JPS6262436B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to electroluminescence (hereinafter referred to as EL).
The present invention relates to display panels (abbreviated as ), and in particular to the substrate structure of EL display panels that are driven at low voltages.

In recent years, a so-called double insulating three-layer structure has been developed in which the EL layer is sandwiched between dielectric layers in a sandwich-like pattern.
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 layer such as lead titanate (PbTiO ₃ ), which substantially reduces the voltage applied to the EL layer. The method is to make it bigger.

The configuration of such an EL display panel is generally the first one.
As shown in the figure, an insulating substrate 1 made of a transparent glass plate
A transparent lower electrode 2 made of, for example, linear indium tin oxide (ITO) is placed on the insulating substrate 1.
An EL material such as zinc sulfide (ZnS:Mn) in which a large number of are arranged in parallel and manganese is added to the surface of the insulating substrate 1 including the surface of the lower electrode ₂ through a first dielectric layer 3 made of PbTiO 3 . Further, a linear upper electrode 6 made of, for example, aluminum (Al) is formed on the EL layer 4 via a second dielectric layer 5 made of, for example, alumina (Al ₂ O ₃ ). It is arranged in parallel with the lower electrode 2 in a relationship perpendicular to it. By selectively applying a voltage between the lower electrode 2 and the upper electrode 6, the EL layer 4 at the intersection point is
A desired shape can be observed from the insulating substrate 1 side by utilizing the fact that it emits light.

By the way, the glass plate used as the insulating substrate 1 of the EL display panel having the above-mentioned structure needs to have a predetermined heat resistance and coefficient of thermal expansion, and also need to have a smooth surface. In other words, the PbTiO ₃ film that becomes the first dielectric layer 3 is usually formed by high-frequency sputtering, but at that time the substrate temperature is kept at 600°C.
Since the film is formed while being maintained at about 0.degree. C., a heat-resistant glass plate that does not deform at that temperature is required. Also, after forming the EL layer 4, the EL layer is
Since heat treatment, or annealing, is performed at approximately 580°C, a material with a thermal expansion coefficient of approximately 40 to 90 (x10 ^-7 °C ^-1 ) is required to prevent cracks in the EL layer during this process. Glass plates with such heat resistance and thermal expansion coefficient are extremely expensive, and it is difficult to obtain large glass plates with such characteristics. This has been a major obstacle to lowering the price and increasing the size of EL display panels that aim to achieve this.

The present invention has been made in view of the above-mentioned points, and its purpose is to provide an EL display panel that uses an inexpensive insulating substrate and can be driven at low voltage. In an EL display panel comprising an EL layer between a lower electrode of a predetermined shape and an upper electrode placed oppositely on the lower electrode, the insulating substrate is composed of a multilayer insulating substrate in which a glass layer is laminated on an alumina substrate. It's about to happen.

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

FIG. 2 is a cross-sectional view of a main part showing the structure of an EL display panel according to the present invention. Reference numeral 11 denotes a multilayer insulating substrate. Linear lower electrodes 12 are arranged in parallel, and the surface of the multilayer insulating substrate 11 including the surface of the lower electrodes 12 is coated with a first layer of PbTiO ₃ .
A dielectric layer 13 made of ZnS:Mn, an EL layer 14 made of ZnS:Mn, and a second dielectric layer 15 made of Al ₂ O ₃ are successively laminated, and a linear transparent upper electrode made of ITO is further formed on the dielectric layer 15. 16 are arranged in parallel with orthogonal to the lower electrode 12. and the lower electrode 12
The point that a light emitting cell is defined at each intersection between the upper electrode 16 and the upper electrode 16 is the same as in the conventional one, but the present invention
The major differences from conventional EL display panels are as follows. That is, instead of using an expensive glass plate as an insulating substrate, a multilayer insulating substrate 11 is used. This multilayer insulating substrate 11 has a glass layer 11a laminated on an alumina base 11b, and is called a glaze-coated alumina substrate and is widely used as a substrate for hybrid integrated circuits and the like. Such glaze-coated alumina substrates are commercially available with excellent surface smoothness and heat resistance, and have a coefficient of thermal expansion of 40 to 90 (×10 ^-7 °C ^-1 ). It is easier and cheaper to obtain than.

Therefore, in the present invention, a glaze-coated alumina substrate as described above, which has extremely advantageous characteristics in manufacturing an EL display panel, is used as a multilayer insulating substrate 11.
It is used as However, since the alumina base 11b of such a multilayer insulating substrate 11 is opaque,
Light from the light emitting cells cannot be extracted from the substrate 11 side. Therefore, in order to extract the light from the light emitting cells from the upper electrode 16 side, in the EL display panel of this embodiment, the upper electrode 16 is formed of a transparent conductive film such as ITO, and the lower electrode 12 is formed with a transparent conductive film such as ITO. It is made of a metal with a melting point, such as a Mo film.

In this way, an inexpensive multilayer insulating substrate 11 is used instead of an expensive glass plate as an insulating substrate, and an EL display panel that can be driven at a low voltage can be manufactured at low cost without changing the conventional manufacturing process. This is possible.

Note that in the above embodiment, the first dielectric layer 13 is
Although the case where the EL layer 14 is formed of PbTiO ₃ has been described, it is not limited thereto, and may be formed of other dielectric layers such as Y ₂ O ₃ .
The present invention can be applied not only to EL display panels constructed with a three-layer structure of double insulating films sandwiched in a sandwich pattern, but also to DC-driven EL display panels in which the EL layer is directly sandwiched between a lower electrode and an upper electrode. You can also get the same effect.

As is clear from the above description, in short, the present invention provides an EL display panel comprising an EL layer between a lower electrode of a predetermined shape disposed on an insulating substrate and an upper electrode disposed opposite to the lower electrode. In,
The insulating substrate is composed of a multilayer insulating substrate in which a glass layer is laminated on an alumina base,
EL that can be driven at low voltage by using an inexpensive multilayer insulating substrate instead of the conventional expensive glass substrate
This has the advantage that the display panel can be realized at low cost.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part for explaining the structure of a conventional EL display panel, and FIG. 2 is a sectional view of a main part for explaining the structure of an EL display panel of the present invention. 1: Insulating substrate, 2, 12: Lower electrode, 3, 5,
13, 15: dielectric layer, 4, 14: EL layer, 6,
16: Upper electrode, 11: Multilayer insulating substrate, 11a:
Glass layer, 11b: alumina substrate.

Claims (1)

[Claims] 1. In an EL display panel comprising an EL layer between a lower electrode of a predetermined shape disposed on an insulating substrate and an upper electrode disposed opposite to the lower electrode,
An EL display panel characterized in that the insulating substrate is a multilayer insulating substrate in which a glass layer is laminated on an alumina base.