JP2772339B2 - Color EL display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color EL display device used as a display backlight in various devices.

[0002]

2. Description of the Related Art A color EL display device in the prior art is a color light-emitting device in which a color luminous body is added to a transparent conductive film made of a polyethylene terephthalate (hereinafter referred to as "PET") film in addition to a usual fluorescent pigment on an ITO-deposited surface. A color display of about eight colors is obtained by using a layer formed on the insulating layer, the back electrode layer, and the protective layer in this order.

On the other hand, recently, as a means for increasing the variation of the emission color, a fluorescent color ink layer is formed outside the transparent conductive film and a color filter is applied.

[0004]

In the above prior art, when a color phosphor is added to a light emitting layer of an EL display device to form a color light emitting layer, an ink in which a binder and a usual fluorescent pigment are mixed is used. The types of color phosphors having excellent dispersibility and coloring properties are limited, and therefore, there is a disadvantage that the types capable of color display are scarce. In addition, when a color film is arranged outside the transparent conductive film in order to increase the variation of the emission color, the emission luminance is reduced by that amount, and it is necessary to drive at a higher voltage to obtain a desired luminance. A problem has arisen in the use of small devices such as watches with limited capacity.
The fluorescent color ink layer is disadvantageous in that it rapidly deteriorates due to ultraviolet rays or the like, and is limited in use in an environment where it is exposed to direct sunlight.

Accordingly, an object of the present invention is to provide a color EL display device capable of obtaining desired light emission for a long period of time by limiting the types of colors that can be realized and by suppressing fading of the fluorescent color ink layer. is there.

[0006]

In order to achieve the above object, a color EL display device of the present invention is provided by adding a fluorescent pigment of a predetermined color and cerium oxide to one surface of a transparent film in a binder. The fluorescent color sheet has a fluorescent color ink layer formed thereon, and the fluorescent color sheet is stacked on the EL panel with the fluorescent color ink layer facing inward. 5 to 50 for the fluorescent pigment binder 100g
g of cerium oxide and binder 1
It is added at a ratio of 0.5 to 20 g with respect to 00 g.

The thickness of the fluorescent color ink layer is 4 to 30 μm.
Ru Tei is formed on.

[0008] good Mashiku, the fluorescent color ink layer of the ultraviolet absorbing agent is added, the accompanying amount of UV absorber ratio of 0.5~20g is preferred for the binder 100 g.

[0011] As the ultraviolet absorber, any one of the benzotriazole-based ultraviolet absorber or a cyanoacrylate ultraviolet absorber or salicylic acid ultraviolet absorber or benzophenone ultraviolet absorber is suitable.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A color EL display device according to the present invention
One side of the transparent film, one side of the binder,
Add fluorescent pigment and cerium oxide of specified colors to
Color sheet having a fluorescent color ink layer formed thereon
The fluorescent color sheet has a fluorescent color ink layer inside.
On the EL panel with the fluorescent pigment
5 to 50 g per 100 g
Cerium oxide is 0.5 to 100 g of binder.
20 g of the fluorescent color ink layer.
The layer thickness is formed to 4 to 30 μm.

[0011]

[Example] it will be described with reference to the drawings attached to this onset Akira below. The structure of the color EL display device of the present invention will be described with reference to the conceptual diagram shown in FIG.
A transparent electrode layer (not shown) formed by depositing ITO is formed thereon, and a luminescent layer 2 is formed by printing a luminescent ink on the transparent electrode layer. As the luminescent ink, zinc sulfide (ZnS) doped with copper (Cu) is used as a phosphor, and as a binder of the luminescent ink, a mixture of a fluorine resin and n-butyl carbitol acetate is used. The luminescent ink is prepared by mixing and stirring the two.

An insulating layer 3 formed by printing insulating ink is formed on the upper surface of the light emitting layer 2. The insulating ink is obtained by mixing barium titanate (BaTiO ₃ ), which is a high dielectric substance, with a binder obtained by mixing a fluororesin and n-butyl carbitol acetate, and thoroughly stirring the mixture. The insulating layer 3 is formed by printing insulating ink on the light emitting layer 2 by screen printing, and then heating and drying. In this way,
The binder containing the fluorine resin and the insulating layer 3 prevent moisture from entering the light emitting layer 2 and adjust a desired dielectric constant of the EL display device.

