JP2780245B2 - Shadow mask for color picture tube and method of manufacturing the same - Google Patents

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 and a method of manufacturing the same.

[0002]

2. Description of the Related Art It has been known that in a shadow mask type color picture tube, the temperature of the shadow mask rises due to the impact of an electron beam, causing thermal deformation. Since this thermal deformation causes a color shift generally called a misregister, it is desired to take measures for each cause. One of the thermal deformations is called local doming. This is because during operation of the color picture tube, only a part of the image reproduction screen (generally a relatively large part having a size of a fraction to several tenths of the total effective surface area) is compared with other parts. This is a phenomenon in which, when an image that is extremely bright and almost still remains for a long time, a shadow mask corresponding to the bright portion locally undergoes thermal deformation.

FIG. 4 shows the relationship between an image reproduced on the screen of a color picture tube and local doming of a shadow mask. In FIG. 4 , reference numeral 1 denotes a panel having a fluorescent screen formed on the inner surface, and 2 denotes an iron plate. With a shadow mask made of a metal plate,
It has a number of small holes 3 for transmitting electron beams. Since the holding mechanism of the shadow mask 2, the electron gun, and the like are well-known, their description is omitted. On the other hand, in the image shown in FIG. 1, reference numeral 100 denotes an image portion that is significantly brighter than other portions, for example, a white cloud in a blue sky, and such a state is slightly longer (5 seconds or more) and almost stationary. If it continues, the portion of the shadow mask 2 corresponding to the image 100 has a greater amount of electron beam bombardment than the other portions, so that the temperature locally rises and the dotted line 101
Is deformed as shown by the solid line 102. For this reason, the small holes 3 in the shadow mask 2 cannot be kept at the fixed positions.
The electron beam that has passed through the laser beam causes the irradiation point on the phosphor dot to move (misregister), causing a color shift. This deformation occurs in a general shadow mask in a direction in which a shadow mask portion corresponding to a bright screen swells toward the phosphor screen side. This phenomenon is conspicuous rapidly as the deflection angle increases, and as in recent years, a wide angle such as 110 ° deflection,
This is a very serious problem in a color picture tube having a flat screen.

Various methods have been devised as a method of reducing such a local doming phenomenon. As a typical example, there is known a method in which the shadow mask 2 conventionally made of a material almost similar to pure iron is made of an alloy called Invar having a small coefficient of thermal expansion. Invar is an alloy with about 36% nickel and the balance iron.

As another method of reducing the doming phenomenon, as disclosed in Japanese Patent Publication No. 61-6969, for example, when an electron beam strikes the shadow mask 2, the mask temperature is prevented from rising. A method of applying a substance that reflects electrons to the surface is known. A typical example is a method in which an oxide of a heavy metal such as lead or bismuth is applied to the electron beam incident side of the shadow mask 2. This is based on the fact that a substance having a large atomic weight has a strong property of reflecting electrons. Oxide is used because the single metal is unstable to heating in the air, or it is difficult to dissolve and keep it in place. Is difficult to exert.

The invar alloy described above as a countermeasure against doming has a thermal expansion coefficient of about 1/9 that of conventional iron, and even if the shadow mask 2 is locally heated by electron beam bombardment, the amount of expansion in that part is increased. Is small, the doming amount is small, and the doming amount in the case of the conventional iron can be reduced to about 30 by setting the doming amount in the case of iron to 100. Here, the reason why the doming amount does not become as small as the ratio of the expansion coefficient as compared with the case of the conventional iron is that the thermal conductivity of this material is about 1/5 of that of iron, and therefore, the impact of the electron beam This is because the amount of heat that is transmitted through the material and escapes is small, and the temperature of the electron beam projection is higher than that of iron.

In addition, as a countermeasure against doming, the above-described method of applying an electron-reflecting material is because most of the electron beam striking the shadow mask 2 is repelled by the applied material with considerable energy. Thus, the temperature rise of the projecting portion can be suppressed. For example, when an appropriate amount of the above-described lead oxide or bismuth oxide is applied onto the shadow mask 2 made of iron, the doming of the shadow mask 2 made of iron, which is not applied, is reduced to about 70, with the doming of the iron-made shadow mask 2 being 100. be able to.

[0008]

The above-described method using an invar alloy as a countermeasure against doming requires a high material cost because a large amount of expensive nickel is used, and a hole is formed by etching for processing as a shadow mask 2. However, there is a drawback in that forming by a press or press is difficult, and processing cost and yield are poor, resulting in a significant increase in cost. Moreover, when this was performed, the effect of reducing local doming as expected from the coefficient of thermal expansion was not obtained.

In addition, the method of applying an electron reflecting material to the shadow mask 2 cannot exert its effect sufficiently, and has a problem in manufacturing such that the electron beam transmitting hole 3 is clogged by this material. Eventually, the cost increases.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the problems of the prior art, and it is possible to suppress the doming phenomenon caused by the impact of an electron beam, and to manufacture a shadow mask for a color picture tube which is inexpensive and easy to manufacture. It is intended to provide a way.

[0011]

SUMMARY OF THE INVENTION A shadow mask for a color picture tube according to the present invention has a small number of small electron beam transmitting masks.
It is composed of a metal plate with holes and has a phosphor screen.
A shadow mask body disposed opposite the inside of the flannel,
Having a small hole for transmitting an electron beam, and
The electronic mask of the shadow mask body has a smaller area than the mask body.
Spot facing the beam incident surface side
At the welding point of the shadow mask body
A metal auxiliary mask is provided.
It is located almost in the center of the mask and
At locations other than the welding points, the auxiliary mask is
It is characterized in that it does not adhere to the mask body
To do

Further, in the method of manufacturing a shadow mask for a color picture tube according to the present invention, after the shadow mask main body is press-molded, an auxiliary mask is melted in the shadow mask main body.
They are joined by contact points , and then blackened.

[0013]

According to the present invention, the auxiliary mask receives at least a part of the electron beam supposed to hit the shadow mask main body and raises the temperature. The heat due to this temperature rise is transmitted to the shadow mask body by radiant heat, but since heat radiation is performed from both sides of the auxiliary mask, the heat incident on the shadow mask main body portion facing the auxiliary mask is compared with the case without the auxiliary mask. Become smaller. Auxiliary mask and shadow mask
Close to the disk body at places other than spot-shaped welding points
Heat conduction between the two is negligible
It is only about.

An auxiliary mask is provided on the shadow mask body.
By performing a blackening process after joining at a welding point, a shadow mask that is less likely to cause local doming can be easily obtained.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an example of a shadow mask for a color picture tube according to the present invention.

In FIG. 1, reference numeral 12 denotes a shadow mask main body which is disposed to face the inner surface of the panel 1, and has a large number of regularly arranged small electron beam transmitting small masks. A hole 3 is provided. These small holes 3 are usually flat thin metal plates (shadow mask original plates)
Thereafter, the metal plate is press-formed to form the shadow mask body 12. Reference numeral 4 denotes a frame which is attached to the periphery of the shadow mask main body 12 in order to maintain the shape of the shadow mask main body 12 as a whole and to hold the same at a predetermined position on the inner surface of the panel. It is formed from a metal plate. The shadow mask main body 12 and the frame 4 are usually joined and fixed by welding. A mechanism such as a spring for holding the frame 4 at a predetermined position on the inner surface of the panel is attached to the frame 4, but the description and illustration are omitted here.

Reference numeral 22 denotes an auxiliary mask. The auxiliary mask 22 is made of the same thin metal plate as the shadow mask main body 12, and is similar to the electron beam transmitting small holes 3 (only a part of which is shown in the figure) of the shadow mask main body 12, and is slightly smaller than this. A large hole 13 for transmitting a large electron beam (only a part thereof is shown in the figure) is provided on the entire surface so as not to obstruct the electron beam passing through the small hole 3. The area of the auxiliary mask 22 is considerably smaller than the area of the portion of the shadow mask main body 12 where the small holes 3 are provided (the area of the portion corresponding to the size of the screen of the color picture tube), and substantially. A plurality of, for example, six, are independently fixed in spots on the inner surface of the shadow mask body 12 by welding points 14.

The size of the auxiliary mask 22 is, for example, 10 when the size of the color picture tube is 25 inches.
It is approximately 0 × 100 mm ² and is welded by a laser or the like so as not to overlap with a portion relatively close to the periphery of the shadow mask main body 12, that is, a portion where the electron beam with a large deflection angle is incident. At this time, the welding point 14 is located at a position relatively near the center of the auxiliary mask 22,
There are only three locations, and at other locations, the shadow mask main body 12 and the auxiliary mask 22 are in normal contact with each other, and are not in a state of so-called close contact or adhesion.

As shown in FIG. 2, the electron beam transmission hole 3 is provided on the panel 1 to prevent unnecessary scattering of the electron beam.
Has a cross-sectional shape that expands toward the fluorescent screen side. In a normal state of the electron beam, the small hole 13 on the auxiliary mask 22 side is formed to have a larger diameter than the small hole 3 so that the electron beam is substantially regulated by the small hole 3 on the shadow mask main body 12 side. Considering the direction of incidence of the electron beam, it is superimposed so as to be slightly shifted as required. Further, the welding point 14 is formed in the non-hole portion 12a of the shadow mask main body 12.
And the non-hole portion 22 a of the auxiliary mask 22. Further, since the non-holes 12a and 22a are considerably narrow,
In order to completely join the auxiliary mask 22 to the shadow mask main body 12, it is desirable to provide a plurality of welding points 14 per small piece of the auxiliary mask 22. The welding point 14 is desirably provided near the approximate center of each auxiliary mask 22.

Next, the operation of the above-described embodiment will be described. In general, the local doming described above is performed when the deflection angle of the electron beam as a color picture tube is relatively large,
In other words, a problem occurs relatively near the periphery of the shadow mask body 12. However, when the electron beam locally collides with a relatively peripheral portion of the shadow mask main body 12, if the auxiliary mask 22 is arranged, most of the electron beam in this portion which should collide with the shadow mask 12 is formed. Auxiliary mask 22
To raise the temperature of this part. This allows
The auxiliary mask 22 generates heat radiation, which appears on both sides of the auxiliary mask 22. Of these, some of the light generated from the portion of the auxiliary mask 22 facing the shadow mask main body 12 is absorbed by the shadow mask main body 12, increasing the temperature of this portion. However, approximately one half of the heat radiation emitted from the auxiliary mask 22 is directed to a portion that does not face the shadow mask main body 12, that is, toward the tube wall of the color picture tube, where it is absorbed and transmitted to the shadow mask main body 12. Does not enter. Since the auxiliary mask 22 and the shadow mask main body 12 are not in perfect contact with each other except for the spot-shaped welding points 14, the heat conduction is extremely poor. Therefore, the heat conduction of the heat of the auxiliary mask 22 to the shadow mask main body 12 can be almost ignored. . As a result, the heat absorbed by the shadow mask body 12 is reduced to about 1/2, and the doming is reduced accordingly.

By the way, up to now, the shadow mask body 1
The electron beam that has directly hit the target 2 is now the auxiliary mask 2
Thus, the auxiliary mask 22 is thermally deformed. However, this is different from the local doming phenomenon described above for the following reasons, and does not cause harm in a practical sense.

