JPS6139344A - Shadow mask - Google Patents

Abstract

PURPOSE:To enable uniformity of form, pitch etc. of pores over a shadow mask for a color picture tube, by forming the shadow mask while regulating the coarseness of its surface by using mild steel etc. and forming pores by photoetching. CONSTITUTION:Over a plate material of a mild steel- or iron-nickel type alloy, or an iron-nickel-cobalt type alloy, buffing or acid cleansing is applied to regulate the surface coarseness within the center line means coarseness (Ra) 0.1- 0.4mum according to B0601, JIS, and the material is formed. Photoetching is applied thereon to prepare numerous circular pores, and a shadow mask for a color picture tube is made up. Thus, by regulating coarseness of the material surface within a specific coarseness, unevenness of form and pitch of pores caused by too much smooth surface is prevented, and a high accuracy and minuteness of the shadow mask can be secured.

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.

As this material, a thin mild steel plate having a thickness of about 0.15 II lil is usually employed. Recently, Invar alloy (Lnva alloy), which is an iron-nickel alloy with low thermal expansion characteristics, has been developed.
r) is beginning to be adopted.

These shadow masks are generally manufactured as follows.

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

Thereafter, the entire surface is pressed to form a curved surface with a predetermined curvature semi-longitudinal, and finally the entire surface is blackened by steam oxidation to improve thermal radiation and prevent diffused reflection.

However, the method of manufacturing a shadow mask using such a photoetching method has the following problems.

In other words, the shape of the holes to be drilled is subtly affected by the material, shape, etching conditions, etc. of the plate material, so it is extremely difficult to control the drilling of holes with high precision and high definition that is faithful to the design standards. In particular, when using Invar alloy, which has started to be used in recent years, the etching rate is significantly lower than that of mild steel sheets, and the shape of the holes themselves, the pitch between the holes, etc. There is a problem that it becomes uneven.

[Object of the Invention] An object of the present invention is to provide a shadow mask in which the shape of the openings themselves and the pitch between the holes are relatively uniform.

[Summary of the Invention J As a result of intensive research into shadow masks, the present inventors discovered that non-uniformity of openings is caused by surface roughness.

The present invention was completed based on this knowledge.

That is, the shadow mask of the present invention has JIS Boeoi
The center line average roughness (Ra) is 0.1 to 0.4μ,
Preferably, it is characterized by having a surface roughness in the range of 0.15 to 0.35 μm.

By defining the surface roughness in this way, non-uniformity in the shape and pitch of the openings can be reduced.

That is, if the surface is too smooth, the adhesion to the resist will decrease, and the resist will not adhere to the necessary areas;
If the surface is too rough, the etching rate will be slow for the convex portions, so that a portion of the aperture wall will remain unetched and the shape of the aperture will be non-uniform.

Therefore, considering these points, the center line average roughness (Ra) is 0.1 to 0.4uta, and even 0.15
~0.35μ set is preferable.

Materials for these shadow masks include, for example, mild steel,
There are Invar alloys, iron-nickel-cobalt alloys, etc.

Among these, Invar alloys and iron-nickel-cobalt alloys have particularly slow etching rates, and the shape of the openings is easily affected by surface roughness, making the present invention particularly useful.

Further, the present invention is more useful as the shadow mask becomes more precise and more precise. That is, the pitch of the openings is 0.38 to 0.7+u+
As the diameter increases from (medium precision II) to 0.2 mm (high precision), the pore shape becomes more susceptible to surface roughness and the present invention becomes more useful.

The above-described surface roughness can be obtained by applying, for example, puff polishing, pickling, shot blasting, dull rolling, etc. after rolling the material.

[Examples of the Invention] A 14-inch shadow mask having circular openings with a pitch of 0.38o+n+ was manufactured as shown in Table 1. As a result, the shape and uniformity of the pores formed were visually observed to see if they were uniform throughout, and the results are also listed in Table 1.

As is clear from this table, the surface roughness is 0.1 to 0.4μ
It can be seen that the regularity of the aperture shape and the uniformity of the entire shadow mask of the apertures can be obtained when the apertures are formed.

[Effects of the Invention] As described above, in the shadow mask of the present invention, by defining the surface roughness, the shape of the opening itself and the entire opening can be made relatively uniform.

Claims (1)

[Claims] 1. JIS B0601. A shadow mask having a center line average roughness (Ra) of 0.1 to 0.4 μm. 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.