JPS5932880B2 - EL display panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroluminescent (hereinafter abbreviated as EL) display panel, and particularly to an EL display panel that is driven at a low voltage.
This invention relates to improvements to display panels.

In recent years, the EL layer is sandwiched between dielectric layers,
An EL display panel constructed with a so-called double-insulating three-layer structure has been developed and put into practical use.

One way to drive such an EL display panel at a low voltage is to form the dielectric layer with a ferroelectric material such as lead titanate (PbTio3), thereby substantially increasing the voltage applied to the EL layer. The method is being adopted. The structure of such an EL display panel generally uses a transparent glass substrate 1 as an insulating substrate, as shown in FIG. A large number of transparent electrodes 2 are arranged.
EL is applied to the surface of the glass substrate 1 including the surface via a dielectric layer 3.
A layer 4 is formed, and a linear back electrode 6 made of, for example, aluminum (Al) is disposed on the EL layer 4 via a dielectric layer 5 in a relationship perpendicular to the transparent electrode 2.

By selectively applying a voltage between the transparent electrode 2 and the back electrode 6, the EL layer 4 at the intersection point emits light to display a desired image. By the way, when the dielectric layers 3 and 5 are composed of a ferroelectric material such as PbTiO3, a high frequency sputtering method is usually used for film formation.

However, especially when the dielectric layer 3 made of PbTiO3 is formed by such a sputtering method, the dielectric layer 3 made of transparent PbTiO3 is formed on the transparent electrode 2;
PbTi03 deposited in direct contact with the surface of the glass substrate 1
The dielectric layer 3 made of the above-mentioned material tends to devitrify easily. As a result of investigating such a devitrification region of the dielectric layer 3, it was confirmed that there were irregularities on the film surface in that region, and the depth of the irregularities was as deep as the film thickness (for example, several 1000
It was found that some of them reached λ). However, on the dielectric layer 3 which has such an uneven surface, the FL layer 4,
When the dielectric layer 5 is sequentially formed and the back electrode 6 is further formed by vapor deposition on the dielectric layer 5, the unevenness of the dielectric layer 3 will affect each film formed thereon, and the final However, there was a drawback that the back electrode 6 could become disconnected, or even if the disconnection did not occur, it would cause problems such as an increase in resistance. The present invention has been made in view of the above-mentioned points, and its object is to provide an EL display panel having a structure that prevents the occurrence of unevenness on the surface of a dielectric layer made of a ferroelectric material and can be driven at a low voltage. and
The feature is that in a structure comprising an electrode in a predetermined pattern on an insulating substrate, a dielectric layer formed on the electrode, and an EL layer formed on the dielectric layer, at least the dielectric layer of the insulating substrate An insulating underlayer made of a heat-resistant oxide material is interposed on the contacting surfaces.

Embodiments of the present invention will be described below with reference to the drawings. Figure 2 is a sectional view of a main part model for explaining the structure of an embodiment of an EL display panel according to the present invention, and is equivalent to Figure 1. Parts are given the same reference numerals.

In the figure, reference numeral 1 denotes a glass substrate, on which an insulating base layer 7 made of a heat-resistant oxidizing substance is formed. A linear transparent electrode 2 made of In2O3 or the like is disposed on the base layer 7, as in the conventional EL display panel, and the surface of the base layer 7 including the surface of the transparent electrode 2 is covered with PbT.
Zinc sulfide to which manganese is added is formed through a dielectric layer 3 (for example, layer thickness 4000λ) made of a ferroelectric material such as iO3.
An EL layer 4 (for example, layer thickness 5000λ) made of an EL material such as ZnS:Mn) is formed. Further, on the EL layer 4, a dielectric layer 5 having a layer thickness of about 4000λ, for example.
A linear back electrode 6 made of Al (such as PbTiO) is disposed perpendicularly to the transparent electrode 2. As is clear from the figure, the EL display panel according to the present invention differs from the conventional one in that an insulating base layer 7 made of a heat-resistant oxidizing material is provided on the glass substrate 1 in advance. This base layer 7 is made of, for example, aluminum oxide (Al2O
3), which is formed in advance on the surface of the glass substrate 1 by a steaming method or a sputtering method to a thickness of, for example, about 5,000 layers. By forming the base layer 7 made of Al2O3 on the surface of the glass substrate 1 in this way to prevent the glass substrate 1 and the dielectric layer 3 from coming into direct contact with each other, the dielectric layer 3 made of PbTiO3 can be formed by sputtering. It has been found that during film formation, it is possible to obtain a transparent and homogeneous PbTiO3 film without any unevenness on the surface of the dielectric layer 3, which occurs when the film is conventionally formed directly on the glass substrate 1. However, the EL layer 4, dielectric layer 5, back electrode 6, etc., which are sequentially formed on the homogeneous dielectric layer 3 with no surface irregularities, can be formed uniformly without any irregularities. As a result, it is possible to eliminate problems such as disconnection of the back electrode 6 and an increase in resistance caused by unevenness of the dielectric layer 3, which conventionally occurred in a region where a film was directly formed on the glass substrate 1. Further, FIG. 3 is a cross-sectional view of a main part showing the structure of another embodiment of the EL display panel according to the present invention, and the same parts as in FIG. 2 are given the same reference numerals.

In this embodiment, a transparent electrode 2 is disposed on a glass substrate 1, and A
A base layer 7 made of l2O3 is formed. This base layer 7 is formed to a thickness of, for example, 100 to 500 layers by vapor deposition or sputtering in the same manner as in the previous embodiment, and the thickness of the base layer 7 is the same as that of the EL layer 4. Since it is made sufficiently thinner than that, the influence of increase in drive voltage is extremely small. Also in this embodiment, since the base layer 7 is formed between the glass substrate 1 and the dielectric layer 3, the dielectric layer 3 can be formed uniformly without any unevenness on its surface. Note that if the base layer 7 made of Al2O3 is formed by sputtering, the PbTiO formed on the base layer 7 will be
The dielectric layer 3 consisting of the dielectric layer 3 can be formed continuously by simply changing the target within the same sputtering apparatus, and the complication of the film forming process can also be avoided. Thus, according to the present invention, it is possible to eliminate problems such as disconnection of the back electrode 6 and increase in resistance caused by unevenness of the dielectric layer 3, which conventionally occurred in areas directly formed on the glass substrate 1. PbTi
There is an advantage that an EL display panel using a ferroelectric material such as O3 and capable of being driven at a low voltage can be easily realized.

In the above-mentioned embodiment, the case where the base layer 7 is formed of Al2O3 is described, but the base layer 7 is not limited to this, and may be formed of other heat-resistant oxide materials such as yttrium oxide (Y2O3) or magnesium oxide (MgO). Furthermore, it is of course possible to form the base layer 7 only between the glass substrate 1 and the dielectric layer 3.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part model for explaining a conventional EL display panel structure, FIG. 2 is a cross-sectional view of a main part model for explaining a first embodiment of an EL display panel according to the present invention, and FIG. The figure is a cross-sectional view of a main part showing the structure of the second embodiment of the EL display panel according to the present invention.〇1: Glass substrate, 2, 6: Electrodes, 5: Dielectric layer, 7: Made of heat-resistant oxide material An insulating base layer.

Claims (1)

[Claims] 1. In a structure comprising an electrode in a predetermined pattern on an insulating substrate, a dielectric layer formed on the electrode, and an EL layer formed on the dielectric layer, at least the surface of the insulating substrate in contact with the dielectric layer 1. An EL display panel characterized in that an insulating base layer made of a heat-resistant oxide material is interposed therein.