JPH0135350B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a novel electroluminescent display element.

(Prior Art and Problems) FIG. 1 is a sectional view of a conventional electroluminescent display element (hereinafter referred to as an EL display element).

In the figure, 1 is a transparent insulating film made of an organic transparent film, etc., and 2 is formed by vapor-depositing mesh-shaped gold, aluminum, ITO (a transparent metal oxide made by doping indium oxide with SnO ₂ ), etc. on the transparent insulating film 1. electroluminescent light (below)
The transparent electrode 3, which is capable of transmitting EL light (referred to as EL light), is an organically bonded phosphor powder made by injecting an activator such as copper or manganese and an activator such as chlorine or bromine into zinc sulfide or zinc selenide. a phosphor layer dispersed in an adhesive;
4 is a dielectric layer in which high dielectric constant powder such as titanium oxide or barium titanate is dispersed in an organic binder, and 5 is a counter electrode using aluminum or gold foil, for example. 6
is a transparent protective film that protects the interior from moisture.

In such a configuration, when a DC or AC voltage is applied between the transparent electrode 2 and the counter electrode 5, the phosphor layer 3 emits light. The larger the applied voltage, the higher the luminance, and the higher the power frequency, the higher the luminance. Usually, in an EL display element, electrodes are formed on the entire surface of the display surface, so the entire surface of the display surface emits light when a voltage is applied.

The EL display element is often used in self-illuminated panel switches and display panels for visually recognizing various functions. For such applications, it is important that figures, characters, etc. be clearly visible when the lights are on, and that in an emergency the entire display surface is blank and not displayed at all, and such a display has been desired. Therefore,
Protective film 6 for EL display element that emits light on the entire surface
The display is displayed by printing the display content with ink or the like, or pasting a printed masking film (the display content is transparent and the surrounding area is opaque, or the display content is opaque and the surrounding area is transparent). Protective film 6 with display contents printed on transparent insulating film 1
or after printing display contents with ink or the like on the transparent insulating film 1, the whole is covered with a protective film 6. Electrodes are formed in the required display pattern by etching or the like. Such methods have been used.

However, in the method shown in , the unmasked parts of the masking film are transparent, so
When observing the EL display element with no voltage applied, the background color of the phosphor layer 3 is visible, and conversely, the printed color is visible in the masked area, making it difficult to distinguish between the printed color and the phosphor layer 3. Unless the same color is selected, there will be a difference in color tone between the masked area and the unmasked area, and for this reason, the display content of the EL display element will be clearly displayed regardless of whether the EL display element is lit, and when it is lit. The difference between the display and the time when the light is off becomes so small that it becomes difficult to distinguish between the light on and the light off. In order to solve this problem, in recent display displays, a translucent green-gray smoke film, for example, is placed on the display element so that the displayed content cannot be seen when the light is off, but the display is slightly visible. Other display problems, such as leakage of content and weakening of brightness when lit, were unsatisfactory.

In addition, the method described above requires an etching process, making it extremely difficult to align the patterns of the transparent electrode and the counter electrode, and requiring a special design to prevent the electrode leader lines from emitting light. I had the above difficulty.

(Object of the Invention) The present invention provides an electroluminescent display element that improves conventional displays and has a structure that facilitates mass production of a wide variety of types.

(Structure of the Invention) The present invention provides an EL display element in which a dielectric layer and a phosphor layer are arranged in a laminated manner between a pair of electrodes facing each other. a membrane at the interface between the electrode and the dielectric layer;
The EL display element is characterized in that the EL display element is interposed at either an interface between the electrode and the phosphor layer or an interface between the dielectric layer and the phosphor layer.

(Embodiment of the invention) FIG. 2 is a sectional view showing a first embodiment of the invention. Note that in the drawings, substantially the same parts as in FIG. 1 are designated by the same reference numerals.

