JPS6247357B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a display device, particularly a display device such as an electroluminescent (hereinafter abbreviated as EL) display panel, which is driven at a lower voltage.

In recent years, the EL layer has been sandwiched between dielectric layers in the form of a sandwich, a so-called double-insulating three-layer structure.
EL display panels have been developed and put into practical use. One way to drive such EL display panels at low voltages is to form the dielectric layer with a ferroelectric material such as lead titanate (PbTiO ₃ ) to substantially increase the voltage applied to the EL layer. The method is being adopted.

The configuration of such an EL display panel is generally the first one.
As shown in the figure, a transparent glass substrate 1 is used as a support substrate, a large number of thin transparent electrodes 2 are arranged in parallel on the glass substrate 1, and a dielectric layer is formed on the surface of the glass substrate 1 including the surface of the transparent electrodes 2. An EL layer 4 is formed on the EL layer 4 via a dielectric layer 5, and a strip back electrode 6 is disposed perpendicularly to the transparent electrode 2 on the EL layer 4 via a dielectric layer 5. By selectively applying a driving voltage between the transparent electrode 2 and the back electrode 6, a desired image is displayed using the EL layer 4 at the intersection point emitting light.
By the way, when the dielectric layers 3 and 5 are composed of a ferroelectric material such as PbTiO ₃ , especially in the dielectric layer 3, the upper surface of the amorphous glass substrate 1 and the transparent electrode 2 with good crystallinity [for example, oxidized Indium (In ₂ O ₃ ) film] Due to the difference in the underlying layer, the crystallinity of the PbTiO ₃ film formed thereon becomes non-uniform. That is, the PbTiO ₃ film also shows good crystallinity on the transparent electrode 2 which has good crystallinity, but the PbTiO ₃ film formed directly on the glass substrate 1 has poor crystallinity. As a result, the transparent electrode 2 in the dielectric layer 3
There was a problem in that there were places where the crystallinity suddenly changed near the edges of the dielectric layer 3, and the dielectric layer 3 peeled off at the places where the crystallinity suddenly changed. In addition, the better the crystallinity of PbTiO ₃ , the higher the dielectric constant, so the dielectric constant changes suddenly at points where the crystallinity suddenly changes in the dielectric layer 3, leading to uneven electric field distribution and uneven display brightness. There were also problems.

The present invention has been made for the purpose of eliminating the above-mentioned problems, and its features include disposing electrodes in a predetermined pattern on a support substrate, and forming a crystalline dielectric layer on the surface of the support substrate including the electrode surface. In a display device having a display medium layer interposed therebetween, a base layer made of a crystalline insulator is provided between the dielectric layer and the support substrate.

An embodiment of the present invention applied to an EL display panel will be described below with reference to the drawings.

FIG. 2 is a sectional view of a main part for explaining the structure of the EL display panel according to the present invention, and the same parts as those in FIG. 1 are designated by the same reference numerals. In the figure, reference numeral 1 denotes a transparent glass substrate, on which a base layer 7 made of a crystalline insulator is formed. And on top of that base layer 7, there is a conventional
Similar to the EL display panel, a thin transparent electrode 2 made of In ₂ O ₃ or the like is provided, and a dielectric layer 3 made of a ferroelectric material such as PbTiO ₃ is formed on the base layer 7 including the top of the transparent electrode 2. An EL layer 4 is formed of an EL material such as zinc sulfide (ZnS:Mn) with manganese added thereto. Further, on the EL layer 4, aluminum (Al) is applied via a dielectric layer 5 made of PbTiO _{3 .}
The back electrode 6 in the form of strips made of
It is arranged in a relationship that is perpendicular to . As is clear from the figure, the EL display panel according to the present invention and the conventional EL
The structural difference from the display panel is that a base layer 7 made of a transparent insulator with good crystallinity is formed on the amorphous glass substrate 1 in advance.

This base layer 7 is made of, for example, zinc sulfide (ZnS), and by depositing ZnS while maintaining the temperature of the glass substrate 1 at about 200°C, ZnS with good crystallinity is formed on the amorphous glass substrate 1. It was formed as a film. By forming the base layer 7 made of a crystalline insulator on the amorphous glass substrate 1 in this way, the dielectric layer 3 can be uniformly formed when the dielectric layer 3 is deposited by sputtering. It can be formed as a crystalline dielectric film. In other words, conventional
In an EL display panel, the transparent electrode 2 with good crystallinity and the amorphous glass substrate 1 serve as the base layer, so that the dielectric layer 3 formed thereon has non-uniform crystallinity. However, since the dielectric layer 3 of the EL display panel according to the present invention is formed on the amorphous glass substrate 1 via the base layer 7 made of a crystalline insulator as described above, it is not crystalline as in the conventional case. A uniform crystalline dielectric layer 3 can be easily formed without causing non-uniformity. In this way, problems such as peeling of the dielectric layer 3 and uneven display brightness caused by non-uniform crystallinity of the dielectric layer 3 can be removed, and it is possible to eliminate problems such as peeling of the dielectric layer ₃ and uneven display brightness. This has the advantage of making it easy to create high-performance EL display panels that can be driven at low voltages.

In addition, although the above-mentioned embodiment described an EL display panel, the present invention is not limited to this, and similar effects can be obtained even when applied to other display devices such as a gas discharge display panel that uses easily discharged gas as a display medium layer. Can be done. Furthermore, it is applicable not only to display devices but also to the formation of ferroelectric films such as optical waveguides and surface acoustic wave filters.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the main parts to explain the structure of a conventional EL display panel, and Figure 2 is an EL display panel according to the present invention.
FIG. 2 is a cross-sectional view of main parts for explaining the structure of a display panel. 1: glass substrate, 2, 6: electrode, 3, 5: dielectric layer, 4: EL layer, 7: base layer made of crystalline insulator.

Claims (1)

[Claims] 1 Arrange electrodes in a predetermined pattern on a support substrate,
In a display device comprising a display medium layer on a support substrate surface including the electrode surface via a crystalline dielectric layer, a base layer made of a crystalline insulator is provided between the dielectric layer and the support substrate. A display device characterized by: