JPH11260546A - Organic el element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode structure of an organic EL element which does not cause display quality deterioration such as expansion of non- electroluminescent regions by stably protecting an electron injection electrode layer and suppressing alteration with the lapse of time. SOLUTION: This organic EL element comprises a hole injection electrode 2, an electron injection electrode 4, and one or more types of organic layers 3 formed between these electrodes and further comprises a wiring electrode 5 and a buffer layer 6 and a sealing layer 7 successively formed on the electron injection electrode 4. The metal material used for forming the buffer layer 6 is a metal easier to be oxidized than that of the sealing layer 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an information display panel,
The present invention relates to an organic EL device which is used for home electric appliances, automobiles, and electric components for motorcycles, such as an instrument panel for an automobile, a display for displaying a moving image and a still image, and is configured using an organic compound.

[0002]

2. Description of the Related Art In recent years, organic EL devices have been actively studied,
It is being put to practical use. In this method, a hole transport material such as triphenyldiamine (TPD) is formed into a thin film on a transparent electrode (hole injection electrode) such as tin-doped indium oxide (ITO) by vapor deposition, and then an aluminum quinolinol complex (A
1q3) as a light emitting layer, and a metal electrode such as Mg having a small work function (electron injection electrode)
This element has a basic structure and has a very high luminance of several hundreds to several tens of thousands cd / m ² at a voltage of about 10 V, and thus has attracted attention as a display for home electric appliances, automobiles, motorcycle electric components and the like.

[0003] The organic EL element has a hole injection electrode layer 2 of ITO or the like on a substrate 1 as shown in FIG.
Further, an organic layer 3 such as a hole injection transport layer, a light emitting layer, and an electron injection transport layer is provided thereon. Then, an electron injection electrode layer 4 is provided on the organic layer 2 and, if necessary, a wiring electrode layer or a protective layer 5 is provided. Further, sealing is performed by fixing a sealing plate 9 made of glass or the like with a sealing adhesive 8 or the like. The actual organic EL element has a thickness of several 100 nm to several tens μm.
The thin film structure has a size of about m and is formed in a predetermined size and shape depending on the intended use, such as a dot matrix or a segment structure.

When manufacturing such an organic EL device,
First, after forming a hole injection electrode such as ITO, an auxiliary electrode and the like as necessary, an organic layer giving a desired emission luminance and emission spectrum is formed, and further, an electron injection electrode is formed. Then, if necessary, a wiring electrode layer or a protective layer is formed.

[0005] By the way, a metal having a low work function is usually used for the electron injection electrode. Such a metal is easily oxidized and has high reactivity with other substances in many cases. For this reason, when the organic EL structure after the formation of the electron injection electrode is exposed to the outside air in the manufacturing process of the organic EL element, the electron injection 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.

The electron injection electrode reacts with an outgas generated from an organic EL structure, a glass substrate, a sealing plate, a sealing adhesive or the like even after the organic EL element is manufactured and sealed. It is corroded and deteriorated little by little. 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, and the like on the electron injection electrode of the organic EL element, but few of them have been sufficiently protected. Nothing has been obtained that can respond to major changes.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to stably protect an electron injecting electrode layer, suppress a change with time,
An object of the present invention is to provide an electrode structure of an organic EL element that does not cause a decrease in display quality such as expansion of a non-light emitting region.

[0009]

The above object is achieved by the following constitution. (1) An organic EL device having a hole injection electrode, an electron injection electrode, and at least one organic layer between these electrodes, wherein a wiring electrode, a buffer layer, and a sealing layer are further provided on the electron injection electrode. An organic EL, wherein a metal layer constituting the buffer layer is a metal which is more easily oxidized than the sealing layer.
element. (2) The organic EL device according to (1), wherein the buffer layer contains a material for constituting an electron injection electrode. (3) The organic EL device according to (1) or (2), wherein the sealing layer contains aluminum.

[0010]

DETAILED DESCRIPTION OF THE INVENTION An electrode of an organic EL device according to the present invention, comprising a hole injection electrode, an electron injection electrode, and one or more organic layers between these electrodes, wherein the electron injection electrode Further, a wiring electrode, a buffer layer, and a sealing layer are sequentially formed thereon, and the constituent metal material of the buffer layer is a metal that is more easily oxidized than the sealing layer.

