JP2000048962A - Organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element having high heat-resistance and weatherability, free from generation of leakage and a dark spot, having high mass-productivity, capable of reducing the cost, and having high luminous efficiency and high brightness. SOLUTION: This organic EL element has a hole injection electrode 2, one kind or more of organic layer 4, an electron injection electrode 6 in order, on a substrate 1. An inorganic hole injection layer 3 is provided between the electrode 2 and the organic layer 4, the layer 3 contains at least one kind selected from the group comprising silicon oxide, silicon nitride, silicon carbide, germanium oxide, germanium nitride and germanium carbide, and a film surface contacting with the organic layer 4 of the hole implantation layer 3 is processed with a plasma.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an organic EL device using an organic compound.

[0002]

2. Description of the Related Art An organic EL device has a structure in which a thin film containing a fluorescent organic compound is sandwiched between an electron injection electrode and a hole injection electrode, and electrons and holes are injected into the thin film and recombined. Generate excitons,
Light emission when this exciton is deactivated (fluorescence / phosphorescence)
This is an element that emits light by utilizing.

[0003] The characteristics of the organic EL element are that it can emit a very high luminance of several hundreds to several 10,000 cd / m ² at a voltage of about 10 V, and can change the color from blue to red by selecting the kind of fluorescent substance. Is possible.

Meanwhile, an organic EL device having a structure using a tin-doped indium oxide (ITO) transparent electrode as a hole injection electrode and a tetraarylenediamine derivative as a hole injection / transport compound for a hole injection / transport layer or the like is known. It is known (JP-A-63-29569, etc.).

However, for example, N, N, N ', N'-tetrakis (-m-biphenyl) -1,1'-biphenyl-
When a layer of a tetraarylenediamine derivative such as 4,4′-diamine is formed directly on the ITO transparent electrode, there is a problem that the luminescence lifetime is not sufficient due to crystallization of the tetraarylenediamine derivative or separation of the layer.

In order to deal with such a problem, ITO
4, which is also a hole injecting and transporting compound, between the transparent electrode and the layer containing the tetraarylenediamine derivative.
4 ', 4 "-tris (-N-(-3-methylphenyl)
-N-phenylamino) triphenylamine (MTDA
It has been practiced to provide a layer containing TA) to obtain a hole injection effect and to improve the adhesion between the two layers (Japanese Patent Laid-Open No. 4-308688, etc.). However, for example, 4,4 ′, 4 ″ -tris (-N-(-3-methylphenyl) -N-phenylamino) triphenylamine has a glass transition temperature of about 80 ° C. and insufficient heat resistance. .

The organic EL element is used under a high electric field intensity in practical use and cannot escape heat generation. Therefore, the above-mentioned 4,4 ′, 4 ″ -tris (−)
N-(-3-methylphenyl) -N-phenylamino)
The heat resistance of organic materials such as triphenylamine is serious, and this causes a problem that the light emission lifetime is not sufficient. In addition, when these organic materials are deteriorated or physical properties at the interface are deteriorated, a leak is generated, a non-light emitting region called a dark spot is generated and expanded, and display quality is significantly impaired. I will.

Further, the organic materials used for the hole injection layer and the like are relatively expensive. For this reason, cost reduction is an important issue when considering application to large displays and mass-produced products.

In order to solve these problems, it has been proposed to provide an inorganic hole injection layer instead of an organic hole injection layer between an organic layer and a hole injection electrode. For example, silicon carbide is known as such an inorganic injection layer. By using an inorganic layer for the hole injection layer, heat resistance can be improved, and the life and weather resistance of the element can be improved. Further, unlike an organic material that is relatively expensive, an inorganic material that is inexpensive and easily available is used, so that the production becomes easy and the production cost can be reduced.
Furthermore, by using an inorganic material for the hole injection layer, ITO can be used.
Also, the connectivity and adhesion with the hole injection electrode are improved.
In addition, the thermal diffusivity becomes good, and the durability and life of the element are improved. However, the brightness was insufficient in comparison with the conventional organic hole injection layer.

