JPH0420994B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of manufacturing a shadow mask used in a color picture tube, and particularly to an etching method thereof.

[Technical background of the invention and its problems]

A shadow mask used in a color picture tube is an important member that is placed close to and facing a fluorescent surface consisting of a group of different emitted colors, and performs a color selection function through a large number of regularly arranged apertures. This shadow mask is usually made by etching a large number of holes from a strip-shaped thin metal plate. The opening area on the surface is large (hereinafter referred to as a large hole), and the opening area on the electron gun side is approximately the same as the through-hole diameter and smaller than that on the fluorescent surface side (hereinafter referred to as a small hole).

When apertures having such a complicated cross-sectional shape are formed by etching, the accuracy and reproducibility decrease as the aperture diameter becomes smaller, and it is difficult to obtain an aperture diameter smaller than the thickness of the plate. As a method of obtaining such an opening diameter smaller than the plate thickness,
In the publication No. 26345, a proposal as shown in FIGS. 1 and 2 is made. That is, the metal surface corresponding to the large and small holes to be etched in the metal plate 1 is exposed,
The metal plate 1 is covered with etching-resistant resist films 2a and 2b, with the metal surface forming the large hole D _a facing down, and the desired depth is etched from both sides of the metal plate 1 in zone a. That is, after performing the first stage etching to the remaining thickness H of the metal plate, it is washed with water in zone b and dried in zone c. Next, a material that is resistant to etching liquid, such as asphalt, paraffin, or polymeric plastic, is sprayed on the metal plate surface in which the small holes D _b have been formed in zone d, and dried in zone e. A resistive layer 3 is formed. Thereafter, a second stage of etching is performed only from the large hole D _a side in zone f, and etching is continued until the resistive layer 3 filling the small hole D _b is reached and the desired hole size is reached. After etching, wash with water,
Send to the next step (g) such as stripping the resistive layer and resist film.
It is said that a shadow mask having a hole size of about 40% of the thickness of the metal plate can be obtained by such a method.

However, the resist layers 2a and 2b, which cover areas other than the pore forming areas, are generally etched from both sides with the small pores on the top and the large pores on the bottom after normal exposure, development, drying and burning, and then washed with water. If drying is carried out, the etching resistance will decrease and the resist shape will be distorted. Therefore, when etching is performed from the large hole side in the latter stage, the adhesion between the resist layer 2a and the metal plate 1 is reduced, so the amount of side etching increases, and variations in hole size are likely to occur. Due to the shape distortion of the resist film portion, the pore shape is disturbed and the quality of the shadow mask is degraded.

In addition, after the first step of etching is completed, the small holes are filled with a resistive material, but the most difficult point during this filling is the third step.
As shown in the figure, the resist layer 2b in the small hole portion partially exists in the form of an eaves 2c due to side etching during the previous etching process, and this eave portion 2c becomes a major obstacle to the flow of the resistive material into the recess. That is, when the resistive material is filled into the recess by dipping or spraying, the air in the vicinity of the eaves 2c is not completely removed and tends to remain partially in the form of bubbles. As a result, during the subsequent etching process, the etching progresses faster in areas where air bubbles exist than in areas that are completely filled, resulting in the problem that defects are more likely to occur in the hole shape.

Furthermore, when etching is performed with the small hole part, which determines the hole size, on the upper side, the distribution of the etching solution that accumulates on the metal plate is not uniform, and it is difficult to obtain the same recess size in all the small hole parts. Interfering with the progress of etching. As a result, there is a problem in that the hole dimensions vary.

[Purpose of the invention]

The present invention has been made in view of the above points, and it is an object of the present invention to uniformly form openings having dimensions smaller than the thickness of the metal plate of the shadow mask over the entire surface of the shadow mask.

[Summary of the invention]

In the present invention, first, pre-etching is performed on both sides of a thin metal plate to form predetermined recesses, and the etched surfaces are washed with water, the resist film is peeled off, washed with water and dried, and then the metal plate is turned over to form the upper side. An etching resistance layer is formed only in the recesses, and in the process from the end of the previous etching to the formation of the resistance layer, the surface on the large hole side is washed with water to protect it from adhesion of the resist film stripping solution and the resistance layer material, and the resistance layer is removed. After the protective means is removed, a predetermined recess is formed by etching with the side where the protection means is not formed facing downward, and a through hole is formed in a predetermined shape by the subsequent etching, and then washed with water to remove the resistive layer and the resist. A shadow mask having through-holes smaller than the thickness of the thin metal plate is obtained by peeling off the film, washing with water, drying, and always etching only from the bottom to prevent the etching solution from pooling.

[Embodiments of the invention]

Examples of the present invention will be described in detail below.

Embodiment 1 FIG. 4 is a block diagram of a metal plate for each step according to an embodiment of the present invention, and FIG. 5 is a schematic diagram showing each step.

