JPH05108014A - Formation of light emitting film for color display of el display panel - Google Patents

Abstract

(57) [Summary] [Objective] The manufacturing process of an EL display panel in which color display pixels are arranged in a matrix on a display surface is rationalized, and the generation of defective pixels when a light emitting film for color display is formed is reduced. [Structure] A mask plate having a window pattern corresponding to an electrode film portion for pixels of the same display color is arranged almost in contact with the panel surface, and a light emitting film portion of the same display color is selectively placed at the position of the window pattern. In addition, the light emitting film parts with different display colors are sequentially formed by shifting the positions for each display color by omitting the patterning step for the light emitting film and absorbing moisture during wet etching of the light emitting film. This prevents defective pixels from occurring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming method for incorporating a light emitting film for color display into an EL (electroluminescence) type display panel having a thin film laminated structure.

[0002]

2. Description of the Related Art EL display panels have come to be widely used as lightweight and thin display devices for personal computers and OA equipment by taking advantage of their self-luminous property and so-called flat panel structure, but at present, they are still in use. At the stage where a single color display is put into practical use, color display is being advanced to improve display performance. In order to display a video image or the like in color, it is necessary to arrange a light emitting film made of a material that emits EL light of these colors as a display pixel of each color of RGB in a matrix pattern on the panel surface in a small pattern. Will be described with reference to FIG.

FIG. 2A shows a state before the light emitting film is provided. A transparent conductive film such as ITO is deposited on the surface of the transparent glass substrate 1 of the EL display panel and photoetching is performed to form the transparent electrode film 2 in a striped pattern elongated in the left-right direction of the drawing. A large number of them are arranged side by side in the front-back direction, and an insulating film 3 made of SiO ₂ , Si ₃ N ₄ , Ta ₂ O ₅ , Al ₂ O ₃ or the like is deposited on the entire surface to obtain the state shown in the figure.

2 (b) and 2 (c) show a process of disposing the light emitting film 4g for green display. As the material of the light emitting film 4g, a base material made of ZnS to which a small amount of Tb is added as an emission center element is used. In FIG. 2 (b), this is formed on the insulating film 3 by the electron beam evaporation method. After that, the photoresist film 30 is spin-coated and formed into a small pattern corresponding to each pixel by a photo process. Figure 2 (c) shows the patterning process of the light-emitting film 4g using the photoresist film 30 as a mask. The chemical etching method has been conventionally used for this, and it is immersed in an aqueous solution of hydrochloric acid or nitric acid, washed with water, The light emitting film 4g is brought into the state shown in the drawing through a work such as peeling.

As a material for the light emitting film 4r for red display shown in FIGS. 2D and 2E, a material containing Eu as an emission center element in a base material of CaS is used. 2D, a photoresist film 30 is formed on the entire surface and a photoresist film 30 is formed thereon in a predetermined pattern. Then, in FIG. 2E, the light emitting film 4r is patterned for each pixel by chemical etching. For the material of the light emitting film for blue display
Using a material in which Ce is added to the base material of SrS, the light emitting film 4b for blue display pixels shown in FIG. 2 (f) is formed in the same manner as described above.

Thereafter, as shown in FIG. 2 (f), an insulating film 5 is deposited in the same manner as the insulating film 3 so as to cover these light emitting films 4g, 4r, 4b, and aluminum is deposited on the upper side thereof. Then, the back electrode film 6 is arranged in a striped pattern in the front-rear direction of the drawing by photoetching to complete the structure.
This EL display panel applies a display voltage between the electrode films 2 and 6 to cause the light emitting films 4g, 4r, 4b for pixels at the intersections of the two to emit EL light in three colors of green, red and blue, respectively. Color display is possible.

[0007]

As described above, in the EL display panel for color display, a single continuous film may be used as the light emitting film in the case of monochromatic display, whereas three types of light emitting films for RGB are used. Since it is necessary and it is necessary to pattern each into an individual pattern for each pixel, the number of manufacturing steps increases and it is very troublesome, and defective pixels are likely to occur during the patterning step of the light emitting film for color display. Therefore, there is a problem that the manufacturing yield is lowered, which is a bottleneck for practical use.

The main cause of defective pixels is that the base material of the light-emitting film, especially CaS for red display pixels and Sr for blue display pixels.
The point is that S is hygroscopic, and conventionally, a wet process using water such as development of a photoresist film, chemical etching, and water washing is used for its patterning. For example, when the light emitting film for a certain color is patterned or during the wet process when the light emitting film for another color is patterned in a later step, the light emitting film having a small pattern for each pixel absorbs moisture. This is because defective pixels such as peeling from the base are likely to occur.

The object of the present invention is to solve the above problems,
An object of the present invention is to provide a method for forming a light emitting film for color display of an EL display panel, which can help streamline the manufacturing process of the color display EL display panel and reduce the occurrence of defective pixels.

[0010]

According to the present invention, the above-mentioned object is achieved by forming the same display when forming a light emitting film for RGB color display pixels arranged in a matrix in the display surface of an EL display panel. With the mask plate provided with the window pattern opened corresponding to the light emitting film portion for the color pixel being arranged almost in contact with the panel surface, the light emitting film portion for this display color is selectively applied to the position of each window pattern. In addition, it is achieved by simultaneously forming films on the display surface, and sequentially forming the light emitting film portions having different display colors while shifting the positions for each display color.

It is desirable to use a vacuum vapor deposition method, in particular, a vacuum vapor deposition method of electron beam heating, for forming the above-mentioned light emitting film portion in order to increase the emission brightness. However, the steps of the laminated structure with the insulating film are unified. In order to reduce the manufacturing cost, it is advantageous to use the sputtering method for forming the light emitting film portion for the display color. The mask plate may be a thin metal plate having a large number of window patterns for each pixel opened by photo-etching or the like.
Since the arrangements of the respective color display pixels of GB in the panel surface are slightly deviated from each other, they can be commonly used for forming the light emitting films for these three colors.

Further, in the method of the present invention, the light emitting film portions having different display colors are formed so that the peripheral portions thereof overlap each other. This prevents the dielectric breakdown and deterioration of the insulating film on the upper side thereof and increases the light emitting area of each pixel. It is advantageous in taking. For this purpose, the size of the window pattern of the mask plate is preferably set to be approximately the same as the width of the above-mentioned striped pattern of the transparent electrode film or the back electrode film.

[0013]

As described above, according to the present invention, the mask plate having the window pattern corresponding to the pixels of the same display color is used, and the mask plate is provided so as to be almost in contact with the panel surface. By forming a light-emitting film portion of a corresponding small pattern, it is possible to simplify the manufacturing process of the display panel by eliminating the need for patterning after film formation, and to apply a wet process to the hygroscopic light-emitting film as in the past. It eliminates the need and reduces the occurrence of defective pixels.

[0014]

EXAMPLE An example of a method for forming a light emitting film for color display according to the present invention will be described below with reference to FIG. The state before film formation of the light emitting film part is shown in Fig. 10 (a), the green state in Fig. 10 (b) to (d),
The state at the time of forming the light emitting film portion for red and blue color display,
Part (e) of the completed EL display panel is shown in an enlarged cross-section. Since the same reference numerals are given to the portions corresponding to the previous FIG. 2, the description of the overlapping portions will be appropriately omitted.

FIG. 1 (a) shows the same state as that of FIG. 2 (a) before the formation of the light emitting film. The transparent electrode film 2 is formed of, for example, a conductive film having a film thickness of 2000 Å. For the insulating film 3, for example, Si ₃ N _{4 is used.}
The film is deposited with a film thickness of about 3000 Å by the sputtering method. A mask plate is used for all film forming steps shown in FIGS. 1 (b) to (d) below.
Use 10. It is preferable to use a thin metal plate made of, for example, stainless steel with a thickness of 0.1 to 0.5 mm for the mask plate 10, and 0.3 to 0.5 m corresponding to each pixel for color display.
The m-square window pattern 11 is opened as illustrated by, for example, a photoetching method. The size of the window pattern 11 is preferably set to be substantially the same as the stripe width of the back electrode film 6 shown in FIG. The mask alignment of the mask plate 10 to the substrate 1 is performed with an accuracy of several tens of μm.

