JPH0864146A - Color picture-tube - Google Patents

Abstract

PURPOSE: To restrict the local thermal expansion by setting a difference between the outer diameter of a mask main body and the inner diameter of a mask frame in the long edge side of a shadow mask larger than the difference thereof in the short edge side of the shadow mask. CONSTITUTION: A shadow mask 24 of a color picture-tube is formed so that the outer diameters of the long edge side and the sort edge side of a mask main body 35 are formed smaller than the inner diameters of the long edge side and the short edge side of a mask frame 25 except for welding parts of the mask main body 35 and the mask frame 25. A difference Δsy between the outer diameter in the long edge side of the main body 35 and the inner diameter in the short edge side of the frame 25 is formed larger in average than a difference Δsx between the outer diameter in the short edge side of the main body 35 and the inner diameter in the short edge side of the frame 25. In the case where an image at a high luminance is locally displayed for a short time, even in the case where the main body 35 is expanded and the stress is generated in the main body 35, a large stress to be generated in the long edge side of the main body 35 can be restricted because the angle of deflection of the electron beam at a central part of the main body 35 is small and displacement of the beam landing is small, and because the peripheral part is welded to the frame 25 and thermal expansion of the main body 35 is restricted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask type color picture tube, and more particularly to a color picture tube in which deviation of beam landing due to thermal expansion of a shadow mask is suppressed.

[0002]

2. Description of the Related Art Generally, a shadow mask type color picture tube has an envelope having a substantially rectangular panel whose effective portion is a curved surface and a funnel-shaped funnel. A phosphor screen including a color phosphor layer is provided, and a shadow mask is arranged inside the phosphor screen so as to face the phosphor screen. With this shadow mask, the three electron beams emitted from the electron gun are selected so as to correctly land on the three-color phosphor layer.

In such a shadow mask, as shown in FIG. 4, a large number of slit-shaped or circular electron beam passage holes 1 are formed, and a peripheral portion of an effective surface 2 having a curved surface facing the phosphor screen is formed. A mask body 4 having a substantially rectangular shape provided with a skirt portion 3 and a mask frame 5 having a substantially rectangular shape arranged outside the skirt portion 3,
The skirt portion 3 and the mask frame 5 are welded at a plurality of points. And this shadow mask
The frame holder 6 made of an elastic body attached to the mask frame 5 is supported on the inside of the panel by engaging with a stud pin provided on the panel.

Generally, the electron beam that reaches the phosphor screen through the electron beam passage hole 1 of the shadow mask is 15 to 15% of the whole electron beam emitted from the electron gun.
It is about 25%, and most of the other electron beams hit the shadow mask and heat it.
For example, in a 20-inch color picture tube, if the anode voltage is 25 kV and the anode current is 1200 μA, the shadow mask is heated by the collision of the electron beam, and the shadow mask reaches about 70 ° C. in the central portion of the mask body. When heated in this way, the shadow mask thermally expands, the relative positional relationship with the phosphor screen changes, the beam landing on the three-color phosphor layer shifts, and in extreme cases, deterioration of color purity occurs. Raise it.

The thermal expansion of this shadow mask has the following two cases.

(A) When the color picture tube is operated for a relatively long time: In this case, the heat of the mask body heated by the collision of the electron beam is transferred to the mask frame, and the shadow mask as a whole reaches a thermal equilibrium state. In this case,
As indicated by the arrows 8 and 9 in (a) and the dashed line in (b), both the mask body 4 and the mask frame 5 thermally expand in the radial direction, and as a result, the shadow mask is It is displaced in the axial (z-axis) direction.

(B) When a high-intensity image is locally displayed for a relatively short time: In this case, as shown by an arrow 8 in FIG. 6A and a dashed line in FIG. Almost no thermal expansion occurs, only the mask body 4 thermally expands, and as a result, the mask body 4 is displaced more in the tube axis direction than in the radial direction.

Regarding the thermal expansion of (a) among these thermal expansions, in JP-B-44-8547, a bimetal element is interposed between a mask frame and a frame holder to increase the temperature of the shadow mask. A means for bringing the phosphor screen closer is shown. As shown in FIG. 6, by interposing this bimetal element 11, it is possible to effectively compensate the deviation of the beam landing with respect to the three-color phosphor layer. However, the deviation of the beam landing due to the thermal expansion of (b) cannot be compensated by the interposition of the bimetal element. Regarding the thermal expansion of (b), Japanese Patent Publication No. 50-68650,
It has been shown to form the mask body with a low thermal expansion material such as Amber alloy. That is, when the mask main body is made of a low thermal expansion material, it is possible to suppress local thermal expansion of the mask main body and reduce deviation of the beam landing due to the local thermal expansion.

However, this low thermal expansion material such as amber alloy is more expensive than a mask body made of a normal mild steel material, and it is difficult to form it into a predetermined curved surface.

