JP2000315581A - Organic electroluminescence element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate manufacture and to lower a driving voltage so as to increase light emission luminance by arranging an organic semiconductor layer between a positive electrode layer and a negative electrode layer and arranging an inorganic charge-barrier layer on each/either side of an organic light emitting layer. SOLUTION: An organic electroluminescence EL element 100 is constructed of a positive electrode layer 10, a first organic semiconductor layer 18, a first inorganic charge-barrier layer 14, an organic light emitting layer 16, a second inorganic charge- barrier layer 18, a second organic semiconductor layer 20, and a negative electrode layer 22 laminated on a board sequentially. In this way, the positive electrode layer 10 and the negative electrode layer 22 arranged via the first and second organic semiconductor layers 18, 20 are not brought into direct contact with the organic light emitting layer 16, so that positive hole/electron injection performance is improved, and consequently, the organic EL element 100 can be driven with a low voltage. Because the first and second inorganic charge-barrier layers 14, 18 giving no influence on the organic light emitting layer 16 are arranged, excellent charge confinement effect is provided and durability of the organic EL element can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence device (hereinafter, also referred to as "organic EL device"). More specifically, the present invention relates to an organic EL device suitable for use in consumer and industrial display devices (displays) or light sources of printer heads.

[0002]

2. Description of the Related Art An example of a conventional organic EL device is disclosed in, for example, US Pat. No. 5,853,905. As shown in FIG. 5, the organic EL element 40 has an anode 30 / first insulating layer 32 / organic light emitting layer 34 / second insulating layer 36 for the purpose of improving light emission efficiency and durability. /
It comprises a cathode 38. The first insulating layer 32 is provided to have an electron barrier function, and the second insulating layer 36 is provided to have a hole barrier function. The first and second insulating layers 32 and 36 are configured to have a thickness such that charges are injected from the anode 30 and the cathode 38 by a tunnel effect, respectively.

In Japanese Patent Application Laid-Open No. Hei 4-297076, as shown in FIG. 6, three organic films 52, 54 and 56 are sandwiched between a cathode layer 58 and an anode layer 50 which is a transparent electrode. An organic EL element 60 including a laminated organic film is disclosed. In the organic EL element 60, carriers are confined in the light emitting layer 56 by the first and second organic films 52 and 54, and a high luminance (luminous efficiency) is obtained at a low driving voltage.
The purpose is to get. Therefore, of the three organic films 52, 54, and 56, the first organic film 52 that is in contact with the cathode layer 58 is doped with a donor impurity, and the second organic film 54 that is in contact with the anode layer 50 is Is doped with an acceptor impurity, and the intermediate layer is configured as a light emitting layer 56. Further, the difference between the electron affinity of the first organic layer 52 doped with the donor impurity and the electron affinity of the organic light emitting layer is set to a value of 0.5 eV or more.

On the other hand, the applicant of the present invention has disclosed in
299 proposes an organic EL device which can be driven at a low voltage and can emit light of high luminance. This organic EL device is specifically composed of an anode / inorganic amorphous hole injection / transport layer / electron barrier layer / light emitting layer / cathode, or a cathode / light emitting layer / hole barrier layer / inorganic amorphous electron injection / transport layer / cathode. And an anode / inorganic amorphous hole injection / transport layer / electron barrier layer / emission layer / hole barrier layer / inorganic amorphous electron injection / transport layer / cathode.

[0005]

However, the organic EL device disclosed in U.S. Pat. No. 5,853,905 has a problem that the driving voltage is high. Further, the organic EL device disclosed in Japanese Patent Application Laid-Open No. 4-297076 has a problem in that the first and second organic films 52 and 54 are used as charge barrier layers, so that the charge confinement effect and the durability are poorly improved. Was seen. Further, in the second organic film 54, since a CN-substituted compound or a quinone compound is used as an acceptor impurity, the second organic film 54 reacts with a compound constituting the first and second organic films 52 and 54 to form a charge transfer complex or There is a tendency that exciplexes are easily formed, and therefore, there have been problems in that the emission luminance of the organic EL element is reduced and durability is poor. Also, due to the difference in electron affinity between the first organic layer and the organic light emitting layer, the junction between the organic light emitting layer and the first organic layer becomes a blocking junction, and electrons are injected from the first organic layer into the organic light emitting layer. There was a problem that the properties tended to be poor.

Further, the organic EL device proposed in Japanese Patent Application Laid-Open No. 3-77299 can be driven at a low voltage of 5 V or less.
In addition, although high-luminance light emission can be obtained, it is necessary to use a special manufacturing apparatus such as plasma CVD when forming the inorganic amorphous hole injection / transport layer or the inorganic amorphous electron injection / transport layer.

Therefore, the inventors of the present invention diligently studied the above problem, and found that by providing an organic semiconductor layer and an inorganic charge barrier layer together, a high emission luminance can be obtained even at a low driving voltage. . That is, the present invention
It is an object of the present invention to provide an organic EL element which is easy to manufacture, has a low driving voltage, and has a high light emission luminance, and a manufacturing method capable of efficiently obtaining such an organic EL element.

[0008]

According to an aspect of the organic EL device of the present invention, there is provided an organic EL device having an organic light emitting layer sandwiched between an anode layer and a cathode layer. An organic semiconductor layer is provided therebetween, and an inorganic charge barrier layer is provided on both sides or one of the sides of the organic light emitting layer. With such a configuration, the anode layer or the cathode layer does not come into direct contact with the organic light emitting layer because of the interposition of the organic semiconductor layer, and the hole and electron injection properties are improved. It will be easier.
In addition, since an inorganic charge barrier layer having high durability and not affecting the organic light emitting layer is provided in contact with the organic light emitting layer, an excellent charge confinement effect can be obtained.
The durability of the L element is improved, and the emission luminance can be increased.

In forming the organic EL device of the present invention, the specific resistance of the organic semiconductor layer is set to 1 × 10 ^-1 to 1 × 10
It is preferable that the value be in the range of ⁹ Ω · cm. With such a configuration, the hole and electron injectability are further improved, and the organic EL element can be easily driven at a low voltage.

In constituting the organic EL device of the present invention, the thickness of the organic semiconductor layer is preferably set to a value within a range from 0.1 to 500 nm. With such a configuration, the hole and electron injectability are further improved, and the organic EL element can be easily driven at a low voltage.

In constituting the organic EL device of the present invention, the organic semiconductor layer is a combination of an organic compound and an oxidizing dopant, a combination of an organic compound and a reducing dopant, or a combination of an organic compound and conductive fine particles. Is preferred. With such a configuration, the anode layer has better hole injecting property, and the cathode layer has better electron injecting property, so that the organic EL element can be easily driven at a low voltage.

In constituting the organic EL device of the present invention, the inorganic charge barrier layer provided between the anode layer and the organic light emitting layer includes silicon oxide, ZnO, GaN, InGaN,
p-type a-Si _1-x C _x (0.5 <x <1) a-Si _1-x
At least one inorganic compound selected from the group consisting of N _x (0.47 <x <0.57), or a combination of at least one compound selected from group A and at least one compound selected from group B It is preferred that Group A: Si, Ge, Sn, Pb, Ga, In, Zn, C
d, Mg chalcogenide or nitride Group B: compounds of Groups 5A to 8 of the periodic table With this configuration, a more excellent electron confinement effect is obtained and the durability of the organic EL device is further improved.

In constituting the organic EL device of the present invention, the inorganic charge barrier layer provided between the cathode layer and the organic light emitting layer comprises an alkali metal chalcogenide, an alkaline earth metal chalcogenide, and an alkali metal halogen. It is preferably at least one inorganic compound selected from the group consisting of halides and halides of alkaline earth metals.

In constituting the organic EL device of the present invention, the inorganic charge barrier layer provided between the cathode layer and the organic light emitting layer is composed of Li ₂ O, LiF, CsF, Cs ₂ O, LiC
1, BaO, SrO, MgO, MgF ₂ , SrCl ₂ , n
A-SiC, a-Si _1-x N _x (0.47 <x <0.
Preferably, the combination is a combination of at least one compound selected from at least one inorganic compound selected from the group consisting of 57). With such a configuration, a more excellent hole confinement effect can be obtained, and the durability of the organic EL element can be further improved.

In constituting the organic EL device of the present invention, the thickness of the inorganic charge barrier layer is preferably set to a value within the range of 1 to 1,000 nm. With such a configuration, a more excellent charge confinement effect is obtained, and the durability of the organic EL element is further improved.

In constituting the organic EL device of the present invention, it is preferable that the following conditions are satisfied when the electron mobility and the hole mobility in the organic light emitting layer are μ _e and _h , respectively. By configuring _{μ h> μ e> μ h} / 1000 Thus, an electron in the organic light-emitting layer, can be a hole to efficiently recombine even voltage application of the low voltage high emission Brightness can be obtained. Note that the electron mobility (μ _e ) and the hole mobility (μ _h ) of the organic light-emitting material are measured by the time of flight (TO
The measurement can be performed by applying the DC voltage of 1 × 10 ⁴ to 1 × 10 ⁶ V / cm · s using the method F).

Another embodiment of the present invention relates to a method for manufacturing an organic EL device, comprising: a step between an anode layer and an organic light-emitting layer; a step between a cathode layer and an organic light-emitting layer; And a step of forming the organic semiconductor layer and the inorganic charge barrier layer by a vapor deposition method or a sputtering method. With such an implementation, it is possible to form a film having a uniform thickness even in a large area, and furthermore, the manufacturing apparatus is simplified as a whole, and the organic EL element can be obtained at low cost.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. It should be noted that the drawings to be referred to show the size of each component so that the present invention can be understood,
It merely shows the shape and arrangement.
Therefore, the present invention is not limited only to the illustrated example. In the drawings, hatching representing a cross section may be omitted.

[First Embodiment] First, a first embodiment of the organic EL device of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of an organic EL device 100, which includes an anode layer 10, a first organic semiconductor layer 12, a first inorganic charge barrier layer 14, an organic light emitting layer 16, a second inorganic charge barrier layer 18, 2 has a structure in which two organic semiconductor layers 20 and a cathode layer 22 are sequentially laminated on a substrate (not shown). Hereinafter, the organic light emitting layer 16, the first and second organic semiconductor layers 12, 18, and the first and second inorganic charge barrier layers 14, 20 which are characteristic portions of the first embodiment will be mainly described. . Therefore, the other components, for example, the configuration and manufacturing method of the anode layer 10 and the cathode layer 22 can be of a general configuration, and will be briefly described.

(1) Organic light emitting layer (Organic light emitting substance) The organic light emitting substance used as a constituent material of the organic light emitting layer preferably has the following three functions. (A) charge injection function: a function of injecting holes from an anode or a hole injection layer when an electric field is applied, and a function of injecting electrons from a cathode layer or an electron injection layer. (B) transport function: injection (C) Light-emitting function: a function of providing a field for recombination of electrons and holes and linking them to light emission, provided that the above (a) to (c) It is not always necessary to have all of the functions together. For example, some of the materials having a hole injection / transport property larger than the electron injection / transport property are suitable as organic light emitting materials. Accordingly, in the present invention, the following general formulas (1) to
It is preferable to use an organic light emitting substance having a styryl group represented by (3) (sometimes referred to as an aromatic ring compound). The styryl group contained in the following general formulas (1) to (3) is more preferably a styryl group represented by the following general formula (4).

[0021]

Embedded image

[In the general formula (1), Ar ¹ has 6 carbon atoms.
To 40 aromatic groups, Ar ² , Ar ³ , and Ar ⁴
Is a hydrogen atom or an aromatic group having 6 to 40 carbon atoms, at least one of which is an aromatic group, and the condensation number n is an integer of 1 to 6. ]

[0023]

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[In the general formula (2), Ar ⁵ has 6 carbon atoms.
An 40 aromatic group, Ar ⁶ and Ar ^7, hydrogen atom or carbon atoms each an aromatic group having 6 to 40,
At least one of Ar ⁵ , Ar ⁶ and Ar ⁷ is substituted with a styryl group, and the condensed number m is an integer of 1 to 6. ]

[0025]

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[In the general formula (3), Ar ^{9 to} Ar ¹³ each represent an aromatic group having 6 to 40 carbon atoms, and Ar ⁸ and Ar ¹⁴ represent a hydrogen atom or an aromatic group having 6 to 40 carbon atoms. And at least one of Ar ^{8 to} Ar ¹⁴ is substituted with a styryl group, and the condensed numbers p, q, r, and s are each 0 or 1. ]

[0027]

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[In the general formula (4), Ar ¹⁵ Ar ¹⁶ and Ar ¹⁷ are each a hydrogen atom or an aromatic group having 6 to 40 carbon atoms. ]

In the organic luminescent materials represented by the general formulas (1) to (3), among the aromatic groups having 6 to 40 carbon atoms, preferred aryl groups having 5 to 40 nuclear atoms include:
Phenyl, naphthyl, anthranil, phenanthryl,
Examples include pyrenyl, chrysenyl, coronyl, biphenyl, terphenyl, pyrrolyl, furanyl, thiophenyl, benzothiophenyl, oxadiazolyl, diphenylanthranyl, indolyl, carbazolyl, pyridyl, benzoquinolyl, and the like.

The aromatic group having 6 to 40 carbon atoms may be further substituted with a substituent. Preferred examples of the substituent include an alkyl group having 1 to 6 carbon atoms (ethyl group, methyl group, i-group). -Propyl group, n-propyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, cyclopentyl group, cyclohexyl group, etc.), alkoxy group having 1 to 6 carbon atoms (ethoxy group, methoxy group, i- A propoxy group, an n-propoxy group, a s-butoxy group, a t-butoxy group, a pentoxy group, a hexyloxy group, a cyclopentoxy group, a cyclohexyloxy group, and the like;
An aryl group, an amino group substituted with an aryl group having 5 to 40 nuclear atoms, an ester group having an aryl group having 5 to 40 nuclear atoms, an ester group having an alkyl group having 1 to 6 carbon atoms, a cyano group, Examples include a nitro group and a halogen atom.

In the organic luminescent materials represented by the general formulas (1) to (3), preferred arylene groups having 5 to 40 nuclear atoms include phenylene, naphthylene, anthranylene, phenanthrylene, pyrenylene, chrysenylene, coronylene, and the like. Biphenylene, terphenylene, pyrrolylene, furanylene, thiophenylene, benzothiophenylene, oxadiazolylene, diphenylanthranylene, indolylene, carbazolylen, pyridylene, benzoquinolylene and the like can be mentioned.

In the organic light emitting layer, a benzothiazole-based, benzimidazole-based, benzoxazole-based fluorescent whitening agent, or a metal complex having a styrylbenzene-based compound or an 8-quinolinol derivative as a ligand is used in combination. Is also preferred. Further, an organic light-emitting material having a distyrylarylene skeleton such as 4,4′-bis (2,2-diphenylvinyl) biphenyl) is used as a host, and the host is provided with a strong fluorescent dye ranging from blue to red, such as a coumarin-based or host. It is also preferable to use a luminescent material doped with the same fluorescent dye as described above.

Further, from the viewpoint that excellent adhesion is obtained, electrons can be smoothly transferred to the organic light emitting layer, and mechanical strength can be improved, an electron injection layer is provided between the cathode and the organic light emitting layer. When provided, it is preferable that the constituent material of the electron injection layer and the constituent material of the organic light emitting layer partially match. That is, it is preferable to use the aromatic ring compounds represented by the general formulas (1) to (3) for the organic light emitting layer and the electron injection layer, respectively. When an electron injection layer is provided in the organic light emitting layer, it is preferable to use the same kind of aromatic ring compound. For example, in the organic light emitting layer, the same kind of aromatic ring compound is preferably used in an amount of 50% by weight or more, and more preferably 60% by weight or more.

(Forming Method) Next, a method of forming an organic light emitting layer will be described. For example, known methods such as an evaporation method, a spin coating method, a casting method, and an LB method can be applied. Further, as described above, the electron injection layer and the organic light emitting layer are preferably formed by the same method. For example, when the electron injection layer is formed by a vapor deposition method, the organic light emitting layer is also formed by a vapor deposition method. It is preferable to form a film.

The organic light-emitting layer is a thin film formed by deposition from a material compound in a gaseous phase or a film formed by solidification from a material compound in a solution state or a liquid state. It is preferable that Usually, this molecular deposition film is a thin film (molecule accumulation film) formed by the LB method.
Can be classified according to the difference between the aggregated structure and the higher-order structure and the functional difference resulting therefrom. Furthermore, the organic light-emitting layer can also be formed by dissolving a binder such as a resin and an organic light-emitting material in a solvent to form a solution, and then thinning the solution by spin coating or the like.

(Thickness of Organic Light-Emitting Layer) The thickness of the organic light-emitting layer thus formed is not particularly limited and can be appropriately selected depending on the situation.
It is preferably a value within the range of m. The reason for this is that when the thickness of the organic light emitting layer is less than 5 nm, the light emission luminance may decrease. On the other hand, when the thickness of the organic light emitting layer exceeds 5 μm, the value of the applied voltage tends to increase. There is. Therefore, the thickness of the organic light emitting layer is set to 10 nm to 3 μm.
Is more preferably in the range of 20 nm to 1
More preferably, the value is in the range of μm.

(2) Organic Semiconductor Layer The first and second organic semiconductor layers are provided to facilitate hole and electron injection, respectively. That is, even if the organic light emitting layer, which is an insulating layer, is directly in contact with the anode layer and the cathode layer, the energy barrier for hole injection and the energy barrier for electron injection are large, respectively.
It is difficult to inject holes and electrons, respectively. On the other hand, by providing the first and second organic semiconductor layers, the energy barrier against hole injection and electron injection can be reduced. Therefore, the injection of holes and electrons is facilitated, and the driving voltage is reduced, for example, 10
V or less. In addition, with such an organic semiconductor layer, without using a plasma CVD apparatus or the like,
A film can be easily formed using a vacuum evaporation apparatus or a thermal CVD apparatus having a relatively simple structure. Therefore, by using an organic semiconductor layer, an advantage in manufacturing can be obtained as compared with the case where an inorganic semiconductor layer is provided.

Constituent Materials The organic semiconductor layer is preferably a combination of an organic compound and an oxidizing dopant, a combination of an organic compound and a reducing dopant, or a combination of an organic compound and conductive fine particles.

Specifically, a preferred combination of the organic compound and the conductive fine particles is selected from organic compounds usually used in organic EL devices, for example, polyvinyl carbazole, polyaniline, polystyrene, amine derivatives, porphyrin, phthalocyanines and the like. A material in which conductive metal particles and conductive inorganic particles are mixed and dispersed is exemplified.
In addition, examples of the kind of the conductive fine particles include one kind alone or a combination of two or more kinds such as gold, silver, copper, nickel, solder, aluminum, indium oxide, tin oxide, and zinc oxide. Further, the average particle diameter of the conductive metal particles is preferably set to a value in the range of 0.001 to 1 μm. Further, the amount of the conductive fine particles to be added is controlled by the amount of the organic compound 10.
It is preferable to set the value within the range of 0.1 to 50 parts by weight with respect to 0 parts by weight.

As the combination of the organic compound and the oxidizing dopant, organic compounds such as polyvinyl carbazole, polyaniline, polycarbonate containing an amine in the main chain, polyether, polysulfone, porphyrin, copper phthalocyanine, and the like, quinone derivatives, halogenated halides, etc. Examples include combinations of oxidizing dopants such as metals, Lewis acids, organic acids, metal halide salts, Lewis salts, fullerenes, and organic acid salts. Therefore, more specific combinations of organic compounds and oxidizing dopants include polyvinyl carbazole and antimony chloride, polyaniline and antimony chloride, amine derivatives and C60, NPD and thioketone, porphyrin and TCNQ, copper phthalocyanine and TCN
E, amine oligomers and DDQ, or amine dendrimers and DDQ, and the like.

When an organic compound is combined with an oxidizing dopant, the ratio of the organic compound to the organic compound is 1:
It is preferable to set the value in the range of 1 to 20: 1 (molar ratio). If the addition ratio of the organic compound and the oxidizing dopant is out of these ranges, the emission luminance of the organic EL element may be reduced or the life may be shortened. Therefore, the addition ratio of the organic compound to the oxidizing dopant is more preferably set to a value within the range of 1: 1 to 10: 1 (molar ratio), and is set to a value within the range of 1: 1 to 5: 1. Is more preferable.

As the combination of the organic compound and the reducing dopant, Alq, DPAVBi or P
Organic compounds such as BD include alkali metals, alkaline earth metals, rare earth metals, alkali metal oxides, alkali metal halides, alkaline earth metal oxides, alkaline earth metal halides, rare earth metal It is preferable to combine at least one reducing dopant selected from the group consisting of oxides and halides of rare earth metals. Further, the addition amount of the reducing dopant is
The same value as the addition ratio of the oxidizing dopant to the organic compound can be used. The organic compound preferably has an electron transporting property, and the alkali metal is Cs,
And Li are preferred.

The combination of the organic compound and the oxidizing dopant, the combination of the organic compound and the reducing dopant, or the combination of the organic compound and the conductive fine particles described above are suitably used for the first and second organic semiconductor layers, respectively. be able to. However, in the first organic semiconductor layer, a combination of an organic compound and an oxidizing dopant, or a combination of an organic compound and conductive fine particles is more preferable because the hole injection property becomes better. Further, in the second organic semiconductor layer, a combination of an organic compound and a reducing dopant, or a combination of an organic compound and conductive fine particles is more preferable because the electron injecting property becomes better.

Specific Resistance The specific resistance of the first and second organic semiconductor layers is 1 × 10 ⁻¹ to
It is preferable that the value be in the range of 1 × 10 ⁹ Ω · cm. This is because if the specific resistance is less than 1 × 10 ⁻¹ Ω · cm, a short circuit may occur between adjacent organic EL elements, while the specific resistance is 1 × 10 ⁹ Ω · c.
If m exceeds m, hole and electron injectability may decrease. Therefore, the specific resistance of the first and second organic semiconductor layers is more preferably set to a value in the range of 1 × 10 ¹ to 1 × 10 ⁸ Ω · cm, and 1 × 10 ² to 1 ×.
More preferably, the value is in the range of 10 ⁷ Ω · cm.

Thickness The thickness of the first and second organic semiconductor layers is 1 to 1,000.
Preferably, the value is in the range of nm. The reason for this is
When the thickness is less than 1 nm, the mechanical strength decreases,
This is because the hole and electron injectability may decrease. On the other hand, if the thickness exceeds 1,000 nm, the improvement of the hole and electron injectability may be reduced, or the film formation time may be significantly increased. Therefore, the thickness of the first and second organic semiconductor layers is 10 to 2
More preferably, the value is in the range of 00 nm.

(3) Inorganic Charge Barrier Layer The first and second inorganic charge barrier layers are provided to facilitate hole and electron confinement and injection, respectively. That is, the first inorganic charge barrier layer is an electron barrier layer, and is provided on the anode side in contact with the organic light emitting layer. Accordingly, the first inorganic charge barrier layer can energetically shield electrons that are going to pass through the organic light emitting layer, so that the electrons can be effectively confined in the organic light emitting layer. The second inorganic charge barrier layer is a hole barrier layer, and is provided on the cathode side in contact with the organic light emitting layer. Therefore, the holes that are going to pass through the organic light emitting layer are energetically blocked by the second inorganic charge barrier layer, and the holes can be effectively confined in the organic light emitting layer. Therefore, the electrons and holes confined in the organic light emitting layer can be efficiently recombined by the first and second inorganic charge barrier layers, and the light emission efficiency can be increased. Note that even if the first and second inorganic charge barrier layers are provided, the first inorganic charge barrier layer rarely acts as a barrier to holes transported from the anode layer in terms of energy. The second inorganic charge barrier layer rarely acts as a barrier for electrons transported from the cathode layer.

Constituent Materials (First Inorganic Charge Barrier Layer) The first inorganic charge barrier layer provided between the anode layer and the organic light emitting layer is made of silicon oxide, Zn
O, GaN, InGaN, p-type a-Si _1-x C _x (0.
5 <x <1), at least one inorganic compound selected from the group consisting of a-Si _1-x N _x (0.4 <x <1), or provided between the cathode layer and the organic light emitting layer Preferably, the second inorganic charge barrier layer is a combination of at least one compound selected from Group A and at least one compound selected from Group B. Group A: Si, Ge, Sn, Pb, Ga, In, Zn, C
d, Mg chalcogenide or nitride Group B: preferably a compound of Groups 5A to 8 of the periodic table. By using such an inorganic compound, a more excellent electron confinement effect is obtained, and the durability of the organic EL element is further improved. Moreover, such an inorganic compound does not react with the constituent material of the organic light emitting layer, and the range of use of the constituent material of the organic light emitting layer is not limited.

(Second Inorganic Charge Barrier Layer) By using such a combination of inorganic compounds, a more excellent hole confinement effect is obtained, and the durability of the organic EL device is further improved.

The second inorganic charge barrier layer is made of Li ₂ O,
LiF, CsF, Cs ₂ O, LiCl, BaO, Sr
O, MgO, MgF ₂ , SrCl ₂ , n-type a-SiC,
It is also preferable to comprise at least one inorganic compound selected from the group consisting of n-type a-Si _1-x N _x (0.1 <x <0.7). By using such an inorganic compound, a better hole confinement effect can be obtained,
Further, the durability of the organic EL element is further improved. Moreover,
With such an inorganic compound, it does not react with the constituent material of the organic light emitting layer, and the use range of the constituent material of the organic light emitting layer is not limited.

Thickness The thickness of the first and second inorganic charge barrier layers is from 1 to 1,000.
It is preferable to set the value in the range of 0 nm. The reason for this is that if the thickness is less than 1 nm, the mechanical strength may decrease, or the confinement of holes and electrons may decrease. On the other hand, if the thickness exceeds 1,000 nm,
This is because the improvement of the hole and electron injectability may be reduced or the film formation time may be significantly increased. Therefore, the thickness of the first and second inorganic charge barrier layers is set to 1
More preferably, the value is in the range of 0 to 200 nm.

(4) Electrode (Anode Layer) As the anode layer, it is preferable to use a metal, an alloy, an electrically conductive compound or a mixture thereof having a large work function (for example, 4.0 eV or more). Specifically, one kind of indium tin oxide (ITO), indium zinc oxide, tin, zinc oxide, gold, platinum, palladium and the like can be used alone or in combination of two or more kinds.

The thickness of the anode layer is not particularly limited, but is preferably in the range of 10 to 1000 nm, and more preferably in the range of 10 to 200 nm. Further, the anode layer is substantially transparent, and more specifically, has a light transmittance of 1 so that light emitted from the organic light emitting layer can be effectively extracted to the outside.
The value is preferably 0% or more.

(Cathode Layer) On the other hand, for the cathode layer, it is preferable to use a metal, an alloy, an electrically conductive compound or a mixture thereof having a small work function (for example, less than 4.0 eV). Specifically, one kind of magnesium, aluminum, indium, lithium, sodium, silver, etc. is used alone,
Alternatively, two or more kinds can be used in combination.
The thickness of the cathode layer is not particularly limited, either.
Preferably, the value is in the range of 0 to 1000 nm.
More preferably, the value is in the range of 0 to 200 nm.

[Second Embodiment] As shown in FIG. 2, an organic EL device 102 according to a second embodiment has an anode layer 10, a first organic semiconductor layer 12, a first inorganic charge barrier layer 14, , The organic light emitting layer 16, the electron injection layer 24, and the cathode layer 22 are sequentially laminated on a substrate (not shown). The organic EL according to the second embodiment
The element 102 includes the electron injecting layer 24 and an electron transporting compound and a reducing dopant. That is, in the second embodiment, the hole injecting property is changed by the first organic semiconductor layer 12 and the electron injecting property is changed by the electron injecting layer 2.
4 and the first inorganic charge barrier layer 1
4 gives an electron barrier property. Hereinafter, the electron injection layer 24, which is a characteristic portion of the second embodiment, will be mainly described, and the other components, for example, the configuration and manufacturing method of the anode layer 10 and the cathode layer 22 are the same as those of the first embodiment. The configuration can be the same as that of the embodiment.

(1) Electron Injecting Region (Electron-Transporting Compound) As the electron-transporting compound, any compound having a function of transmitting electrons injected from a cathode to an organic luminescent medium should be widely used. Can be.
Specifically, for example, an aromatic ring compound composed of an aromatic ring containing no nitrogen atom (sometimes simply referred to as a non-nitrogen heterocyclic compound) or an organic compound containing a nitrogen-containing heterocyclic compound (simply, Nitrogen-containing heterocyclic compound may be referred to.).

Non-Nitrogen Heterocyclic Compound The non-nitrogen heterocyclic compound is a compound containing an aromatic ring composed of carbon (C) and hydrogen (H), or a compound containing carbon (C), hydrogen (H) and oxygen (O ) Is defined as a compound containing an aromatic ring. However, a nitrogen atom may be contained in a molecule other than the aromatic ring, and it is rather preferable that aromatic rings not containing a nitrogen atom are connected to each other by, for example, a nitrogen atom. Further, the compound of the aromatic ring composed of carbon and hydrogen and the compound of the aromatic ring composed of carbon, hydrogen and oxygen may be used alone or in combination.

As described above, by using the non-nitrogen heterocyclic compound in combination with the reducing dopant described below, excellent electron injecting properties can be obtained, and the reaction with the constituent materials in the adjacent light emitting region can be suppressed. . That is, the non-nitrogen heterocyclic compound is an aromatic ring composed of carbon and hydrogen,
Or, it is composed of an aromatic ring composed of carbon, hydrogen and oxygen, and is composed of a nitrogen-containing aromatic ring or an electro withdrawing group (for example,-
It does not contain a nitrogen-containing group such as a CN group, a —NO ₂ group, an amide group, and an imide group. Therefore, generation of a charge transfer complex or exciplex having low luminous efficiency at the interface between the electron injection region and the light emitting region can be efficiently suppressed.

Preferred non-nitrogen heterocyclic compounds include anthracene, fluorene, perylene, pyrene, phenanthrene, chrysene, tetracene, rubrene, terphenylene, quarterphenylene, sexiphenylene, triphenylene, picene, coronel, diphenylanthracene, benz [a] anthracene And an aromatic ring compound containing at least one aromatic ring selected from the group consisting of binaphthalene. It is more preferable that the non-nitrogen heterocyclic compound has a styryl group-substituted aromatic ring, a distyryl group-substituted aromatic ring, or a tristyryl group-substituted aromatic ring. Thus, styryl group substitution (including distyryl group substitution and tristyryl group substitution).
Hereinafter, the same applies. ), The light emission luminance and the life of the organic EL element can be further improved. Examples of the aromatic ring compound containing a styryl group-substituted group include, for example, the same aromatic ring compounds as the aromatic ring compounds represented by the general formulas (1) to (3) used in the organic light emitting medium. Compounds.

Nitrogen-Containing Heterocyclic Compound Examples of the electron transporting compound include a nitrogen-containing heterocyclic compound. Even when the nitrogen-containing heterocyclic compound is used as described above, by using a reducing dopant having a work function of 2.9 eV or less among the reducing dopants described below, it is possible to react with the organic light emitting medium material. Is efficiently suppressed, and a high light emission luminance can be obtained.

Such a nitrogen-containing heterocyclic compound is defined as a compound having a heterocyclic ring having a nitrogen atom, and specific examples include a nitrogen-containing complex and a nitrogen-containing ring compound. Preferred examples of the nitrogen-containing complex include a metal complex having an 8-quinolinol derivative as a ligand, a phthalocyanine derivative, and a metal phthalocyanine. Preferred examples of the nitrogen-containing ring compound include oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, quinoxaline derivatives, and quinoline derivatives. Further, as the nitrogen-containing heterocyclic compound, it is also preferable to use a heterocyclic tetracarboxylic anhydride such as an anthrone derivative, a fluorenilimethane derivative, carbodiimide, or naphthaleneperylene.

(Reducing Dopant) The electron injection region in the second embodiment is characterized in that it contains a reducing dopant together with an electron transporting compound.

Kind Reducing dopant is defined as a substance that can reduce an aromatic ring compound when it is oxidized. Therefore, the type of the reducing dopant is not particularly limited as long as it has a certain reducing property, but it is preferable to use the same type as the reducing dopant used in the organic semiconductor layer.

More specifically, preferable alkali metals include, for example, Li (lithium, work function: 2.93 e).
V), Na (sodium, work function: 2.36 eV),
K (potassium, work function: 2.3 eV), Rb (rubidium, work function: 2.16 eV) and Cs (cesium, work function: 1.95 eV). The values of the work functions in parentheses are described in Chemical Handbook (Basic Edition II, p. 49).
3, edited by The Chemical Society of Japan), and so forth. Preferred alkaline earth metals include, for example, Ca (calcium, work function: 2.9 eV), M
g (magnesium, work function: 3.66 eV), Ba
(Barium, work function: 2.52 eV), and Sr
(Strontium, work function: 2.0 to 2.5 eV). The value of the work function of strontium is
Physics of Semiconductor Device (NY Wyllow, 1969, P366). Preferred rare earth metals include, for example, Yb (ytterbium, work function: 2.6e).
V), Eu (Eurobium, work function: 2.5 eV),
Gd (gadnium, work function: 3.1 eV) and En
(Erbium, work function: 2.5 eV).

Preferred alkali metal oxides include, for example, Li ₂ O, LiO and NaO. Preferred alkaline earth metal oxides include:
For example, CaO, BaO, SrO, BeO and MgO
Is raised. Preferred alkali metal halides include, for example, fluorides such as LiF, NaF and KF, as well as LiCl, KCl and NaC.
l. Preferred alkaline earth metal halides include, for example, CaF ₂ , BaF ₂ , Sr
Examples include fluorides such as F ₂ , MgF ₂ and BeF ₂ , and halides other than fluorides. Preferred rare earth halides include, for example, LaF ₃ , YbF ₃ , and Eu.
Fluorides such as F _3, and the like.

As a preferable reducing dopant,
An aromatic compound coordinated with an alkali metal is also included. The aromatic compound coordinated with the alkali metal is represented by, for example, the following general formula (5). A ⁺ Ar ^20- (5) where A in the general formula (5) represents an alkali metal.
Ar ²⁰ is an aromatic compound having 10 to 40 carbon atoms. Examples of the aromatic compound represented by the formula (5) include anthracene, naphthalene, diphenylanthracene, terphenyl, quarterphenyl, kinkphenyl, sexiphenyl and derivatives thereof.

Addition Amount The amount of the reducing dopant added in the electron injection region may be set to a value within the range of 0.01 to 50% by weight when the entire material constituting the electron injection region is 100% by weight. preferable. The amount of the reducing dopant added is 0.01% by weight.
If it is less than, the emission luminance of the organic EL element is reduced,
Life tends to be shorter. On the other hand, when the addition amount of the reducing dopant exceeds 50% by weight, on the contrary, the emission luminance tends to decrease and the life tends to be shortened. Therefore, it is more preferable to set the amount of the reducing dopant to a value in the range of 0.2 to 20% by weight from the viewpoint that the balance between the emission luminance and the life becomes better.

Further, with respect to the amount of the reducing dopant to be added, it is preferable that the addition ratio between the aromatic ring compound and the reducing dopant is in a range of 1:20 to 20: 1 (molar ratio). When the addition ratio of the electron transporting compound and the reducing dopant is out of these ranges, the emission luminance of the organic EL device tends to decrease and the life tends to be shortened. Therefore, the addition ratio of the aromatic ring compound to the reducing dopant is more preferably set to a value within the range of 1:10 to 10: 1 (molar ratio), and a value within the range of 1: 5 to 5: 1. More preferably,

(Electron Affinity) The electron affinity in the electron injection region in the second embodiment is preferably set to a value within the range of 1.8 to 3.6 eV. The value of electron affinity is 1.8
If it is less than eV, the electron injecting property tends to decrease, leading to an increase in driving voltage and a decrease in luminous efficiency. On the other hand, when the value of electron affinity exceeds 3.6 eV, a complex having low luminous efficiency is generated. Thus, the occurrence of blocking junction can be suppressed efficiently. Therefore, the electron affinity in the electron injection region is more preferably set to a value within the range of 1.9 to 3.0 eV, and even more preferably set to a value within the range of 2.0 to 2.5 eV. Further, the difference between the electron affinity between the electron injection region and the organic luminescent medium is preferably set to 1.2 eV or less, more preferably 0.5 eV or less. The smaller the difference in electron affinity, the easier the electron injection from the electron injection region to the organic luminescent medium,
An organic EL element capable of high-speed response can be obtained.

(Glass Transition Point) The glass transition point (glass transition temperature) of the electron injection region in the second embodiment is
The value is preferably 100 ° C. or more, more preferably a value in the range of 105 to 200 ° C.
By limiting the glass transition point in the electron injection region in this way, the heat-resistant temperature of the organic EL element 100 can be easily set to 85 ° C. or higher. Therefore, even when a current is injected from the current injection layer into the organic luminescent medium during light emission and Joule heat is generated, the tendency of the electron injection region to be destroyed in a short time is reduced, and the life of the organic EL element is extended. be able to. The glass transition point of the electron injection region is determined by the differential scanning calorimeter (DS) for the components constituting the electron injection region.
C) can be determined as a specific heat change point from a specific heat change curve obtained when heating is performed in a nitrogen stream at a rate of temperature rise of 10 ° C./min. This point is the same in other embodiments and examples.

(Energy Gap) The energy gap (band gap energy) of the electron injection region in the second embodiment is preferably set to a value of 2.7 eV or more, and more preferably to a value of 3.0 eV or more. . As described above, when the value of the energy gap is set to be larger than a predetermined value, for example, 2.7 eV or more, it is less likely that holes move to the electron injection region beyond the organic light emitting medium. Therefore, the efficiency of recombination of holes and electrons is improved, the light emission luminance of the organic EL element is increased, and light emission in the electron injection region itself can be avoided.

(Structure of Electron Injection Area) The structure of the electron injection area in the second embodiment is not particularly limited and is not limited to a single-layer structure. For example, a two-layer structure or a three-layer structure may be used. May be. Further, the thickness of the electron injection region is not particularly limited.
Preferably, the value is in the range of nm to 1 μm,
More preferably, the value is in the range of 0 nm.

(Method for Forming Electron Injection Area) Next, a method for forming the electron injection area will be described. The method for forming the electron injection region is not particularly limited as long as it can be formed as a thin film layer having a uniform thickness. For example, a known method such as an evaporation method, a spin coating method, a casting method, and an LB method may be used. Can be applied. Note that it is preferable that the aromatic ring compound containing no nitrogen atom and the reducing dopant be co-evaporated, but this vapor deposition method will be described in detail in the third embodiment.

It is preferable that the electron injection region and the method of forming the organic luminescent medium are made to coincide with each other. For example, when the organic light emitting medium is formed by a vapor deposition method, it is preferable that the electron injection region is also formed by a vapor deposition method. When the film is formed by the same method as described above, the electron injection region and the organic light emitting medium can be formed continuously, which is advantageous in simplifying equipment and shortening the settlement time. Further, since the chances of oxidizing the electron injection region and the organic light emitting medium are reduced, the light emission luminance of the organic EL element can be improved.

[Third Embodiment] Next, FIG. 3 and FIG.
A third embodiment of the present invention will be described with reference to FIG. In the third embodiment, even when the organic light emitting layer or the like has a large area, the composition ratio of the constituent materials is made uniform, the variation in the driving voltage of the organic EL element is reduced, and the life can be made uniform. An object of the present invention is to provide a method for manufacturing a first organic EL element capable of saving space. That is, a plurality of evaporation sources 21 arranged opposite to the substrate 203 using the vacuum evaporation apparatus 201 as shown in FIGS.
This is a method for evaporating a thin film layer for an organic EL element by simultaneously evaporating different evaporation materials from 2A to 212F, wherein a rotation axis 213A for rotating the substrate 203 is set on a substrate 203, Sources 212A-212F
Are disposed at positions away from the rotation axis 213A of the substrate 203, and the evaporation is performed while rotating the substrate 203.

Here, the vacuum evaporation apparatus 201 shown in FIGS. 3 and 4 includes a vacuum chamber 210, a substrate holder 211 for fixing the substrate 203, which is installed in the upper portion of the vacuum chamber 210, It comprises a plurality (six) of evaporation sources 212A to 212F, which are arranged below the holder 211 and are opposed to each other, for filling an evaporation material. The inside of the vacuum chamber 210 can be maintained at a predetermined reduced pressure state by an exhaust means (not shown). In addition,
Although the number of vapor deposition sources is shown in the drawing as six, the number is not limited thereto, and may be five or less, or seven or more.

The substrate holder 211 has a holding portion 212 for supporting the peripheral portion of the substrate 203, and is configured to horizontally hold the substrate 203 in the vacuum chamber 210. At the center of the upper surface of the substrate holder 211, a rotating shaft 213 for rotating (rotating) the substrate 203 is provided upright in the vertical direction. The rotating shaft 213 is connected to a motor 214 serving as a rotation disturbance unit.
4 rotates the substrate 203 held by the substrate holder 211 together with the substrate holder 211 into the rotating shaft 2.
13 rotates around the center of rotation. That is, at the center of the substrate 203, the rotation axis 213A of the rotation shaft 213 is set in the vertical direction.

Next, the organic light-emitting layer 16 and the electron injection layer 14 are
A method for forming a film on the substrate 203 will be specifically described. First, a planar square substrate 20 as shown in FIG.
The substrate 203 is prepared, and the substrate 203 is locked on the holding portion 212 of the substrate holder 211 to be in a horizontal state. In this regard, the fact that the substrate 203 shown in FIG. 2 is held in a horizontal state indicates this.

Here, on the virtual circle 221, the evaporation source 212
A first organic semiconductor layer material, a first inorganic charge barrier layer material, an organic light emitting layer material, a second organic semiconductor layer material, a second inorganic charge barrier layer material, and a cathode material. After each filling, the inside of the vacuum chamber 210 is evacuated to a predetermined degree of vacuum, for example, 1.0 × 10 ⁻⁴ Torr by the exhaust means. In forming the organic light emitting layer 16 and the like, it is also preferable to deposit two or more types of electron transporting compounds, or to uniformly deposit a combination of a hole transporting compound and an electron transporting compound, It is also preferable that the concentration of the electron transporting compound is higher with respect to the hole transporting compound as it is closer to the cathode.

Next, each of the vapor deposition sources 212 is heated to vapor-deposit each forming material, and the motor 214 is rotated and disturbed to rotate the substrate 203 along the rotation axis 213A at a predetermined speed, for example, 1 to 100 rpm. . In this way, the organic light emitting layer 16 and the like are formed by simultaneously depositing a plurality of deposition materials while rotating the substrate 203.

As shown in FIG. 4, for example, the evaporation sources 212 B and 212 C
Since it is provided at a position shifted by a predetermined distance M in the horizontal direction from 3A, the angle of incidence of the two kinds of deposition materials on the substrate 203 can be changed regularly by the rotation of the substrate 203. Therefore, the deposition material can be uniformly attached to the substrate 203, and the composition ratio of the deposition material is uniform in the film surface of the electron injection layer 14, for example, the concentration unevenness is ± 10% (in terms of mol). A certain thin film layer can be reliably formed. Further, by performing the vapor deposition as described above, the substrate 203 does not need to revolve, so that space and equipment are not required, and the film can be formed economically with a minimum space. Revolving the substrate means rotating around a rotation axis other than the substrate, and requires a larger space than when rotating.

In carrying out the manufacturing method according to the third embodiment, the shape of the substrate 203 is not particularly limited.
For example, as shown in FIG. 3, when the substrate 203 is in the shape of a short flat plate, a plurality of evaporation sources 212 are formed along the circumference of the virtual circle 221 about the rotation axis 213A of the substrate 203.
A to 212F are provided, and when the radius of the virtual circle 221 is M and the length of one side of the substrate 203 is L, M> (1/2)
It is desirable to satisfy × L. When the lengths of the sides of the substrate 203 are not the same but different, the length of the longest side is set to L. With this configuration, the substrate 203 can be supplied from the plurality of evaporation sources 212A to 212F.
Since the angles of incidence of the vapor deposition material with respect to can be made the same, the composition ratio of the vapor deposition material can be more easily controlled. In addition, with this configuration, the evaporating material is evaporated at a constant incident angle with respect to the substrate 203, so that the evaporating material does not enter vertically and the uniformity of the composition ratio in the film plane is further improved. be able to.

In carrying out the manufacturing method according to the third embodiment, as shown in FIG.
To 212F are arranged on the circumference of a virtual circle 221 centered on the rotation axis 213A of the substrate 203, and the plurality of evaporation sources 21
When the number (number) of the arrangements 2A to 212F is n, it is preferable that the evaporation sources 212A to 212F are arranged at an angle of 360 ° / n from the center of the virtual circle 221. For example, when six evaporation sources 212 are provided, the virtual circle 22
It is preferable to arrange them at an angle of 60 ° from the center of one. With this arrangement, a plurality of deposition materials can be sequentially formed on each portion of the substrate 203, so that thin film layers having composition ratios that are regularly different in the thickness direction of the film can be easily formed. can do.

[0083]

EXAMPLES Example 1 (1) Preparation for Manufacturing Organic EL Device In manufacturing the organic EL device of Example 1, first, a transparent glass substrate having a thickness of 1.1 mm, a length of 200 mm, and a width of 200 mm was used. Then, a transparent electrode film of ITO was formed as an anode layer. Next, the substrate is subjected to ultrasonic cleaning with isopropyl alcohol, and further dried in an N ₂ (nitrogen gas) atmosphere.
Washed for minutes. Hereinafter, the glass substrate and the anode layer are collectively referred to as a substrate. Next, the cleaned substrate is placed in a vacuum deposition apparatus.
(Japan Vacuum Engineering Co., Ltd.), it is attached to the substrate holder of the vacuum chamber, and the material for the organic semiconductor layer (copper phthalocyanine and DDQ) and the material for the inorganic charge barrier layer (Si
O ₂ ), organic light emitting layers (DPVTP and DPAVB)
i), a material for an electron injection layer (Alq), and a material for a cathode layer (aluminum and lithium) were respectively filled in the respective evaporation sources. The structural formulas of DPVTP, DDQ, and DPAVBi are represented by the following formulas (7), (8), and (9).
Are shown below.

[0084]

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[0085]

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[0086]

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(2) Manufacture of Organic EL Element Next, the pressure inside the vacuum chamber was reduced to a degree of vacuum of 1 × 10 ⁻⁶ Torr, and the first 600 μm thick layer was formed on the anode layer formed on the substrate. Organic semiconductor layer, a first inorganic charge barrier layer having a thickness of 50 °, an organic light emitting layer having a thickness of 400 °, and a thickness of 200
An electron injection layer of Å and a cathode layer of 2,000 Å thickness were sequentially laminated to obtain an organic EL device. When the first organic semiconductor layer is formed, copper phthalocyanine and DDQ are simultaneously deposited according to the method described in the third embodiment, the deposition rate of copper phthalocyanine is set to 50 ° / sec, and the deposition rate of DDQ is set to 1Å / sec. When forming the first inorganic charge barrier layer, the deposition rate of SiO _x (1 <x <2) was set to 1 ° / sec. Also, when forming the organic light emitting layer, DPVTP and DPAVBi are simultaneously deposited,
The VTP deposition rate was 50 ° / sec, and the DPAVBi deposition rate was 1 ° / sec. In forming the electron injection layer, the deposition rate of Alq was set to 2Å / sec. further,
Also when forming the cathode layer, aluminum and lithium are co-deposited, and the deposition rate of aluminum is 10 ° /
Seconds and the deposition rate of lithium was 0.1 ° / sec. In addition, an organic EL element was manufactured without breaking the vacuum state even once between the formation of the organic light emitting layer and the formation of the cathode layer.

(3) Evaluation of organic EL device The cathode layer in the obtained organic EL device was minus (-).
Electrode and anode layer as plus (+) electrode, 8
V DC voltage was applied. The current density at this time is 1.8
mA / cm ² , and the emission luminance at that time was 92 cd /
m ² , and the emission color was blue. When the obtained organic EL device was driven at a constant current of 10 mA / cm ² , no leakage current was observed even after 1000 hours.

Example 2 In Example 2, instead of copper phthalocyanine and DDQ in the organic semiconductor layer of Example 1, TPDP represented by the following formula (10) (formula (1)
In 0), m and n are each an integer of 1 to 10. ) And iron chloride (weight ratio: 100: 5), an organic EL device was prepared in the same manner as in Example 1, and a light emitting state was evaluated by applying a DC voltage of 8 V. As a result, the current density was 1.6 mA / cm ² , the emission luminance at that time was 82 cd / m ² , and the emission color was blue. When the obtained organic EL device was driven at a constant current of 10 mA / cm ² , no leakage current was observed even after 1000 hours.

[0090]

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Example 3 In Example 3, in place of copper phthalocyanine and TCNQ in the organic semiconductor layer of Example 1, PMMA as a binder and antimony-doped tin oxide (weight ratio 1: 1) as conductive fine particles were used. Except for using, an organic EL device was produced in the same manner as in Example 1,
The light emitting state was evaluated by applying a DC voltage of 8 V. As a result, the current density was 1.5 mA / cm ² , the emission luminance at that time was 76 cd / m ² , and the emission color was blue. When the obtained organic EL device was driven at a constant current of 10 mA / cm ² , no leakage current was observed even after 1000 hours.

[Embodiment 4] In Embodiment 4, instead of Alq in the electron injection layer of Embodiment 1, Li ₂ O was added at 10 ° C.
An organic EL device was prepared in the same manner as in Example 1, except that phthalocyanine and Li were simultaneously deposited at a deposition rate of 20 ° / cm ^{2 to} a thickness of 200 °. The light emitting state was evaluated by applying a DC voltage. As a result, the current density is 1.7 mA / cm ² ,
At that time, the light emission luminance was 83 cd / m ² , and the light emission color was blue. Further, the obtained organic EL device was 10 mA.
/ Cm ² , no leakage current was observed even after 1000 hours.

Comparative Example 1 In Comparative Example 1, an organic EL device was manufactured in the same manner as in Example 1 except that the inorganic charge barrier layer in Example 1 was not provided, and light was emitted by applying a DC voltage of 8 V. The condition was evaluated. As a result, the current density was 2.2 m
A / cm ² , and the emission luminance at that time was 41 cd / m ^2.
And the emission color was blue. In addition, the obtained organic E
When the L element was driven at a constant current of 10 mA / cm ² ,
Even after lapse of 000 hours, a leak current is generated and the voltage is 11 V
Up.

[Comparative Example 2] In Comparative Example 2, the organic E layer was prepared in the same manner as in Example 1 except that the DDQ used together with copper phthalocyanine was not used and the organic semiconductor layer was not used.
An L element was manufactured, and a light emitting state was evaluated by applying a DC voltage of 8 V. As a result, the current density was significantly reduced to 0.7 mA / cm ^2, and the emission luminance at that time was 30 cd / m ^2.
And the emission color was blue. In addition, the obtained organic E
When the L element was driven at a constant current of 10 mA / cm ² ,
No leakage current was observed even after a lapse of 000 hours.

[0095]

As described above in detail, according to the organic EL device of the present invention, the organic light-emitting substance near the interface with the anode layer is oxidized using an oxidizing dopant or the like, so that a low voltage can be obtained. In driving (for example, a DC voltage of 7 V or less), the luminous efficiency is improved (for example, a light emission luminance of 30 cd).
/ M ² or more).

Further, according to the method of manufacturing an organic EL device of the present invention, the method includes a step of oxidizing an organic luminescent material near the interface with the anode layer, thereby enabling low-voltage driving (for example, a DC voltage of 7 V or less). , High luminous efficiency (for example,
An organic EL device having an emission luminance of 30 cd / m ² or more can be efficiently provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an organic EL device according to a first embodiment.

FIG. 2 is a cross-sectional view of an organic EL device according to a second embodiment.

FIG. 3 is a perspective view of a vacuum deposition apparatus according to a third embodiment.

FIG. 4 is a sectional view of a vacuum evaporation apparatus according to a third embodiment.

FIG. 5 is a sectional view of a conventional organic EL element (No. 1).

FIG. 6 is a sectional view of a conventional organic EL element (part 2).

[Explanation of symbols]

 Reference Signs List 10 anode layer 12 first organic semiconductor layer 14 first inorganic charge barrier layer 16 organic light emitting layer 18 second inorganic charge barrier layer 20 second organic semiconductor layer 22 cathode layer 24 electron injection layer 100, 102 organic EL device 201 Vacuum evaporation apparatus 203 Substrate 210 Vacuum tank 211 Substrate holder 212 Holder 212A to 212F Evaporation source 213 Rotation axis 213A Rotation axis 214 Motor 221 Virtual circle

Claims (10)

[Claims] 1. An organic electroluminescence device having an organic light emitting layer sandwiched between an anode layer and a cathode layer, wherein an organic semiconductor layer is further provided between the anode layer and the cathode layer. An organic electroluminescent device comprising an inorganic charge barrier layer provided on both sides or any one side of the above. 2. The organic semiconductor layer has a specific resistance of 1 × 10 ⁻¹
The organic electroluminescence device according to claim 1, wherein the value is within a range of 1 to 10 ⁹ Ω · cm. 3. The organic semiconductor layer has a thickness of 0.1 to 50.
3. The organic electroluminescent device according to claim 1, wherein the value is within a range of 0 nm. 4. The organic semiconductor layer is a combination of an organic compound and an oxidizing dopant, a combination of an organic compound and a reducing dopant, or a combination of an organic compound and conductive fine particles. The organic electroluminescent element according to any one of the above. 5. An inorganic charge barrier layer provided between the anode layer and the organic light emitting layer, wherein the inorganic charge barrier layer comprises silicon oxide, ZnO, GaN,
InGaN, p-type a-Si _1-x C _x (0.5 <x <
1), at least one inorganic compound selected from the group consisting of a-Si _1-x N _x (0.4 <x <1) and diamond-like carbon, or at least one compound selected from the following group A The organic electroluminescent device according to any one of claims 1 to 4, wherein the organic electroluminescent device is a combination of at least one compound selected from Group B and Group B. Group A: Si, Ge, Sn, Pb, Ga, In, Zn, C
d, Mg chalcogenide or nitride Group B: Periodic Table 5A to 8 group compounds 6. An inorganic charge barrier layer provided between the cathode layer and the organic light emitting layer, wherein the inorganic charge barrier layer is made of an alkali metal chalcogenide, an alkaline earth metal chalcogenide, an alkali metal halide and an alkaline earth metal halide. The organic electroluminescence device according to any one of claims 1 to 5, wherein the organic electroluminescence device is at least one inorganic compound selected from the group consisting of: 7. An inorganic charge barrier layer provided between the cathode layer and the organic light-emitting layer may be made of Li ₂ O, LiF, CsF, Cs ₂
O, LiCl, BaO, SrO, MgO, MgF ₂ , S
rCl ₂ , n-type a-SiC, n-type a-Si _1-x N
The organic electroluminescent device according to any one of claims 1 to 6, wherein the organic electroluminescent device is at least one inorganic compound selected from the group consisting of _x (0.1 <x <0.7). 8. The inorganic charge barrier layer has a thickness of 1 to 1,0.
2. A value within a range of 00 nm.
The organic electroluminescent device according to any one of claims 1 to 7. 9. The method according to claim 1, wherein the electron mobility of the organic light emitting layer is μ.
_e, the hole mobility when the mu _h, the organic electroluminescent device according to any one of claims 1-8, characterized by satisfying the following conditions. μ _h > μ _e > μ _h / 1000 10. The method for manufacturing an organic electroluminescence device according to claim 1, wherein the organic electroluminescent device is provided between the anode layer and the organic light emitting layer and between the cathode layer and the organic light emitting layer, or A method for manufacturing an organic electroluminescent device, comprising a step of forming an organic semiconductor layer and an inorganic charge barrier layer by a vapor deposition method or a sputtering method between any one of them.