JP2003031360A - Organic el element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element of high yield and high quality prevented from partial short circuit between electrodes or an approximate short circuit state and free from erroneous light emission and display unevenness caused by the generation of a leak current. SOLUTION: This organic EL element has a first electrode 2 and a second electrode 10 in order on a substrate 1 and has three or more organic layers 3, 4, 5, 6, 7 and 8 at least one layer of which has a light emitting function, between the electrodes 2, 10. At least two or more organic layers 3, 4 out of the organic layers 3, 4, 5, 6, 7 and 8 are structured to embed foreign matters, and the glass transition point of the organic layer 3 in contact with the first electrode 2 out of two or more organic layers 3, 4 is higher than that of the other organic layer 4 embedding the foreign matter.

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) element and an organic EL display panel using the organic EL element. More specifically, the present invention prevents element leakage caused by foreign matter during manufacture. The present invention relates to an organic EL display having high productivity, improved durability and reliability, and an organic EL display panel using the same.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for flat panel displays from the viewpoint of occupying a small volume, and a device using an electroluminescence element (hereinafter abbreviated as EL element) which is light in weight and does not require a backlight is attracting attention. Has been done.

EL elements include organic EL elements and inorganic EL elements. Among them, the organic EL element has an advantage that it can be driven at a low voltage of about 20 V or less, unlike the inorganic EL element.

The organic EL device is a device in which electrons and holes (holes) are injected from the outside, and the emission center is excited by the recombination energy of the electrons, and in general, it is more positive than tin-doped indium oxide (ITO). A hole transport layer containing triphenyldiamine or the like formed on a hole (hole) injection electrode, and an organic light emitting layer containing a fluorescent substance such as aluminum quinolinol complex (Alq3) stacked on the hole transport layer. , And a metal electrode having a low work function (electron injection electrode) such as magnesium, as a basic structure.

When manufacturing a display using such an organic EL element, how to reduce the defective rate is an important issue in the mass production process. That is, the organic layers are non-uniformly stacked in the manufacturing process, the organic layers are damaged when the functional thin films such as the electron injection electrode are stacked, conversely impurities are mixed in the electron injection electrode itself, or oxidation is caused. As a result, defects such as uneven brightness and dot defects and quality variations may occur.

In particular, the occurrence of current leakage is an important problem, and if there is a current (leakage current) in the opposite direction, crosstalk, uneven brightness, dot defects, etc. occur, which is fatal for mass production products. It becomes defective.

In the conventional organic EL device, the thickness of the organic layer is 1
The thickness is about 00 to 200 nm, and if such a thin film contains fine foreign matter, leakage easily occurs by applying a drive voltage up to about 20V.

As a method for suppressing the occurrence of defective leakage,
For example, Japanese Unexamined Patent Publication No. 2000-91067 or Japanese Patent Application No. 11-236697 discloses a method of performing a process of embedding a foreign substance that may cause a leak due to thermal melting of an organic EL material layer. ing.

However, when the organic EL material is melted by heat, due to the problem of wettability between the organic material and ITO, ITO and organic E
The interface with the L material becomes unstable, and as a result, the produced organic EL display suffers from poor display quality, resulting in a decrease in reliability.

In addition, there is a problem in that the phenomenon in which the organic material is thermally oxidized is inevitable due to the thermal melting, and the driving voltage of the organic EL element increases.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to suppress the element leakage, stabilize the interface between the electrode and the organic EL layer to improve the reliability, and suppress the increase of the driving voltage. It is to provide an EL display.

[0012]

The above object can be achieved by the following constitution of the present invention. (1) A first electrode and a second electrode are sequentially provided on a substrate, and at least one layer has three or more organic layers having a light emitting function between these electrodes, and at least two of the organic layers are provided.
One or more organic layers have a structure in which foreign matter is embedded, and among the two or more organic layers, the glass transition point of the organic layer in contact with the first electrode embeds other foreign matter. An organic EL device whose glass transition temperature is higher than that of the organic layer. (2) Organic E of the above (1), in which the work function of an organic layer in which a foreign substance is embedded is equal to or smaller than the work function of an organic layer in contact with the first electrode, other than the organic layer in contact with the first electrode.
L element. (3) An organic EL element in which the total film thickness of the organic layer in which the foreign matter is embedded is 1:10 to 1: 1 as a ratio to the total film thickness of the other organic layers. (4) A first electrode and a second electrode are sequentially provided on a substrate, and at least one layer has three or more organic layers having a light emitting function between these electrodes, and at least two of the organic layers are provided.
A layer or more organic layers having a structure in which foreign matter is embedded, and the work function of the organic layer in which foreign matter is embedded is in contact with the first electrode, other than the organic layer in contact with the first electrode. An organic EL device with a work function equal to or smaller than that. (5) A first electrode and a second electrode are sequentially provided on a substrate, and at least one layer has three or more organic layers having a light emitting function between these electrodes, and at least two of the organic layers are provided.
The organic layer of at least one layer has a structure in which foreign matter is embedded, and the total thickness of the organic layer in which this foreign matter is embedded is 1:10 to 1: 1 in terms of the ratio to the total thickness of the other organic layers. Organic EL that is 1
element. (6) A manufacturing method for obtaining the organic EL device according to any one of (1) to (5), wherein the organic layer in which the foreign matter is embedded is:
A method for producing an organic EL element, which is processed by a heat melting step of heating and melting at a temperature of a glass transition point or higher and a melting point or lower. (7) The method for manufacturing an organic EL device according to (6), wherein the heat melting step is performed in an atmosphere having an oxygen concentration of less than 1%. (8) The organic EL of (6) or (7) above, wherein the heat-melting step is performed with the film formation surface of the substrate facing downward.
Device manufacturing method.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The organic EL device of the present invention has a first electrode and a second electrode in sequence on a substrate, and at least one layer between these electrodes has three or more layers having a light emitting function. An organic layer, and at least two or more organic layers of the organic layer have a structure in which foreign matter is embedded. Of the two or more organic layers, one of the organic layers in contact with the first electrode The glass transition point is higher than the glass transition point of the organic layer in which other foreign matter is embedded.

Further, the work function of the organic layer other than the organic layer in contact with the first electrode, in which the foreign matter is embedded, is equal to or smaller than the work function of the organic layer in contact with the first electrode.

Further, the ratio of the total thickness of the organic layer in which the foreign matter is embedded to the total thickness of the other organic layers is 1:10.
~ 1: 1.

Here, the first electrode is an electrode formed as a lower electrode on the substrate. Usually, the first electrode is an anode side, that is, a transparent electrode such as ITO having a hole injecting property. To be On the other hand, the second electrode is an upper electrode formed on the organic layer, and a cathode, that is, an electron injection electrode having an electron injection property or a cathode combined with an electron injection layer is usually used. In the case of so-called reverse stacking, the first electrode may be set on the cathode side and the second electrode may be set on the anode side.

In the present invention, at least one of the laminated organic layers has a light emitting function, and two or more layers have a structure in which foreign matter is embedded. One of the organic layers in which the foreign matter is embedded is located in contact with the first electrode, and the other layers are formed closer to the second electrode.

As the organic layer for embedding a foreign substance, the first electrode is usually a hole injecting electrode, so an organic layer having a hole injecting and transporting property is used. However, when the first electrode is set on the cathode side, the organic layer naturally has an electron injecting and transporting property. Further, it may have both hole injecting and transporting property and electron injecting and transporting property, or may have a light emitting function.

In the following description, as a general mode, a case where the first electrode is a hole injecting electrode and the organic layer in contact with the first electrode has a hole injecting and transporting property will be described as an example.

The hole injecting electrode material is preferably one capable of injecting holes efficiently into the hole injecting 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
It is preferable that any one of O) is the main composition. These oxides may deviate somewhat from their stoichiometric composition.

The electrode on the side from which light is extracted has an emission wavelength band,
Generally, the light transmittance for light with a wavelength of 400 to 700 nm is 5
It is preferably 0% or more, more preferably 80% or more, and particularly preferably 90% or more. If the transmittance is too low, the light emission itself from the light emitting layer is attenuated, and it becomes difficult to obtain the brightness required for the light emitting element.

The thickness of the electrode is 50 to 500 nm, especially 50.
The range of up to 300 nm is preferred. Further, the upper limit is not particularly limited, but if it is too thick, there is a concern that the transmittance may decrease or peeling may occur. If the thickness is too thin, a sufficient effect cannot be obtained, and there is a problem in film strength during production.

Here, the organic layer in contact with the first electrode is referred to as a hole injection layer a, and the other organic layer for embedding foreign matter is referred to as a hole injection layer b. The hole injection layer b for embedding the foreign matter
May have a plurality of layers such as b1, b2, b3 ....

At this time, it is important that the material selected for the hole injection layer a does not have a glass transition point Tg or is higher than the Tg of the hole injection layer b. When the injection treatment of the injection layer b is performed, it is sufficient that the hole injection layer a is separated from the injection layer b so as not to melt. Specifically, it is preferably 20 ° C. or higher.

Furthermore, the heat melting of the organic material is more than 4 than Tg.
Since it is known to start at a temperature as high as 0 ° C ("Rheology for chemists", Publisher: Kagaku Dojin, author: Shigeharu Onoki), the difference in Tg is more preferably 40 ° C. That is all.

The reason for using two or more layers having different Tg is as follows.
This is because the fluidity of two layers having different Tg's or more is more effective than that of one layer, and as a result, the foreign matter embedding ability is increased and the element leakage is reduced.

Examples of the material used for the hole injecting layer a include aromatic tertiary amines, but not limited to these, a material having a good hole injecting property can be applied, for example, tetraaryl. Examples thereof include benzidine compounds, hydrazone derivatives, carbazole derivatives, triazole derivatives, imidazole derivatives, oxadiazole derivatives, polythiophene and polyaniline derivatives, and silane derivatives such as hexamethyldisilazane.

The material used for the hole injection layer b is the same as the material used for the hole injection layer a, but the material needs to have fluidity at room temperature or heat treatment.

Regarding the work function relationship between the hole injection layer a and the hole injection layer b, the work function of the hole injection layer b is equal to or smaller than that of the hole injection layer a. There is a need to. The reason for this is that the organic material is inevitably oxidized when the foreign material is embedded by making the material such as a heat treatment fluid, and avoids the problem that the driving voltage of the organic EL element rises. Is.

By making the work function of the hole injection layer a combination of the above, it becomes possible to adjust the redox potential of the organic material, reduce the oxidation of this organic layer, and suppress the drive voltage rise.

In the present invention, the hole injection layer a and the hole injection layer b.
After forming the laminated body of, heat treatment is performed. Addition at this time
The heat temperature is higher than the glass transition point of the material of the hole injection layer b.
Higher temperature, preferably higher than 20 ° C, more preferable
For example, the treatment may be performed at a temperature higher than 40 ° C. Heat
The atmosphere during the heating is preferably a non-oxidizing atmosphere, for example N 2.
₂ , Ar atmosphere and the like. At this time, in the atmosphere
The oxygen concentration should be less than 1%, especially 0.05% or less.
preferable. When the oxygen concentration is 1% or more, the oxidation phenomenon of organic materials may occur.
Will occur.

There is no problem even in a depressurized atmosphere or a pressurized atmosphere as long as the oxygen concentration is sufficiently low. Even if the heat capacity of the substrate is taken into consideration, the heating time is about several tens of minutes to obtain a sufficient effect.

The heat treatment step at this time may be performed, for example, with the film-forming surface of the substrate 1, that is, the surface on which the organic layers 3 and 4 are formed, facing downward, as shown in FIG.
By performing heat treatment with the film-forming surface of the substrate facing downward, the melted and fluidized organic material becomes foreign matter 1 due to gravity.
It becomes easy to aggregate into 1 and the leak can be suppressed more effectively.

A hole transport layer is preferably formed on the heat-melted organic layer. To select the hole transport layer formed in contact with the heat-melted organic layer, it is necessary to select a material having a small work function difference. Specifically, the difference in work function from the heat-melted organic layer as the base is preferably less than ± 0.4 eV, and more preferably ± 0.2 eV or less. The reason is that the heat-melted organic layer has an increased work function and a reduced hole injecting property, and the work function difference between the organic layer and the organic layer in contact therewith affects the driving voltage.

