

[0041]

Embedded image... (14) In the above general formula (14), Ar_{twenty three}Is 6 to 30
An arylene group having a carbon atom, represented by the above general formula (7)
A group having an aromatic amine skeleton represented by the general formula
A group having an aromatic ethenylene skeleton represented by (8)
You. Also, Ar _{twenty four}And Ar_{twenty five}Are each independently 6
Aryl groups having up to 30 carbon atoms, of the above general formula
A group having an aromatic amine skeleton represented by (9), or
The aromatic ethenylene skeleton represented by the general formula (10)
The following shows the group.

The siloxane-based hole-transporting material used in the present invention has a high
For the molecular weight of the molecule, the polystyrene equivalent number average
Child size is 10^Three-10⁷Is more preferable, more preferably
10 ^Three-10⁶And more preferably 10^Three~
5 × 10^FiveRange. On the other hand, the weight average molecular weight
There is no limit, but 10^Three-10⁷Is exemplified, preferably
Is 10^Three-10⁶It is.

The structure of the organic EL device of the present invention [1] is such that at least one of the transparent or translucent pair of anode and cathode electrodes has at least one layer containing a luminous body and a layer adjacent to the anode. Having a buffer layer,
In addition, a layer containing a hole transporting polymer may be provided adjacent to the buffer layer. Further, the organic EL of the present invention [2]
As a structure of the element, a buffer layer adjacent to the anode is provided between a pair of anodes and cathodes, at least one of which is transparent or translucent, and a hole transporting luminescent layer is provided adjacent to the buffer layer. You only need to have it. In the organic EL device of the present invention [1] or [2], an element in which an electron transport layer is provided adjacent to a light emitting layer or a hole transport light emitting layer, and a hole transport layer is provided adjacent to a light emitting layer Are preferred. The structure of the organic EL device of the present invention [1] includes:
Specifically, the following structures a) and b) are exemplified. a) Anode / buffer layer / hole transport layer / light-emitting layer / cathode b) anode / buffer layer / hole transport layer / light-emitting layer / electron transport layer / cathode Further, as the structure of the organic EL device of the present invention [2]. Specifically, the following structures c) to d) are exemplified. c) anode / buffer layer / hole transport / emission layer / cathode d) anode / buffer layer / hole transport / emission layer / electron transport layer / cathode

Further, the light emitting layer, the hole transporting layer, the electron transporting layer, and the hole transporting light emitting layer may be each independently used in two or more layers. The order and number of layers to be stacked and the thickness of each layer can be appropriately used in consideration of luminous efficiency and device life. The shape, size, material, manufacturing method, and the like of the organic EL device of the present invention having these structures are appropriately selected according to the use of the organic EL device.

In the organic EL device of the present invention, the method of forming the buffer layer is not limited, but when a low molecular compound is used as the organic material of the buffer layer, it is formed from a mixed solution with a polymer binder. Examples include a method using a film and a vacuum evaporation method. When a polymer compound is used as the organic material of the buffer layer, a method of forming a film from a solution may be used.

As the polymer binder to be mixed with the low-molecular compound, those which do not extremely impair the charge transporting property and heat resistance are preferable, and those which do not strongly absorb visible light are preferably used. Examples of the polymer binder include poly (N-vinylcarbazole), polyaniline or a derivative thereof, polythiophene or a derivative thereof, poly (p-phenylenevinylene) or a derivative thereof, poly (2,5-thienylenevinylene) or a derivative thereof,
Polycarbonate, polyacrylate, polymethyl acrylate, polymethyl methacrylate, polystyrene,
Examples thereof include polyvinyl chloride and polysiloxane.

The solvent used for film formation from a solution is not particularly limited as long as it can dissolve a polymer.
As the solvent, chloroform, methylene chloride, chlorine solvents such as dichloroethane, ether solvents such as tetrahydrofuran, aromatic hydrocarbon solvents such as toluene and xylene, acetone, ketone solvents such as methyl ethyl ketone, ethyl acetate, butyl acetate, Examples thereof include ester solvents such as ethyl cellosolve acetate, and water-soluble solvents such as water, methanol, ethanol, and isopropyl alcohol.

As a method of forming a film from a solution, a spin coating method, a casting method, a microgravure coating method,
Coating methods such as gravure coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, screen printing, flexographic printing, offset printing, and inkjet printing can be used.

In the organic EL device of the present invention, the above-mentioned polymeric fluorescent substance is preferably used as the luminescent material used in the luminescent layer or the hole transporting luminescent layer. Or a mixture with the polymeric fluorescent substance. Further, a layer containing a luminescent material other than the polymer fluorescent material may be used in combination. Examples of good solvents for the polymeric fluorescent substance include chloroform, methylene chloride, dichloroethane, tetrahydrofuran, toluene, xylene, decalin and the like. Depending on the structure and molecular weight of the polymeric fluorescent substance, usually 0.1% by weight of these solvents is used.
The above can be dissolved.

When a film is formed from a solution using these organic solvent-soluble polymeric phosphors in the preparation of an organic EL device, it is only necessary to remove the solvent by drying after coating this solution. The same method can be applied to the case where a light-emitting material is mixed with a light-emitting material, which is very advantageous in manufacturing. As a method of forming a film from a solution, spin coating, casting, microgravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, screen printing, Flexographic printing, offset printing,
A coating method such as an inkjet printing method can be used.

In the organic EL device of the present invention, the above hole transporting polymer is preferably used as a hole transporting material used in the hole transporting layer or the hole transporting light emitting layer. May be used as a mixture, or a hole transport material other than the hole transport polymer may be used as a mixture. Further, a layer containing a hole transporting material other than the hole transporting polymer may be used in combination. Examples of hole transporting materials other than the hole transporting polymer used include pyrazoline derivatives,
Examples thereof include an arylamine derivative, a hydrazone derivative, a stilbene derivative, and a triphenyldiamine derivative.

Specifically, examples of the hole transport material include JP-A-57-101844 and JP-A-58-197143, JP-B-58-32372, and JP-A-2-36270.
And JP-A-3-37992. In the case of a low-molecular-weight hole transport material,
It is preferable to use it by dispersing it in a polymer binder.

When the organic EL device of the present invention has an electron transporting layer, known electron transporting materials can be used, and oxadiazole derivatives, anthraquinodimethane or its derivatives, benzoquinone or its derivatives , Naphthoquinone or its derivative, anthraquinone or its derivative, tetracyanoanthraquinodimethane or its derivative, fluorenone derivative, diphenyldicyanoethylene or its derivative,
Examples thereof include a diphenoquinone derivative, and a metal complex of 8-hydroxyquinoline or a derivative thereof.

Specifically, JP-A-63-70257, JP-A-63-175860, and JP-A-2-1353
Nos. 59, 2-135361, 2-209
988, 3-37992, 3-152
184 is exemplified.
Of these, oxadiazole derivatives, benzoquinone or its derivatives, anthraquinone or its derivatives, or metal complexes of 8-hydroxyquinoline or its derivatives are preferred, and 2- (4-biphenylyl) -5 is preferred.
-(4-t-butylphenyl) -1,3,4-oxadiazole, benzoquinone, anthraquinone, tris (8
-Quinolinol) aluminum is more preferred.

The method of forming the hole transporting layer or the electron transporting layer is not limited. For the low molecular weight hole transporting material, the method of forming a film from a mixed solution with a polymer binder is used. In addition to film formation from a solution, a vacuum deposition method is exemplified. In the case of a polymer hole transport material or a polymer electron transport material, a method of forming a film from a solution is exemplified.
The solvent used for film formation from a solution may be any solvent that dissolves the hole transporting material or the electron transporting material. Examples of the solvent include chloroform, methylene chloride, chlorinated solvents such as dichloroethane, ether solvents such as tetrahydrofuran, Aromatic hydrocarbon solvents such as toluene and xylene,
Examples thereof include ketone solvents such as acetone and methyl ethyl ketone, and ester solvents such as ethyl acetate, butyl acetate and ethyl cellosolve acetate.

When a film is formed from a solution using a siloxane-based hole-transporting polymer as the hole-transporting polymer, an additive can be added. Examples of the additive include defatty acid salts such as zinc, lead, cobalt, and tin; ammonia, amines such as trimethylamine and triethylamine; and N-alkyl-substituted piperazine or piperidine. Of these, amines are preferred. Used. The amount of the additive is preferably 0.1 to 10% by weight.

As a method of forming a film from a solution, a spin coating method, a casting method, a microgravure coating method,
Coating methods such as gravure coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, screen printing, flexographic printing, offset printing, and inkjet printing can be used.

As the polymer binder to be mixed, those which do not extremely impair the charge transportability are preferable, and those which do not strongly absorb visible light are suitably used. As the polymer binder, poly (N-vinylcarbazole), polyaniline or a derivative thereof, polythiophene or a derivative thereof, poly (p-phenylenevinylene) or a derivative thereof, poly (2,5-thienylenevinylene) or a derivative thereof, polycarbonate , Polyacrylate, polymethyl acrylate, polymethyl methacrylate, polystyrene, polyvinyl chloride, polysiloxane and the like.

When a siloxane-based hole-transporting polymer is used as the hole-transporting polymer, heat treatment is preferably performed after forming a layer containing the siloxane-based hole-transporting polymer. The temperature range of the heat treatment may be a range in which the hole transporting compound contained in the siloxane-based polymer is not decomposed and the hole transporting property is not significantly impaired, and is preferably in a range of 50 ° C to 250 ° C, more preferably. Is 100 ° C to 200 ° C
Range. Examples of the atmosphere for the heat treatment include the air, an inert atmosphere, and a vacuum, and preferably the air. The heat treatment time is preferably in the range of 1 minute to 1 hour, more preferably in the range of 1 minute to 20 minutes.

In the present invention, as a material of the transparent or translucent anode, a conductive metal oxide film, a translucent metal thin film, or the like is used. Specifically, a film (such as NESA) formed using a conductive glass made of indium tin oxide (ITO), zinc oxide (ZnO), tin oxide (SnO ₂ ), or the like, or gold, platinum, or silver , Copper and the like are used, and ITO, ZnO and SnO ₂ are preferable. Examples of the manufacturing method include a vacuum deposition method, a sputtering method, an ion plating method, and a plating method.

Next, as the material of the cathode used in the present invention, a material having a small work function is preferable. For example, aluminum, indium, magnesium, calcium, lithium, magnesium-silver alloy, magnesium-indium alloy, indium-silver alloy, lithium-aluminum alloy, lithium-magnesium alloy, lithium-indium alloy, calcium-aluminum alloy, graphite, or A graphite interlayer compound or the like is used.

As a method for producing the cathode, a vacuum deposition method, a sputtering method, a lamination method for thermocompression bonding a metal thin film, and the like are used. After the cathode is formed, a protective layer for protecting the organic EL device may be provided.

[0063]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it should not be construed that the present invention is limited thereto. <Measurement of Molecular Weight> Regarding the molecular weight, a weight average molecular weight and a number average molecular weight in terms of polystyrene were determined by gel permeation chromatography (GPC). <Measurement of weight loss> The weight loss was measured using a thermal analyzer (SSC5200, TG / DTA3 manufactured by Seiko Instruments Inc.).
20), in a helium gas atmosphere, at a heating rate of 5 ° C.
The change in weight upon heating at / min was measured, and the change in weight based on the weight at 100 ° C was determined.

Reference Synthesis Example 1 <Synthesis of silane compound 1>
A solution of 8.0 g of the dibromo derivative of N'-diphenyl-N, N'-bis (3 "-methylphenyl) -1,1'-biphenyl-4,4'-diamine in a dry tetrahydrofuran solution was added at -78.degree. 17 ml of a butyllithium / n-hexane solution was added for lithiation, and N, N′-diphenyl-N, N′-bis (3 ″ -methylphenyl) -1,1 ′ was added.
A dilithium derivative of -biphenyl-4,4'-diamine was produced.

