JPH0922664A - Shadow mask for color picture tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the mechanical strength of a shadow mask, and to realize the fine and accurate division. SOLUTION: A shadow mask 20 is formed by overlapping a phosphor surface side mask 24 at t1 of plate thickness, which is positioned in the phosphor surface side, and an electron gun side mask 26 at t2 of plate thickness, which is positioned in the electron gun side. Plate thickness of the electron gun side mask 26 is formed thin so as to be accurately and finely formed for regulation of the electron beam, and the plate thickness of the phosphor surface side mask 24 is formed thick so as to improve the strength of the whole of the mask. In consideration of hole diameter, which can be drilled, and the weight, t1 +t2 is set as 0.110-0.180mm, and in consideration of volume reduction at the time of etching with an increase of the plate thickness, a ration of plate thickness t1 /t2 is set as 2-5, and a ratio of the open hole diameter d1 /d2 is set at 1.4-1.8 so as to prevent the generation of distortion of the shape of a beam spot.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask incorporated in a color picture tube, and more particularly to a shadow mask formed by superposing two masks having different plate thicknesses.

[0002]

2. Description of the Related Art A shadow mask for a color picture tube has a large number of openings and is formed into a predetermined curved shape. The opening for passing the electron beam is formed by etching, and usually has a small hole on the side where the electron beam enters and a large hole on the side of the fluorescent screen through which the electron beam exits. Further, in the peripheral portion of the shadow mask, the incident angle of the electron beam, that is, the angle formed by the electron beam incident on the aperture with the mask normal in the vicinity of the passage hole is larger than that in the central portion near the tube axis, and the electron beam There is a possibility that the portion may hit the large hole on the phosphor screen side of the shadow mask and the spot shape of the electron beam reaching the phosphor screen may deteriorate. Therefore, Japanese Patent Publication No. 47-7670 proposes a so-called off-center mask in which the central axes of the large and small holes are shifted in order to increase the taper of the mask hole wall.

In general, the electron beam transmittance of the shadow mask is 15 to 20%, and most of the rest is projected onto the surface of the shadow mask and the temperature of the shadow mask is kept at 6%.
Raise to about 0 to 100 ° C. As a result, the shadow mask is thermally deformed, which causes deterioration in color purity called purity drift. A consumer color picture tube for a television receiver, in which the aperture pitch of the shadow mask is relatively rough, has a large margin for deviation in the geometrical positional relationship between the phosphor layer and the electron beam, and the shadow mask is not subject to thermal deformation. Even if it occurs, the degree of deterioration in color purity is small. However, a shadow mask used in a high-resolution color display or the like, in which the aperture pitch is set small, has a small margin for the deviation of the position of the electron beam impinging on the fluorescent screen, and the color purity is deteriorated due to thermal deformation of the shadow mask. Will also be noticeable.

In general, a high-purity rimmed steel or a low-carbon aluminum killed steel plate is used as a material for a shadow mask for a color picture tube in view of material supply capacity, cost, workability, strength and the like. Since such a shadow mask material has a large coefficient of thermal expansion and is likely to cause color purity deterioration, it is necessary to prevent the deterioration of color purity by using an iron-nickel alloy having a small coefficient of thermal expansion, for example, amber alloy.
Proposed in 446 etc. However, the material cost of the amber alloy is high, and the mechanical strength thereof is high, so that the yield in the step of forming the desired shape is poor, and the cost of the color picture tube increases.

On the other hand, there is also a method of using a thick shadow mask in order to suppress the deterioration of color purity by increasing the heat capacity of the shadow mask itself. However, when high resolution is required, such as in computer displays, it is necessary to reduce the diameter and pitch of the shadow mask apertures. It is desired that the shadow mask for a resolution color picture tube has a thinner plate than that for a consumer, etc., which has a low demand for higher resolution. As described above, the plate thickness of the shadow mask has a contradictory relationship with respect to thermal deformation and resolution.

Further, the radius of curvature of the shadow mask increases with the recent trend toward larger and flattened screens, and even if the shadow mask has the same plate thickness as the conventional one, the tension strength of the shadow mask after molding is low. Tends to become. As a result, there is a high possibility that the mask will be deformed due to an impact during the manufacturing process of the color picture tube or during transportation. Further, in the case of a shadow mask for a color picture tube in which the radius of curvature is increased to increase the screen flatness, the above-mentioned amount of offset must be larger than that of a shadow mask having a small radius of curvature.

