JP2001057286A - Organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the oxidation and degradation of a cathode or a cathode/ organic layer interface, the change with the lapse of time or the like and to elongate the service life by comprising a hole injection electrode and a cathode, and an organic layer having a luminescent layer and located between the electrodes, forming a protective layer on the cathode, and including Al, O and N in the protective layer. SOLUTION: The thickness of a protective layer is 30-50 nm, the protective layer is formed by a reactive sputtering process, and x=0.1-1.0 and y=0.1-1.0 are preferable when an average composition of the protective film is represented by AlOxNy. The protective layer can be manufactured by various physical or chemical thin film forming methods such as a sputtering method, an EB evaporation or the like, in particular, the sputtering method is preferred. In the sputtering method to from the protective layer, the pressure of a sputtering gas is preferably within a range of 0.1-1 Pa. As the sputtering gas, an inert gas used in a conventional sputtering device, such as Ar, Ne, Xe, Kr or the like can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Organic EL devices can be formed on glass in a large area, and are being researched and developed for displays and the like. In general, an organic EL element is formed by forming a transparent electrode such as ITO on a glass substrate, and laminating an organic amine-based hole transport layer and an organic light emitting layer made of, for example, an Alq3 material which exhibits electron conductivity and emits strong light. Further, an electrode having a small work function, such as MgAg, is formed and used as a basic element.

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

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

FIGS. 2 and 3 show a typical structure of an organic EL device.

In FIG. 2, a hole transport layer 14 and a light emitting layer 15 which are organic compounds are formed between a hole injection electrode 12 and an electron injection electrode 13 provided on a substrate 11. In this case, the light emitting layer 15 also functions as an electron transport layer.

In FIG. 3, a hole transport layer 14, an emission layer 15, and an electron transport layer 16, which are organic compounds, are formed between a hole injection electrode 12 and an electron injection electrode 13 provided on a substrate 11.

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

Further, the negative electrode of the organic EL element is usually
Although a metal or the like having a low work function is used, such a negative electrode material is easily oxidized and often has high reactivity with other substances. Therefore, when the organic EL structure is exposed to the outside air after the formation of the negative electrode, the negative electrode is immediately oxidized and becomes unusable. Therefore, the organic EL structure must always be handled in a state of being shielded from the outside air, which makes the manufacturing operation extremely difficult.

[0010] Further, after the organic EL element is manufactured and sealed, the negative electrode can be used for an organic EL structure, a glass substrate, or the like.
Alternatively, it reacts with outgas generated from a sealing plate, a sealing adhesive, or the like, and is gradually corroded or deteriorated. As such corrosion or deterioration progresses, the non-light-emitting area of the light-emitting surface expands, lowering the brightness and contrast, and eventually causing pixels that do not emit light, thereby deteriorating the image quality and life of the organic EL element. Was a factor.

Various attempts have been made to form a protective electrode, a sealing film, etc. on the electron injection electrode of the organic EL element, but few of them have been adequately protected. Nothing has been obtained that can respond to major changes.

As a protective layer for the negative electrode, for example, as described in Japanese Patent Application Laid-Open No. 8-1855982,
Studies have been made to form l ₂ O ₃ . However, when attempting to deposit Al ₂ O ₃ by sputtering, the organic layer may be damaged by the generated oxygen plasma. Further, the formed Al ₂ O ₃ film is inferior in heat radiation property, and there is a risk that the organic layer may be damaged by heat generated during high luminance light emission or continuous driving.

In order to solve such a problem, for example,
As described in Japanese Patent Application Laid-Open No. 8-1855982, attempts have been made to use aluminum nitride as a protective film. However, the formed aluminum nitride thin film has a large internal stress and may cause defects such as film peeling.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to realize a long-life organic EL device by suppressing the oxidation and deterioration of the negative electrode and the interface between the negative electrode and the organic layer and the change with time.

[0015]

Means for Solving the Problems That is, the above object is as follows.
This is achieved by the following configuration. (1) a hole injection electrode, a negative electrode, and an organic layer having at least a light emitting layer between these electrodes, a protective layer on the negative electrode, wherein the protective layer comprises aluminum, oxygen, An organic EL device containing nitrogen. (2) The organic EL device according to (1), wherein the protective layer has a thickness of 30 to 500 nm. (3) The organic EL device according to (1) or (2), wherein the protective layer is formed by reactive sputtering. (4) When the average composition of the protective film is expressed as AlO _x N _y , x = 0.1 to 1.0 y = 0.1 to 1.0 The above (1) to (3) Any one of the organic EL devices.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The organic EL device of the present invention has a hole injection electrode, a negative electrode, an organic layer having at least a light emitting layer between these electrodes, and a protective layer on the negative electrode. The protective layer contains aluminum, oxygen, and nitrogen.

By forming the protective layer containing aluminum, oxygen and nitrogen on the negative electrode as described above, damage due to oxygen plasma and the like is suppressed, and the organic layer is not damaged. It is possible to obtain an organic EL device that maintains its performance stably and has a reduced stress in the film, and does not cause defects such as film peeling.

The protective layer contains aluminum, oxygen, and nitrogen. When the average composition of the protective layer is expressed as AlO _x N _y , x = 0.1 to 1.0, particularly 0.3 to 0.8, y
= 0.1 to 1.0, particularly preferably 0.2 to 0.4.

If x is too small, the stress inside the film becomes too large, and if x is too large, the heat dissipation of the film deteriorates.
If y is too small, the heat dissipation of the film deteriorates, and the organic layer is easily damaged. If y is too large, the internal stress of the film becomes too large.

It is considered that the protective film is composed of a mixture of aluminum oxide and aluminum nitride.

The composition of the protective film can be obtained by chemical analysis, X-ray fluorescence analysis, Rutherford backscattering or the like.

The thickness of the protective film is usually from 30 to 50.
0 nm, especially about 50 to 200 nm. If the film thickness is too small, it is difficult to obtain the effect as a protective film. If the film thickness is too large, peeling due to internal stress or the like is likely to occur.

As the method of forming the protective layer, various physical or chemical thin film forming methods such as a sputtering method and an EB vapor deposition method are possible, but the sputtering method is preferable.

When the protective layer is formed by a sputtering method, the pressure of the sputtering gas at the time of sputtering is preferably in the range of 0.1 to 1 Pa. As the sputtering gas, an inert gas used in a normal sputtering apparatus, for example, Ar, Ne, Xe, Kr, or the like can be used. Further, N ₂ may be used if necessary.

As the sputtering method, a high-frequency sputtering method using an RF power source, a DC reactive sputtering method, or the like can be used, but DC reactive sputtering is particularly preferred. The power of the sputtering apparatus is preferably 100 W to DC sputtering.
The range of 3 kW is preferable, and the deposition rate is 0.5 to 10 nm /
min, especially in the range of 1 to 5 nm / min. The substrate temperature during film formation is from room temperature (25 ° C.) to about 150 ° C.

As the reactive gas, NO, NO ₂ , N ₂
O, CO, CO _{2 and the} like can be mentioned. These reactive gases may be used alone or as a mixture of two or more.

As the negative electrode, in combination with an organic electron injection / transport layer or the like, the following electrode can be used as necessary as an electrode having electron injection properties. For example,
K, Li, Na, Mg, La, Ce, Ca, Sr, B
a, Sn, Zn, Zr or other metal element alone, or a binary or ternary alloy system containing them to improve stability, for example, Ag.Mg (Ag: 0.1 to 50 at%), A
l·Li (Li: 0.01 to 14 at%), In · Mg
(Mg: 50-80 at%), Al.Ca (Ca: 0.0
1 to 20 at%).

The thickness of the negative electrode thin film may be a certain thickness or more for sufficiently injecting electrons, and may be 0.1 nm or more, preferably 0.5 nm or more, particularly 1 nm or more. Also,
Although there is no particular upper limit, the film thickness is usually 1 to 50.
It may be about 0 nm.

The negative electrode (electron injection electrode) does not need to have a low work function and an electron injection property in combination with the following high-resistance inorganic electron injection / transport layer and inorganic insulating electron injection / transport layer. Therefore, there is no particular limitation, and ordinary metals can be used. 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 negative electrode thin films may be a certain thickness or more that can provide electrons to the inorganic insulating electron injecting and transporting layer, and may be 50 nm or more, preferably 100 nm or more. Although the upper limit is not particularly limited, the film thickness may be generally about 50 to 500 nm.

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

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.
wt%, more preferably 5 to 12 wt%. Also, IZO
The mixing ratio of ZnO to In ₂ O ₃ is usually 12
About 32% by weight.

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

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

The thickness of the electrode is 50-500 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.

The organic EL device of the present invention may have a high-resistance inorganic electron injection / transport layer instead of the following organic electron injection / transport layer.

As described above, by arranging the high-resistance inorganic electron injecting and transporting layer having an electron conduction path and capable of blocking holes between the light emitting layer and the negative electrode, electrons can be efficiently injected into the light emitting layer. As a result, the luminous efficiency is improved and the driving voltage is reduced.

The high-resistance inorganic electron injecting and transporting layer comprises a first
One or more oxides having a work function of 4 eV or less as a component and selected from an alkali metal element, an alkaline earth metal element, and a lanthanoid element, and one of a metal having a work function of 3 to 5 eV as a second component And more than one species.

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

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

The high resistance inorganic electron injecting and transporting layer preferably has a work function of 4 eV or less as the first component, more preferably 1 eV or less.
４4 eV, preferably Li, Na, K, Rb, C
one or more alkali metal elements selected from s and Fr, or one or more alkaline earth metal elements preferably selected from Mg, Ca and Sr, or 1 preferably selected from La and Ce Contains oxides of any one or more of the lanthanoid elements. Of these, lithium oxide, magnesium oxide, calcium oxide, and cerium oxide are particularly preferred. When these are mixed and used, the mixing ratio is arbitrary. Lithium oxide is 50 mol% in terms of Li ₂ O in these mixtures.
It is preferable that it is contained above.

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

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

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

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

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

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

The thickness of the high-resistance inorganic electron transporting layer is as follows:
Preferably, it is about 0.2 to 30 nm, particularly about 0.2 to 10 nm. If the electron injection layer is thinner or thicker than this, the function as the electron injection layer cannot be sufficiently exhibited.

As a method for producing the above-mentioned inorganic electron transporting layer having a high resistance, various physical or chemical thin film forming methods such as a sputtering method and a vapor deposition method can be considered, but the sputtering method is preferable. Among them, multi-source sputtering for separately sputtering the targets of the first component and the second component is preferable. By using multi-source sputtering, a sputtering method suitable for each target can be used. Further, in the case of one-source sputtering, a mixed target of the first component and the second component may be used.

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

The organic EL device of the present invention may have an inorganic insulating electron injecting and transporting layer as an electron injecting and transporting layer, instead of the organic electron injecting and transporting layer and the high-resistance inorganic electron injecting and transporting layer.

As described above, by providing the inorganic insulating electron injecting and transporting layer made of an inorganic material, an organic EL element having both the advantages of the inorganic material and the organic material can be obtained. That is, the physical properties at the interface between the electrode or the light emitting layer and the electron injection / transport layer are stabilized, and the production becomes easy. In addition, luminance equal to or higher than that of a device having a conventional organic electron injection layer can be obtained, and furthermore, the heat resistance and the weather resistance are high, so that the life is longer than that of the conventional device, and the occurrence of leaks and dark spots is reduced. 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.

The inorganic insulating electron injecting and transporting layer has a function of facilitating the injection of electrons from the negative electrode, a function of stably transporting electrons, and a function of preventing holes. This layer increases and confines holes and electrons injected into the light emitting layer, optimizes a recombination region, and improves luminous efficiency.

That is, the inorganic insulating electron injecting and transporting layer is
By using the main component or the like, there is no need to form an electrode having an electron injection function, and a metal electrode having relatively high stability and good conductivity can be used. Then, the electron injection transport efficiency of the inorganic insulating electron injection transport layer is improved, and the life of the device is extended.

The inorganic insulative electron injecting and transporting layer is mainly composed of lithium oxide (Li ₂ O) and rubidium oxide (Rb
₂ O), potassium oxide (K ₂ O), sodium oxide (Na
₂ O), cesium oxide (Cs ₂ O), strontium oxide (SrO), magnesium oxide (MgO), and calcium oxide (CaO). These may be used alone or as a mixture of two or more, and the mixing ratio when two or more are used is arbitrary. Of these, strontium oxide is most preferred, followed by magnesium oxide, calcium oxide, and then lithium oxide (Li ₂ O).
Then rubidium oxide (Rb ₂ O), followed by potassium oxide (K ₂ O), and sodium oxide (Na ₂ O) is preferred. When these are used as a mixture, it is preferable that strontium oxide is contained in an amount of 40 mol% or more, or lithium oxide and rubidium oxide in a total amount of 40 mol% or more, particularly 50 mol% or more.

The inorganic insulating electron injecting and transporting layer is preferably
Silicon oxide (SiO _Two), And / or
Is germanium oxide (GeO)_Two). They are
Either one may be used, or both may be mixed and used
The mixing ratio at that time is arbitrary.

Each of the above-mentioned oxides usually has a stoichiometric composition. However, the oxide slightly deviates from the stoichiometric composition to form a non-stoichiometric composition.
y).

The inorganic insulating electron injecting and transporting layer of the present invention is preferably such that each of the above-mentioned constituents is Sr
O, MgO, CaO, Li ₂ O, Rb ₂ O, K ₂ O, Na ₂
O, Cs ₂ O, in terms of SiO _2, GeO _2, main component: 80 to 99 mol%, more preferably 90 to 95
mol%, stabilizer: 1-20 mol%, more preferably 5-10
mol%, contained.

The thickness of the inorganic insulating electron injecting and transporting layer is preferably from 0.1 to 2 nm, more preferably from 0.3 to 2 nm.
0.8 nm. If the electron injection layer is thinner or thicker than this, the function as the electron injection layer cannot be sufficiently exhibited.

In the inorganic insulating electron injection / transport layer, H, Ne, Ar, K
r, Xe, etc. may be contained in a total of 5 at% or less.

If the average value of the entire inorganic insulating electron 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 inorganic insulating electron injecting and transporting layer is usually in an amorphous state.

The method of manufacturing the above-mentioned inorganic insulating electron injecting and transporting layer may be in accordance with the above-mentioned high resistance electron injecting and transporting layer.

It is preferable to use an electron injecting and transporting material for the electron injecting and transporting layer made of an organic material.

Specifically, the electron injecting and transporting layer is made of Tris (8
A quinoline derivative such as an organometallic complex having 8-quinolinol or a derivative thereof as a ligand such as 8-quinolinolato) aluminum (Alq3), an oxadiazole derivative, a perylene derivative, a pyridine derivative, a pyrimidine derivative, a quinoxaline derivative, a diphenylquinone derivative; Nitro-substituted fluorene derivatives and the like can be used.

The electron injecting / transporting layer may also serve as a light emitting layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. The electron injection layer may be formed by vapor deposition or the like, similarly to the light emitting layer.

The thickness of the organic electron injecting and transporting layer is not particularly limited and varies depending on the forming method, but it is usually preferably about 5 to 500 nm, particularly preferably 10 to 300 nm.

The light emitting layer is composed of at least one kind or two or more kinds of organic compound thin films involved in the light emitting function, or a laminated film thereof.

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

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

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 preferably 0.01 to 10% by volume, and more preferably 0.1 to 5% by volume. In the case of rubrene, the content is preferably about 0.01 to 20% by volume. 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].

Further, in addition to 8-quinolinol or its derivative, 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
Phenylanthracene derivative described in JP-A-12600 (Japanese Patent Application No. 6-110569) and JP-A-8-1296
No. 9 (Japanese Patent Application No. 6-114456) is also preferable.

The light emitting layer may also serve as an electron injection / transport layer. In such a case, it is preferable to use tris (8-quinolinolato) aluminum or the like. These fluorescent substances may be deposited.

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

In the mixed layer, a carrier hopping conduction path is formed, so that each carrier moves in a material having a favorable polarity, and injection of a carrier 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 and the electron injecting and transporting compound used for the mixed layer may be selected from the hole injecting and transporting compound and the electron injecting and transporting compound described later.

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

As the compound capable of injecting and transporting holes, an amine derivative having strong fluorescence, for example, a triphenyldiamine derivative which is the above-described hole transporting material, a styrylamine derivative, or an amine derivative having an aromatic condensed ring is used. Is preferred.

The mixing ratio in this case depends on the respective carrier mobilities and carrier concentrations. In general, the weight ratio of the compound of the hole injecting and transporting compound / the compound having the electron injecting and transporting function is 1/99 to less. 99/1, more preferably 10/90 to 90/10, particularly preferably 20/80
It is preferable to set it to about 80/20.

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

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

The 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.

When 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 may have an organic hole injection / transport layer as a hole injection / transport layer between the light emitting layer and the hole injection electrode.

The organic hole injecting and transporting layer is described in, for example, JP-A-63-295695 and JP-A-2-19169.
4, JP-A-3-792, JP-A-5-234
681, JP-A-5-239455, JP-A-5-299174, JP-A-7-126225, JP-A-7-126226, JP-A-8-100
Various organic compounds described in JP-A-172, EP0650955A1, and the like can be used. For example, a tetraarylbendicine compound (triaryldiamine or triphenyldiamine: TPD), an aromatic tertiary amine, a hydrazone derivative, a carbazole derivative, a triazole derivative, an imidazole derivative, an oxadiazole derivative having an amino group, polythiophene, etc. . These compounds may be used alone or in combination of two or more. When two or more kinds are used in combination, they may be stacked as separate layers or mixed.

For forming the light emitting layer, the organic hole injecting and transporting layer, and the electron injecting and transporting layer, it is preferable to use a vacuum deposition method since a uniform thin film can be formed. When the vacuum deposition method is used, the amorphous state or the crystal grain size is 0.2
A uniform thin film of less than μm can be obtained. 0.2μ crystal grain size
When m is exceeded, the light emission becomes non-uniform, the driving voltage of the device must be increased, and the injection efficiency of electrons and holes is significantly reduced.

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 comprises:
A high-resistance inorganic hole injection / transport layer may be provided as a hole injection / transport layer between the hole injection electrode and the hole injection electrode.

As described above, by disposing a high-resistance inorganic hole injecting and transporting layer having a hole conduction path and capable of blocking electrons between the light emitting layer and the hole injecting electrode, holes can be efficiently transferred to the light emitting layer. It can be injected, and the luminous efficiency is improved and the driving voltage is reduced.

Preferably, a metal or semimetal oxide such as silicon or germanium is used as a main component of the high-resistance inorganic hole injecting and transporting layer, and a work function of 4.5 is used.
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; Thereby, holes can be efficiently injected from the hole injection layer to the organic layer on the light emitting layer side. Moreover,
Transfer of electrons from the light emitting layer to the hole injection electrode side can be suppressed, and recombination of holes and electrons in the light emitting layer can be efficiently performed. 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 obtain a luminance equal to or higher than that of a device having a conventional organic hole transporting layer, and has a longer life than conventional devices because of high heat resistance and weather resistance, and has a leak and darkness. 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 resistivity of the high-resistance inorganic hole injecting and transporting layer is preferably 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 component, 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 is additionally used as an impurity.
r, Kr, Xe and the like may be contained in a total of 5 at% or less.

If the composition is such a composition as the average value of the whole high-resistance inorganic hole injecting and transporting layer, 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 0.2 to 100 nm, more preferably 0.2 to 30 nm, and particularly preferably about 0.2 to 10 nm.
Even if the high-resistance inorganic hole injecting and transporting layer is thinner or thicker, the function as the hole transporting layer cannot be sufficiently exhibited.

As a method for 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 film forming conditions and the like are the same as those in the case of the inorganic electron injecting and transporting layer.

Further, in order to prevent deterioration of the organic layer and the electrodes of the device, it is preferable to seal the device 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.

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

The 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. The spacer is usually a granular material having a uniform particle size, but the shape is not particularly limited, and may be various shapes as long as it does not hinder the function as the spacer. As the size, the diameter in terms of a circle is 1 to 20 μm, more preferably 1 to 10 μm, and especially 2 to 20 μm.
8 μm is preferred. Those having such a diameter have a grain length of 10
It is preferably about 0 μm or less, and the lower limit is not particularly limited, but is usually about the same as or larger than the diameter.

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

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

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

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

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

The 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.

For 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.

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

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

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

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

The organic EL device of the present invention is, for example, as shown in FIG. 1, a substrate 1 / a hole injection electrode 2 / a hole injection / transport layer 3 / a light emitting layer 4 / an electron injection / transport layer 5 / a negative electrode (electron injection electrode). 6 / protective layer 7 may be sequentially laminated. In FIG. 1, the hole injection electrode 2 and the negative electrode 6
Is connected to a drive power source E.

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

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

[0129]

<Example 1> A 7059 substrate (trade name, manufactured by Corning Incorporated) as a glass substrate was scrub-cleaned using a neutral detergent.

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

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

4,4 ', 4 "-tris (-N- (3-methylphenyl) -N-phenylamino) triphenylamine (m-MTDATA) was deposited at a deposition rate of 0.2 nm / sec to a thickness of 40 nm. Evaporation was performed to form a hole injection layer.

Next, N, N, N ', N'-tetrakis (m-biphenyl) -1,1'-biphenyl-4,4'
-Diamine (TPD) was deposited at a deposition rate of 0.2 nm / sec to a thickness of 40 nm to form a hole transport layer.

Further, N, N, N
N ', N'-tetrakis (m-biphenyl) -1,1'
-Biphenyl-4,4'-diamine (TPD), tris (8-quinolinolato) aluminum (Alq3),
Rubrene at an overall deposition rate of 0.2 nm / sec.
It was deposited to a thickness of nm to form a light emitting layer. TPD: Alq3 =
Rubulene was doped at 5% by volume with respect to the mixture at a ratio of 1: 1 (weight ratio).

Further, the tris (8-
(Quinolinolato) aluminum (Alq3) was deposited at a deposition rate of 0.2 nm / sec to a thickness of 40 nm to form an electron injection transport layer.

Next, while maintaining the reduced pressure, AlLi (L
i: 7 at%) to a thickness of 1 nm, followed by Al
Evaporation was performed to a thickness of 0 nm to form a negative electrode for an electron injection electrode and an auxiliary electrode.

Next, the film was transferred to a sputtering apparatus, and a protective film was formed to a thickness of 100 nm by DC reactive sputtering using Al as a target. The deposition conditions at this time were: input power: 1 kW, sputtering gas: Ar, reactive gas: N ₂ O, 5 SCCM, and pressure: 0.3 Pa.

Finally, the resultant was sealed with glass to obtain an organic EL device. As comparative samples, a comparative sample 1 in which a protective film was not formed, a comparative sample 2 in which Al ₂ O ₃ was formed with a similar thickness, and a comparative sample 3 in which AlN was formed with a similar thickness were produced.

Each of the obtained organic EL devices was heated at 115 ° C. for 1 hour.
After storage for 00 hours, the substrate was driven in air at a constant current density of 10 mA / cm ² , and the area of the luminescent pixel during initial driving and after storage was compared to determine the shrinkage ratio.

As a result, the shrink ratio of the invention sample was 5% or less, the shrink ratio of the comparative sample 1 was 80% or more, and the shrink ratio of the comparative sample 3 was 5% or less.
0% or more. For Comparative Sample 2,
Since the introduction of O ₂ at the time of film formation, emission luminance can not be obtained organic layer is damaged. Further, Comparative Sample 3
The occurrence of cracks, which is considered to be caused by stress in the protective film, was visually confirmed.

[0141]

As described above, according to the present invention, it is possible to realize a long-life organic EL device by suppressing the oxidation and deterioration of the negative electrode and the interface between the negative electrode and the organic layer and the change with time.

[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 showing a configuration example of a conventional organic EL element.

FIG. 3 is a schematic sectional view showing another configuration example of a conventional organic EL element.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 substrate 2 hole injection electrode 3 organic hole injection layer 4 inorganic insulating hole transport layer 5 light emitting layer 6 electron injection and transport layer 7 negative electrode (electron injection electrode) 11 substrate 12 hole injection electrode 13 electron injection electrode 14 hole transport layer 15 light emission Layer 16 Electron transport layer

Claims (4)

[Claims] 1. A semiconductor device comprising: a hole injection electrode, a negative electrode, and an organic layer having at least a light-emitting layer between these electrodes; and a protective layer on the negative electrode. And an organic EL device containing nitrogen. 2. The organic EL device according to claim 1, wherein said protective layer has a thickness of 30 to 500 nm. 3. The organic EL device according to claim 1, wherein said protective layer is formed by reactive sputtering. 4. The protective film has an average composition of AlO _x
The organic EL device according to claim 1, wherein when expressed as N _y , x = 0.1 to 1.0 and y = 0.1 to 1.0.