By forming a buffer layer and a sealing layer made of a metal which is more easily oxidized on a wiring electrode formed on the electron injection electrode, outgas and the like generated after sealing can be reduced by the buffer. It is absorbed by the layer and can protect the electron injection electrode.

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. Note that the electron injection electrode can be formed by an evaporation method or a sputtering method.

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. A wiring electrode is further provided on the electron injection electrode.

As the constituent metal material of the wiring electrode layer, for example, Al, Al and transition metal, especially Sc, Nb, Z
r, Hf, Nd, Ta, Cu, Si, Cr, Mo, M
n, Ni, Pd, Pt, W, etc., preferably their total is 10 at% or less, more preferably 5 at% or less, especially 2 at% or less.
An aluminum-based alloy which may contain at% or less can be preferably mentioned. Aluminum has a low resistance, and when used as a wiring electrode layer, a good effect can be obtained.

The thickness of the wiring 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 prevent entry of moisture, oxygen or an organic solvent. A range from 100 to 500 nm is preferred. If the wiring electrode layer is too thin, the effect cannot be obtained, and the step coverage of the wiring electrode layer will be low, and the connection with the terminal electrode will not be sufficient. On the other hand, if the wiring electrode layer is too thick, the stress on the wiring electrode layer will increase, and the growth rate of dark spots will increase.

The total thickness of the electron injection electrode and the wiring electrode is not particularly limited, but is usually 100 to 10
What is necessary is just to make it about 00 nm.

A buffer layer is provided on the wiring electrode layer.
As a constituent metal material of the buffer layer, a material having high reactivity with water or gas in the atmosphere or capable of adsorbing them is preferable. Further, it is a material that is more easily oxidized than a constituent metal material of a sealing layer described later. The metal material of such a buffer layer is not particularly limited, but is preferably the same as the constituent material of the electron injection electrode.

The thickness of the buffer layer is such that even if moisture, oxygen, an organic solvent, or other reactive gas enters, it is absorbed by the buffer layer and penetrates into a lower layer (such as an electron injection electrode). In order to prevent this, the thickness may be set to a certain value or more, preferably 20 nm or more, and more preferably 20 to 200 nm. If the buffer layer is too thin, the effect cannot be obtained. If the buffer layer is too thick, the stress of the buffer layer increases, and the growth rate of dark spots increases.

A sealing layer is provided on the buffer layer. The metal material forming the sealing layer needs to be a material that is less oxidizable than the material of the buffer layer. Specifically, for the metal material of the buffer layer, the oxidation-reduction curve of the metal material of the sealing layer (for example, introduced by Ellingham and Richardson
It was developed by Jeffs. ) Is the higher ranking relationship.

The constituent metal of such a sealing layer is not particularly limited, but Al, Ti, Ni and alloys of these metals are preferable, and Al is particularly preferable. Even if Al is oxidized to some extent, the oxidation does not proceed from there on, and the sealing effect is high.

The thickness of the sealing layer may be a certain thickness or more, preferably 5 nm or more, in order to prevent the entry of moisture, oxygen, an organic solvent, other reactive or corrosive gas and the like. Preferably 5-100 nm, especially 10-1
A range of 00 nm is preferred. If the sealing layer is too thin, the effect cannot be obtained. If the sealing layer is too thick, the stress of the sealing layer increases and the growth rate of dark spots increases.

The electron injection electrode, the wiring electrode layer, the buffer layer, and the sealing layer can be formed by a vapor deposition method, but it is preferable to use a sputtering method. When each of the above layers is formed by a sputtering method, the formed electrode layer and the like become a dense film, the penetration of moisture into the film is very small as compared with a coarse vapor deposition film, and the chemical stability is high. And a long-life electrode structure can be obtained.

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. When a TiN film or the like is formed as a sealing layer, the film can be formed by using reactive sputtering. In this reactive sputtering, in addition to the above-described inert gas, a reaction of N ₂ , NH _3, or the like is performed. Neutral gas can be used.

As a sputtering method, a film may be formed by using a suitable sputtering method from among 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 film formation rate is 5 to 100 nm / min, especially 10 to 50 nm.
The range of nm / min is preferred.

When the above layers are formed by a vapor deposition method, the conditions for vacuum vapor deposition are not particularly limited, but it is preferable that the degree of vacuum is 10 ^-4 Pa or less and the vapor deposition rate is about 0.01 to 1 nm / sec. Further, it is preferable to form each layer continuously in a vacuum. If they are formed continuously in a vacuum, impurities can be prevented from adsorbing at the interface between the layers, so that high characteristics can be obtained.

