JPH0439894A - El display device - Google Patents

Abstract

PURPOSE:To reduce crosstalk between adjoining picture elements by dividing a luminous film into picture element luminous films at every picture element to be formed, and arranging a shade film between the luminous film and a back electrode film so as to cover the spaces between mutual picture element luminous films and the back side. CONSTITUTION:A luminous film is divided into picture element luminous films 4P at every picture element so as to eliminate parts between the mutual picture elements. Moreover direct crosstalk light between adjoining picture element luminous films 4P is shut off by arranging a shade film 10 between the luminous film and a back electrode film 6 to cover the spaces between mutual picture element luminous films 4P, and also indirect crosstalk light via the back side is cut off by covering the back side too of the picture element luminous films 4P. This almost completely prevents crosstalk between mutual picture elements in an EL display device.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to electroluminescence (hereinafter referred to as EL).
The present invention relates to an EL display device based on the electroluminescence principle, which includes a light emitting film and an insulating film between a transparent electrode film on a substrate side and a back electrode film, and displays pixels arranged in an array.

[Conventional technology]

EL display devices can be configured into thin display panels and have recently been attracting attention as small display devices for computers and the like because they can emit high-intensity light.

In an EL display device suitable for such uses, a large number of pixels are arranged in a two-dimensional array or matrix within the display surface, and a transparent electrode film is arranged on the front side of the panel, and a back electrode film is arranged on the back side of the panel. A variable image can be displayed by applying display data or display drive voltage between the two. Although this is well known, the outline of the conventional structure will be briefly explained with reference to FIG.

In FIG. 4, indium tin oxide (hereinafter referred to as ITO) is deposited on a transparent insulating substrate 1, which is generally a glass plate.
A few hundred strips of very thin transparent electrode films 2 are arranged, and the top is covered with an insulating film 3 such as silicon nitride.The light emitting film 4 provided on top of this is usually made of a base material of ZnS and a luminescent active material such as Mn. It contains a small amount of as a luminescent center. This light-emitting film 4 is covered with the same insulating film 5 as above, and on top of that, several hundred back electrode films 6 made of aluminum or the like are arranged in a direction perpendicular to the transparent electrode film 2 to form a transparent electrode! l! A luminescent display pixel is formed in a portion of the luminescent film 4 corresponding to each intersection between the luminescent film 2 and the back electrode film 6.

In an EL display device configured in this manner, display data is placed on, for example, the transparent electrode film 2, and the back electrode film 6 is normally scanned sequentially with an alternating current display drive voltage that switches between positive and negative at each scanning period. At this time, the voltage applied between the picture electrode films 2 and 60 causes the insulating films 3 and 5 to be displayed.
An electric field is applied to each pixel portion of the light emitting film 4 sandwiched between the two, and the EL light is emitted from the transparent substrate 1 side. As mentioned above, when the luminescent center in ZnS of the luminescent film 4 is Mn, the EL
The display device performs a yellow monochrome display with a wavelength of 5800. Note that the insulating film 3 on the front side may be omitted from the structure shown in FIG. 4.

[Problem to be solved by the invention]

The above-mentioned EL display device can be made as thin as about 2 mm, and the pixel size can be reduced to 0.2 mm or less, so in principle, fine and clear display is possible. Since the insulating films 3 and 5 sandwiching it are both transparent, there is a problem in that so-called display crosstalk occurs between pixels, which tends to reduce the clarity of the display.

Figure 5 shows this crosstalk between two adjacent pixels P.
4 is a cross section taken along the line X-X in FIG. 4. Normally, the display voltage applied between the transparent electrode film 2 and the back electrode film 6 causes the portion of the light emitting film 4 corresponding to each pixel P to emit light, and this is taken out to the transparent substrate l side as the display light Ld. Since the film 4 itself is transparent, crosstalk light Lc is generated between adjacent pixel portions as shown in the figure. In addition to such direct losstalk inside the light emitting film 4, since the insulating film 5 is also transparent, indirect crosstalk light Lc is also generated which is reflected by the metal back electrode film 6 as shown in the figure.

In any case, the display light of each pixel mixes with the display light of the adjacent pixel due to such crosstalk, resulting in a decrease in the contrast on the display and a decrease in the sharpness of the displayed image.

Note that crosstalk can be considerably reduced by widening the mutual spacing between pixels P, that is, the mutual spacing between transparent electrode films 3, to half or more of the width of the pixels, but this clearly goes against the trend of miniaturization of displays, and the average brightness of displays decreases. A decline is inevitable.

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and reduce crosstalk between adjacent pixels to sharpen images displayed by an EL display device.

[Means to solve the problem]

The present invention aims to achieve this objective by adding a light-emitting film to each pixel in an EL display device that includes a light-emitting film and an insulating film between a front-side transparent electrode film and a back-side electrode film and displays pixels arranged in an array as described above. This is achieved by forming each pixel light-emitting film separately, and disposing a light-shielding film between the light-emitting film and the back electrode film so as to cover the space between the pixel light-emitting films and the back side.

It is most advantageous for the light-shielding film in the above structure to be an insulating light-absorbing film, and praseodyme manganese oxide, for example, can be used as the material therefor. If this light absorption film has good insulation properties, it is advantageous to replace the conventional back side insulation film with it. Furthermore, even if the light-absorbing film has good insulation properties, it may not be desirable to bring it into direct contact with the light-emitting film. In this case, for example, a very thin backside insulating film may be interposed between the light-absorbing film and the light-emitting film.

If the light-absorbing film does not have very good insulation, it is advantageous to directly cover the light-emitting film with it so that the insulation is mainly provided by the backside insulation film.

It is also possible to use a light-reflecting film as a light-shielding film, but the material for that is usually a conductive material such as metal.
In this case as well, it is best to interpose a very thin backside insulating film between the light-emitting film and the light-emitting film to prevent direct contact with it.By making this light-reflecting film a metal such as aluminum, it can be used as a backside electrode film. be able to.

[Function] The light-emitting film of conventional EL display devices is a continuous film that is common to all pixels, and although the structure of the display panel is simple, the light-emitting film itself is transparent, so crosstalk easily occurs between pixels, and the displayed image is Therefore, the area between the pixels of the light emitting film is originally an unnecessary part and is harmful because it becomes a crosstalk path. is divided into pixel light-emitting films for each pixel so as to eliminate the portion between the pixels.

Furthermore, in the present invention, a light-shielding film is disposed between the light-emitting film and the back electrode film to cover the space between the pixel light-emitting films, thereby blocking direct crosstalk light between adjacent pixel light-emitting films, and By also covering the back side of the light emitting film, the above-mentioned indirect loss talk light passing through the back side is blocked.

With this configuration of the present invention, crosstalk between pixels in an EL display device is almost completely prevented, and the above-mentioned problem is solved.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings. 1st
The drawings to FIG. 3 show different embodiments of the EL display device according to the present invention, and parts corresponding to those in FIG. 4 are given the same reference numerals, and all correspond to the cross section taken along the line X--X.

In either embodiment, a transparent glass plate with a thickness of about 1n is used as the substrate 1, a conductive film such as ITO is spattered onto it to a thickness of about 0.1n, and the transparent electrode film 2 is formed by photoetching to a thickness of, for example, 200μ. The stripes are formed with a width of 40n and an interval of 40n.

Next, for example, silicon nitride is deposited or grown to a thickness of about 0.4 nm for the front side insulating film 3 by sputtering or CVD. This insulator 113 can be made of silicon nitride, silicon oxide, or alumina, and it is desirable to improve its insulating properties by heat treatment if necessary after deposition.

For yellow monochrome display, approximately 0.5 for luminescent film.
Using ZnS containing wt% Mn, this is deposited to a film thickness of, for example, 0.5μ〇 by ordinary electron beam evaporation, and then dry etching or chemical etching using carbon tetrachloride or the like is performed in the present invention. By patterning it into stripes with the same array pitch as the transparent electrode film 2 and usually the same width, the pixel light emitting film 4p is separated for each pixel P. Alternatively, it is also possible to form the pixel light-emitting film 4p into such a striped pattern from the beginning by a vapor deposition method using a metal mask. As is well known, the luminescent properties of a luminescent film are improved by a predetermined forming process. The steps up to this point are the same in all embodiments of the present invention.

In the first embodiment of the present invention shown in FIG. 1, an insulating light absorbing film is used as the light shielding film 10, and the conventional back side insulating film is replaced with this film. For example, praseodium manganese oxide can be used for this light-absorbing light-shielding film 10, and Praseodium manganese oxide can be used.
A black insulating light-shielding film 10 is formed by depositing a sintered mixture of ++ and MnC0 to a thickness of, for example, 0.4 nm by sputtering using a sintered mixture of ++ and MnC0 as a target. In addition, CdTe+ CdSe+
Black dielectrics such as Sb, S, etc. and amorphous silicon can be used, but if particularly high insulation is required for this first embodiment, 1IIr! A slight increase in I- or a dielectric other than black may be used as appropriate.

Back electrode 1! I6 may be formed by photo-etching a metal such as aluminum deposited to a thickness of about 0.5 nm by sputtering or the like and patterning it into a striped arrangement in a direction perpendicular to the transparent electrode film 2 as shown in FIG. The EL display device of the first embodiment configured as described above is put into use after the heat treatment of the insulating film 3 and the forming of the pixel light emitting film 4p are completed.

When this display device is caused to emit EL by applying a display driving voltage between the transparent electrode film 2 and the back electrode film 6, each pixel electrode film 4
It is the same as the conventional method that the emitted light of p is extracted as display light Ld from the substrate l side in a direction almost perpendicular to the display surface, but the conventional crosstalk light Lc directed in a direction parallel to the display surface or toward the back side is emitted from the pixel light emitting film 4p. Since all of the light is blocked by the light-shielding film 1O that covers the space between them and the back side, the problem of crosstalk between pixels is almost completely solved in the EL display device of the present invention.

In the second embodiment shown in FIG. 2, the light-shielding film 11 is made to be light-absorbing, as in the previous example, but it is formed to a thinner film thickness of, for example, 0.1μ, so that the light-shielding film 11 is made light-absorbing. A back insulating film 5 made of silicon nitride or the like, which is the same as the front insulating film 3, is provided to cover the back side and between the back electrode film 6 and the back electrode film 6. This embodiment is suitable when it is desired to increase the dielectric strength of the display device, or when amorphous silicon or the like, which has high light absorption but does not have very high insulation properties, is used for the light shielding film 11. The thickness of the back side insulating film 5 is appropriately selected depending on the required dielectric strength voltage. The crosstalk prevention effect by the light shielding film 11 is the same as above.

In the third embodiment shown in FIG. 3, the back side insulating film 5a and the light-absorbing light shielding layer 1I110 are arranged in the reverse order of the second example, and the back side insulating film 5a in contact with the pixel light emitting film 4p is as thin as possible.
The back electrode film 6 is about 0.1n or less.
The light shielding film 10 disposed unevenly has a film thickness of, for example, 0.4 nm, which is the same as that of the first embodiment. In this third embodiment, the light shielding film 1
If the material for 0 is brought into direct contact with the pixel light emitting film 4p, it is suitable for cases where impurities that are undesirable for light emission are diffused, and by isolating the two with an insulating film 5a of good quality, it is possible to prevent impurities that may occur during the use of the ELL display device. It is possible to effectively prevent the light emitting characteristics of the pixel light emitting film 4p from easily deteriorating.

The light shielding film 10 of the third embodiment can almost completely eliminate crosstalk between pixels, as in the first embodiment. Note that the insulating film 5a in this embodiment may be coated with silicon nitride or the like, but dry etching is performed before the light shielding film 10 is coated to remove the portions between the pixel light emitting films 4p as shown in the figure. It is preferable to do so in order to reduce crosstalk between pixels as much as possible.