If the work function relationship between the heat-melting organic layer and the light-emitting layer falls within the above range, the light-emitting layer may be formed in contact with the heat-melting organic layer.

The film thickness of each organic layer is selected to obtain the characteristics of the device, but from the viewpoint of device leakage,
The ratio of the total thickness of the heat-melting organic layer and the thickness of the organic layer disposed on the cathode side of the total is preferably the total thickness of the heat-melting organic layer: the total thickness of the other organic layers = 1: 20. ˜3: 1, more preferably 1:10 to 1: 1 and even more preferably
It is 1: 3 to 1: 1.

The reason is that there is a possibility that a foreign matter that causes a leak is generated on the ITO surface, and in addition to that, there is a possibility that the foreign matter is driven in from the cathode side.
When the cathode forming method is the sputtering method or the electron beam evaporation, there is a possibility that foreign matter may be implanted during the film formation, which may affect the element leakage.

When the film thickness of the heat-melting organic layer is thin, the ability to embed foreign matters existing on the ITO surface is insufficient, and when the film thickness of the organic layer thereafter is thin, this time, the cathode forming process is performed. Leakage due to foreign matter driven in will occur.

Considering this point, the organic E that is resistant to element leakage
The above film thickness range is selected for manufacturing the L element.

To form an element having these organic layers, first, an ITO film is formed as a hole injecting electrode on an insulating substrate such as glass and patterned by photolithography or the like.

Next, an end protection layer (edge cover) is formed in order to cover the end step of the ITO. The edge cover may be made of a photoresist, an organic material such as polyimide, or an inorganic material such as SiO ₂ , but a photoresist is preferable from the viewpoint of the manufacturing process. After that, dry cleaning such as UV / O ₃ treatment is applied to remove organic contamination on the ITO surface.

Next, as the hole injecting layer a, for example, a labyrinthine tertiary amine-based material is formed by vapor deposition.

Next, as the hole injecting layer b, for example, a tetraaryl pentidine compound (TPD) based material is formed by vapor deposition.

At this time, the material selected for the hole injection layer a has no glass transition point Tg or is higher than the Tg of the hole injection layer b.

After the laminated film formation of the hole injection layer a and the hole injection layer b is performed, heat treatment is performed. The heating temperature at this time is as described above, and the atmosphere for heating is also as described above.

Next, if necessary, a hole-transporting material is formed into a hole-transporting layer to form a light-emitting layer.

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

The light emitting layer has a function of injecting holes and electrons, a function of transporting them, and a function of generating excitons by recombination of holes and electrons.

Known organic light emitting layers can be used. For example, quinolinolato complexes are known. Specifically, 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-quinolinolato lithium, tris (5-chloro-8-quinolinolato) gallium, bis (5-chloro-8-quinolinolato) calcium, 5,7-dichloro-8-quinolinolato aluminum, tris (5,7-Dibromo-8-hydroxyquinolinolato) aluminum, poly [zinc (II) -bis (8-
Hydroxy-5-quinolinyl) methane] and the like.

In addition, the phenylanthracene derivatives described in JP-A-8-12600 and JP-A-8-12969.
The tetraarylethene derivatives described in JP-A No. 1994-200242 are also preferable.

The light emitting layer may also serve as the electron injecting and transporting layer, and in such a case, tris (8-quinolinolato) aluminum or the like is preferably used. These fluorescent substances may be deposited.

The light emitting layer is also preferably a mixed layer of at least one hole injecting and transporting compound and at least one electron injecting and transporting compound, if necessary.
Furthermore, it is preferable to include a dopant in this mixed layer.

That is, the organic light-emitting layer of the device may contain a fluorescent substance in an amount of 0.1 to 10% by mass.
Inclusion of a fluorescent substance improves luminous efficiency and life characteristics,
Alternatively, they are mixed for the purpose of adjusting the emission wavelength.