[0010]

As described above, when the high-luminance image is locally displayed for a relatively short time as the thermal expansion of the shadow mask due to the collision of the electron beam, the mask frame hardly thermally expands. Only the mask body thermally expands, and as a result, the mask body is displaced more in the tube axis direction than in the radial direction. Such thermal expansion of the shadow mask can be suppressed by forming the mask main body with a low thermal expansion material such as amber alloy. However, the low thermal expansion material such as amber alloy has a problem that the cost is higher than that of the ordinary mild steel material of the mask body and that it is difficult to form it into a predetermined curved surface.

Therefore, even if the mask main body is formed of a high thermal expansion material such as mild steel, a means for suppressing the thermal expansion that occurs when a high-intensity image is locally displayed for a relatively short time is desired.

By the way, when a high-intensity image is locally displayed for a relatively short time, the displacement of the mask body made of mild steel due to thermal expansion is the largest at the middle portion of the mask body and becomes smaller as it approaches the peripheral portion. . This is because in the peripheral portion of the screen, the peripheral portion of the mask body is welded to the mask frame, so that the thermal expansion of the mask body is suppressed by the mask frame. On the other hand, in the central part of the screen, the deflection angle of the electron beam is small even if the central part of the mask body corresponding to the central part of the screen is thermally expanded,
The deviation of the beam landing with respect to the three-color phosphor layer is small. However, the deviation of the beam landing with respect to the three-color phosphor layer increases as it approaches the peripheral portion of the screen.
As can be seen from the figure, when a high-intensity image is locally displayed in a relatively short time, the deviation of the beam landing due to the thermal expansion of the mask body made of mild steel is mainly caused by the horizontal movement of the mask body 4 as shown in FIG. It occurs in the vicinity of the intermediate portion 13 on the axis (x axis).

Moreover, in the shadow mask, the distance from the center of the mask body 4 to the long side in the vertical axis (y-axis) direction is shorter than the distance to the short side in the horizontal axis (x-axis) direction. The heat of the heat is transmitted to the long side before the short side. On the other hand, the mask frame 5 has a larger heat capacity than the mask body 4 and a small amount of the electron beam directly impinging on it, so that the mask frame 5 does not thermally expand largely before the mask body 4. As a result, the mask body 4 is subjected to a larger stress in the vertical direction than in the horizontal direction, as shown by arrows 14 and 15 in FIG. The deviation of the beam landing occurs in the middle part of the screen corresponding to the vicinity 13 of the middle part, and the color purity deteriorates.

The present invention has been made in order to solve the problem of the shadow mask in which the mask body is made of mild steel. Even if the mask body is made of a high thermal expansion material such as mild steel, the local thermal expansion is caused. It is an object of the present invention to configure a color picture tube that can suppress the above phenomenon and that does not cause deterioration of color purity due to deviation of beam landing.

[0015]

A substantially rectangular shadow mask for selecting three electron beams landing on a three-color phosphor layer of a phosphor screen is provided, and this shadow mask is an effective surface facing the phosphor screen. A shadow mask for a color picture tube comprising a substantially rectangular mask body having a skirt portion provided on the peripheral portion and a substantially rectangular mask frame which is arranged outside the skirt portion and welded to the skirt at a plurality of locations. Was formed so that the difference between the outer diameter of the mask body on the long side and the inner diameter of the mask frame was larger than the difference between the outer diameter of the mask body on the shorter side and the inner diameter of the mask frame.

Further, the shadow mask is formed such that the difference between the outer diameter of the mask body on the long side and the inner diameter of the mask frame is maximized in the middle between the center of the long side of the mask body and the diagonal portion.

[0017]

As described above, in the shadow mask, the difference between the outer diameter of the mask body on the long side and the inner diameter of the mask frame is larger than the difference between the outer diameter of the mask body on the short side and the inner diameter of the mask frame. When formed, when a high-intensity image is locally displayed for a relatively short time, the stress generated in the mask body, especially the large stress generated on the long side of the mask body, can be reduced even if the mask body thermally expands. The deviation of the beam landing with respect to the three-color phosphor layer can be reduced to reduce the deterioration of color purity.

Further, when the shadow mask is formed so that the difference between the outer diameter of the mask body on the long side and the inner diameter of the mask frame is maximized in the middle between the center of the long side of the mask body and the diagonal portion, the same comparison is made. When a high-intensity image is displayed locally for a short time, even if the mask body thermally expands, it is possible to reduce the large stress particularly on the long side near the middle of the horizontal axis of the mask body. 3 at the position corresponding to the vicinity of the middle part
The deviation of the beam landing with respect to the color phosphor layer can be reduced to reduce the deterioration of color purity.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

FIG. 2 shows a color picture tube which is one of the embodiments. The color picture tube has an envelope composed of a substantially rectangular panel 20 having an effective portion having a curved surface and a funnel-shaped funnel 21 integrally joined to the panel 20, and the effective portion of the panel 20 is A phosphor screen 23 is provided on the inner surface of the phosphor screen 23. The phosphor screen 23 is composed of a striped three-color phosphor layer 22 that is vertically elongated and emits blue, green, and red light. A panel frame 20 is provided with a frame holder (not shown) made of an elastic material, which is attached to a mask frame 25 to be described later and has a substantially rectangular shadow mask 24 facing the phosphor screen 23. It is supported by being locked to a stud pin (not shown). On the other hand, in the neck 27 of the funnel 21, an electron gun 29 that emits the three electron beams 28 arranged in a row passing on the same horizontal plane.
Is provided. Then, the three electron beam 28 emitted from the electron gun 29 is deflected by a magnetic field generated by a deflecting device 30 mounted outside the funnel 21, and the phosphor screen 23 is horizontally and vertically scanned to obtain a color image. Is formed to display.

In the shadow mask 24, a large number of slit-shaped electron beam passage holes 33 are formed in a predetermined array on an effective surface 32 formed of a curved surface facing the phosphor screen 23, and the effective surface 32 is surrounded by a peripheral portion. It comprises a substantially rectangular mask body 35 provided with a skirt portion 34, and a mask frame 25 formed in an approximately rectangular shape having an L-shaped cross section and arranged outside the skirt portion 34 so as to surround the skirt portion 34. The mask body 35 and the mask frame 25
Are made of mild steel, and the skirt portion 34 and the mask frame 25 are fixed to each other by welding at the central portions and the diagonal portions of the long sides and the short sides.

Further, as shown in FIG. 1, the shadow mask 24 of the color picture tube of this example has the long side of the mask main body 35 except for the welded portion between the mask main body 35 and the mask frame 25 indicated by X. And the outer diameter of the short side is smaller than the inner diameter of the long side and the short side of the mask frame 25, respectively, and the outer diameter of the long side of the mask body 35 and the inner diameter of the long side of the mask frame 25. Difference .DELTA.sy is larger than the difference .DELTA.sx between the outer diameter of the mask body 35 on the shorter side and the inner diameter of the mask frame 25 on the shorter side on average.

In this way, if the difference Δsy between the outer diameter on the long side of the mask body 35 and the inner diameter on the long side of the mask frame 25 is formed to be larger on average than the difference Δsx on the short side, a relatively short time is required. When a high-intensity image is locally displayed, even if the mask body is thermally expanded and stress is generated in the mask body, it is possible to reduce a large stress particularly generated on the long side of the mask body. It is possible to reduce the deviation of the beam landing with respect to and reduce the deterioration of the color purity.

That is, in the conventional shadow mask, when a high-intensity image is locally displayed for a relatively short time, the mask body is locally subjected to a larger stress in the vertical direction than in the horizontal direction. Due to the thermal expansion, the beam landing is deviated in the middle part of the screen corresponding to the vicinity of the middle part of the horizontal axis, and the color purity is deteriorated. However, when the shadow mask is constructed as in this example, the mask body 35
Since the deflection angle of the electron beam is small in the central part of the mask, the deviation of the beam landing is small as in the conventional shadow mask, while the peripheral part of the mask body 35 is welded to the mask frame 25. The thermal expansion of 35 is suppressed, and the deviation of the beam landing is small like the conventional shadow mask. Further, even in the vicinity of the middle of the horizontal axis of the mask body 35 indicated by the broken line 37, the mask body 3
The difference Δsy between the outer diameter on the long side of 5 and the inner diameter on the long side of the mask frame 25 is made larger than the difference Δsx on the short side, so that even if the mask body 35 is thermally expanded, Is reduced, and the stress 38 that is greater than the horizontal direction that the mask body 35 receives in the vertical direction can be made as small as the stress 39 that receives in the horizontal direction. Even in the vicinity of the intermediate portion of the horizontal axis, the deviation of the beam landing can be reduced. By making it smaller, deterioration of color purity can be reduced.

In a color picture tube in which the electron beam passage hole of the shadow mask has a slit shape, if the difference between the outer diameter on the short side of the mask body and the inner diameter on the short side of the mask frame is large, vibration and impact characteristics are large. However, when the difference between the outer diameter on the long side of the mask body and the inner diameter on the long side of the mask frame is increased like the color picture tube of this example, the influence on vibration and impact characteristics is small, The beam landing deviation due to vibration or impact can be almost ignored.

Next, another embodiment will be described.

In the shadow mask shown in FIG. 3, the difference Δsy between the outer diameter on the long side of the mask body 35 and the inner diameter on the long side of the mask frame 25 is determined by the difference between the center and the center of the long side of the mask body 35. It is formed to have a maximum Δsxmax in the intermediate portion between and. Further, in this shadow mask, the outer diameter of the mask body 35 on the short side is substantially equal to the inner diameter of the mask frame 25 on the short side (Δsy = 0). Since the other structure is almost the same as that of the shadow mask of the above-mentioned embodiment, the same symbols are given to the same portions and the description thereof will be omitted.

When the shadow mask is constructed in this way,
By maximizing the difference Δsy between the outer diameter of the long side of the mask body 35 and the inner diameter of the long side of the mask frame 25 at the middle portion of the long side of the mask body 35, the height is locally increased for a relatively short time. When a brightness image is displayed, even if the mask body thermally expands, it is possible to reduce a large stress particularly generated on the long side of the horizontal axis middle portion 37 of the mask body. It is possible to reduce the deviation of the beam landing with respect to the three-color phosphor layer at the corresponding position and reduce the deterioration of the color purity.

As with the shadow mask of the above-mentioned embodiment, this shadow mask has a small effect on vibration and impact characteristics, and the effect of ignoring beam landing deviation due to vibration or impact can be obtained.

In the above embodiment, the color picture tube in which the electron beam passage hole of the shadow mask has a slit shape has been described, but the present invention is also applicable to the case where the electron beam passage hole is circular.

[0031]

According to the present invention, a shadow mask has a substantially rectangular mask body in which a skirt portion is provided in the peripheral portion of an effective surface facing a phosphor screen, and a mask body is arranged outside the skirt portion and welded to the skirt portion at a plurality of locations. In a color picture tube consisting of a substantially rectangular mask frame, the difference between the outer diameter of the mask body on the longer side of the shadow mask and the inner diameter of the mask frame is calculated by comparing the outer diameter of the mask body on the shorter side with the mask frame. If it is formed larger than the inner diameter of the mask, when a high-intensity image is locally displayed for a relatively short time, even if the mask body is thermally expanded, the stress generated in the mask body, particularly on the long side of the mask body, occurs. A large stress can be reduced, the deviation of the beam landing with respect to the three-color phosphor layer can be reduced, and the deterioration of color purity can be reduced.

When the shadow mask is formed so that the difference between the outer diameter of the mask body on the long side and the inner diameter of the mask frame is maximized in the middle between the center of the long side of the mask body and the diagonal portion, the shadow mask is relatively When a high-intensity image is displayed locally for a short time, even if the mask body thermally expands, it is possible to reduce the large stress particularly on the long side near the middle of the horizontal axis of the mask body. It is possible to reduce the deviation of the beam landing with respect to the three-color phosphor layer at a position corresponding to the vicinity of the portion and reduce the deterioration of the color purity.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a shadow mask of a color picture tube which is an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a color picture tube which is an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a shadow mask according to another embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a conventional shadow mask.

5A and 5B are diagrams for explaining thermal expansion of a conventional shadow mask when a color picture tube is operated for a relatively long time.

6A and 6B are diagrams for explaining thermal expansion of a conventional shadow mask when a high-intensity image is locally displayed for a relatively short time.

FIG. 7 is a diagram for explaining a cause of thermal expansion of a conventional shadow mask when a high-intensity image is locally displayed for a relatively short time.

[Explanation of symbols]

 20 ... Panel 22 ... Three-color phosphor layer 23 ... Phosphor screen 24 ... Shadow mask 25 ... Mask frame 28 ... 3 Electron beam 32 ... Effective surface 33 ... Electron beam passage hole 34 ... Skirt portion 35 ... Mask body

Claims (2)

[Claims] 1. A substantially rectangular shadow mask for selecting three electron beams for landing a three-color phosphor layer of a phosphor screen, the shadow mask being provided in a peripheral portion of an effective surface facing the phosphor screen. In a color picture tube comprising a substantially rectangular mask body provided with a skirt portion and a substantially rectangular mask frame arranged outside the skirt portion and welded to the skirt portion at a plurality of locations, the shadow mask is The difference between the outer diameter of the mask body on the long side and the inner diameter of the mask frame is formed to be larger than the difference between the outer diameter of the mask body on the short side and the inner diameter of the mask frame. A color picture tube. 2. A substantially rectangular shadow mask for selecting three electron beams for landing a three-color phosphor layer of a phosphor screen, the shadow mask being provided on a peripheral portion of an effective surface facing the phosphor screen. In a color picture tube comprising a substantially rectangular mask body provided with a skirt portion and a substantially rectangular mask frame arranged outside the skirt portion and welded to the skirt portion at a plurality of locations, the shadow mask is A color picture tube characterized in that the difference between the outer diameter of the mask body on the long side and the inner diameter of the mask frame is formed to be maximum between the center of the long side of the mask body and the diagonal portion. .