JPH06330034A - Organic electroluminescent element - Google Patents

Abstract

PURPOSE:To provide an organic electroluminescent element having increased adhesiveness between a cathode and an electron injection layer and enabling uniform light emission. CONSTITUTION:The organic electroluminescence element is produced by inserting an adhesion improving layer between a cathode and an organic layer. The dipole component of the surface energy of the adhesion improving layer is >=4dyn/cm.

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, and more particularly, to an organic electroluminescence device capable of uniform light emission by enhancing the adhesion between a cathode and an electron injection layer.

[0002]

2. Description of the Related Art At present, electroluminescence elements (hereinafter sometimes abbreviated as EL elements) have high visibility due to self-luminance.
Since it is a completely solid element and has a characteristic of excellent impact resistance, various elements using inorganic / organic compounds have been proposed and attempted to be put into practical use. Among these elements, an organic EL element using an organic compound can greatly reduce the applied voltage, and therefore various materials and elements using the same are being developed. As an element structure of such an organic EL element, there is known a structure in which a hole injection layer and an electron injection layer are provided as necessary to improve the light emission performance, based on a basic structure of an anode / a light emitting layer / a cathode. In these configurations, metals such as Mg, Al and In are used for the cathode, but these metals have poor adhesion to the organic compounds used for the light emitting layer and the electron injection layer. In such a device structure having poor adhesion, the mechanical strength of the device is reduced, and the light emission becomes nonuniform (a non-light emitting region may occur). Further, in such an element, the load on the light emitting surface becomes non-uniform, which promotes deterioration of the element and shortens its life, which is a problem for practical use.

[0003]

The cause of non-uniform light emission of an organic EL device is that the adhesion between the cathode and the organic layer is insufficient as described above. Generally, the adhesiveness of two substances is determined by the surface energy of each substance. It is said that if the difference between the surface energies of these two substances is large, the adhesion is poor, and if the difference is small, the adhesion is good. Therefore, since the surface energy of metals is generally large and the surface energy of organic substances is small, it can be easily imagined that the adhesion is poor. There are a dispersive force component (so-called van der Waals force) and a dipole interaction component (hereinafter referred to as dipole component) (Coulomb force) as components that generate the surface energy of an organic substance. The range and target are different. As a result of diligent research, the present inventors have found that the dipole component plays an important role in the surface energy with respect to the adhesion between the metal and the organic substance, and the substance having a dipole component of 4 dyn / cm or more. It was found that by inserting the compound between the organic substance and the cathode, the adhesion between the organic substance and the cathode was improved, and uniform light emission was achieved. That is, the present invention relates to an organic electroluminescence device having an adhesion improving layer between a cathode and an organic layer, wherein the dipole component of the surface energy of the adhesion improving layer is 4 dyn / cm.
The present invention provides an organic electroluminescence device characterized by the above.

In the organic EL device of the present invention, a cathode and an organic layer (a light emitting layer, an electron injection layer, etc.) are formed on the basis of the usual device structure.
There is an adhesion improving layer between and. Examples of such a device structure include: anode / light-emitting layer / adhesion improving layer / cathode anode / hole injection layer / light-emitting layer / adhesion improving layer / cathode anode / light-emitting layer / electron injection layer / adhesion improving layer / cathode anode / Examples include hole injection layer / light emitting layer / electron injection layer / adhesion improving layer / cathode. Of the above configurations, or particularly the configuration is preferable. Here, the hole injection layer is a layer having at least one of hole injection property, transport property, and electron barrier property, and the electron injection layer is an electron injection property, transport property, hole Is a layer having at least one of the barrier properties. The hole injecting layer and the electron injecting layer may each be composed of one layer or two layers. The organic layer includes a hole injection material and a light emitting material,
A layer having a plurality of functions, which is formed by mixing a light emitting material and an electron injecting material, or a hole injecting material, a light emitting material, and an electron injecting material, may be used. As a result of intensive studies by the present inventors, the element having poor performance because it has excellent performance as an electron injecting layer but poor adhesion to the cathode, uniformity of light emission by providing an adhesion improving layer as in the present invention, It has been found that the life can be improved. The adhesion improving layer may have a dipole component of surface energy of 4 dyn / cm or more, preferably 4
˜20 dyn / cm, particularly preferably 5 to 10 dyn /
cm. Here, the surface energy is 4 dyn / cm
If it is less than 20%, the adhesion between the cathode (metal) and the adhesion improving layer deteriorates, and if it exceeds 20 dyn / cm, the adhesion between the organic layer forming the light emitting layer and the electron injection layer and the adhesion improving layer deteriorates. There is. Various materials are used as the adhesion improving material for such an adhesion improving layer, but preferred examples are shown below. First, the general formula (I)

[0005]

[Chemical 6]

(Where, k, l, m and n are 0 to 5 respectively)
Indicates an integer. However, the case of k = 1 = m = n = 0 is excluded. Also, Ar is

[0007]

[Chemical 7]

(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms or halogen, and R ² and R ³ each represent hydrogen, an alkyl group having 1 to 6 carbon atoms or halogen.
p represents an integer of 1 to 4, q and r each represent an integer of 0 to 4. However, R ¹ , R ² and R ³ may be the same or different. )) And a compound having a cyano group. Next, general formula (II)

[0009]

[Chemical 8]

(In the formula, Z ¹ and Z ² each independently represent an unsubstituted or substituted aromatic group. Here, the substituent is an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, Represents a cyano group, chlorine, bromine or fluorine, and Y ¹ ,
Y ^2's each independently represent an unsubstituted or aromatic group having an alkyl group having 1 to 5 carbon atoms. Q is -O-, -CH ₂
-, - CH ₂ -CH ₂ - or -C (CH _{3) 2} - indicates, X is shows a -O- or -S-. ) And a compound having an oxadiazole ring. In addition, the general formula (III)

[0011]

[Chemical 9]

(In the formula, A is a single bond, --O--, --SO.
_2- , -S-, -CH = CH-, -CO-,

[0013]

[Chemical 10]

(In the formula, s represents an integer of 1 to 8). B ¹ and B ² are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, unsubstituted or having 6 to 1 carbon atoms having a substituent.
8 represents an aryl group of 8 or an unsubstituted or substituted heterocyclic residue having 3 to 12 carbon atoms. Here, the substituents are nitro group, amino group, cyano group, hydroxyl group, carboxyl group,
Methylthio group, ethylthio group, halogen, carbon number 1-6
Alkoxy group, C1-6 alkoxycarbonyl group, C2-8 dialkylamino group, C2-8
And a C 1-6 alkylenedioxy group or a C 1-6 alkyleneoxy group. B ¹ and B ² may be the same or different. )
And a compound having a quinoxaline ring. Specific examples of the compound represented by the above general formula (I) include:

[0015]

[Chemical 11]

[0016]

[Chemical 12]

[0017]

[Chemical 13]

[0018]

[Chemical 14]

And the like. In addition, specific examples of the compound represented by the general formula (II) include:

[0020]

[Chemical 15]

[0021]

[Chemical 16]

[0022]

[Chemical 17]

[0023]

[Chemical 18]

[0024]

[Chemical 19]

[0025]

[Chemical 20]

And the like. General formula (III)
Specific examples of the compound represented by

[0027]

[Chemical 21]

[0028]

[Chemical formula 22]

[0029]

[Chemical formula 23]

And the like. The above-mentioned adhesion improving material can exhibit the effect of the present invention particularly effectively in the above-mentioned constitution.

The other constituent materials of the organic EL device of the present invention are not particularly limited, and known materials can be used. For example, as the light emitting material used for the light emitting layer, any one of conventionally known compounds can be selected and used. Examples of the light-emitting material include polycyclic condensed aromatic compounds, benzoxazole-based, benzothiazole-based, benzimidazole-based optical brighteners, metal chelated oxanoide compounds, distyrylbenzene-based compounds, and other thin-film-forming compounds. Is used. Here, examples of the above-mentioned polycyclic fused aromatic compound include condensed ring luminescent substances containing anthracene, naphthalene, phenanthrene, pyrene, chrysene, and perylene skeletons.

As the above-mentioned fluorescent whitening agents of benzoxazole type, benzothiazole type, benzimidazole type and the like, for example, those described in JP-A-59-194393 can be used, and typical examples thereof are ,
2,5-bis (5,7-di-t-pentyl-2-benzoxazolyl) -1,3,4-thiadiazole; 4,
4'-bis (5,7-t-pentyl-2-benzoxazolyl) stilbene; 4,4'-bis (5,7-di-
(2-Methyl-2-butyl) -2-benzoxazolyl) stilbene; 2,5-bis (5,7-di-t-pentyl-2-benzoxazolyl) thiophene; 2,5-
Bis (5- (α, α, -dimethylbenzyl) -2-benzoxazolyl) thiophene; 2,5-bis (5,7-
Di- (2-methyl-2-butyl) -2-benzoxazolyl) -3,4-diphenylthiophene; 2,5-bis (5-methyl-2-benzoxazolyl) thiophene;
4,4'-bis (2-benzoxazolyl) biphenyl; 5-methyl-2- (2- (4- (5-methyl-2-
Benzoxazolyl) phenyl) vinyl) benzoxazole; benzoxazoles such as 2- (2- (4-chlorophenyl) vinyl) naphtho (1,2-d) oxazole, 2,2 ′-(p-phenylenedivinylene) ) -Bisbenzothiazole and other benzothiazoles, 2-
Examples thereof include (2- (4- (2-benzimidazolyl) phenyl) vinyl) benzimidazole; 2- (2- (4-carboxyphenyl) vinyl) benzimidazole, and other fluorescent whitening agents such as benzimidazole compounds. Further, as other useful compounds, those listed in Chemistry of Synthetic Soybean 1971, 628 to 637 and 640 can be used.

As the metal chelated oxanoide compound, for example, those described in JP-A-63-295695 can be used. As typical examples thereof, tris (8-quinolinol) aluminum, bis (8-quinolinol) magnesium, bis (benzo (f) -8-quinolinol) zinc, bis (2-methyl-8-quinolinolato) aluminum oxide, tris ( 8-quinolinol) indium, tris (5-methyl-8-quinolinol) aluminum, 8-quinolinol lithium, tris (5-chloro-8-quinolinol)
Gallium, bis (5-chloro-8-quinolinol) calcium, poly (zinc (II) -bis (8-hydroxy-5)
Examples include 8-hydroxyquinoline-based metal complexes such as -quinolinonyl) methane) and dilithium epinetridione.

Other examples include distyrylbenzene derivatives described in European Patent No. 0319881 or European Patent No. 0373582, and specific examples of the distyrylbenzene derivative include 1,4-bis ( 2-Methylstyryl) benzene; 1,4-bis (3-methylstyryl) benzene; 1,4-bis (4-methylstyryl) benzene; distyrylbenzene; 1,4-bis (2
-Ethylstyryl) benzene; 1,4-bis (3-ethylstyryl) benzene; 1,4-bis (2-methylstyryl) -2-benzene; 1,4-bis (2-methylstyryl) -2-ethylbenzene And so on. Also,
The distyrylpyrazine derivative described in JP-A-2-252793 can also be used, and specific examples thereof include 2,5-bis (4-methylstyryl) pyrazine; 2,5-bis (4
-Ethylstyryl) pyrazine; 2,5-bis (2- (1
-Naphthyl) vinyl) pyrazine; 2,5-bis (4-methoxystyryl) pyrazine; 2,5-bis (2- (4-
Biphenyl) vinyl) pyrazine; 2,5-bis (2-
(1-pyrenyl) vinyl) pyrazine and the like.
In addition, the dimethylidene derivative described in European Patent No. 0388768 and JP-A-2-231970, the coumarin derivative described in JP-A-2-191946, the perylene derivative described in JP-A-2-196885, and JP-A-2 Naphthalene derivatives described in JP-A-255789, JP-A-2-289676 and JP-A-2-886.
Phthaloperinone derivatives described in JP-A No. 89, JP-A 2-2
And a styrylamine derivative disclosed in Japanese Patent No. 50292.
The cyclopentadiene derivative described in JP-A-289675 and the like can be appropriately selected depending on the desired emission color and performance.

The light emitting layer made of the above light emitting material may have a laminated structure of two or more layers, if desired.
It may be formed by adding a fluorescent substance as disclosed in Japanese Patent No. 69,292. In this case, the organic compound is a thin film-like layer and has a part of the injection function and the light emitting function of the function of the light emitting region, while the fluorescent substance is present in the organic compound layer in a trace amount (several mol% or less). It plays a part of a light emitting function of emitting light in response to recombination of electrons and holes. Further, the organic compound used in the light emitting region may be a compound having no thin film property, and examples of such a compound include 12-phthaloperinone; 1,4-diphenyl-1,3-butadiene; 1,4,4-Tetraphenyl-1,3-butadiene; Tetraphenylcyclopentadiene; Naphthalimide derivative (JP-A-2-3
No. 05886); perylene derivative (JP-A-2-18)
9890); oxadiazole derivatives (JP-A-2
-216791 or the oxadiazole derivative disclosed by Hamada et al. In the 38th Joint Lecture on Applied Physics; aldazine derivative (JP-A-2-220393).
Gazette); Pyrazillin derivative (JP-A-2-220394)
Gazette); cyclopentadiene derivative (JP-A-2-28
9675); Pyrrolopyrrole derivative (JP-A-2-
296891); styrylamine derivatives (App
l. Phys. Lett. , Volume 56, L799 (19
90 years); Coumarin compounds (Japanese Patent Laid-Open No. 191694/1990)
Publication); International Publication WO90 / 13148 or App
l. Phys. Lett. , Volume 58, L8, P198
2 (1991). However, these materials that do not have a thin film property have a shortcoming that the life of the device is short. In the above light emitting material, it is particularly preferable to use an aromatic dimethylidene-based compound, and specific examples thereof include 1,4-phenylenedimethylidene; 4,4′-phenylenedimethylidene;
2,5-xylylene dimethylidene; 2,6-naphthylene dimethylidene; 1,4-biphenylene dimethylidene;
1,4-p-Telephenylenedimethylidene; 9,10-
Anthracene diyl methylidene; 4,4'-bis (2,
2-di-t-butylphenylvinyl) biphenyl; 4,
4′-bis (2,2-diphenylvinyl) biphenyl and the like, or derivatives thereof. This light emitting layer may be composed of a single or two or more light emitting materials composed of these organic or inorganic compounds,
Alternatively, a light emitting layer made of a compound different from the light emitting layer may be laminated.

Next, the hole injecting layer is made of a hole transferring compound and has a function of transferring the holes injected from the anode to the light emitting layer. By interposing this hole injection layer between the anode and the light emitting layer, many holes are injected into the light emitting layer at a lower electric field, and moreover, the electrons injected from the cathode or the electron injection layer into the light emitting layer are: Due to the barrier of electrons existing at the interface between the light emitting layer and the hole injecting layer, the device is excellent in light emitting performance, such as being accumulated at the interface in the light emitting layer and improving the light emitting efficiency. The hole transporting compound used in the hole injecting layer is disposed between two electrodes to which an electric field is applied, and when the hole is injected from the anode, the hole is appropriately transferred to the light emitting layer. Is possible, for example 10 ⁴ -10 ⁶
At least 10 ^-6 cm ² / V · when an electric field of V / cm is applied
Those having a hole mobility of seconds are suitable. The hole transfer compound is not particularly limited as long as it has the above-mentioned preferable properties, and conventionally, in the optical transmission material,
Any material can be selected and used from materials commonly used as charge injection / transport materials for holes and known materials used for hole injection layers of organic EL devices.

Examples of the hole transfer compound include quinoxaline compounds represented by the general formula (I), triazole derivatives (US Pat. No. 3,112,197), oxadiazole derivatives (US Pat. No. 3,189,447). ，
Imidazole derivative (JP-B-37-16096), polyarylalkane derivative (US Pat. No. 3,615,
402, U.S. Pat. No. 3,820,989, U.S. Pat. No. 3,542,544, JP-B-45-555,
Japanese Patent Publication No. 51-10983, Japanese Patent Publication No. 51-9322
4, Japanese Patent Publication No. 55-17105, Japanese Patent Publication No. 56
-4148 gazette, Japanese Patent Publication No. 55-108667 gazette,
Japanese Patent Publication No. 55-156953, Japanese Patent Publication No. 56-366
56), pyrazoline derivatives and pyrazolone derivatives (US Pat. No. 3,180,729, US Pat. No. 4,278,74).
6 specification, JP-A-55-88064, JP-A-5
JP-A-5-88065, JP-A-49-105537, JP-A-55-51086, and JP-A-56-80.
No. 051, JP-A-56-88141, JP-A-57-45545, JP-A-54-112637, JP-A-55-74546) and phenylenediamine derivatives (US Pat. No. 3,615,404). Description, JP-B-51-10105, JP-B-46-3712, JP-B-47-25336, JP-A-54-53
435, JP-A-54-110536, JP-A-54-119925), arylamine derivatives (US Pat. No. 3,567,450, US Pat. No. 3,180,70).
No. 3, U.S. Pat.No. 3,240,597, U.S. Pat.No. 3,658,520, U.S. Pat.No. 4,232,103, U.S. Pat.No. 4,175,961, U.S. Pat.
376, JP-B-49-35702, JP-B-39-27577, JP-A-55-144250, JP-A-56-119132, JP-A-56-
22437, West German Patent 1,110,518),
Amino-substituted chalcone derivative (US Pat. No. 3,526,501), oxazole derivative (US Pat. No. 3,257,203), styrylanthracene derivative (JP-A-56-
46234), fluorenone derivatives (JP-A-54)
-110837), hydrazone derivatives (US Pat. No. 3,717,462, JP-A-54-59143, JP-A-55-52063, JP-A-55-52).
064, JP-A-55-46760, JP-A-55-85495, JP-A-57-11350, JP-A-57-148749, and JP-A-2-31.
1591), stilbene derivatives (JP-A-61-2)
10363, JP-A-61-228451,
JP 61-14642 A, JP 61-7225 A
5, JP-A-62-47646, JP-A-62.
-36674, JP-A-62-10652,
JP-A-62-30255, JP-A-60-9344
5, JP-A-60-94462, JP-A-60-
-174749, JP60-175052), silazane derivatives (US Pat. No. 4,950,950), polysilane-based (JP-A-2-204996), aniline-based copolymers (JP-A-2-282632). No.), a conductive polymer oligomer (JP-A 1-2113)
99, especially thiophene oligomers and the like).

In the organic EL device used in the present invention,
The above hole transporting compound or charge injecting / transporting material can be used as the hole injecting material, and the following porphyrin compounds (as described in JP-A-63-295965) and aromatic tertiary compounds. Amine compounds and styrylamine compounds (U.S. Pat. No. 4,127,412, JP-A-53-27033, JP-A-54-58445, JP-A-54-149634, and JP-A-54-64299)
No. 55-79450, No. 55-1442.
No. 50, No. 56-119132, No. 61-2.
95558, 61-98353, 63.
It is preferable to use the aromatic tertiary amine compound. Typical examples of the porphyrin compound include porphine, 1,10,1
5,20-Tetraphenyl-21H, 23H-porphine copper (II); 1,10,15,20-tetraphenyl 2
1H, 23H-porphine cuprous (II); 5,10,1
5,20-Tetrakis (pentafluorophenyl) -2
1H, 23H-porphine; Silicon phthalocyanine oxide; Aluminum phthalocyanine chloride; Phthalocyanine (no metal); Dilithium phthalocyanine; Copper tetramethylphthalocyanine; Copper phthalocyanine; Chromium phthalocyanine; Zinc phthalocyanine; Lead phthalocyanine; Titanium phthalocyanine oxide; Magnesium phthalocyanine; Examples include methyl phthalocyanine.

Typical examples of the aromatic tertiary amine compound and styrylamine compound include N, N, N ',
N'-tetraphenyl-4,4'-diaminophenyl;
N, N'-diphenyl-N, N'-di (3-methylphenyl) -4,4'-diaminobiphenyl (TPDA);
2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ', N'-tetra-
p-tolyl-4,4'-diaminobiphenyl; 1,1-
Bis (4-di-p-tolylaminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-
Methylphenyl) phenylmethane; bis (4-di-p-
Trilylaminophenyl) phenylmethane; N, N'-diphenyl-N, N'-di (4-methoxyphenyl)-
4,4'-diaminobiphenyl; N, N, N ', N'-
Tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl; N, N, N-tri (p-tolyl) amine; 4-
(Di-p-tolylamino) -4 '-[4 (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino- (2-diphenylvinyl) benzene; 3-
Methoxy-4′-N, N-diphenylaminostilbenzene; N-phenylcarbazole and the like. In addition, crystals of inorganic semiconductors such as Si, SiC, CdS,
Amorphous materials can also be used. Furthermore, it is an inorganic substance, p
A hole injecting material of type-Si or p-type-SiC can also be used. For example, an inorganic semiconductor disclosed in International Publication WO90 / 05998 may be used. The hole injection layer of the present invention may be composed of a single layer composed of one or more of these hole injection materials, or
The hole injection layer may be formed by laminating a hole injection layer made of a different kind of compound on the hole injection layer.

The electron injection layer is made of an electron injection material and has a function of transmitting the electrons injected from the cathode to the light emitting layer. The electron injecting material is not particularly limited, and any one of conventionally known compounds can be selected and used. Specific examples thereof include nitro-substituted fluorenone derivatives and anthraquinodimethane derivatives (JP-A-57-149259, JP-A-58-55450, JP-A-63-10406).
No. 1), diphenylquinone derivative (Polyme)
r, Preprints, Japan 37, No.
3 (1988) p. 681), a thiopyran dioxide derivative, a heterocyclic tetracarboxylic acid anhydride such as naphthaleneperylene, a carbodiimide, a fluorenylidenemethane derivative (Japanease Journal of A).
Applied Physics, Volume 27, L269 (1
988)), an anthraquinodimethane derivative (JP-A-61-61)
-225151, JP 61-233750), anthrone derivative (JP 61-225151, JP 61-233750), oxadiazole derivative (Appl. Phys. Lett., 5).
5, 15, 1489 and those disclosed by Hamada et al.), Electron-transporting compounds (JP-A-59-194393), and the like. In addition, Tris (8
-Quinolinol) aluminum, tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,5
A metal complex of an 8-quinolinol derivative such as 7-dibromo-8-quinolinol) aluminum or tris (2-methyl-8-quinolinol) aluminum, or a central metal of the 8-quinolinol derivative is aluminum to In, M
a metal complex replacing g, Cu, Ca, Sn, Pb,
A metal-free or metal phthalocyanine, a metal-free or metal phthalocyanine whose terminal is substituted with an alkyl group or a sulfone group, and a distyrylpyrazine derivative which is a material of the light emitting layer can also be used as the electron injection material. Furthermore, n-type α-S which is an inorganic substance
An electron injection material made of i, n-type α-SiC can be used as the electron injection material. For example, international publication WO90
Inorganic semiconductors and the like disclosed in / 05998 are cited. The electron injection layer of the present invention may be composed of a single layer composed of one or two or more of these electron injection materials, or is a stack of electron injection layers composed of a compound different from the layer. May be.

Next, a method for manufacturing the EL element used in the present invention
A preferred example of will be described. As an example, the above-mentioned anode / hole injection
Consisting of injection layer / light emitting layer / electron injection layer / adhesion improving layer / cathode
A method for manufacturing an EL element will be described. First, columnar transparent
On the substrate, consists of the desired electrode material, for example the anode material
The thin film should have a thickness of 1 μm or less, preferably 10 to 200 nm.
Those who use evaporation or sputtering to achieve the
Then, the anode is formed by the method. Then leave this on
Hole injection layer, light-emitting layer, electron injection layer, adhesion improvement
A thin film is formed in order of the material of the good layer. Those who make thin films
As the method, spin coating, casting,
Although there are vapor deposition methods, it is easy to obtain a uniform film and
The vacuum deposition method is preferred because it does not easily generate holes.
Good If this vapor deposition method is used for this thinning,
The vapor deposition conditions are: type of compound used, molecular deposition film
Depending on the target crystal structure, association structure, etc.,
Boat heating temperature 50-450 ℃, vacuum degree 10 ^-Five-10
^-3Pa, evaporation rate 0.01 to 50 nm / sec, substrate temperature -5
Select appropriately in the range of 0 ~ 300 ℃, film thickness 5nm ~ 5μm.
And is desirable. After forming these layers, cathode materials
A thin film of a quality of 1 μm or less, preferably 50 to 200
For example, vapor deposition or sputtering to obtain a film thickness in the range of nm.
Formed by a method such as a ring and provided with a cathode
As a result, a desired EL element can be obtained. In addition, this EL element
In order to fabricate the
Good layer, electron injection layer, light emitting layer, hole injection layer, anode
It is also possible to manufacture. In addition, holes are injected between the pair of electrodes.
In the form of mixed injection layer, emission layer and electron injection layer (mixed layer)
Element consisting of sandwiched anode / mixed layer / adhesion improving layer / cathode
As a method of manufacturing the child, for example, an anode is formed on a suitable substrate.
A thin film made of a substance for use in forming a hole injection material, a light emitting material
Materials, electron injection materials, polyvinylcarbazole, polycarbonate
Bonate, Polyarylate, Polyester, Polyete
Solution such as a binder, or
A thin film is formed from the solution of
However, the one on which the above-mentioned adhesion improving layer and the cathode are formed is
is there.

In the organic EL device thus obtained,
When a DC voltage is applied, light emission can be observed by applying a voltage of about 5 to 40 V with the anode having a positive polarity and the cathode having a negative polarity. Moreover, even if a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Furthermore, when an AC voltage is applied, light is emitted only when the positive electrode is in the + state and the negative electrode is in the − state. The waveform of the alternating current applied may be arbitrary.

[0043]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples. Surface energy measuring method Surface energy is measured by a contact angle measuring method. This contact angle measuring method is used as a general measuring method. H. KAELBLE, JOURNAL OF A
PPLIED POLYMER SCIENCE Vo
l. 18. PP. 1869-1889 (1974) is mentioned. A specific method will be described below with reference to the accompanying drawings. First, when a drop of the liquid 1 having a known surface energy is dropped on the vapor deposition film of the contact improving material 2, the liquid 1 adheres on the vapor deposition film as shown in FIG. Here, the contact angle is θ, and other parameters are defined as follows. γ _S : Surface energy of the deposited film (interfacial tension) γ _L : Surface energy of the liquid (surface tension) α _S : Square root of the dispersive component of the surface energy of the deposited film α _L : Square root of the dispersive component of the surface energy of the liquid β _S : Square root of dipole interaction component of surface energy of deposited film β _L : Square root of dipole interaction component of liquid surface energy γ _S = α _S ² + β _S ² γ _L = α _L ² + β _L ² Above Therefore, the following relational expression holds. (1 + cos θ) γ _L = 2 (α _L α _S + β _L β _S ) This formula is transformed into (1 + cos θ) γ _L / 2α _L = α _S + (β _L / α _L ) β _S (A) be able to. Therefore, θ is measured using several kinds of liquids with known γ _L , α _L , and β _L , and as shown in FIG. 2, the horizontal axis is β _L / α _L and the vertical axis is (1 + cos θ) γ _L
A straight line is obtained when plotted as / 2α _L. The slope of this straight line is β _S and the intercept with the vertical axis is α _S. Here, the dipole component of the surface energy is represented by β _S ² .
The values of γ _L , 2α _L , and β _L / α _L of known liquids used for the measurement are shown in Table 1, respectively.

Measurement of Contact Angle A glass substrate having a size of 25 mm × 20 mm × 1.1 mm was fixed to a basic holder of a commercially available vacuum deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.), and the molybdenum resistance heating boat was charged with the above-mentioned Compound 1 200mg was added and heated to 320 ℃, vapor deposition rate 0.1
A vapor deposition film having a film thickness of 30 nm was prepared by depositing it on the substrate at a rate of up to 0.3 nm / sec. Here, the substrate temperature was room temperature. Then, the obtained vapor deposition film was taken out from the vapor deposition device and attached to a contact angle measuring device (manufactured by Elmo Optical Co., Ltd.). Then, one drop of the liquid having a known surface energy shown in Table 1 was dropped, and the contact angle was measured. Each measured value was substituted into the above formula (A), and α _S and β _S were obtained from the slope of the straight line and the intercept of the y-axis. From the graph shown in FIG. 2, the slope (β _S ) is 2.8 (dy
n / cm) ^1/2 , Y intercept (α _S ) is 5.8 (dyn / c)
m) ^{1/2, which} is the dipole component of the surface energy (β
_S ) ² is 7.8 dyms / cm, and the dispersion force component (α _S ) ² is 3
The calculated value was 3.6 dyn / cm. The surface energy in the following examples and comparative examples was measured by the above method.

[0045]

[Table 1]

Example 1 ITO was formed on a 25 mm × 75 mm × 1.1 mm glass substrate.
The transparent support substrate was prepared by forming an electrode with a thickness of 100 nm. The transparent supporting substrate was ultrasonically cleaned with isopropyl alcohol for 5 minutes, then with pure water for 5 minutes, and again with isopropyl alcohol for 5 minutes. Then
This transparent support substrate was fixed to a basic holder of a commercially available vacuum deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.), and a molybdenum resistance heating boat was fitted with N, N'-diphenylether-N,
200 mg of N'-bis (3-methylphenyl)-(1,1'-biphenyl) -4,4'-diamine (TPD)
Put it in another molybdenum resistance heating boat for 4,4'-
Bis (2,2'-diphenylvinyl) biphenyl (DP
Put 200 mg of VBi) into the vacuum chamber 1 × 1
The pressure was reduced to 0 ^-4 Pa. After that, the boat containing TPD is heated to 215 to 220 ° C. to deposit TPD at a deposition rate of 0.1 to
It was deposited on the substrate at 0.3 nm / sec to form a hole injection layer having a film thickness of 60 nm. The substrate temperature at this time was room temperature. Without removing the obtained hole injection layer from the vacuum chamber, DPVBi was placed on the hole injection layer at a boat temperature of 250 ° C.
It was deposited on the substrate at a vapor deposition rate of 0.1 to 0.2 nm / sec to form a light emitting layer having a film thickness of 40 nm. The substrate temperature at this time was room temperature. Further, 200 mg of tris (8-quinolinol) aluminum (Alq) was put in a resistance heating boat made of molybdenum, and the pressure in the vacuum chamber was reduced to 2 × 10 ⁻⁴ Pa. A boat containing Alq was heated to 280 ° C., Alq was deposited on the substrate at a vapor deposition rate of 0.3 nm / sec, and an electron injection layer having a film thickness of 20 nm was formed. After forming the electron injection layer, the obtained deposit was taken out of the vacuum chamber, a stainless steel mask was placed on the light emitting layer, and the substrate was fixed again on the substrate holder. Then, 200 mg of the exemplified compound 1 was placed in a molybdenum resistance heating boat.
It was put in and attached to a vacuum chamber. Also, 0.5 g of Ag wire was placed in a tungsten basket, and 1 g of Mg ribbon was placed in another molybdenum resistance heating boat. The pressure in the vacuum chamber was reduced to 1 × 10 ⁻⁴ Pa, Compound 1 was deposited at a vapor deposition rate of 0.1 nm / sec, and an adhesion improving layer having a film thickness of 10 nm was formed. On top of that, Mg deposition rate 1.8 nm / sec,
At the same time, Ag was vapor-deposited at a vapor deposition rate of 0.1 nm / sec to prepare a cathode. The obtained device emitted blue light. Table 2 shows the dipole energy of the surface energy and the light emitting state of the adhesion improving layer of the device.

Example 2 A device was prepared in the same manner as in Example 1 except that Compound 14 was used as the material for the adhesive layer. The obtained device emitted blue light. Table 2 shows the dipole energy of the surface energy and the light emitting state of the adhesion improving layer of the device.

Example 3 A device was prepared in the same manner as in Example 1 except that the exemplified compound 17 was used as the material for the adhesive layer. The obtained device emitted blue light. Table 2 shows the dipole energy of the surface energy and the light emitting state of the adhesion improving layer of the device.

Example 4 A device was prepared in the same manner as in Example 1 except that the exemplified compound 21 was used as the material for the adhesive layer. The obtained device emitted blue light. Table 2 shows the dipole energy of the surface energy and the light emitting state of the adhesion improving layer of the device.

Example 5 A device was prepared in the same manner as in Example 1 except that the exemplified compound 64 was used as the material for the adhesive layer. The obtained device emitted blue light. Table 2 shows the dipole energy of the surface energy and the light emitting state of the adhesion improving layer of the device.

Example 6 A device was prepared in the same manner as in Example 1 except that the exemplified compound 74 was used as the material for the adhesive layer. The obtained device emitted blue light. Table 2 shows the dipole energy of the surface energy and the light emitting state of the adhesion improving layer of the device.

Example 7 ITO on a glass substrate of 25 mm × 75 mm × 1.1 mm
The transparent support substrate was prepared by forming an electrode with a thickness of 100 nm. The transparent supporting substrate was ultrasonically cleaned with isopropyl alcohol for 5 minutes, then with pure water for 5 minutes, and again with isopropyl alcohol for 5 minutes. Then
This transparent support substrate was fixed to a basic holder of a commercially available vacuum deposition apparatus (manufactured by Nippon Vacuum Technology Co., Ltd.), and a molybdenum resistance heating boat was fitted with N, N'-diphenylether-N,
200 mg of N'-bis (3-methylphenyl)-(1,1'-biphenyl) -4,4'-diamine (TPD)
Put it in another molybdenum resistance heating boat for 4,4'-
Bis (2,2'-diphenylvinyl) biphenyl (DP
VBi) was added in an amount of 200 mg, and another molybdenum resistance heating boat was charged with 100 mg of 2,3-bis (2,2-diphenylvinyl) quinoxaline (DPVQ) to reduce the pressure in the vacuum chamber to 1 × 10 ⁻⁴ Pa. . afterwards,
Heat the boat with TPD to 215-220 ° C
PD was deposited on the substrate at a vapor deposition rate of 0.1 to 0.3 nm / sec to form a hole injection layer having a film thickness of 60 nm. The substrate temperature at this time was room temperature. Without removing the obtained hole injection layer from the vacuum chamber, DPVBi was deposited on the substrate at a boat temperature of 250 ° C. and a vapor deposition rate of 0.1 to 0.2 nm / sec to form a light emitting layer having a thickness of 40 nm. The film was formed. The substrate temperature at this time was room temperature. Further, DPVQ is deposited on the substrate at a vapor deposition rate of 0.1 to 0.2 nm / sec to obtain a film thickness of 10
An electron injection layer of nm was formed. Next, 200 mg of the exemplified compound (74) was put into a resistance heating boat made of molybdenum, and the boat was mounted in a vacuum chamber.
^The pressure was reduced to ⁻⁴ Pa, the boat containing the compound (74) was electrically heated to 300 ° C., and the compound (74) was deposited on the substrate at a vapor deposition rate of 0.3 nm / sec to a film thickness of 10 nm.
Finally, the obtained deposit was taken out of the vacuum chamber, a stainless steel mask was placed on the light emitting layer, and it was fixed again to the substrate holder. Next, 0.5 g of Ag wire was placed in a tungsten basket, and 1 g of Mg ribbon was placed in another molybdenum resistance heating boat. Reduce the pressure in the vacuum chamber to 1 × 10 ^-4 Pa,
Deposition rate of Mg is 1.8 nm / sec, and deposition rate of Ag is 0.
A cathode was produced by vapor deposition at 1 nm / sec. The obtained device emitted blue light uniformly.

Example 8 Instead of DPVQ in the electron injection layer, 4,4'-bis [2-
A device was produced in the same manner as in Example 7 except that (4-phenylquinolyl)] biphenyl was used. The device emitted uniform blue light. When it was continuously driven in dry nitrogen at an initial stage of 100 cd / m ² , the half life was 100 hours.

Comparative Example 1 A light emitting layer made of DPVBi was prepared in the same manner as in Example 1. Then remove it from the vacuum chamber,
A stainless steel mask was placed on the light emitting layer and fixed again on the substrate holder. Next, put 0.5 g of Ag wire in the tungsten basket, put 1 g of Mg ribbon in the molybdenum boat, and put the vacuum chamber in 1 × 10 ^-4.
Reduced pressure to Pa, Mg (deposition rate 1.8 nm / sec) and Ag
(Vapor deposition rate of 0.1 nm / sec) was simultaneously vapor-deposited to prepare a negative electrode. The device thus obtained emitted blue light, but had nonuniform donut-shaped light emission. Table 2 shows the dipole energy of the surface energy and the light emitting state of the layer in contact with the negative electrode of the device.

Comparative Example 2 A device was prepared in the same manner as in Example 1 except that 1,4-bis (2-methylstyryl) benzene (DSB) was used as the material for the adhesion improving layer. The obtained device emitted blue light. Table 2 shows the dipole energy of the surface energy and the light emitting state of the adhesion improving layer of the device.

Comparative Example 3 The following compounds were used as materials for the adhesion improving tank.

[0057]

[Chemical formula 24]

An element was manufactured in the same manner as in Example 1 except that was used. The surface of the Mg: Ag electrode of the obtained device was gray. The obtained device emitted blue light. Table 2 shows the dipole energy of the surface energy and the light emitting state of the adhesion improving layer of the device.

[0059]

[Table 2]

Comparative Example 4 A device was prepared in the same manner as in Example 8 except that the adhesion improving layer (Exemplified Compound 74) was not provided. The device emitted blue light, but non-uniform light emission occurred due to the generation of many small dark spots. Further, the half-life was 10 hours or less when continuously driven in dry nitrogen at an initial stage of 100 cd / m ² .
In addition, β _s ² of 4,4′-bis [2- (4-phenylquinolyl)] biphenyl was 2.8 dyn / cm.

[0061]

The organic element of the present invention has a dipole component of 4d.
By inserting an adhesion improving layer of yn / cm or more between the organic layer and the cathode, the adhesion between the organic substance and the cathode was improved, and uniform light emission was made possible. Therefore, the organic EL device of the present invention can be effectively used as various display devices and light emitting devices.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a method of measuring a contact angle θ.

FIG. 2 is a graph showing the relationship between β _L / α _L and (1 + cos θ) γ _L / 2α _{L in} the formula (A) for obtaining the surface energy.

[Explanation of symbols]

 1: Liquid 2: Contact improvement material

Claims (9)

[Claims] 1. An organic electroluminescence device having an adhesion improving layer between a cathode and an organic layer, wherein the dipole component of the surface energy of the adhesion improving layer is 4 dyn / cm or more. . 2. The adhesion improving layer has the general formula (I): (In the formula, k, l, m, and n each represent an integer of 0 to 5. However, the case where k = l = m = n = 0 is excluded.
r is (In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms or halogen, R ² and R ³ each represent hydrogen, an alkyl group having 1 to 6 carbon atoms or halogen, and p represents 1 to 4 An integer, q and r each represent an integer of 0 to 4, provided that R ¹ , R ² and R ³ may be the same or different from each other)). Organic electroluminescent device. 3. The adhesion improving layer has the general formula (II): (In the formula, Z ¹ and Z ² each independently represent an unsubstituted or substituted aromatic group. Here, the substituent is an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a cyano group, Represents chlorine, bromine, or fluorine, Y ¹ and Y ² each independently represents an unsubstituted or aromatic group having an alkyl group having 1 to 5 carbon atoms, and Q represents —O—, —CH ₂ —, — CH
_2- CH ₂ — or —C (CH ₃ ) ₂ — and X is —
Indicates O- or -S-. The organic electroluminescent element of Claim 1 which consists of a compound represented by these. 4. The adhesion improving layer has the general formula (III): (In the formula, A is a single _{bond, -O -, - SO 2 -} , - S -, -
CH = CH-, -CO-, (In the formula, s represents an integer of 1 to 3). B ¹ , B
² are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms,
It represents an unsubstituted or substituted aryl group having 6 to 18 carbon atoms or an unsubstituted or substituted heterocyclic residue having 3 to 12 carbon atoms. Here, the substituents are nitro group, amino group, cyano group, hydroxyl group, carboxyl group, methylthio group, ethylthio group, halogen, alkoxy group having 1 to 6 carbon atoms, alkoxycarbonyl group having 1 to 6 carbon atoms, and 2 carbon atoms. A dialkylamino group having 8 to 8 carbon atoms, a dialkyleneoxy group having 2 to 8 carbon atoms, an alkylenedioxy group having 1 to 6 carbon atoms, or an alkyleneoxy group having 1 to 6 carbon atoms. B ¹ and B ² may be the same or different. The organic electroluminescent element of Claim 1 which consists of a compound represented by these. 5. An organic electroluminescent device having an adhesion improving layer between a cathode and an electron injection layer, wherein the dipole component of the surface energy of the adhesion improving layer is 4 dyn / c.
An organic electroluminescence device having a thickness of at least m. 6. The organic electroluminescence device according to claim 1, wherein an anode / hole injection layer / light emitting layer / electron injection layer / adhesion improving layer / cathode are laminated in this order. 7. The organic electroluminescence device according to claim 6, wherein the adhesion improving layer comprises the compound represented by the general formula (I) according to claim 2. 8. The adhesion-improving layer has the general formula (I) as defined in claim 3.
The organic electroluminescence device according to claim 6, comprising the compound represented by I). 9. The adhesion-improving layer has the general formula (II) according to claim 4.
The organic electroluminescence device according to claim 6, comprising the compound represented by I).