JPH0325894A - Electroluminescent display element - Google Patents

Abstract

PURPOSE:To increase an angle part capable of improving the density of electric force line in an EL layer at the time of application of a voltage to the EL layer, improve the brightness of a picture element, and reduce uneven emission by dividing at least one of opposite electrodes of an EL display element into small areas. CONSTITUTION:In a luminous area partitioned by the width of a pair of electrodes 2, 6, a plurality of rectangular slits, or narrow holes 10 extending in the longitudinal direction of the electrode of a back plate 6 are formed. These narrow holes 10 are arranged in parallel to each other and at equal intervals. The width of the narrow hole is preferably 5-10 t to the total film thickness t of an EL layer 4 and insulating films 3, 5. Namely, by providing a plurality of through hole parts having angle parts on the electrode surfaces of the opposite electrodes in the luminous area in the EL layer, the density of the electric force line from the peripheral part of the electrode and the angle part of its surface inner part is increased, and the part having a strong field is increased in the EL layer to increase the emission quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an electroluminescent display element that emits light in response to an electrical signal.

BACKGROUND ART Braun tubes are widely used as color display devices that display multiple colors in response to electrical signals. Liquid crystal display elements have also been developed to make devices thinner. Furthermore, display elements using electroluminescence (hereinafter referred to as EL), which are completely solid-state and can emit high-intensity light, have also been developed.

Such EL display elements are classified by structure into DC type, which does not have an insulating layer or dielectric layer between the electrode and the EL layer, and AC type, which has an insulating layer between the electrode and the EL layer. The AC type is suitable as a dot matrix EL display element.

Furthermore, when classifying EL display elements by the EL layer that emits light, E
There are two types: a dispersed type in which fine particles of the L layer material are bonded with a binder and formed by coating, and a thin film type in which the EL layer material is formed by a thin film forming method such as vapor deposition or sputtering.

FIG. 4 shows a schematic cross section of a double insulation type AC EL display element formed as an X, Y matrix. The EL display element is
On a glass transparent substrate 1, a plurality of transparent electrodes 2 such as ITO,
The first insulating JII 3, the EL layer 4, the second insulating film 5, and a plurality of back electrodes 6 crossing the transparent electrode 2 are laminated and formed in this order. The EL layer 4 is made of ZnS, ZnSe, CaS,
This is a layer containing a few percent of a luminescent center substance using a semiconductor material of a metal compound of the ■-■ group such as SrS as a host substance.

In the light emitting mechanism of such an EL display element, a voltage is applied between the back electrode 6 and the transparent electrode 2, and an electric field is applied to the EL layer 4 via the first and second insulating films 5.

The applied electric field generates free electrons in the host material of the EL layer 4, and the free electrons in the electric field are accelerated to become hot electrons in a high energy state.

These hot electrons excite the luminescent center substance of the EL layer 4, and the excited state is relaxed to emit light having a predetermined spectral distribution. The color of the emitted light is determined by the combination of the host material of the EL layer 4 and the luminescent center material.

For example, when using ZnS as a host material, when the luminescence center substance is Sm, it emits red light, and similarly, when the luminescence center substance is Sm, it emits yellow light, and when it is Mn, it emits yellow light and T
At b, green light is emitted, and at Tm, blue light is emitted.

FIG. 5 shows a plane view of the EL display element according to FIG. 5 from a glass transparent substrate. X. In an EL display element having Y matrix electrodes, the light-emitting area A (shaded area) defined between the electrode surfaces of the electrodes 2.6 that intersect and face each other does not simultaneously emit light even when the applied voltage increases, and the electrodes do not emit light at the same time. Light emitting area A on the surface
As shown in FIG. 5 (C), the light emission starts sequentially from the peripheral area of This causes uneven light emission, which deteriorates the display quality of the display element.Therefore, if the area of the opposing electrode surfaces is increased, a problem arises in that the uneven light emission becomes noticeable.

SUMMARY OF THE INVENTION An object of the present invention is to provide an EL display element that does not cause a difference in intensity of light emission in the light emitting region of the EL layer.

The EL display element of the present invention has at least one pair of electrodes having portions facing each other and an EL layer disposed between the electrodes, wherein at least one of the electrodes has at least a portion facing the other. It is characterized by having one through hole.

Example Embodiments of the present invention will be described below with reference to the drawings.

The EL display element of the example also has IT on the glass transparent substrate 1.
A plurality of transparent electrodes 2 such as O, a first insulating film 3. The EL layer 4, the second insulating layer 5, and a plurality of back electrodes 6 intersecting the transparent electrode 2 are laminated and formed in order, and are laminated in the same order as the conventional EL display element and made of materials. (
Figure 4, Figure 2).