A thin ITO transparent electrode 2 is formed on the surface of a polyester transparent insulating film 1 by sputtering, and polycarbonate (dielectric constant
A paste prepared by dissolving 3.0) in ethyl acetate at 30% by weight is applied to a desired shape by screen printing and dried to form a transparent insulating film 7. Next, a slurry prepared by mixing cyanoethylated cellulose dissolved in polyethylene glycol with a fluorescent powder containing zinc sulfide as a main component is applied and dried by a screen printing method to form a fluorescent layer 3. moreover,
After forming the dielectric layer 4 having a high dielectric constant, a counter electrode 5 made of aluminum is bonded by thermocompression bonding to complete the electroluminescent substrate. At least the phosphor layer 3 and dielectric layer 4 of the light emitting section are formed to have a uniform thickness so that uniform and efficient light emission can be achieved.

When an AC voltage of 50 Hz and 100 V was applied to the electrodes 1 and 5, only the phosphor layer 3 without the transparent insulating film 7 emitted light, resulting in a clear display with high contrast. That is, when a voltage is applied to the electrodes 1 and 5, the voltage is applied as a partial pressure to the transparent insulating film 7, the phosphor layer 3, and the dielectric layer 4, respectively, but the transparent insulating film 7 is interposed. Since the partial pressure applied to the phosphor layer 3 in the portion where the transparent insulating film 7 is interposed is smaller than the voltage required to cause the phosphor to emit light, the phosphor layer 3
In this case, only the portion where the transparent insulating film 7 is not interposed will emit light.

Furthermore, similar effects can be obtained by using an insulator with a low dielectric constant such as acrylic resin or styrene resin in addition to the above-mentioned materials as the material of the transparent insulating film 7.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

An electroluminescent substrate is completed in the same manner as in the first embodiment except that a transparent insulating film 7 having a desired shape is interposed between the phosphor layer 3 and the dielectric layer 4. When an AC voltage of 50 Hz and 100 V was applied between both electrodes of the electroluminescent substrate,
As in the first example, a clear display with high contrast was exhibited.

FIG. 4 is a sectional view showing a third embodiment of the present invention.

An electroluminescent substrate is completed in the same manner as in the first embodiment except that a transparent insulating film 7 having a desired shape is interposed between the dielectric layer 4 and the counter electrode 5. When an AC voltage of 50 Hz and 100 V was applied between both electrodes of the electroluminescent substrate,
As in the first example, a clear display with high contrast was exhibited.

Note that the present invention can be applied to all types of EL display elements such as flexible dispersion type, hollow type, and thin film type.

(Effects of the Invention) The present invention provides an EL display element in which a dielectric layer and a phosphor layer are arranged in a laminated manner between a pair of electrodes facing each other. By adopting a configuration in which the electrode is interposed at the boundary between the electrode and the dielectric layer, the boundary between the electrode and the phosphor layer, or the boundary between the dielectric layer and the phosphor layer, both When a voltage is applied between the electrodes, the voltage applied to the phosphor layer in the portion where the transparent insulating film with the desired shape and low dielectric constant is interposed becomes lower and the phosphor layer does not emit light, so that the transparent insulating film A desired light emission pattern can be obtained by interposing.

Since the phosphor layer is formed over the entire display surface and the insulating film with a desired shape and low dielectric constant is transparent, the display surface when not lit is free regardless of the position of the transparent insulating film. Since the entire surface exhibits the same color as the phosphor layer, the display pattern is difficult to see.

Since the display element has a simple laminated structure, it is easy to manufacture.

This effect is achieved.

[Brief explanation of drawings]

1 is a cross-sectional view of a conventional electroluminescent display element, FIG. 2 is a cross-sectional view showing a first embodiment of the present invention, FIG. 3 is a cross-sectional view showing a second embodiment of the present invention, and FIG. The figure is a sectional view showing a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Transparent insulating film, 2... Transparent electrode, 3... Fluorescent layer, 4... Dielectric layer, 5... Counter electrode, 6... Protective film, 7... Transparent insulating film.

Claims (1)

[Claims] 1. In an electroluminescent display element in which a dielectric layer and a phosphor layer are arranged in a laminated manner between a pair of electrodes facing each other, a transparent insulating film having a desired shape and a low dielectric constant is placed between the electrodes and the dielectric layer. an electroluminescent material interposed at any one of the interface between the electrode and the phosphor layer, the interface between the electrode and the phosphor layer, or the interface between the dielectric layer and the phosphor layer. Sense display element.