JPS61211996A - Thin film el element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention provides electroluminescence (EL) by applying an alternating electric field.
(luminescence) relates to a thin film EL device that produces light emission.

[Prior art]

As a conventional thin film EL element, there is one described, for example, in Patent No. 19128 of 1982.

FIG. 2 is a sectional view of the above thin film EL element.

In FIG. 2, In and O are placed on the glass substrate 1.

Transparent conductive film 2 such as , SnO, etc., Y, O, or Si3N4
A first dielectric film 3 such as the above, a light emitting film 4 made of ZnS containing a small amount of Mn, and a second dielectric film 5 made of the same material as the first dielectric film 3 are sequentially laminated by electron beam evaporation or sputtering. A transparent multilayer film 100 is formed by these 2 to 5.

Note that the film thickness of each of the above parts is approximately 500 mm for the dielectric film and approximately 6000 mm for the light emitting film.

Furthermore, the mass film thickness is 50 to 300 on the second dielectric film 5.
An island-like absorber film 6 made of a Mo film is formed by electron beam evaporation or sputtering.

Note that this island-like absorber film 6 can be replaced with another metal film or semiconductor film having an island-like structure, such as Ta, Cr, SL, or the like.

Further, on the island-like absorber film 6, a transparent dielectric film 7 of M20°3 or the like having a film thickness of about 500 mm is formed.

A metal film 8 such as Al is sequentially laminated thereon by vapor deposition or sputtering. These 6 to 8 are blackened back electrodes 2
00 is formed.

The transparent conductive film 2 and the blackened back electrode 200 are patterned into appropriate shapes by ordinary photolithography.

In the above device, the transparent conductive film 2 and the blackened back electrode 2
00, the electric field inside the light emitting film 4 becomes 1
When reaching ~2 X 10' V/co+, the above 2
The portion sandwiched between the two electrodes emits light to display the patterned shape.

Therefore, it is desirable to use a material with a high dielectric constant as the first and second dielectric films.

In the device shown in FIG. 2, since the blackened back electrode 200 is used as described above, the external light that has entered through the transparent multilayer film 100 is absorbed by the island-like absorber film 6 and the transparent dielectric film 7. Therefore, the contrast in a bright environment is significantly improved compared to an element using a high reflectance metal such as M for the back electrode.

Furthermore, as an element that maintains high display contrast under high illuminance environments, an element having the structure shown in FIG.
No. 8).

In the device shown in FIG. 3, ITO (In,
O, with several percent of 5no2 added) or In, O,
A transparent conductive film 300 made of
It has a human shape and a black background plate 10 is provided behind it, and portions 1 to 5 constituting the transparent multilayer film 100 are the same as those in FIG. 2 above.

In the device shown in FIG. 3, each constituent film is composed of a single transparent film, so that external light incident from the rear of the glass substrate 1 passes through each transparent layer and is absorbed by the black background plate 10. High contrast can be obtained almost regardless of the intensity of light.

[Problem that the invention seeks to solve]

However, the devices shown in FIGS. 2 and 3 have the following problems.

First, in the device shown in FIG. 2, since the transparent dielectric film 7 (Anzoi) is provided between the island-like absorber film 6 and the metal film 8, the driving voltage increases by about 5%, and as a result, the driving voltage increases by about 5%. Since it is necessary to increase the breakdown voltage of the drive circuit, there is a problem in that the manufacturing cost of the drive circuit increases.

Furthermore, since the transparent dielectric film 7 is itself very thin and is formed on the island-shaped absorber film 6 with large irregularities, its dielectric properties are extremely unstable and dielectric breakdown easily occurs. Therefore, there is a problem that the yield during manufacturing is poor.

On the other hand, in the device shown in FIG. 3, no metal film is provided on the transparent conductive film 300, and the transparent conductive film 300 itself serves as an electrode, so it is difficult to achieve the low resistance required as an electrode. It is necessary to make the film considerably thicker, and it is also necessary to have sufficient transparency.

In order to form such a transparent conductive film, it is necessary to maintain the substrate on which transparent multilayer films 1 to 5 100 are formed at a temperature of 200°C or higher, preferably around 300°C during manufacturing. There is a problem in that cracks and film peeling occur due to the difference in thermal expansion coefficients of 1 to 5, resulting in a decrease in yield.

Furthermore, when etching to form a pattern on thick ITO or the like, it is necessary to use an acid such as HCl1, but the light-emitting film 4 is very sensitive to acid, and the acid cannot penetrate through defects such as pinholes in the second dielectric film 5. If the particles enter, the light-emitting film 4 will be dissolved, which will also cause a decrease in yield.