A back electrode layer 4 is formed on the upper surface of the insulating layer 3. The back electrode layer 4 is formed by printing a conductive ink obtained by mixing a carbon powder as a conductor with a polyester resin. Examples of conductive ink include polyester resin 8
0 g, carbon powder 10 g and binder 10 g
The mixture is used in the ratio of

On the upper surface of the back electrode layer 4, a protective layer (moisture-proof layer) 5 made of silicone resin is formed by printing.

On the light emitting surface side (transparent conductive film 1 side) of the EL panel A having the above structure, a fluorescent color sheet B having the following structure is provided. The fluorescent color sheet B is provided with a fluorescent color ink layer 6 serving as a color filter on one surface of a transparent film 7 such as PET, and the fluorescent color ink layer 6 is formed by printing fluorescent color ink on the transparent film 7 by screen printing. And is stacked on the EL panel A with the inside facing inward.

Example 1 In this example, the fluorescent color ink used was a mixture of a fluororesin and n-butyl carbitol acetate in a weight ratio of 25:75 as a binder. It is made by adding 3 g of cerium oxide and 30 g of fluorescent pigment.

The amount of the fluorescent pigment to be added to the fluorescent color ink is suitably 5 to 50 g per 100 g of the binder. This is because the color obtained when the fluorescent pigment is dispersed in the binder is beautifully finished between 5 and 50 g. When the amount of the fluorescent pigment to be added exceeds 50 g, which is the upper limit, it is necessary to consider the solubility of the fluorescent pigment in the binder.

The amount of cerium oxide added to the fluorescent color ink is 0.5 to 2 with respect to 100 g of the binder.
0 g is appropriate. Cerium oxide has a high ultraviolet absorbing property and thus functions to prevent deterioration due to ultraviolet rays. However, when the amount of cerium oxide added is less than 0.5 g with respect to 100 g of the binder, the fluorescent color ink layer
Cannot be expected, and if it exceeds 20 g, it becomes impossible to obtain clear light emission of the color of the fluorescent color ink layer 6.

In the fluorescent color sheet B, since the fluorescent color ink layer 6 is provided facing inward, the fluorescent color ink layer 6 is not directly exposed to the outside air. Thereby, the deterioration of the fluorescent color ink layer 6 is more reliably suppressed.

In this embodiment, the fluorescent color ink layer 6 is formed to have a thickness of 4 to 30 μm. 4 layer thickness
If it is less than μm, a satisfactory fluorescent color cannot be obtained, and the EL panel A on the back side can be seen through to lower the display quality. Conversely, if it exceeds 30 μm,
The light transmittance is reduced, and the function as a backlight type color EL display device is lost.

In the above embodiment, the addition of cerium oxide enhances the absorption of ultraviolet light to prevent deterioration due to ultraviolet light.
A range of 5 to 20 g is suitable. Therefore, an example in which an ultraviolet absorber is added in addition to the addition of cerium oxide in order to further increase the light resistance to ultraviolet light will be described below.

Example 2 In this example, 3 g of cerium oxide and 3 g of fluorescent pigment were added to 100 g of a binder in the same manner as in Example 1.
0 g, and 3 g of an ultraviolet absorber. The fluorescent color ink is printed on a transparent film 7 to form a fluorescent color ink layer 6.

Examples of the UV absorber include benzo such as 2,2-methylenebis {4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol}. Triazole-based UV absorber, 2
Cyanoacrylate-based ultraviolet absorbers such as -ethylhexyl-2-cyano-3,3'-diphenylacrylate;
Salicylic acid-based ultraviolet absorbers such as phenyl salicylate,
A benzophenone-based ultraviolet absorber such as 2,4-dihydroxybenzophenone is used.

FIG. 2 is a graph comparing the luminance retention ratios of the color EL display devices subjected to a color fading test (light fastness test) by irradiation with ultraviolet rays, and is prepared from the data in Table 1 obtained as a result of the tests. A is a conventional example (without addition of both), B is Example 1 (with cerium oxide added), which is a color EL display device of the present invention, and C is Example 2.
(To which cerium oxide and an ultraviolet absorber are added) are shown.

