JP2000268954A - Light emitting element - Google Patents

Abstract

(57) [Summary] [Problem] Since an organic light-emitting element has extremely low moisture resistance, realizing a flexible display made of a plastic film has a problem in terms of life. SOLUTION: By providing a water trapping film 12 made of zeolite, colored powder and organic resin inside a sealing,
A flexible organic light-emitting panel with high contrast and long life characteristics is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display element used as a light emitting display or a backlight for a liquid crystal display.

[0002]

2. Description of the Related Art Electroluminescent (EL) panels have the characteristics of high visibility, excellent display capability, and high-speed response. In recent years, reports have been made on organic light-emitting devices using organic compounds as constituent materials (for example, see the related paper Applied Physics Letters, No. 51).
Volume 913, 1987 (Applied Physics Letters, 51, 19)
87, P.913.))).

[0003] This report describes an organic light emitting device having a structure in which an organic light emitting layer and a charge transport layer are laminated. A tris (8-quinolinol) aluminum complex (hereinafter Alq) has been developed as a luminescent material, and is an excellent luminescent material having both high luminous efficiency and electron transport. Also, Journal of Applied Physics, Vol. 65, No. 36
10 1989 (Journal of Applied Physics, 65, 198)
9, p.3610.), A device was prepared in which Alq for forming an organic light emitting layer was doped with a fluorescent dye such as a coumarin derivative or DCM1, and it was found that the emission color was changed by appropriate selection of the dye. Furthermore, it was clarified that the luminous efficiency was increased as compared with the undoped one. On the other hand, the organic light emitting device has a problem that it is very weak against moisture and has a short life.

[0004] However, improvement of the life, which has been the biggest issue in recent years, has progressed, and it is expected to be a next-generation flexible display (paper display). The flexible display is a thin, light, and flexible film-shaped display, and can make use of the characteristics of the organic light-emitting device of the self-luminous type. In the development of a film display, the gas barrier property of a film used for a substrate or for sealing is an important issue, and especially for an organic light-emitting device having extremely low moisture resistance, moisture permeability is the most important issue. Development has already progressed in the field of liquid crystal panels or dispersed inorganic EL panels and the like, and the moisture permeability of fluorine films is said to be comparable to that of metals.

[0005] Among them, ethylene trifluoride chloride resin film is excellent in both moldability and moisture-proof property. For example, Japanese Patent Application Laid-Open No. 7-153571 discloses a thin, organic light-emitting device having a structure in which both sides of a film-shaped organic light-emitting element are sandwiched between moisture-absorbing films, and both sides are sandwiched between moisture-proof films.
It is described that the effect of a light source having a light shape and a free shape can be obtained. Nylon 6 is used for the moisture-absorbing film and ethylene trifluoride is used for the moisture-proof film.
Although the structure is the same as that of the L panel, since the organic EL element is very weak against moisture, the hygroscopic nylon film cannot obtain a sufficient dehydration effect by heat treatment at 90 ° C., and functions as a hygroscopic film. I ca n’t do it.

In addition, the organic light emitting device described is
The organic light-emitting layer and the electrode layer are separately formed and then bonded to each other, and this method causes deterioration of an interface portion most important for charge injection, so that sufficient luminance cannot be obtained or Does not glow.

Japanese Patent Application Laid-Open No. 8-167475 discloses an EL device sealing method in which a thin film layer made of an inorganic material is formed on one or both surfaces of a plastic film, and a heat-fusible plastic is further laminated via an adhesive layer. It describes an EL element sealing structure in which a gas barrier property, a water vapor barrier property, and high transparency are simultaneously added by a laminate.
Organic E between the heat-fusible plastics
It has a structure sandwiching the L element.

However, in practice, it is important that moisture enters from the adhesive surface where the heat-fusible plastics are superimposed on each other or adheres to the film surface or the element surface. Does not provide sufficient life characteristics.

[0009] In order to prevent intrusion of moisture, for example, in the element configuration described in JP-A-10-275682, after forming a protective layer on an organic layer and a cathode, an oxygen absorbent is formed in a sealing portion. By filling with an inert medium together with a dehydrating agent, generation and growth of black spots are suppressed.

The protective layer is intended to protect from moisture and from an inert medium, especially an inert liquid, and from an oxygen absorbent and a dehydrating agent. However, in forming a film, the protective layer is liable to generate stress. There is a risk of damaging the element. Further, the number of manufacturing processes increases, which leads to an increase in cost in mass production.

In Japanese Patent Application Laid-Open No. 60-97, a mixture of zeolite and a light-absorbing powder is formed into a thick film or a ceramic and fixed to the inner wall of a seal cap, thereby improving moisture resistance. At the same time, the contrast was improved and the production was simplified.

In particular, in Japanese Patent Application Laid-Open No. 61-96695, a composite of zeolite, carbon powder, and an organic resin is formed into a film, and the film is fixed to the inner wall of a seal cap of an EL panel to improve the moisture resistance.

[0013] In particular, regarding the advantage of forming the above-mentioned composite into a film, it is mentioned that the composite can be easily cut by a cutter and is hardly damaged to be easily handled. E described here
The L panel relates to an inorganic EL panel as apparent from the fact that ZnS is used as a base material of the phosphor layer. As described above, the development of the organic EL element began in 1987, and at that time, the EL panel was used. A panel refers to an inorganic EL panel.

In the manufacturing process, 600 inorganic EL panels are used.
Since high-temperature processing of about ° C. is performed, plastic or the like cannot be used for a substrate on which an EL layer is formed, and a flexible panel cannot be realized.

[0015]

As described above, in making a display into a film, there still remains a problem with respect to ingress of moisture from an adhesive surface, and an inorganic compound is required for long-term storage. Compared with the storage stability of a glass substrate or the like made of, a substrate or a protective layer made of an organic material still has insufficient life stability with respect to the moisture permeability of the film.

When the water-absorbing agent is encapsulated in a powder or solid form, the organic light-emitting device may be damaged by contact when the flexible display is curved, and the device may be short-circuited or the like. There was a problem of losing the function as.

[0017]

Accordingly, we have realized a film-shaped organic light-emitting device by providing a film-like humectant in a sealing portion, and have also realized an organic light-emitting device by trapping moisture that enters after sealing. This has solved the problem by preventing deterioration of the light emitting element.

Specifically, according to the light emitting device of the present invention (claim 1), an organic light emitting device having at least an organic light emitting layer is formed on a flexible substrate, sealed with a moisture-proof film, and zeolite and a colored powder. It is characterized in that a water trapping film made of a body and an organic resin is provided inside the sealing.

Further, the organic light emitting device has an organic light emitting layer formed between a positive electrode and a negative electrode, or a hole transport layer and an organic light emitting layer between a positive electrode and a negative electrode. Or a structure in which a hole transport layer, an organic light emitting layer and an electron transport layer are laminated between a positive electrode and a negative electrode. Further, the inside of the sealing is in a vacuum state.

Further, according to the light emitting device of the present invention (claim 6), the organic light emitting device having at least the organic light emitting layer is formed on a flexible substrate, sealed with a moisture-proof film, and the zeolite, the colored powder and the organic light emitting device. A water trapping film made of a resin is fixed to a sealing inner surface of the moisture-proof film.

Further, the organic light emitting device has a structure in which an organic light emitting layer is formed between a positive electrode and a negative electrode, a structure in which a hole transport layer and an organic light emitting layer are stacked, It has a configuration in which a layer, an organic light emitting layer, and an electron transport layer are laminated.

Further, the water catching film is fixed to the sealing inner surface of the moisture proof film with a hot melt type resin film.

Further, the water catching film is fixed to the sealing inner surface of the moisture proof film with a hot melt type resin film having hygroscopicity.

Further, an inert gas is filled in the sealing of the organic light emitting element.

Further, the colored powder contained in the water catching film of the organic light emitting device is a black powder.

[0026]

Embodiments of the present invention will be described below. The organic light-emitting element is a thin film device having an organic layer having a thickness of about 1000 angstroms (Å) in a low molecular weight system and about several thousand Å in a high molecular weight system, and having a thickness of about 1 μm even when an electrode layer is added. Therefore, the device depends on the thickness and shape of the substrate. If a thin and light substrate is used, a thin and lightweight device can be provided. Furthermore, by using a flexible substrate, it is possible to realize a curved surface display, which has been difficult due to a problem of a viewing angle in a liquid crystal display, by utilizing a feature of a self-luminous type.

