JPH03214547A - Shadow mask of color image receiving tube - Google Patents

Abstract

PURPOSE:To enhance the permeability of electron beam and provide a shadow mask with bright screen and high chromatic pureness by performing press shaping process, and then shaping the part outside the junction of the pored part of No.2 mask body with a small gap reserved relative to No.1 mask body. CONSTITUTION:A shadow mask 20 is mounted on a mask attraction device 31 and pinched with a mask holder 33 being in contact no No.2 mask body 22 side, and a strong mag. field is impressed on another mask attraction device 32 which is installed approx. 0.3mm apart from the No.2 mask body 22, which is thus attracted magnetically and shaped into the specified form, and a small gap 29 dimensioning between 0.05-0.5mm is formed at the surface where the mask bodies 21, 22 are contacting. Therein the welding line part 28 of mask bodies 21, 22 is welded in the direction of short axis of apertures 13a, 13b, so that the mask body 22 is free from twisting relative to the surface of the mask body 21. This allows providing a screen having good color pureness, and the permeability for electron beam is enhanced, so that a bright image will be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a shadow mask for a color picture tube,
Involved in improving the shadow mask, which is made by overlapping two K mask bodies.

[Conventional technology]

The shadow mask type color picture tube is constructed as shown in FIG. A funnel-shaped channel 1 and a front panel 2 are sealed together, and a fluorescent surface 3 coated on the inner surface of the panel 2, a plurality of pins 4 provided on the side wall of the panel 2, and a fluorescent surface 3 are formed. A shadow mask structure 5 is provided which is disposed opposite to each other and is supported by a spring plate 11 supported by the above-mentioned pin number via a bimetal 1o.

The shadow mask structure 5 is constructed as follows.

Electron beam 6A from electron guns 12A, 12B and 120
, 6B and 60 selectively pass through, and a non-porous area 24 formed around the periphery of the perforated area, and the inner surface shape of the panel 2 is similar to that of the panel 2. A shadow mask 7 having approximately equal spherical surfaces is provided. This shadow mask has a skirt 8 which is bent around four circumferences, and is welded and fixed to seven frames 9 at, for example, 8 to 16 points over the entire circumference of the skirt 8. This frame 9 is welded and supported by a bimetal 10 to compensate for thermal expansion of the shadow mask 7 that occurs during operation of the color picture tube. The spring plate 11 engaged with the pin 4 supports the bimetal 10 by welding and maintains the shadow mask at the relative position K of the panel 2.

In a force 21 picture tube with such a structure, the electron gun 12A
, 12B, 120 emitted from electron beams 6A, 6B
, 60 pass through the aperture 13 consisting of a large number of array holes provided in the perforated region 23 of the shadow mask 7, and strike the phosphors emitting red, green, and blue light on the phosphor surface 3. to emit light. Usually, for the surface area of the shadow mask 70,
The total area of the apertures 13 is approximately 15 to 25%, and most of the electron beams collide with the non-opening portions and heat the shadow mask 7.

For example, as a result of measuring the temperature of the shadow mask structure 5 using a 21-inch color picture tube, the temperature rise curve shown in FIG. 10 was obtained. In other words, Takadaden E 28kV, beam current 1m
Under the condition A, the temperature at the center of the shadow mask 7 is
As shown by temperature curve 14, the temperature rose significantly in the first 5 minutes and reached saturation at about 40° C. in 30 minutes. However, the temperature of the frame 9, which has a large heat capacity, rose slowly and reached a saturated state in about 1 hour K1, as shown by a temperature rise curve 15.

Due to such a difference in temperature rise, the shadow mask 7 thermally expands and protrudes in the direction of the fluorescent surface 3, causing color shift. That is, as shown in FIGS. 11 and 12, the shadow mask 7, which was in the state shown by the solid line before the start of the operation, is displaced to the state shown by the dotted line (position '70) due to thermal expansion due to the temperature rise. Therefore, the electron beams 6k, 6B, and 60 that have passed through the aperture 13 move toward the center by a distance T shown in Figure 11 on the phosphor surface s, causing adjacent phosphors of other colors to emit light. It becomes impossible to reproduce normal color graphics.