The organic EL device of the present invention can be applied to displays using various organic EL devices, such as a matrix type display and a segment type display.

Next, the organic EL structure constituting the organic EL device of the present invention will be described.

The organic EL structure used in the present invention is, for example, as shown in FIG. 1, a hole injecting electrode 2 such as ITO on a substrate 1 and one kind of a hole injecting and transporting layer, a light emitting layer, an electron injecting and transporting layer and the like. It has an organic layer 3 having the above and an electron injection electrode 4. Further, a wiring electrode layer 5, a buffer layer 6, and
And a sealing layer 7. Although omitted in this example, if necessary, a sealing plate 9 as shown in FIG. 2 is provided with a sealing adhesive or the like.

Since the hole injection electrode is generally configured to extract light emitted from the substrate side, a transparent or translucent electrode is preferable. Examples of the transparent electrode include ITO (tin-doped indium oxide), IZO (zinc-doped indium oxide), ZnO, SnO ₂ , In ₂ O _{3, and the} like.
ZO (zinc-doped indium oxide) is preferred. ITO
Usually contains In ₂ O ₃ and SnO in a stoichiometric composition, but the O amount may be slightly deviated from this. ITO
Usually has In ₂ O ₃ and SnO ₂ in a stoichiometric composition, but the oxygen amount may be slightly deviated from this. I
The mixing ratio of SnO ₂ to n ₂ O ₃ is 1 to 20 wt%,
More preferably, the content is 5 to 12% by weight. In addition, IZO
The mixing ratio of ZnO ₂ to n ₂ O ₃ is usually 12 to 3
It is about 2% by weight.

The thickness of the hole injecting electrode may be a certain thickness or more that can sufficiently inject holes, and is preferably 5 or more.
The range is preferably from 0 to 500 nm, more preferably from 50 to 300 nm. The upper limit is not particularly limited, but if the thickness is too large, there is a fear of peeling or the like. If the thickness is too small, there is a problem in the film strength at the time of manufacturing, the hole transport ability, and the resistance value.

The hole injecting electrode layer can be formed by a vapor deposition method or the like, but is preferably formed by a sputtering method, in particular, a DC sputtering method or a pulse sputtering method.

After electrode formation, in addition to the sealing layer, 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 . The sealing gas has a water content of 100 ppm.
Or less, more preferably 10 ppm or less, particularly 1 ppm
The following is preferred. Although there is no particular lower limit for the water content, it is usually about 0.1 ppm.

The material of the sealing plate is preferably a flat plate, and may be a transparent or translucent material such as glass, quartz, resin, etc., and glass is particularly preferred. As such a glass material, an alkali glass is preferable, and in addition, a glass composition such as soda-lime glass, lead-alkali glass, borosilicate glass, aluminosilicate glass, and silica glass is also preferable. As the plate making method, a roll-out method, a download method, a fusion method, a float method, or the like is 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 sealing plate may be maintained at a desired height by adjusting the height using a spacer. Examples of the material of the spacer include resin beads, silica beads, glass beads, and glass fibers, and glass beads are particularly preferable. The spacer is usually a granular material having a uniform particle size, but the shape is not particularly limited, and may be various shapes as long as it does not hinder the function as the spacer. As the size, the diameter in terms of a circle is 1 to 20 μm, more preferably 1 to 10 μm, and especially 2 to 20 μm.
8 μm is preferred. Those having such a diameter have a grain length of 10
It is preferably about 0 μm or less, and the lower limit is not particularly limited, but is usually about 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 previously mixed into the sealing adhesive or may be mixed during 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 substrate material 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 is used. 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.

Next, the organic layer provided in the organic EL device will be described. 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. In the light emitting layer,
It is preferable to use a relatively electronically neutral compound.

The hole injecting and transporting layer has a function of facilitating the injection of holes from the hole injecting electrode, a function of stably transporting holes, and a function of preventing electrons.
The electron injection / transport 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. 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 light emitting layer, the thickness of the hole injecting and transporting layer, and the thickness of the electron injecting and transporting layer are not particularly limited and vary depending on the forming method.
It is preferable that the thickness be in the range of 10 to 300 nm.

The thickness of the hole injecting and transporting layer and the thickness of the electron injecting and transporting layer depend on the design of the recombination and 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 500 nm for the transport layer.
It is about. Such a film thickness is the same when two injection / transport layers are provided.

