JPH0471296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a cathode ray tube, and more particularly to a shadow mask for a color cathode ray tube.

[Technical background and problems of the invention]

Generally, color cathode ray tubes are as shown in Figure 1.
An envelope is composed of a rectangular panel 1, a funnel-shaped funnel 2, and a net 3, and a screen 4 having striped phosphors that emit red, green, and blue light is provided on the inner surface of the panel 1. There is. On the other hand, in the net 3, so-called in-line electron guns 6 are provided which are arranged in a line along the horizontal axis of the panel 1 and emit three electron beams corresponding to red, green, and blue. Between the screen 4 and the electron gun 6, there is a shadow mask 5, which is made up of a mask body with a large number of slits facing the screen and a frame 7 fixed by welding to the mask body. It is provided through. In such a color cathode ray tube, the three inline electron beams are deflected by a deflection device (not shown) external to the funnel 2 so as to scan the inner surface of the substantially rectangular panel 1. The colors are sorted through the slit holes in the shadow mask 5, and the striped phosphors are correctly struck to cause them to emit light, thereby producing a color image. Of the electron beams emitted from this electron gun, the effective electron beam that passes through the slit hole of the shadow mask 5 is usually less than 1/3, and the remaining electron beam impinges on the shadow mask 5 and sometimes damages the shadow mask 5. It will be heated to about 80℃. By the way, the mask body of this shadow mask 5 is generally formed of a thin plate with a thickness of 0.1 mm to 0.3 mm mainly composed of iron, which has a relatively large thermal expansion.
Strong blackened frame 7 with a thickness of around 1mm
The periphery is fixed by. In the early stages of operation of a color cathode ray tube, the mask body is heated by the impact of electron beams. At this time, since the peripheral part of the mask body is blackened and close to the frame 7 having a large heat capacity, heat is transferred to the frame 7 by radiation and conduction, and the temperature of the peripheral part of the mask body becomes lower than that of the central part. As a result, a temperature difference occurs between the central part and the peripheral part of the mask body, and it becomes as if only the central part is relatively heated, causing this central part to heat and expand, resulting in so-called doming. As a result, the distance between the screen and the mask body is changed,
There is a drawback that the electron beam passing through the slit does not accurately strike a predetermined striped phosphor, resulting in deterioration of color purity.

[Purpose of the invention]

The present invention has been made in view of the above points, and an object of the present invention is to reduce doming of a shadow mask during the operation of a color cathode ray tube, and to prevent deterioration of color purity due to color shift of an image.

[Summary of the invention]

The present invention provides a cathode ray tube equipped with a shadow mask consisting of a mask body having a large number of through holes adjacent to the inner surface of the panel, and a frame that is fixed to the peripheral portion of the mask body and supports the mask body. By providing a heat reflective layer on at least one surface of the mutually opposing parts, heat from the mask body is prevented from moving to the frame by radiation conduction, thereby suppressing doming in the initial operating state of the shadow mask. It is a cathode ray tube.

[Embodiments of the invention]

The present invention will be explained in detail based on examples.

The color cathode ray tube according to the present invention comprises an envelope consisting of a panel 1, a funnel 2 and a net 3 as shown in FIG. The configuration with the electron gun 6 is the same as that shown in FIG. 1, and the shadow mask is characterized in that it is configured as follows. That is, as shown in FIG.
5a, the bent portion or skirt portion 18
The mask body 15 is welded to the skirt portion 18 at multiple locations, and the mask body 15
It consists of a frame 17 that supports the. This frame 17 has a substantially L-shaped cross section, and the mask body 15
A heat reflective layer 20 is provided on the inner surface 17a and the outer surface 17b facing the peripheral portion 15a including the skirt portion.
This heat reflective layer 20 is a nickel plating layer with a thickness of 10 μm to 20 μm, and is formed by degreasing and cleaning a frame made from a material into a frame shape as a whole with an L-shaped cross section, and then passing it through a plating bath. Thereafter, it is welded and fixed to the skirt portion 18 of the mask body at multiple locations.

