JP2002367784A - Organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reliable organic EL element with low driving power voltage with element reliability such as suppressed leak obtained from the use of an insulation layer or a resistance layer as a hole injection layer and with shortcoming prevented of increase of driving power voltage. SOLUTION: The organic EL element is composed of a hole injection electrode 2, an electron injection electrode 8 and of one or more kinds of organic layers 4, 5, 6 between these two electrodes. At least one layer 5 of the organic layers has a luminescence function, and an inorganic oxide electron injection layer 7 is arranged between the organic layer 5 with the luminescence function and the electron injection electrode 8. The inorganic oxide electron injection layer 7 contains molybdenum oxide as a first component and contains, as a second component, one or more kinds of metal or metal oxide with a work function of not more than 3 eV.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescent device (organic EL device) using an organic material which emits light by recombination of holes and electrons.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for flat panel displays from the viewpoint of reducing the occupied area, and a device using an electroluminescent element (hereinafter abbreviated as EL element) which is lightweight and does not require a backlight has been developed. Attention has been paid. EL elements include organic EL elements and inorganic EL elements. Among these, the organic EL element has an advantage that it can be driven at a low voltage of about 20 V, unlike the inorganic EL element.

[0003] The structure of the organic EL device is a two-layer structure having a hole injection / transport layer and an organic light emitting layer / electron injection / transport layer between a hole injection electrode and an electron injection electrode, or an organic light emitting layer / positive layer. 2 having a hole injection transport layer and an electron injection transport layer
There is one of layer Yasushizo.

As a structure having two or more layers, there is a structure having a hole injection / transport layer, an organic light emitting layer, and an electron injection / transport layer. Alternatively, a single-layer structure having a light-emitting layer, a hole injection / transport layer, and an electron injection / transport layer in one layer is also known.

In these organic EL devices, an injection layer for efficiently injecting and transporting holes and electrons into the organic light emitting layer as in the above-described structure is required in order to obtain practical brightness at practical power. become.

In order to inject electrons efficiently in the conventional devices, it is necessary to use a metal having a low work function typified by an alkali metal, as described in JP-A-63-295695. Was needed. However, the same work also pointed out the difficulty of applying low work function metals to electronic devices because they are easily oxidized and difficult to handle.

To improve this, Japanese Patent Laid-Open No. 5-121 is disclosed.
According to Japanese Patent No. 172, an efficient electron injection layer is manufactured by using an alloy stabilized by adding lithium, which is a low work function metal, to aluminum, which is a relatively stable and inexpensive metal, as an electron injection layer. ing.

However, in the method described in Japanese Patent Application Laid-Open No. 5-121172, it is necessary to control the concentration of alkali metal in aluminum to 0.1% or less, but the co-evaporation of aluminum and alkali metal is controlled. Have difficulty. For this reason, the reproducibility is poor and the productivity is extremely low due to the difficulty in maintaining the apparatus.

On the other hand, in order to stably use an alkali metal having excellent electron injection efficiency, Japanese Patent Application Laid-Open No. 9-17574 discloses a method of inserting a compound such as an alkali metal oxide into the interface between the cathode and the organic layer. Have been. However, alkali metal compounds have high hygroscopicity and are difficult to handle as materials.
In addition, during vapor deposition, degassing is likely to occur, and the film formation rate is unstable, which causes a problem in controllability. Furthermore, since the reactivity of the alkali metal compound is high, it reacts with the steaming boat to cause corrosion of the boat, making continuous film formation difficult. At present, it is extremely difficult to apply to mass production from such a viewpoint.

Japanese Patent Application Laid-Open No. 2000-215893 discloses a material in which a high-resistance inorganic electron injecting layer contains a low work function metal such as an alkali metal. In the embodiment of the invention in this publication, it is stated that a sputtering method is preferable as a method for producing an inorganic electron injection layer. However, the material disclosed in this publication actually requires the use of a sputtering method as a manufacturing method due to its melting point and difficult handling. However, it is known that the sputtering method may damage an organic film. Have been. (Sputte
r deposition of cathodes inorganic light emittimg
diodes, LSHung, Jourmal of Applied Pbysics, Vol.
86 No.8, pp4607-4612, 1999) Therefore, it is not suitable as a method for producing a highly efficient organic EL device.

Japanese Patent Application Laid-Open No. 2000-235893 discloses S
i, Ge, Sn, Pb, Ga, In, Zn, Cd, Mg
Chalcogenides or their nitrides and the periodic table 5
An inorganic thin film layer containing a compound of Group A-8 as a hole injection layer,
A method for manufacturing an efficient organic EL device by using the electron injection layer is disclosed. However, in the method described here, as in Japanese Patent Application Laid-Open No. 2000-215983, damage to the element due to the sputtering method cannot be avoided. Furthermore, the inorganic thin film layer described in this publication is not good for all materials of the organic light emitting layer, and lacks electron injection properties.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for easily producing an organic EL device having a high luminous efficiency, a low operating voltage and a long life by using a high-resistance inorganic electron injecting layer having an excellent electron injecting property. It is to realize.

[0013]

That is, the above object is achieved by the following constitution of the present invention. (1) A hole injecting electrode, an electron injecting electrode, and one or more organic layers between these electrodes, at least one of the organic layers has a light emitting function, and the organic layer having the light emitting function. An inorganic oxide electron injection layer is provided between the layer and the electron injection electrode. The inorganic oxide electron injection layer contains a conductive metal oxide as a first component, and has a work function of 3 eV or less as a second component. Organic EL device containing one or more kinds of metals or metal oxides. (2) The organic EL device according to (1), wherein the conductive metal oxide of the first component is molybdenum oxide. (3) The organic EL device according to (1) or (2), wherein the second component is an alkali metal. (4) The above (1) to (3), wherein the content of the second component contained in the inorganic oxide electron injection layer is 1 to 70% by volume.
Any one of the organic EL devices. (5) The organic EL device according to any one of (1) to (4), wherein the content of the second component is 0.1 to 16% by mass based on the total amount of the metal components of the first component and the second component.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The organic EL device of the present invention has a hole injection electrode and an electron injection electrode on a substrate, and has at least one organic layer between these electrodes. One layer has a light emitting function, and has a metal oxide layer between the electron injection electrode and the organic layer, and the metal oxide layer preferably has a conductive metal oxide as a first component, Contains molybdenum oxide and has a work function of 3.0 eV as a second component.
It contains one or more of the following metals or metal oxides.

As described above, when the first component contains a metal having a low work function as the second component in the conductive metal oxide layer such as molybdenum oxide, the electron injection efficiency is improved and the luminous efficiency is improved. As a result, the driving voltage decreases.

The reason why the metal oxide is contained as the first component and the metal having a low work function is contained as the second component is to increase the resistance of the inorganic electron injection layer, block holes, and form a conduction path for transporting electrons. To do that. In this way, 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, electrons can be efficiently injected into the light emitting layer, and the luminous efficiency can be improved. And the driving voltage decreases.

The purpose of mixing a low work function metal with a metal oxide is to stabilize a highly reactive low work function metal. Further, there is a problem that the metal (such as aluminum) serving as an electron injection electrode and the organic layer have poor adhesion and easily peel off the film due to heat generation and the like accompanying the driving of the organic EL element, resulting in poor reliability. Here, by using a metal oxide as the inorganic electron injecting layer, the above-mentioned problem of separation can be solved.

The metal oxide used for the inorganic oxide electron injecting layer solves the above problem irrespective of insulating properties and conductivity. However, in the case of insulation, the drive voltage may increase,
Preferably, using a conductive metal oxide has a greater effect of increasing the electron injection efficiency.

The conductive metal oxide in the present invention preferably has a specific resistance of 10 ⁸ Ω · cm or less, and from the viewpoint of the high-resistance inorganic electron injection layer,
Preferably, it has a specific resistance of 10 ⁻² Ω · cm or more.

As the conductive metal oxide, molybdenum oxide
(MoO_Three ), Vanadium oxide (V _TwoO_Five ), Tin oxide
(SnO_Two ), Cupric oxide (CuO), and primary oxidation
Any oxide selected from titanium (TiO) is preferred.
Good. Among them, resistance heating steaming is easy.
Molybdenum oxide as a material that is easy to handle
(MoO_Three Is particularly preferred.

Further, molybdenum oxide (MoO ₃ ) has a planar structure in which a regular octahedral structure is continuous, and it is considered that a low work function metal such as an alkali metal is sandwiched between the molybdenum oxide and the metal to stabilize it.

The above oxides do not necessarily have to have a stoichiometric composition, and may be slightly deviated. Also,
The above oxides may be combined. When combined, the respective ratios may be adjusted as needed.

As the second component, a metal having a work function of 3 eV or less, K, Cs, Rb, Na, Sr, Li, Ba, E
Examples thereof include u, Yb, Ce, Pr, Sm, I, and Ca, and from the viewpoint of effects, alkali metals such as Li, Na, K, Rb, and Cs are preferable. The work function of the second component is 3 eV or less, particularly 2.5 eV or less. The lower limit is preferably as small as possible, and is not particularly limited, but is usually about 2.0 eV.

The second component in the inorganic oxide electron injecting layer accounts for 1 to 70% by volume, especially 30 to 60% by volume, based on all components.
Preferably, it is contained by volume. If the content is 1% by volume or less, the effect of lowering the driving voltage by the second component is reduced, and if the content is 70% by volume or more, the effect of improving the adhesion by the metal oxide film is reduced, and the reliability is deteriorated. When a metal oxide is used as the second component, the driving voltage increases.

[0025] The content of the second component is preferably 0.1 to 0.1 with respect to the total of the metal components of the first component and the second component.
It is 16% by weight, especially 4 to 12% by weight.

The second component does not need to exist uniformly in the film, but may have a gradient composition with respect to the film thickness direction. In this case, it is preferable that a large amount of the second component exists on the organic layer side. It is necessary that the entire composition be within the above range.

Further, in the inorganic oxide electron injection layer, aluminum (Al), titanium (Ti),
Specific resistance 1 such as tungsten (W) and molybdenum (Mo)
It may contain a metal of 0 ^-2 Ω · cm or less. In this case, the resistivity of the entire inorganic oxide electron injection layer is 10 ⁸ Ω · c.
The content may be adjusted so as to be in the range of m to 10 ⁻² Ω · cm.

Since the resistivity can be controlled by including the third component, the injection property of the inorganic oxide electron injection layer can be controlled, and the driving voltage of the organic EL element can be reduced.

The thickness of the inorganic oxide electron injection layer is preferably 0.3 to 30 nm, more preferably 1 to 10 nm.
It is. When the film thickness is smaller than this, the effect of the inorganic oxide electron injection layer is not sufficient, and when the film thickness is larger than this, the drive voltage is significantly increased.

The inorganic oxide electron injecting layer can be formed by a sputtering method, an EB evaporation method, an ion plating method, a resistance heating evaporation method, or the like. Co-evaporation with a multi-source evaporation source using a method is preferred. In the case of co-evaporation, reactive evaporation in which oxygen is introduced into a chamber may be performed to form a metal oxide.

The organic EL device of the present invention comprises, for example, as shown in FIG. 1, a substrate 1 / a hole injection electrode 2 / an inorganic high resistance hole injection layer 3 / a hole injection transport layer 4, a first light emitting layer 5a. / Second light emitting layer 5b, electron injection transport layer 6 / inorganic oxide electron injection layer 7, electron injection electrode 8 / protective film 9 in this order. In addition, a reverse stack in which the electron injection electrode 8 is formed on the substrate 1 side may be used. The stacked configuration may be an optimum stacked configuration according to required performance and specifications. The organic layer may have a multilayer structure in which a hole injection / transport layer, a light emitting layer, an electron injection / transport layer, and the like are stacked, or a single layer structure in which the light emitting layer has an electron injection / transport function, a hole transport function, and the like. It may be.

The material for the hole injection electrode is preferably a material capable of efficiently injecting holes into the hole injection layer or the like, and is preferably a substance having a work function of 4.5 eV to 5.5 eV. Specifically, tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), indium oxide (In
₂ O ₃ ), tin oxide (SnO ₂ ) and zinc oxide (Zn
O) having a main composition of either of them is preferable. These oxides may deviate somewhat from their stoichiometric composition. The mixing ratio of SnO ₂ to In ₂ O ₃ is 1 to 20.
% By mass, more preferably 5 to 12% by mass. Also, I
The mixing ratio of ZnO to In ₂ O _{3 in} ZO is usually
It is about 12 to 32% by mass.

The electrode on the light extraction side has an emission wavelength band,
Usually, the light transmittance for light having a wavelength of 400 to 700 nm is 5
It is preferably at least 0%, more preferably at least 80%, particularly preferably at least 90%. 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
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.

When the electron injecting electrode is used in combination with the inorganic electron injecting and transporting layer, it is not necessary to have a low work function and electron injecting property. it can. Among them, in terms of conductivity and ease of handling, Al, Ag, In, Ti, Cu, Au, Mo,
One or two or more metal elements selected from W, Pt, Pd and Ni, particularly Al and Ag are preferred.

The thickness of these electron injecting electrodes may be a certain thickness or more capable of giving electrons to the 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.

Further, when a protective layer is provided in order to protect the organic EL element from moisture in the atmosphere, it is possible to suppress deterioration caused by the generation of dark spots (called dark spots) in the element. The protective film is made of SiN, SiON, S
A film having a high water-blocking ability such as iO ₂ and Al ₂ O ₃ is preferable.

As a method for forming the protective film, a vapor deposition method, a sputtering method, a CVD method and the like can be considered, but a plasma CVD method which can be formed at a low temperature and has good step coverage is preferable.

After the organic EL device is manufactured, it is preferable to form a protective film without exposing the device to the atmosphere. The thickness of the protective film is not particularly limited, but is preferably 100 to 5000 nm. If the thickness of the protective film is smaller than this, the water blocking ability is reduced. If the thickness is larger than this, film peeling due to the stress of the protective film and the characteristics of the organic EL element are affected.

The total thickness of the electron injection electrode and the protective film is not particularly limited, but may be generally about 50 to 500 nm.

Next, the organic layer of the organic EL device will be described in detail.

The organic EL device according to the present invention includes at least one organic light emitting layer between two electrodes, at least one of which is transparent. Contains compounds.

In the organic EL device according to the present invention, the wavelength of light emitted from at least one organic light emitting layer is not particularly limited, but preferably, at least one organic light emitting layer has a wavelength of at least 380 to 780 nm. It is configured to emit white light having a continuous emission spectrum.

In the present invention, when at least one organic light emitting layer is configured to emit white light having a continuous light emission spectrum of 430 nm to 650 nm or less,
Particularly preferred.

In the present invention, the organic light-emitting layer contains a host material which is a hole-transporting compound or an electron-transporting compound or a mixture thereof, and has a hole and electron injecting function, a hole and electron transporting function, and a positive hole and electron transporting function. It preferably has a function of generating excitons by recombination of holes and electrons and contains a compound which is relatively neutral electronically.

Examples of the hole-transporting compound used as the host material of the organic light-emitting layer include a triazole derivative, an oxadiazole derivative, an imidazole derivative, a polyarylalkane derivative, a birazolin derivative, a birazolone derivative, a phenylenediamine derivative, an arylamine derivative, Amino-substituted chalcone derivatives, oxazole derivatives,
Examples include a styryl anthracene derivative, a fluorenone derivative, a hydrazone derivative, and a stilbene derivative. Further, a triphenyldiamine derivative can be preferably used.

As an example of the triphenyldiamine derivative, a tetraarylpendicine compound (triaryldiamine or triphenyldiamine: TPD) is particularly preferred.

Tetraarylbendicine compound (TDP)
Preferred specific examples are as follows.

[0049]

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[0050]

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[0051]

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As the electron transporting compound used as the host material of the organic light emitting layer, a quinoline derivative can be preferably used, and further, a metal complex having 8-quinolinol or a derivative thereof as a ligand, Tris (8-quinolinato) aluminum (A
lq3) is preferably used. Further, a phenylanthracene derivative or a tetraarylethene derivative can also be used as the electron transporting compound.

[0053]

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In the present invention, the organic light-emitting layer preferably has a structure in which a host material which is a hole-transporting compound or an electron-transporting compound or a mixture thereof is doped with a dovant as a fluorescent material. .

Further, the organic EL device according to the present invention preferably has two organic light emitting layers laminated on each other. In the case of forming two organic light emitting layers, each of them is doped with a fluorescent substance having a different light emission wavelength, thereby securing a wide light emission wavelength band and improving a degree of freedom of a color of a light emission color. be able to.

In the present invention, examples of the fluorescent substance contained as a dopant include compounds disclosed in JP-A-63-264692, specifically, rubrene-based compounds, coumarin-based compounds, quinacridone-based compounds, and dicyano. One or more compounds selected from the group consisting of compounds such as methylbiran compounds can be preferably used.

Examples of the fluorescent substance which can be preferably used in the present invention are as follows.

[0058]

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[0059]

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[0060]

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[0061]

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Further, in the present invention, JP-A-2000-26
No. 334 and the naphthacene-based compound described in JP-A-2000-26337 can also be preferably used as a fluorescent substance to be contained as a dovant, and include a rubrene-based compound, a coumarin-based compound, a quinacridone-based compound, and dicyanomethyl. When used in combination with a pyran-based compound or the like, the life of the organic EL device can be significantly improved.

In the present invention, a naphthacene-based compound which can be preferably used as a fluorescent substance to be contained as a dopant has a basic skeleton represented by the formula (I).

[0064]

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In the formula (I), R ^{1 to} R ⁴ each represent an unsubstituted or substituted alkyl, aryl, amino, heterocyclic or alkenyl group. Further, it is preferably any of an aryl group, an amino group, a heterocyclic group and an alkenyl group.

The aryl group represented by R ^{1 to} R ⁴ may be monocyclic or polycyclic, and includes condensed rings and ring assemblies. The total carbon number is preferably 6 to 30, and may have a substituent.

The aryl group represented by R ^{1 to} R ⁴ is preferably a phenyl group, (o-, m-, p-) tolyl group, pyrenyl group, perylenyl group, coronenyl group, (1)
-, And 2-) naphthyl group, anthryl group, (o-,
(m-, p-) biphenylyl group, terphenyl group, phenanthryl group and the like.

The amino group represented by R ^{1 to} R ⁴ includes
Any of an alkylamino group, an arylamino group, an aralkylamino group and the like may be used. These preferably have an aliphatic having 1 to 6 carbon atoms in total and / or 1 to 4 aromatic carbon rings. Specific examples include a dimethylamino group, a diethylamino group, a dibutylamino group, a diphenylamino group, a ditolylamino group, a bisdiphenylylamino group, and a bisnaphthylamino group.

The heterocyclic groups represented by R ^{1 to} R ⁴ include:
Examples thereof include a 5- or 6-membered aromatic heterocyclic group containing O, N, and S as a hetero atom, and a fused polycyclic aromatic heterocyclic group having 2 to 20 carbon atoms.

As the alkenyl group represented by R ^{1 to} R ⁴ , at least one of the substituents has a phenyl group (1
-, And 2-) phenylalkenyl groups, (1,2-,
And 2,2-) diphenylalkenyl groups, (1,2,2)
2-) A triphenylalkenyl group or the like is preferable, but an unsubstituted one may be used.

Examples of the aromatic heterocyclic group and the condensed polycyclic aromatic heterocyclic group include a thienyl group, a furyl group, a pyrrolyl group, a pyridyl group, a quinolyl group and a quinoxalyl group.

When R ^{1 to} R ⁴ have a substituent, at least two of these substituents are preferably any of an aryl group, an amino group, a heterocyclic group, an alkenyl group and an aryloxy group. Aryl group, amino group,
For the heterocyclic group and the alkenyl group, the above R ^{1 to} R ⁴
Is the same as

The aryloxy group as a substituent for R ^{1 to} R ⁴ is preferably an aryloxy group having an aryl group having a total of 6 to 18 carbon atoms, and specifically, an (o-, m-, p-) phenoxy group and the like. It is.

Two or more of these substituents may form a condensed ring. Further, it may be further substituted, and in that case, preferred substituents are the same as described above.

When R ^{1 to} R ⁴ have a substituent, it is preferred that at least two of them have the above substituent. The substitution position is not particularly limited, and may be any of meta, para, and ortho positions. Also, R
¹ and R ⁴ , and R ² and R ³ are preferably the same, but may be different.

Further, at least five or more, more preferably six or more, of R ^{1 to} R ⁸ are an unsubstituted or substituted alkyl group, aryl group, amino group, alkenyl group or heterocyclic group.

R ⁵ , R ⁶ , R ⁷ and R ⁸ each represent hydrogen or any of an alkyl group, aryl group, amino group and alkenyl group which may have a substituent.

The alkyl group represented by R ⁵ , R ⁶ , R ⁷ and R ⁸ preferably has 1 to 6 carbon atoms.
It may be linear or branched. Preferred specific examples of the alkyl group include a methyl group, an ethyl group,
(N, i) propyl group, (n, i, sec, tert)
-Butyl group, (n, i, neo, tert) -pentyl group and the like.

The aryl group, amino group and alkenyl group represented by R ⁵ , R ⁶ , R ⁷ and R ⁸ include the above-mentioned R ¹
For to R ⁴ is the same as. Further, R ⁵ and R ⁶ and R ⁷ and R ⁸ are preferably the same, but may be different.

In the present invention, the following compounds can be preferably used as the fluorescent substance to be contained as a dopant.

[0081]

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[0082]

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When two organic light-emitting layers are provided, it is preferable that each organic light-emitting layer contains two or more kinds of these fluorescent substances, and the two or more kinds of fluorescent substances have different emission wavelengths. .

In the present invention, the content of the dopant in the organic light emitting layer is preferably from 0.01 to 20% by weight, more preferably from 0.1 to 15% by weight.

In the present invention, the thickness of the organic light emitting layer is not particularly limited, and the preferable thickness is usually from 5 to 500 nm, more preferably from 10 to 300 nm, depending on the forming method. .

In the present invention, when two or more organic light emitting layers are formed, the thickness of each organic light emitting layer ranges from a thickness corresponding to one molecular layer to a thickness less than the thickness of the entire organic light emitting layer. Yes, specifically, 1 to 85 nm, preferably 5 to 60 n
m, more preferably 5 to 50 nm.

In the present invention, preferably, the organic light emitting layer is formed by vapor deposition.

In the present invention, the conditions for forming the organic light-emitting layer by vapor deposition are not particularly limited, but are not more than 1 × 10 ^-4 Pascal and the steaming speed is 0.01 to 10 μm.
It is preferred to be about 1 nm / sec.

In the present invention, the organic light emitting layer preferably contains a mixture of a hole transporting compound and an electron injecting and transporting compound.

When the organic light emitting layer contains a mixture of a hole transporting compound and an electron injecting and transporting compound, a hopping conduction path of carriers is formed, and each carrier is formed of a material having a polarity predominantly. And carrier injection of the opposite polarity is less likely to occur, and therefore, the compound contained in the organic light emitting layer is prevented from being damaged.
There is an advantage that the life of the element can be improved.

Further, a dobant made of a fluorescent substance is
By including the mixture of the hole transporting compound and the electron injecting and transporting compound in the organic light emitting layer, the emission wavelength characteristics of the organic light emitting layer itself can be changed, and the emission wavelength is shifted to the longer wavelength side. At the same time, the emission intensity can be improved, and further, the stability of the organic EL element can be improved.

When the organic light emitting layer contains a mixture of a hole transporting compound and an electron injecting and transporting compound, the mixing ratio between the hole transporting compound and the electron injecting and transporting compound is determined by the carrier mobility and carrier Although it is determined according to the concentration, it is generally 1/99 to 99/1, preferably 10/90 to 90/10, more preferably 20/80 to 80 by mass ratio.
/ 20, most preferably 40/60 to 60/40.

When forming an organic light emitting layer containing a mixture of a hole transporting compound and an electron injecting and transporting compound, the hole transporting compound and the electron injecting and transporting compound are put in different evaporation sources and evaporated. It is preferable to perform co-evaporation,
When the hole transporting compound and the electron injecting and transporting compound have the same or very similar vapor pressure, they can be mixed in advance in the same vapor deposition source and then subjected to steaming.

When forming an organic light emitting layer containing a mixture of a hole transporting compound and an electron injecting and transporting compound, the hole transporting compound and the electron injecting and transporting compound are uniformly mixed in the organic light emitting layer. However, it is not always necessary to mix them uniformly.

In the present invention, the organic material layer preferably has, in addition to at least one organic light emitting layer, a hole transporting layer having a function of stably transporting holes, and a function of stably transporting electrons. And an electron transport layer having the following formula: By providing these layers, it is possible to increase the number of holes and electrons injected into the organic light emitting layer, to confine the organic light emitting layer, to optimize the recombination region, and to improve the light emission efficiency. .

In the present invention, compounds that can be preferably used in the hole transport layer include, for example, tetraarylbendicine compounds (triaryldiamine or triphenyldiamine: TPD), aromatic tertiary amines,
Hydrazone derivatives, carbazole derivatives, triazole derivatives ", imidazole derivatives, oxadiazole derivatives having an amino group, polythiophenes, and the like. Among them, tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD) and triarylamine multimer (ATP) described in WO / 98/30071 can be particularly preferably used. .