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
-Quinolinolato) quinoline derivatives such as metal complex dyes having 8-quinolinol or a derivative thereof as a ligand such as aluminum, tetraphenylbutadiene, anthracene, perylene, coronene, and 12-phthaloperinone derivatives. Further, phenylanthracene derivatives disclosed in Japanese Patent Application No. 6-110569, and Japanese Patent Application No. 6-11445.
No. 6 tetraarylethene derivative or 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.

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

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

Other host substances include Japanese Patent Application No.
Also preferred are phenylanthracene derivatives described in -110569 and tetraarylethene derivatives described in Japanese Patent Application No. 6-114456.

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 weight, more preferably 0.1 to 15% by weight.

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 less likely to occur, so that the organic compound is less likely to be damaged. This has the advantage that the element life is extended. Further, by including the above-described dopant in such a mixed layer, the emission wavelength characteristics of the mixed layer itself can be changed, the emission wavelength can be shifted to a longer wavelength, and the emission intensity is increased, The stability of the device can be improved.

The hole injecting and transporting compound and the electron injecting and transporting compound used in the mixed layer may be selected from the compounds for the hole injecting and transporting layer and the compounds for the electron injecting and transporting layer, respectively, which will be described later. Among them, compounds for the hole injection transport layer include amine derivatives having strong fluorescence,
For example, it is preferable to use a triphenyldiamine derivative which is a hole transport material, a styrylamine derivative, or an amine derivative having an aromatic condensed ring.

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

As the compound for the hole injecting and transporting layer, an amine derivative having strong fluorescence, for example, a triphenyldiamine derivative as 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 having a hole injecting / transporting compound / the compound having an electron injecting / transporting function is from 1/99 to more. 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 of forming the mixed layer, co-evaporation in which evaporation is performed from different evaporation sources is preferable. However, when the vapor pressures (evaporation temperatures) are approximately the same or very close, they are mixed in advance in the same evaporation board. Alternatively, it can be deposited. In the mixed layer, it is preferable that the compounds are uniformly mixed, but in some cases, the compounds may exist in an island shape. The light-emitting layer is generally formed to a predetermined thickness by vapor-depositing an organic fluorescent substance or by dispersing and coating the resin in a resin binder.

The hole injecting and transporting 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.

When the hole injecting and transporting layer is divided into a hole injecting layer and a hole transporting layer, a preferred combination can be selected from the compounds for the hole injecting and transporting 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 good thin film property on the surface of the positive electrode. Such a stacking order is the same when two or more hole injection transport layers are provided. 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, when making the device,
Since thin film of about 1 to 10 nm can be made uniform and pinhole-free because of the use of vapor deposition, even if a compound having a small ionization potential in the hole injection layer and having absorption in the visible region is used, light emission can be achieved. It is possible to prevent a decrease in efficiency due to a color tone change or re-absorption. The hole injecting and transporting layer can be formed by vapor deposition of the above compound in the same manner as the light emitting layer and the like.

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 is provided in the electron injection transport layer provided as needed. 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 preferred 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.

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.

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 absorption is strong in an EL emission wavelength region. In practice, laser dyes and the like are suitable, and rhodamine compounds, perylene compounds, cyanine compounds, phthalocyanine compounds (including subphthalocyanines, etc.) 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 that does not quench the fluorescence may be basically 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. As the light absorbing material, a material that does not quench the fluorescence of the fluorescent material may be selected.

In forming the hole injection transport layer, the light emitting layer and the electron injection transport layer, a uniform thin film can be formed.
It is preferable to use a vacuum deposition method. When vacuum deposition is used, the amorphous state or the crystal grain size is 0.1 μm
The following homogeneous thin film is obtained. If the crystal grain size exceeds 0.1 μm, the light emission becomes non-uniform, the driving voltage of the device must be increased, and the charge injection efficiency 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.

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

The organic EL element is driven by direct current or pulse, and the applied voltage is usually about 2 to 20 V.

[0076]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. Example 1 An ITO transparent electrode (hole injection electrode) was formed on a glass substrate to a thickness of 100 nm by a sputtering method. The obtained ITO thin film is patterned and etched by a photolithography technique, and further, a wiring structure film such as an auxiliary electrode is formed. Finally, a 100 μm × 100 μm
A hole injection electrode layer constituting a pattern of (pixel) was formed.

