JP2000058268A - Organic dispersion type EL device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] At the time of hot laminating by bonding a transparent electrode on a light emitting layer, a phosphor is depressed in an insulating layer due to softening of an organic binder, uneven brightness and an increase in current value flowing in the light emitting layer. Provided is an organic dispersion-type EL device that prevents a decrease in electrical characteristics of the device. SOLUTION: By providing a high dielectric constant organic binder layer between an insulating layer and a light-emitting layer, the sinking of a phosphor into the insulating layer is suppressed, uneven brightness and low power consumption are improved, and a high dielectric material having an appropriate dielectric constant is obtained. Improve brightness by selecting dielectric constant organic binder,
Organic dispersion type EL device that achieves long life.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to prevent the phosphor from sinking into the insulating layer, so that the brightness unevenness is extremely small.
The present invention relates to a low power consumption and long life organic dispersion type EL device.

[0002]

2. Description of the Related Art Heretofore, an organic dispersion type EL device has been used as a surface light source or a light emitting display device, for example, as a backlight of a liquid crystal display device because of its thinness, uniform light emission, light weight and the like. In addition, since large-area bodies are easy to manufacture, they are also used as backlights for signboards and signs, signboards, and the like. In general,
As shown in FIG. 1, the organic dispersion type EL element has a thickness of 10 μm in which a high dielectric constant inorganic substance such as barium titanate having a particle size of 1 to 10 μ is dispersed in a high dielectric constant organic binder on a back electrode such as an aluminum electrode 1. A dielectric layer 2 having a thickness of about 30 μm and a phosphor having a particle diameter of 10 to 50 μm dispersed in a high dielectric constant organic binder having a thickness of about 20 μm.
A 70 μm light-emitting layer 3 is sequentially laminated, and a transparent electrode 4 made of indium tin oxide (ITO) or the like formed on a transparent film such as PET is provided on the light-emitting layer. Fluoroethylene)
And sealed with a moisture-proof film 5. On the other hand, for example, JP-A-59-151799 and JP-A-2-90
It is also known from Japanese Patent Application Laid-Open No. 489/1989 and Japanese Patent Application Laid-Open No. 2-140992 that an organic binder layer is provided between a light emitting layer and a transparent electrode to increase the adhesive strength.

[0003]

According to the prior art,
When hot lamination is performed to bond the transparent electrode on the light emitting layer with sufficient adhesion, the phosphor sinks into the insulating layer due to the softening of the high dielectric constant organic binder, causing uneven brightness and current flowing through the light emitting layer. There is a problem that the power consumption is increased due to the increase in the value, and Japanese Patent Application Laid-Open No. 1-17091 discloses a method of improving the electrical characteristics by making the light emitting layer uneven. In addition, when the depression is extremely severe, the fluorescent substance reaches the rear electrode, and there is a risk of short-circuit and heat generation.
For example, JP-A-3-8292 discloses that an insulating layer and a fluorescent layer are formed on separate films and laminated so that both layers are in contact with each other. There is a description that an insulating powder is mixed and dispersed in a layer.

[0004]

SUMMARY OF THE INVENTION The present inventor has made various studies from the above-mentioned viewpoints, and has made it possible to provide a high dielectric constant organic binder layer between an insulating layer and a light emitting layer. In addition to suppressing the sinking of the phosphor into the insulating layer and improving uneven brightness and low power consumption, the selection of a high dielectric constant organic binder with an appropriate dielectric constant further improved the brightness and achieved long life. Things.

The present invention has been made based on the above findings. That is, (1) In the method of manufacturing an organic dispersion type EL device in which an insulating layer and a light emitting layer are sequentially laminated on a back electrode substrate, An organic dispersion-type EL device characterized in that a high dielectric constant organic binder layer is laminated between the organic light emitting layer and the light emitting layer, and (2) the dielectric constant of the high dielectric constant organic binder laminated between the insulating layer and the light emitting layer. A practically sufficient effect can be exhibited by the organic dispersion type EL element having a ratio of 10 or more.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments. This will be described with reference to the drawings. As shown in FIG. 2, an insulating layer 12, a high dielectric constant organic binder layer 13, and a light emitting layer 14 are sequentially laminated and coated on an aluminum foil 11 by a doctor blade method, and a trace amount of organic residue remaining on each layer is formed. Vacuum drying is performed to remove the solvent. Next, in order to increase the adhesive strength with the transparent electrode, pressing with a hot roll is performed to smooth the surface of the light emitting layer in advance (FIGS. 3-21, 22, and 2).
3, 24). Hereinafter, the light emitting layer and the transparent electrode, the lower part of the aluminum electrode, the upper part of the transparent electrode, and the water trapping film 6 are sequentially bonded by a hot roll press. Finally, the device is completed by sandwiching and laminating with a moisture-proof film
(FIGS. 4-31, 32, 33, 34).

