JPH0437537B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to a color picture tube, and particularly to the structure of a shadow mask. Technical Background and Problems of the Invention A conventional shadow mask type color picture tube consists of an envelope in which a panel 1 and a funnel 2 are joined together, as shown in FIG. , a shadow mask 4 is locked behind it via a support frame 5. An electron gun 6 is arranged at the neck portion of the funnel 2, and the electron beam 7 emitted from the electron gun 6 is deflected by a deflection yoke (not shown).
The light is deflected by the light beam, passes through the shadow mask 4, and reaches the fluorescent film 3. A large number of slit holes in the shadow mask 4 are arranged in the vertical axis direction with bridge portions in between, and the cross section of each slit hole in the mask plate thickness direction is such that the opening area is larger on the fluorescent surface side than on the electron gun side. It is being done. Usually, the phosphor screen side is the large hole side,
The electron gun side is also called the small hole side slit. As is well known, the shape of the slit hole in the shadow mask can be considered to be almost the same as the slit hole on the small hole side of the electron gun (hereinafter, the slit hole on the small hole side will be referred to as a slit hole).
Figure 2-1 shows an enlarged view of a normal slit hole.
The shape of the connecting part in the vertical axis direction of the slit hole 8, that is, the bridge part 9 in the short direction of the slit, is
The slit portions 8' in the longitudinal direction of the slits are straight and parallel to the slits 8' and 2-2.
The figure shows the positional relationship between the electron beam 11 that has reached the phosphor film and the phosphor film, and the light emitting area of the phosphor. The phosphor film 3 on the inner surface of the panel is formed by elongated strip-shaped phosphor strips G, B, R and black light absorbing strips 10 along the vertical axis. The three deflected electron beams 7 pass through the slit holes 8 of the shadow mask 4 and color the phosphor strips G, B, R, respectively. It is well known that the electron beam shape 11 is substantially the same as the slit hole 8. Normally, the positional relationship between the electron beam 11 that has reached the phosphor strips G, B, and R and the phosphor strips G, B, and R is determined by the distance from the panel inner surface 3 to the shadow mask 4,
The electron beam is directed in or out of the phosphor strips G, B, R. Figure 2-2 shows the electron beam 11
It can be seen that the effective light emitting area of each of the phosphor strips G, B, and R is different from each other. This is a cause of local color deviations due to deviations from the shape of the electron beams when the entire color picture tube screen is made white. This is called the white uniformity characteristic (hereinafter referred to as the WU characteristic).
In other words, it can be seen that the degree of surplus of the WU characteristic is decreasing. Also, when forming the black light absorbing strips 10 by coating, the roundness of the bridge portions 9 causes constrictions, which deteriorates the quality of the screen. As described above, with the usual slit hole shape, it was not possible to expect an increase in the margin of WU characteristics and an improvement in screen quality due to the constriction of the black light absorbing stripes. Next, a method for manufacturing such a shadow mask will be described. The shadow mask is made by using a negative master plate with large and small rectangular slits, and using photolithography, for example, the thickness of the plate is 0.15.
It is obtained by coating a photoresist film on a metal plate of 1.0 mm in diameter, printing the pair of negative master plates, developing, drying and burning, and finally etching with an etchant. The dimensional difference between the small slit in the negative master plate and the slit hole after corrosion is called the side etch amount, and the side etch amount relative to the thickness of the metal plate is shown in the table below.

