JPH0254896A - Electroluminescence element - Google Patents

Abstract

PURPOSE:To obtain a higher brightness of a light emitting element by constituting at least one of organic binders forming the insulating layer and luminescent layer of the element of a binder material having a small dielectric loss. CONSTITUTION:An electroluminescence light emitting element 1 has a structure in which a laminated body 6 is formed by successively laminating a back plate 2, an insulating layer 3, a luminescent layer 4 and a transparent electrode 5, and the both front and back surfaces of the laminated body 6 are sealed by tranaparent package films 7, 7. The layer 3 of this element 1 is formed by dispersing and mixing an insulating material to an organic material composed of a binder material having a small dielectric loss. The layer 4 is formed by dispersing and mixing a luminescent material to the organic binder composed of the same binder material. Hence, this element 1 can be stably driven by applying a high frequency thereto, and the brightness of the element 1 can be increased much more.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electroluminescent element that is mainly incorporated into a liquid crystal display device and used as a backlight (backlight).

<Prior Art> Conventionally, this type of electroluminescent device has been constructed by sequentially laminating a back electrode, an insulating layer, a light-emitting layer, and a transparent electrode to form a laminate, and the front and back surfaces of this laminate are covered with a pair of layers. It is known to have a cross-sectional structure sealed with a transparent package film as a resin jacket. The insulating layer of this electroluminescent device is constructed by dispersing an insulating material made of barium titanate into an organic binder made of a binder material such as cyanoethyl cellulose or cyanoethyl pullulan, and the light emitting layer is made of zinc sulfide. It is common to be constructed by dispersing and mixing a luminescent material whose main component is strontium sulfide or the like into an organic binder made of the same binder material as described above.

The reason why cyanoethyl cellulose and cyanoethyl pullulan are used as such organic binders is that these binder materials have a large dielectric constant. This is based on the fact that a high voltage can be applied between the electroluminescent element and the electric field applied to the luminescent particles in the luminescent layer, thereby increasing the brightness of the electroluminescent element.

<Problems to be Solved by the Invention> Incidentally, in order to achieve high brightness of the electroluminescent device, it is necessary to increase the voltage applied to it, but this requires a large power supply. This has the disadvantage of increasing the cost and increasing the space required to incorporate the electroluminescent device into electronic equipment.

Therefore, in order to avoid such inconveniences, it is possible to improve the brightness of electroluminescent devices by applying high frequency waves, but cyanoethyl cellulose and cyanoethyl pullulan, which are common binder materials used as organic binders, can be considered. has a large dielectric constant and a large dielectric loss (ta
n δ), it would be destroyed if a high frequency higher than a predetermined value was applied and driven, which was not practical.

The present invention was created in view of such circumstances, and
The present invention aims to provide an electroluminescent device that can be driven stably by applying high frequency and that can reduce the size of the power supply. In order to achieve the purpose, in an electroluminescent device in which an insulating layer and a light-emitting layer are laminated between a pair of electrodes and integrally sealed with a resin jacket, the insulating layer and the light-emitting layer constitute the The present invention is characterized in that at least one of the hammer binders is made of a binder material with low dielectric loss. Note that the dielectric loss of the binder material at a frequency of 10 KHz is preferably 104 or less.

Effects> According to the above structure, at least one of the binder forming the insulating layer and the light emitting layer of the electroluminescent element is made of mTA... a binder material with low loss, so that the electroluminescent element is It is possible to drive by applying a higher frequency than the above, which makes it possible to achieve even higher brightness and to reduce the size of the power supply.

<Example> Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a cross-sectional view showing the schematic structure of an electroluminescent device.
This electroluminescent device 1 includes a back electrode 2, an insulating layer 3, and a light emitting layer 4.
A laminate 6 is constructed by sequentially laminating the laminate 6 and the transparent electrode 5, and both the front and back surfaces of the laminate 6 are sealed with a pair of transparent puff cage films 7.7 serving as resin jackets. The back electrode 2 of this electroluminescent element 1 is formed from a metal foil such as aluminum or nickel, and the back electrode 2 is made of an electrode film such as indium/tin oxide (CITO) on the inner surface of a transparent polyester film 5a or the like. 5
b.

On the other hand, the insulating layer 3 of this electroluminescent device 1 is made of an insulating material made of barium titanate and an organic binder made of one of the binder materials with small dielectric loss (tan δ) shown in Table 1 (see next page). The light-emitting layer 4 is made by dispersing and mixing a luminescent material containing zinc sulfide, strontium sulfide, etc. as a main component into an organic binder made of the binder materials shown in Table 1. It is made up of.

Table 1 Table 1 indicates that the dielectric loss is small, that is, the dielectric loss at a frequency of 10 KHz is at least 10-
``The table below lists examples of binder materials, and in this table, cyanoethyl pullulan, which is a conventionally used general binder material, is listed for comparison.

Next, using polystyrene in Table 1 as an example of a binder material with small dielectric loss, the insulation N3 and the light emitting layer 4 are prepared.
A specific example of configuring this will be explained.

First, to form the insulating layer 3, for example, green zinc sulfide 1i (ZnS:Cu) powder and granular polystyrene are mixed so that their weight ratio is 4=1. An insulating paste is formed by dispersing the mixture in methyl ketone or toluene as a solvent. Then, this insulating paste is printed directly on the back electrode 2 and dried, or it is formed into a sheet shape in advance and then laminated by thermocompression bonding. On the other hand, when forming the light-emitting layer 4, barium titanate (BaTi03) powder and granular polystyrene are mixed at a weight ratio of 3:1 and dispersed in the above solvent to emit light. After forming the paste, it is laminated by the same method as above.

By the way, when the inventors of the present invention conducted a characteristic experiment on the relationship between the applied frequency and the luminance of the electroluminescent device having the structure described above and the electroluminescent device having the conventional structure, it was found that in the conventional product, Frequency 10-2
It has been revealed that, whereas element destruction occurs when a voltage of 0 KHz is applied, the product of the present invention can be driven stably even when a high frequency of 50 to 60 KHz is applied.

<Effects of the Invention> As explained above, according to the present invention, at least one of the organic binders constituting the insulating layer and the light emitting layer of the electroluminescent element is made of a binder material with small dielectric loss, so that the electroluminescent It is possible to apply a higher frequency to the element than in the conventional example and drive it stably. and,
This has the effect that not only can the brightness of the electroluminescent element be further increased, but also the power supply can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a schematic structure of an electroluminescent device according to the present invention. In the figure, reference numeral 1 is an electroluminescent element, 2 is a back electrode, 3 is an insulating layer, 4 is a light emitting layer, 5 is a transparent electric bridge, and 7 is a transparent package film (resin jacket).

Claims (1)

[Claims] (1) In an electroluminescent device in which an insulating layer and a light emitting layer are laminated between a pair of electrodes and integrally sealed with a resin jacket, at least one of the organic binders constituting the insulating layer and the light emitting layer is used. An electroluminescent device characterized in that one side is made of a binder material with low dielectric loss.