Incidentally, the organic EL element has a problem that the injected holes and electrons often pass through the light emitting layer without recombining, resulting in poor luminous efficiency.
If the luminous efficiency is poor, the luminance will be reduced. Also,
In order to obtain a certain level of luminance, a high voltage must be applied, and the driving voltage becomes high, so that leakage occurs.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide high heat resistance, high weather resistance, low occurrence of leaks and dark spots, high mass productivity, low cost, and luminous efficiency. To provide an organic EL device having high brightness and high luminance.

[0012]

The above object is achieved by the present invention described below.

(1) A hole injection electrode and 1
At least one kind of organic layer and an electron injection electrode, and an inorganic hole injection layer between the hole injection electrode and the organic layer, wherein the hole injection layer is formed of silicon oxide, silicon nitride, Containing one or more of silicon, germanium oxide, germanium nitride and germanium carbide,
An organic EL device in which a film surface of the hole injection layer that is in contact with the organic layer is plasma-treated.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The organic EL device of the present invention has a hole injection electrode, at least one kind of organic layer, and an electron injection electrode on a substrate in order. Having an inorganic hole injection layer, the hole injection layer contains one or more of silicon oxide, silicon nitride, silicon carbide, germanium oxide, germanium nitride and germanium carbide, and the hole injection layer The film surface in contact with the organic layer is plasma-treated.

In the present invention, a high hole injection function can be obtained by making the inorganic hole injection layer have the above composition. Then, in the present invention, the surface of the inorganic hole injection layer is subjected to plasma treatment. In the above composition, defects such as oxygen vacancies are likely to occur. Therefore, by performing plasma treatment on the surface of the hole injection layer, electrons flowing from the light emitting layer to the hole injection layer are blocked at the interface without recombination with holes, so that the luminous efficiency is further improved and the luminance is increased. 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.

In the organic EL device of the present invention, by providing an inorganic hole injection layer instead of an organic hole injection 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 electrodes is also improved. Therefore, the occurrence of leaks and dark spots is small.

The inorganic hole injection layer contains at least one of silicon oxide, silicon nitride, silicon carbide, germanium oxide, germanium nitride, and germanium carbide. These may be used alone or in combination of two or more. When two or more kinds are used, the quantitative ratio is arbitrary.

In the case of the oxide, when the composition before the plasma treatment is expressed as (Si _1-a Ge _a ) O _b , 0 ≦ a ≦ 1, 0.2 ≦ b ≦ 1.8, and 0.4 It is preferable that ≦ b ≦ 1.7. If b is larger or smaller than this, the hole injection ability decreases.

In the case of nitride, when the composition before the plasma treatment is expressed as (Si _1-a Ge _a ) N _c , 0 ≦ a ≦ 1, 0.2 ≦ c ≦ 1.2, and further 0.5 It is preferable that ≦ c ≦ 1.1. If c is larger or smaller than this, the hole injection ability decreases.

In the case of carbide, when the composition before the plasma treatment is expressed as (Si _1-a Ge _a ) C _d , 0 ≦ a ≦ 1, 0.1 ≦ d ≦ 0.9, and further 0.3 ≦ Preferably, d ≦ 0.8. If d is larger or smaller than this, the hole injection ability decreases.

The hole injection layer may be a mixture of two or more of these oxides, nitrides and carbides of silicon and / or germanium, in which case the proportion is arbitrary.

In addition to the inorganic hole injection layer, H, Ne, Ar, Kr, Xe, etc. used for the sputtering gas may be used in a total of 1%.
0 at% or less may be contained.

If the average value of the whole hole injection layer is such a composition, the hole injection layer may have a concentration gradient in the film thickness direction.

The inorganic hole injection layer is usually in an amorphous state.

The thickness of the inorganic hole injection layer is 0.5 to 2
It is preferably 0 nm, particularly preferably 1 to 10 nm. If the hole injection layer is thinner or thicker than this, hole injection is not sufficiently performed, and the brightness decreases.

In the case of a configuration in which emitted light is extracted from the hole injection electrode side, the transmittance of the hole injection layer for emitted light is preferably 50% or more, particularly preferably 80% or more. When the transmittance of the emitted light is reduced, the emission itself from the light emitting layer is attenuated,
Luminance required for a light emitting element cannot be obtained.

The inorganic hole injection layer is formed by plasma CVD.
The film can be formed by a sputtering method or a sputtering method, but is preferably formed by an RF sputtering method.