When operating such a color cathode ray tube,
The shadow mask is heated by the impact of the electron beam, but since a heat reflective layer is provided on the surface of the frame, which has a large heat capacity, heat radiation from the periphery of the mask body to the frame is reduced, and the heat radiation from the periphery of the mask body to the frame is reduced. The transfer of heat from the area to the surrounding area and frame is impeded. In addition, the heat absorbed by the frame is difficult to radiate from the frame because the emissivity of the frame is low, and the temperature of the frame itself is also difficult to decrease.
This also makes it difficult for the temperature around the mask body, which is attached to the frame, to drop. As a result, the temperature difference between the central part and the peripheral part of the mask body is relatively reduced, and the amount of doming of the shadow mask can be reduced. Experiments using a color cathode ray tube according to the present invention showed that the amount of movement of the electron beam due to doming of the shadow mask was 15% to 20% compared to a conventional color cathode ray tube using a frame that was only blackened.
%Diminished. In addition, since the nickel plating layer is formed relatively thick at 10 μm to 20 μm, it is difficult to rust, so there is no need for any special anti-rust treatment, such as the process of forming a blackening film. Even when heated to high temperatures of around 400° to 500° during baking, sealing, or exhausting processes, it maintains its glossy surface and acts as a heat-reflecting layer. This is the thickness
When it becomes thinner than about 10μm, the rust prevention effect disappears,
When heated to the high temperatures mentioned above, it loses its luster and no longer functions as a heat reflector. In addition, if the diameter exceeds 20 μm, it is disadvantageous in terms of cost, and if the diameter exceeds 20 μm,
A preferable range is about 20 μm.

The heat reflective layer may be plated with aluminum on the frame in the same manner as described above. In that case, the thickness is preferably 2 μm to 4 μm; within this range, the luster and rust prevention effect will not be lost, and the thickness will be better than that of nickel. It has the same effect as plating.

In the embodiment shown in FIG. 2, the skirt portion 18 of the mask is welded and fixed to the outside of the frame 17, but as shown in FIG.
The skirt portion 18 may be welded to a. In the example shown in FIG. 3, a heat reflective layer 20 made of an aluminum plating layer with a thickness of approximately 2 μm is formed on the inner surface 17a of the frame 17 facing the peripheral portion 15a of the mask body 15. In this case as well, heat radiation from the mask peripheral portion 15a to the frame 17 is reduced, the temperature difference between the center and the periphery of the mask body is reduced, and the amount of doming of the shadow mask can be suppressed.

FIG. 4 shows yet another embodiment, in which a heat reflective layer 20 made of an A-Zn plating layer is formed to cover the entire surface of the frame 17. In this case, the emissivity is lower over the entire surface of the frame, so it is more difficult for heat to radiate and the temperature of the frame itself is less likely to drop than when a heat reflective layer is provided only on the surface facing the periphery of the mask. , the temperature around the mask also becomes difficult to decrease. As a result, the temperature difference between the periphery and the center of the mask becomes smaller. Here, A-Zn plating was used as the heat reflective layer,
If the thickness is 20 μm or more, it has rust prevention properties and can sufficiently maintain its function as a heat reflective layer even when heated at high temperatures.

Furthermore, FIG. 5 shows another embodiment, in which the entire surface of the frame 17 is covered with a heat reflective layer 20 plated with nickel, and a heat reflective layer 20a is formed on the peripheral part 15a including the skirt part 18 of the mask body. . The heat reflective layer 20a of the mask is obtained by metal spraying A on a blackened mask body in the atmosphere,
The effect of the heat reflective layer will be sufficiently exhibited if the thickness of the coating by thermal spraying is about 2 μm to 4 μm. In this case, the emissivity of the peripheral portion of the mask body is also lowered, which has the advantage of further suppressing the temperature drop in this portion, and in addition to A, Ni or an alloy thereof may also be used.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to reduce mask doming in the initial stage of operation of a cathode ray tube and improve color purity deterioration such as color shift.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view schematically showing a color cathode ray tube;
2 to 5 are schematic cross-sectional views of shadow masks showing embodiments of the present invention. 15...Mask body, 7,17...Frame,
20, 20a...Heat reflective layer.

Claims (1)

[Scope of Claims] 1. A cathode ray tube comprising a shadow mask consisting of a mask body having a large number of through holes adjacent to the inner surface of the panel, and a frame fixed to the periphery of the mask body and supporting the mask body. A cathode ray tube characterized by having a heat reflective layer on at least one surface of the opposing portions of the main body and frame. 2. The cathode ray tube according to claim 1, wherein the heat reflective layer is formed to cover the entire surface of the frame. 3 A heat reflective layer is formed on the frame and its thickness is
The cathode ray tube according to claim 1 or 2, characterized in that the cathode ray tube is made of nickel with a diameter of 10 μm or more. 4 A heat reflective layer is formed on the frame and its thickness is
The cathode ray tube according to claim 1 or 2, characterized in that the cathode ray tube is made of aluminum with a diameter of 2 μm or more. 5 A heat reflective layer is formed on the frame and its thickness is
Claim 1 or 2, characterized in that it is an aluminum-zinc alloy with a diameter of 20 μm or more.
Cathode ray tube as described in section. 6. The cathode ray tube according to claim 1, wherein the heat reflective layer is formed on the mask body and is an aluminum layer having a thickness of 2 to 4 μm.