First, as described above, in the local doming as described above, the portion of the shadow mask main body 12 where the electron beam is projected expands locally, whereas the entire peripheral portion expands. In this case, the electron beam projecting portion swells up. In order for local doming to occur so conspicuously that it is harmful in practical use, it is necessary that the area of projection of the electron beam be larger than a certain area (for example, 2500 mm in a shadow mask having a plate thickness of 0.25 mm). ² or more). However, since the individual area of the auxiliary mask 22 is not so large, even if the electron beam collides with one of the areas having an area where local doming would have been a problem in the past, In most cases, at least a part thereof protrudes from one auxiliary mask 22. That is, a state that "the entire area around the portion expanded by the impact of the electron beam does not expand does not expand, so the electron beam projecting portion expands" is difficult to appear.

The second reason is that the auxiliary mask 2
2. Even if the doming phenomenon occurs, the shadow mask body 1
As long as the electron beam 2 is not deformed, the electron beam passing through the small hole 3 of the shadow mask body 12 may be partially missing,
It does not hit where it should not hit on the phosphor screen. That is, the location of the problem on the phosphor screen is usually simply darkened, and does not exhibit a very unfavorable phenomenon such as emission of other colors.

Although there is the second reason described above, it is desired that the auxiliary mask 22 itself does not easily cause doming. Therefore, it is not preferable to make the size of one auxiliary mask 22 too large for the first reason, and it is desirable to perform welding with the shadow mask main body 12 with as small an area as possible and with a small number of points.
Further, the effect of thermal deformation of doming of the auxiliary mask 22 associated with the second reason is minimized by the welding point 14.
Is desirably located near the center of each auxiliary mask 22. In addition, if the size of the auxiliary mask 22 is too large, there is a problem in holding in terms of welding strength.
It becomes difficult to form the small holes 3 and the small holes 13 with high accuracy over the entire auxiliary mask 22. Conversely, if the auxiliary mask 22 is too small, the number increases, the number of mounting steps increases, and the number of operations for matching the small holes 3 and 13 also increases. Accordingly, the size of the auxiliary mask 22 varies depending on the curved surface, curvature, and the like of the shadow mask main body 12, but when the shape is close to a circle or a square, when the plate thickness of the shadow mask main body 12 is approximately t, 4 × 10 ⁴ t ² to 4 × 10 ⁵ t ² is appropriate.

In the embodiment shown in FIG. 1, there is a gap between a plurality of auxiliary masks 22 mounted thereon, and the electron beam incident thereon is not directly interrupted by the auxiliary masks 22 but directly to the shadow mask body 12. Local doming requires some electron beam projecting area for it to harm, and small gaps are not a problem.

The thermal emissivity of the surface of the shadow mask body 12 on the side facing the auxiliary mask 22 is set to 1
2,2 than 22,22 not overlapped
It is good to set small in the part where 2 overlaps.
This is because it is desired that the heat transfer by radiation is as small as possible in the overlapping portion of the shadow mask main body 12 and the auxiliary mask 22, while the shadow mask main body 12 is
This is because it is desirable that the heat generated by the electron beam bombardment escapes as much as possible from the portions not overlapping with each other.

The thermal emissivity of the auxiliary mask 22 on the side facing the shadow mask main body 12 is preferably set to be smaller than the surface on the opposite side on which the electron beam is incident. The reason is that most of the heat generated in the auxiliary mask 22 due to the impact of the electron beam can be released to the electron beam incident surface side of the auxiliary mask 22. As a result, local doming of the shadow mask main body 12 can be significantly reduced as compared with a state where the auxiliary mask 22 is simply attached.

[0028] described in FIG. 3 method for manufacturing a shadow mask for setting the thermal emissivity, as described above. In FIG. 3 , the manufacturing of the shadow mask includes a press forming step 41 for producing the shadow mask main body 12 having the small holes 3 from the original shadow mask plate, and a welding step 42 for joining the auxiliary mask 22 to the shadow mask main body 12. , A blackening step 43.