As described above, from the viewpoint of heat capacity and mechanical strength, the plate thickness must be increased, but by increasing the plate thickness, the minimum aperture size that can be drilled becomes large, It is against the resolution. Furthermore, since the amount of offset is proportional to the increase in plate thickness of the shadow mask in addition to the incident angle of the electron beam, the distance between the large hole and the small hole on the side where the electron beam enters the center line of the aperture (mask center side). Becomes narrower and the distance becomes larger on the side where the electron beam escapes (outer side in the radial direction from the mask center), so that the mask aperture shape is deformed. Due to the deformation of the aperture shape, there is a problem that white uniformity (white uniformity) on the phosphor screen is deteriorated.

That is, as shown in FIG. 5, the taper a required for the electron beam 2 incident on the shadow mask 1 having the plate thickness T at an angle θ to escape to the phosphor screen side without hitting the aperture 3 is: When the height of the matching point 4 of the large and small holes is t, a =
It is represented by (T−t) × tan θ. That is, the taper a required becomes larger as the plate thickness or the incident angle increases.
As a general design, the aperture spacing is 0.27 mm and the aperture diameter is 0.
Table 1 shows changes in the taper a and changes in the shift amount (offset amount) of the central axes of the large and small holes when the mask plate thickness and the electron beam incident angle are changed for a 25 mm shadow mask.
Shown in

[0009]

[Table 1]

The problem of increasing the offset amount will be described with reference to FIG. Plate thickness 0.1 in Table 1
FIG. 6 is a schematic diagram showing a mask cross section at an incident angle of 35 degrees at 5 mm.
become that way. Since the taper a is 105 microns and the mask hole diameter is 125 microns, the sum of the two is 230 microns, which is almost the same as the large hole diameter. Since the height tc of the matching point of the large and small holes on the mask center side and the height tr of the matching point of the large and small holes on the outer side in the radial direction are significantly different, it is impossible to make the mask opening diameter the same as the small hole diameter. The aperture diameter must be increased to obtain the target aperture diameter, and an aperture diameter error is likely to occur. Further, since the heights up to the large and small hole matching portions are different accordingly, the spread speed of the opening due to etching is different between the mask center direction and the outer side in the radial direction, and ideally the solid line 6 should have the shape shown by the broken line 5. The shape of the hole is distorted as shown in. Therefore, when looking at the shadow mask as a whole, it is impossible to manufacture a mask having a uniform hole diameter due to variations in the spreading speed due to the etching of the holes located at the center of the mask and the holes located around the mask. Becomes Even when the mask plate thickness is increased, the offset amount increases accordingly, and the same drawbacks occur. In this way, if the aperture pitch and aperture diameter are reduced with a single plate to prevent the beam eclipse phenomenon, aperture deformation will occur.

[0011]

Therefore, in order to solve such a problem, it is desirable to use two shadow masks in a superposed manner.
It is proposed in Japanese Patent No. 67440.

However, the one disclosed in Japanese Patent Laid-Open No. 1-302639 has a double structure in terms of strength, and the above-mentioned off-center is not taken into consideration. In addition, since the reinforcing mask located on the phosphor screen side has a large plate thickness of 0.25 mm, it is necessary to increase the aperture diameter required to prevent the beam eclipse phenomenon. There is a risk that the holes will be connected, and the remaining volume after etching will be small, resulting in a loss of the reinforcing effect.

On the other hand, Japanese Unexamined Patent Publication No. 3-67440 discloses that a double structure shadow mask is used for off-centering, but the plate thickness and the like are not taken into consideration. Further, in this known example, in order to prevent beam chipping, it is necessary to make the taper of the opening large, and since the mask on the phosphor screen side must be etched more than necessary, the volume decreases drastically and mechanical There is a problem that the strength cannot be improved.

In view of the above-mentioned problems, the present invention has sufficient mechanical strength, can achieve high definition and can prevent the electron beam eclipse phenomenon, and has sufficient strength even after perforation by etching. The purpose of the present invention is to provide a structure of a shadow mask for practical use.