As the substrate, a transparent or translucent glass substrate or a plastic film or sheet is used.
In the case of glass, it can be curved by using a thin substrate having a thickness of 50 to 500 μm. In the case of plastic, it is selected in consideration of optical characteristics, heat resistance, dimensional stability, surface flatness and the like.

Materials satisfying these requirements include amorphous thermoplastic resins such as polycarbonate, polyacrylate, polyether sulfone, and cyclic amorphous polyolefin, polyfunctional acrylates, polyfunctional polyolefins, and the like.
Thermosetting resins such as unsaturated polyesters and epoxy resins are preferred.

Although organic light-emitting devices are very weak against moisture, plastic film sheets are inherently inferior to glass in oxygen and water vapor barrier properties. Coating is required. As a material for the barrier film,
Ethylene vinyl alcohol copolymer, polyacrylonitrile, polyvinylidene chloride, polysilazane, a deposited silicon oxide film, a deposited silicon nitride film, and the like are preferable.

In the process of manufacturing the organic light emitting device,
In particular, solution coating method, Langmuir Blodgett (LB)
When a treatment containing an organic solvent such as a method is performed, a solvent-resistant film for protecting the plastic film / sheet is coated. Examples of the method for processing the solvent-resistant film include wet coating.

Further, the organic light-emitting device emits surface light by making at least one of the electrodes transparent or translucent.
It is necessary to take into account the released gas. Usually, an ITO (indium tin oxide) film is often used for an anode serving as a hole injection electrode. In addition, tin oxide, Ni, Au, P
t, Pd and the like.

For the purpose of improving the transparency or reducing the resistivity of the ITO film, a film forming method such as sputtering, electron beam evaporation, or ion plating is employed.

The film thickness is determined from the required sheet resistance value and visible light transmittance. However, since the driving current density of the organic light emitting element is relatively high, the thickness is more than 100 nm in order to reduce the sheet resistance value. It is often used by the way.

In the case of a plastic substrate, in particular, a reactive sputtering method using an indium-tin alloy target,
A transparent electrode film is formed by a sputtering method using an indium tin oxide target.

Next, the organic light emitting layer in the present invention is preferably made of tris (8-hydroxyquinoline) aluminum which is an electron transporting light emitting material. Another example is Tris (4
-Methyl-8-hydroxyquinoline) aluminum and other metal complexes. At the same time, dyes having various emission colors may be contained, and dyes of each color may be mixed in the same layer, or layers having each dye may be stacked or arranged in parallel.

As a constituent material of the hole transport layer, a derivative having triphenylamine as a basic skeleton is preferable. For example, a tetraphenylbenzidine compound, a triphenylamine trimer described in JP-A-7-126615,
And benzidine dimer. Also, JP-A-8-48
Various triphenyldiamine derivatives described in JP-A-6-656 or MTP described in JP-A-7-65958
D (commonly known as TPD). In particular, Japanese Patent Application No. 9-341
No. 238 is preferred.

As a constituent material of the electron transport layer, tris (8-hydroxyquinoline) aluminum is preferable.
Other examples include metal complexes such as tris (4-methyl-8-hydroxyquinoline) aluminum. The electron transport layer preferably has a thickness of 10 to 1000 nm. Regarding the organic layers of the above-described hole transport layer, light-emitting layer, and electron transport layer, it is desirable to form a homogeneous film in an amorphous state, and it is preferable to form the film by a vacuum evaporation method.

Further, by continuously forming each layer in a vacuum, it is possible to prevent impurities from adhering to the interface between the respective layers, thereby improving characteristics such as lowering of operating voltage, higher efficiency and longer life. Can be planned.

In forming each of these layers by a vacuum deposition method, when one layer contains a plurality of compounds,
It is preferable to perform co-evaporation by individually controlling the temperature of each boat containing the compound, but it is also possible to vapor-deposit a mixture in advance.

Further, as other film forming methods, a solution coating method, a Langmuir-Blodgett (LB) method, or the like can be used. In the solution coating method, a functional material such as a dye or a charge transporting material may be dispersed in a matrix material such as a polymer.In order to further enhance thermal stability, the functional material may be dispersed in the main chain or side of the polymer. It may be composed of a polymer, a copolymer, a block copolymer or the like incorporated in a chain.

The cathode as an electron injection electrode has Tang.
In many cases, an alloy of a metal having a low work function and a low electron injection barrier, such as a MgAg alloy or an AlLi alloy, and a metal having a relatively large work function and being stable is used. Further, a metal having a low work function may be formed on the organic layer side, and a metal having a large work function may be laminated thickly for the purpose of protecting the metal having a low work function, such as Li / Al or LiF / Al.
Such a laminated electrode can be used. For forming these cathodes, a vapor deposition method or a sputtering method is preferable.

Examples of the moisture-proof film include those coated with a barrier film, such as the above-mentioned plastic film sheet serving as a substrate, or a fluororesin. Particularly, ethylene trifluoride chloride which satisfies all of the water vapor barrier property, transparency and moldability is preferable.

As the water catching film, it is preferable to use an organic resin which is relatively permeable to water. Any water-permeable film can be used as long as it has appropriate water permeability and heat resistance. Urethane or polyvinyl alcohol is preferable. As a result of examining the maintenance of the life characteristics of the organic light emitting device, a heat treatment at 200 ° C. or more is required for dehydration of zeolite, and therefore, a urethane resin having particularly excellent heat resistance is preferable. Since urethane has high flexibility, it also serves as a buffer, and does not cause any damage such as short-circuiting of the device even when directly contacting the organic light emitting device. Therefore, a protective layer on the surface of the organic light emitting device is not required.

Examples of the colored powder to be mixed include light-absorbing oxide powders such as manganese oxide, chromium oxide, nickel oxide, copper oxide, and iron oxide. Usually, in the display field, a black powder such as a carbon powder is particularly preferable as a colored powder so as to arrange a black matrix between pixels in order to improve contrast.

As an example, urethane and zeolite are mixed at a weight ratio of 1: 3, and 4% by weight of carbon powder is added to the total amount to form a 0.3 mm thick film into a water catching film. A panel was prepared.

(Embodiment 1) FIG. 1 shows an embodiment of an organic light emitting panel according to the present invention, which is a part of a structure having a water trapping film inside a seal in which an organic light emitting element is sandwiched between moisture-proof layers. FIG.

As shown in FIG. 1, N, N was deposited on a polycarbonate film (not shown) in which ITO was formed in a strip shape.
50n consisting of N'-bis (4'-diphenylamino-4-biphenylyl) -N, N'-diphenylbenzidine
A hole transport layer (not shown) having a thickness of m is formed. Subsequently, as a light emitting layer, tris (8-hydroxyquinoline)
Aluminum was deposited to a thickness of 50 nm to form an electron transporting light emitting layer (not shown).

Finally, a strip-shaped negative electrode made of an AlLi alloy is formed so as to be orthogonal to the ITO, and the organic light emitting element 11 is formed.
I got The water-absorbing film 12 is heated and dried in the air at 200 ° C. for 2 hours, and then placed on the element surface so as to cover the element surface. The portion was sealed to obtain a flexible organic light emitting panel.

When this panel was curved while displaying images such as characters and pictures, the visibility was high and the contrast was high. Furthermore, when it was left unattended in a constant temperature and high humidity layer at 80 ° C. and 90%, the black spot diameter was 10 μm or less even after 1000 hours, showing a favorable light emitting state.

(Example 2) After an organic light-emitting device was manufactured with the same composition as in Example 1, when the both surfaces were sandwiched between moisture-proof layers, the water-trapping film was fixed to the inner surface of the moisture-proof layer on the cathode side with an epoxy resin. After that, the peripheral portion was sealed in a state of being filled with nitrogen gas to obtain a flexible organic light-emitting panel.

When this device was left unattached in a constant temperature and high humidity layer at 80 ° C. and 90%, the black spot diameter was 1 after 1000 hours.
At 0 μm or less, a good light emitting state was exhibited.

Example 3 The same procedure as in Example 2 was carried out except that the epoxy resin of Example 2 was used as a nylon 6 film, sandwiched between a water catching film and a moisture-proof layer, and heated and fused at 150 ° C. An organic light emitting device was produced by the method.

When this device was left unattached in a constant temperature and high humidity layer at 80 ° C. and 90%, the black spot diameter was 1 after 1000 hours.
At 0 μm or less, a good light emitting state was exhibited.

(Example 4) The same procedure as in Example 2 was repeated except that the epoxy resin of Example 2 was used as a nylon 6 film, a slightly larger nylon film was placed on the water catching film, and heated at 150 ° C to fuse the film to the moisture-proof layer. An organic light-emitting device was manufactured in the same manner as in Example 2.

When this device was left unattached in a constant temperature and high humidity layer at 80 ° C. and 90%, the black spot diameter was 1 after 1000 hours.
At 0 μm or less, a good light emitting state was exhibited.

Comparative Example 1 A 50 nm-thick film of N, N'-bis (4'-diphenylamino-4-biphenylyl) -N, N'-diphenylbenzidine was formed on a polycarbonate film on which ITO was formed. A hole transport layer is formed.

Subsequently, as a light emitting layer, tris (8-hydroxyquinoline) aluminum was deposited to a thickness of 50 nm to form an electron transporting light emitting layer. Finally, a negative electrode made of an AlLi alloy was formed.

A nylon 6 film was vacuum-dried on the device at 120 ° C. for 5 hours, and then placed so as to cover the element surface. Further, both surfaces were sandwiched by a moisture-proof layer, and the peripheral portion was sealed with the inside kept in vacuum. .

When this device was left unattached in a constant temperature and high humidity layer at 80 ° C. and 90%, the black spot diameter became 1 after 100 hours.
It exceeded 00 μm and hardly emitted light.

[0060]

As described above, according to the present invention, when an organic light-emitting device manufactured on a film-like substrate is sealed with a moisture-proof film,
By providing a water-trapping film made of zeolite, colored powder, and organic resin inside the sealing, a flexible display with high contrast and long life can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a part of a structure having a water trapping film inside a seal in which an organic light-emitting element according to an embodiment of the present invention is sandwiched between moisture-proof layers.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Organic light emitting element 12 Water catching film 13 Moisture-proof layer

 ──────────────────────────────────────────────────続 き Continued from the front page (72) Inventor Tetsuya Sato 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 72) Inventor Hisanori Sugiura 1006 Kadoma, Kazuma, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd.

Claims (13)

[Claims] An organic light-emitting device having at least an organic light-emitting layer formed on a flexible substrate and sealed with a moisture-proof film, wherein a water-trapping film made of zeolite, a colored powder and an organic resin is sealed. A light-emitting element provided inside. 2. The light emitting device according to claim 1, wherein the organic light emitting device has an organic light emitting layer formed between a positive electrode and a negative electrode. 3. The light emitting device according to claim 1, wherein the organic light emitting device has a structure in which a hole transport layer and an organic light emitting layer are stacked between a positive electrode and a negative electrode. 4. The light emitting device according to claim 1, wherein the organic light emitting device has a structure in which a hole transport layer, an organic light emitting layer, and an electron transport layer are stacked between a positive electrode and a negative electrode. 5. The light emitting device according to claim 1, wherein the inside of the sealing is in a vacuum state. 6. A light-emitting element in which an organic light-emitting element having at least an organic light-emitting layer is formed on a flexible substrate and sealed with a moisture-proof film. A light-emitting element fixed to a sealing inner surface of a film. 7. The light emitting device according to claim 6, wherein the organic light emitting device has a structure in which an organic light emitting layer is formed between a positive electrode and a negative electrode. 8. The light emitting device according to claim 6, wherein the organic light emitting device has a structure in which a hole transport layer and an organic light emitting layer are laminated between a positive electrode and a negative electrode. 9. The light emitting device according to claim 6, wherein the organic light emitting device has a structure in which a hole transport layer, an organic light emitting layer, and an electron transport layer are stacked between a positive electrode and a negative electrode. 10. The light emitting device according to claim 6, wherein the water catching film is fixed to the moisture-proof film with a hot melt type resin film. 11. The light emitting device according to claim 6, wherein the hot melt resin film has a hygroscopic property. 12. The light emitting device according to claim 6, wherein an inert gas is filled in the sealing of the organic light emitting device. 13. The light emitting device according to claim 1, wherein the colored powder is a black powder.