JPH0634390B2 - EL display device - Google Patents

Description

The present invention relates to an EL display device that produces EL (electroluminescence) light emission by applying an electric field, and more particularly to a technique for suppressing reflection from a glass substrate surface.

[Prior art]

As a conventional thin film EL panel, for example, there is one as shown in FIG. 3 (for example, described in Japanese Patent Application No. 57-182595).

In FIG. 3, In ₂ O ₃ and S are formed on the glass substrate 1.
Front electrode 2 made of a transparent conductive film such as nO ₂ (film thickness of about 2000
Å) is vapor-deposited, followed by a first dielectric film 3 made of Y ₂ O ₃ , Si ₃ N _4, etc., and a light emitting film 4 made of ZnS containing a small amount of Mn.
The second dielectric film 5 made of the same material as the first dielectric film 3 is sequentially laminated by electron beam evaporation or sputtering, and the above 3 to 5 form the transparent multilayer film 100. The thickness of each dielectric film is 5000
Å, luminescent film is about 6000Å.

Next, a mass film thickness of 50 to 30 is formed on the second dielectric film 5 described above.
The island-shaped absorber film 6 made of a 0Å Mo film is formed by electron beam evaporation or sputtering. The island-shaped absorber film 6 can be replaced with another metal film or semiconductor film having an island-shaped structure, for example, Ta, Cr, Si or the like.

A film thickness of about 5000Å is formed on the island-shaped absorber film 6 described above.
A transparent dielectric film 7 such as Al ₂ O ₃ is formed, and Al is formed on the transparent dielectric film 7.
A metal film 8 of the like is sequentially laminated by vapor deposition or sputtering.

The above 6 to 8 form the blackened back electrode 200.

In addition, the front electrode 2 and the blackened rear electrode 200 described above are
Patterning into a shape corresponding to a desired display shape is performed by ordinary photolithography.

As described above, the EL display device in which the thin film EL element is formed on the glass substrate is completed.

When an AC voltage is applied between the front electrode 2 and the blackened back electrode 200 of the EL display device as described above, and the electric field in the light emitting film 4 reaches 1 to 2 × 10 ⁶ V / cm, the electrodes are applied to both electrodes. The sandwiched part emits light and a graphic is displayed.

In the above EL display device, external light that has entered the blackened back electrode 200 from the outside through the transparent multilayer film 100 is
It is absorbed by the island-shaped absorber film 6 and the transparent dielectric film 7. Therefore, the specular reflection and diffuse reflection by the blackened back electrode 200 are 1/100 or less, respectively, as compared with the case where the back electrode is formed only by a metal such as Al, and the reflection of the back electrode by the above configuration is It solves the problem of reduced visibility.

[Problems to be solved by the invention]

In the conventional EL display device as described above, since the difference between the refractive index of the glass substrate 1 and the refractive index of air is quite large, specular reflection occurs strongly on the surface of the glass substrate 1, and when used in a bright environment. Had a problem in that the display of the observer himself or the surrounding scenery was not visible, and the display was not easy to see, which caused a lot of discomfort.

In order to solve the above problems, a glass substrate 1 of an EL panel
It is also possible to directly provide an antireflection film on the front surface of. However, in that case, since the temperature of the EL panel rises when the antireflection film is formed, there arises a problem that the yield is deteriorated.

The present invention has been made in order to solve the problems of the prior art as described above, and provides an EL display device that prevents reflection on the surface of a glass substrate, makes it easy to see the display even in a bright environment, and has a good manufacturing yield. The purpose is to do.

[Means for solving problems]

To achieve the above object, in the present invention, an EL panel having a thin film EL element formed on one surface of a glass substrate, and an antireflection film on one surface of a transparent substrate having the same refractive index as the above glass substrate. And the regular reflection suppressor having the above-mentioned structure are arranged in parallel so that the thin film EL element formation surface and the antireflection film formation surface are back-to-back with each other through a transparent body having substantially the same refractive index as the glass substrate. I have set up.

[Action]

According to the present invention, which is configured as described above,
The reflection of external light is suppressed by the antireflection film, and the substrate of the regular reflection suppressor and the glass substrate of the EL panel have the same refractive index, and the transparent bodies provided between them are also substantially the same. Since it has a refractive index, there is almost no reflection from those portions, and therefore, it is possible to realize an EL display device in which reflection of external light is significantly suppressed.

