JPS6139343A - Shadow mask - Google Patents

Abstract

PURPOSE:To enable uniformity of form, pitch etc. of pores over a shadow mask, by making the shadow mask from mild steel etc. and forming it making the number of crystalline particles around a pore wall more than 50/mm., and forming pores by photoetching. CONSTITUTION:After a mild steel-, iron-nickel type alloy, or iron-nickel-cobalt type alloy is melted, then heat-treated, and, in the process of annealing and cool- rolling, given the final annealing temperature and time at 700-750 deg.C in about 0.5-2hr, and the final cool-rolling of 15-30% processing rate, the material is made up, whereon numerous circular pores are formed by photoetching, so as to make up a shadow mask for a color picture tube. Thus, number of crystalline particles around a pore wall is increased up to more than 50/mm., and unevenness of form and pitch of pores caused by crystalline particles can be avoided, gaining a high accuracy and minuteness of the shadow mask.

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 fluorescent surface, there is a shadow mask having a large number of apertures (dot-shaped, blind-shaped) formed based on predetermined design standards. It is arranged.

The material for this shadow mask usually has a thickness of about 0.
A 15m1 thin mild steel plate is used. Recently, Invar alloy, an iron-nickel alloy with low thermal expansion characteristics,
InVar) is beginning to be adopted.

This shadow mask is manufactured as follows.

First, a 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 radius of curvature, and finally the entire surface is blackened by steam oxidation to improve thermal radiation and prevent diffuse 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 basis. 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 and the distance between the holes There is a problem that the pitch etc. become non-uniform.

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

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

The present invention was completed based on this knowledge.

That is, the shadow mask of the present invention is characterized in that the number of crystal grains on the aperture walls is 50/111 or more, preferably 80/111 or more, more preferably 110/1111 or more.

That is, each crystal grain has a different direction of easy etching. As a result, since the etching rate differs depending on each crystal grain of the aperture wall, if the number of crystal grains is small, the influence of the easy direction becomes large, and the shape of the aperture wall tends to become distorted.

Therefore, by increasing the number of crystal grains, a shadow mask is provided in which the distortion of the shape of the openings is reduced.

The material for the shadow mask is mild steel, iron -42wt%
Nickel alloys (Invar alloys), iron-nickel-cobalt systems, etc. are conceivable, but since this order increases the non-uniformity of openings due to crystal grains, the present invention is effective in the reverse order.

Further, the distance between the openings of the shadow mask is not more than o, y+ns pitch, furthermore, not more than 0.38n+m pitch, and even more preferably not more than 0.2
The present invention is effective when the precision and definition are as high as m-pitch or less, since the non-uniformity due to crystal grains becomes particularly large.

The method for manufacturing the shadow mask of the present invention described above will be described below.

First, the material is melted and then hot processed.

Next, cold rolling and annealing are repeated several times, and finally annealing and cold rolling are performed to obtain a shadow mask material.

In this process, crystal grains can be made finer by combining the R* annealing conditions and the final cold rolling conditions as shown below.

That is, the final annealing concentration and annealing time may be selected within a range that does not cause the recrystallized grains to become coarse, for example, 1
It is preferable to perform annealing at 00 to 150° C. for about 2 hours.

In addition, for the final cold rolling process, a small working rate is preferable because it prevents the crystal grains from forming into fibers. On the other hand, if the working rate is too small, the effect of grain refinement due to cold rolling is lost. Hateful. Therefore, for example, a processing rate of 50% or less is preferable, and a processing rate of 15 to 30% is more preferable.

[Embodiments of the invention] Next, the actual ms of the present invention will be explained.

A 14-inch shadow mask having circular openings with a pitch of 0.38 m5 is manufactured using the materials shown in Table 1. As a result, the number of crystal grains that replaced the formed pores, the shape of the pores, and the pitch were measured and are listed in Table 1.As is clear from this table, it is clear that It can be seen that as the number of crystal grains increases, the non-uniformity of the pore shape and pitch decreases.

Further, the present invention was particularly effective for Invar alloy and Fe-Ni-Or gold alloy shadow masks.

Margins below [Effects of the Invention] As described above, the shadow mask of the present invention has a shape of the apertures themselves and a pitch between the apertures by increasing the number of crystal grains on the aperture walls to 50/mm or more. can be made relatively uniform.

Claims (1)

[Claims] 1. A shadow mask in which the number of crystal grains on the aperture wall is 50/mm or more. 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.