JPS61220293A - 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 Application No. 19128 of 1982.

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

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

A transparent conductive film 2 made of or SnO, etc., a first dielectric film 3 made of Y2O3, Si, N, etc., a light-emitting film 4 made of ZnS containing a trace amount of Mn, and made of the same material as the first dielectric film 3. The second dielectric films 5 are sequentially laminated by electron beam evaporation or sputtering, and these 2 to 5 form a transparent multilayer film 100.

Note that the film thickness of each of the above parts is approximately 5,000 for the dielectric film and approximately 6,000 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 also be replaced with another metal film or semiconductor film having an island-like structure, such as Ta, Cr, Si, or the like.

Furthermore, a transparent dielectric film 7 such as AflzO having a film thickness of about 500 μm is formed on the island-like absorber film 6, and a metal film 8 such as M is deposited thereon by vapor deposition or sputtering. Stack them one after another.

These 6 to 8 form the blackened back electrode 200.

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 the voltage reaches ~2×10'V/Cm, the portion sandwiched between the two electrodes emits light, and the patterned shape is displayed by light emission.

In this case, the voltage applied to the thin film EL element typically reaches a peak value of 150 to 250 V.

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. As a result, the contrast in a bright environment is significantly improved compared to an element using a high-reflectance metal such as a metal as the back electrode.

Next, FIG. 3 is a sectional view of another conventional example.

In the conventional example shown in FIG. 3, the back electrode is composed only of a metal film 9 made of M or the like.

Moreover, FIG. 4 is a sectional view of still another conventional example.

In the conventional example shown in FIG. 4, the back electrode is composed only of a transparent conductive film 10 made of ITO (tin-doped indium oxide) or the like.

[Problem that the invention seeks to solve]

In conventional thin-film EL devices such as those mentioned above, the back electrode has a metallic luster such as M or is black, so there is little room for choice in the relationship between the chromaticity and brightness between the colored light and the color of the electrode. There was a problem in that the degree of freedom was severely restricted.

In addition, in the case of using a transparent conductive film as the back electrode, the degree of freedom in shaping increases, but in the case of a case where a metal film is not provided on the transparent conductive film 10 and the transparent conductive film 10 itself becomes an electrode. Therefore, in order to achieve the low resistance required for an electrode, it is necessary to make the film considerably thicker, and it also needs to have sufficient transparency.

In order to form such a transparent conductive film, it is necessary to maintain the substrate on which the 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.

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

[Means to solve the problem]

In order to achieve the above object, in the present invention, the back electrode is formed of a multilayer thin film in which an absorbing film, a transparent film, and a metal film are laminated in order from the display side, and the thickness of the absorbing film and the transparent film is set to a predetermined thickness. By setting the value, the back electrode is configured to have a predetermined color.

[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 FIG. 1, the thin absorption film 11 is a very thin Mo film with a mass thickness of 10 to 50 people. Moreover, the transparent film 12
is an A112O film having a thickness of 50 to 3,500 people, and the metal film 8 is a metal film on the shipboard or the like having a thickness of 500 to 10,000 people.

As the absorption film 11, it is better to use a material with a relatively low reflectance, such as a metal such as Cr or Ta, or a semiconductor such as Si or Ge, in addition to Mo.

Further, as the transparent film 12, in addition to M and O, a transparent dielectric film or a transparent conductor film having a refractive index close to or larger than the refractive index of the second dielectric film 5 can be used. .

Next, one effect will be explained.

FIG. 5 is a schematic enlarged view of the back electrode of the multilayer structure of the present invention.

Although the mechanism of coloring according to the present invention has not been completely elucidated, it is presumed to be due to the following effects.

That is, external light incident from the glass substrate 1 side is absorbed to some extent by the very thin absorption film 11 and enters the transparent film 12.

This light undergoes multiple reflections between the metal film 8 and the thin absorption film 11.

The light that has been multiple-reflected and passed through the absorption film 11 toward the glass substrate 1 side has an optical path difference, and therefore interferes with each other, producing a color that corresponds to the thickness of the absorption film 11 and the transparent film 12.

Therefore, by changing the thicknesses of the absorbing film 11 and the transparent film 12, the back electrode can be colored in any color from red to blue.

In FIG. 6, the thickness of the absorption film 11 made of Mo is 10 to 50.
Human, AiL29. The thickness of the transparent film 12 made of
The colors obtained when a range of 500 people are combined are shown on a chromaticity diagram, and the shaded area shows the range of colors obtained.

Further, FIG. 7 shows an absorption film 11 made of Mo, AJl, and O.

FIG. 2 is a diagram showing the relationship between the thickness of a transparent film 12 and the color of an electrode.

In addition, in Fig. 7, the Mo film thickness is varied over a fairly wide range, but in order to increase the saturation, it is necessary to reduce the Mo film thickness, and preferably it is thinner than 50. good.

For example, if the MO film thickness is 40 people, AI! 20. The film thickness is 1
, if there are 300 people, it will be blue, and if Mo is 40 people, it will be A.
If a, O, has 1,900 people, the color becomes green, and if Mo has 40 people and M,03 has 2,800 people, the color becomes red.

It goes without saying that by adding a background that matches the color of the electrode to the portion where there is no back electrode, the entire background is unified to the same color and the display effect is increased.

〔Effect of the invention〕

As explained above, in the present invention, the back electrode is formed of a multilayer thin film in which an absorbing film, a transparent film, and a metal film are laminated, and the thickness of the absorbing film and the transparent film is set to a predetermined value. Since the back electrode is configured to have a predetermined color, the display effect can be enhanced by setting the color of the back electrode according to usage conditions.

For example, when used in an environment with strong external light, the retrospective power of one display can be enhanced by coloring the back electrode in a dark color close to the complementary color of the emitted light color when the EL element is turned on.

Also, when used in environments with relatively low illuminance, such as indoors under artificial lighting.

By coloring the back electrode in a similar color to the emission color of the EL element, visual fatigue can be reduced.

As described above, in the present invention, the display effect can be enhanced by setting the color of the back electrode according to the conditions of use. Therefore, the degree of freedom in shaping can be greatly increased, and the marketability of the EL panel can be improved.

Furthermore, in the case of the present invention, there is no risk of reducing yield or reliability during manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the present invention, FIGS. 2 to 4 are sectional views of an example of a conventional element, FIG. 5 is an enlarged view of a back electrode in the present invention, and FIG. The range of colors obtained in this example is shown on a chromaticity diagram, and FIG. 7 is a diagram showing changes in color depending on the thickness of the absorbing film 11 and the transparent film 12. Explanation of symbols

Claims (1)

[Claims] In a thin film EL element in which a transparent light-emitting film is formed between a transparent front electrode disposed on the display side and a back electrode disposed on the back side, the back electrode is formed with an absorbing film in order from the display side. The back electrode is formed of a multilayer thin film in which a transparent film and a metal film are laminated, and the thickness of the absorption film and the transparent film is set to a predetermined value, so that the back electrode has a predetermined color. A thin film EL device characterized by: