JPH07111876B2 - Color picture tube - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a shadow mask type color picture tube, and more particularly to a curved surface shape of a shadow mask.

[Technical background of the invention and its problems]

The shadow mask used in the shadow mask type color picture tube is one of the important members having a color selection function. That is, a shadow mask consisting of an effective curved surface portion having a large number of apertures regularly arranged at regular intervals with respect to the curved inner surface of a panel in which phosphors emitting light of multiple colors are separately coated. Are arranged. Then, a plurality of electron beams from the electron gun arranged in the neck portion of the tube are focused, accelerated, and deflected to scan a substantially rectangular area and pass through the opening of the shadow mask. Then, the corresponding phosphors are made to project and emit a color image. Therefore, a certain relative positional relationship is required between the aperture group of the shear mask and the corresponding phosphor group in order to make the so-called beam landing accurate, and this relative relationship is always kept constant during the operation of the picture tube. I have to keep it.
More specifically, the distance between the shed mask and the phosphor screen (hereinafter abbreviated as q value) must always be within a certain allowable range. However, due to its operating principle, the sheer mask type color picture tube has an electron beam amount of less than 1/3 that passes through the opening of the sheer mask, and the remaining electron beams impinge on the non-rear portion of the sheer mask. The projected electron beam is converted into thermal energy and heats and expands the shear mask. As a result, in general, a shear mask made of a material containing iron as a main component changes the position of the shear mask due to thermal expansion, and when the q value changes outside the allowable range, the deviation of the beam landing position causes deterioration of color purity. The magnitude of mislanding caused by the thermal expansion of such a shed mask greatly differs depending on the pattern of the image on the screen and the duration of this pattern.

Of these, mislanding that takes a long time is corrected by interposing a bimetal in the spring support structure attached to the mask frame holding the shear mask, as shown in JP-B-44-3547. Is possible. Therefore, a big problem is mislanding that occurs in a short time.

Regarding mislanding that occurs in a short time, using a signal device that generates a rectangular window-shaped pattern and measuring the size of the mislanding by changing the shape and position of the window-shaped pattern, as shown in Fig. 3. If there is a window-shaped pattern (7) across almost the entire screen (8), the mislanding is relatively small. However, as shown in FIG. 4, the largest mislanding occurs when the relatively elongated window-shaped pattern (7) is unevenly distributed from the left and right ends of the contour of the screen (8) to the center. This experimental fact can be easily understood for the following reason.

First, the television set is designed so that the average anode current of the picture tube does not exceed a certain value.
In the case of a large window-shaped pattern as shown in the figure, the current per unit area of the shadow mask is smaller than that in the case of FIG. 4, and therefore the temperature rise is small.

Secondly, if the window pattern is in the center of the screen, mislanding does not easily occur even if the shear mask thermally deforms. growing. However, since the shear mask is fixed to the mask frame near the left and right edges of the screen, the deformation itself is small. Therefore, the largest mislanding occurs in the case of the window pattern shown in FIG.

FIG. 5 is a schematic diagram for explaining a mislanding state in the case where there is a window pattern as shown in FIG. That is, the shadow mask (14) is arranged opposite to the inner surface (10) of the panel (9) via the stud pin (11), the spring support structure (12) and the mask frame (13). The shadow mask (14) when it is operating at a low brightness, that is, a low electron flow density, is at the position (a),
The electron beam (16) passing through the aperture (15) is correctly landing on the corresponding phosphor (17). When a locally high-intensity pattern as shown in FIG. 4 is projected from this state, the shear mask (14) is locally heated and expanded to be displaced to the position (a ') and the opening (15). Is displaced from the position (b) to (b '), and as a result, the electron beam (16) passing through the aperture (15) is displaced from the position (c) to (c') and is not properly landed on the predetermined phosphor. .

In order to prevent such thermal deformation of the sheer dough mask in a short time, the fixing portion of the sheer dough mask to the mask frame is made as flexible as possible, and the dome-shaped deformation as shown in FIG. 6 (a) is changed to that shown in FIG. 6 (b). Shed mask (1
4) A method of translating the entire pipe in the axial direction is also adopted. However, even if such a measure is effective for the displacement due to the overall thermal expansion as shown in FIG.
The local displacement shown in the figure has almost no effect. This tendency is remarkable especially in a large-sized tube having a large screen, and also in a tube having the same size but a large radius of curvature of the shadow mask, that is, a flattened tube which is visually preferable.

[Object of the Invention]

The present invention has been made in view of the above points, and it is an object of the present invention to suppress the deterioration of the color purity caused by the local thermal expansion of the shear mask.

[Outline of Invention]

An axis passing through the center of the effective curved surface in the substantially long side direction of the substantially rectangular shape is defined as an X axis, and an axis passing through the center of the effective curved surface in the direction of the short side is defined as a Y axis.
When the axis coinciding with the tube axis is the Z axis, the cross section of the effective curved surface portion of the shadow mask and the plane including the X axis and the Z axis has the X axis as the major axis and the Z axis as the minor axis, and X, Y, The cross section of the effective curved surface of the shadow mask and the plane parallel to the plane including the Y axis and the Z axis forms a part of an elliptic curve with the origin of the Z axis as the apex, and the radius of curvature near the X axis is When RVO and the radius of curvature near the long side are RVY, by configuring so that RVO ≦ RVY, in the vicinity of the region where the local doming is maximum,
By reducing the radius of curvature in the direction parallel to the Y-axis near the X-axis and reducing the thermal deformation in this region, the deterioration of color purity is effectively suppressed.

Example of Invention

Examples of the present invention will be described in detail below. When a window-like pattern as shown in FIG. 4 is projected, only the area (18) where the electron beam impinges on the shadow mask (14) is projected during the initial 2-3 minutes as shown in FIG. Thermal expansion causes local mislanding. When the temperature rise of the window-shaped pattern portion of the shadow mask (14) at this time is measured, the center point M on the X-axis rises to about 70 ° C. at the upper and lower points N, that is, the Y-axis of the window pattern. A-parallel to
The temperature rises to about 25 ° C at both ends of the A'axis. From this, it can be seen that, in the region (18), the thermal expansion in the vicinity of the X axis is larger than the thermal expansion in the portion away from the X axis. In other words, if the deformation near the X axis is reduced, the thermal deformation of the entire region (18) can be reduced.

As for the curved surface shape of the shear mask, a partial spherical surface is conventionally used. However, in order to optimize the q value, Alternatively, Shapes such as displayed may also be used.

However, θ: Angle with respect to Y-axis R _H : Radius of arc on X-axis R _VO : Radius of arc on Y-axis A, B, C, k: Constant In the expression of (1), the shadow mask passing through the center of the screen Arbitrary cross section is one arc, X axis, Y in the display of formula (2)
An arbitrary cross section parallel to the axis and the Y-axis is represented by one arc.

FIG. 1 shows an embodiment of the present invention, and is indicated by X in FIG.
The cross section along the line BB 'is shown on the axis.

In FIG. 1, the cross section of the effective curved surface portion of the shadow mask and the plane including the X axis and the Z axis (hereinafter also simply referred to as the X axis cross section) has a shape (1) and (2). )
Is represented by one arc, the shape (2) according to the present invention is formed by a part of an elliptic curve having the X axis as the major axis and the Z axis as the minor axis. On the other hand, the cross section of the shadow mask effective curved surface portion and the plane parallel to the plane including the Y axis and the Z axis (hereinafter, also simply referred to as the cross section in the direction parallel to the Y axis) has the shape of the above embodiment and the equation (1) and The shape is represented by the formula (2) and the shape is a circular arc. However, by changing the shape of the X-axis cross section, the radius of curvature changes in the shape of the embodiment as compared with the conventional arc shape. If the cross section on the Y-axis and in the outermost portion of the effective diameter parallel to the Y-axis is an arc, the radius of curvature of the cross section in the direction parallel to the Y-axis of the intermediate portion is as shown in FIG. ) Is smaller than the conventional arc shape (5). In particular, the difference becomes large in the vicinity of point M in FIG.
The radius of curvature parallel to the Y-axis has a great effect on the thermal deformation of the shear mask, and the smaller the radius of curvature, the smaller the local mislanding. Therefore, the local mislanding can be effectively corrected if the radius of curvature in the direction parallel to the Y axis near the point M where the local mislanding due to thermal expansion is the largest becomes small. Therefore, by using the shadow mask shape according to the present invention, by changing the lengths of the major axis and the minor axis of the elliptic curve, the radius of curvature in the direction parallel to the Y axis near the point M is adjusted, and the maximum mislanding point is reached. Can have the maximum correction effect. That is, local mislanding can be suppressed very effectively.

For example, in the 20-inch 90 ° deflection color picture tube, the conventional (2)
Whereas the shape represented by the formula and the radius of curvature of the X axis is R _H = 1080 mm, as an embodiment of the present invention, for example, the long axis Ra = 241.68.
mm, short axis Rb = 46.53 mm, the local mislanding could be improved by 20%.

In the ellipse, the ratio of the major axis Ra and the minor axis Rb changes depending on the eccentricity ε, and ε takes a value in the range of 0ε <1. Ε for a circle
= 0. The closer the eccentricity ε is to 0, the closer it is to a circle. Therefore, the radius of curvature of the cross section of the shear mask in the direction parallel to the Y-axis does not become small, and it is not possible to have a sufficient correction effect for local mislanding. That is, 0.5
The above is necessary. Therefore, the range of ε is 0.5ε <
1.0 is appropriate.

The elliptic curve along the X axis may be a substantially elliptic curve by combining two or more radiuses of curvature.

In the above description, the cross section in the direction parallel to the Y-axis is represented by one arc, but this is not always necessary. However, for local mislanding due to thermal expansion of the shear mask, the radius of curvature in the direction parallel to the Y axis near the X axis is the most effective and the smaller the better. For this reason, the cross section in the direction parallel to the Y-axis has at least one arc, or unless the radius of curvature on the X-axis of this cross-section is made smaller than the radius apart from the X-axis, for example, the radius of curvature in the vicinity of the long side, it is localized. Mislanding cannot be effectively corrected.

In the case of the sheer mask having the above structure, the q value may be locally deviated from the optimum value. However, if the amount is out of the allowable value, it is particularly preferable to make the inner surface shape of the panel similar to that of the sheer mask. There is no problem. In this case, the raster distortion characteristics and the like change, but the change amount is small and causes almost no problem. With the 20-inch color picture tube described above, it was not easy to discern visually, so it was not a practical problem.

〔The invention's effect〕

As described above, according to the present invention, it is possible to effectively suppress the deterioration of the color purity due to local thermal deformation by only partially changing the curved surface shape without significantly changing the structure of the shear mask. it can.

[Brief description of drawings]

1 and 2 are schematic views showing an embodiment of the present invention, and FIG.
FIGS. 4 and 5 are schematic diagrams showing the projected pattern, FIGS. 5 and 7 are schematic diagrams for explaining local thermal deformation of the sheer dough mask, and FIGS. 6 (a) and 6 (b) are It is a schematic diagram for demonstrating the whole thermal deformation of a shear mask. (1), (2) …… Shadow mask cross section (5), (6) …… Shadow mask cross section (7) …… Window pattern, (8) …… Screen outline (9) …… Panel, (10)… … Inside panel (11) …… stud pin, (12) …… spring support structure (13) …… frame, (14) …… shadow mask (15) …… opening, (16) …… electron beam (17)… … Phosphor, (18) …… Electron beam impingement area

Claims (4)

[Claims] 1. A substantially rectangular panel having a phosphor group formed on the inner surface thereof, and a substantially rectangular effective curved surface portion and a rule in the effective curved surface portion which are arranged in close proximity to the panel. In a color picture tube provided with a shadow mask having a large number of arranged apertures, an axis passing through the center of the effective curved surface portion of the substantially rectangular long side is defined as the X axis, and the center of the effective curved surface portion in the short side direction is defined as When the axis passing through is the Y axis and the axis coinciding with the tube axis is the Z axis, the effective curved surface portion of the shadow mask and the X axis and the Z axis.
The cross section with the plane including the axis is substantially a part of an elliptic curve having the X axis as a long axis, the Z axis as a short axis, and the origins of the X, Y, and Z axes as apexes, and the shadow mask The cross section of the effective curved surface part of X and the plane parallel to the plane including the Y axis and the Z axis is X.
Let RVO be the radius of curvature near the axis and R be the radius of curvature near the long side.
A color picture tube characterized in that when VY, RVO ≤ RVY. 2. The color picture tube according to claim 1, wherein the eccentricity of the elliptic curve is 0.5 or more and less than 1.0. 3. The color picture tube according to claim 1, wherein the elliptic curve is a curve composed of a plurality of different radii of curvature. 4. The cross section between the effective curved surface portion of the shadow mask and the plane including the Y axis and the Z axis has one or two or more different radii of curvature. Color picture tube described.