The above data shows that the light source has a strongest spectrum of 365 nm, a lamp power of 400 W, and a luminance of 450 cd /.
This was obtained from an experiment conducted using a mercury lamp of cm ^{2 and} a pink fluorescent pigment as the ink of the fluorescent color ink layer 6.

[0026]

[Table 1]

As can be seen from Table 1 and FIG. 2, the difference in the luminance maintenance ratio starts to increase from around 30 hours when the irradiation time is around 30 hours.
At 0 hours there is a considerable difference. That is, after 200 hours of irradiation time, in the second embodiment, the brightness maintenance ratio 108
%, The lightfastness is remarkably excellent, with almost no color fading. In contrast, in Example 1, a slight fading was observed at 138%. Is obtained.

In the second embodiment, the EL panel A itself emits blue green light, but when the color of the fluorescent color ink layer 6 thereon is pink, if the color of the fluorescent color ink layer 6 is dark, the fluorescent light is almost unchanged. Light emission is displayed in the color (pink) of the color ink layer 6. On the other hand, if the color of the fluorescent color ink layer 6 is light pink, white emission is obtained by acting on the blue-green emission of the EL panel A. Thus, what kind of luminescent color is finally obtained can be appropriately determined according to the relationship between the luminescent color of the EL panel A, the color of the fluorescent color ink layer 6, and the color depth of both.

The fluororesin binder used for the light emitting layer and the insulating layer is a polymer of vinylidene fluoride such as polyfluoroethylene, vinyl fluoride, ethylene trifluoride, ethylene trifluoride ethylene, or propylene hexafluoride. Or 1
You may use the copolymer which can copolymerize more than 2 types. Also,
As the phosphor, zinc sulfide doped with Cu is used, and the phosphor is made of SiO ₂ , TiO ₂ , Al ₂ O in advance.
A material coated with an inorganic transparent dielectric material such as ₃ may be used. Further, the protective layer may be a moisture-proof layer made of fluororesin instead of silicon resin.

[0030]

According to the present invention, since the fluorescent color sheet is superposed on the EL panel with the fluorescent color ink layer facing inward, the fluorescent color ink layer is not directly exposed to the outside air, and the color fading is suppressed. Moreover, as a fluorescent color ink layer,
Since a binder and a fluorescent pigment to which cerium oxide is added are employed, it is possible to maintain luminance without fading even when used for a long time. Also, the fluorescent pigment and cerium oxide are added at a ratio of 5 to 50 g and 0.5 to 20 g, respectively, to 100 g of the binder.
Thus, it is possible to form a fluorescent color ink layer that can obtain both a good fading prevention effect and a clear emission color. And
To form the layer thickness of the fluorescent color ink layer 4~30μm
Runode, Ru der can be beautiful color displayed by the EL panel and the combination Rukoto.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram showing a comparison of a luminance maintenance ratio between a conventional example and this embodiment.

[Explanation of symbols]

 6 Fluorescent color ink layer 7 Transparent film A EL panel B Fluorescent color sheet

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Koji Yoneda, Inventor Koji Yoneda 4-1-1, Sumida-ku, Tokyo Inside Seikosha Co., Ltd. (56) References JP-A-4-298989 (JP, A) JP-A-2 -288186 (JP, A) JP-A-6-275380 (JP, A) JP-A-6-23195 (JP, U)

Claims (1)

(57) [Claims] 1. A fluorescent color sheet having a fluorescent color ink layer formed by adding a fluorescent pigment of a predetermined color and cerium oxide to a binder on one surface of a transparent film, wherein the fluorescent color sheet is 5-50 the fluorescent color ink layer Ah Ri superimposed on EL panel inwardly, the fluorescent pigment for the binder 100g
g of cerium oxide and 0.1 g of the cerium oxide per 100 g of the binder.
Are added in a proportion of 5 to 20 g, the thickness of the fluorescent color ink layer is formed on 4~30μm
Color EL display device characterized by being.