JPH11162652A - Organic el element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a high element performance and a high mass productivity by forming a lower electrode on a base and thereon a light emission part, and further thereon forming a counter electrode consisting of a protection electrode layer formed by the vacuum evaporation method and a main electrode layer formed by the induction coupling magnetron sputtering method. SOLUTION: A lower electrode to serve as a positive electrode is made on a base material made of glass, etc., and thereon an organic light emission layer is made, and further thereon a counter electrode of negative electrode is formed so that an organic EL element is accomplished. This counter electrode is composed of a protection electrode layer and a main electrode layer. The protection electrode layer is formed on the light emission layer by the vacuum evaporation method so as to suppress drop of the function of the light emission layer and to generate a good interface, wherein the film thickness should preferably be made 5-20 nm by the use of a metal such as Mg having a work function of 4 eV or less. The main electrode layer is formed uniformly and in good quality in mass-production by the induction coupling magnetron sputtering method, wherein the film thickness should preferably be made 50-300 nm by the use of a conductive metal, metal oxide, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an organic electroluminescence (hereinafter referred to as "E
L ". A) an element and a method for manufacturing the same.

[0002]

2. Description of the Related Art An organic EL device has a structure in which holes injected directly into an organic light emitting layer from an anode or through a hole injection layer and electrons injected into the organic light emitting layer directly from a cathode or through an electron injection layer. Are elements that emit light (EL light) by recombination. The organic EL element can emit light with a significantly lower applied voltage than the inorganic EL element, and can perform display with low viewing angle dependence when the organic EL element is used as a pixel. . Therefore, a display device using an organic EL element as a pixel (organic E
L display device), and a surface light source using an organic EL element are being actively developed.

In recent years, organic EL devices have been actively improved through organic light emitting materials, electron injecting materials, hole injecting materials, counter electrode materials, and the like, and device performance such as device life and luminous efficiency has been greatly increased. Improved. Among them, a counter electrode made of an alloy such as Al: Li, Mg: Ag or the like by a vacuum evaporation method (which means an electrode formed directly or through a predetermined layer on the light emitting portion after the light emitting portion is formed. The same applies hereinafter. The organic EL element formed with (.) Has high element performance.

In order to obtain an organic EL display device, first, a large number of organic EL elements (pixels) are formed on a substrate to obtain an organic EL display panel. In order to make the characteristics uniform and the sheet resistance of the organic EL display panel uniform, it is necessary to form the layers constituting the organic EL element over a wide range with uniform thickness.

The use of a vacuum deposition method as a means for forming the counter electrode is suitable for obtaining an organic EL element having high element performance, but from the viewpoint of forming a counter electrode having a uniform film thickness over a wide range. Is not very suitable. In addition, when an opposite electrode containing a metal that easily reacts with an evaporation source for vacuum deposition such as aluminum (Al) is formed by a vacuum deposition method, it is difficult to continuously form the counter electrode. Is reduced.

The viewpoint of forming a counter electrode having a uniform film thickness over a wide range, the viewpoint of forming the counter electrode under high mass productivity, and the intrusion of oxygen or moisture into the light emitting portion through the counter electrode to form an organic electrode From the viewpoint of suppressing a decrease in the durability (device life) of the EL element by forming a dense counter electrode, it is preferable to form the counter electrode by a sputtering method.

However, according to the study by the present inventors, when the counter electrode is formed by the sputtering method, high-speed electron beams, neutral or ionized high-energy atoms, ultraviolet rays, and the like are generated, and due to these, the counter electrode is formed. When the underlying layer is an organic material layer (an organic light emitting layer or an electron injection layer or a hole injection layer made of an organic material), the organic material layer is easily damaged. When the organic material layer is damaged, the light emitting characteristics of the organic EL element are deteriorated such as the occurrence of a non-light emitting point (dark spot).

The damage of the organic layer by high-speed electron beams, high-energy atoms, ultraviolet rays, and the like generated when the counter electrode is formed by the sputtering method is as follows.
Appl. Phys. Lett. 68 (19), 1996 (hereinafter referred to as “Document I”), pages 2606 to 2608, the organic EL element has a two-layer structure of the counter electrode, In addition, it is possible to suppress the input power at the time of sputtering by keeping it small. In the above-mentioned Document I, an RF magnetron sputtering method in which a thin film made of an alloy such as Mg: Ag having a small work function is formed on an organic light emitting layer (Alq ₃ layer) by a vacuum evaporation method, and then the input power is suppressed small. Describes an organic EL element in which an ITO thin film is formed on a thin film made of the above-described alloy, thereby forming a two-layer counter electrode composed of a thin film made of an alloy and an ITO thin film.

[0009]

The organic EL device described in Document I has an advantage that the organic light emitting layer can be prevented from being damaged when an ITO thin film is formed by RF magnetron sputtering. However, since the input power during RF magnetron sputtering is kept small, the film forming rate is as low as 0.05 angstroms / second, and the ITO thin film having a desired film thickness (the thickness of the ITO thin film in the organic EL device of Document I is 400 Angstroms) takes a long time to form. Therefore, mass productivity is low.

An object of the present invention is to provide an organic EL device capable of obtaining a device having high device performance under high productivity, and a method of manufacturing the same.

[0011]

According to the present invention, there is provided an organic EL device comprising: a base; a lower electrode formed on the base; and a light emitting layer formed on the lower electrode. And a counter electrode formed on the light emitting section, wherein the counter electrode is formed of a protective electrode layer formed on the light emitting section by a vacuum evaporation method and an inductively coupled magnetron sputtering method ( I nductively C oupled M agnetron S putte
ring method; hereinafter abbreviated as “ICMS method”. ) And a main electrode layer formed on the protective electrode layer.