Further, since the EL panel and the specular reflection suppressor are separately configured and then combined, there is no problem that the yield is deteriorated due to the temperature rise of the EL panel during manufacturing.

Example of Invention

FIG. 1 is a sectional view of a main part of an embodiment of the present invention, and the same reference numerals as those in FIG. 3 denote the same parts.

In FIG. 1, the substrate 21 is a transparent body having the same refractive index as the glass substrate, and for example, the same glass substrate as the glass substrate 1 may be used.

Further, an antireflection film 400 is formed on the surface of the substrate 21.

As the antireflection film 400, for example, the substrate 21 has a refractive index n.
= 1.52 soda glass, CeF ₃ 22 with a refractive index n ₁ = 1.70, ZrO ₂ O ₂ 23 with a refractive index n ₂ = 2.1, and MgF ₂ 24 with a refractive index n ₃ = 1.38 are in order respectively. about 920 Å, about 1200 Å, was laminated with a film thickness of about 750 Å, called _{λ 0/4-λ 0/} 2-λ 0/4 type three-layer anti-reflection film can be used.

The above three-layer antireflection film, for example, electron beam evaporation method,
Alternatively, it is formed by a resistance wire heating vapor deposition method.

As described above, the regular reflection suppressor 500 having the antireflection film 400 formed on the substrate 21 is formed.

Next, the EL panel 300 and the diametrically opposite suppressor 500 are arranged in parallel so that the vapor deposition surfaces are back to back with each other through the spacers 25 having a thickness of about 0.3 mm, a length of 3 mm, and a width of 3 mm installed at the four corners. Then, an epoxy adhesive 26 is applied along the periphery of the substrate 21.
Attach and fix.

However, in order to inject a transparent body 28, which will be described later, between the glass substrate 1 and the substrate 21, there is only one portion where an adhesive is not applied, that is, an injection hole (not shown, for example, a size of about 1 mm). Shall be provided.

Next, a transparent liquid 27 having a refractive index substantially the same as that of the glass substrate 1 and the substrate 21 is injected from the above injection hole to completely fill the space formed by the glass substrate 1 and the substrate 21. The injection hole is sealed with the same epoxy adhesive as above.

Examples of the transparent liquid 27 include silicon oil (for example, KF5 manufactured by Shin-Etsu Chemical Co., Ltd.) when the glass substrate 1 and the substrate 21 are soda glass having a refractive index of 1.52.
1, the refractive index n = 1.51) can be used.

As the injection method, the pressure difference is utilized by reducing the pressure while the injection hole is submerged in the silicone oil, completely exhausting the air between the glass substrate 1 and the substrate 21, and then returning to the atmospheric pressure again. A method of injecting silicone oil into the gap can be used.

The EL display device of FIG. 1 is completed as described above.

Next, the operation will be described.

Of the ambient light I that reaches the antireflection film 400 of the EL display device from the outside, a small part is reflected as the reflected light I ₁ .
Most of them pass through as they are, and proceed to the boundary surface between the substrate 21 and the transparent body 27.

However, since the substrate 21 and the transparent body 27 have substantially the same refractive index, in other words, they have the same optical quality, and therefore go straight without causing regular reflection at this surface.

Further, also at the boundary surface between the transparent body 27 and the glass substrate 1, the light is transmitted without reflection as in the above.

The transmitted light I ₁ ′ entering the thin film EL device as described above
Is finally absorbed by the blackened back electrode 200 and disappears.

In the case of the embodiment shown in FIG. 1, the light reflected on the observer side by the surface of the EL display device is a weak reflected light I reflected by the antireflection film.
₁ only.

On the other hand, in the conventional EL display device as shown in FIG. 3, the light I ₂ reflected on the surface of the glass substrate 1 is considerably large.

FIG. 2 is a diagram comparing the intensity of regular reflection in the visible light region between the present embodiment shown in FIG. 1 and the conventional EL display device shown in FIG. The case where the light is incident from the line direction is shown.

As can be seen from FIG. 2, the reflectance of the EL display device of the present invention is reduced to ⅕ or less of the conventional value over a wide visible light range.