Preferred specific examples of the triarylamine multimer (ATP) are as follows.

[0098]

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[0099]

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[0100]

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In the present invention, further, JP-A-63-29
No. 5695, JP-A-2-191694, JP-A-3-792
JP-A-5-234681, JP-A-5-239455, JP-A-5-299174, JP-A-7-126225, JP-A-7-126226-1 and JP-A-8-100172 And various organic compounds described in JP-A No. 650955Al can also be used for the hole injection / transport layer, the hole injection layer, and the hole transport layer.

In the present invention, two or more of these compounds may be used in combination, and when two or more of these compounds are used in combination, they may be mixed in one layer or formed as two or more layers. , May be laminated.

In the present invention, the hole transport layer can be formed by depositing the above compound. When a device is formed by vapor deposition, a uniform, thin film having a thickness of about 1 to 10 nm without pinholes can be formed. Therefore, a compound having a small ionization potential and absorbing light of a visible wavelength is formed in the hole injection layer. Even if it is used, it is possible to prevent a decrease in luminous efficiency due to a change in the color tone of the luminescent color or reabsorption.

In the present invention, compounds that can be preferably used in the electron transport layer include, for example, 8- (quinolineolato) aluminum (Alq3) such as tris (8-quinolinolato) aluminum (Alq3).
Examples thereof include an organometallic complex having quinolinol or a derivative thereof as a ligand, an oxadiazole derivative, a perylene derivative, a pyridine derivative, a pyrimidine derivative, and a quinoxaline derivative.

In the present invention, the electron transporting layer can be formed by depositing the above compound.

In the present invention, an organic light emitting layer, a hole injection / transport layer or a hole injection layer and a hole transport layer;
The conditions for forming the electron injecting / transporting layer or each of the electron injecting layer and the electron transporting layer by vapor deposition are not particularly limited, but are not more than 1 × 10 ⁻⁴ pascal and the vapor deposition rate is 0.01 to 1 nm / sec. It is preferable to set the degree. Each layer is preferably formed continuously under a reduced pressure of 1 × 10 ⁻⁴ Pa or less. By forming each layer continuously under a reduced pressure of 1 × 10 ⁻⁴ Pa or less, it is possible to prevent impurities from being adsorbed at the interface of each layer, and to obtain a high-performance organic EL device. And the driving voltage of the organic EL element is reduced, and the generation and growth of dark spots can be suppressed.

In the present invention, when two or more compounds are contained in the organic light-emitting layer, the hole transport layer, and the electron transport layer, the temperature of each boat containing the compounds is controlled individually.
It is preferable to form an organic light emitting layer, a hole transport layer, an electron injection transport layer, an electron injection layer or an electron transport layer by co-evaporation.

Further, the organic EL device of the present invention preferably has a high-resistance inorganic hole injecting and transporting layer between the light emitting layer and the hole injecting electrode as the other electrode.

As described above, by arranging the high-resistance inorganic hole injecting and transporting layer having a hole conduction path and capable of blocking electrons between the organic layer and the hole injecting electrode, holes can be efficiently injected into the light emitting layer. In addition, the luminous efficiency is improved and the driving voltage is reduced. By using such a high-resistance inorganic hole injection / transport layer, an organic EL
The film thickness of the entire device can be reduced, and a thin film device having an extremely small thickness can be obtained in combination with the thinning of the color filter layer.

Preferably, a metal or semimetal oxide such as silicon or germanium is used as the main component of the high-resistance inorganic hole injecting and transporting layer, and the work function is 4.5.
forming a conductive path by containing a metal or semimetal and / or any one or more of these oxides, carbides, nitrides, silicides, and borides of eV or more, preferably 4.5 to 6 eV; Accordingly, holes can be efficiently injected from the hole injection electrode into the organic layer on the light emitting layer side. In addition, the transfer of electrons from the organic layer to the hole 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 can achieve a luminance equal to or higher than that of a device having a conventional organic hole injection layer, and has a higher heat resistance and weather resistance. There are few 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 high-resistance inorganic hole injecting and transporting layer preferably has a resistivity of 1 to 1 × 10 ¹¹ Ω · cm, particularly 1 × 10 ¹¹ Ω · cm.
^{It is 3} to 1 × 10 ⁸ Ω · cm. By setting the resistivity of the high-resistance inorganic hole injection / transport layer in the above range, the hole injection efficiency can be dramatically improved while maintaining high electron blocking properties. The resistivity of the high-resistance inorganic hole injecting and transporting layer can also be determined from the sheet resistance and the film thickness. In this case, the sheet resistance can be measured by a four-terminal method or the like.

The material of the main component is an oxide of silicon or germanium. Preferably, in (Si _1-x Ge _x ) O _y , 0 ≦ x ≦ 1, 1.7 ≦ y ≦ 2.2, preferably 1 0.7 ≦ y ≦ 1.99. The main component of the high-resistance inorganic hole injecting and transporting layer may be silicon oxide or germanium oxide, or a mixed thin film thereof. If y is larger or smaller than this, the hole injection function tends to decrease. The composition may be determined by, for example, Rutherford backscattering or chemical analysis.

The high-resistance inorganic hole injecting and transporting layer further contains, in addition to the main components, oxides, carbides, nitrides, silicides and borides of metals (including semimetals) having a work function of 4.5 eV or more. Is preferred. Work function 4.5 eV or more,
Preferably the metal at 4.5-6 eV is preferably Au, C
u, Fe, Ni, Ru, Sn, Cr, Ir, Nb, P
At least one of t, W, Mo, Ta, Pd and Co. These are generally present as metals or in the form of oxides. Moreover, these carbides, nitrides, silicides, and borides may be used. When these are mixed and used, the mixing ratio is arbitrary. Their content is preferably from 0.2 to 40 mol%, more preferably from 1 to 2 mol%.
0 mol%. If the content is less than this, the hole injection function is reduced, and if the content exceeds this, the electron blocking function is reduced. When two or more kinds are used in combination, the total content is preferably in the above range.

The oxides, carbides, nitrides, silicides and borides of the above metals or metals (including semimetals) are usually dispersed in a high-resistance inorganic hole injecting and transporting layer.
The particle size of the dispersed particles is usually about 1 to 5 nm.
It is considered that a hopping path for transporting holes between the dispersed particles as conductors via the high-resistance main component is formed.