Examples of such a fluorescent substance include:
At least one selected from the compounds disclosed in JP-A-63-264692, for example, compounds such as quinacridone, rubrene, and styryl dyes can be mentioned. Further, quinoline derivatives such as metal complex dyes having 8-quinolinol such as tris (8-quinolinolato) aluminum or a derivative thereof as a ligand, tetraphenylbutadiene, anthracene, perylene, coronene, 12-
Examples include phthaloperinone derivatives. Further, the phenylanthracene derivative described in JP-A-8-12600 and the tetraarylethene derivative described in JP-A-8-12969 can be used.

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

If necessary, the organic layer of the present invention may be provided with an electron injection layer, an electron transport layer, an electron injection transport layer and the like formed of an electron injection transport material.

The electron injecting and transporting 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.

In the present invention, as a compound that can be preferably used in the organic electron injecting layer and the electron transporting layer, for example, 8-quinolinol such as tris (8-quinolinolato) aluminum (Alq3) or a derivative thereof is coordinated. Organometallic complex as a child, oxadiazole derivative,
Perylene derivative, pyridine derivative, pyrimidine derivative,
Examples thereof include quinoxaline derivatives. Also,
It is also possible to use the above-mentioned phenylanthracene derivative and tetraarylethene derivative.

A thin film is formed by vapor deposition using these organic materials. When the vacuum evaporation method is used, an amorphous state or a homogeneous thin film having a crystal grain size of 0.2 μm or less can be obtained. If the crystal grain size exceeds 0.2 μm, non-uniform light emission occurs, the drive voltage of the device must be increased, and the charge injection efficiency is significantly reduced.

In the present invention, the organic light emitting layer and the hole injection layer are used.
A transport layer or a hole injection layer and a hole transport layer, and
Of the electron injection transport layer or electron injection layer and electron transport layer
The conditions for forming each layer by vapor deposition are particularly limited
Not a thing, but 1 × 10^-FourWhen the pressure is less than Pa, the deposition rate is 0.
It is preferably about 01 to 1 nm / sec. Each layer is 1
× 10^-FourBeing formed continuously under reduced pressure below Pa
Is preferred. 1 x 10 ^-FourContinuously under reduced pressure below Pa
By forming each layer, impurities are absorbed at the interface of each layer.
Since it can be prevented from being worn, it has
It becomes possible to obtain an organic EL element and an organic EL element
Drive voltage is reduced, dark spots are generated, and growth occurs
Can be suppressed.

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

Next, an inorganic electron injecting layer having a high resistance is preferably provided as an electron injecting layer for improving the luminous efficiency. The high resistance inorganic electron injecting layer includes insulating alkali metal compounds such as LiF and Li ₂ O, Li ₂ MoO ₄ and RuO ₂ :
Li ₂ O or the like can be used.

The high resistance inorganic electron injecting and transporting layer has a thickness of 0.2 to
It is preferable to have a film thickness of 30 nm, and 0.2 to 2
It is particularly preferable to have a film thickness of 0. Even if the thickness of the high resistance inorganic electron injecting and transporting layer is less than 0.2 nm, it is 30 nm.
Even if it exceeds, the function of electron injection cannot be fully exerted.

An electron injection electrode is formed on this electron injection layer. A normal metal can be used for the electron injection electrode. Among them, Al, Ag, I from the viewpoint of conductivity and handleability.
One or more metal elements selected from n, Ti, Cu, Au, Mg, Mo, W and Pt are preferable.

The electron injection electrode is formed by the sputtering method,
There are a resistance heating vapor deposition method, an electron beam vapor deposition method and the like.
The resistance heating vapor deposition method is selected from the viewpoints that each has advantages and disadvantages and good device characteristics are obtained, and the sputtering method is selected from the viewpoint of mass productivity, and a formation method suitable for the purpose may be adopted.

The thickness of these electron injecting electrodes may be a certain thickness or more capable of giving electrons to the electron injecting and transporting layer, and may be 50 nm or more, preferably 100 nm or more. The upper limit is not particularly limited, but the film thickness is usually about 50 to 500 nm.

Furthermore, in order to protect the organic EL element from moisture in the atmosphere, if a protective layer is provided, it is possible to suppress deterioration due to the occurrence of dark spots (called dark spots) occurring in the element. The protective film is SiN, SiON, S
A film having a high water blocking ability such as iO ₂ or Al ₂ O ₃ is preferable.

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

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

The total thickness of the electron injecting electrode and the protective layer is not particularly limited, but it is usually about 50 to 500 nm.

Thereafter, in order to prevent the deterioration of the element, the element is sealed with a sealing plate or the like. The sealing plate is sealed with an adhesive resin. The sealing gas is preferably an inert gas such as Ar, He or N ₂ . Moreover, a desiccant is added if necessary.

As the material of the sealing plate, it is possible to use a material different from that of the substrate, but it is preferable to use the same material as the material of the substrate, or one having the same thermal expansion coefficient and mechanical strength.

The height of the sealing plate may be adjusted by using a spacer and held at a desired height.

In the present invention, the substrate on which the organic EL structure is formed is an amorphous substrate such as glass or quartz, a crystalline substrate such as Si, GaAs, ZnSe or Z.
Examples thereof include nS, GaP, InP, and the like, and a substrate in which a crystalline, amorphous, or metal buffer layer is formed on these crystalline substrates can also be used. Moreover, as the metal substrate, Mo, Al, Pt, Ir, Au, Pd, or the like can be used. Further, a resin material such as plastic or a flexible material can be used. The substrate material is
A glass substrate and a resin material are preferable. When the substrate is on the light extraction side, it is preferable that it has the same light transmittance as that of the electrode.

As the glass material, alkali glass is preferable from the viewpoint of cost, but in addition to this, glass compositions such as soda lime glass, lead alkali glass, borosilicate glass, aluminosilicate glass, and silica glass are also preferable. In particular, soda glass, which is a glass material having no surface treatment, can be used at low cost.

The substrate may be provided with a color filter film, a color conversion film containing a fluorescent substance, or a dielectric reflection film to control the emission color.

As the color filter film, a color filter used in a liquid crystal display or the like may be used.
The extraction efficiency and color purity may be optimized by adjusting the characteristics of the color filter according to the light emitted from the organic EL element.

Further, if a color filter capable of cutting outside light of a short wavelength which is absorbed by the EL device material or the fluorescence conversion layer is used, the light resistance of the device and the display contrast are improved.

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

Through the above steps, it becomes possible to manufacture an organic EL element in which element leakage is unlikely to occur.

The organic EL device of the present invention is, for example, as shown in FIG. 1, substrate 1 / hole injection electrode 2 / hole injection layer a3 /
The hole injection layer b4 / hole transport layer 5 / light emitting layer 6 / electron injection layer a7 / electron injection layer b8 / inorganic electron injection / transport layer 9 / electron injection electrode 10 are laminated in this order. In addition, the electron-injection electrode 10 may be formed on the substrate 1 side to form a reverse stack. The laminated structure may be an optimum laminated structure depending on the required performance and specifications. The organic layer may have a multi-layer structure in which a hole injecting / transporting layer, a light emitting layer, an electron injecting / transporting layer, and the like are stacked, or a single layer structure in which the light emitting layer has an electron injecting / transporting function, a hole transporting function, and the like. May be

The organic EL element can be driven by direct current or pulse, and can also be driven by alternating current. Applied voltage is usually 2
It is about 30V.

[0083]

EXAMPLES Example 1 On the glass substrate 1, a transparent conductive film ITO 100 nm as the hole injection electrode 2 was formed. This substrate was subjected to ultrasonic cleaning for 10 minutes and then rinsed with pure water. Then, it baked at 110 degreeC in the oven for 8 hours or more. The ITO-attached substrate was washed with UV / O ₃ and then introduced into a vacuum device to reduce the pressure in the tank to 1 × 10 ⁻⁴ Pa or less.

As the hole injection layer a3, 10 n of the first tetraarylbenzidine compound (glass transition point 127 ° C.) was used.
Then, a second tetraarylbenzidine compound (glass transition point: 95 ° C.) 30 nm was formed as a hole injection layer b4 by vacuum vapor deposition.

The glass substrate provided with the organic layer was placed at 180 ° C. in an oven in an air atmosphere with the film-forming surface facing downward at 10 ° C.
Melt heat treatment was performed for minutes.

It was again introduced into the vacuum apparatus and the vacuum was evacuated to 1 × 10 ^-4 Pa or less. After that, a first hole transport layer 5 is formed.
70 nm of the tetraarylbenzidine compound was formed, and the first tetraarylbenzidine compound and the anthracene derivative were used as co-evaporation hosts, and rubrene and a styrylamine derivative were added as dopants to form a light emitting layer 6 having a thickness of 60 nm.

Next, an anthracene derivative having a thickness of 20 nm was formed as an electron injecting and transporting layer a7, and tris (8-quinolinato) aluminum having a thickness of 10 nm was formed as an electron injecting layer b8.

Then, as the high resistance inorganic electron injection layer 9, L
i ₂ MoO ₄ was formed to a thickness of 1 nm, and then 300 nm of aluminum was formed as the electron injection electrode 10 by a vapor deposition method.

This organic EL device was sealed with an adhesive using a glass plate coated with a desiccant.

The electrical characteristics of the organic EL device thus produced were measured, and the current density was 10 mA / cm ^2.
Voltage was 7.6 V and the luminance was 840 cd / m ² .

Regarding this organic EL element, the element ITO
-Reverse bias voltage -30 to measure cathode-to-cathode leakage
The leak current at V was measured to be 1 × 10 ¹⁰ A / mm ²
(Average of 200 samples) was below.

Further, when it was stored at 85 ° C. for 1000 hours, no change was observed on the light emitting surface, and the deterioration in luminance was good within 10%.

Example 2 The correlation between the work function of the organic material selected for the heat-melting organic layer and the driving voltage of the organic EL element was determined.

The material shown in Table 1 was formed to a thickness of 10 nm as a hole injection layer a in contact with ITO, and then a second tetraarylpentidine compound (glass transition point 95) was formed as a hole injection layer b.
(° C) 30 nm was formed by vacuum evaporation. This is placed in an oven in an air atmosphere with the deposition surface of the substrate facing downward.
After heat treatment for melting at 80 ° C. for 10 minutes, an organic EL device was manufactured in the same manner as in Example 1.

For each of the obtained devices, 10 mA / cm ²
And the drive voltage when driven at 100 mA / cm ² . The results are shown in Table 1.

[0096]

[Table 1]

From these results, it was found that the hole injection material in contact with ITO had a higher work function and the driving voltage decreased.

Further, when the element leak was measured for these organic EL elements, the same results as in Example 1 and good results were obtained.

Example 3 As the hole injecting layer a, the first tetraaryl benzidine compound (glass transition point 127
℃) 10nm, then the second hole injection layer b as a second tetraaryl benzidine compound (glass transition temperature 95 ℃) 30nm
Was formed by vacuum evaporation. This glass substrate with an organic layer is placed in an oven with a nitrogen atmosphere (dew point -50 ° C) without opening to the atmosphere.
Melt heat treatment was performed at 80 ° C. for 10 minutes.

The electrical characteristics of the organic EL device thus manufactured were measured, and the current density was 10 mA / cm ^2.
The voltage was 6.6 V and the luminance was 820 cd / m ² .

Further, when the element leak was measured for these organic EL elements, the same result as in Example 1 and good results were obtained.

Example 4 First Tetraaryl Penzidine Compound (Glass Transition Point 127 ° C.) as Hole Injection Layer a
Of 10 nm, and then, as the hole injecting layer b, a second tetraaryl benzidine compound (glass transition temperature 95 ° C.) was added to 20,3
It was formed by vacuum vapor deposition at 0, 50 and 90 nm. Then, an organic EL device was prepared in the same manner as in Example 1.

For comparison, Table 2 also shows the results of the execution of film thicknesses and film thickness ratios outside the above ranges.

[0104]

[Table 2]

The leak element was an element having a current value of 4 × 10 ⁻⁷ A / mm ² or more at a voltage of −30 V.

From Table 2, it is effective that the film thickness of the heat-melting organic layer is 20 nm or more, and it is particularly preferable that the film thickness of the organic layer is 100 nm or more. It was found that the leak element was reduced when the film thickness ratio was 1:10 to 1: 2.

[Comparative Example 1] A single layer of the hole transport layer b was formed without laminating the heat-melting organic layer, and a comparison was made with the laminated heat-melting organic layer described in Example 1. As the hole injecting layer b in contact with ITO, 40 nm of the second tetraaryl benzidine compound (glass transition point 95 ° C.) was formed by vacuum evaporation.
This was melt-heated at 180 ° C. for 10 minutes in an oven in the air atmosphere, and then a mechanical EL element was manufactured in the same manner as in Example 1.

Regarding this lateral EL element, the ITO of the element
-Reverse bias voltage -30 to measure cathode-to-cathode leakage
The leak current at V was measured to be 5 × 10 ^-7 A / mm ²
It was about (average of 200 samples), resulting in extremely large leak.

Further, when a high temperature storage test was carried out at 85 ° C., unevenness was observed on the light emitting surface in about 150 hours, and a defect occurred as a commercial mass-produced product.

[0110]

As described above, according to the present invention, it is possible to prevent a partial short-circuit between electrodes or an approximate short-circuit state, and to obtain a high-quality yield that does not cause erroneous light emission or display unevenness due to a leak current. A good organic EL element can be realized.

[Brief description of drawings]

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

FIG. 2 is a partial cross-sectional view showing a state in which an organic material is aggregated into foreign matter by gravity due to a heat treatment process after forming an organic layer.

[Explanation of symbols]

1 glass substrate 2 Hole injection electrode (first electrode) 3 Hole injection layer a 4 Hole injection layer b 5 Hole transport layer 6 light emitting layer 7 Electron injection layer a 8 Electron injection layer b 9 Inorganic high resistance electron injection layer 10 Electron injection electrode (second electrode) 11 foreign matter

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Michio Arai             1-13-1, Nihonbashi, Chuo-ku, Tokyo             -In DC Inc. F-term (reference) 3K007 AB06 AB11 AB17 AB18 CA01                       CB01 DA01 DB03 EB00 FA01

Claims (8)

[Claims] 1. A first electrode and a second electrode are sequentially provided on a substrate, and at least one layer between these electrodes has a light emitting function.
The organic layer has at least two layers, and at least two organic layers of the organic layer have a structure in which foreign matter is embedded. Among the at least two organic layers, the organic layer is in contact with the first electrode. An organic EL device in which the glass transition point of the organic layer is higher than the glass transition point of the organic layer in which other foreign matter is embedded. 2. An organic layer other than the organic layer in contact with the first electrode,
The organic EL device according to claim 1, wherein the work function of the organic layer in which the foreign matter is embedded is equal to or smaller than the work function of the organic layer in contact with the first electrode. 3. The total film thickness of the organic layer in which the foreign matter is embedded is
The ratio to the total thickness of the other organic layers is 1:10 to 1:
The organic EL element which is 1. 4. A substrate having a first electrode and a second electrode in sequence on a substrate, at least one layer having a light emitting function between these electrodes.
Having at least two organic layers, and having a structure in which at least two or more organic layers of the organic layers embed foreign matter, and embedding foreign matter other than the organic layer in contact with the first electrode. An organic EL device in which the work function of the organic layer is equal to or smaller than the work function of the organic layer in contact with the first electrode. 5. A substrate having a first electrode and a second electrode successively on a substrate, and at least one layer having a light emitting function between these electrodes.
The organic layer has at least two layers, and at least two or more of the organic layers have a structure in which foreign matter is embedded, and the total thickness of the organic layer in which foreign matter is embedded is Organic E having a ratio of 1:10 to 1: 1 with respect to the total thickness of the organic layer
L element. 6. The method for producing an organic EL device according to claim 1, wherein the organic layer in which the foreign matter is embedded is heated by melting at a temperature of a glass transition point or higher and a melting point or lower. A method for manufacturing an organic EL element, which is processed by a melting step. 7. The method for manufacturing an organic EL device according to claim 6, wherein the heat melting step is performed in an atmosphere having an oxygen concentration of less than 1%. 8. The organic EL device according to claim 6, wherein the heat-melting step is performed with the film formation surface of the substrate facing downward.
Device manufacturing method.