That is, when the EL panel is lit with the same brightness, about 5
This means that it is possible to ensure the same legibility even in an environment with double the brightness.

Incidentally, the in the embodiment of FIG. 1, using a so-called _{λ 0/4-λ 0/} 2-λ 0/4 type three-layer anti-reflection film as an antireflection film is not limited thereto, For example,
To further reduce the reflectance of the EL display device,
A more multilayer antireflection film can be used.

For example, from the side closer to the substrate 21 having a refractive index n = 1.52, M
gF ₂ (n ₁ = 1.38), ThF ₄ (n ₂ = 1.53), ZnS (n ₃
= 2.35) and MgF ₂ (n ₄ = 1.38) 920 respectively
When a four-layer antireflection film deposited with a film thickness of Å, 1085Å, 830Å, 920Å is used, the regular reflectance of the EL display device can be reduced to 1/10 or less of the conventional value.

Further, in the case of an EL display device the ambient light is used in not very strong place, although suppression of the reflectance decreases, cheap single-layer antireflection film manufacturing cost and _{λ 0/4-λ 0/} 4 It is also possible to use a two-layer antireflection film of the type.

Further, in the above embodiment, the glass substrate 1 and the substrate 21
The case where a transparent liquid, for example, silicon oil is used as a substance to be filled between the and is illustrated. However, this substance is transparent and has a refractive index almost the same as that of the glass substrate 1 and the substrate 21. The liquid is not limited to the liquid as long as it has, and for example, a transparent adhesive or a transparent paste that finally solidifies can be used.

Further, in the embodiment of FIG. 1, the antireflection film having the antireflection film is formed on the substrate 21, and the antireflection film is formed so as to be combined with the EL panel. It is also possible to directly provide an antireflection film on the front surface of.

However, in that case, when forming the antireflection film, the EL
Since the temperature of the panel rises, there is a problem that the yield deteriorates, which is not preferable.

In that respect, when the EL panel and the specular reflection suppressor are separately configured and then combined as in the embodiment of FIG. 1, the above-mentioned problems do not occur.

〔The invention's effect〕

As described above, in the present invention, the EL panel in which the thin film EL element is formed on the glass substrate and the specular reflection suppressor in which the antireflection film is formed on the substrate having the same refractive index as the above glass substrate are described above. Since it is configured to be placed back to back through a transparent body that has almost the same refractive index as the glass substrate of, the specular reflection on the glass substrate surface is significantly reduced, and the surrounding scenery is displayed in a bright environment. It is possible to solve the problem of the conventional device that it becomes difficult to see.

In addition, since the EL panel and the specular reflection suppressor are separately configured and then combined, the yield of the EL panel is not deteriorated due to the temperature rise of the EL panel at the time of manufacturing, and high efficiency is achieved. The EL panel can be manufactured at low cost.

Further, when used in the same environment, the device can be driven at a low luminance with a smaller electric field stress as compared with the conventional device, so that the life of the device can be extended and other excellent effects can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the present invention, FIG. 2 is a comparison diagram of reflectance in a conventional device and a device of the present invention, and FIG. 3 is a cross-sectional view of an example of a conventional device. <Explanation of reference symbols> 1 ... Glass substrate, 2 ... Front electrode 3 ... First dielectric film, 4 ... Light emitting film 5 ... Second dielectric film, 6 ... Island-like absorber film 7 ... Transparent dielectric film, 8 …… Metal film 21 …… Substrate, 25 …… Spacer 26 …… Adhesive, 27 …… Transparent body ……… Transparent multilayer film, 200 …… Blackened back electrode 300 …… EL panel, 400 …… Anti-reflection film 500 …… Regular reflection suppressor

Claims (1)

[Claims] 1. An EL panel in which a thin film EL element is formed on one surface of a transparent glass substrate, and a specular reflection suppressor in which an antireflection film is formed on one surface of a transparent substrate having the same refractive index as the glass substrate. And a transparent body having substantially the same refractive index as the glass substrate, the EL panel and the specular reflection suppressing body via the transparent body, the thin film EL element formation surface and the antireflection film. An EL display device characterized in that they are arranged in parallel so as to be back-to-back with the formation surfaces of the two.