JP2001035404A - Shadow mask for color image receiving tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shadow mask for color image receiving tube involving a decreased deformation of the part around the center due to an impact, etc. SOLUTION: A mask plate 1 of a shadow mask is furnished with aperture 2 having a major diametric portion 2a at one of the surfaces and a minor diametric portion 2b at the other surface. The condition D1/D2<2.6 should be met at least in the central part of the mask plate 1, where D1 represents the diameter of the major portion 2a while D2 does the diameter of the minor portion 2b, and also the condition t/T>0.15 should be met at least in the central part of the mask plate 1, where (t) represents the height of the joining point of the two portions 2a and 2b while T does the thickness of the mask plate 1. Because the volume is increased even in the central part easy to make deformation, the part has a larger mechanical strength and deformation is not likely generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask for a color picture tube which is resistant to impact.

[0002]

2. Description of the Related Art Generally, a shadow mask of a cathode ray tube of a color picture tube has a large number of apertures, and these apertures are used to convert an electron beam emitted from an electron gun into a fluorescent light having a one-to-one geometric relationship. It has the function of passing light so that it only strikes the body layer, and is also called a color selection electrode. There are two types of shadow masks, round holes and rectangular holes, which can be roughly classified by their hole shape. Round shapes are used for display tubes for displaying characters and figures in detail, and are commonly used in households. Rectangular holes are generally used for pipes.

In recent years, the proportion of flat panel displays has been increasing as personal computer, office computer or EWS terminals, and there is a great demand for display tubes for desktop use.

[0004] On the other hand, general households tend to be large, and from the ergonomic point of view, a flat square having a flat screen with little reflection of external light and little image distortion.
Pipes are becoming mainstream. In recent years, the outer surface of a display panel on which a fluorescent screen for displaying an image is formed is a pure flat tube, which is a completely flat CRT similar to a glass plate, and is becoming the mainstream of the CRT. The shadow mask for a completely flat CRT has a greater curvature of the shadow mask after press molding than the shadow mask for a flat square tube, and the angle of incidence of the electron beam incident on the aperture around the shadow mask Is larger than a flat square tube.

As a result, in a completely flat tube, the rate at which a part of the incident electron beam collides with the hole edge or hole wall of the shadow mask is increased as compared with the flat square tube, and the shape of the electron beam is distorted. And reduce the brightness and white uniformity. Further, the reflected electron beam causes an unintended phosphor to emit light, causing a decrease in contrast and a decrease in color purity. These points are more likely to occur as the shadow mask aperture pitch is smaller and the thickness of the mask plate is larger. However, in the case of a cathode ray tube having a large incident angle of the electron beam to the aperture, such as a completely flat tube, this point is remarkable. And greatly lowers the quality as a color picture tube.

[0006] Further, in a completely flat tube, the tensile strength of the shadow mask is lower than that of a conventional flat tube having a small curvature, and the impact applied during the manufacturing process of the cathode ray tube, the transportation of the cathode ray tube, and incorporated in a television. The shadow mask is easily deformed by the impact, and the reliability of the quality of the cathode ray tube is weakened. If the shadow mask is extremely deformed, a color shift is completely generated in the portion.

[0007] As a shadow mask that obtains strength without lowering luminance and white uniformity, the configuration described in JP-A-10-144214 is known. That is, as shown in FIG. 2, the shadow mask described in Japanese Patent Application Laid-Open No. H10-144214 prevents deterioration of the mechanical strength of the shadow mask by eliminating unnecessary etching in the peripheral portion. is there.

[0008]

However, in the shadow mask for a completely flat tube having a large curvature in the horizontal H-axis direction, the shadow mask is press-formed because the shaping rate at the center of the shadow mask is small. Later, due to the impact during the manufacturing process of the CRT or the impact during transportation after the CRT is completed or after being incorporated into a set, there is a problem that deformation may occur near the center of the shadow mask. .

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a shadow mask for a color picture tube which reduces deformation near the center due to impact or the like.

[0010]

According to the present invention, a mask plate has an opening having a different opening size on one surface side and the other surface side. Assuming that the size is D2, at least the center of the mask plate is D1 / D
2 <2.6.

By setting the size of the opening as described above, at least the volume of the central portion is increased even in the central portion where deformation is likely to occur, the mechanical strength is increased in the central portion, and deformation is less likely to occur. .

Further, assuming that the height of the coincident point between the large hole side and the small hole side is t and the thickness of the mask plate is T, t / T> 0.15 at least at the center of the mask plate. And less likely to deform.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the shadow mask for a color picture tube according to the present invention will be described below with reference to the drawings. Parts corresponding to those in the conventional example shown in FIG.

As shown in FIG. 1, the shadow mask has a large hole portion 2a having a large hole diameter on one side of a mask plate 1 of the shadow mask, and a small hole side having a small hole diameter on the other side. An opening 2 having a small opening 2b and having a different opening size is formed.

The size of the large hole portion 2a of the opening 2 is D
1, when the size of the small hole portion 2b is D2, D1 / D2 <2.6 at least at the center of the mask plate 1, and the large hole portion
Assuming that the height of the coincident point between the hole 2a and the small hole portion 2b is t, and the thickness of the mask plate 1 is T, t is at least at the center of the mask plate 1.
/T>0.15.

Next, a method of manufacturing the shadow mask shown in FIG. 1 will be described.

First, iron having a desired thickness to be the mask plate 1 is used.
A high temperature degreasing solution of 80 ° C. or higher is sprayed on the low thermal expansion amber material of nickel to perform degreasing cleaning, and a resist film having a thickness of 7 μm to 8 μm is formed on both sides of the cleaned mask plate 1. Thereafter, a mask plate 1 on which a resist film is formed is positioned between shadow mask patterns for large and small holes which are attached to an exposure device (not shown). Irradiate the resist film through the pattern,
A latent image of a shadow mask pattern is formed on a resist film.

For the baking of the shadow mask, a model LZ-100, a large-size pattern making machine manufactured by Nippon Seiko, was used.
0 or model number LRS-1100 which is a large pattern making machine manufactured by Micronics. Further, when the shadow mask pattern for the large and small holes is printed on the front and back of the mask plate 1 on which the resist film is formed, if the alignment accuracy is low, the desired cross-sectional shape cannot be obtained. When the shadow mask pattern alignment position deviates from the design value, a function is provided for automatically correcting the shadow mask pattern to the design value.

Then, hot water of about 40 ° C. is sprayed on the resist film having the pattern latent image to dissolve and remove the unexposed resist film, and the surface of the mask plate 1 in which openings are formed by etching is exposed. Further, after the development is completed, a baking treatment is performed at a high temperature of about 200 ° C. in order to improve the strength, adhesion and etching resistance of the resist film, and a ferric chloride solution having a high temperature of 60 ° C. or more is sprayed and etched. As a result, a shadow mask having the target opening 2 is formed.

Further, in order to stably form the shape of the opening 2, the slit size of the shadow mask pattern printed on the small hole side at the center of the shadow mask is reduced,
When etching the mask plate 1 in a state where the small hole portion 2b is on the upper side and the large hole portion 2a is on the lower side while horizontally transporting the mask plate 1,
The etching may be performed under the condition that the flow rate of the etching solution sprayed from the small hole portion 2b to the large hole portion 2a is large in the central portion of the mask plate 1, or the impact force becomes strong.

Here, D at the center of the shadow mask
An experiment was conducted on deformation after pressing using a plurality of shadow masks having different values of 1 / D2 and t / T. As shown in Table 1, D1 / D2 <2.6 and t / T>
It can be seen that the deformation of 0.15 is small. Therefore, due to the impact during the production process of the cathode ray tube, the impact during transportation after the cathode ray tube is completed or after being incorporated into the set,
The deformation of the shadow mask is less likely to occur, and the tensile strength of the shadow mask after molding with a high-definition color CRT with a flat screen is increased.

[0022]

[Table 1]

[0023]

According to the present invention, by setting the size of the aperture in a predetermined range, the volume increases even in the central portion where the deformation is relatively likely to occur, so that the mechanical strength increases in the central portion and the deformation is increased. Is less likely to occur, and the mechanical strength can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a shadow mask for a color picture tube of the present invention.

FIG. 2 is a sectional view of a conventional shadow mask for a color picture tube.

[Explanation of symbols]

 1 Mask plate 2 Opening

Claims (2)

[Claims] An opening having a different opening size on one surface side and the other surface side of a mask plate, and the size of the opening on the large hole side is D.
1. A shadow mask for a color picture tube, wherein D1 / D2 <2.6 at least at the center of the mask plate, where the size of the small hole side is D2. 2. Assuming that the height of the point of coincidence between the large hole side and the small hole side is t and the thickness of the mask plate is T, t / T> 0.15 at least at the center of the mask plate. 2. A shadow mask for a color picture tube according to claim 1, wherein: