JPH04351883A - Manufacture of dispersion type electroluminescence element - Google Patents

Abstract

PURPOSE:To increase a light lead-through efficiency for a dispersion type electroluminescence element by increasing a glossiness (a reflection factor) of an insulation layer. CONSTITUTION:In an insulation layer applying process for a dispersion type electroluminescence element, drying to an insulation layer 24 is set to be low- temperature delayed drying at 30 deg.C-50 deg.C, so the irregularity in the surface of applied ink is let to flow to be smooth. The glossiness at the surface of the insulation layer is thus increased to increase a reflection factor, thereby a light lead-through efficiency for the dispersion type electroluminescence element is increased.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a distributed EL device, and more particularly to a method for coating and drying an insulating layer.

0002

2. Description of the Related Art A conventional method for manufacturing a distributed EL element will be described. An insulating layer ink made by dispersing a high dielectric powder such as barium titanate in an organic binder such as cyanoethyl cellulose dissolved in an organic solvent such as dimethyl formamide is applied onto a back electrode made of aluminum foil, etc., and then dried. an insulating layer formed using zinc sulfide, a light-emitting layer consisting of a phosphor made of zinc sulfide as a matrix and activated with copper etc. dispersed in an organic binder such as sial ethyl cellulose, and an ITO layer.
After sequentially laminating transparent electrodes made of materials such as the Fabricate the element. These distributed EL elements are thin, flexible, easy to handle, and can be manufactured at relatively low cost, so they have recently become rapidly popular as backlights for laptop-type word processors and liquid crystal display devices for personal computers.

0003

However, in the above manufacturing method, after applying the ink for the insulating layer, hot air drying is performed at 100° C. for about 1 hour, so the organic solvent quickly evaporates and the drying is completed. Therefore, the uneven portions generated immediately after coating remain on the surface of the insulating layer and solidify, reducing the reflectance of the surface. When such a distributed EL element emits light, the insulating layer has a low reflectance, so there is a problem in that the efficiency of extracting light to the outside of the element is low and sufficient brightness cannot be obtained.

0004

[Means for Solving the Problems] In order to solve the above problems, the present invention performs delayed drying at a low temperature (for example, 30°C to 50°C) after applying an ink for an insulating layer on a back electrode and before main drying. This suppresses the rapid evaporation of the organic solvent and smoothes the surface of the insulating layer by fluidizing and reducing the unevenness that has formed on the surface immediately after application over time. do.

[0005]

[Function] According to the above method, when forming an insulating layer by coating, it is gradually dried at a low temperature after coating, so rapid evaporation of the organic solvent can be suppressed, and during this time, the irregularities on the coated surface will not flow. As a result, the reflectance of the surface of the insulating layer is improved and the light extraction efficiency of the dispersion type EL element is improved.

[0006]

EXAMPLES A method of manufacturing a distributed EL device according to the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 2 shows a distributed EL according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of main parts showing the structure of the element. In Figure 2, 3
4 is a light-emitting layer in which a phosphor (for example, zinc sulfide activated with copper) is dispersed in an organic binder such as cyanoethyl cellulose, and 4 is a light emitting layer in which a high dielectric powder such as barium titanate is dispersed in an organic binder such as cyanoethyl cellulose. The transparent electrode is formed by forming a transparent electrode layer 2 such as ITO on a transparent electrode substrate 1 made of polyester film by a method such as vapor deposition, and the back electrode substrate 5 is made of aluminum foil, for example. An insulating layer 4 is formed thereon. 6 is a moisture-absorbing film made of nylon or the like, and 7 is a moisture-proof protective film for sealing made of polyethylene trifluoride, for example. Leads not shown. In the manufacturing method of the dispersion type EL element 8 having the above structure, the manufacturing method of the present invention that is most different from the conventional method and is characteristic is the method of forming an insulating layer, and especially the drying method immediately after coating.

Next, a method for coating and drying an insulating layer according to the present invention will be explained with reference to FIG.

FIG. 1 is an enlarged sectional view of a main part of an insulating layer corresponding to the insulating layer coating and drying process of the present invention. FIG. 1(a) shows the state of the insulating layer during coating, FIG. 1(b) shows the state of the insulating layer during low-temperature delayed drying, and FIG. 1(c) shows the state of the insulating layer during main drying. In this example, a doctor blade method is used as the coating method. 21 is a doctor blade, 22 is an insulating layer ink, 23 is an aluminum foil,
24 indicates an insulating layer. The gap between the aluminum foil 23 and the doctor blade 21 is about 270 μm.

First, on the aluminum foil 23, an insulating layer is prepared by dispersing a high dielectric powder such as barium titanate at a predetermined ratio in a solution of an organic binder such as cyanoethyl pullulan in an organic solvent dimethylformamide. The ink 22 is printed using a doctor blade method to form an insulating layer 24. The arrow indicates the direction of movement of the doctor blade. Immediately after coating, the surface of the insulating layer has irregularities as shown in FIG. 1(a). Next, low temperature delayed drying is performed in a drying oven set at 30°C to 50°C. In this low-temperature drying, the organic solvent is gradually evaporated, so that the insulating layer 24 is smoothed by flowing, and uneven portions are eliminated (FIG. 1(b)). Continue low temperature drying until most of the organic solvent has evaporated.

Next, main drying is performed in a drying oven set at 100°C. In the main drying process, almost no flow of the insulating layer 24 occurs, and the slight remaining dimethylformamide and water almost completely evaporate, the insulating layer shrinks and solidifies, and an insulating layer of 40 μm to 50 μm is finally formed. (Figure 1 (
c)).

The steps from the next step to the completion of the device are the same as those of the conventional method, so their explanation will be omitted.

Table 1 shows a comparison of the measurement results of the luminous efficiency and the glossiness of the insulating layer for the dispersion type EL device produced by the low temperature delayed drying method of the present invention and the conventional device without low temperature drying.

[0014]

[Table 1]

[0015]

[0016] The glossiness is 60° glossiness according to the JIS standard. The glossiness can be used as a barometer when evaluating the surface reflectance of the insulating layer. Luminous efficiency is 400Hz
This is the value when the brightness is 100 cd/square meter. As is clear from Table 1, the present invention has higher gloss and superior luminous efficiency than the conventional method. This indicates that low-temperature drying improved the reflectance of the insulating layer surface and improved the light extraction efficiency. In addition, because it was gradually dried at a low temperature, voids were less likely to occur in the organic binder or at the boundary with the phosphor, which may have improved efficiency. here,
When the drying temperature is lower than 30° C., the drying time becomes significantly longer and the efficiency of production decreases. Furthermore, if the temperature is higher than 50°C, drying will be rapid and surface irregularities will remain, reducing the effect of the present invention. In the above embodiments, the insulating layer was printed using a doctor blade method, but the present invention is also applicable to other methods such as screen printing. Further, in the above embodiment, high temperature main drying was performed after low temperature delayed drying, but only low temperature delayed drying may be performed without performing main drying.

[0017]

Effects of the Invention According to the manufacturing method of the present invention, since the insulating layer is gradually dried at a low temperature after being applied, rapid evaporation of the organic solvent is suppressed and the organic solvent evaporates gradually. It has the effect of providing a high-performance dispersion type EL element that flows and becomes smooth, improves the reflectance of the surface of the insulating layer, and improves the light extraction efficiency. Note that the distributed EL according to the present invention
The device is suitable for backlighting of liquid crystal display devices installed in laptop-type word processors and personal computers, which are desirably used with low power consumption.

[Brief explanation of drawings]

FIG. 1: An enlarged cross-sectional view of essential parts for explaining the insulating layer coating and drying process of the present invention and the corresponding surface state of the insulating layer.

[
FIG. 2 A cross-sectional view of main parts showing the structure of the distributed EL element according to the present invention

[Explanation of symbols]

1 Transparent electrode substrate 2 Transparent electrode layer 3. Luminescent layer 4, 24 Insulating layer 5　Back electrode substrate 6 Moisture absorbing film 7 Moisture-proof protective film 8 Distributed EL element 21 Doctor Blade 22 Ink for insulation layer 23 Aluminum foil

Claims (3)

[Claims] 1. A step of coating an insulating layer and a light emitting layer on a back electrode, laminating a transparent electrode on the light emitting layer, and comprising:
a step of leading out leads from the back electrode and the transparent electrode;
In a method for manufacturing a distributed EL element, the method includes the step of hermetically sealing the laminate from which the leads have been led out with a moisture-proof film,
A method for manufacturing a dispersed EL element, characterized in that a low temperature delayed drying step is provided immediately after coating an insulating layer. 2. The method for manufacturing a distributed EL device according to claim 1, wherein the low-temperature delayed drying is performed at a temperature of 30° C. to 50° C. 3. The method for manufacturing a distributed EL device according to claim 1, wherein a main drying step is provided after the low temperature delayed drying.