[Table] Figure 3 shows the small slits in a normal negative original plate and the shape of the slit holes after corrosion. As shown in FIG. 3A, the rectangular negative original plate small slit 12 becomes a slit hole 13 as shown in FIG. 3B after corrosion, and the corner portions have a rounded shape. This is because there is a difference in corrosion rate between the slit portion in the longitudinal direction of the slit hole 13, the bridge portion in the lateral direction of the slit, and the corner portion of the slit hole. Since the slit portion has a large corroded area, the corrosive solution can be exchanged quickly and the corrosion rate increases. Since the bridge portion has a smaller corroded area than the slit portion, the exchange of corrosive liquid is slower, and the corrosion rate is slower. The corner portion becomes the boundary between the slit portion and the bridge portion, and the corrosion rate becomes even slower. The difference in corrosion rate between the slit portion and the bridge portion is also clear from the amount of side etching in the previous table. As described above, since the corrosion rate differs from one slit hole to another, it is practically extremely difficult to eliminate roundness at the corners of the slit hole by changing the conditions of the manufacturing method of the shadow mask. One possible solution to the above problem is to change the shape of the small slits in the negative master to accelerate the corrosion rate at the corners of the slit holes. For example, there is a method of attaching horns to the corners of the small slits in the negative original as shown in FIG. 4A, but this method is difficult in practice due to the following problems. For example, with a shadow mask, the plate thickness is 0.15
mm, to obtain a slit hole width of 0.170 mm, use the side etching amount of 0.075 mm in the previous table to make the negative original plate small slit width s.
is 0.095mm. When the horn width b of the small slit hole in the negative master plate is set to 1/4 of the small slit width s, the horn width b is approximately 0.024 mm, and since the horn width b is very thin compared to the small slit width s, the amount of side etching of the horn portion is The amount of side etching is approximately 0.045mm, which is smaller than the amount of side etching at the slit and bridge parts, and the corrosion rate is also slower. As a result, the shape of the slit hole is shown in FIG. 4B. In addition, in order to accelerate the corrosion rate at the corner of the slit hole, if the horn width b is increased, the horns of the bridge portion will match after corrosion, and the result will be the same as when the small slit length of the negative original plate was simply lengthened by the horn length a x 2. Become. Therefore, simply using a corner portion for a small slit in a negative original plate is insufficient to correct the roundness of the corner portion of the slit hole. OBJECTS OF THE INVENTION The present invention aims to increase the margin of WU characteristics and improve screen quality by forming the slit holes of a shadow mask so as to have a substantially rectangular shape. Summary of the Invention The present invention connects the slit holes on the small hole side of a shadow mask by a connecting groove having a long node in the vertical axis direction, and the bridge portion has an island-shaped portion branched by the connecting groove. This removes the roundness of the corners. Embodiments of the Invention The slit shape of a shadow mask applied to the present invention will be explained in detail below along with its manufacturing process. Figures 5A and 5B show the shape of small slits in the negative master plate on the small hole side of the shadow mask applied to the present invention. Small slit bridge part 1 of negative original plate
4 is provided with a pair of auxiliary dots 15 to form a negative original on the small hole side, and this negative original on the small hole side is combined with a negative original on the large hole side (not shown) which has no auxiliary dots and has a normal rectangular large slit. A shadow mask metal plate is sandwiched between these negative master plates on both sides, and etching is performed using a normal shadow mask manufacturing method. Said small slit supplementary dot 15
The positional relationship between the small slit 16 and the small slit 16 is related to the thickness of the metal plate (that is, the amount of side etching). For example, as shown in FIG. The auxiliary dot is placed inside the longitudinal extension line of the small slit. Furthermore, although FIG. 5B shows a case where the plate thickness is 0.18 mm, the supplementary dots 15 are placed outside the longitudinal extension line of the small slit. That is, the positional relationship between the supplementary dots 15 and the small slits 16 is determined by the amount of side etching. Regarding the shape and size of the auxiliary dots 15, the length (BL) and width (BS) of the auxiliary dots are determined by the amount of correction for the corrosion rate at the corner of the slit hole, regardless of the width of the small slit in the negative original. FIG. 6 shows the shape of the slit hole thus formed.
The slit holes on the small hole side are connected by two connecting grooves 18 that are long in the vertical axis direction and vertically connect the corners of the slit holes, and the connecting grooves 18 facilitate the exchange of corrosive fluid during corrosion, increasing the corrosion rate. The corner portions of the slit holes have the shapes shown in Line and Roux.
Furthermore, if it is desired to corrode the corner portion of the slit hole, this can be easily done by increasing the length (BL) of the auxiliary dot 15 and increasing the area of the connecting groove. As described above, on the small hole side of the shadow mask, the corner portions of the slit holes are connected by the connecting groove 18, and when looking at the slit holes that have just been connected, a node portion that locally protrudes wider than the slit hole is formed near the bridge portion. . The slit hole bridge portion 19 is located in an archipelago shape from the metal plate surface on the small hole side of the shadow mask by the two connecting grooves 18, that is, a slit hole shape on the small hole side is formed in which the connecting grooves are branched by the bridge portion. Ru. In addition, although the shape of the corrosion-promoting part has been described as a substantially triangular shape in the embodiment of the present invention, the purpose of the present invention is to remove the roundness of the corners of the slit hole, and the shape of the corrosion-promoting part may be substantially quadrangular, substantially trapezoidal, substantially polygonal, etc. I can't say enough good things about it. Effects of the Invention As described above, according to the present invention, corrosion is promoted by the connecting grooves of the slit holes in the shadow mask, and the roundness of the corners of the slit holes is removed, so that the slit hole shape becomes substantially rectangular, and the WU characteristics It is possible to provide a color picture tube with increased margin and improved screen quality.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of a normal shadow mask type color picture tube, Figure 2-1 is an enlarged view of the slit hole in the shadow mask used in the color picture tube shown in Figure 1, and Figure 2-2 is a phosphor film. Figures 3(a) and 3(b) are schematic diagrams for explaining the positional relationship between the arriving electron beam and the fluorescent film, and Figure 4(a) is a schematic enlarged diagram showing the small slits in a normal negative original plate and the shape of the slit holes after corrosion. , B are schematic enlarged views showing the conventional horn-shaped negative original plate small slit and the shape of the slit hole after corrosion, and Figures 5A and 5B are schematic enlarged views showing the negative original plate small slit shape applied to the present invention. , FIG. 6 is a schematic enlarged view showing the shape of the small hole side slit hole of the present invention. 1... Panel, 2... Funnel, 3... Fluorescent film, 4... Shadow mask, 5... Support frame, 6...
...Electron gun, 7...Electron beam, 8...Slit hole, 9...Bridge portion, 10...Black light absorption strip, 11...Electron beam reaching the fluorescent film, 12
...Small slit in negative original plate, 13...Slit hole after corrosion, 14...Small slit bridge part in negative original plate, 15...Small slit auxiliary dot in negative original plate, 16
...Negative original plate small slit, 17...Corrosion promotion part,
18... Connection groove, 19... Slit hole bridge portion.

Claims (1)

[Claims] 1. A color picture tube comprising at least a phosphor screen, an electron gun, and a shadow mask manufactured by etching so as to have a large number of slit holes arranged between them and connected via a bridge part in the vertical axis direction. The slit holes on the electron gun side of the shadow mask have a rectangular shape and are connected by a connecting groove having a long node in the vertical axis direction, and the bridge part has an island-like part branched by the connecting groove. A color picture tube comprising: