JPS647476B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroluminescent device that emits electroluminescence by applying a voltage, and particularly to a distributed electroluminescent device that emits high-intensity light.

FIG. 1 is a cross-sectional view showing the structure of a conventional dispersion type electroluminescent device, in which 1 is a transparent glass substrate that constitutes the display surface, and 2 is a film of tin oxide as an electrode material on the glass substrate 1 with a thickness of about 2000 Å. Transparent electrodes formed using electron beam evaporation and heat treatment.
3 is a fluorescent layer to be described later; 4 is a metal back electrode having reflective properties formed by forming aluminum on the fluorescent layer 3 to a thickness of about 2000 Å by electron beam evaporation; these glass substrate 1, transparent electrode 2, The fluorescent layer 3 and the back electrode 4 are distributed electroluminescent cells (hereinafter abbreviated as EL cells).
5. 6 is a cover made of polycarbonate resin that hermetically surrounds the EL cell 5 except for the display surface part of the EL cell 5, but this cover 6 is made of metal or glass other than the resin as long as gas leakage does not occur. Any shape is acceptable, and as long as only the portion facing the display surface is transparent, the shape may surround the entire EL cell 5.

By the way, the phosphor layer 5 is made by dispersing a phosphor added with an active material and an activating material to form a luminescent center in a base material, and a dielectric material having a high dielectric constant and serving as a binder. The resulting paste-like material is formed into a film with a thickness of about 10 μm using a silk screen method. For example, zinc sulfide is used as the base material, copper is used as the active material, aluminum is used as the activating material, and cyanoethylhydrocytic cellulose, acrylic, and epoxy are used as the dielectric material. Resins such as are used.

In such a configuration, by applying a regular alternating current voltage of several KHz between the electrodes 2 and 4, an electric field generated in the phosphor layer 3 excites electrons in copper, which is the luminescent center, and produces a fringe color. Electroluminescence is generated, and the light rays from this emission are irradiated to the outside through the glass substrate 1 either directly or reflected by the back electrode 4.

This invention makes full use of technical means to enable even higher luminance in the dispersion type electroluminescent device having the above structure. By adding a silane coupling agent, the state of the bonding interface between the phosphor and the dielectric is improved to provide an electroluminescent device with high emission intensity.

Examples of this invention will be described below.

FIG. 2 is a sectional view showing the structure of a distributed electroluminescent device according to this embodiment, and the glass substrate 1, transparent electrode 2, back electrode 4, and case 6 are made of the same materials as in the conventional example shown in FIG. It is used under the same conditions and is characterized by the fluorescent layer 30 forming part of the structure of the EL cell 50.
It is in.

As a result of detailed observation and analysis of the emission state of the conventional phosphor layer 3 made of a phosphor and a dielectric, it was found that the phosphor layer 3 in which the polarity of the bonding interface between the phosphor and the dielectric is uniform has a higher emission intensity. It turned out that it was possible to obtain

In this invention, a silane coupling agent is added to a fluorescent material consisting of a fluorescent material and a dielectric material to make active use of this phenomenon, thereby forcing the polarity of the bonding interface between the fluorescent material and the dielectric material. The phosphor layer 30 was formed by applying the film to a thickness of about 10 μm on the transparent electrode 2 by a silk screen method, and then heat-treating it at about 100° C.

FIG. 3 shows that in a distributed electroluminescent device having such a configuration, the phosphor in the phosphor layer 30 includes:
An active material made of copper and an activated material made of aluminum are added to a base material made of zinc sulfide, and an epoxy resin is used as a dielectric material to serve as a binder, and a silane coupling is inserted into these fluorescent materials. This is a diagram showing the relationship between the applied voltage and the luminescence brightness measured by varying the amount of the silane coupling agent added, and the number on the right side indicates the amount of the silane coupling agent added.

This reduces the amount of silane coupling agent added.
It can be seen that when the amount exceeds 5 wt%, the emission starting voltage becomes low, the emission brightness increases with respect to the application of the same value of voltage, and the maximum emission brightness that is finally reached also becomes high.

Note that if the amount of silane coupling agent added exceeds a certain value, the terminal voltage supply between both electrodes 2 and 4 of the EL cell 50 will decrease and the current density will increase, so there is a limit to the amount of silane coupling agent added. In this example, the above phenomenon was observed when the content exceeded 23 wt%.

In this way, in a dispersed electroluminescent device having a phosphor layer made of a phosphor and a dielectric as part of its structure, the phosphor is embedded in a silane cup within a phosphor made of a dielectric. By adding an appropriate amount of ring agent, i.e. 5 to 23 wt%, to form a phosphor layer, the polarity of the bonding interface between the phosphor and dielectric is aligned, and they are firmly bonded to each other within the phosphor layer. Therefore, compared to the conventional structure, it is possible to emit light at a lower voltage, and the effect is that the light emission brightness increases when the same value of voltage is applied, and the maximum light emission brightness that is finally reached is also increased. A display element with good contrast can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of a conventional distributed electroluminescent device, FIG. 2 is a cross-sectional view showing the structure of a distributed electroluminescent device according to an embodiment of the present invention, and FIG. FIG. 2 is a characteristic diagram showing the relationship between luminance and luminance applied to an electroluminescent element. 1: Glass substrate, 2: Transparent electrode, 30: Fluorescent layer, 4: Back electrode.

Claims (1)

[Claims] 1. In a dispersed electroluminescent device having a fluorescent layer that emits electroluminescence when a voltage is applied, 5 to 23 ωt% of a silane coupling agent is contained in the phosphor and dielectric that constitute the fluorescent layer. An electroluminescent device characterized by the addition of additives.