JPS6333277B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to electroluminescence (hereinafter referred to as EL).
(abbreviated as )) relates to improvements in display devices.

In recent years, thin-film EL display devices constructed with a so-called double insulating three-layer structure in which an EL layer is sandwiched between dielectric layers in a sandwich pattern have been put into practical use. Developments have been made of ferroelectric materials such as lead titanate (PbTiO ₃ ).

In one step, such a thin-film EL display device is made by disposing a transparent electrode in a predetermined pattern on a transparent glass substrate, and then sputtering the transparent electrode onto the transparent electrode.
A dielectric layer such as PbTiO ₃ and manganese as a luminescent center agent are added to a luminescent base material such as zinc sulfide (ZnS:
EL layer consisting of EL material such as Mn) and
Dielectric layers such as PbTiO ₃ are sequentially laminated, and a back electrode in a predetermined pattern is provided on the dielectric layers.

By the way, in the EL display device, there is a sharp boundary between the EL layer and the dielectric layer, so the adhesion between the EL layer and the dielectric layer becomes weak, and the EL layer and the dielectric layer become weak. There has been a problem in that spatter damage during the formation of the body layer tends to cause these films to peel off, resulting in a decrease in the display quality of the device and the manufacturing yield.

The present invention has been made in view of the above-mentioned points, and its purpose is to strengthen the adhesion between the EL layer and the dielectric layer to prevent separation of these films.
The purpose of the present invention is to provide a display device, which is characterized by having an EL layer and a dielectric layer between opposing electrodes.
In the EL display device, a buffer layer is interposed between the EL layer and the dielectric layer, and the buffer layer is made of a mixture of the material of the luminescent base material constituting the EL layer and the material of the dielectric layer.

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

The figure is a cross-sectional view of a main part for explaining the structure of an EL display device according to the present invention. Reference numeral 1 indicates a transparent glass substrate, and on the glass substrate 1 there is formed a material made of, for example, indium oxide (In ₂ O ₃ ). A transparent electrode 2 is provided, and a dielectric layer 3 made of PbTiO ₃ is deposited on the transparent electrode 2 by sputtering. Then, a buffer layer 4 is provided on the dielectric layer 3.
An EL layer 5 made of NnS:Mn is formed, and
A dielectric layer 7 made of PbTiO ₃ is deposited on the EL layer 5 via a buffer layer 6 . A back electrode 8 made of aluminum (Al), for example, is provided on the dielectric layer 7.

The buffer layers 4 and 6 are made of a mixed material in which the luminescent base material ZnS constituting the EL layer 5 and PbTiO ₃ constituting the dielectric layers 3 and 7 are mixed at a mixing ratio (weight ratio) of, for example, 1:1. There is. Such buffer layers 4 and 6 are
The film was formed by sputtering using a target formed by mixing ZnS, PbO, and TiO ₂ at a predetermined ratio.

As described above, in the EL display device according to the present invention, the buffer layer 4 is provided between the EL layer 5 and each of the dielectric layers 3 and 7.
and 6, it is possible to eliminate the sharp boundary between the EL layer and the dielectric layer that exists in conventional EL display devices, and the close contact between the EL layer and the dielectric layer can be eliminated. This helps strengthen the force, and as a result, it becomes possible to prevent the peeling of thin films that occur when EL layers and dielectric layers are formed by sputtering.

In the above-mentioned embodiment, the case was described in which the mixing ratio of ZnS and PbTiO ₃ in the thickness direction of the buffer layers 4 and 6 was constant; however, the mixing ratio of ZnS and PbTiO ₃ in the thickness direction of the buffer layer is not limited to this. It is also possible to sequentially change the ratio. In other words, the mixing ratio of PbTiO ₃ to ZnS can be made small on the side closer to the EL layer, and gradually increased as it approaches the dielectric layer side. Also, the buffer layers 4 and 6
Of course, it is also possible to use a mixture of EL layer material ZnS:Mn and dielectric layer material PbTiO ₃ . Furthermore, similar effects can be obtained even when the present invention is suitable for an EL display device having a dielectric layer on either side of the EL layer.

In addition to ZnS, the materials that serve as the luminescent base material for the EL layer include zinc selenide (ZnSe) and cadmium sulfide (CdS).
The dielectric layer material may be other materials such as
Not only PbTiO ₃ but also barium titanate (BaTiO ₃ ),
PZT (PbZr _1-x Ti _x O ₃ ), PLZT (Pb _1-3/2x La _x Zr _1-y
It is also possible to use Ti _y O ₃ ) or the like.

As is clear from the above description, the present invention can be summarized by interposing a buffer layer between the EL layer and the dielectric layer, which is made of a mixture of at least the light-emitting base material and the dielectric layer material constituting the EL layer. , it is possible to strengthen the adhesion between the EL layer and the dielectric layer and prevent the thin films from peeling off, which is extremely effective in improving the display quality and manufacturing yield of the device.

[Brief explanation of drawings]

The figure is a cross-sectional view of a main part model for explaining the structure of an embodiment of the EL display device according to the present invention. 1: Transparent glass substrate, 2: Transparent electrode, 3, 7:
Dielectric layer, 4, 6: buffer layer, 5: EL layer, 8: back electrode.

Claims (1)

[Claims] 1. In an EL display device comprising an EL layer and a dielectric layer between opposing electrodes, between the EL layer 5 and the dielectric layers 3 and 7,
An EL display device characterized in that buffer layers 4 and 6 made of a mixture of a light emitting base material and a dielectric layer constituting the EL layer are interposed.