In the high-resistance inorganic hole injecting and transporting layer, H, Ne or A used for a sputtering gas may be additionally used.
r, Kr, Xe and the like may be contained in a total of 5 at% or less.

If the average value of the whole high-resistance inorganic hole injecting and transporting layer is such a composition, the composition may not be uniform and may have a structure having a concentration gradient in the film thickness direction.

The high-resistance inorganic hole injecting and transporting layer is usually
It is in an amorphous state.

The thickness of the high-resistance inorganic hole injecting and transporting layer is preferably 0.3 to 100 nm, more preferably 1 to 100 nm.
The thickness is preferably about 100 to 100 nm, particularly about 5 to 30 nm. Even if the high-resistance inorganic hole injecting and transporting layer is thinner or thicker, the function as the hole injecting layer cannot be sufficiently exhibited.

As a method of manufacturing the above-described inorganic hole injecting and transporting layer having a high resistance, various physical or chemical thin film forming methods such as a sputtering method and an evaporation method can be considered, but the sputtering method is preferable. Among them, multi-source sputtering in which the above main component and a target such as a metal or a metal oxide are separately sputtered 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, the composition may be adjusted by arranging small pieces of the above metal or metal oxide on the target of the main component and appropriately adjusting the area ratio of the two.

When a high-resistance inorganic hole injecting and transporting layer is formed by sputtering, the pressure of the sputtering gas during sputtering is preferably in the range of 0.1 to 1 Pa. The sputtering gas is
Inert gas used in ordinary sputtering equipment, for example, A
r, Ne, Xe, Kr, etc. can be used. Further, N ₂ may be used if necessary. As the atmosphere during sputtering,
Reactive sputtering may be performed by mixing about 1 to 99% of O ₂ in addition to the above-mentioned sputtering gas.

As the 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.

Since the organic EL device of the present invention has a high-resistance inorganic hole injecting and transporting layer, heat resistance and weather resistance are improved, and the life of the device can be extended. In addition, since an inexpensive and easily available inorganic material is used instead of a relatively expensive organic substance, the production becomes easy and the production cost can be reduced. Further, the connectivity with the electrode, which is an inorganic material, which has been a problem in the past, is improved. For this reason, generation of a leak current and generation of a dark spot can be suppressed.

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. Further, a resin material such as plastic or a material having flexibility can be used. The substrate material is
Preferably, a glass substrate or a resin material is 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.

As the 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, which has no surface treatment, can be used at low cost.

Further, in order to prevent oxidation 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, and N ₂ 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.

As the material of the sealing plate, a material different from that of the above-mentioned substrate can be used. However, it is preferable that the material is the same as the material of the substrate or has the same thermal expansion coefficient and mechanical strength.

The height of the sealing plate may be adjusted by using a spacer, and may be maintained at a desired height. Examples of the material of the spacer include resin beads, silica beads, glass beads, and glass fibers, and glass beads are particularly preferable. When a recess is formed in the sealing plate, the spacer may or may not be used.

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

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. .

The emission 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 display contrast are improved.

In addition, an optical thin film such as a dielectric multilayer film may be used instead of the color filter.

The fluorescence conversion filter film performs color conversion of the emission color by absorbing the light of the EL emission and emitting the light from the phosphor in the fluorescence conversion film. 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 an 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.) naphthaloimide compounds, condensed ring hydrocarbon compounds, condensed heterocyclic compounds A styryl compound, a coumarin compound or the like may be used.

As the binder, basically, a material that does not quench the fluorescence may be selected, and a binder that 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 does not damage the film during formation of the hole injection electrode (ITO, IZO, or the like) 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 element can be driven by direct current or pulse, and can be driven by alternating current. The applied voltage is usually 2
It is about 30V.

[0140]

Example 1 Example 1 (TPD / Alq / MoO ₃ : Li / Al Structure) As shown in FIG. 2, an ITO transparent conductive film 100 nm as a hole injection electrode 2 was formed on a glass substrate 1. . After ultrasonic cleaning was performed on the substrate 1 for 10 minutes, it was rinsed with pure water. Thereafter, baking was performed at 110 ° C. for 8 hours or more in an open state. After the substrate with ITO was subjected to UV / O ₃ cleaning, the substrate was introduced into a vacuum device and the pressure in the tank was reduced to 1 × 10 ⁻⁴ Pa or less.

As the hole injection organic layer 4, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-diphenyl-4,4′-diamine (TPD) was 20 nm, and the light emitting layer was 5 as tris (8-quinolilat) aluminum 100n
m were sequentially formed by a resistance heating evaporation method.

Next, as the inorganic oxide electron injection layer 7, M
oO ₃ and Li were formed to a thickness of 5 nm by co-evaporation using a resistance heating method. At this time, the film formation rates of MoO ₃ and Li are both set to 0.1.
Steaming was performed at a volume ratio of 1: 1 at 1 nm / sec. L
Using an Al-20atm% Li alloy as the evaporation source of i,
The power was controlled so that only Li was evaporated.

Thereafter, an electron injection electrode 8 of aluminum was formed to a thickness of 150 nm by a resistance heating method, and finally a protective film 9 of SiN was formed to a thickness of 200 nm to obtain an organic EL device.

Further, in order to check the stability of film formation, in forming the electron injection layer, the number of film formations at the time of device fabrication was 1 in conversion.
Deposition was performed for a film thickness equivalent to 00 times, but no alteration of the material boat for vapor deposition was observed, and degassing did not occur at the time of film formation, and stable film formation was performed.

FIG. 3 shows an X-ray diffraction result of the formed electron injection layer. As is apparent from the figure, no crystal is observed in the film, and the film is in an amorphous state.

When the electrical characteristics of the organic EL device thus manufactured were measured, the current density was 10 mA / cm ²
At 5.7 V, and the luminance was 320 cd / m ² .

Example 2 The optimum composition of molybdenum oxide: lithium was determined for the inorganic electron injecting layer. The molybdenum oxide: lithium composition is 10: 0, 10: 1 by volume ratio,
5: 1, 1: 1, 1: 3, 1: 6, 1:25, and the other steps were the same as in Example 1 to produce an organic EL device.

The drive voltage characteristics of the sample thus obtained were measured. FIG. 4 shows the results.

From FIG. 4, it can be seen that the drive voltage is greatly deteriorated where lithium is not contained. Also,
If the lithium concentration was too high and exceeded 70% by volume, device leakage was observed and the yield was extremely poor.

[0150] From the above results, the effect of lowering the driving voltage can be seen when a very small amount of lithium is contained in molybdenum oxide. The optimum concentration range of molybdenum oxide: lithium is 1% by volume to 70% by volume. I understand. Also,
It is understood that the content of the second component is preferably 0.1 to 16% by mass with respect to the total of the metal components of the first component and the second component.

Example 3 An optimum composition of molybdenum oxide: lithium oxide was determined for the inorganic electron injection layer. Molybdenum oxide: Lithium oxide was formed by flowing oxygen during evaporation, adjusting the degree of vacuum to 1 × 10 ⁻² Pa, and oxidizing lithium during film formation. The composition ratio of molybdenum oxide: lithium oxide is 10: 0, 10: 1, 5: 1 by volume ratio.
An organic EL device was manufactured in the same manner as in Example 1, except that the ratio was changed to 1: 1, 1: 3, 1: 6, and 1:25.

The drive voltage characteristics of the sample thus obtained were measured. The results are shown in FIG.

As is clear from FIG. 5, similarly to the third embodiment, the drive voltage is greatly deteriorated where no lithium oxide is contained. On the other hand, when the lithium oxide concentration was too high, the drive voltage was increased because the inorganic electron injection layer was insulated. Therefore, in order to suppress an increase in driving voltage, the lithium concentration is preferably 70% by volume or less.

In forming the electron injection layer, MoO ₃
An organic EL device was produced in the same manner as described above, except that a co-evaporation of Li and Mo was not performed, and a composite oxide of Li ₂ MoO ₄ was used to form a single evaporation boat. When the obtained sample was evaluated in the same manner as above, almost the same result was obtained.

Example 4 (ITO / TPD / Alq / MoO ₃ : Na / Al Structure) An organic electron injection layer was formed in the same manner as in Example 1 except that MoO ₃ and Na were formed to a thickness of 5 nm by co-evaporation. An EL device was manufactured.

When the obtained device was evaluated in the same manner as in Example 1, the voltage at a current density of 10 mA / cm ² was 5.5.
9 V and a luminance of 300 cd / m ² .

Example 5 (ITO / TPD / Alq / MoO ₃ : Cs / Al Structure) An organic electron-injecting layer was formed in the same manner as in Example 1 except that MoO ₃ and Cs were formed to a thickness of 5 nm by co-evaporation. An EL device was manufactured.

When the obtained device was evaluated in the same manner as in Example 1, the voltage at a current density of 10 mA / cm ² was 6.
0 V and a luminance of 290 cd / m ² .

Further, the organic EL devices of Examples 1, 4, and 5
The half life of luminance by continuous driving was 3000 hours or more (at 100 cd / m ² conversion) or more, indicating a sufficient life.

Example 6 (ITO / GeO ₂ : In ₂ O ₃ / distyrylarylene derivative + 3% distyrylaryleneamine derivative / Mo)
(O ₃ : Li / Al structure) On the hole injection electrode ITO, GeO ₂ : In ₂ O ₃ (sputter target composition 85:15 mol%) 1 nm was formed as an inorganic hole injection layer.

Next, a distyryl arylene derivative represented by the following chemical formula 15 as a host material was added to the organic light emitting layer:
Similarly, 3% by volume of a distyrylaryleneamine derivative represented by the following chemical formula 16 is added as a dopant substance,
An organic light emitting layer having a thickness of 100 nm was formed by co-evaporation with resistance heating.

[0162]

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[0163]

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Next, as in Example 1, an inorganic electron injecting layer was formed to a thickness of 5 nm by co-evaporation of MoO ₃ and Li, and an aluminum cathode was formed to a thickness of 150 nm to produce an organic EL device.

When the obtained device was evaluated in the same manner as in Example 1, the voltage at a current density of 10 mA / cm ² was 1
2.4 V and a luminance of 350 cd / m ² .

Example 7 In Example 1, when K and Rb were used in place of Li, substantially the same results were obtained.

Example 8 In Example 1, after forming the ITO electrode, an ATP having the following structure was formed to a thickness of 100 nm by a resistance heating evaporation method to form a hole injection layer.

[0168]

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Next, a TPD having the following structure was
A film was formed to a thickness of 0 nm to form a hole transport layer.

[0170]

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Next, as the first light emitting layer, an anthracene derivative having the following structure: TPD: rubrene was used at a volume ratio of 7.
Co-deposition was performed to a thickness of 20 nm so that the ratio became 5: 2.5: 0.3.

[0172]

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Next, the anthracene derivative and TPD were used as the host material as the second light emitting layer, and the distyryl aryleneamine derivative represented by Chemical Formula 16 of Example 6 was used as the dopant material in a volume ratio of 7.5: 2.5:
The film was formed to have a thickness of 40 nm so as to be 0.2.

Further, the above-mentioned anthracene derivative was formed into a film having a thickness of 20 nm as a third light emitting layer.

Next, as an electron injecting and transporting layer, Alq 3 was formed to a thickness of 10 nm, an inorganic electron injecting layer was formed to a thickness of 5 nm by co-evaporation of MoO ₃ and Li, and an aluminum cathode was formed to a thickness of 150 nm. The organic EL device was formed.

When the obtained device was evaluated in the same manner as in Example 1, the voltage at a current density of 10 mA / cm ² was 6.
7 V and a luminance of 840 cd / m ² .

After the device was stored at 85 ° C. for 100 hours, the emission luminance was measured in the same manner. The luminance reduction rate was 5% or less, and no noticeable deterioration was observed.

[Embodiment 9] In Embodiment 1, after forming the ITO electrode, GeO ₂ : In ₂ O ₃ was formed by sputtering.
(Sputter target composition: 85: 15 mol%) was deposited to a thickness of 1 nm to form a hole injection transport layer.

Next, as the first light emitting layer, an anthracene derivative: TPD: rubrene was used at a volume ratio of 7.5: 2.5:
Co-deposition was performed to a thickness of 20 nm so as to be 0.3.

Next, as the second light emitting layer, an anthracene derivative and TPD were used as a host material, and a distyryl aryleneamine derivative represented by Chemical Formula 16 of Example 6 was used as a dopant material. .5: 0.2
The film was formed to have a thickness of 40 nm.

Further, the above-mentioned anthracene derivative was formed into a film having a thickness of 20 nm as a third light emitting layer.

[0182] Next, as the electron injection transport layer, the Alq3 with a thickness of 10nm deposited, the inorganic electron injecting layer, in the same manner as in Example 1, was 5nm formed by co-deposition of MoO ₃ and Li, 150 nm aluminum cathode The organic EL device was formed.

When the obtained device was evaluated in the same manner as in Example 1, the voltage at a current density of 10 mA / cm ² was 4.
3 V, luminance was 900 cd / m ² .

After the device was stored at 85 ° C. for 100 hours, the emission luminance was measured in the same manner. The luminance change rate was 10% or less, and no noticeable deterioration was observed.

Comparative Example 1 (ITO / TPD / Alq / Al Structure) An organic EL device was manufactured in the same manner as in Example 1 except that no inorganic electron injection layer was formed.

The obtained device was evaluated in the same manner as in Example 12.
When evaluated, the current density was 10 mA / cm ^Two The voltage at
8.7v, brightness 210cd / m^Two Met. This is inorganic
Since the electron injection layer is not formed, the driving voltage increases and the brightness
Is considered to have decreased.

Comparative Example 2 (ITO / TPD / Alq / Mg / Al Structure) An organic EL device was manufactured in the same manner as in Example 1 except that Mg was formed to a thickness of 5 nm as an inorganic electron injection layer.

When the obtained device was evaluated in the same manner as in Example 1, the voltage at a current density of 10 mA / cm ² was 7.
The driving voltage was 6 V and the luminance was 300 cd / m ² . Further, the luminance half life in continuous driving is at most 150.
It was about time (at 100 cd / m ² ).

It is considered that this is because the adhesion between the metal and the organic layer is poor, so that the inorganic electron injecting layer is peeled off by the heat during driving, and the life is shortened. Therefore, it can be seen that the inclusion of a low work function metal in the metal oxide is extremely effective in increasing the adhesion of the film.

Comparative Example 3 (ITO / GeO ₂ : In ₂ O ₃ / IDE120 + 3%
IDE102 / MoO ₃ : Mg (1: 1) / Al) MoO ₃ and Mg (work function 3.7 eV) were co-deposited (volume ratio 1: 1) as a electron injection layer by a resistance heating method to a film thickness of 5 nm. An organic EL device was produced in the same manner as in Example 6, except that the device was formed.

When the obtained device was evaluated in the same manner as in Example 1, the voltage at a current density of 10 mA / cm ² was 1
3.7 V and a luminance of 11 cd / m ² .

Since the luminance is lower and the driving voltage is higher than in Example 5, it is understood that the low work function metal to be added to MoO ₃ is preferably 3 eV or less.

[Comparative Example 4] Sputtered inorganic electron injection layer (ITO / GeO ₂ : In ₂ O ₃ / IDE120 + 3%
IDE102 / Li ₂ O: RuO ₂ / Al structure)

As an electron injection layer, Li ₂ O: RuO ₂
(30: 70 mol%) An organic EL device was produced in the same manner as in Example 6, except that 1 nm was formed by a sputtering method under the following conditions using a target. Sputtering conditions: Pressure: 0.15 Pa Input power: 0.76 W / cm ² Sputter gas: Kr 8 cc / min Distance between substrates: 90 mm

When the obtained device was evaluated in the same manner as in Example 1, the voltage at a current density of 10 mA / cm ^{2 was} 15.7.
V, and the luminance was 10 cd / m ² .

As compared with Example 6, the luminance was lowered and the driving voltage was increased due to the spatter damage.

Comparative Example 5 (Example 9 Electron Injection Layer Control Structure) As an inorganic electron injection layer, instead of Mo ₃ Li, pasophenanthroline (BPhen) having the following structure was formed to 20 nm by co-evaporation with Li. An organic EL device was produced in the same manner as in Example 9.

[0198]

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When the obtained device was evaluated in the same manner as in Example 1, the voltage at a current density of 10 mA / cm ² was 4.
3 V and a luminance of 1000 cd / m ² .

After the device was stored at 85 ° C. for 100 hours, the emission luminance was measured in the same manner. The luminance decrease rate was 50% or more. This is the organic substance BPh
It is considered that en was coordinated with an alkali metal and crystallized. Therefore, co-evaporation with alkali metal,
It has been found that inorganic substances having high thermal stability are preferred.

[0201]

As described above, according to the present invention, the adhesion between the electron injection electrode and the organic layer is improved, and as a result, the life of the device is improved. In addition, the driving voltage can be reduced and the luminous efficiency can be improved simultaneously with the improvement of the adhesion. Moreover, it can be manufactured by a simple method using a material system which is easy to handle, and the process is simple and the manufacturing cost can be reduced. According to the present invention, a high-efficiency organic EL can be easily manufactured, so that application to various display devices is facilitated.

[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.

FIG. 2 is a schematic cross-sectional view illustrating a basic configuration of the organic EL element of Example 1.

FIG. 3 is a diagram showing an X-ray diffraction result of an electron injection electrode formed in Example 1.

FIG. 4 is a graph showing measurement results of Li concentration / drive voltage characteristics of Example 2.

FIG. 5 is a graph showing measurement results of Li concentration / drive voltage characteristics of Example 3.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 hole injection electrode 3 high-resistance inorganic hole injection layer 4 hole injection layer 5 light emitting layer 5a first light emitting layer 5b second light emitting layer 6 electron injection layer 7 inorganic oxide electron injection layer 8 electron injection electrode

Continued on the front page F term (reference) 3K007 AB00 AB03 AB04 AB06 AB13 AB15 AB18 BB01 BB06 CA01 CA05 CA06 CB01 DA00 DB03 EB00 FA01 FA02

Claims (5)

[Claims] 1. An electron-injecting electrode, an electron-injecting electrode, and at least one organic layer between these electrodes. At least one of the organic layers has a light-emitting function. Between the organic layer and the electron injection electrode
It has an inorganic oxide electron injection layer. The inorganic oxide electron injection layer contains a conductive metal oxide as a first component and at least one metal or metal oxide having a work function of 3 eV or less as a second component. Organic EL contained
element. 2. The organic EL device according to claim 1, wherein the conductive metal oxide of the first component is molybdenum oxide. 3. The organic EL device according to claim 1, wherein the second component is an alkali metal. 4. The content of the second component contained in the inorganic oxide electron injection layer is 1 to 70% by volume.
Any one of the organic EL devices. 5. The organic EL device according to claim 1, wherein the content of the second component is 0.1 to 16% by mass based on the total amount of the metal components of the first component and the second component.