JPS6139345A - Shadow mask - Google Patents

Abstract

PURPOSE:To prevent textural unevenness over a shadow mask for a color picture tube occurring on etching, by forming the shadow mask while removing the surface oxide layer evenly by using mild steel etc., and by forming pores by photoetching. CONSTITUTION:Over a plate material of a mild steel-or iron-nickel type alloy, iron-nickel-cobalt type alloy, etc., a polishing process not depending on the rolling direction, such as a chemical polishing or sand blasting is applied to remove evenly the surface oxide layer, to make up the material, then numerous circular pores are formed thereon by photoetching, and a shadow mask for a color picture tube is made up. Thus, textural unevenness occurring on etching is prevented by avoiding to leave easy and hard etching portions mixed over the material, a high accuracy of the shadow mask being acquired.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a shadow mask, and more particularly to a high-precision, high-definition shadow mask.

[Technical background of the invention and its problems] Immediately in front of the color picture tube fluorescing surface, a shadow mask is arranged which has a large number of apertures (dot-shaped, blind-shaped) formed based on predetermined design standards. It is set up.

The material for this shadow mask usually has a thickness of about 0.
A thin mild steel plate of 15IllIl is used. recently,
Invar alloys, which are iron-nickel alloys with low thermal expansion characteristics, are beginning to be adopted.

This shadow mask board is manufactured as follows.

First, the material is melted and forged, then hot rolled to form a plate, and then mechanically ground to a roughness of about 80 mesh (hub polishing, belt grinding, scalping, etc.) to remove any oxides that have formed on the surface of the plate. After that, cold rolling and annealing are repeated, and finally finish rolling is performed to produce a plate material for a shadow mask.

Next, a shadow mask is manufactured using this plate material as follows.

First, this plate material is cleaned, coated with photoresist, exposed, and then etched with ferric chloride to form holes.

After that, the entire surface is pressed to form a curved surface with a predetermined radius of curvature, and finally the entire surface is blackened by steam oxidation to improve thermal radiation and prevent diffused reflection.

However, in the shadow mask manufactured as described above, streak-like unevenness with a width of about 0.5 to 5 mm may occur during etching. The present inventors studied this uneven streaking and found that the opening speed of the shadow mask is different between the striped part and the non-striped part, and as a result, the light transmittance is different.
It was determined that this was visible as a streak-like unevenness.

[Object of the Invention] An object of the present invention is to provide a shadow mask without uneven streaks.

[Summary of the Invention] As a result of intensive research into shadow masks, the present inventors discovered that this streaking occurs in the rolling direction of the plate material, and that oxides are mainly removed from the surface of the plate material during the manufacturing process of the plate material. It was found that the occurrence depends on the

The present invention was completed based on this knowledge.

That is, the shadow mask of the present invention is characterized in that the surface layer is uniformly removed.

In other words, the oxide layer is removed by continuous puff polishing and
This is done by mechanical grinding such as belt grinding or scalping, but if the surface oxidized layer is not removed uniformly, streaks will remain. However, although the surface becomes smooth during cold rolling in the subsequent process, when a shadow mask is manufactured using this plate material, there remain streak-like areas on the surface that are easy to etch and areas that are difficult to etch. Because of this, uneven streaks appear during the etching process.

Therefore, by uniformly removing the surface layer, this uneven streaking can be prevented.

As a method for preventing this, any polishing method that does not depend on the rolling direction may be used, such as a chemical polishing method and a sandblasting method.

That is, by using a method of spraying a liquid such as an acid or a solid powder, the surface oxidation layer can be uniformly removed. Furthermore, even when using mechanical grinding that depends on the rolling direction, the surface can be uniformly removed by dividing the process into multiple steps and sequentially changing the roughness.

Specifically, after hot rolling, first mechanical grinding is performed to a roughness of about 60 to 100 mesh, and then to a roughness of 150 to 3
It is preferable to perform a second mechanical grinding with a roughness of about 0.00 mesh. Further, it is desirable that the second mechanical grinding be performed during the process of repeating cold rolling and annealing.

Among the mechanical grinding methods mentioned above, belt grinding, hub grinding, skull pink, etc. are easy to use industrially.

Next, the material for the shadow mask is mild steel.

Invar alloy (36Ni-Fe alloy, N1-pe-QO
There are various alloys such as Invar alloy, Ni −
The present invention is effective for Fe--Qo alloys because their etching rate is significantly lower than that of mild steel sheets, and they are particularly susceptible to uneven streaks.

Margin L Example of the invention] A 14-inch shadow mask having circular openings with a pitch of 0.38+u was manufactured as shown in Table 1, and it was observed whether or not uneven streaks occurred there. .

As is clear from this table, the shadow masks of the examples of the present invention have less uneven streaks and can be called good shadow masks.

[Effects of the Invention] As described above, the present invention can provide a good shadow mask with less uneven streaks because the surface layer is uniformly removed.

Claims (1)

[Claims] 1. A shadow mask in which a surface oxidation layer is uniformly removed. 2. Claim 1 in which the shadow mask is made of mild steel
Shadow mask as described in section. 3. The shadow mask according to claim 1, wherein the shadow mask is made of an iron-nickel alloy. 4. The shadow mask according to claim 1, wherein the shadow mask is made of an iron-nickel-cobalt alloy.