FIG. 1 shows a plan view of the EL display element of the example as viewed from the back electrode 6 side. As shown in the figure, a pair of electrodes 2.
In the light emitting region defined by the width of 6, a plurality of elongated slits or elongated holes 10 extending in the length direction of the back electrode 6 are formed. These elongated holes 10 are arranged parallel to each other and at equal intervals.

As a result of experiments, the width of the elongated hole itself is 5 to 10 μm,
The electrode part between the slotted holes is 0. A range of 1 to 0.2 is preferable because it appears to the naked eye to emit light evenly and with high brightness. The width of this long hole is determined by the total thickness of the EL layer 4 and the insulating films 3 and 5, that is, the distance between the opposing electrodes. It was also confirmed that when the thickness was 5 to 1.5 μm, and when the thickness was 5 to 10 μm, light was emitted well and evenly. In this way, as shown in the cross-sectional view of FIG.
It has been found that it is preferable to set the value to t.

Further, the elongated holes 10 are preferably formed so as to be arranged at regular intervals parallel to the length direction of the electrode to be formed, as shown in FIG. This is to prevent the resistance of the electrode from decreasing as much as possible. Forming an elongated hole perpendicular to the length direction of the electrode reduces the current path width and increases the resistance.
Furthermore, even if the elongated hole is formed at an angle with respect to the length direction of the electrode, the current path becomes longer and the resistance component increases. It should be noted that it is desirable to provide such a parallel slot 10 on a low-resistance back electrode made of metal in general, but if the response speed allows (if the resistance value is large, CR
(The time from voltage application to the start of light emission, which is determined by the time constant of , is extended), a slit may be provided on the transparent electrode side. Also,
Parallel slits may be provided in each of the opposing electrodes 2.6.

As described above, in the above embodiment, even if the through holes are formed as a plurality of parallel elongated holes extending through the electrodes, as shown in the cross-sectional view of FIG. Ba,
Since this is equivalent to the presence of a protrusion with a small radius of curvature on the electrode surface, the surface density of charges near the corner 11 increases, and the lines of electric force (broken line) in the EL layer near the corner 11 increase. The density increases.

That is, according to the present invention, by providing a plurality of through holes having corners in the electrode surfaces of opposing electrodes in the light emitting region of the EL layer, electricity from the periphery of the electrodes and the corners inside the surfaces thereof is prevented. By increasing the density of the lines of force, as shown in FIG. 2, the areas in the EL layer where the electric field is strong are increased, thereby increasing the amount of light emitted.

Furthermore, in the above embodiment, a plurality of parallel elongated holes are formed on the back electrode 6, but in consideration of the electrical resistance of the electric circuit and wiring, as shown in FIG. There are long, narrow parallel grooves 10a over the entire length of the electrode.
(Fig. 3(a)) or as slits 10b extending alternately at right angles to the electrode length direction (Fig. 3(b)). Even if the slits 10c are formed as aligned and elongated slits (
(Fig. 3(c)), or through holes 10d arranged or arranged in a dotted pattern on the electrode (Fig. 3(d)).
, arcuate slits 10e (Fig. 3(e)) arranged concentrically on the island-shaped electrode 6 instead of electrodes on the stripe, or radial slits 10f arranged along the radial direction (Fig. 3(e)).
f)).

Effects of the Invention As described above, according to the present invention, a plurality of through holes having corners are formed in the surface of at least one of the electrodes in the light emitting region of the EL layer, that is, at least one of the opposing electrodes of the EL display element is formed in a small area. By dividing the EL layer into two, it is possible to increase the corner portions that can improve the density of electric lines of force in the EL layer when voltage is applied to the EL layer, improve the brightness of the pixel, and reduce uneven light emission.

[Brief explanation of drawings]

FIG. 1 is an enlarged partial plan view of an EL display element according to the present invention;
FIG. 2 is an enlarged partial cross-sectional view of an EL display element according to the present invention;
FIG. 3 is a partial plan view showing through holes or slits in the electrode surface of the EL display element according to the present invention, and FIG.
FIG. 5 is an enlarged partial sectional view of an L display element, and FIG. 5 is an enlarged partial plan view of a conventional EL display element. Explanation of symbols of main parts 1...Substrate 2...Transparent electrode 3
．． 5... Insulation +1! I 4...EL
Layer 6... Back electrode 10... Elongated slit 11... Corner part Fig. 1 Fig. 2 Fig. 3

Claims (2)

[Claims] (1) An electroluminescent display element comprising at least a pair of electrodes having portions facing each other and an electroluminescent layer disposed between the electrodes, wherein at least one of the electrodes has at least one layer in the portion facing the other. An electroluminescent display element characterized by having two through holes. (2) The electroluminescent display element according to claim 1, wherein the through hole is an elongated slit extending in the length direction of the electrode on the surface of the electrode.