The present invention is not limited to the embodiments described above, but can be implemented in various embodiments. For example, as described above, the front insulating film 3 can be omitted as appropriate, and this is particularly easy in the second embodiment. In the example, all the pixel light-emitting films 4p were used for the same yellow display, but by sequentially changing the type of active substance to be added to the zrIS for the light-emitting center, it is possible to make the ELL display device display color. . In this case, the active substances are, for example, Ss for red, Tb for green, and B for blue.
The pixel light emitting films 4p for emitting these three colors are formed in square patterns corresponding to each pixel. In addition, in the embodiment, the light-shielding films 10 and 11 were all light-absorbing films, but
This can also be used as a light reflecting film. However, since the light reflecting film is made of a conductive material such as metal, direct contact with the pixel light emitting film 4p is not desirable, so a thin back side insulator 1115a as shown in FIG. 3 is interposed between the light reflecting film and the pixel light emitting film 4p. If this light reflecting film is made of aluminum, it can also be used as the back electrode film 6, and the E
This is particularly advantageous in simplifying the structure of the LL display and in producing the above-mentioned color display.

〔Effect of the invention〕

As described above, in the present invention, for an EL display device that includes a light emitting film and an insulating film between the transparent electrode film on the substrate side and the back electrode film and performs display of arrayed pixels, the light emitting film is attached to each pixel for each pixel. The following effects can be achieved by dividing the light-emitting film and disposing a light-shielding film between the light-emitting film and the back electrode film so as to cover the space between and the back side of the pixel light-emitting film.

(a)i! A light-shielding film placed between the back electrode films of the pixel light-emitting films covers the space between the pixel light-emitting films and the back side of the pixel light-emitting films, preventing direct crosstalk between adjacent pixel light-emitting films and indirect crosstalk via the back side. By blocking the talk light, E
Crosstalk between pixels of a LL display device can be almost completely prevented.

(b) According to an embodiment in which the light-shielding film is an insulating light-absorbing film, crosstalk can be prevented without complicating the structure while effectively using this as an insulating film; According to this method, it is possible to effectively utilize scattered light to improve display brightness while preventing crosstalk.

(C)ii! Since it is divided into each element of the luminescent film element,
This is particularly advantageous in switching the display color for each pixel when displaying a color display in an ELL display device, preventing crosstalk between pixels, that is, color mixture, and sharpening the displayed image.

The ELL display device embodying the present invention has high display contrast and clear images especially when the display is miniaturized, and while taking advantage of its inherent advantages as a flat self-luminous panel, it can be used at the display end of computers, etc. It is expected that this technology will contribute to further improvement in performance and widespread use.

[Brief explanation of drawings]

1 to 3 are partially enlarged cross-sectional views of an ELL display device showing different embodiment structures of the present invention, respectively. Figure 4 and subsequent figures relate to the prior art, and Figure 4 is EL.
FIG. 5 is a partially cutaway perspective view showing the conventional structure of an L display device, and FIG. 5 is a partially enlarged sectional view showing crosstalk on pixel display. Note that FIGS. 1 to 3 and FIG. 5 correspond to the cross section taken along the line X--X in FIG. 4. In these figures, d: substrate, 2: transparent electrode film, 3: front side insulating film, 4: light emitting film, 4p: ill
Light-emitting film 5: back side insulating film, 5a: thin back side insulating film, 6:
Back electrode film, lo: light shielding film, 11: ll light shielding film, L
c: crosstalk light, Ld+display light, P: pixel. Figure 2

Claims (1)

[Claims] A device that includes a light-emitting film and an insulating film between a transparent electrode film on the substrate side and a back electrode film, and displays pixels arranged in an array, in which the light-emitting film is divided into pixel light-emitting films for each pixel. An EL display device in which a light-shielding film is disposed between the light-emitting film and the back electrode film so as to cover the space between the pixel light-emitting films and the back side of the pixel light-emitting films.