In the sputtering method, the target having the same composition as the hole injection layer is usually used. The composition of the hole injection layer to be formed is almost the same as that of the target.

The pressure of the sputtering gas at the time of sputtering is 0.
The range of 5 to 5 Pa is preferred. Further, by changing the pressure of the sputtering gas within the above range during the film formation, a hole injection layer having a concentration gradient can be easily obtained.

As the sputtering gas, an inert gas used in a usual sputtering apparatus can be used. Above all, Ar, K
r or Xe, or at least one of these
It is preferable to use a mixed gas containing at least one kind of gas.

Reactive sputtering may be performed. As a reactive gas, when an oxide is formed, O ₂ , CO 2
When forming a nitride, N ₂ , NH ₃ ,
NO, NO ₂ , N ₂ O and the like are listed, and when forming a carbide, CH ₄ , C ₂ H ₂ , C ₂ H ₄ , CO and the like are listed. These reactive gases may be used alone or as a mixture of two or more.

As the sputtering method, a high frequency sputtering method using an RF power source or a DC sputtering method may be used, but the RF sputtering method is preferred. The deposition rate is 0.
The range of 5 to 10 nm / min is preferred.

In the present invention, it is preferable that the surface of the hole injection layer is subjected to plasma treatment before forming the organic layer after forming the same. By performing the plasma treatment on the surface, the electron blocking function is improved, the luminous efficiency is further increased, and the luminance is further increased.

For the plasma treatment, DC plasma may be used, but RF plasma is preferably used.

As the processing gas to be used, a gas containing O,
For example, oxygen, nitrogen oxide, carbon monoxide and the like can be mentioned, and among them, it is preferable to use oxygen. In addition, A
An inert gas such as r may be added. By performing plasma processing with such a processing gas, the surface of the hole injection layer becomes O 2
Excess or O is introduced to improve the electron blocking function.

The flow rate of the processing gas may be appropriately determined according to the type. Although the flow rate varies depending on the type and operating conditions of the gas used, 10～500SCC in normal O ₂ conversion
It is about M. The operating pressure is usually preferably about 0.3 to 1 Pa.

The high frequency applied to the high frequency induction coil generally has a frequency of about 13.56 MHz and a power of 0.1 to 0.1 MHz.
A high frequency power of about 5 kW is applied, but is not limited thereto, and a frequency and power capable of generating and maintaining plasma may be applied.

The time of the plasma treatment is 1 minute or more.
Particularly, 5 to 20 minutes are preferable.

FIG. 1 shows a structural example of the organic EL device of the present invention. The organic EL device shown in FIG. 1 has, on a substrate 1, a hole injection electrode 2, a hole injection layer 3, a light emitting layer 4, an electron injection transport layer 5, and an electron injection electrode 6 in this order. The film surface of the hole injection layer 3 which is in contact with the light emitting layer 4 is subjected to plasma processing. In addition, the organic EL element of the present invention is not limited to the illustrated example, and may have various configurations, and the electron injection transport layer 5 may not be provided.

Since the hole injecting electrode usually has a structure in which light emitted from the hole injecting electrode side is extracted, its material and thickness are preferably determined so that the transmittance of the emitted light is 80% or more. Is preferred. Specifically, for example, ITO (tin-doped indium oxide),
ZO (zinc-doped indium oxide), ZnO, SnO
₂ , In ₂ O _{3 and the} like, particularly ITO, IZO
Is preferred. The mixing ratio of SnO ₂ to In ₂ O ₃ is:
1-20 wt%, especially 5-12 wt% is preferred. In ₂ O
The mixing ratio of ZnO to ₃ is 1 to 20 wt%, particularly 5 to 20 wt%.
12 wt% is preferred. In addition, Sn, Ti, Pb, and the like may be contained in the form of oxides in an amount of 1% by weight or less in terms of oxides. The thickness of the hole injection electrode may be a certain thickness or more capable of sufficiently injecting holes, and is usually 10 to 50.
Preferably, it is about 0 nm. It is necessary that the driving voltage be low in order to improve the reliability of the element, but it is preferable that the driving voltage be 10 to 30 Ω / □ (film thickness of 50 to 300 n
m) ITO. For actual use,
The interference effect due to reflection at the interface of the hole injection electrode such as ITO fully satisfies the light extraction efficiency and color purity.
What is necessary is just to set the electrode thickness and the optical constant.