In a dry argon atmosphere, a solution of 7.0 g of dimethoxymethylchlorosilane in dry tetrahydrofuran was added at -78 ° C. to the N, N′-diphenyl-N, N ′.
A solution of a dilithium derivative of -bis (3 "-methylphenyl) -1,1'-biphenyl-4,4'-diamine was added dropwise to the mixture, and the mixture was stirred at -78 ° C for 1 hour. After distilling off excess dimethoxymethylchlorosilane and the solvent, dry toluene was added thereto and the lithium salt was removed with a glass filter under a dry argon atmosphere, and the solvent was distilled off to obtain 7.1 g of a viscous solid. nuclear magnetic resonance spectra of the obtained reaction product from ^{(1 H-NMR), N} , N '
That a dimethoxymethylsilyl derivative and a bis (dimethoxymethylsilyl) derivative of -diphenyl-N, N'-bis (3 "-methylphenyl) -1,1'-biphenyl-4,4'-diamine are formed; confirmed.
Hereinafter, this is referred to as silane compound 1. ¹ H-NMR: 0.40 [s] (methyl group bonded to silicon atom), 2.28 [s] (methyl group), 2.40
[S] (methyl group), 3.60 [s] (methoxy group),
6.8 to 7.6 [m] (aromatic group)

<Synthesis of hole transporting polymer 1> 10 ml of a tetrahydrofuran solution of silane compound 1 (6.5 g)
And 3.5 ml of triethylamine and 0.1 ml of water while stirring.
65 ml was added, and the mixture was stirred at 60 ° C. After evaporating the solvent, the residue was purified by reprecipitation with tetrahydrofuran / 2-propanol to obtain 3.17 g of a white solid.

The nuclear magnetic resonance absorption spectrum of the obtained white solid shows a signal of a methyl group bonded to a silicon atom at about 0.0 to 0.7 ppm, and a methyl on the phenyl ring at about 1.8 to 2.4 ppm. Wide range of signals, 3.4-
A signal of a methoxy group around 3.7 ppm and 6.2
A broad signal of aromatic ring protons was observed around ７7.6 ppm. In addition, the infrared absorption spectrum
100 cm ^-1, broad signal of from a siloxane bond in the vicinity of 800 cm ^-1, broad signal of from hydroxyl groups was observed around 3300 cm ^-1, N the obtained polymer, N '
-Diphenyl-N, N'-bis (3 "-methylphenyl) -1,1'-biphenyl-4,4'-diamine group is incorporated as a part of a repeating unit, and is formed by hydrolysis. It was confirmed that some of the hydroxyl groups remained unreacted, and the molecular weight was measured by GPC to find that the weight average molecular weight in terms of polystyrene was 2.2 × 10 ⁴ and the number average molecular weight was 6. It was 2 × 10 ³ .

To 15 ml of a tetrahydrofuran solution of the white solid (1.0 g) obtained above was added triethylamine 3
After addition of 1.7 ml of triphenylchlorosilane, the mixture was stirred at 55 ° C. Water was added to quench excess triphenylchlorosilane. After distilling off the solvent, the residue was dissolved in toluene and mixed with water using a separating funnel. Then, the toluene layer was separated and the solvent was distilled off. The obtained solid was purified by reprecipitation with tetrahydrofuran / 2-propanol to obtain 0.85 g of a white solid.

Nuclear magnetic resonance absorption spectrum of the obtained white solid
From the ratio of the integrated signal values in
It was confirmed that the lyl group had been incorporated. Also, infrared
3300 cm in the absorption spectrum^-1Low intensity near
However, a wide range of signals derived from hydroxyl groups were observed,
I confirmed that it still remains. In addition, the molecular weight is determined by GPC.
When measured at, the weight average converted to polystyrene
The molecular weight is 2.4 × 10 ^Four, Number average molecular weight is 7.9 × 10^Three
Met.

Further, 4 ml of triethylamine was added to 20 ml of a tetrahydrofuran solution of the above white solid (0.65 g) obtained by reacting with triphenylchlorosilane.
, 0.43 g of diphenylmethylchlorosilane
Was added and stirred at room temperature. The solid obtained by post-treatment of the reaction in the same manner as in the reaction with triphenylchlorosilane was purified by reprecipitation with tetrahydrofuran / ethanol to obtain 0.48 g of a white solid. Hereinafter, this is referred to as a hole transporting polymer 1.

In the nuclear magnetic resonance absorption spectrum of the obtained hole transporting polymer 1, a methyl signal of diphenylmethylsilyl group was observed at around 0.4 to 0.6 ppm.
It was confirmed that a diphenylmethylsilyl group had been incorporated. In the infrared absorption spectrum, 3300 cm
^No signal was observed around ^-1 and it was confirmed that no hydroxyl group remained. When the molecular weight of the hole transporting polymer 1 was measured by GPC, the weight average molecular weight in terms of polystyrene was 2.9 × 10 ⁴ , and the number average molecular weight was 9.5.
× 10 ³ .

Reference Synthesis Example 2 <Synthesis of polymeric fluorescent substance 1> 2,5-dioctyloxy-
p-Xylylene dichloride was reacted with triphenylphosphine in N, N-dimethylformamide solvent to synthesize a phosphonium salt. 3. The obtained phosphonium salt
78 g, 4.228 g of a phosphonium salt of 2-methoxy-5-octyloxy-p-xylylene dichloride obtained in the same manner, 1.01 g of terephthalaldehyde and 1.15 g of 1-pyrenecarboxaldehyde were added to ethyl alcohol It was dissolved in a mixed solvent of 80 g / 100 g of chloroform. A solution obtained by mixing 10 ml of a 12% methanol solution of lithium methoxide and 40 ml of ethanol was added dropwise to a mixed solution of a phosphonium salt and an aldehyde in ethyl alcohol / chloroform, followed by a reaction at room temperature for 4 hours. After standing at room temperature overnight, the precipitate was collected, washed with ethyl alcohol, and then dissolved in toluene, to which ethanol was added for reprecipitation purification. After reprecipitation purification twice, this was dried under reduced pressure to obtain 2.0 g of a polymeric fluorescent substance. This is called polymeric fluorescent substance 1.

The repeating units of polymeric fluorescent substance 1 calculated from the charged ratio of the monomers and the molar ratios thereof are shown below. It was confirmed by ¹ H-NMR that a pyrenyl group was present at the molecular terminal.

[0074]

Embedded image (15) The number average molecular weight in terms of polystyrene of the polymeric fluorescent substance 1 was 2.5 × 10 ³ . By infrared absorption and ¹ H-NMR, a spectrum corresponding to an approximately 50:50 copolymer of 2-methoxy-5-octyloxy-p-phenylenevinylene and 2,5-dioctyloxy-p-phenylenevinylene was obtained. Was done.

Reference Synthesis Example 3 <Synthesis of polymeric fluorescent substance 2> 2-methoxy-5-isoamyloxy-p-xylylenedibromide was reacted with triphenylphosphine in an N, N-dimethylformamide solvent to convert a phosphonium salt. Synthesized. 4.52 g of the obtained phosphonium salt, 0.54 g of terephthalaldehyde and 1
0.46 g of pyrenecarboxaldehyde was dissolved in 100 ml of a mixed solvent of ethanol / toluene (1/1). Next, to this ethanol / toluene mixed solution of the phosphonium salt and the aldehyde, 25 ml of a solution obtained by mixing 5 ml of a 12% lithium methoxide methanol solution and 20 ml of ethyl alcohol was added dropwise at room temperature. Continued
The reaction was performed at room temperature for 5 hours.

After standing at room temperature overnight, the formed precipitate was recovered. Next, the precipitate was washed with ethanol. Next, this precipitate was dissolved in toluene, and ethanol was added thereto for reprecipitation purification. This was dried under reduced pressure to obtain polymer 0.1.
3 g were obtained. The obtained polymer is called polymeric fluorescent substance 2.

The repeating units of polymeric fluorescent substance 2 calculated from the charging ratio of the monomers are shown below. The molecular terminal mainly has a pyrenyl group.

[0078]

Embedded image (16) The number average molecular weight in terms of polystyrene of the polymeric fluorescent substance 2 was 2.9 × 10 ³ . By infrared absorption and ¹ H-NMR, a spectrum corresponding to 2-methoxy-5-isoamyloxy-p-phenylenevinylene was obtained.

<Preparation and Evaluation of Device> Example 1 An ITO film having a thickness of 200 nm was formed by sputtering.
On a glass substrate with^-6Torr at 450 ° C
Vacuum deposition of sublimated and purified copper phthalocyanine (Tokyo Kasei)
According to the method, 50 nm was deposited. On top of this, high hole transportability
Spin coating method using toluene solution of molecule 1
As a result, a hole transport layer having a thickness of 50 nm was laminated. Hole
After forming the transport layer, on a hot plate heated to 150 ° C
Then, a heat treatment was performed in the air for 5 minutes. Moreover
Then, using a decalin solution of polymeric fluorescent substance 1, spin
The light emitting layer having a thickness of 50 nm is laminated by the coating method.
Was. Next, this was dried under reduced pressure at 120 ° C. for 1 hour.
Tris (8-quinolinol) is formed on the light emitting layer as an electron transporting layer.
Le) aluminum (Alq_Three) Was deposited to a thickness of 50 nm. Sa
In addition, an aluminum-lithium alloy (Al:
Li = 99: 1 by weight) is evaporated to a thickness of 100 nm to form an organic E
An L element was produced. The degree of vacuum at the time of deposition is 8 × 10
^-6Torr or less. Device buffer layer and hole transport
The layer thickness ratio is L _b/ L_h= 1.0. This element
5mA / cm in nitrogen stream^TwoDrive so that the current density is
When moved, the luminance is 100 cd / m^TwoMet. this
After storing the device in a 110 ° C. vacuum oven for 7 days
When driven under the same conditions, the luminance was 99 cd / m
^TwoAnd almost the same luminance as before storage at 110 ° C. Using
Temperature rise of copper phthalocyanine at 5 ° C / min in helium atmosphere
And thermogravimetric measurement showed weight loss from 100 ° C
Is 0.3% at 150 ° C. and 0.7% at 400 ° C.
Showed high thermal stability.

Example 2 A glass phthalocyanine having a thickness of 200 nm was laminated on a glass substrate having a 200 nm-thick ITO film by sputtering by a vacuum evaporation method. On top of this, 1,2 of polyvinyl carbazole (manufactured by Aldrich: Mw = 1,100,000)
-A hole transport layer having a thickness of 50 nm was laminated by a spin coating method using a dichloroethane solution. A light emitting layer having a thickness of 50 nm was laminated thereon by spin coating using a decalin solution of the polymeric fluorescent substance 1. Next, after drying this at 120 ° C. for 1 hour under reduced pressure,
Tris (8-quinolinol) aluminum (Alq ₃ ) was deposited to a thickness of 50 nm on the light emitting layer as an electron transporting layer.
Further, an aluminum-lithium alloy (A
1: Li = 99: 1 by weight) was evaporated to a thickness of 100 nm to produce an organic EL device. The degree of vacuum at the time of evaporation is all 8 ×
It was 10 ^-6 Torr or less. The ratio of the thickness of the buffer layer to the thickness of the hole transport layer of the device was L _b / L _h = 1.0. When the device was driven in a nitrogen stream to have a current density of 5 mA / cm ² , the luminance was 185 cd / m ² .
When this device was driven under the same conditions after being stored in a vacuum oven at 110 ° C. for 14 days, the luminance was 200 cd
/ M ² and almost the same luminance as before storage at 110 ° C.

Example 3 A 10-fold diluted solution of polythiophene (PEDOT manufactured by Bayer) in isopropyl alcohol was formed into a film having a thickness of 30 nm by spin coating on a glass substrate provided with an ITO film having a thickness of 200 nm by sputtering. On a hot plate heated to
Heat treatment was performed for minutes. On top of this, using a toluene solution of the hole transporting polymer 1 by a spin coating method,
A hole transport layer having a thickness of 50 nm was laminated. After forming the hole transport layer, a heat treatment was performed in the air for 5 minutes on a hot plate heated to 150 ° C. Further, a light emitting layer having a thickness of 50 nm was laminated thereon by spin coating using a decalin solution of the polymeric fluorescent substance 2. Next, this was dried under reduced pressure at 120 ° C. for 1 hour, and then tris (8-quinolinol) aluminum (Alq3) was deposited as an electron transporting layer on the light emitting layer to a thickness of 50 nm. Further, an aluminum-lithium alloy (Al: Li = 99: 1 weight ratio) was deposited to a thickness of 100 nm as a cathode to produce an organic EL device. The degree of vacuum at the time of deposition was 8 × 10 ⁻⁶ Torr or less. The ratio of the thickness of the buffer layer to the thickness of the hole transport layer of the device was L _b / L _h = 0.6. This element was placed in a nitrogen stream for 5 minutes.
When driven to have a current density of mA / cm ² ,
The luminance was 83 cd / m ² . This element was heated at 110 ° C.
After storage in a vacuum oven for 3 days and driving under the same conditions, the luminance was 83 cd / m ² , which was almost the same as before storage at 110 ° C. After removing the solvent of the used polythiophene solution, it was dried at 100 ° C. in vacuum, and the obtained solid was heated in a helium atmosphere at 5 ° C./min. The decrease was 2.4% at 150 ° C.

Example 4 In accordance with the method described in Molecular Crystals Liquid Crystals, Part E, 119, pp. 173-180 (1985), aniline was prepared using ammonium persulfate as an oxidizing agent. Was subjected to an aqueous sodium hydroxide treatment, followed by washing and drying to obtain polyaniline. By sputtering, a 200 nm thick I
A 0.5 wt% solution of the obtained polyaniline in N-methyl-2-pyrrolidone was formed to a thickness of 40 nm on a glass substrate provided with a TO film by spin coating. The substrate coated with polyaniline was immersed in an aqueous solution of polystyrene sulfonic acid for doping, and then subjected to a heat treatment in the air for 5 minutes on a hot plate heated to 150 ° C. On this, a hole transporting layer having a thickness of 50 nm was laminated by a spin coating method using a toluene solution of the hole transporting polymer 2. After forming the hole transport layer, a heat treatment was performed in the air for 5 minutes on a hot plate heated to 150 ° C. Further, a light emitting layer having a thickness of 50 nm was laminated thereon by spin coating using a decalin solution of the polymeric fluorescent substance 1. Next, this is subjected to
After drying for 5 hours, tris (8-quinolinol) aluminum (Alq3) was added on the light emitting layer as an electron transporting layer.
0 nm was deposited. Further, 100 n of an aluminum-lithium alloy (Al: Li = 99: 1 weight ratio) is used as a cathode.
m was deposited to produce an organic EL device. The degree of vacuum at the time of deposition was 8 × 10 ⁻⁶ Torr or less. The ratio of the thickness of the buffer layer to the thickness of the hole transport layer of the device was L _b / L _h = 0.8. When this device was driven in a nitrogen stream to have a current density of 5 mA / cm ² , the luminance was 75 cd / m 2.
^{Was 2} . When the device was driven under the same conditions after being stored in a vacuum oven at 110 ° C. for 3 days, the luminance was as follows:
76 cd / m ² , almost the same luminance as before storage at 110 ° C. The polyaniline used was placed in a helium atmosphere at 5 ° C /
When the temperature was raised in 100 minutes and thermogravimetry was performed, the weight loss from 100 ° C. was 0.6% at 150 ° C. and 1.6.5 at 400 ° C.
%, Indicating high thermal stability.

Comparative Example 1 An organic EL device was prepared in the same manner as in the organic EL device of Example 2, except that copper phthalocyanine was not formed. When this device was driven in a nitrogen stream to have a current density of 5 mA / cm ² , the luminance was 220 cd / m ² . When the device was stored in a vacuum oven at 100 ° C. for 4 days and then driven under the same conditions, the luminance was 98 cd.
/ M ² , the luminance was greatly reduced.

Comparative Example 2 In the organic EL device of Example 1, the hole transporting polymer 1
Was formed in the same manner except that no film was formed. This element was placed in a nitrogen stream at 5 mA.
/ Cm ² , the luminance was 51 cd / m ² . When the device was driven under the same conditions after being stored in a vacuum oven at 100 ° C. for 5 days, the brightness was significantly reduced to ² cd / m ² .