This is a 21 type (21 inch) panel 2 whose inner radius is 13
When measured with a 50 mm color picture tube, the electron beam appeared most prominently on the long axis 150 mm from the center of the 7-ace plane of panel 2, and at a high voltage voltage of 28 kV and a beam current of 1 mA, the electron beam was 0.05~0. A color shift phenomenon occurs due to OBmm movement.

On the other hand, when the temperature of the frame 9 gradually rises by 1 and approaches a saturated state, the frame 9 undergoes an expansion due to thermal expansion to a position 9A shown by a dashed line in FIG. 11. Therefore, frame 9
The 7th surface of the Shadoku V-sk that is joined to moves to the state of position 7A. As a result, the electron beam 6 passing through the aperture
A, 6B, 6C! moves outward by a distance S, causing the phosphor to emit light in the opposite direction to the phenomenon that occurs at the beginning of the operation of the color picture tube, making it impossible to reproduce a normal color image.

This phenomenon continues to occur if the color picture tube is operated continuously, and it is necessary to correct it.

Therefore, the bimetal 10 (
9), the frame 9 is moved to the position 9 shown in FIG. 11 so that the shadow mask 7 approaches the panel 2.
BK is displaced, the shadow mask 7 surface is moved to a position 7B indicated by a two-dot chain line, and the amount of color shift is corrected so that the beam trajectory matches the regular fluorescent surface.

However, in the screen K where the local brightness increases,
It has been impossible to correct the color shift due to thermal deformation of the shadow mask 7 facing the local area, since it is hardly expected that the temperature of the bimetal 10 will increase.

To solve these problems, it is effective to increase the thickness of the shadow mask, as shown in the paper ``Theoretical Study on Local Doming Phenomenon K of Shadow Mask Tubes'' published in the Journal of the Television Society of Japan. This has been theoretically proven. However, shadow masks are generally manufactured using a chemical method, such as the etching method disclosed in Japanese Patent Publication No. 51-9264.

In manufacturing using this method, there is a relationship between the plate thickness t and the width dimension Sw of the shadow mask hole through which the electron beam passes, as shown in the following equation, and a small hole is drilled in the thick plate a! It was impossible to create an OSv＞○. On the other hand, improving the resolution of CRTs (cathode ray tubes) and reducing the size of the fluorescent surface means that the shadow mask holes become smaller, and in order to maintain color purity due to thermal deformation of the shadow mask. There is a contradictory relationship in that a thick shadow mask is required. Therefore, as mentioned above, it is difficult to make the shadow mask hole small, so for example, as shown in Japanese Unexamined Patent Publication No. 57-138746, a large number of through slots are provided across a bridge. A method was considered in which two thin shadow masks were stacked and welded together.

[Problem to be solved by the invention]

The shadow mask of the conventional color picture tube as shown above is
Each mask body that is assembled by stacking two sheets is usually 0.3 mm.
It is manufactured from aluminum killed steel with the following plate thickness, and has many through holes in the hole width direction via bridges, so if the mask body is made thicker, the bridges will become wider, which will prevent the electron beam from passing through. There was a problem in that the rate increased, and this became a major obstacle to improving the brightness of the fluorescent surface.

In addition, in order to set the positional relationship of the apertures of each overlapping mask body so as not to obstruct the passage of the electron beam, when press forming into the desired shape, it is necessary to There is a problem in that it is difficult to obtain passage of a predetermined amount of electron beam due to variations in the deviation.

The present invention was made to solve these problems, and aims to provide a shadow mask for a color picture tube that has high electron beam transmittance, a bright screen, and high color purity.

[Steps to solve problems]

In the shadow mask for a color picture tube according to the present invention, of the first and second mask bodies, the second mask body on the opposite panel side is made extremely thin so that the difference in the length of the neutral line is small. This prevents the displacement of both 7-patchers during press molding, and after press molding, the part of the second mask body outside the joint of the perforated part is moved to the first mask body by electromagnetic force or the like. It is molded with a small gap between the two.

[Effect]

In this invention, the electron beam emitted from the electron gun passes through the seven holes of the shadow mask.
Since most of the light hits the second mask body, the temperature of the second mask body, which is extremely thin, rapidly rises by 1. but,
The electron beam hardly hits the first mask body on the panel side that controls the position of the electron beam, and heat transfer from the second mask body on the opposite panel side is mostly due to radiation transfer, so the mask body is overlapped. By making the emissivity of the corresponding surfaces of both mask bodies smaller than that of the other surfaces, the temperature rise of the first mask body can be made extremely small, thereby suppressing thermal deformation.

In addition, since the second mask body has a linear joining point with respect to the first mask body K, even if a gap is provided between the surfaces of the first mask body and the first mask body, A bright screen can be obtained without twisting, reflecting electron beams in unnecessary directions, reducing color purity, or blocking the passage of electron beams.

〔Example〕

FIG. 1 is a plan view of a shadow mask of a color picture tube according to an embodiment of the present invention before it is bent.

The shadow mask 20 is formed by overlapping a first mask body 21 and a second mask body 22. The first mask body 21 facing the fluorescent surface 3 is made of, for example, an aluminum killed steel plate and has a thickness of 0.15 to 0.30 mm, and controls the position where the electron beam impinges on the fluorescent surface 3. It is for the purpose of The second mask body 22, which is overlapped and bonded to the first mask body 21 and is mechanically reinforced, is made of, for example, an aluminum killed steel plate, has an extremely thin plate thickness of 0.01 to 0.05 mm, and absorbs most of the electron beam. will collide. Reference numeral 23 indicates a perforated region having an aperture (not shown) consisting of a large number of arranged holes, 24 indicates a non-porous region having a peripheral area having no aperture, and 25 indicates a first mask body 21 and a second mask. body 22
This is a positioning hole for determining the relative position of. 28a indicates a number of planned welding line positions to be welded in a later process.

FIG. 2 is a vertical cross-sectional view showing the state of the shadow mask in the state shown in FIG. 1 after being bent and completed. The small gap formed in the outer portion prevents heat transfer from the second mask body 22, whose temperature has increased, to the first mask body 21.

Next, the production of a shadow mask according to an embodiment of the present invention will be explained using a 21-inch color picture tube as an example.

First, the dimensions of the mask body 21 and 22 in which the perforated region and the non-porous region 24 are formed by chemical etching are as follows, as shown in a partially enlarged view in FIG. There is. The mask body 21 has a plate thickness t 1 =0. At 25mm,
Bitch P of apertures 13a and 13b = 0.65m
m, the narrowest part on the electron gun side @W=○. 15m
m, each dimension from this center line Q is W1 = 0.
160mm, W2 = 0.120mm. In addition, the mask body 22 has a plate thickness t2 = 0.025 mm.
So, W3=0.180mm, W4=O. 150mm
It has become. (In the figure, the mask body 22 has a gap t3
However, it is formed at the end of the manufacturing process, and is flat in the early stages of the process. ) The mask bodies 21 and 22 manufactured in this way are formed by inserting the positioning holes 25 provided as shown in FIG. 1 into the positioning jig 27 shown in FIG.
is inserted into the positioning bin 26 of , and both are aligned.

Next, for example, as shown in FIG. 4, the head 30 is lowered. As shown in FIG. 6, the aperture 13a,
The mask bodies 21 and 22 are welded from the bridge 34 in the long axis direction of the mask body 13b to the aperture adjacent in the short axis direction at the welding line part 2 by laser light emitted from the head 3o. At this time, a strong magnetic device is installed in the direction of the jig 27 in contact with the mask body 21, and the magnetic force causes the mask body 21. 22 may be welded while being in close contact with each other. (
Note that although FIG. 6 shows a state in which a small gap 29 is formed in the mask body 22, this is formed in the final process. )
Thereafter, press molding is performed using a mold having a curved surface of a predetermined shape to obtain a shadow mask 20 of a predetermined shape.

Next, a blackening process is performed to generate a deteriorating film with high emissivity on the surface of the shadow mask 20. At this time, mask body 2
Since the contact surfaces 21a and 22b of 1.22 are not sufficiently supplied with oxygen, a blackened film with high emissivity is not generated.

Subsequently, as shown in FIG. 5, the shadow mask 2Q is attached to the mask suction device 31, and the mask presser 33 is brought into contact with the second mask body 22 side to hold the shadow mask 20, and the shadow mask 20 is held approximately from the mask body 22. A strong magnetic field is applied to the mask suction device 32 installed at a distance of 0.3 mm, and the mask body 22 is magnetically attracted to the mask body 22 into a predetermined shape.
．． A small gap 29 is formed between the contacting surfaces of 22. At this time, the mask body 21. As shown in FIG. 6, the weld line portion 28 of the mask body 22 is welded in the short axis direction of the apertures 13a, 13b, so that the mask body 22 will not twist with respect to the surface of the mask body 21. The small gap 29 is 0.0
5 to 0.5 mm is appropriate. FIG. 8 shows a sectional view taken along the line Y--Y in FIG. 6.

Note that if the thickness of the second mask body 22 on the opposite panel side exceeds 0.05 mm, its thermal deformation stress will affect the first mask body 21, increasing the amount of mislanding. . In addition, if the plate thickness is as thin as 0.01 mm, the amount of deformation due to handling during the crushing process is large and the plate cannot be used for general purpose.

〔Effect of the invention〕

As described above, according to the present invention, the first mask body on the inner surface side of the panel and the second mask body on the opposite side of the panel, which are welded at a large number of welding lines, are press-formed between both mask bodies. Since a small gap is provided outside the weld line, the temperature of the second mask body that is hit by the electron beam rises rapidly, but the second mask body is thin and heat radiation from the inner surface Because the rate is bad,
The amount of heat transferred to the first mask body is small, the temperature increase is suppressed to a small level, thermal deformation of the first mask body is reduced, and a decrease in color purity of the screen can be prevented.

In addition, the strain caused by the difference in the amount of elongation between the first and second mask bodies due to the temperature difference is released by the deformation of the second mask, which is very thin, and is exerted on the first mask body. The impact will be minimal.

This creates a screen with good color purity and increases the transmittance of the electron beam, making it possible to obtain bright images.

[Brief Description of the Drawings] Fig. 1 is a plan view showing a state before bending and forming of a shadow mask of a color picture tube according to an embodiment of the present invention, and Fig. 2 is a press bending of the shadow mask in the state shown in Fig. 1. Fig. 3 is a longitudinal cross-sectional view of the completed state with a gap formed between both mask bodies after molding, and Fig. 3 shows the state in which the first and second mask bodies of the shadow mask shown in Fig. A perspective view, FIG. 4 is a cross-sectional view of both mask bodies in FIG. 3 being electron beam welded, and FIG. 5 is a welding of both mask bodies that have been welded together and press bent in the process of FIG. 4. FIG. 6 is a cross-sectional view of a main part showing a means for forming a gap in a portion outside the line, and FIG. Figures 7 and 8 are the 6th
9 is a partially cutaway perspective view of a conventional shadow mask type color picture tube,
FIG. 10 is a curve diagram showing the temperature rise with respect to operating time of the picture tube frame and shadow mask in FIG. 9; FIG. 11 is an explanatory diagram of the deformation state due to temperature change of the shadow mask structure of the picture tube in FIG. 9; FIG. 12 is an explanatory diagram showing the shift of the electron beam toward the fluorescent surface due to thermal deformation of the shadow mask shown in FIG. 11. 2... Panel, 3... Fluorescent surface, Work 3... Aperture 13a, 13b... Aperture 20... Shadow mask, 21... First mask body, 22... Third 2
mask body, 23... perforated area, 24... non-perforated area, 28... weld line part, 29... small gap. Note that the same reference numerals in the drawings indicate the same or equivalent parts.

Claims (1)

[Claims] a first mask body made of a thin plate material with a thickness of about 0.15 to 0.30 mm, in which an aperture is formed, and arranged to face the fluorescent surface on the inner surface of the panel of the picture tube; 0.
The first mask body is made of a thin plate material of 0.05 mm and has an aperture formed therein, and includes a second mask body that is overlapped with the first mask body on the opposite side of the panel and joined by a number of weld lines, and the two mask bodies are combined. A shadow mask for a color picture tube, characterized in that a small gap is formed between the surfaces outside the welded joint.