JP2000340364A - Organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent damage by sputtering, and improve an electron implantation efficiency and luminous efficiency by forming an electron implantation electrode by sputtering and including organic electron transport compound and metal phthalocyanine compound in an organic electron transport layer in contact with an inorganic electron implantation layer. SOLUTION: Preferably, electron implantation transporting compound is set to tris (8-quinolinolato) aluminum, metal phthalocyanine compound is set to copper phthalocyanine compound, and the thickness of an organic electron transport layer including them is set to 5-40 nm. A hole implantation electrode 2 is formed on a substrate 1, an organic hole implantation layer 3, an organic hole transport layer 4, a light emitting layer 5, an organic electron transport layer 6, an organic electron transport layer 7 including the metal phthalocyanine compound, an inorganic electron implantation layer 8, and electron implantation electrode 9 are formed in this order, and the hole implantation electrode 2 and the electron implantation electrode 9 are connected to a drive power source E.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic EL (electroluminescence) device, and more particularly to a device that emits light by applying an electric field to a thin film of an organic compound.

[0002]

2. Description of the Related Art Organic EL devices can be formed on glass in a large area, and are being researched and developed for displays and the like. In general, an organic EL element has a transparent electrode such as ITO (tin-doped indium oxide) formed on a glass substrate, and an organic amine-based hole transport layer, an electron conductive layer and strong light emission, such as Alq3 [ An organic light emitting layer made of [tris (8-quinolinolato) aluminum] material is laminated, and further, an electrode having a small work function such as MgAg is formed as a basic element.

[0003] The device structure reported so far has a structure in which one or more organic compound layers are interposed between a hole injection electrode and an electron injection electrode.
The organic compound layer has a two-layer structure or a three-layer structure.

[0004] Examples of the two-layer structure include a structure in which a hole transport layer and a light emitting layer are formed between a hole injection electrode and an electron injection electrode, or a structure in which a light emitting layer and an electron transport layer are provided between a hole injection electrode and an electron injection electrode. There is a formed structure. As an example of the three-layer structure, there is a structure in which a hole transport layer, a light emitting layer, and an electron transport layer are formed between a hole injection electrode and an electron injection electrode.
Also, a single-layer structure in which a single layer has all the functions has been reported for polymers and mixed systems.

In these organic EL devices, reliability is a common problem. That is, the organic EL element has a hole injection electrode and an electron injection electrode in principle, and requires an organic layer for injecting and transporting holes and electrons efficiently between these electrodes. However, these materials are susceptible to damage at the time of manufacturing, and have a problem in affinity with electrodes. In addition, degradation of organic thin film
(Light emitting diode) and LD (laser diode).

In particular, when a metal or inorganic compound layer is formed on an organic layer by sputtering, there is a problem that the organic layer is damaged and the performance of the device is deteriorated. In particular, when the electron injection electrode is formed by sputtering, since this electrode layer has a considerable thickness, the time required for forming the sputtering is considerably long, and the damage due to the sputtering tends to increase. Therefore, there is a demand for a proposal of an element structure that improves performance in consideration of such problems.

[0007] G. Parthasarathy, P.E. Burrows, V.kh
alfin, V.G.Kozlov, S.R.Forrest, Appl.Phys.Lett.,72(1
7), 2138 (1998) contains metals for organic semiconductor devices.
No cathode has been proposed, and a cathode with improved transparency has been proposed.
Conventional translucent M with ITO as a sword material
g: Copper phthalocyanine with ITO in place of Ag thin film
Use Nin thin film (Zinc phthalocyanine is acceptable)
It has been shown. The organic EL element shown here is
Hole injection efficiency on glass substrate covered with ITO film
30-60 Angstrom thick copper lid for better performance
A Russiannin film is formed by vacuum evaporation,
Hole transport layer with a thickness of 00 Å (hole transport material
Represents 4,4'-bis [N- (1-naphthyl) -N
-Phenyl-amino] biphenyl), and 400-5
A light-emitting electron transporting layer having a thickness of
Alq3 was used as the electron transport material, and the first 200
Dope coumarin 6 into the thick part of Angstrom)
Formed in order, and further 30-60 angstroms
To form a copper phthalocyanine film having a thickness of
_TwoTransfer to atmosphere equipment, 400 ~
600 angstrom thick ITO film with copper phthalocyanine
It is formed on a film. In this element,
Performance equivalent to using a Mg: Ag thin film
It has been. In addition, an ITO film is formed on the copper phthalocyanine film.
Formed on the organic layer during sputtering of the ITO film.
Damage is reduced, and
Is shown to decrease.

Although the provision of a copper phthalocyanine film can be expected to help improve the performance of the device as described above, it is not sufficient.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent damage due to sputtering, improve electron injection efficiency and the like, improve luminous efficiency, reduce operating voltage,
An object of the present invention is to provide a long-life organic EL device.

[0010]

This and other objects are achieved by the present invention described below. (1) In an organic EL device having a hole injection electrode and an electron injection electrode and having an organic layer containing an organic compound between these electrodes, an organic hole injection layer and / or an organic hole are provided on the hole injection electrode. A transport layer, a light-emitting layer, and at least two layers containing an organic electron injecting and transporting compound.
An organic EL device comprising: an organic electron transporting layer; and an inorganic electron injecting layer containing an inorganic compound. The electron injecting electrode is further formed on the inorganic electron injecting layer. Is formed by sputtering, and the organic electron transporting layer in contact with the inorganic electron injecting layer contains an organic electron injecting and transporting compound and a metal phthalocyanine compound. (2) The organic EL device according to (1), wherein the electron injecting / transporting compound is tris (8-quinolinolato) aluminum. (3) The organic EL device according to (1) or (2), wherein the metal phthalocyanine compound is a copper phthalocyanine compound. (4) The organic electron transporting layer containing the electron injecting and transporting compound and the metal phthalocyanine compound has a thickness of 5 to 40.
The organic EL device according to any one of the above (1) to (3), which has a nm.

The above-mentioned Appl. Phys. Lett., 72 (17), 213
8 (1998) shows a copper phthalocyanine thin film on which ITO is mounted as a cathode material, but the device configuration is completely different from that of the present invention. That is, as in the present invention, an organic electron transporting layer containing a metal phthalocyanine compound is indispensable, there is no mention of providing two or more organic electron transporting layers, and there is no description about combining an inorganic electron injecting layer. Nor is it shown at all.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The organic EL device of the present invention has a hole injection electrode, an electron injection electrode, and one or more organic layers provided between these electrodes, and an inorganic electron is provided between the organic layer and the electron injection electrode. An injection layer is provided. The organic layer is an organic hole injection layer and / or an organic hole transport layer from the hole injection electrode side,
It has a light emitting layer and two or more organic electron transport layers.
Of the two or more organic electron transporting layers, at least the uppermost organic electron transporting layer in contact with the inorganic electron injecting layer contains an organic injecting electron transporting compound and a metal phthalocyanine compound. Further, the organic EL device of the present invention is formed in the above-mentioned layer arrangement from the hole injection electrode, and finally, the electron injection electrode is formed by sputtering.

As described above, in the present invention, two or more organic electron transporting layers are provided, and the organic electron transporting layer provided in contact with the inorganic electron injecting layer contains a metal phthalocyanine compound in addition to the organic injecting electron transporting compound. Therefore, damage to the organic layer when the electron injection electrode is formed by sputtering can be prevented, and the electron injection efficiency and the like can be improved, and the initial characteristics can be improved (the driving voltage decreases and the luminance increases (20%). And the life is extended.
On the other hand, if no metal phthalocyanine compound film is provided, including the organic electron transporting layer containing the metal phthalocyanine compound, damage to the organic layer is increased, driving voltage is increased, and luminance is low. On the other hand, when only one organic electron transport layer containing no metal phthalocyanine compound is laminated and laminated with a metal phthalocyanine compound film, the initial characteristics are improved, but the life is short.

The organic EL device of the present invention may have, for example, a configuration as shown in FIG. 1. As shown in FIG. 1, a hole injection electrode 2 is formed on a substrate 1, and an organic EL device is further formed thereon. A hole injection layer 3, an organic hole transport layer 4, an emission layer 5, an organic electron transport layer 6, an organic electron transport layer 7 containing a metal phthalocyanine compound, an inorganic electron injection layer 8, and an electron injection electrode 9 formed in this order. It is. The hole injection electrode 2 and the electron injection electrode 9 are connected to a driving power source E.

The organic EL device of the present invention is not limited to the illustrated example, and has at least one organic electron transporting layer having at least two organic electron transporting layers and an inorganic electron injecting layer in contact with the inorganic electron injecting layer. Only needs to contain a metal phthalocyanine compound, but the structure shown in the drawing is preferable in consideration of performance, production, and the like. In addition, each of the organic electron transport layers 6 and 7 and the inorganic electron injection layer 8 may have a multilayer structure.
The organic hole injection layer 3 or the organic hole transport layer 4
(In such a case, it may be referred to as an organic hole injecting and transporting layer). In addition, various changes can be made within the scope of the present invention.

In the present invention, the organic layer is a layer containing an organic compound as a main component (at least 50 wt%), and the organic compound includes a metal complex coordinated with the organic compound. . On the other hand, the inorganic layer is a layer containing an inorganic compound as a main component (at least 50% by weight).

In the electrode layer, at the contact interface between the layers, the constituent components may be mutually diffused.

The organic EL device of the present invention has two or more organic electron transporting layers, and the organic electron transporting layer in contact with the inorganic electron injecting layer contains an organic electron injecting and transporting compound and a metal phthalocyanine compound.

The metal phthalocyanine compound is not particularly limited and may be any known one. As the central metal, Cu, Fe, Zn, Co, Pt, Cr, Ni, Pd
And the like, and Cu and Zn are preferable, and Cu is particularly preferable.

Examples of the organic electron injecting / transporting compound include quinoline derivatives such as an organometallic complex having 8-quinolinol such as tris (8-quinolinolato) aluminum (Alq3) or a derivative thereof as a ligand, oxadiazole derivatives, perylene Derivatives, pyridine derivatives, pyrimidine derivatives, quinoxaline derivatives, diphenylquinone derivatives, nitro-substituted fluorene derivatives and the like can be used.

Examples of the organic electron injecting and transporting compound include quinoline derivatives, metal complexes having 8-quinolinol or a derivative thereof as a ligand, particularly aluminum complexes, particularly tris (8-quinolinolato) aluminum (A
It is preferred to use lq3). Also, JP-A-8-1
It is also preferable to use a phenylanthracene derivative disclosed in JP-A-2600 and a tetraarylethene derivative disclosed in JP-A-8-12969.

The quinolinolato aluminum complex preferably used in the present invention is described in JP-A-63-26469.
No. 2, JP-A-3-255190, JP-A-5-7073
3, JP-A-5-258859, JP-A-6-2158
No. 74 and the like.

Specifically, first, tris (8-quinolinolato) aluminum, bis (8-quinolinolato) magnesium, bis (benzo {f} -8-quinolinolato) zinc, bis (2-methyl-8-quinolinolato) aluminum Oxide, tris (8-quinolinolato) indium,
Tris (5-methyl-8-quinolinolato) aluminum, 8-quinolinolatolithium, tris (5-chloro-
8-quinolinolato) gallium, bis (5-chloro-8-
Quinolinolato) calcium, 5,7-dichloro-8-quinolinolatoaluminum, tris (5,7-dibromo-
8-hydroxyquinolinolato) aluminum and poly [zinc (II) -bis (8-hydroxy-5-quinolinyl) methane].

In addition to 8-quinolinol or a derivative thereof, an aluminum complex having another ligand may be used, such as bis (2-methyl-
8-quinolinolato) (phenolato) aluminum (III)
, Bis (2-methyl-8-quinolinolato) (ortho-
Cresolato) aluminum (III), bis (2-methyl-
8-quinolinolato) (meth-cresolate) aluminum
(III), bis (2-methyl-8-quinolinolato) (para-cresolato) aluminum (III), bis (2-methyl-8-quinolinolato) (ortho-phenylphenolate)
Aluminum (III), bis (2-methyl-8-quinolinolato) (meth-phenylphenolato) aluminum (II
I), bis (2-methyl-8-quinolinolato) (para-
Phenylphenolato) aluminum (III), bis (2-
Methyl-8-quinolinolato) (2,3-dimethylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (2,6-dimethylphenolato) aluminum (III), bis (2-methyl- 8-quinolinolato)
(3,4-dimethylphenolato) aluminum (III),
Bis (2-methyl-8-quinolinolato) (3,5-dimethylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (3,5-di-tert-butylphenolato) aluminum (III) ), Bis (2-methyl-8)
-Quinolinolato) (2,6-diphenylphenolato) aluminum (III), bis (2-methyl-8-quinolinolato) (2,4,6-triphenylphenolato) aluminum (III), bis (2-methyl- 8-quinolinolato)
(2,3,6-trimethylphenolato) aluminum (I
II), bis (2-methyl-8-quinolinolato) (2,
3,5,6-tetramethylphenolato) aluminum (I
II), bis (2-methyl-8-quinolinolato) (1-naphthrat) aluminum (III), bis (2-methyl-8
-Quinolinolato) (2-naphthrat) aluminum (II
I), bis (2,4-dimethyl-8-quinolinolato)
(Ortho-phenylphenolato) aluminum (III),
Bis (2,4-dimethyl-8-quinolinolato) (para-
Phenylphenolato) aluminum (III), bis (2,
4-dimethyl-8-quinolinolato) (meta-phenylphenolato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) (3,5-dimethylphenolato) aluminum (III), bis (2 4-dimethyl-8
-Quinolinolato) (3,5-di-tert-butylphenolato) aluminum (III), bis (2-methyl-4-ethyl-8-quinolinolato) (para-cresolato) aluminum (III), bis (2-methyl) -4-methoxy-8-quinolinolato) (para-phenylphenolato) aluminum (III), bis (2-methyl-5-cyano-8-quinolinolato) (ortho-cresolato) aluminum (III),
Bis (2-methyl-6-trifluoromethyl-8-quinolinolato) (2-naphthrat) aluminum (III);

In addition, bis (2-methyl-8-quinolinolato) aluminum (III) -μ-oxo-bis (2-
Methyl-8-quinolinolato) aluminum (III), bis (2,4-dimethyl-8-quinolinolato) aluminum
(III) -μ-oxo-bis (2,4-dimethyl-8-quinolinolato) aluminum (III), bis (4-ethyl-
2-methyl-8-quinolinolato) aluminum (III)-
μ-oxo-bis (4-ethyl-2-methyl-8-quinolinolato) aluminum (III), bis (2-methyl-4
-Methoxyquinolinolato) aluminum (III) -μ-oxo-bis (2-methyl-4-methoxyquinolinolato)
Aluminum (III), bis (5-cyano-2-methyl-
8-quinolinolato) aluminum (III) -μ-oxo-
Bis (5-cyano-2-methyl-8-quinolinolato) aluminum (III), bis (2-methyl-5-trifluoromethyl-8-quinolinolato) aluminum (III) -μ
-Oxo-bis (2-methyl-5-trifluoromethyl-8-quinolinolato) aluminum (III) and the like.

In the present invention, tris (8-quinolinolato) aluminum (Alq3) is particularly preferred.

The ratio of the electron injecting / transporting compound to the metal phthalocyanine compound in the electron transporting layer containing the electron injecting / transporting compound and the metal phthalocyanine compound is expressed by the formula: electron injecting / transporting compound / metal phthalocyanine compound (weight ratio).
Is preferably from 4/1 to 1/4, and more preferably from 3/2 to 2/3.

Each of these compounds may be used alone or in combination.
More than one species may be used in combination. These compounds may be uniformly mixed in the layer, or may be a gradient film having a concentration gradient in the film thickness direction. In the case of a gradient film, the content of the metal phthalocyanine compound is preferably increased on the inorganic electron injection layer side, and may be gradually reduced on the organic electron transport layer side. However, it is preferable to mix them almost uniformly from the viewpoint of ease of production.

By setting the ratio of both compounds within the above range, it is possible to effectively prevent spatter damage without impairing the function as an element. On the other hand, when the amount of the metal phthalocyanine compound is small, the effect of preventing sputter damage is insufficient, and when the amount is large, the performance as an element is likely to be deteriorated.

The organic electron transporting layer containing the metal phthalocyanine compound is usually preferably formed as a single layer, but may be formed in a multilayer structure. The thickness is preferably 5 to 40 nm (50 to 400 angstroms) in total when forming a multilayer structure. If this layer is too thin, the effect of preventing sputter damage cannot be sufficiently obtained, and if it is too thick, the initial characteristics are reduced and the element life is shortened.

On the other hand, the organic electron injecting and transporting compound used in the organic electron transporting layer below the organic electron transporting layer containing the metal phthalocyanine compound is the same as that used in the organic electron transporting layer containing the metal phthalocyanine compound. The same applies to preferable ones, and particularly, tris (8-quinolinolato) aluminum (Alq3) is preferably used. Usually, this layer is preferably composed of only one layer, but it may have a multilayer structure. This layer preferably has a total thickness of 5 to 30 nm in a multilayer structure. Further, the ratio of the thickness of the organic electron transporting layer to that of the metal phthalocyanine compound-containing organic electron transporting layer is preferably 4/1 to 1/4.

The organic electron transporting layer can be formed by a vacuum evaporation method or the like.

The organic EL device of the present invention has an inorganic electron injecting layer between the organic electron transporting layer containing the above metal phthalocyanine compound and the negative electrode serving as an electron injecting electrode.

The inorganic electron injecting layer preferably has a work function of 4 eV or less as a first component, more preferably 1 to 4 eV, preferably Li, Na, K, Rb, Cs and Fr.
One or more alkali metal elements selected from, or
It preferably contains an oxide of one or more alkaline earth metal elements selected from Mg, Ca and Sr, or one or more lanthanoid elements preferably selected from La and Ce. Among these, especially lithium oxide, magnesium oxide, calcium oxide,
Cerium oxide is preferred. When these are mixed and used, the mixing ratio is arbitrary. Further, it is preferable that lithium oxide is contained in the mixture in an amount of 50 mol% or more in terms of Li ₂ O.

The inorganic electron injection layer further contains, as a second component, at least one element selected from Zn, Sn, V, Ru, Sm and In. In this case, the content of the second component is preferably 0.2 to 40 mol%, more preferably 1 to 20 mol%. When the content is small, the electron injection function is reduced, and when the content is large, the hole blocking function is reduced. When two or more kinds are used in combination, the total content is preferably in the above range. The second component may be in a metal element state or an oxide state.

By including the conductive (low-resistance) second component in the high-resistance first component, the conductive material is present in the insulating material in the form of islands. It is believed that a hopping path is formed.

The oxide of the first component usually has a stoichiometric composition, but may deviate slightly from this to have a non-stoichiometric composition. The second component also usually exists as an oxide, and the same applies to this oxide.

In the high-resistance inorganic electron injecting layer, H, Ne, Ar, K
r, Xe, etc. may be contained in a total of 5 at% or less.

The average value of the entire high-resistance inorganic electron injection layer is not necessarily uniform as long as it has such a composition, and a structure having a concentration gradient in the film thickness direction may be employed.

The high resistance inorganic electron injection layer is usually in an amorphous state.

The resistivity of the high-resistance inorganic electron-injecting layer is preferably 1 to 1 × 10 ¹¹ Ω · cm, particularly 1 × 10 ³ to 1 × 10 ¹¹ Ω · cm.
× 10 ⁸ Ω · cm. By setting the resistivity of the high-resistance inorganic electron injection layer within the above range, the electron injection efficiency can be dramatically improved while maintaining high hole blocking properties. The resistivity of the high-resistance inorganic electron injection layer can also be determined from the sheet resistance and the film thickness.

Thus, by arranging the inorganic electron injection layer having an electron conduction path and capable of blocking holes between the organic layer and the electron injection electrode (negative electrode), electrons can be efficiently injected into the light emitting layer. As a result, the luminous efficiency is improved and the driving voltage is reduced.

Preferably, the second component of the high-resistance inorganic electron injecting and transporting layer is contained in an amount of 0.2 to 40 mol% based on all components.
By forming a conductive path by containing the compound, electrons can be efficiently injected from the electron injection electrode to the organic layer on the light emitting layer side. In addition, the movement of holes from the organic layer to the electron injection electrode can be suppressed, and the recombination of holes and electrons in the light emitting layer can be performed efficiently. Further, an organic EL device having both the advantages of the inorganic material and the advantages of the organic material can be obtained. The organic EL device of the present invention has a luminance equal to or higher than that of a conventional device having only an organic electron injection layer, and has a higher heat resistance and a higher weather resistance. Less occurrence of dark spots. Further, not only relatively expensive organic substances but also inorganic materials which are inexpensive, easily available and easily manufactured can be used to reduce manufacturing costs.

The thickness of the high resistance inorganic electron injection layer is as follows.
Preferably, it is about 0.2 to 30 nm, particularly about 0.2 to 20 nm. If the electron injection layer is thinner or thicker, the function as the electron injection layer cannot be sufficiently exhibited.

The method for producing the high-resistance inorganic electron-injecting layer is preferably a sputtering method. Among them, multi-source sputtering for separately sputtering the first component and the second component targets is preferable. By using multi-source sputtering, a sputtering method suitable for each target can be used. Further, in the case of one-source sputtering, a mixed target of the first component and the second component may be used. Further, an evaporation method may be used.

When a high-resistance inorganic electron injecting layer is formed by a sputtering method, the pressure of a sputtering gas at the time of sputtering is set to 0.1.
The range of 1 to 1 Pa is preferred. The sputtering gas is an inert gas used in a normal sputtering apparatus, for example, Ar, N
e, Xe, Kr, etc. can be used. Also, if necessary, N ₂
May be used. As an atmosphere at the time of sputtering, reactive sputtering may be performed by mixing about ₁ to 99 vol% of O ₂ in addition to the above-mentioned sputtering gas.

As a sputtering method, a high frequency sputtering method using an RF power source, a DC sputtering method, or the like can be used. The power of the sputtering apparatus is preferably in the range of 0.1 to 10 W / cm ² by RF sputtering, and the film formation rate is preferably in the range of 0.5 to 10 nm / min, particularly 1 to 5 nm / min.

The substrate temperature during film formation is room temperature (25
C) to about 150C.

The inorganic electron injecting layer has a function of facilitating the injection of electrons from the cathode, a function of stably transporting electrons, and a function of hindering holes. It may have a function of increasing / confining, optimizing a recombination region, and improving luminous efficiency.

Such an inorganic insulating electron injection layer mainly comprises
Lithium oxide (Li_TwoO), rubidium oxide
(Rb_TwoO), potassium oxide (K_TwoO), sodium oxide
(Na _TwoO), cesium oxide (Cs_TwoO), stron oxide
Titanium (SrO), magnesium oxide (MgO), and
One or more of calcium oxide (CaO)
Have. These may be used alone or as a mixture of two or more.
May be used in combination.
Optional. Among them, strontium oxide
Is most preferred, followed by magnesium oxide and calcium oxide.
Cium and lithium oxide (Li_TwoO) preferred
And then rubidium oxide (Rb_TwoO), followed by oxide
Lium (K_TwoO) and sodium oxide (Na_TwoO)
preferable. When these are used in combination,
Of which strontium oxide is more than 40 mol% or acid
The total of lithium oxide and rubidium oxide is more than 40 mol%,
In particular, it is preferably contained at 50 mol% or more.

The inorganic insulating electron injection layer preferably contains silicon oxide (SiO ₂ ) and / or germanium oxide (GeO ₂ ) as a stabilizer. Either of these may be used, or both may be mixed and used, and the mixing ratio at that time is arbitrary.

Each of the above oxides usually has a stoichiometric composition, but may deviate slightly from this and have a non-stoichiometric composition.

The inorganic insulating electron injection layer of the present invention comprises:
Preferably, each of the above components is SrO,
MgO, CaO, Li_TwoO, Rb_TwoO, K_TwoO, Na_TwoO,
Cs _TwoO, SiO_Two, GeO_TwoMain component: 80-99 mol%, more preferably 90-95
 mol%, stabilizer: 1-20 mol%, more preferably 5-10
 mol%, contained.

The thickness of the inorganic insulating electron injection layer is preferably 0.1 to 2 nm, more preferably 0.3 to 0.8.
nm.

The method for forming such an electron injection layer may be sputtering, and is the same as described above.

The light emitting layer has a function of injecting holes (holes) and electrons, a function of transporting them, and a function of generating excitons by recombination of holes and electrons. By using a relatively electronically neutral compound for the light emitting layer, electrons and holes can be easily injected and transported in a well-balanced manner.

The light emitting layer of the organic EL device contains a fluorescent substance which is a compound having a light emitting function. Examples of such a fluorescent substance include, for example, JP-A-63-26469.
No. 2 discloses at least one compound selected from compounds such as quinacridone, rubrene, and styryl dyes. Also, Tris (8
Quinolinol derivatives such as metal complex dyes having 8-quinolinol or a derivative thereof as a ligand, such as (quinolinolato) aluminum; tetraphenylbutadiene, anthracene, perylene, coronene, and 12-phthaloperinone derivatives. Further, phenylanthracene derivatives described in JP-A-8-12600 (Japanese Patent Application No. 6-110569), tetraarylethene derivatives described in JP-A-8-12969 (Japanese Patent Application No. 6-114456), and the like are described. Can be used.

It is also preferable to use a host material capable of emitting light by itself and a dopant in combination. In such a case, the content of the dopant in the light emitting layer is preferably 0.01 to 10 wt%, more preferably 0.1 to 5 wt%. By using a host material and a dopant in combination, the emission wavelength characteristics of the host material can be changed, light emission shifted to a longer wavelength becomes possible, and the luminous efficiency and stability of the device are improved.

As the host substance, a quinolinolato complex is preferable, and an aluminum complex having 8-quinolinol or a derivative thereof as a ligand is preferable. Specific examples of such an aluminum complex are the same as those of the organic electron injecting and transporting compound, and particularly preferable is tris (8-quinolinolato) aluminum.

Other host materials are disclosed in
Phenylanthracene derivative described in JP-A-12600 (Japanese Patent Application No. 6-110569) and JP-A-8-1296
No. 9 (Japanese Patent Application No. 6-114456) is also preferable.

The light emitting layer is preferably a mixed layer of at least one kind of hole injecting and transporting compound and at least one kind of electron injecting and transporting compound, if necessary.
Further, it is preferable that a dopant is contained in the mixed layer. The content of the compound in such a mixed layer is preferably 0.01 to 20% by weight, more preferably 0.1 to 15% by weight.

In the mixed layer, a hopping conduction path of carriers is formed, so that each carrier moves in a material having a favorable polarity, and injection of carriers having the opposite polarity is less likely to occur, so that the organic compound is less likely to be damaged. This has the advantage that the element life is extended. Further, by including the above-described dopant in such a mixed layer, the emission wavelength characteristics of the mixed layer itself can be changed, the emission wavelength can be shifted to a longer wavelength, and the emission intensity is increased, The stability of the device can be improved.

The compound capable of injecting and transporting holes and the compound capable of injecting and transporting electrons to be used in the mixed layer may be selected from a compound capable of injecting and transporting holes and a compound capable of injecting and transporting electrons, respectively, which will be described later. Among them, as the compound capable of injecting and transporting holes, it is preferable to use an amine derivative having strong fluorescence, for example, a triphenyldiamine derivative which is a hole transporting material, further a styrylamine derivative, or an amine derivative having an aromatic condensed ring. .

As the compound capable of injecting and transporting electrons, it is preferable to use a quinoline derivative, furthermore a metal complex having 8-quinolinol or a derivative thereof as a ligand, particularly tris (8-quinolinolato) aluminum (Alq3). It is also preferable to use the above-mentioned phenylanthracene derivatives and tetraarylethene derivatives.

Examples of the hole injecting and transporting compound include amine derivatives having strong fluorescence, such as the above-described hole injecting and transporting material, triphenyldiamine derivative, styrylamine derivative, and amine derivative having an aromatic condensed ring. It is preferably used.

The mixing ratio in this case depends on the respective carrier mobility and carrier concentration. In general, the weight ratio of the compound capable of injecting and transporting holes / the compound capable of injecting and transporting electrons is 1/99 to 99/99. 1, more preferably 10/90
To 90/10, particularly preferably 20/80 to 80/20
It is preferable that the degree is about the same.

The thickness of the mixed layer is preferably not less than the thickness corresponding to one molecular layer and less than the thickness of the organic compound layer. Specifically, the thickness is preferably 1 to 85 nm, more preferably 5 to 60 nm, particularly preferably 5 to 50 nm.

As a method of forming the mixed layer, co-evaporation in which evaporation is performed from different evaporation sources is preferable. However, when the vapor pressures (evaporation temperatures) are approximately the same or very close, they are mixed in advance in the same evaporation board. Alternatively, it can be deposited. In the mixed layer, it is preferable that the compounds are uniformly mixed, but in some cases, the compounds may exist in an island shape. The light-emitting layer is generally formed to a predetermined thickness by vapor-depositing an organic fluorescent substance or by dispersing and coating the resin in a resin binder.

The hole injecting and transporting compound used in the organic hole injecting layer and the organic hole transporting layer of the organic EL device of the present invention includes amine derivatives having strong fluorescence, such as the above-mentioned hole transporting compound such as triphenyl. It is preferable to use a diamine derivative, further a styrylamine derivative, and an amine derivative having an aromatic condensed ring.

The compound capable of injecting and transporting holes is described, for example, in JP-A-63-295695 and JP-A-2-191694.
JP, JP-A-3-792, JP-A-5-2346
No. 81, JP-A-5-239455, JP-A-5
JP-A-299174, JP-A-7-126225, JP-A-7-126226, JP-A-8-100
Various organic compounds described in JP-A-172, EP0650955A1, and the like can be used. For example, a tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD), an aromatic tertiary amine, a hydrazone derivative, a carbazole derivative, a triazole derivative, an imidazole derivative, an oxadiazole derivative having an amino group, polythiophene, etc. . These compounds may be used alone or in combination of two or more. When two or more kinds are used in combination, they may be stacked as separate layers or mixed.

The thickness of the organic hole transport layer is not particularly limited and varies depending on the forming method, but it is usually preferably about 5 to 500 nm, particularly preferably 10 to 300 nm. When a hole injection layer and a transport layer are provided, it is preferable that the thickness of the injection layer is 1 nm or more and the thickness of the transport layer is 1 nm or more. The upper limit of the thickness of the injection layer and the transport layer at this time is usually
The thickness is about 500 nm for the injection layer and about 500 nm for the transport layer.

The negative electrode (electron injecting electrode) is particularly limited in combination with the above-mentioned high resistance or insulating inorganic electron injecting layer, since it is not necessary to have a low work function and an electron injecting property. It is not necessary, and ordinary metals can be used. Among them, in terms of conductivity and ease of handling, Al, A
g, In, Ti, Cu, Au, Mo, W, Pt, Pd and Ni, in particular one or two selected from Al and Ag
Metal elements such as seeds are preferred.

The thickness of the negative electrode thin film may be a certain thickness or more that can provide electrons to the high-resistance inorganic electron injecting and transporting layer, and may be 50 nm or more, preferably 100 nm or more. Although the upper limit is not particularly limited, the film thickness may be generally about 50 to 500 nm.

The following may be used as the electron injection electrode, if necessary. For example, K, Li, Na, M
g, La, Ce, Ca, Sr, Ba, Sn, Zn, Zr
Or a two-component or three-component alloy system containing them for improving stability, for example, Ag.Mg.
(Ag: 0.1 to 50 at%), Al.Li (Li: 0.
01 to 14 at%), In.Mg (Mg: 50 to 80 at%)
%), Al.Ca (Ca: 0.01 to 20 at%), and the like.

The thickness of the electron injecting electrode thin film may be a certain thickness or more capable of sufficiently injecting electrons.
The thickness is preferably 0.5 nm or more, particularly 1 nm or more.
The upper limit is not particularly limited.
It may be about 500 nm. On the electron injection electrode,
Further, an auxiliary electrode (protection electrode) may be provided.

The thickness of the auxiliary electrode may be a certain thickness or more, preferably 50 nm or more, more preferably 100 nm or more, in order to secure electron injection efficiency and to prevent entry of moisture, oxygen or an organic solvent. A range from 100 to 500 nm is preferred. If the auxiliary electrode layer is too thin, the effect cannot be obtained, and the step coverage of the auxiliary electrode layer is reduced, and the connection with the terminal electrode is not sufficient. On the other hand, if the auxiliary electrode layer is too thick, the stress of the auxiliary electrode layer increases, which causes adverse effects such as an increase in the growth rate of dark spots.

As the auxiliary electrode, an optimum material may be selected and used depending on the material of the electron injection electrode to be combined. For example, if importance is placed on ensuring electron injection efficiency, a low-resistance metal such as Al may be used, and if importance is placed on sealing properties, a metal compound such as TiN may be used.

The total thickness of the electron injecting electrode and the auxiliary electrode is not particularly limited, but is usually 50 to 500 nm.
It should be about the degree.

The hole injecting electrode material is preferably one capable of efficiently injecting holes into the organic hole injecting or transporting layer, and is preferably a substance having a work function of 4.5 eV to 5.5 eV. Specifically, tin-doped indium oxide (IT
O), zinc-doped indium oxide (IZO), indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), and zinc oxide (ZnO) are preferable. These oxides may deviate somewhat from their stoichiometric composition. The mixing ratio of SnO ₂ with respect to In ₂ O ₃ is, 1 to 20 wt%, more preferably 5~12wt%.
The mixing ratio of ZnO to In ₂ O ₃ in IZO is usually about 12 to 32 wt%.

The hole injection electrode may contain silicon oxide (SiO ₂ ) in order to adjust the work function.
The content of silicon oxide (SiO ₂ ) is preferably about 0.5 to 10% by mol ratio of SiO _{2 to} ITO. S
The inclusion of iO ₂ increases the work function of ITO.

The electrode on the side from which light is extracted has an emission wavelength band,
The light transmittance is usually 400 to 700 nm, particularly preferably 50% or more, more preferably 80% or more, and particularly preferably 90% or more for each emitted light. If the transmittance is too low, the light emission itself from the light emitting layer is attenuated, and it becomes difficult to obtain the luminance required for the light emitting element.

The thickness of the electrode is 50 to 500 nm, especially 50 to 500 nm.
The range of -300 nm is preferred. The upper limit is not particularly limited. However, if the thickness is too large, there is a fear that the transmittance is reduced or the layer is peeled off. If the thickness is too small, a sufficient effect cannot be obtained, and there is a problem in film strength at the time of production and the like.

The electrodes are formed by sputtering, and specifically, may be formed in the same manner as the inorganic electron injection layer.

In the present invention, the conditions of the vacuum deposition for forming the organic layer are not particularly limited, but it is preferable that the degree of vacuum is 10 ⁻⁴ Pa or less and the deposition rate is about 0.01 to 1 nm / sec. Further, it is preferable to form each layer continuously in a vacuum. If they are formed continuously in a vacuum, impurities can be prevented from adsorbing at the interface between the layers, so that high characteristics can be obtained. Further, the driving voltage of the element can be reduced, and the occurrence and growth of dark spots can be suppressed.

When a plurality of compounds are contained in one layer when a vacuum evaporation method is used to form each of these layers, it is preferable to co-deposit each boat containing the compounds by individually controlling the temperature.

Further, in order to prevent deterioration of the organic layer and the electrodes of the element, it is preferable to seal the element with a sealing plate or the like. The sealing plate adheres and seals the sealing plate using an adhesive resin layer in order to prevent moisture from entering. The sealing gas is A
An inert gas such as r, He, N ₂ or the like is preferable. Further, the moisture content of the sealing gas is preferably 100 ppm or less, more preferably 10 ppm or less, and particularly preferably 1 ppm or less. Although there is no particular lower limit for the water content, it is usually about 0.1 ppm.

The material of the sealing plate is preferably a flat plate, and may be a transparent or translucent material such as glass, quartz, resin, etc., and glass is particularly preferred. As such a glass material, an alkali glass is preferable from the viewpoint of cost, and in addition, a glass composition such as soda lime glass, lead alkali glass, borosilicate glass, aluminosilicate glass, and silica glass is also preferable. In particular, soda glass, a glass material without surface treatment can be used at low cost,
preferable. As the sealing plate, other than a glass plate, a metal plate, a plastic plate, or the like can be used.

The sealing plate may be maintained at a desired height by adjusting the height using a spacer. Examples of the material of the spacer include resin beads, silica beads, glass beads, and glass fibers, and glass beads are particularly preferable. The spacer is usually a granular material having a uniform particle size, but the shape is not particularly limited, and may be various shapes as long as it does not hinder the function as the spacer. As the size, the diameter in terms of a circle is 1 to 20 μm, more preferably 1 to 10 μm, and especially 2 to 20 μm.
8 μm is preferred. Those having such a diameter have a grain length of 10
It is preferably about 0 μm or less, and the lower limit is not particularly limited, but is usually about the same as or larger than the diameter.

When a recess is formed in the sealing plate,
Spacers may or may not be used. The preferred size when used is within the above range,
Particularly, the range of 2 to 8 μm is preferable.

The spacer may be previously mixed in the sealing adhesive or may be mixed at the time of bonding. The content of the spacer in the sealing adhesive is preferably 0.01
-30 wt%, more preferably 0.1-5 wt%.

The adhesive is not particularly limited as long as it can maintain stable adhesive strength and has good airtightness, but it is preferable to use a cationic curing type ultraviolet curing epoxy resin adhesive. .

In the present invention, the substrate on which the organic EL structure is formed is an amorphous substrate such as glass or quartz, or a crystalline substrate such as Si, GaAs, ZnSe, or Z.
Examples thereof include nS, GaP, and InP, and a substrate in which a crystalline, amorphous, or metal buffer layer is formed on these crystalline substrates can also be used. As the metal substrate, Mo, Al, Pt, Ir, Au, Pd, or the like can be used, and a glass substrate is preferably used. When the substrate is on the light extraction side, it is preferable that the substrate has the same light transmittance as the above-mentioned electrodes.

Further, a large number of the elements of the present invention may be arranged on a plane. By changing the emission color of each element arranged on a plane, a color display can be obtained.

The luminescent color may be controlled by using a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film on the substrate.

As the color filter film, a color filter used in a liquid crystal display or the like may be used.
The characteristics of the color filter may be adjusted in accordance with the light emitted from the organic EL element to optimize the extraction efficiency and the color purity.

If a color filter capable of cutting off short-wavelength external light that is absorbed by the EL element material or the fluorescence conversion layer is used, the light resistance of the element and the contrast of display are improved.

An optical thin film such as a dielectric multilayer film may be used instead of the color filter.

The fluorescence conversion filter film absorbs EL light and emits light from the phosphor in the fluorescence conversion film to convert the color of the emitted light. It is formed from a fluorescent material and a light absorbing material.

As the fluorescent material, basically, a material having a high fluorescence quantum yield may be used, and it is desirable that the fluorescent material has strong absorption in the EL emission wavelength region. In practice, laser dyes and the like are suitable, and rhodamine compounds, perylene compounds, cyanine compounds, phthalocyanine compounds (including subphthalocyanines, etc.) naphthalimide compounds, condensed ring hydrocarbon compounds, condensed heterocyclic compounds A styryl compound, a coumarin compound or the like may be used.

As the binder, a material which basically does not quench the fluorescence may be selected, and a binder which can be finely patterned by photolithography, printing or the like is preferable. In the case where the hole injection electrode is formed on the substrate in contact with the hole injection electrode, a material which is not damaged when the hole injection electrode (ITO, IZO) is formed is preferable.

The light absorbing material is used when the light absorption of the fluorescent material is insufficient, but may be omitted when unnecessary. As the light absorbing material, a material that does not quench the fluorescence of the fluorescent material may be selected.

The organic EL device of the present invention is usually used as a DC drive type or pulse drive type EL device, but it can also be driven by AC. The applied voltage is usually 2 to 30
V.

The devices of the present invention may be stacked in multiple layers in the film thickness direction. With such an element structure, it is also possible to adjust the color tone of the emitted light and to make it multicolored.

The organic EL element of the present invention can be applied to various optical applications such as an optical pickup used for memory read / write, a relay device in a transmission line of optical communication, a photocoupler, etc. in addition to a display application. Can be used for devices.

[0105]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention. <Example 1> Corning product name 7 as a glass substrate
The 059 substrate was scrub-cleaned using a neutral detergent.

An ITO hole injection electrode layer having a thickness of 200 nm was formed on this substrate at a substrate temperature of 250 ° C. by an RF magnetron sputtering method using an ITO oxide target.

After the surface of the substrate on which the ITO electrode layer and the like had been formed was washed with UV / O _3, it was fixed to a substrate holder of a vacuum evaporation apparatus, and the pressure in the tank was reduced to 1 × 10 ⁻⁴ Pa or less.

Next, N, N'-
Diphenyl-N, N'-bis [N- (4-methylphenyl) -N-phenyl- (4-aminophenyl)]-1,
1′-biphenyl-4,4′-diamine was deposited at a deposition rate of 0.1%.
It was deposited at a thickness of 50 nm at 2 nm / sec. To form a hole injection layer.

Next, N, N, N ', N'-tetrakis (m-biphenyl) -1,1'-biphenyl-4,4'
-Diamine (TPD) is deposited at a deposition rate of 0.2 nm / sec.
m to form a hole transport layer.

Further, N, N, N
N ', N'-tetrakis (m-biphenyl) -1,1'
-Biphenyl-4,4'-diamine (TPD), tris (8-quinolinolato) aluminum (Alq3),
Rubrene and a total deposition rate of 0.2 nm / sec.
Evaporation was performed to a thickness of 00 nm to form a light emitting layer. TPD: Alq
A mixture of 3 = 1: 1 (volume ratio) was prepared, and rubrene was doped at 10 vol% to this mixture.

Further, while maintaining the reduced pressure, tris (8-quinolinolato) aluminum (Alq3) was evaporated at a vapor deposition rate of 0.1.
The first electron transport layer was formed by vapor deposition at 2 nm / sec to a thickness of 10 nm.

Next, tris (8-quinolinolato) aluminum (Alq3) and copper phthalocyanine (CuP
c) was deposited to a thickness of 10 nm at an overall deposition rate of 0.2 nm / sec to form a second electron transport layer. Alq3: Cu
A mixed layer of Pc = 1: 1 (weight ratio) was obtained.

Next, the substrate was transferred to a sputtering apparatus, and Li
Using a target obtained by mixing RuO ₂ with 30 mol% in ₂ O,
A high-resistance inorganic electron injection layer was formed to a thickness of 1 nm (10 angstroms). The sputtering gas at this time is A
r: 30 sccm, room temperature (25 ° C.), film formation rate 1 nm /
min, operating pressure: 0.2 to 2 Pa, and input power: 500 W. The composition of the formed inorganic electron injection layer was almost the same as that of the target. The resistivity of this layer is 1 × 10 ³ Ω · cm
Met.

Next, Al was sputtered to a thickness of 200 nm to form a negative electrode, and finally glass sealing was performed to obtain an organic EL device. This is designated as Sample No. 1.

Sample No. 2 was prepared in the same manner as in Sample No. 1 except that the second electron transport layer was not provided.
I got In addition, Sample No. 3 was obtained in the same manner except that the second electron transport layer was a layer made of only CuPc. Further, Sample No. 4 was obtained in the same manner except that no inorganic electron injection layer was provided.

These samples were placed in Ar at 10 mA / cm ²
, And the initial luminance and the driving voltage were obtained.
Similarly, the half life of luminance was determined at a constant current density of 100 mA / cm ² in Ar. Table 1 shows the results.

[0117]

[Table 1]

From Table 1, the effect of the present invention is clear.
The above-mentioned Li ₂ O and RuO ₂ were used as the inorganic electron injection layer.
Li, Na, K, Rb, Cs,
Oxides of elements selected from Fr, Mg, Ca, Sr, La and Ce, and Zn, Sn, V, Ru, Sm and I
When various combinations with elements selected from n were used, similar effects were obtained. The same was true even when the above-mentioned inorganic insulating electron injection layer was used.

[0119]

According to the present invention, damage due to sputtering can be prevented, luminous efficiency is improved, operating voltage is low,
A long-life organic EL element is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of an organic EL device of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 substrate 2 hole injection electrode 3 organic hole injection layer 4 organic hole transport layer 5 light emitting layer 6 organic electron transport layer 7 organic electron transport layer containing metal phthalocyanine compound 8 inorganic electron injection layer 9 electron injection electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07F 5/06 C07F 5/06 EF term (Reference) 3K007 AB00 AB03 AB04 AB06 BB01 BB06 CA00 CA01 CA02 CA04 CB01 DA00 DB03 EB00 EB05 FA01 FA03 4H048 AA03 AB92 VA56 VA80 VB10

Claims (4)

[Claims] 1. An organic EL device having a hole injection electrode and an electron injection electrode, and having an organic layer containing an organic compound between these electrodes, wherein an organic hole injection layer and / or An organic hole transporting layer, a light emitting layer, at least two organic electron transporting layers containing an organic electron injecting and transporting compound, and an inorganic electron injecting layer containing an inorganic compound are formed in this order. An organic EL device in which the electron injecting electrode is formed on a layer, wherein the electron injecting electrode is formed by sputtering, and an organic electron transporting layer in contact with the inorganic electron injecting layer comprises an organic electron injecting and transporting compound and a metal phthalocyanine compound. An organic EL device containing: 2. The method according to claim 1, wherein the electron injecting and transporting compound is tris (8
(E) -quinolinolato) aluminum.
L element. 3. The organic EL device according to claim 1, wherein the metal phthalocyanine compound is a copper phthalocyanine compound. 4. An organic electron transporting layer containing the electron injecting and transporting compound and the metal phthalocyanine compound has a thickness of 5%.
The organic EL device according to claim 1, wherein the thickness is from 40 to 40 nm.