In the step of forming the light emitting film portion 4g for green display shown in FIG. 1 (b), light emission using ZnS containing a small amount of Tb as a base material is performed with the mask plate 10 positioned so as to be almost in contact with the panel surface. The film portion 4g is selectively vapor-deposited or deposited on the insulating film 3 in the window pattern 11 of the mask plate 10 with a film thickness of 5000 to 8000Å by, for example, a vacuum evaporation method in which an evaporation source is heated by an electron beam. At this time, the mask plate 10 does not completely come into close contact with the panel surface and actually rises slightly, so that a slight sag or inclination may occur at the peripheral edge of the light emitting film portion 4g as shown in the drawing, but there is no problem. In the method of the present invention, the process shown in FIG. 1 (b) can be immediately followed by the process shown in FIG. 1 (c).

FIG. 1 (c) shows a film forming process of the light emitting film portion 4r for red display, which is a mask plate 10 dedicated to it or shared with the previous process.
In the same manner as above, the light emitting film portion 4r using Eu-added CaS as a base material is positioned in such a manner that it is almost in contact with the panel surface, and the window pattern 11 of the mask plate 10 is formed to a similar film thickness in the same manner as before.
The film is selectively formed at the position. The peripheral portion of the light emitting film portion 4r slightly overlaps the peripheral portion of the light emitting film portion 4g formed in the previous step as shown in the figure. The film forming process for the light emitting film portion 4b for blue display shown in FIG. 1 (d) is the same, and Ce is added.
In the mask plate 10 in which the light emitting film portion 4b for blue display having SrS as a base material is positioned so as to have a similar film thickness in the same manner as the step of FIG. 1 (b) from the step of FIG. 1 (c). A film is selectively formed at the position of the window pattern 11.

In the embodiment shown in FIG. 1, the light emitting film portions 4g, 4r, 4b for displaying green, red and blue are used for convenience, as in the conventional example shown in FIG.
However, in the present invention, there is no need to turn it on to the subsequent step because the hygroscopic film having a high hygroscopic property needs to be sent to the subsequent step because the wet process is conventionally used. The film forming order of the film portions 4g, 4r, 4b may be arbitrary. Further, although the film formation is performed by the vacuum vapor deposition method in the above, it is of course possible to use the sputtering method or the plasma CVD method for the film formation.
In particular, the sputtering method has the advantage that the insulating films 3 and 5 are deposited by the same method, and that the process matching is good in forming a laminated structure with them. In the case of this sputtering method, the electrode plate on which the substrate 1 is mounted or the transparent electrode film 2 when the film is formed.
By applying a high frequency electric field for bias to the mask plate 10 and applying a DC bias voltage in the opposite direction to the mask plate 10, the amount of the light emitting film material deposited on the mask plate 10 can be reduced.

In order to complete the EL display panel of FIG. 1 (e), first, the insulating film 5 is formed on the light emitting film portions 4g, 4r, 4b with the same material and the same thickness as the insulating film 3 and with the same film thickness. Form a film. At this time, as can be seen by comparing with FIG. 2 (f), in the method of the present invention, since the upper surfaces of the light emitting film portions 4g, 4r, 4b are much flatter than in the conventional case and there is no step, the insulating film 5 can be formed with good film quality. Moreover, since the light emitting film portion has no corners, the electric field concentration on the insulating film 5 is much less, and the risk of dielectric breakdown or insulation deterioration during long-term use of the EL display panel is reduced. Next, the aluminum
The back electrode film 6 having a film thickness of about 5000Å is arranged in the same manner as the conventional one, and the completed state of the drawing is obtained. In the EL display panel according to the present invention, the EL emission area of each pixel can be made wider than in the conventional case of FIG. 2 (f).

[0020]

As described above, according to the method of the present invention, it is the same in the state that the mask plate having the window pattern opened corresponding to the light emitting film portion for the pixels of the same display color is arranged almost in contact with the panel surface. By selectively and simultaneously forming the light emitting film portion of the display color at the position of each window pattern, and sequentially forming the light emitting film portion of different display color for each display color, the following effects can be obtained. Obtainable.

(A) Since the light emitting film portion is formed into a small pattern corresponding to each display color pixel using a mask plate having a window pattern, patterning is performed after the formation of the light emitting film as in the conventional case. It is not necessary, the number of manufacturing steps of the EL display panel can be reduced, and the manufacturing cost in mass production can be significantly reduced. (b) Since it is not necessary to perform a wet process for patterning the light emitting film portion as in the conventional case, generation of defective pixels due to moisture absorption of the light emitting film is reduced to improve yield in mass production of EL display panels. be able to. (c) Since it is not necessary to separate the light emitting film portions from each other to perform etching as in the conventional case, the surface of the light emitting film becomes almost flat, and the insulating film on the light emitting film has a good film quality on the underlying surface with few steps. It is possible to form a film by the method described above, and it is possible to improve the long-term reliability of the EL display panel by reducing the concentration of an electric field on the insulating film to prevent the generation of defective pixels due to insulation breakdown or insulation deterioration and the deterioration of display brightness. (d) Since the peripheral portions of the light emitting film portions of different display colors can be formed so as to overlap slightly, the effective area of the light emitting film portion for each display color pixel is increased to increase the EL light emission amount, and the color display of the display panel is performed. Can be brightened.

As described above, the method of the present invention is applied to the E for color display.
The L display panel has the effects of reducing the manufacturing cost by simplifying the manufacturing process and improving the manufacturing yield, and improving the display performance and the long-term reliability. Especially, when applied to mass production, these effects can be advantageously exhibited. It is possible to solve the conventional problems in the mass production of color EL display panels and to contribute to the development of a bottleneck for practical use.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of an EL display panel showing an embodiment of a method for forming a light emitting film for color display according to the present invention.
(a) shows the state before film formation of the light emitting film portion, (b) shows the state when the light emitting film portion for green display is formed, and (c) shows the light emitting film portion for red display. FIG. 6D is a cross-sectional view showing a state of film formation, FIG. 7D shows a state of film formation of the light emitting film portion for blue display, and FIG. 8E shows a state of the EL display panel when completed.

FIG. 2 is a partially enlarged cross-sectional view showing a method of manufacturing a conventional EL display panel for color display, where FIG. 2 (a) shows a state before a light emitting film is formed, and FIG. 2 (b) shows a display for green display. The state of the light-emitting film during film formation is shown in Fig. 6 (c).
(d) shows the state when the light emitting film for red display is formed, (e) shows the state during patterning, and (f) shows the film formation and patterning of the light emitting film for blue display. Sectional drawing showing each completed state of EL display panel including process

[Explanation of symbols]

 1 EL display panel substrate 2 Transparent electrode film 3 Insulating film 4b Light emitting film part for blue display 4g Light emitting film part for green display 4r Light emitting film part for red display 5 Insulating film 6 Back electrode film 10 Mask plate 11 Window pattern

Claims (3)

[Claims] 1. A method of forming a light emitting film for color display on an EL display panel in which color display pixels are arranged in a matrix on a display surface, the method corresponding to a light emitting film portion for pixels of the same display color. With a mask plate with an open window pattern almost in contact with the panel surface, the light-emitting film portions of the same display color are selectively and simultaneously formed at the positions of the window patterns to emit light of different display colors. A method for forming a light-emitting film for color display of an EL display panel, wherein the film portions are sequentially formed by shifting the position for each display color. 2. The method of forming a light emitting film for color display according to claim 1, wherein the light emitting film portions having different display colors are formed so that their peripheral portions overlap each other. 3. The method for forming a light emitting film for color display according to claim 1, wherein the light emitting film portion is formed by a sputtering method.