On the other hand, a method of manufacturing an organic EL device according to the present invention for achieving the above object comprises forming a lower electrode on a base material, forming a light emitting portion on the lower electrode, and forming a counter electrode on the light emitting portion. In forming the organic EL element by forming the above, the counter electrode was formed into a two-layer structure of a protective electrode layer and a main electrode layer, and the protective electrode layer was formed on the light emitting portion by a vacuum deposition method. Thereafter, the main electrode layer is formed on the protective electrode layer by an ICMS method.

[0013]

Embodiments of the present invention will be described below in detail. First, the organic EL device of the present invention will be described. The organic EL element of the present invention, as described above, a base material, a lower electrode formed on the base material,
It has a light-emitting portion formed on the lower electrode and a counter electrode formed on the light-emitting portion, and has a two-layer structure in which the counter electrode is formed by a specific method.

Here, the term "lower electrode" as used in the present invention means an electrode formed on a base material prior to the formation of a light emitting portion, and the lower electrode may be used as an anode or may be used as a cathode. May be used. When the lower electrode is used as an anode, the counter electrode is used as a cathode. When the lower electrode is used as a cathode, the counter electrode is used as an anode.

The most significant feature of the organic EL device of the present invention is that each layer constituting the counter electrode having a two-layer structure is a specific one formed by a specific method. Therefore,
First, the counter electrode will be described, and other components will be described later.

As described above, the above-mentioned counter electrode is composed of a protective electrode layer and a main electrode layer formed on the protective electrode layer.
It has a layered structure. The above-described protective electrode layer suppresses the function of the underlying layer (organic light emitting layer, electron injection layer, or hole injection layer) from being reduced when the protective electrode layer is formed. In order to form a good interface with the layer to be formed, it is formed by a vacuum deposition method.

When the counter electrode is used as a cathode,
An alkaline earth metal (Mg, Sr, Ba, Ca, etc.) or an alkali metal (L) is used so that electrons can be well injected into the underlying layer (in this case, an organic light emitting layer or an electron injection layer).
Preferably, the protective electrode layer is formed of a metal having a small work function (about 4 eV or less), such as i, Na, K, Rb, and Cs, or an alloy or a mixture of these metals. Further, since the above-mentioned metals, alloys or mixtures are not said to have good film properties, in order to compensate for this, metals having good film properties (for example, Ag, Al, etc. ) are added to the above-mentioned metals, alloys or mixtures. The above alloy (when a metal is contained) containing approximately 99.9 at% or less, or a mixture containing 99.9 mol% or less of an organic substance having good film properties (for example, a metal complex of an 8-quinolinol derivative) is contained. A protection electrode may be formed.

When the counter electrode is used as a cathode, the thickness of the protective electrode layer is set so that (1) electrons can be injected into the underlying layer (organic light emitting layer or electron injection layer) with high efficiency. (2) to prevent the underlying layer from being damaged during the formation of the main electrode layer described below;
(3) From the viewpoint of securing high mass productivity, etc.
The thickness is preferably 0 nm, more preferably about 7 to 12 nm.

On the other hand, when the counter electrode is used as an anode, the work function is generally set so that holes are well injected into the underlying layer (in this case, the organic light emitting layer or the hole injection layer). A conductive material of 4.5 eV or more (for example, Au, N
i, Cu, Pt, Ag, Pd, etc.).

In the case where the counter electrode is used as an anode, the thickness of the protective electrode layer is such that (a) electrons can be injected into the underlying layer (organic light emitting layer or hole injection layer) with high efficiency. From 5 to 20 nm from the viewpoint of (b) suppressing damage to the underlying layer when forming a main electrode layer described later, (c) securing high mass productivity, and the like. Preferably, the thickness is more preferably about 7 to 12 nm.

The main electrode layer formed on the above-mentioned protective electrode layer bears the bulk properties (resistivity, etc.) of the counter electrode, and the ratio of the main electrode layer to the counter electrode is high. For this reason, in the organic EL device of the present invention, a uniform and high-quality main electrode layer is formed under high mass productivity while suppressing the layer underlying the protective electrode layer from being damaged during the formation of the main electrode layer. In forming the main electrode layer, the ICM
It is formed by the S method.

When the counter electrode is used as a cathode, the above-mentioned main electrode layer may be formed of the same material as the above-mentioned protective electrode layer, or may be made of another conductive material such as a conductive metal or
It may be formed of a conductive oxide such as n-Sn-O-based or In-Zn-O-based. As described above, since the protective electrode layer is a thin layer, when the main electrode layer is formed of a transparent conductive oxide on the protective electrode layer, the light extraction surface is formed on the main electrode layer side (counter electrode side). It can also be used as In the case where an In-Zn-O-based amorphous conductive oxide is used as a material for the main electrode layer, a main electrode layer having low electric resistance can be formed at room temperature or room temperature. It is easier to prevent the layer serving as the base from being damaged during the formation of the main electrode layer.

When the counter electrode is used as a cathode, the thickness of the main electrode layer may be made as large as possible in order to obtain a counter electrode having a small electric resistance.
In order to prevent the organic light emitting layer or the electron injection layer from being damaged at the time of forming the main electrode layer, it is generally required to be 50 to 3 mm.
The thickness is preferably set to 00 nm, and more preferably to about 100 to 200 nm.

On the other hand, when the counter electrode is used as the anode, the main electrode layer may be formed of a material having a work function of about 4.5 eV or more, as in the case of the protective electrode layer, or in the same manner as when the counter electrode is used as the cathode. Alternatively, the conductive oxide may be formed using the conductive oxide. The thickness of the main electrode layer when the counter electrode is used as the anode is preferably about 50 to 300 nm, more preferably about 100 to 200 nm, from the same viewpoint as when the counter electrode is used as the cathode. preferable.

The organic EL device of the present invention has the above-mentioned specific counter electrode, and a desired light emission (EL) is obtained by applying a voltage between the counter electrode and the lower electrode formed on the substrate. Light) can be obtained, and the layer configuration other than the counter electrode can be appropriately selected.

Specific examples of the layer structure of an organic EL device of the type using the lower electrode as an anode are described in (1) to (1) below.
(4) That is, (1) lower electrode (anode) / organic light emitting layer / counter electrode (cathode) (2) lower electrode (anode) / hole injection layer / organic light emitting layer / counter electrode (cathode) (3) Lower electrode (anode) / organic light emitting layer / electron injection layer / counter electrode (cathode) (4) Layer structure of lower electrode (anode) / hole injection layer / organic light emitting layer / electron injection layer / counter electrode (cathode) No.

Specific examples of the layer structure of the organic EL device of the type using the lower electrode as a cathode include the following (A) to (D): (A) lower electrode (cathode) / organic light emitting layer / facing Electrode (anode) (B) Lower electrode (cathode) / organic light emitting layer / hole injection layer / counter electrode (anode) (C) Lower electrode (cathode) / electron injection layer / organic light emitting layer / counter electrode (anode) ( D) A layer configuration of lower electrode (cathode) / electron injection layer / organic light-emitting layer / hole injection layer / counter electrode (anode).

Organic E of the type (1) or (A) above
In the L element, the organic light emitting layer corresponds to the light emitting portion according to the present invention. In the organic EL element of the above-mentioned type (2) or (B), the laminate of the hole injection layer and the organic light emitting layer is the present invention. In the organic EL device of the type (3) or (C), a laminate of an organic light emitting layer and an electron injection layer corresponds to the light emitting portion according to the present invention, In the organic EL device of the type (D), a laminate of a hole injection layer, an organic light emitting layer, and an electron injection layer corresponds to the light emitting portion in the present invention.

There are an organic EL device in which a hole transport layer is used in place of the hole injection layer, and an organic EL device in which a hole transport layer is used together with the hole injection layer. The “hole injection layer” is a general term for a single layer of a hole injection layer, a single layer of a hole transport layer, and a laminate of a hole injection layer and a hole transport layer, unless otherwise specified.

Hereinafter, each layer including the base material (however, the counter electrode has already been described and will not be described here) will be specifically described. (A) Substrate When the substrate side is the light extraction surface, a transparent substrate is used as the substrate. The transparent base material is preferably made of a material that gives high transparency (approximately 80% or more) to light emission (EL light) from the light emitting portion, and specific examples thereof include alkali glass and alkali-free glass. Transparent glass or transparent resin such as polyethylene terephthalate, polycarbonate, polyethersulfone, polyetheretherketone, polyvinyl fluoride, polyacrylate, polypropylene, polyethylene, amorphous polyolefin, fluorine-based resin, or plate-like made of quartz Object, a sheet-like object, or a film-like object. What kind of transparent substrate is used can be appropriately selected depending on the intended use of the organic EL device and the like. On the other hand, when the substrate side is not used as the light extraction surface, a substrate other than the above-described transparent substrate can be used as the substrate. In this case, the base material may be an inorganic substance or an organic substance.

(B) Lower electrode When the lower electrode is used as an anode, a metal, an alloy, an electrically conductive compound or a mixture thereof having a large work function (about 4 eV or more) is preferably used as a material thereof. Specific examples include metals such as Au, CuI, ITO,
Examples include conductive transparent materials such as tin oxide, zinc oxide, and In-Zn-O-based amorphous conductive oxide. The thickness of the lower electrode in this case depends on the material, but is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm. On the other hand, when the lower electrode is used as a cathode, its material has a small work function (for example, 4 eV
Hereinafter) metals, alloys, electrically conductive compounds or mixtures thereof are preferably used. Specific examples include Na, N
a-K alloy, Mg, Li, alloy or mixed metal of Mg and Ag, Mg-Cu mixture, Al, Al / Al ₂ O ₃ ,
Al-Li alloys, rare earth metals such as In and Yb and the like can be mentioned. The thickness of the lower electrode in this case depends on the material, but is usually selected in the range of 10 nm to 1 μm. In addition, when light emission (EL light) from the light emitting portion is taken out from the base material side, the transmittance of the EL light at the lower electrode is preferably 10% or more. Further, the sheet resistance of the lower electrode is preferably several hundred Ω / □ or less.

(C) Organic Light-Emitting Layer The organic light-emitting layer is usually formed of one or more kinds of organic light-emitting materials, and a mixture of the organic light-emitting material and a hole injection material and / or an electron injection material described later or In some cases, the mixture or the polymer material in which the organic light emitting material is dispersed is formed. The organic light emitting material used as the material of the organic light emitting layer has the following functions: (a) charge injection function, that is, holes can be injected from an anode or a hole injection layer when an electric field is applied, and electrons can be injected from a cathode or an electron injection layer. Functions that can be injected, (b) transport functions, i.e.
The function of moving injected holes and electrons by the force of an electric field, and (c) the function of emitting light, that is, the function of providing a field of recombination of electrons and holes and connecting them to light emission. Any combination is acceptable, but the above (a) to (c)
It is not always necessary to have sufficient performance for each of the functions described above.For example, among those having a hole injection / transport property larger than the electron injection / transport property, some of them are suitable as organic light emitting materials. . As the organic light emitting material, for example, a benzothiazole-based, benzimidazole-based, benzoxazole-based fluorescent whitening agent, a styrylbenzene-based compound, or the like can be used.

As a specific example of the above-mentioned fluorescent whitening agent, benzoxazole based 2,5-bis (5,7-di-t-
Pentyl-2-benzoxazolyl) -1,3,4-thiadiazole, 4,4′-bis (5,7-t-pentyl-2-benzooxazolyl) 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]
Examples include benzoxazole, 2- [2- (4-chlorophenyl) vinyl] naphtho [1,2-d] oxazole, and benzothiazole-based compounds include 2,2 '-(p-phenylenedivinylene) -bisbenzothiazole. And in the benzimidazole system, 2- [2- [4- (2-
Benzimidazolyl) phenyl] vinyl] benzimidazole, 2- [2- (4-carboxyphenyl) vinyl] benzimidazole and the like. In addition, other useful compounds are described in Chemistry of Synthetic Soy (1971), pages 628-637 and 6
Listed on page 40.

Specific examples of the above styrylbenzene compounds 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-methylbenzene, 1,4-bis (2-methylstyryl)-
2-ethylbenzene and the like.

Further, in addition to the above-described fluorescent whitening agents and styrylbenzene compounds, for example, 12-phthaloperinone, 1,4-diphenyl-1,3-butadiene,
1,4,4-tetraphenyl-1,3-butadiene, naphthalimide derivative, perylene derivative, oxadiazole derivative, aldazine derivative, pyrazin derivative, cyclopentadiene derivative, pyrrolopyrrole derivative, styrylamine derivative, coumarin compound, international Publication WO
90/13148 and Appl.Phys.Lett., Vol 58, 18, P1982
(1991), a high molecular compound, an aromatic dimethylidin compound, and a compound represented by the following general formula (I):

Embedded image Can be used as the organic light emitting material.

Here, specific examples of the aromatic dimethylidyl-based compound include 1,4-phenylenedimethylidin, 4,4'-phenylenedimethylidin, 2,5-xylylenedimethylidin, 2,6 -Naphthylenedimethylidin, 1,4-biphenylenedimethylidin, 1,4
-P-terephenylenedimethylidin, 4,4'-bis (2,2-di-tert-butylphenylvinyl) biphenyl, 4,4'-bis (2,2-diphenylvinyl) biphenyl, and the like, and the like. Derivatives. Also,
Specific examples of the compound represented by the general formula (I) include:
Bis (2-methyl-8-quinolinolate) (p-phenylphenolate) aluminum (III), bis (2-methyl-8-quinolinolate) (1-naphtholate) aluminum (III) and the like can be mentioned.

In addition, a compound in which the above-mentioned organic light emitting material is used as a host and the host is doped with a strong fluorescent dye from blue to green, for example, a coumarin-based fluorescent dye or a fluorescent dye similar to the above-mentioned host is also suitable as the organic light emitting material. .
When the above compound is used as the organic light emitting material, blue to green light emission (emission color varies depending on the type of dopant) can be obtained with high efficiency. Specific examples of the host as the material of the compound include an organic light-emitting material having a distyrylarylene skeleton (particularly preferably, for example, 4,
4'-bis (2,2-diphenylvinyl) biphenyl)
Specific examples of the dopant which is a material of the compound include diphenylaminovinylarylene (particularly preferably, for example, N, N-diphenylaminobiphenylbenzene) and 4,4′-bis [2- [4- (N , N-di-p-tolyl) phenyl] vinyl] biphenyl).

The organic light emitting layer is particularly preferably a molecular deposition film. Here, the molecular deposition film refers to a thin film formed by deposition from a material compound in a gaseous state or a film formed by solidification from a material compound in a solution state or a liquid phase state. Can be distinguished from a thin film (molecule accumulation film) formed by the LB method by a difference in an aggregated structure and a higher-order structure and a functional difference caused by the difference. There is no particular limitation on the thickness of the organic light emitting layer,
Although it can be appropriately selected according to the situation, it is usually 5 nm.
The range is preferably from 5 to 5 μm.

(D) Hole Injection Layer The material of the hole injection layer provided as needed (hereinafter referred to as “hole injection material”) has hole injection properties or electron barrier properties. Any material may be used as long as it has been conventionally used as a hole injecting material for an electrophotoreceptor.
^-5 cm ² / V · s (electric field intensity 10 ⁴ to 10 ⁵ V / cm)
Those described above are preferred. The hole injection material may be either an organic substance or an inorganic substance.

Specific examples include triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives,
Styryl anthracene derivative, fluorenone derivative, hydrazone derivative, stilbene derivative, silazane derivative,
Polysilane, aniline copolymer, conductive polymer oligomer (especially thiophene oligomer), porphyrin compound, aromatic tertiary amine compound, styrylamine compound, the above-mentioned aromatic dimethylidin compound shown as an organic light emitting material, p-type And inorganic semiconductors such as -Si and p-type SiC.

As the hole injecting material, it is preferable to use a porphyrin compound, an aromatic tertiary amine compound or a styrylamine compound, and it is particularly preferable to use an aromatic tertiary amine compound. Specific examples of the porphyrin compound include porphine, 1,10,15,2
0-tetraphenyl-21H, 23H-porphine copper (II), 1,10,15,20-tetraphenyl-21
H, 23H-porphine zinc (II), 5,10,15,
20-tetrakis (pentafluorophenyl) -21
H, 23H-porphine, silicon phthalocyanine oxide, aluminum phthalocyanine chloride, phthalocyanine (metal-free), dilithium phthalocyanine, copper tetramethyl phthalocyanine, copper phthalocyanine, chromium phthalocyanine, zinc phthalocyanine, lead phthalocyanine, titanium phthalocyanine oxide, magnesium phthalocyanine, copper octa Methyl phthalocyanine and the like.

Specific examples of the aromatic tertiary amine compound and styrylamine compound include N, N,
N ', N'-tetraphenyl-4,4'-diaminophenyl, N, N'-diphenyl-N, N'-bis- (3-
Methylphenyl)-[1,1′-biphenyl] -4,
4'-diamine, 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-tolylaminophenyl) 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-diphenylaminostilbene, N-phenylcarbazole ,
A compound having two condensed aromatic rings in the molecule, such as 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl, in which three triphenylamine units are linked in a star burst form 4,4 ', 4 "-tris [N- (3-methylphenyl) -N-phenylamino]
Triphenylamine and the like.

The thickness of the hole injection layer is not particularly limited.
Usually, it is 5 nm to 5 μm. The hole injection layer may have a single-layer structure composed of one or more hole injection materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions.

(E) Electron Injection Layer The material of the electron injection layer provided as needed (hereinafter referred to as “electron injection material”) has a function of transmitting electrons injected from the cathode to the organic light emitting layer. Anything is acceptable. Generally, it is desirable that the electron affinity is higher than the electron affinity of the organic light emitting material and lower than the work function of the cathode (the minimum when the cathode is a multi-component). However, if the energy level difference becomes extremely large, a large electron injection barrier exists there, which is not preferable. The electron affinity of the electron injecting material is preferably about the same as the work function of the cathode or the electron affinity of the organic light emitting material. The electron injection material may be either an organic substance or an inorganic substance.

Specific examples include nitro-substituted fluorenone derivatives, anthraquinodimethane derivatives, diphenylquinone derivatives, thiopyrandioxide derivatives, heterocyclic tetracarboxylic anhydrides such as naphthaleneperylene, carbodiimides, fluorenylidenemethane derivatives, anthrones Derivatives, oxadiazole derivatives, JP-A-59-19439
No. 3 discloses a series of electron-transporting compounds disclosed as a material for an organic light-emitting layer, a thiazole derivative in which an oxygen atom of an oxadiazole ring is substituted with a sulfur atom, and a quinoxaline ring known as an electron-withdrawing group. Metal complexes of quinoxaline derivatives, 8-quinolinol derivatives (for example, tris (8-quinolinol) aluminum, tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum, tris ( 2-methyl-8-quinolinol)
Aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc and the like, and the central metal of these metal complexes is In, Mg, C
u, Ca, Sn, Ga, or Pb), metal-free or metal phthalocyanine or those whose terminals are substituted with an alkyl group, a sulfone group, or the like; Inorganic semiconductors such as styrylpyrazine derivatives and n-type-Si and n-type-SiC are exemplified.

The thickness of the electron injection layer is not particularly limited.
Usually, it is 5 nm to 5 μm. The electron injection layer may have a single-layer structure composed of one or more electron injection materials, or may have a multilayer structure composed of a plurality of layers having the same composition or different compositions.

In the organic EL device of the present invention having the above-described layer structure, the counter electrode has a two-layer structure of the protective electrode layer and the main electrode layer, and the protective electrode and the main electrode layer are viewed from the light emitting portion. Are stacked in this order. Since the protective electrode layer provided on the light emitting portion is an ultrathin film having a thickness of about 5 to 20 nm formed by a vacuum evaporation method, the light emitting portion is damaged when the protective electrode layer is formed. Is less likely to occur, and its mass productivity is relatively high. Further, since the main electrode layer provided on the protective electrode layer is formed by the ICMS method, it is difficult for the light emitting portion to be damaged when the main electrode layer is formed, and Even if the electrode layer is formed over a wide range, the uniformity of the film thickness and the mass productivity are both high.

Therefore, the organic EL device of the present invention is an organic EL device capable of obtaining a device having high device performance under high productivity. The organic EL device of the present invention having the above advantages is suitable as a pixel or a surface light source of an organic EL display panel.

When a gas such as oxygen or moisture enters the organic EL element, the performance of the organic EL element is reduced.
The organic EL device of the present invention may have a sealing layer for preventing gas such as oxygen or moisture from entering the device.

The material of the sealing layer is organic E to be sealed.
It can be appropriately selected according to the use of the L element. Specific examples of the material of the sealing layer include, for example, a copolymer obtained by copolymerizing a monomer mixture containing tetrafluoroethylene and at least one comonomer, a fluorine-containing copolymer having a cyclic structure in the copolymer main chain. Polymer, polyethylene, polypropylene, polymethyl methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichlorodifluoroethylene, copolymer of chlorotrifluoroethylene and dichlorodifluoroethylene, water absorption of 1% or more Water-absorbing substance and moisture-proof substance having a water absorption of 0.1% or less, In, Sn, P
metals such as b, Au, Cu, Ag, Al, Ti, Ni, M
gO, SiO, SiO ₂ , Al ₂ O ₃ , GeO, Ni
Metal oxides such as O, CaO, BaO, Fe ₂ O ₃ , Y ₂ O ₃ , TiO ₂ , MgF ₂ , LiF, AlF ₃ , CaF ₂
And fluorinated hydrocarbons such as metal fluorides such as perfluoroalkanes, perfluoroamines and perfluoropolyethers, and those obtained by dispersing an adsorbent for adsorbing moisture and oxygen into the liquid fluorinated hydrocarbons. .

The above-described organic EL device of the present invention can be obtained, for example, by the method for manufacturing an organic EL device of the present invention described in detail below. As described above, in the method for manufacturing an organic EL device of the present invention, a lower electrode is formed on a base material, a light emitting portion is formed on the lower electrode, and a counter electrode is formed on the light emitting portion. In obtaining an element, the counter electrode has a two-layer structure of a protective electrode layer and a main electrode layer, and
After the protective electrode layer is formed on the light emitting portion by a vacuum deposition method, the main electrode layer is formed on the protective electrode layer by an ICMS method.

Here, the method of forming the lower electrode and the light emitting portion is not particularly limited, but may be PVD, CVD, spin coating, casting, LB, etc., depending on the material of the layer to be formed. The method can be applied as appropriate. If a vacuum deposition apparatus is used to form the lower electrode and the light emitting section, it is possible to form from the lower electrode to the protective electrode layer to be described later by only this vacuum deposition apparatus, so that the equipment can be simplified and the production time can be shortened. Is advantageous. At that time, each layer is formed continuously,
That is, it is preferable to perform the process without breaking the vacuum even once between the formation of a certain layer A and the formation of the next layer B.

In the method of the present invention, after the light emitting portion is formed as described above, a protective electrode layer is formed on the light emitting portion by a vacuum deposition method, and then the IC is formed on the protective electrode layer.
A main electrode layer is formed by the MS method. Since the material and thickness of the protective electrode layer and the material and thickness of the main electrode layer have already been described in the description of the organic EL device of the present invention, the film forming conditions of each layer will be described here.

In forming the protective electrode layer by the vacuum deposition method, the degree of vacuum (vacuum pressure) at the time of film formation is set to 1 × 10
^-3 Pa, preferably 1 × 10 ^-4 Pa
More preferably, the pressure is lower. In addition, the substrate temperature during film formation does not need to be adjusted, but it is possible to cool or heat the substrate (the substrate after forming the light emitting unit) within a range that does not adversely affect the light emitting unit. Good. The shape and heating method of the evaporation source in the vacuum deposition method are not particularly limited, and can be appropriately selected in consideration of the shape and size of the organic EL element to be obtained, mass productivity, and the like.

On the other hand, when forming the main electrode layer by the ICMS method, the degree of vacuum (vacuum pressure) at the time of film formation is 1 ×.
10 ⁰ to 1 × and 10 ^-2 Pa or so, and (generally 50~200W inductively coupled coil input power) roughly 200-300 gauss strength of the magnetron magnetic field, be generally 13.56~100MHz the RF frequency Is preferred. The substrate temperature during film formation can be, for example, 80 ° C. or lower.

A protective electrode layer is formed on the light emitting portion by the above-described vacuum deposition method, and the above-described ICM is formed on the protective electrode layer.
In the method of the present invention in which the main electrode layer is formed by the S method, since the protective electrode layer to be formed has a very thin film thickness of about 5 to 20 nm, it is difficult to react with a metal such as Al that easily reacts with an evaporation source for vacuum deposition. , It is possible to obtain relatively high mass productivity even in the case where a protective electrode layer containing is intended. In addition, since the protective electrode layer is formed by a vacuum evaporation method, it is possible to suppress the deterioration of the function of the underlying layer of the protective electrode and to improve the interface between the underlying layer and the protective electrode layer. It can be.

Further, a main electrode layer as a layer having a bulk property of the counter electrode is formed by an ICMS method. In the ICMS method, a substrate (a base material after forming a protective electrode layer) and a sputtering cathode are formed. And 20 for example
cm or more, so that the light-emitting part can be easily prevented from being damaged by high-speed electron beams, neutral or ionized high-energy atoms, ultraviolet rays, etc. generated during sputtering (at the time of forming the main electrode layer). Can be. In addition, even when a small sputtering target is used, a main electrode layer having high uniformity in film thickness can be formed over a wide range. In spite of the large T / S (distance between the substrate and the sputtering cathode), the film deposition rate can be increased to, for example, 1 Å / sec or more, and the evaporation source for vacuum deposition such as Al can be used. Even when a main electrode layer containing a metal that easily reacts is to be formed, high mass productivity can be obtained.
As a result, according to the method of the present invention, it is possible to obtain an organic EL device having high device performance under high mass productivity.

In the case where the sealing layer described in the description of the organic EL device of the present invention is formed, a vacuum deposition method, a sputtering method, a MB method, or the like is used depending on the material of the sealing layer.
E (molecular beam epitaxy) method, cluster ion beam evaporation method, ion plating method, plasma polymerization method (high frequency excitation ion plating method), reactive sputtering method, plasma CVD method, laser CVD method, thermal CV
Methods such as the D method, the gas source CVD method, the spin coating method, and the casting method can be appropriately applied.

When a liquid material such as a liquid fluorinated hydrocarbon or an adsorbent for adsorbing moisture or oxygen is dispersed in the liquid fluorinated hydrocarbon as the material of the sealing layer, the liquid fluorinated hydrocarbon is formed on a substrate. A housing material that covers the light emitting element while forming a gap between the light emitting element and the light emitting element in cooperation with the base material outside the light emitting element (there may be another sealing layer). It is preferable to form a sealing layer by filling the space formed by the base material and the housing material with the liquid material. As the housing material, a material made of glass or a polymer (for example, ethylene trifluoride chloride) having a small water absorption is preferably used. When using a housing material, only the housing material may be provided without providing the above-described sealing layer, or a space formed by the housing material and the base material after the housing material is provided. A layer of an adsorbent for adsorbing oxygen or water may be provided on the substrate, or particles of the adsorbent may be dispersed.

[0060]

Embodiments of the present invention will be described below. Example 1 First, an ITO transparent electrode (corresponding to a lower electrode) having a thickness of 100 nm was formed on a glass plate having a length of 25 mm, a width of 75 mm, and a thickness of 1.1 mm (hereinafter referred to as a “substrate with a lower electrode”). .) Was prepared. After the substrate with the lower electrode was ultrasonically cleaned in an organic solvent, a dry nitrogen gas was blown to remove the organic solvent from the surface of the ITO transparent electrode. Thereafter, UV / ozone cleaning was performed to remove organic substances from the surface of the ITO transparent electrode.

Next, a vacuum evaporation chamber having an evaporation source of a resistance heating type and an inductively coupled magnetron sputtering chamber (hereinafter, an inductively coupled magnetron sputtering chamber is referred to as “IC
MS room ". ), And a hole injection layer and an organic light-emitting layer are formed on the ITO transparent electrode of the substrate with the lower electrode after cleaning under the following conditions by using the high vacuum evaporation apparatus. The layer, the protective electrode layer and the main electrode layer were sequentially laminated in this order to obtain an organic EL device. At this time, an organic EL device was manufactured without breaking the vacuum even once between the formation of the hole injection layer and the formation of the main electrode layer.

First, the substrate with the lower electrode was mounted on a substrate holder in a vacuum evaporation chamber. Then, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (hereinafter abbreviated as “NPD”) is used as a hole injecting material, and the NPD is subjected to a vacuum degree of 5. Vapor deposition was performed under the conditions of 0 × 10 ⁻⁵ Pa or less and a vapor deposition rate of 0.1 to 0.3 nm / sec to form a hole injection layer having a thickness of 60 nm. At this time,
The substrate with the lower electrode was not heated or cooled.

Next, tris (8-
Using quinolinol) aluminum (hereinafter abbreviated as "Alq"), this Alq was deposited under the same conditions as in the formation of the above-described hole injection layer to form an organic light emitting layer having a thickness of 60 nm. Next, magnesium (Mg) and silver (Ag) were used as the material of the protective electrode layer, and the degree of vacuum was 1.0 × 10 ⁻⁴ Pa at the time of vapor deposition, the vapor deposition rate of Mg was 1 nm / sec, and Ag was performed by a dual vacuum vapor deposition method. The Mg and Ag were vapor-deposited under the conditions of a vapor deposition rate of 0.1 nm / sec to form a 20 nm-thick protective electrode layer made of a Mg: Ag alloy. After this,
After forming the protective electrode, the substrate with the lower electrode was transferred from the vacuum evaporation chamber to an ICMS chamber evacuated to 1.0 × 10 ⁻⁴ Pa.

Then, the degree of vacuum in the ICMS chamber is 1.3 × 1
After introducing argon gas into the ICMS chamber so as to be 0 ^-1 Pa, an IC using an alloy target of Mg and Ag (the atomic ratio Mg / Ag of Mg and Ag is 10/1) is used.
According to the MS method, an argon gas pressure (atmospheric pressure during sputtering) is 1.3 × 10 ⁻¹ Pa, a magnetron magnetic field strength is 250 gauss (induction coupling coil input power is 50 μm).
W), RF frequency 13.56 MHz, cathode applied voltage 400 V (DC), distance between substrate (substrate after forming protective electrode) and target (cathode) 20 cm, substrate temperature room temperature (non-heating, non-cooling) A main electrode layer having a film thickness of 80 nm was formed underneath. At this time, the film formation rate of the main electrode layer was 0.1 nm / sec, and almost no increase in the substrate temperature was observed during the formation of the main electrode layer.

In addition, regarding the above alloy target,
Prior to transporting the substrate after forming the protective electrode to the ICMS chamber, pre-sputtering was performed to remove impurities such as oxides formed or adhered to the target surface in advance. This pre-sputtering was performed for 5 minutes under the same conditions as when the main electrode layer was formed. The main electrode layer was formed by performing sputtering under the same conditions as in the pre-sputtering with the substrate shutter closed, and after confirming that the sputtering was stabilized, opening the substrate shutter.

By forming up to the above-mentioned main electrode layer, the lower electrode (ITO transparent electrode) and the hole injection layer (NPD) are formed.
Layer), organic light emitting layer (Alq layer), protective electrode layer (Mg: A
g layer) and a main electrode layer (Mg: Ag layer) were sequentially laminated on the above glass plate to obtain an organic EL device. In this organic EL element, the hole injection layer and the organic light emitting layer correspond to the “light emitting portion” in the present invention, and the organic EL element has a two-layered counter electrode of the protective electrode layer and the main electrode layer. have.

Example 2 After forming up to the protective electrode layer under exactly the same conditions as in Example 1,
Al was formed in exactly the same manner as the formation of the main electrode layer in Example 1.
An 80 nm-thick main electrode layer was formed by ICMS to obtain an organic EL device. The conditions at the time of forming the main electrode layer were the same as those in Example 1 except that a sputtering target made of Al was used.
The deposition rate of the main electrode layer was 0.2 nm / sec.

Example 3 After forming up to the protective electrode layer under exactly the same conditions as in Example 1 except that the film thickness of the protective electrode layer was 13 nm, the In- layer was formed in exactly the same manner as the formation of the main electrode layer in Example 1. A 100 nm-thick main electrode layer made of a Zn-O-based amorphous conductive oxide (hereinafter, referred to as "IXO") was formed by an ICMS method to obtain an organic EL device. The conditions for forming the main electrode layer were the same as those in Example 1 except that a sputtering target composed of IXO (In atomic ratio In / (In + Zn) = 0.83) was used.
The deposition rate of the main electrode layer was 0.13 nm / sec.

Example 4 First, an organic light emitting layer was formed under exactly the same conditions as in Example 1, and then a protective electrode having a thickness of 20 nm made of Al and Li was formed in exactly the same manner as the formation of the protective electrode layer in Example 1. The layers were formed by a single vacuum evaporation method. In forming the protective electrode layer, an alloy of Al and Li (Li content was 5 at%) was used as a vapor deposition material. The deposition rate of the protective electrode layer was 1 nm / sec as in Example 1.

Next, an 80 nm-thick main electrode layer made of Al and Li was formed by the ICMS method in exactly the same manner as the formation of the main electrode layer in Example 1 to obtain an organic EL device. The conditions for forming the main electrode layer were the same as those in Example 1 except that a sputtering target composed of an Al: Li alloy (Li content was 5 at%) was used. The film formation rate of the main electrode layer was 0.1 nm / sec as in Example 1.

COMPARATIVE EXAMPLE 1 After forming up to the organic light-emitting layer under the same conditions as in Example 1,
M is formed in exactly the same manner as the formation of the protective electrode layer in Example 1.
A 100 nm-thick counter electrode (single-layer structure) composed of g and Ag was formed by a vacuum deposition method to obtain an organic EL device.

Comparative Example 2 An organic light emitting layer was formed under exactly the same conditions as in Example 1,
Mg was formed in exactly the same manner as the formation of the main electrode layer in Example 1.
A 100-nm-thick counter electrode (single-layer structure) made of Ag and Ag was formed by ICMS to obtain an organic EL device.

Performance Test of Organic EL Device For each of the organic EL devices produced in Examples 1 to 4 and Comparative Examples 1 and 2, a DC voltage of 10 V was applied between the lower electrode (anode) and the counter electrode (cathode). A voltage is applied to cause the organic EL element to emit light, and its initial performance (current density, luminance,
(Power conversion efficiency and uniformity of light emission). The uniformity of the light emission was measured with a luminance meter (CS-Minolta).
Judgment was made based on whether or not a non-emission point (dark spot; hereinafter abbreviated as “DS”) was observed in the visual field of 100). Further, the durability of each organic EL element was examined as follows. That is, the initial luminance is 300c
Each organic EL element emits light in a dry nitrogen atmosphere at d / m ^2, and the time required for the luminance to be reduced by half when continuously driven at the DC voltage value at this time (hereinafter referred to as “luminance half-time”) ) Is examined, and D.C. Increase in the number of S. Whether or not the area of S has increased (hereinafter referred to as “whether DS has increased”).
Was examined. Table 1 shows the results.

[0074]

[Table 1]

As is clear from the comparison of Examples 1 to 4, both the initial performance and the durability are higher when Al: Li is used than when Mg: Ag is used as the material of the counter electrode. It is easy to obtain an organic EL device. In addition, when a counter electrode containing a metal that easily reacts with an evaporation source for vacuum deposition such as Al is formed by a vacuum deposition method, it is difficult to continuously form the film, and mass productivity is low. Although decreased, as in Example 4, A
l: The thickness of the protective electrode using Li is extremely thin,
If the main electrode using l: Li is formed by an ICMS method, higher mass productivity can be obtained.

However, as is clear from the comparison between Example 1 and Comparative Example 2, when the counter electrode has a single-layer structure formed by the ICMS method, the light emitting portion is not damaged when the counter electrode is formed. Inevitably, the light-emitting characteristics (initial performance) of the organic EL element decrease. Therefore, the counter electrode is
A single layer structure formed by the CMS method is not so preferable from the viewpoint of obtaining an organic EL element having high light emission characteristics. In the second embodiment, ten D.E. S was visually recognized.

As is clear from the comparison between Example 1 and Comparative Example 1, when an opposing electrode made of only a metal that does not easily react with the evaporation source for vacuum evaporation is formed, the vacuum evaporation method is used. By forming the counter electrode, an organic EL element having high initial characteristics can be obtained with high mass productivity.
Highly durable organic EL device (long-life organic EL device)
From the viewpoint of obtaining organic E, the organic E
It is preferable to manufacture an L element.

[0078]

As described above, the organic EL of the present invention
Since the element is an organic EL element capable of obtaining high element performance under high mass productivity, according to the present invention, it is easy to provide an organic EL element with high element performance under high mass productivity. become.

Claims (6)

[Claims] A substrate, a lower electrode formed on the substrate, a light emitting portion formed on the lower electrode, and a counter electrode formed on the light emitting portion; The counter electrode is constituted by a protective electrode layer formed on the light emitting portion by a vacuum deposition method, and a main electrode layer formed on the protective electrode layer by an inductively coupled magnetron sputtering method. An organic EL device, comprising: 2. The method according to claim 1, wherein the protective electrode layer comprises a metal layer having a work function of 4 eV or less and having a thickness of 5 to 20 nm.
The organic EL device according to claim 1. 3. The organic EL device according to claim 1, wherein the main electrode layer comprises a metal layer or a conductive oxide layer having a thickness of 50 to 300 nm. 4. When forming a lower electrode on a base material, forming a light emitting portion on the lower electrode, and forming a counter electrode on the light emitting portion to obtain an organic EL device, the counter electrode is protected. After having a two-layer structure of an electrode layer and a main electrode layer, and forming the protective electrode layer on the light emitting portion by a vacuum evaporation method, the protective electrode layer is formed on the protective electrode layer by an inductively coupled magnetron sputtering method. A method for manufacturing an organic EL device, comprising forming a main electrode layer. 5. The method according to claim 4, wherein the protective electrode layer is formed of a metal layer having a work function of 4 eV or less and having a thickness of 5 to 20 nm and containing a metal as a main component. 6. A main electrode layer comprising a metal layer or a conductive oxide layer having a thickness of 50 to 300 nm.
Or the method of claim 5.