The hole injection electrode can be formed by a vapor deposition method or the like, but is preferably formed by a sputtering method. When a sputtering method is used for forming the ITO or IZO electrode, a target in which Sn ₂ or ZnO is doped into In ₂ O ₃ is preferably used. When the ITO transparent electrode is formed by the sputtering method, the luminescence luminance has less change with time than that formed by the vapor deposition. DC sputtering is preferable as the sputtering method, and the input power is 0.1 to 4
A range of W / cm ² is preferred. In particular, the power of the DC sputtering apparatus is preferably in the range of 0.1 to 10 W / cm ² , particularly preferably in the range of 0.2 to 5 W / cm ² . Further, the film formation rate is preferably in the range of 2 to 100 nm / min, particularly preferably in the range of 5 to 50 nm / min.

The sputtering gas is not particularly limited, and an inert gas such as Ar, He, Ne, Kr, and Xe, or a mixed gas thereof may be used. As the pressure at the time of sputtering such a sputtering gas,
Usually, it may be about 0.1 to 20 Pa.

As the electron injection electrode, a substance having a low work function is preferable. For example, K, Li, Na, Mg, La, C
e, Ca, Sr, Ba, Al, Ag, In, Sn, Z
It is preferable to use a single metal element such as n or Zr, or a two-component or three-component alloy system containing them for improving the stability. As an alloy system, for example, Ag · Mg (A
g: 0.1 to 50 at%), Al.Li (Li: 0.01)
１２12 at%), In · Mg (Mg: 50 to 80 at%),
Al.Ca (Ca: 0.01 to 20 at%) and the like are preferable. In addition, it is particularly preferable to use these oxides and further use lithium oxide. When the electron injection electrode is made of an oxide, the organic layer is surrounded by an oxide paired with the hole injection electrode which is an oxide such as ITO, and the weather resistance is improved. The electron injection electrode can be formed by an evaporation method or a sputtering method, but an evaporation method is preferable.

The thickness of the electron injecting electrode thin film may be a certain thickness or more for sufficiently injecting electrons.
Preferably, the thickness may be 1 nm or more. The upper limit is not particularly limited, but the thickness may be generally about 1 to 500 nm.

In the organic EL device of the present invention, a protective electrode may be provided on the electron injection electrode, that is, on the side opposite to the organic layer.
By providing the protective electrode, the electron injection electrode is protected from the outside air, moisture, and the like, the deterioration of the constituent thin film is prevented, the electron injection efficiency is stabilized, and the element life is dramatically improved. Also,
This protection electrode has a very low resistance, and also has a function as a wiring electrode when the resistance of the electron injection electrode is high. This protective electrode is made of Al, Al and a transition metal (except for Ti
), Ti or titanium nitride (TiN), and when these are used alone, at least Al: 90-1
00at%, Ti: 90-100at%, TiN: 90-1
It is preferable to contain about 00 mol%. Also,
When two or more kinds are used, the mixing ratio is arbitrary, but Al and T
In the mixing of i, the content of Ti is preferably 10 at% or less. Further, a layer containing these alone may be laminated. In particular, when Al, Al and transition metals are used as wiring electrodes described later, good effects are obtained, and TiN has high corrosion resistance and a large effect as a sealing film. TiN is
It may deviate from the stoichiometric composition by about 10%.
In addition, alloys of Al and transition metals include transition metals, especially Sc, Nb, Zr, Hf, Nd, Ta, Cu, Si, C
Preferably, the total of r, Mo, Mn, Ni, Pd, Pt, W and the like may contain 10 at% or less, more preferably 5 at% or less, particularly 2 at% or less. The lower the content of the transition metal, the lower the thin film resistance when functioning as a wiring material.

The thickness of the protective 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. The range of 100 to 1000 nm is preferred. If the protective electrode layer is too thin, the effect cannot be obtained, and the step coverage of the protective electrode layer is reduced, and the connection with the terminal electrode is not sufficient. on the other hand,
If the protective electrode layer is too thick, the stress of the protective electrode layer increases, so that the growth rate of dark spots increases. Note that the thickness when functioning as a wiring electrode is high, because the film thickness of the electron injection electrode is small, and when this is compensated for, the thickness is usually about 100 to 500 nm. Is about 100 to 300 nm.