The present invention aims to solve the problems of the prior art as described above.

[Means for solving the problem] In order to achieve the above object, in the present invention, the blackened back electrode is formed of a multilayer thin film consisting of an island-like absorber film, a transparent conductive film, and a metal film, so that driving The structure is such that it prevents a rise in voltage, is easy to manufacture, and can improve yield.

[Embodiments of the invention]

FIG. 1 is a sectional view of one embodiment of the present invention, and the same reference numerals as in FIG. 2 indicate the same parts.

In the embodiment shown in FIG. 1, the blackened back electrode 400 includes the island-like absorber film 6, the transparent conductive film 11, and the metal ll! It has a laminated structure with lI8.

When manufacturing the device shown in FIG. 1, for example, the second dielectric film 5
An island-shaped absorber film 6 made of a Mo film having a mass film thickness of 50 to 300 nm is formed thereon by electron beam evaporation or sputtering, and a transparent conductive film 11 such as ITO is formed thereon with a mass film thickness of 100 nm.
A metal film 8 such as M is formed thereon by vapor deposition or sputtering.

Note that the island-like absorber film 6 can be replaced with another metal film or semiconductor film, such as Ta or Cr.

Moreover, as the transparent conductive film 11, in addition to ITO, In2O,
It is possible to use a semiconductor such as SNO, SL, or SL doped with an impurity to make it conductive.

Next, the effect will be explained.

External light entering from the outside through the transparent multilayer film 100 is absorbed by the island-shaped absorber film 6 and the transparent conductive film 11.

Therefore, a black back electrode that hardly reflects external light can be realized, and an EL panel with excellent display contrast can be provided.

The above operation is similar to that of the conventional element shown in FIG.

However, in the conventional element shown in FIG. 2, since the transparent dielectric film 7 is provided between the island-like absorber film 6 and the metal film 8, the driving voltage increases and dielectric breakdown is likely to occur. Although there was a problem, in the case of this embodiment, the transparent conductive film 11 is provided between the island-like absorber film 6 and the metal film 8, so that the island-like absorber film 6 and the metal film 8 are different from each other. They are virtually at the same potential, so there is no risk of the above-mentioned problems of increased drive voltage and dielectric breakdown.

Furthermore, when the transparent conductive film 300 is used alone as an electrode as in the conventional example shown in FIG. However, in the case of this embodiment, there was a problem that etching for pattern formation had to be done using acid.
Since it is used together with the metal film 8, the thickness of the transparent conductive film 11 can be made much thinner than the thickness of the transparent conductive film 300 shown in FIG.

Therefore, there is no problem even if the transparency of the film itself decreases to some extent, so the film can be formed at a low temperature.
Regarding pattern formation, since the film thickness is very thin, it can be removed together with the underlying Mo layer using an alkaline etching solution.

Therefore, unlike the conventional element shown in FIG. 3, there is no risk of problems caused by maintaining the temperature at a high temperature or by using acid during manufacturing.

In the embodiment shown in FIG. 1, one layer each of the island-like absorber film 6 and the transparent conductive film 11 are provided, but by stacking them in multiple layers, the light absorption effect can be further enhanced. It can also be increased.

〔Effect of the invention〕

As explained above, in the present invention, the back electrode is formed of a multilayer thin film consisting of an island-like absorber film, a transparent conductive film, and a metal film, which impairs the ability to obtain excellent display contrast. It is possible to prevent the drive voltage from increasing without any problems, reducing the cost of the thin film EL display system including the drive system, and eliminating the need to hold it at high temperatures or use acid during manufacturing. This makes it possible to further improve yield and reliability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, and FIGS. 2 and 3 are sectional views of an example of a conventional element. Explanation of symbols 1...Glass substrate 2...Transparent conductive film 3...
-First dielectric film 4...Light emitting film 5...Second dielectric film 6...Island absorber film 7...Transparent dielectric film 8...Metal film 11...Transparent conductive film Membrane 1
00...Transparent multilayer film 400...Blackened back electrode

Claims (1)

[Claims] In a thin film EL element in which a transparent light emitting layer is formed between a front electrode made of a transparent conductive film disposed on the display side and a back electrode disposed on the back side, the back electrode is connected to the light emitting layer. A thin film EL device characterized in that it is formed of a multilayer thin film in which at least one laminated film of a light absorber film and a transparent conductive film having an island-like structure is formed in order from the one closest to , and a metal film is provided on the outside of the laminated film.