Here, the blackening process is a process which is also performed in a conventional shadow mask, and is performed by performing a heat treatment in an oxidizing atmosphere for the purpose of improving the heat radiation characteristics of the surface. This is a step of forming a black oxide film on the surface. In this embodiment, the auxiliary mask 22 is welded between the press forming step 41 of the metal plate to be the shadow mask main body 12 and the blackening step 43.
In this way, an oxidizing atmosphere for blackening will almost stationary in between shadow horses disk body 12 and the auxiliary mask 22, this is the face instead placed constantly atmosphere having an oxidizing power, since it is less to be supplied Only a very imperfect oxide film is formed on the surface where the two 12 and 22 are opposed to each other. As a result, the two 12 and 22 can be formed without any special work.
Can have a smaller heat emissivity on the opposite surface than on the opposite surface.

The auxiliary mask 22 is press-molded and welded to the shadow mask main body 12. However, the auxiliary mask 22 does not need to be bent in particular, but if the individual area is small, the auxiliary mask 22 can be formed along the shadow mask main body 12. This is because the appropriate hole positions can be overlapped only by bending, and a proper gap between the two 12 and 22 that is not completely adhered can be naturally provided. Of course, the auxiliary mask 22 may be separately formed in advance. In short, after welding, both 12,22
When press molding is performed integrally, almost complete adhesion is obtained, and the effect of the present invention is lost.

The present invention may have various other modifications. For example, the auxiliary mask 22 is made of an iron alloy having a low coefficient of thermal expansion containing 36 to 42% of nickel with respect to the shadow mask body 12 which is usually made of iron, so that thermal deformation similar to doming of the auxiliary mask 22 is reduced as much as possible. It is also possible.

The auxiliary mask 22 is made of a material in which blackening (oxide film) is unlikely to be formed under the conditions for blackening an ordinary iron material such as an alloy containing nickel. It may be blackened.

[0033]

As is evident from the foregoing description, according to the inventions, the electron beam incident surface side partially face of the shadow mask body
Place multiple auxiliary masks approximately in the center of each auxiliary mask.
Weld each to the main body of the shower mask, and at locations other than the welding point
Each auxiliary mask is not in close contact with the shadow mass body
As a result, it is possible to easily manufacture and provide a color picture tube capable of sufficiently suppressing local doming without increasing the cost.

Further, according to the inventions, after the molding of the shadow mask, the auxiliary mask welding. Thus straining facilities blackened after its may readily be exhibited local doming prevention effect by the auxiliary mask color A method for manufacturing a shadow mask for a picture tube can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a shadow mask for a color picture tube according to the present invention.

FIG. 2 is an enlarged sectional view of the shadow mask.

FIG. 3 is a view showing a manufacturing process of the shadow mask for a color picture tube according to the present invention.

FIG. 4 is an explanatory view of a conventional shadow mask for a color picture tube.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Panel 3 13 Electron beam 12 Shadow mask main body 14 Weld point 22 Auxiliary mask 41 Press forming process 42 Auxiliary mask attaching process 43 Blackening process

Claims (2)

(57) [Claims] 1. A shadow mask main body which is formed of a metal plate having a large number of small holes for transmitting an electron beam and which is disposed to face an inner surface of a panel on which a fluorescent screen is formed, and a small mask for transmitting an electron beam. It has a hole, and a smaller area than the shadow mask body is arranged partially facing the electron beam incident surface side of the shadow mask body, in spot-like welding points
A plurality of metal auxiliary masks to be joined to the shadow mask main body , wherein the welding points are approximately the same as those of the auxiliary masks.
Center position and the above welding points
Outside, the auxiliary mask is the shadow mask body
A shadow mask for a color picture tube, wherein the shadow mask is made so as not to adhere to the mask. A press molding process wherein molding the shadow mask body, the steps you joining auxiliary mask by welding points to the shaped shadow mask body, after attaching the auxiliary mask in the shadow mask body is blackened And a method of manufacturing a shadow mask for a color picture tube.