JPH03192635A - Color picture tube - Google Patents

Abstract

PURPOSE:To improve doming characteristic by gradually increasing the slot to slot pitch and the slot width of a shadow mask from its center to the circumference and increasing the mask thickness from the center to the circumference. CONSTITUTION:The pitch between slots 2 and the slot width of a shadow mask 1 are made larger from its center toward its circumference. An area is provided on the circumference of the mask where its thickness is thicker than that in the center. The slot pitch Pc in the shadow mask center is determined by the screen size and the target resolution of a color picture tube. Then the slot width Swc of the shadow mask is determined by the width of a beam passing through the slot and according to how the landing allowance is taken. Since the doming size is inverse proportion to the shadow mask thickness, the mask thickness is made greater on the circumference than in the center of the mask for reducing the doming. This improves doming characteristic in the circumferential area of the mask.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color picture tube having a striped phosphor screen, and in particular to improvement of a shadow mask for preventing color shift that occurs at high current.

[Conventional technology]

4 and 5 show a plan view and a sectional view of a shadow mask used in a conventional color picture tube having a striped phosphor screen. It's a slot. Line C-C is the center of mask 1, P is the lateral pitch of the slots at the center of the mask, P is the lateral pitch of the slots at the periphery of the mask, S wc is the slot width at the center of the mask, and S we is This is the slot width around the mask.

As mentioned above, the pitch between slots is generally PC<P.

Designed to close. One of the reasons for this is that the influence of the earth's magnetic field is greater in the periphery, especially in some corners, than in the center of the mask, so it is necessary to increase the landing margin. As shown in the cross-sectional view of the mask, the curved radius R of the mask 1 along the panel 3,
This is to make it smaller. The smaller R, the smaller the doming (the amount of movement of the electron beam on the phosphor screen due to thermal expansion of the mask as the electron beam enters the mask).

One of the design conditions for a shadow mask is the target resolution. This determines the required pitch of the shadow mask. Whether this required pitch is satisfied on the entire west side or only in the center depends on the application, but for color image receiving CRTs, it is often satisfied only in the center. . Once the pitch is determined, the slot width S is created in the shadow mask. C is also determined by design. Generally speaking Sw
It is e2Pc/4. On the other hand, in order to reduce the above-mentioned doming, it is effective to increase the thickness t of the shadow master. However, the minimum slot width S wc that can be opened is determined by the plate thickness t. Generally speaking, the wide range of slot widths that can be opened economically is SWC≧Tt.

[Problem to be solved by the invention]

Since the shadow mask of a conventional color picture tube is constructed as described above, in the shadow master, the usable mask thickness is determined at the same time as the slot pitch PC is determined, and its value is greater than the value of this mask thickness. Increasing the thickness makes it difficult to form slots in the shadow mask, leading to a sharp increase in cost.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a color picture tube having a shadow mask that improves doming characteristics using conventional processing techniques.

[Means to solve the problem]

A color picture tube according to the present invention is a color picture tube equipped with a striped phosphor screen and a shadow mask having slots, in which the pitch between the slots and the slot width of the shadow mask are gradually widened from the center of the mask toward the periphery. In addition, the mask plate is characterized in that a thicker area is provided on the peripheral side than in the central area.

[For production]

In this invention, the effect of reducing doming can be obtained by making the shadow mask thicker at the periphery than at the center of the screen, where doming is greater.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a plan view of a shadow mask used in a color picture tube according to the present invention, in which 1 indicates the shadow mask;
2 is a slot that is aligned and opened in this master.

Line C-C is the center of the master, PC is the lateral pitch of the slot at the center of the mask, Po is the lateral pitch of the slot at the periphery of the mask, Sl, lc are the slot widths at the center of the mask, and Swe is the lateral pitch of the slot at the periphery of the mask. It is the slot width. Further, FIG. 2 is a sectional view taken along the line ■--■ in FIG. 1, where tc is the thickness of the mask at the center, and t is the thickness at the periphery of the mask.

Further, the slot pitch Pc at the center of the shadow mask is generally determined by the screen size and target resolution of the color picture tube. Once this is determined, the slot width of the shadow mask is strictly determined by the width of the beam passing through the slot and how to set the landing margin, but in general, s wc = ""'r, and this slot width can be opened economically. The board thickness is wide. ≧7tc Therefore, tc≦Pc. Conventionally, a uniform shadow mask having a mask plate thickness of 1C has been used.

On the other hand, as shown in the beam movement characteristic diagram shown in FIG. 7, the magnitude of doming increases as the distance from the center of the screen increases, and the maximum point is at the 374th position of the distance to the horizontal edge.

Therefore, since doming is inversely proportional to the thickness of the shadow mask, increasing the thickness of the mask around the mask is effective in reducing doming. Furthermore, since the slot pitch at the periphery of the mask is set to be larger than that at the center, the slot width also increases accordingly, and therefore the thickness of the mask plate at which the slot width can be economically opened also increases as it approaches the periphery. This invention aims to take advantage of this point.

Specifically, the peripheral slot pitch is generally P,=1
．． Often set in the range of 2 to 1.3 PC, the slot width in this case is S,, = 1.05 to 1.2 O
It will be about 8-. Therefore, the plate thickness that can be economically opened is also t,
=1.05 to 1.20 t c , which is shown in the cross-sectional view of the shadow mask shown in FIG.

As a result, the mask plate thickness can be increased by 5 to 15% in the wA region where doming is actually large, and doming can be reduced by approximately the same ratio.

In addition, in the example, an example was shown in which the thickness of the shadow mask l was gradually thickened from the center to the periphery, but as shown in FIG. You can.

〔Effect of the invention〕

As explained above, according to the present invention, the thickness of the shadow mask is increased by providing a thicker region on the peripheral side than in the center, thereby improving the doming characteristics in the region around the mask where doming is likely to be a problem. A picture tube is obtained.

[Brief explanation of drawings]

The first part is a plan view of a shadow mask for a color picture tube according to the present invention, and the second part is a cross-sectional view taken along the line ■-■ in Fig. 1.
FIG. 3 is a sectional view of a shadow mask according to another embodiment of the present invention, FIG. 4 is a plan view of a conventional shadow mask, FIG. 5 is a sectional view taken along the line ■-V in FIG. 4, and FIG. 6 is a panel view. and a schematic diagram of a shadow mask, and FIG. 7 is a characteristic diagram showing the relationship between the amount of beam movement and the horizontal distance from the center of the screen. 1...Shadow mask, 2...Slot, PC...
- Slot pitch at the center of the mask, P, ... Slot pitch at the periphery of the mask, S-+++ Slot width at the center of the mask, S, ... Slot width at the periphery of the mask. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] In a color picture tube equipped with a striped phosphor screen and a shadow mask having slots, the pitch between the slots and the slot width of the shadow mask are gradually widened from the center of the mask toward the periphery, and the thickness of the mask is increased at the center. A color picture tube characterized by having a thicker area on the peripheral side.