[0015]

In order to solve the above problems, the present invention provides a first mask having a large number of apertures through which an electron beam passes, which is on the phosphor screen side, and an opening of the first mask. A shadow mask for a color picture tube, comprising a large number of openings corresponding to the holes, and a second mask having a plate thickness and a hole diameter smaller than that of the first mask, which are superposed and adhered to each other. When the plate thickness of the second mask is t1 and t2, and the aperture diameters of the first and second masks are d1 and d2, respectively, 0.110 mm ≦ (t1 + t2) ≦ 0.180 mm 2 ≦ t1 / t2 ≦ 5 A shadow mask for a color picture tube, having a relationship of 1.4 ≦ d1 / d2 ≦ 1.8.

[0016]

According to the present invention, the total thickness of the double-structured shadow mask is regulated to prevent the unnecessary increase of the weight of the in-tube component while maintaining the necessary minimum strength. The first mask, which is the electron gun side mask, has a thin plate thickness because it is formed with high precision in order to regulate the electron beam.
The phosphor screen side mask 24 is thick in order to improve the strength of the entire mask. Considering the diameter of holes that can be pierced and the weight of parts in the pipe, t1 + t2 is 0.110 to 0.18.
The thickness is set to 0 mm, the plate thickness ratio t1 / t2 is set to 2 to 5 in consideration of the volume reduction at the time of etching due to the plate thickness increase, and the aperture diameter ratio d is set to prevent the beam spot shape distortion.
1 / d2 is set to 1.4 to 1.8.

In this way, by controlling the plate thickness ratio and the aperture ratio in the phosphor screen side mask and the electron gun side mask,
Minimize volume reduction due to etching to achieve high definition and mechanical strength.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 and 2 are views for explaining the configuration of the color picture tube. The overall structure of the color picture tube is the same as the conventional one, and has a panel 11 having a phosphor screen 10 formed on the inner surface thereof, and an envelope including a funnel 12 connected to the panel 11. The fluorescent surface 10 on the inner surface of the panel 11 is red, green,
An electron gun 15 composed of a plurality of phosphor layers each emitting blue light and emitting a plurality of electron beams 14B, 14G, 14R corresponding to the emission colors to the neck portion 13 of the funnel 12.
Is arranged. Further, inside the panel 11 between the electron gun 15 and the phosphor screen 10, the colors of the electron beams 14B, 14G, and 14R emitted from the electron gun 15 are color-selected and projected onto a phosphor layer of a predetermined emission color. A shadow mask structure 20 having a selection function is arranged via a holder 16. Further, a deflection yoke 17 provided on the outer wall of the funnel of the envelope horizontally and vertically scans to display a color image.

The shadow mask 20 has a substantially rectangular shape as shown in FIG. 2, and has a center O through which the tube axis Z passes and a large number of apertures 1.
8 provided with a perforated portion 21 and a non-perforated portion 22 around the perforated portion 21
have. The cross-sectional structure of the shadow mask according to the present invention is as shown in FIGS. 3 (a) and 3 (b).
FIG. 3A shows the central portion of the shadow mask, and FIG. 3B shows the peripheral portion of the shadow mask. As shown in FIG. 3, in the shadow mask 20, a fluorescent screen side mask located on the fluorescent screen side, 24 and an electron gun side mask 26 are superposed and securely fixed to necessary places by electron beam welding, laser welding, resistance welding or the like. It has a double structure that is integrated. As the shadow mask material, various materials such as a low carbon rimmed steel thin plate, a low carbon aluminum killed steel thin plate, an iron-nickel alloy which is a low thermal expansion material, and an amber material thin plate can be used.

The phosphor screen side mask 24 has a plate thickness t1 sufficient to maintain the strength as a shadow mask, and a large number of holes 25 for passing electron beams are formed by etching. If the opening diameter is large, the volume of the mask is greatly reduced during etching and the function of improving the mechanical strength is reduced. Therefore, the size of the opening 25 is set smaller than the size of the large hole of the conventional shadow mask having the same mask opening interval.

The electron gun side mask 26 defines the electron beam size, and a large number of holes 27 corresponding to the individual mask holes 25 are formed by etching to form small holes with high precision. Therefore, a plate material thinner than the fluorescent screen side mask 24 is used. Since the plate thickness t2 is thin, the cross-sectional shape of the opening of the electron gun side mask 26 is a through hole without a taper or a mortar-shaped opening with a slight taper.

Here, the plate thickness, aperture diameter, etc. of the double structure mask will be described in detail. In order to reduce the aperture size for high resolution, the plate thickness t2 of the electron gun mask 26 may be thinned, but in order to maintain the mechanical strength, the plate thickness T (= t1 + t2) of the entire double structure is set. It must be within a predetermined range. Therefore, if the electron gun side mask 26 is simply thinned, the plate thickness t2 of the phosphor screen side mask 24 is correspondingly reduced.
In order to achieve a sufficient amount of offset in the fluorescent screen side mask 24, the size d1 of the opening 25 of the fluorescent screen side mask 24 must be increased or the fluorescent screen side mask 24 itself must be turned off. Must be the center mask. When the aperture diameter d1 of the phosphor screen side mask 24 becomes large,
Compared to a mask with a small aperture diameter, the strength is weakened due to the volume reduction due to etching, while taking off-center with the phosphor screen side mask itself may cause the same problem as in the case of a conventional thick mask. . In other words, in order to achieve the desired characteristics while suppressing the volume reduction due to etching, it is necessary to set the plate thickness of the double structure mask to a predetermined relationship.

First, the electron gun side mask 26 of the double-structured mask can have a smaller aperture diameter d2 as the plate thickness t2 becomes thinner. The limit is 020 mm. It should be noted that this plate thickness is suitable for a hole pitch of 0.250 mm or less. Considering the strength of the shadow mask as a whole with respect to the electron gun side mask 26 having this thickness, the plate thickness t1 of the phosphor screen side mask 24 is 0.
About 090 mm is sufficient. If a sufficient amount of offset is taken between the electron gun side mask 26 and the fluorescent screen side mask 24, the required taper amount of the fluorescent screen side mask 24 can be small, and there is no problem of strength reduction due to etching. That is, the thickness T of the shadow mask as a whole is at least 0.110 mm. Considering the change of the mask plate thickness, the hole precision and the strength, with the relationship of the plate thickness as the minimum condition, it is as follows.

That is, it is preferable that the mask 24 has a large plate thickness in order to improve the strength. However, in consideration of practical use, the upper limit of the total thickness of the double structure mask is 0.180 mm.
If it becomes thicker than this, an increase in the weight of parts in the pipe cannot be ignored. Therefore, the total thickness T of the double structure shadow mask is
Is desired to be in the range of 0.110 mm to 0.180 mm.

The electron gun side mask 26 regulates the electron beam, and it is preferable that the plate thickness t2 is thin in order to form a high definition shadow mask. The thicker the plate thickness t2 is, the larger the minimum diameter of the openable hole is. However, as a shadow mask for a high-definition display tube, a plate thickness of about 0.060 mm can be applied without lowering the uneven quality.

On the other hand, the fluorescent screen side mask 26 serves to reinforce the strength of the entire mask, and the plate thickness t1 is preferably thick. However, if it is too thick, it is necessary to increase the etching amount in order to prevent beam spot shape deterioration (beam eclipse) due to beam impingement on the wall surface of the aperture. The effect of is reduced. On the other hand, if it is too thin, it does not serve as a reinforcement. From this, the plate thickness t of the phosphor screen side mask 24 is
A desirable value for 1 is 0.090 to 0.160 mm.

Further, as a matter of course, if the mask opening pitch is large, there is no problem in hole accuracy even if the plate thickness of the electron gun side mask is increased, and if the mask as a whole has a predetermined thickness. The plate thickness of the phosphor screen side mask may be reduced in proportion to the increase of the plate thickness of the electron gun side mask. On the other hand, if the plate thickness of the phosphor screen side mask is increased in order to improve the strength, the volume reduction due to the etching due to the provision of the large-diameter aperture increases as the thickness increases. Therefore, if the ratio of the fluorescent screen side mask and the electron gun side mask is set within a predetermined range,
It is possible to achieve strength improvement and high definition, and the ratio t1 / the plate thickness t1 of the phosphor screen side mask 24 and the electron gun side mask 26 is t1 /.
It is desired that t2 be 2 to 5.

The hole diameter d2 of the electron gun side mask 26 is determined by the design of the display tube. On the other hand, the phosphor screen side mask 2
If the hole diameter d1 of 4 is too large, the volume of the remaining portion after etching becomes small and the reinforcing effect becomes small. Therefore, the hole diameter d1 of the phosphor screen side mask 24 is preferably small. But,
If it is too small, there is a high possibility that beam eclipse will occur if an error occurs when aligning both masks, and in order to avoid this, the electron beam passes through the fluorescent screen side mask hole corresponding to the electron gun side mask. Since the offset is made on the side (outward in the radial direction), d1 is determined by also considering this offset amount, and d1 / d2 is 1.4 to 1.
If 8 is satisfied the purpose.

As a specific example, in the case of a shadow mask used in a flat square display tube having a 15-inch mask hole pitch of 0.27 mm, the mask hole diameter is as small as 125 μm, and the plate thicknesses of the first and second shadow masks are large. t1 and t2 are t1 = 0.10 mm and t2 =
At 0.03 mm, t1 / t2 is about 0.33.
Also, d1 = 0.175 mm and d2 = 0.125 mm.

The 17-inch mask hole pitch is 0.20.
In the case of the shadow mask used for the flat square display tube of mm, the mask hole diameter is as small as 85 microns, and the plate thickness t1 of the first and second shadow masks is 1.
t2 is t1 = 0.10 mm, t2 = 0.02 mm, respectively
Therefore, t1 / t2 = 5. Also, d1 = 0.1
50 mm and d2 = 0.085 mm.

Further, the 21-inch mask hole pitch is 0.3.
In the case of a shadow mask used for a 0 mm flat square display tube, the mask hole diameter is as large as 145 μm, and the plate thicknesses t1, t of the first and second shadow masks are large.
2 is t1 = 0.12 mm and t2 = 0.06 mm, respectively
Therefore, t1 / t2 = 2. Also, d1 = 0.2
30 mm and d2 = 0.145 mm.

The fluorescent screen side mask itself may be an off-center mask if necessary. The off-center mask can suppress the mask mass reduction. When trying to take offset with a conventional single mask, the aperture on the side of the electron gun side was regulated and the aperture on the fluorescent screen side was offset, so that the large and small hole matching parts on the mask center side and the peripheral side. This resulted in the displacement of the mask opening, resulting in the deformation of the mask opening. On the other hand, since the double-sided fluorescent screen side mask does not need to regulate the electron beam diameter,
The design margin is high. The offset amount Δ depends on the position of the hole in one mask, and the objective is satisfied if Δ = 0 to d2 / 2 is determined.

If the cross-sectional shape of the opening 25 is made into a mortar shape as shown in FIG. 3, the mask volume is greatly reduced during etching. Therefore, in order to maximize the remaining volume of the mask, the mask volume shown in FIG. As shown in (b), the cross-sectional shape of the phosphor screen side mask 24 may be a drum shape having a coincident etching point near the center of the plate thickness.

[0034]

As described above, according to the present invention,
By limiting the overall weight of the double structure mask and suppressing the increase in weight, the volume reduction due to etching can be minimized by setting the ratio of the plate thickness and aperture diameter of the two masks to a predetermined relationship. It is possible to improve. Therefore, it is possible to improve the mechanical strength of the shadow mask and achieve high definition.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a color picture tube.

FIG. 2 is a plan view of a shadow mask used in a color picture tube.

3A and 3B are cross-sectional views showing an embodiment of a shadow mask according to the present invention, where FIG. 3A shows a central portion of the shadow mask and FIG. 3B shows a peripheral portion of the shadow mask.

4A and 4B are cross-sectional views showing another embodiment of the shadow mask according to the present invention, wherein FIG. 4A shows a central portion of the shadow mask, and FIG. 4B shows a peripheral portion of the shadow mask.

FIG. 5 is a cross-sectional view showing a conventional shadow mask.

6A and 6B are views for explaining a defect of a conventional shadow mask, FIG. 6A is a sectional view, and FIG. 6B is a plan view showing an aperture shape.

[Explanation of symbols]

 24 ... 1st mask (fluorescent screen side mask) 25 ... 1st mask opening 26 ... 2nd mask (electron gun side mask) 27 ... 2nd mask opening t1 ... 1st mask plate Thickness t2 ... Plate thickness of second mask d1 ... Opening diameter of first mask d2 ... Opening diameter of second mask

Claims (1)

[Claims] 1. A first mask having a large number of apertures through which an electron beam passes and which is on the phosphor screen side, and a large number of apertures corresponding to the apertures of the first mask, and the plate thickness thereof. And a second mask having a hole diameter smaller than that of the first mask and being overlapped and fixed by adhesion, a plate thickness of each of the first and second masks is t1, t
2 and the opening diameters of the first and second masks are respectively d1,
A shadow mask for a color picture tube having a relationship of 0.110 mm ≦ (t1 + t2) ≦ 0.180 mm 2 ≦ t1 / t2 ≦ 5 1.4 ≦ d1 / d2 ≦ 1.8 when d2.