[0085]

The organic electroluminescent device of the present invention exhibits excellent luminous efficiency, device life and storage stability at high temperatures, and thus can be preferably used as devices such as a planar light source as a backlight and a flat panel display. .

Claims (11)

[Claims] An electrode comprising a pair of anodes and cathodes, at least one of which is transparent or translucent, a layer containing at least one luminescent material, a buffer layer adjacent to the anode, and a positive electrode adjacent to the buffer layer. A buffer layer containing a hole-transporting polymer, wherein the buffer layer contains an organic material whose weight loss from 100 ° C. to 150 ° C. is 5% by weight or less, and the buffer layer has a thickness of L _b , when the thickness of the layer containing a transport polymer was L _h, the organic electroluminescent device L _b / L _h is equal to or in the range of 0.5 to 1.5. Here, the weight loss from 100 ° C. to 150 ° C. means the weight of the organic material at 100 ° C. when the temperature of the organic material is increased at a constant rate of 5 ° C./min using a thermal analyzer in a helium gas atmosphere. Refers to a weight loss at 150 ° C. of the organic material when the weight of the organic material is 100% by weight. 2. At least one is transparent or translucent.
Adjacent to the anode, between a pair of anode and cathode electrodes
Buffer layer and hole transport adjacent to the buffer layer
Buffer layer having a layer containing a conductive polymer and a luminescent material
However, if the weight loss from 100 ° C to 150 ° C is 5% by weight or less
Contains a certain organic material, and adjusts the thickness of the buffer layer.
L _b, The thickness of the layer containing the hole-transporting polymer and the phosphor
L_hAnd L_b/ L_hIs in the range of 0.5 to 1.5
Organic electroluminescent element characterized by the following:
Child. Here, the weight loss from 100 ° C. to 150 ° C.
The machine material is raised using a thermal analyzer under a helium gas atmosphere.
100% of the organic material when heated at a temperature rate of 5 ° C./min.
The organic material when the weight at 100 ° C. is 100% by weight
Weight loss at 150 ° C. 3. A polymeric fluorescent substance whose luminous body is composed of a conjugated polymer exhibiting fluorescence in a solid state, comprising one or more kinds of repeating units represented by the following formula (1), and the total of those repeating units is ^3. The organic electroluminescent device according to claim 1, wherein the number of the repeating units is 50 mol% or more and the number average molecular weight in terms of polystyrene is 10 ³ to 10 ⁸ . Embedded image ... (1) [where Ar ₁ is an arylene group containing 6 to 60 carbon atoms in the conjugated bond of the main chain or a 4 to 60 carbon atoms. Is a heterocyclic compound group represented by R ₁ and R ₂ each independently represent a hydrogen atom,
And a group selected from the group consisting of an alkyl group having 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, a heterocyclic compound group having 4 to 20 carbon atoms, and a cyano group. n represents 0 or 1] 4. The organic electroluminescent device according to claim 1, wherein the hole transporting polymer is a siloxane-based hole transporting polymer. 5. The organic electroluminescent device according to claim 1, wherein the organic material whose weight loss is 5% or less is a porphyrin compound. 6. The organic electroluminescent device according to claim 5, wherein the porphyrin compound is a phthalocyanine compound. 7. The organic electroluminescent device according to claim 1, wherein the organic material whose weight loss is 5% or less is a conductive polymer. 8. The organic electroluminescent device according to claim 7, wherein the conductive polymer is polyaniline or a derivative thereof. 9. The organic electroluminescent device according to claim 7, wherein the conductive polymer is polythiophene or a derivative thereof. 10. An electron transport layer according to claim 1, wherein an electron transport layer is provided adjacent to the layer containing the luminous body or the layer containing the hole transporting polymer and the luminous body. Organic electroluminescent element. 11. A method according to claim 1, wherein a layer containing a hole transporting polymer is provided adjacent to the layer containing the luminous body.
10. The organic electroluminescent device according to any one of 3 to 9 above.