The total thickness of the electron injecting electrode and the protective electrode is not particularly limited, but is usually 100 to 100.
It may be about 0 nm.

When the electron injection electrode and the protective electrode are formed by an evaporation method, the conditions for vacuum evaporation are not particularly limited.
The degree of vacuum is 0 ^-4 Pa or less, and the deposition rate is 0.01 to 1 nm /
It is preferable to be about 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.

When the electron injection electrode and the protective electrode are formed by the sputtering method, the pressure of the sputtering gas at the time of sputtering is set to 0.1.
The range of 1 to 1 Pa is preferred. As the sputtering gas, an inert gas used in a usual sputtering apparatus can be used.

As a sputtering method, a film may be formed by using a suitable sputtering method from a high frequency sputtering method using an RF power source, a DC sputtering method, and the like. The power of the sputtering apparatus is preferably 0.1 to 10 W / cm by DC sputtering.
^2, in the range of 10~10W / cm ² in RF sputtering. The deposition rate is 5 to 100 nm / min, particularly 10 to 50 n / min.
A range of m / min is preferred.

The electron injection electrode is patterned by a method such as mask evaporation or etching after film formation.
Thereby, element separation is performed and a desired light emitting pattern is obtained.

Next, the organic layer provided in the organic EL device of the present invention will be described.

The light emitting layer has a function of transporting holes (holes) and electrons, and a function of generating excitons by recombination of holes and electrons. It is preferable to use a relatively electronically neutral compound for the light emitting layer.

The thickness of the light emitting layer is not particularly limited and varies depending on the forming method.
It is preferable that the thickness be in the range of 10 to 300 nm.

The light emitting layer of the organic EL element 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, tetraarylethene derivatives described in JP-A-8-12969, and the like can be used.

Further, it is preferable to use in combination with a host substance capable of emitting light by itself, and it is preferable to use it as a dopant. In such a case, the content of the compound in the light emitting layer is 0.01 to 20% by weight, and more preferably 0.1 to 20% by weight.
It is preferably 1 to 15% by weight. When used in combination with a host substance, the emission wavelength characteristics of the host substance 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. Such an aluminum complex is disclosed 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.
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.

Other host materials are disclosed in
Also preferred are a phenylanthracene derivative of No. -12600 and a tetraarylethene derivative of JP-A-8-12969.

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 dopant in such a mixed layer is 0.01 to 20% by weight, more preferably 0.1 to 20% by weight, based on the total amount of the hole injecting and transporting compound and the electron injecting and transporting compound.
It is preferable that the content be 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 unlikely 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 hole injecting and transporting compound used in the mixed layer includes, for example, JP-A-63-295695, JP-A-2-191694, JP-A-3-792, and JP-A-5-234681. JP-A-5-239
455, JP-A-5-299174, JP-A-7-126225, JP-A-7-126226, JP-A-8-100172, EP065095
Various organic compounds described in 5A1 and the like can be used. For example, a tetraarylbendicine compound (triaryldiamine or triphenyldiamine:
TPD), aromatic tertiary amines, hydrazone derivatives, carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives having an amino group, polythiophene, and the like. These compounds may be used alone or in combination of two or more.

As the compound capable of injecting and transporting holes, an amine derivative having strong fluorescence, for example, a triphenyldiamine derivative, a styrylamine derivative, or an amine derivative having an aromatic condensed ring is preferably used.

As the electron injecting and transporting compound, it is preferable to use a quinoline derivative, furthermore a metal complex having 8-quinolinol or its derivative as a ligand, particularly tris (8-quinolinolato) aluminum (Alq3). It is also preferable to use a phenylanthracene derivative or a tetraarylethene derivative. An oxadiazole derivative, a perylene derivative, a pyridine derivative, a pyrimidine derivative, a quinoxaline derivative, a diphenylquinone derivative, a nitro-substituted fluorene derivative, or the like can be used. These compounds may be used alone or in combination of two or more.

The mixing ratio in this case depends on the respective carrier mobility and carrier concentration. In general, the weight ratio of the compound of the hole injecting and transporting compound / the electron injecting and transporting compound is 1/99 to 99/99. 1, more preferably 10/9
0 to 90/10, particularly preferably 20/80 to 80/2
It is preferable to set the value to about 0.

The thickness of the mixed layer is preferably not less than the thickness of 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.

Particularly preferable examples of the light emitting layer include an aluminum complex having 8-quinolinol or a derivative thereof as a ligand, and a mixed layer in which a tetraarylbendicine compound is doped with a fluorescent substance such as rubrene or coumarin. The mixing ratio of the aluminum complex having 8-quinolinol or a derivative thereof as a ligand and the tetraarylbendicine compound is preferably in the above range. The doping fluorescent substance such as rubrene,
Preferably it is 0.01 to 20 mol%.

The organic EL device of the present invention may be provided with an organic electron injection / transport layer or an organic hole transport layer as required.

The hole transporting layer has a function of stably transporting holes and a function of hindering electrons. The electron injecting and transporting layer has a function of facilitating injection of electrons from the electron injecting electrode and a function of stably transporting electrons. It has a function of transporting and a function of blocking holes. These layers increase and confine holes and electrons injected into the light emitting layer, optimize the recombination region, and improve luminous efficiency.

The thickness of the hole transporting layer and the thickness of the electron injecting and transporting layer are not particularly limited and vary depending on the forming method, but are usually about 5 to 500 nm, especially about 10 to 3 nm.
It is preferably set to 00 nm.

The thickness of the hole transport layer and the thickness of the electron injection / transport layer depend on the design of the recombination / light emitting region, but may be about the same as the thickness of the light emitting layer or about 1/10 to 10 times. When the hole or electron injection layer and the transport layer are separated from each other, it is preferable that the injection layer has a thickness of 1 nm or more and the transport layer has a thickness of 1 nm or more. At this time, the upper limit of the thickness of the injection layer and the transport layer is usually about 500 nm for the injection layer and about 500 nm for the transport layer. For such a film thickness, the injection / transport layer is
The same applies when providing layers.

In the hole transport layer, for example, JP-A-63-295695, JP-A-2-191694, JP-A-3-792, JP-A-5-23468
No. 1, JP-A-5-239455, JP-A-5-239455
299174, JP-A-7-126225,
JP-A-7-126226, JP-A-8-10017
Various organic compounds described in JP-A No. 2,650 / 955A1, etc. 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.

When two or more hole transport layers are provided,
Preferred combinations can be selected and used from the compounds for the hole transport layer. At this time, it is preferable to laminate the compounds in order from the hole injecting electrode (ITO or the like) with the smallest ionization potential. Further, it is preferable to use a compound having a good thin film property on the surface of the hole injection electrode. With such a stacking order, the driving voltage is reduced, and the occurrence of current leakage and the occurrence and growth of dark spots can be prevented. In addition, in the case of forming an element, a thin film having a thickness of about 1 to 10 nm can be made uniform and pinhole-free because evaporation is used, so that the hole transport layer has a small ionization potential and has absorption in the visible part. Even when a compound is used, it is possible to prevent a change in the color tone of the emission color or a decrease in efficiency due to reabsorption. The hole transport layer can be formed by vapor deposition of the above compound in the same manner as the light emitting layer and the like.

The electron injecting and transporting layer, which is provided as needed, includes a quinoline derivative such as an organometallic complex having 8-quinolinol such as tris (8-quinolinolato) aluminum (Alq3) or a derivative thereof as a ligand. An oxadiazole derivative, a perylene derivative, a pyridine derivative, a pyrimidine derivative, a quinoxaline derivative, a diphenylquinone derivative, a nitro-substituted fluorene derivative, or the like can be used. The electron injection / transport layer may also serve as the light emitting layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. The electron injecting and transporting layer may be formed by vapor deposition or the like, similarly to the light emitting layer.

When the electron injecting and transporting layer is divided into an electron injecting layer and an electron transporting layer, a preferable combination can be selected from the compounds for the electron injecting and transporting layer. At this time, it is preferable to stack the compounds in descending order of the electron affinity value from the electron injection electrode side. Such a stacking order is the same when two or more electron injection / transport layers are provided.

After forming each layer of the organic EL structure, Si
Inorganic materials O _X such as Teflon, a protective film may be formed using an organic material such as fluorocarbon polymers containing chlorine.
The protective film may be transparent or opaque, and the thickness of the protective film is about 50 to 1200 nm. The protective film can be formed by a general sputtering method, a vapor deposition method,
It may be formed by an ECVD method or the like.

Further, it is preferable to provide a sealing plate on the device in order to prevent oxidation of the organic layer and the electrode of the device and to protect the device from mechanical damage. The sealing plate is bonded and sealed with an adhesive resin or the like in order to prevent moisture from entering. The sealing gas is preferably an inert gas such as Ar, He, and N ₂ . 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 this 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, and resin. Glass is particularly preferred. As such a glass material, for example, soda-lime glass, lead-alkali glass, borosilicate glass, aluminosilicate glass,
Glass compositions such as silica glass are preferred. Also,
As the plate making method, a roll-out method, a download method, a fusion method, a float method and the like are preferable. As a surface treatment method for the glass material, a polishing treatment, a SiO ₂ barrier coat treatment, or the like is preferable. Among them, soda-lime glass produced by a float method and having no surface treatment can be used at a low cost, and is preferable. As the sealing plate, other than a glass plate, a metal plate, a plastic plate, or the like can be used.

The means for adjusting the height of the sealing plate is not particularly limited, but it is preferable to use a spacer. By using spacers, it is inexpensive,
A desired height can be easily obtained. 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,
Various shapes may be used as long as the function as a spacer is not hindered. The size is preferably a circle-converted diameter of 1 to 20 μm, more preferably 1 to 10 μm, and particularly preferably 2 to 8 μm. The particle having such a diameter is preferably about 100 μm or less in grain length, and the lower limit is not particularly limited, but is usually about 1 μm.

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 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 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. .

The material of the substrate is not particularly limited, and can be appropriately determined depending on the material of the electrodes of the organic EL structure to be laminated. For example, a metal material such as Al, or a transparent or transparent material such as glass, quartz, or resin. The material may be translucent or opaque. In this case, in addition to glass, ceramics such as alumina, metal sheets such as stainless steel are subjected to insulation treatment such as surface oxidation, and thermosetting resins such as phenolic resin And a thermoplastic resin such as polycarbonate.

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.

When 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.

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, thereby performing color conversion of the emission color. It is formed from a fluorescent material and a light absorbing material.

As the fluorescent material, a material having a high fluorescence quantum yield may be basically used, and it is desirable that the fluorescent material has a strong absorption in an EL emission wavelength region. Actually, laser dyes and the like are suitable, and rhodamine-based compounds, perylene-based compounds, cyanine-based compounds, phthalocyanine-based compounds (including subphthalocyanine, etc.), naphthalimide-based compounds, condensed-ring hydrocarbon-based compounds, and condensed heterocyclic-based compounds Compounds, styryl compounds,
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. Further, a material that does not suffer damage during the formation of ITO or IZO is preferable.

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

For forming an organic layer, it is preferable to use a vacuum deposition method since a uniform thin film can be formed. When a vacuum deposition method is used, a homogeneous thin film having an amorphous state or a crystal grain size of 0.1 μm or less can be obtained.

The conditions for vacuum deposition are not particularly limited.
The degree of vacuum is 0 ^-4 Pa or less, and the deposition rate is 0.01 to 1 nm /
It is preferable to set it to about 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.

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

The organic EL device of the present invention is usually used as a DC drive type EL device, but it can be AC drive or pulse drive. The applied voltage is usually 2 to 2
It is about 0V.

[0099]

Next, examples of the present invention will be shown, and the present invention will be described more specifically.

Example 1 An ITO transparent electrode thin film was formed on a Corning 7059 glass substrate by sputtering.
A film having a thickness of nm was formed and patterned. The glass substrate on which the ITO transparent electrode is formed is washed with a neutral detergent, acetone,
The resultant was subjected to ultrasonic cleaning using ethanol, pulled out of boiling ethanol, dried, and washed with UV / O ₃ .