After the surface of the substrate on which the ITO electrode layer and the like had been formed was washed with UV / O _3, it was fixed to a substrate holder of a vacuum evaporation apparatus, and the pressure in the tank was reduced to 1 × 10 ⁻⁴ Pa or less. 4,
4 ', 4 "-tris (-N- (3-methylphenyl)-
N-phenylamino) triphenylamine (hereinafter, m-
MTDATA) was deposited at a deposition rate of 0.2 nm / sec. To a thickness of 40 nm to form a hole injection layer, and then N, N′-diphenyl-N, N′-m-tolyl-4 while maintaining the reduced pressure. , 4'-Diamino-1,1'-biphenyl (hereinafter, referred to as
TPD) was deposited at a deposition rate of 0.2 nm / sec. To a thickness of 35 nm to form a hole transport layer. Further, while maintaining the reduced pressure, tris (8-quinolinolato) aluminum (hereinafter, referred to as tris (8-quinolinolato) aluminum)
Alq3) was deposited at a deposition rate of 0.2 nm / sec. To a thickness of 50 nm to form an electron injecting / transporting / light emitting layer.

Then, while maintaining the reduced pressure, the EL element structure substrate was transferred from the vacuum evaporation apparatus to the sputtering apparatus, and the AlLi electron injection electrode (Li concentration: 6 at%) was formed to a thickness of 50 nm at a sputtering pressure of 1.0 Pa. A film was formed. At that time, Ar was used as a sputtering gas, the input power was 100 W, the size of the target was 4 inches in diameter, and the distance between the substrate and the target was 9
0 mm. Further, while maintaining the reduced pressure, the EL element substrate was transferred to another sputtering apparatus, and the sputtering was performed at a sputtering pressure of 0.3 Pa by a DC sputtering method using an Al target.
A wiring electrode was formed to a thickness of 200 nm. At this time, Ar was used as a sputtering gas, 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 9
0 mm.

While maintaining the reduced pressure, the wafer was transferred to a sputtering apparatus on which an electron injection electrode was formed, and an AlLi buffer layer (Li concentration: 6 at%) was formed to a thickness of 50 nm in the same manner as the electron injection electrode. Next, while maintaining the reduced pressure, the EL element structure substrate was transferred to another sputtering apparatus, and a sealing layer was formed to a thickness of 200 nm in the same manner as the Al wiring electrode.

Finally, a glass sealing plate is attached, and organic E
An L element was used. A comparative sample without a buffer layer and a sealing layer was obtained in the same manner.

Each of the obtained organic EL devices was continuously driven at a constant current density of 10 mA / cm ² under an acceleration condition of 85 ° C. for 100 hours by applying a DC voltage in the air. Observing the light-emitting surface of each pixel and measuring the size of the non-light-emitting portion in the pixel, the comparative sample showed that the non-light-emitting portion grew from the periphery of the pixel toward the center over an average width of 5 μm. On the other hand, in the sample of the present invention, an extremely excellent result of 1 μm or less was obtained on average. This is considered to be the result of protecting the electron injection electrode by absorbing or blocking gas or moisture generated in the space where the buffer layer is sealed.

<Example 2> In Example 1, the material of the buffer layer was changed from AlLi to K, Li, Na, Mg, La, and C.
e, Ca, Sr, Ba, Ag, In, Sn, Zn, Zr
Either a single substance or an alloy of these and Al was evaluated by the same method as in Example 1, and almost the same results were obtained. The same applies when the metal used for the sealing layer is Ti or Ni.

[0083]

As described above, according to the present invention, the organic EL device which stably protects the electron injection electrode layer, suppresses the change with time, and does not deteriorate the display quality such as enlargement of the non-light emitting region.
An electrode structure of the device can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an organic EL device of the present invention.

FIG. 2 is a plan view schematically showing a conventional organic EL element.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 hole injection electrode 3 organic layer 4 electron injection electrode layer 5 wiring electrode 6 buffer layer 7 sealing layer

Claims (3)

[Claims] 1. An organic EL device having a hole injection electrode, an electron injection electrode, and at least one organic layer between these electrodes, further comprising a wiring electrode, a buffer layer, And a sealing layer are sequentially formed, and the constituent metal material of the buffer layer is a metal that is more easily oxidized than the sealing layer. 2. The organic EL device according to claim 1, wherein said buffer layer contains a material for forming an electron injection electrode. 3. The organic EL device according to claim 1, wherein the sealing layer contains aluminum.