A smooth aluminum-killed low-carbon steel plate 4 with a thickness of 0.13 mm is used as a shadow mask material, and a photosensitive solution consisting of alkali milk caseinate and ammonium dichromate is applied to both main surfaces and dried to form a resist film of approximately 5 μm. Next, on one main surface of the thin metal plate 4, approximately
A negative master plate with a circular image of 80 μm and a negative master plate with a circular image of approximately 150 μm are placed in close contact with each other on the corresponding part of the other main surface, and exposed for 30 seconds from a distance of 1 m using a 5KW mercury lamp. . then 40
The unexposed and uncured portions of the resist film are dissolved and removed using hot water at a temperature of 1 kg/cm ² at a spray pressure of 1 kg/cm 2 to expose the metal surfaces 7 and 8 corresponding to the small hole forming portion and the large hole forming portion (Fig. 4 a). ). Thereafter, in order to improve the etching resistance of the remaining resist films 5 and 6 and the adhesion strength with the thin metal plate 4, the remaining resist films 5 and 6 were dried for about 2 minutes in an atmosphere of 150°C and then heated to 200°C.
Burn for about 2 minutes in an atmosphere of Next, etching is carried out by spraying etching liquid 9 from both sides of the metal plate until the desired recesses 10 are formed (FIGS. 4b and 5a), followed by washing with water (FIG. 5b) and drying (FIG. 5b). (not shown). Here, when the previous stage etching is completed, polyethylene is placed on the large hole side of the metal plate 4.
A protective film 11 made of polypropylene or vinyl chloride is attached (FIG. 4c) to protect the recess on the large hole side up to the subsequent etching. Next, a sodium hydroxide solution with a concentration of 15% and a temperature of 60° C. is sprayed from the small hole side to peel off the remaining resist film on the small hole side (Fig. 5c), and the resist film is washed with water (Fig. 5d) and dried. Next, the metal plate is turned over (Fig. 4c) so that the side surface of the small hole formed by the previous etching is placed on top, and a water-soluble etching-resistant material such as milk caseinate alkali or polyvinyl alcohol is applied to this side using a roller coater. , epoxy dispersion resin, alkyd resin, etc. are applied (Fig. 5 e), and the recesses on the small hole side are completely filled and dried (Fig. 5 f), thereby forming the resistance layer 12 (Fig. 5 f). Figure 4 d). In addition to the roller coating method, the resistive material may be applied by a spray method, a dipping method, or a bar coater method. In addition, the resistive material must have etching resistance, and if water-insoluble materials such as paraffin, petroleum pitch, lacquer, etc. are used in addition to the above, the remaining resist film 5 on the small hole side must be peeled off, washed with water, and then dried. It is preferable to form the resistance layer 12 by using the following steps.

Now, after forming the resistance layer 12, the protective film 11 on the large hole side is peeled off, and etching is performed by spraying the etching liquid 9 only on the large hole side located below the metal plate (Fig. 5g). The large hole side concave portion reaches the resistance layer 12 to obtain a shadow mask opening of the desired size (FIG. 4e). Then resistive layer 1
2 and the resist film 6 are removed (FIG. 5h), and the opening forming process is completed (FIG. 4f).

The thus obtained shadow mask is of high quality, with excellent hole shape, no defects, and hole size smaller than the metal plate thickness and without variation. In the above embodiments, if the resistive material does not adhere to the lower side of the metal plate due to the resistive material coating method, the protective film may be peeled off before the resistive material coating step.

Embodiment 2 FIGS. 6 and 7 show a chamber and a process diagram of a second embodiment of the present invention. In this example, the steps from resist film application to the preceding etching process are the same as in Example 1. The steps a to h in FIG. 7 are similar to and correspond to the steps in FIG. 5, respectively.
In order to prevent resist film stripping liquid, resistive material, etc. from adhering to the large hole side between the end of the first stage etching and the second stage etching, as shown in FIGS. 6a and 6b, the running part of the metal plate 4 is The subsequent etching steps are carried out in an etching chamber 13 having a shielding plate 14 on the side surface of the corresponding chamber. There are various possible structures for this shielding plate, and FIG. 6 shows one example, in which the metal plate is held down by a rubber roller 15 so that it does not lift up from the shielding plate due to the force of the etching liquid blowing up from below. It has a structure that attaches. That is, after etching is completed, the etching solution adhering to the small hole side is washed away using a washing chamber having the above-mentioned shielding plate (Fig. 7b), and then the resist film stripping chamber having the same shielding plate is used to wash away the etching liquid adhering to the small hole side. Example 1 of resist film
Remove with sodium hydroxide solution in the same way as (Figure 7c)
After that, it is washed with water (FIG. 7d) and dried (not shown). Thereafter, the metal plate was turned over, and the etching resistance material was applied to the small hole side located on the upper side of the metal plate in the same manner as in Example 1 using a resistance material coating chamber having a similar shielding plate, with the small hole portion where the recess was formed facing upward. A resistive layer is formed by applying the resistive layer (FIG. 7e) and drying it (FIG. 7f). Next, in an etching chamber that does not have a shielding plate, etching is carried out by spraying the etching solution only on the large hole side from below (Fig. 7g), so that the large hole side recess reaches the resistive layer and the intended purpose is achieved. Obtain a shadow mask aperture with dimensions as follows. Next, the resistive layer and resist film are peeled off to complete the opening forming process (FIG. 7h).

In this example, a resistance layer was formed on the small hole side.
Needless to say, it may be formed on the large hole side.

Further, if the resistive material is not attached to the lower side of the metal plate depending on the method of applying the resistive material, the resistive material coating chamber does not need to have a shielding plate.

Embodiment 3 FIG. 8 shows a process diagram of a third embodiment of the present invention, but in this embodiment as well, the steps from resist film coating to the preceding etching step are the same as in Embodiment 1, and the explanation thereof will be omitted. Further, the steps a to h in FIG. 7 are similar to and correspond to the steps in FIG. 5, respectively. In order to prevent resist film stripping solution, resistive material, etc. from adhering to the large hole side between the end of the first stage etching and the second stage etching, a magnetic sheet is pasted as a protective film 11 and the resist stripping process (Fig. 8c) is performed. ) to resistive material coating process (Fig. 7d)
Implement up to. This magnetic sheet is preferably one in which a magnetized material is applied to the surface of a rubber sheet or a flexible plastic sheet, or one in which the magnetized material is impregnated, and it is annular and can be used continuously. be. Therefore, after etching is completed (Fig. 8a), the etching solution adhering to the small hole side is washed away using a washing chamber (Fig. 8b), and after drying (not shown), the magnetic sheet is placed on the large hole side. After gluing, in the next resist stripping chamber, only the resist film on the small hole side was removed with a sodium hydroxide solution in the same manner as in Example 1 (FIG. 8c), followed by washing with water (FIG. 8d) and drying. Thereafter, the metal plate was turned over so that the small hole with the recess was placed on the upper side, and a resistive layer was formed only on the small hole side in the same manner as in Example 1 while leaving the magnetic sheet attached to the large hole side (Fig. 8e). ) and dry (Figure 8f). At this time, the magnetic sheet is peeled off from the large hole side after the resistive material application step (FIG. 8e) and circulated back to before the resist film stripping step of FIG. 8c. The subsequent steps are the same as in Example 1.

〔Effect of the invention〕

In the case of spray etching, it is preferable to spray the etching solution from below both the large hole and the small hole to avoid the influence of liquid pooling. However, if both the first and second stages are etched from below, the time required for etching will be longer, production efficiency will be lowered, and mass productivity will be lacking. By etching simultaneously from both sides of the large hole and small hole side, with the large hole side that is not etched as the upper side, and etching only from the bottom side in the latter stage, the hole shape is excellent, there are no hole defects, and the thickness is smaller than the thickness of the metal thin plate. A high-quality shadow mask having uniform hole sizes can be obtained.

[Brief explanation of drawings]

Figure 1 is a schematic process diagram showing the conventional hole forming process, Figure 2 is a schematic diagram showing the cross-sectional state of the hole in the middle of the process in Figure 1, and Figure 3 is for explaining side etching of the hole. Schematic diagram of Figures 4a to 4f
is a schematic cross-sectional view showing the shape of the hole in the hole formation process of the embodiment of the present invention, FIG. 5 is a schematic process diagram showing the hole formation step of FIG. 4, and FIGS. 6a and 6b are A schematic cross-sectional view and a perspective view showing an example of a shielding plate, and FIGS. 7 and 8 are schematic process diagrams showing a hole forming step in another embodiment of the present invention. 4... Metal plate, 5, 6... Resist film, 7, 8
...Exposed metal surface, 9...Etching liquid, 10...
recess, 11...protective film, 12...resistance layer,
13...chamber, 14...shielding plate.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a shadow mask in which a large number of regularly arranged through holes are formed in which the aperture area on one surface of a thin metal plate is different from the corresponding aperture area on the other surface, A portion of both sides of the thin metal plate other than the predetermined aperture area is covered with an etching-resistant resist film, and the smaller aperture area is placed on the lower side, and the etching is performed at a stage earlier than the both sides of the metal thin plate. to form a predetermined recess, wash the surface on which the recess is formed, remove only the resist film on the side of the smaller opening area, wash with water and dry, then turn the metal plate over and remove the resist film on the side of the smaller opening area. An etching resistance layer is formed only on the metal surface, and in the process from the end of the previous etching to the formation of the resistance layer, the surface different from the smaller opening area is washed with water, and the resist film stripping solution and resistance layer material are attached. A predetermined recess is formed by etching in the subsequent step with only the surface on which the resistive layer is not formed facing downward, and a through hole in a predetermined shape is bored through the etching in the subsequent step. A method for manufacturing a shadow mask, which comprises washing with water, peeling off the resistive layer and resist film, washing with water and drying to obtain a shadow mask having through holes smaller than the thickness of the thin metal plate. 2. The method of manufacturing a shadow mask according to claim 1, wherein a surface different from the smaller aperture region after the end of the previous etching step is protected with an organic synthetic film. 3. The shadow mask according to claim 1, characterized in that a surface different from the smaller opening after the end of the previous stage etching is protected by a ring-shaped magnetic sheet that can be used cyclically. manufacturing method. 4. Protection of a surface different from the smaller opening after the end of the previous etching is performed by an etching chamber having a shielding plate for preventing adhesion of liquid from scattering. How to make a shadow mask.