Next, using SiO ₂ as a target, R
Film formation rate of inorganic hole injection layer by F sputtering
A film was formed to a thickness of 2 nm at nm / min. The sputtering gas at this time was Ar 100 sccm, O _{2 10} sccm, and the operating pressure was 0.5 Pa. The input power is 13.56 MHz in frequency.
It was set to 100 W with z. The composition of the formed hole injection layer is
SiO _1.7 .

Then, the surface of the hole injection layer was subjected to plasma treatment for 10 minutes using 100 sccm of O _{2 as} a treatment gas. At this time, the AC power for plasma generation has a frequency of 13.5.
The operating pressure was 0.5 Pa at 6 MHz and 2 kW. ESC
As a result of measurement by A (X-ray photoelectron spectroscopy), the surface of the hole injection layer was O-excessive than that without plasma treatment.

Next, the pressure in the tank was reduced to 1 × 10 ⁻⁴ Pa or less, and N, N, N ′, N′-tetrakis (m-biphenyl) -1,1′-biphenyl-4,4′-diamine (T
PD), tris (8-quinolinolato) aluminum (Alq3) and rubrene at an overall deposition rate of 0.2
The film was deposited to a thickness of 40 nm at nm / sec to form a light emitting layer. T
PD: Alq3 = 1: 1 (weight ratio), rubrene was set to 0.5 mol% with respect to this mixture.

Next, while maintaining the reduced pressure, tris (8-
(Quinolinolato) aluminum (Alq3) was deposited at a deposition rate of 0.2 nm / sec to a thickness of 30 nm to form an electron injection transport layer.

While maintaining the reduced pressure, AlLi was deposited at a deposition rate of 0.2 nm / min to a thickness of 5 nm to form an electron injection electrode.

Further, while maintaining the reduced pressure, a sputtering pressure of 0.3 was obtained by DC sputtering using an Al target.
An Al wiring electrode was formed to a thickness of 200 nm with Pa. At this time, Ar was used as the sputtering gas, and the input power was 500
W, the size of the target was 4 inches in diameter, and the distance between the substrate and the target was 90 mm.

Finally, a glass sealing plate was attached, and organic E
An L element was used.

The prepared organic EL device of the present invention was supplied at 10 mA /
Driven at a constant current of ² cm ² . As a result, the luminance of the organic EL device of the present invention was 700 cd / m ² . Further, the lifetime was longer than that of an organic EL device having a conventional organic hole injection / transport layer. In addition, neither leakage nor dark spots were observed.

<Comparative Example 1> An organic EL device was manufactured in the same manner as in Example 1 except that the surface of the hole injection layer was not subjected to O ₂ plasma treatment.

Then, the organic EL device was driven at a constant current of 10 mA / cm ^{2 in} the same manner as in Example 1, and the luminance was measured. The luminance was lower than that of the plasma-treated device of the present invention.

Example 2 The composition of the inorganic hole injection layer was GeO _1.8 , Si _0.5 Ge _0.5 O _1.8 , SiN ₁ , Ge
N _0.9 , Si _0.5 Ge _0.5 N _0.9 , SiC _0.8 , GeC _0.8 ,
Even with Si _0.5 Ge _0.5 C _0.7 , the same luminance as in Example 1 was obtained, and higher luminance than that without plasma treatment was obtained. Further, the surface of the hole injection layer was O-excessive or O-introduced as compared with the case where no plasma treatment was performed.

[0112]

As described above, according to the present invention, the heat resistance and weather resistance are high, the occurrence of leaks and dark spots is small, the mass productivity is high, the cost can be reduced, and the light emission is further improved. An organic EL element having high efficiency and high luminance can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration example of an organic EL element.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 hole injection electrode 3 hole injection layer 4 light emitting layer 5 electron injection transport layer 6 electron injection electrode

Claims (1)

[Claims] A substrate having a hole injection electrode, at least one kind of organic layer, and an electron injection electrode, wherein an inorganic hole injection layer is provided between the hole injection electrode and the organic layer; The hole injection layer contains at least one of silicon oxide, silicon nitride, silicon carbide, germanium oxide, germanium nitride, and germanium carbide, and a film surface of the hole injection layer in contact with the organic layer is subjected to plasma treatment. An organic EL device which has been manufactured.