The smoothing of the upper surface of the light emitting layer may be omitted depending on the type of the high dielectric constant organic binder used.
For example, it is applied to a binder having a high softening point, such as cyanoethylated pullulan, and having low adhesion to a transparent electrode. Light emitting layer, high dielectric constant organic binder used for the insulating layer, cyanoethylated pullulan, cyanoethylated saccharose,
Cyanoethylated cellulose, cyanoethylated polyvinyl alcohol, cyanoethylated hydroxysaccharose,
A cyanoethyl compound such as cyanoethylated hydroxycellulose or a polyfluoride resin such as polyvinylidene fluoride may be used, and the three layers may be the same or different. Further, a mixture thereof may be used.

Here, if the high dielectric constant organic binder layer 43 is not laminated, as shown in FIG. 5, after the smoothing, the fluorescent material sinks into the insulating layer 42 due to the softening of the high dielectric constant organic binder, as shown in FIG.
The light emitting layer thickness becomes uneven. This leads to an increase in power consumption due to uneven brightness and an increase in a current value flowing through the light emitting layer 44. Further, when the depression is extremely severe, the fluorescent substance reaches the rear electrode, which causes a short-circuit and generates heat, which is a serious problem in terms of safety. When the high dielectric constant organic binder layer 43 is provided between the insulating layer 42 and the light emitting layer 44, depression of the fluorescent material into the insulating layer is eliminated, and uneven brightness and increase in power consumption are suppressed, thereby extending the life of the element.

When the high dielectric constant organic binder layer is thin, the depression is not eliminated, and when it is thick, the depression is eliminated, but the luminance is reduced as the distance between the electrodes is largely divided. Although it depends on the kind of the binder, the thickness before vacuum drying and before smoothing is suitably 3 to 15 μm. A dielectric constant of 5 or more is appropriate. If it is smaller than 10, the brightness decreases. It is more preferably 15 or more, and the above-mentioned cyanoethyl compound or polyfluoride-based resin is preferable as the binder for the high dielectric constant organic binder layer. On the other hand, if the phosphor concentration in the light emitting layer is reduced to avoid the depression, the luminance is reduced. If the phosphor is made to have a small particle size, the life is significantly shortened.

[0010]

The present invention will be specifically described below with reference to examples and comparative examples. Example 1 67 parts by weight of barium titanate (average particle size: 5 μm), 10 parts of cyanoethylated pullulan, and 23 parts by weight of dimethylformamide were mixed and stirred to prepare a paste for an insulating layer, which was then placed on a 80 μm aluminum plate by a doctor. Coating was carried out by a blade method, followed by hot air drying at 130 ° C. for 3 minutes. Next, 35 parts by weight of cyanoethylated pullulan and 65 parts by weight of dimethylformamide were mixed and stirred, and a paste prepared for a high dielectric constant organic binder layer was applied in the same manner on the insulating layer, and heated at 130 ° C. for 3 minutes. Dried. Further Z
Phosphor activated with nS with Cu and Cl (average particle size 25μ)
55 parts by weight, 16 parts by weight of cyanoethylated pullulan and 29 parts by weight of dimethylformamide were mixed and stirred, and a paste prepared for a light emitting layer was coated on the high dielectric constant organic binder layer in the same manner. Hot air dried for minutes. This laminate was cut into a size of 10 cm × 15 cm and vacuum dried at 75 ° C. for 20 hours. In addition, after vacuum drying, the gap of the blade was adjusted in advance so that the insulating layer 25n, the high dielectric organic binder layer 5μ, and the light emitting layer 50μ were obtained. 150 ° C, 30K after drying
A metal hot roll press was performed under the conditions of gf / cm ² and 10 cm / min to smooth the surface of the light emitting layer. Then, a PET film transparent electrode was placed on the light emitting layer at 150 ° C. for 3 hours.
After bonding with a hot roll press under the conditions of 0 kgf / cm ² and 40 cm / min, the lower part of the aluminum foil and
A water catching film made of nylon was bonded on the PET film transparent electrode under the same conditions as those for bonding the transparent electrode. Finally, it was laminated with a moisture-proof film made of PCTFE to produce an organic dispersion type EL device.

[Comparative Example 1] An organic dispersion type EL device without an organic binder layer having a high dielectric constant was produced under the same conditions as in Example 1. However, the gap of the blade was previously adjusted so that the thickness of the light emitting layer after vacuum drying was 55 μm.

Comparative Example 2 An organic dispersion type EL device was prepared under the same conditions as in Example 1 except that the cyanoethylated pullulan in the high dielectric constant organic binder layer was changed to a mixed resin of a phenoxy resin and a cellulose resin having a dielectric constant of about 5. Produced.

The initial luminance and electrical characteristics of each of the organic dispersion type EL devices produced were measured (measurement conditions: 20 ° C., 65% R).
H). Further, an accelerated life test was performed in a constant temperature / humidity layer at 40 ° C. and 90% RH. 100V, 400Hz for both measurements
Was applied. After the completion of the accelerated test, the cross section of each element was observed under a microscope, and the presence or absence of the phosphor depressed in the insulating layer was confirmed. The results are summarized in Table 1. As can be seen from the table, it can be seen that the provision of the high-dielectric-constant organic binder improves the electrical characteristics and the life as compared with the case where no organic binder is provided. In addition, luminance unevenness was eliminated. The accelerated test life is a continuous lighting time until the luminance decreases to half of the initial luminance.

[0014]

[Table 1]

[0015]

As described above, an insulating layer, a high dielectric constant organic binder layer, and a light emitting layer are formed on an aluminum foil by the doctor blade on the back electrode substrate according to the present invention. Layer coating by vacuum drying and vacuum drying
The organic dispersion type EL device obtained by the process of smoothing the upper surface of the light emitting layer by pressing with a hot roll, laminating the water-absorbing film on the upper part of the transparent electrode and laminating the moisture-proof film has excellent brightness and electric power. It can be suitably used because it exhibits higher performance than conventional ones with its characteristics and long life.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a conventional organic dispersion type EL element.

FIG. 2 is a cross-sectional view showing the steps of a laminated structure of the organic dispersion type EL element of the present invention.

FIG. 3 is a cross-sectional view showing the smoothing of the upper part of the light emitting layer by the hot roll of the present invention.

FIG. 4 is a completed sectional view showing a laminated structure of the organic dispersion type EL element of the present invention.

FIG. 5 is a cross-sectional view showing an explanation of each performance by the laminated structure of the present invention.

[Explanation of symbols]

1-aluminum electrode, 2-dielectric layer, 3-light-emitting layer, 4-transparent electrode, 5-moisture-proof film, 6-water catching film, 11,2
1, 31, 41-aluminum electrode, 12, 22, 32, 42
-Insulating layer, 13, 23, 33, 43-High dielectric constant organic binder, 14, 24, 34, 44-Light emitting layer.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Minoru Kanda 1-297 Kitabukurocho, Omiya City, Saitama Prefecture Inside Mitsubishi Materials Research Institute (72) Inventor Masaharu Ishiwata 1-297 Kitabukurocho, Omiya City, Saitama Mitsubishi Materials 3K007 AB00 AB02 AB05 BB01 BB05 CB01 DA04 DA05 EB04 EC01 FA01

Claims (2)

[Claims] 1. An organic dispersion type EL device in which an insulating layer and a light emitting layer are sequentially laminated on a back electrode substrate, wherein an organic binder layer having a high dielectric constant is laminated between the insulating layer and the light emitting layer. Type EL element. 2. The organic dispersion type EL device according to claim 1, wherein the high dielectric constant organic binder has a dielectric constant of 10 or more.