JP2763571B2 - Correction lens for color picture tube fluorescent screen formation - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correction lens used in an exposure step when a fluorescent screen of a color picture tube is formed by exposure and development.

2. Description of the Related Art As the resolution and brightness of a color picture tube have been increased, it has been desired to further improve the phosphor screen quality, and high precision is also required for exposure processing using a correction lens.

In the formation of a so-called black matrix type phosphor screen having a light-absorbing black film, a black film having a large number of stripe-shaped or dot-shaped holes is first formed,
Next, a stripe-like or dot-like phosphor film is formed in the hole. For this reason, the hole and the phosphor film occupy substantially the same position, but it is important that the hole and the phosphor film are correctly positioned at the position where the electron beam is projected.

Various correction lenses are used for such alignment (registration correction). Such correction lenses include those having a continuous curved surface and those having a discontinuous curved surface, all of which are for refracting an exposure light beam to approximate an actual electron beam trajectory. Surface.

In a color picture tube having a striped phosphor film,
Since the phosphor film has a vertically long band shape, even if the phosphor film and the electron beam emitted for stimulating the phosphor film are displaced in the vertical direction, no color misregistration is caused thereby. Therefore, it is only necessary to consider the landing correction of the beam in the horizontal direction, and the degree of freedom in designing the correction lens is high. However, since such phosphor screens cannot arrange phosphor films at high density, high resolution cannot be obtained.

For this reason, a color picture tube requiring a high resolution, such as for a computer terminal, uses a dot type having a phosphor screen formed of a dot-shaped phosphor film.

In forming the fluorescent screen of such a dot type color picture tube, both horizontal and vertical landing corrections must be performed, and various correction lenses are used so as to obtain an optimum correction amount.

An exposure table incorporating a discontinuous type correcting lens as disclosed in Japanese Patent Publication No. 47-40983 is constructed as shown in FIG. That is, the face panel 5 on which the shadow mask 4 is mounted is placed on the exposure table 3 in which the light source 1 and the correction lens 2 are provided. Reference numeral 6 denotes a photosensitive film.

The correction lens 2 has a planar shape as shown in FIGS. 11A to 11C and a cross-sectional shape in the horizontal (X) and vertical (Y) directions, and has a plurality of square or rectangular shapes in the X and Y directions. , And each block is inclined at a predetermined angle in the X direction and the Y direction except for those at the center.

After the exposure light beam emitted from the light source 1 is refracted by the correction lens 2, it reaches the inner surface of the face panel 5 through the aperture of the shadow mask 4, and exposes and cures the photosensitive film 6. Is projected onto the photosensitive film 6 and printed as it is, so that the correction lens 2 during the exposure processing period
A vibration mechanism is required to vibrate in both the X and Y directions. Further, when a linear light source is used as in the invention disclosed in Japanese Patent Publication No. 55-44418 and a correction lens having a discontinuous boundary surface only in the longitudinal direction is used, the photosensitivity of the discontinuous boundary surface is reduced. In this case, the vibration mechanism as described above is not required because the projection on the film can be blurred.

However, when the exposure process is performed using the linear light source as described above, the dot holes and the phosphor film become non-circular. Further, if the inclination angles of many blocks of the correction lens are different in the division direction of the blocks, the projected images on the photosensitive film partially overlap and the exposure amount becomes non-uniform. In addition, not only must the vibration distance or speed be selected according to the tilt angle, but also the design of an optical filter for adjusting the illuminance distribution becomes very difficult.

On the other hand, if a correction lens obtained by dividing a block in both the X and Y directions is used, circular dots can be obtained, but a large number of small blocks are required. A mold is made by combining the molds, and a resin liquid is injected into the mold to obtain a synthetic resin correction lens. However, such resin molding makes it difficult to obtain high processing accuracy, and the practical heat-resistant temperature of the resin lens is as high as 80 ° C., so that temperature control during use is necessary. Further, the transparency is reduced during use, so that the life is short. Furthermore, it is necessary to apply vibrations in a plurality of directions for blurring so that the pattern of the block boundary surface is not projected onto the photosensitive film as it is, which complicates the configuration of the exposure table.

In the formation of the dot-type phosphor screen, it is necessary to simultaneously perform registration correction in both the horizontal and vertical directions, so that it is difficult to apply a correction lens having a continuous curved surface. For example, as shown in FIG. 12, considering the correction in the case where the electron beam enters the dot-shaped phosphor film at the four corners of the phosphor screen while being shifted in the + X direction, the phosphor film moves in the + X direction. The curved surface of the correction lens must be corrected so that it can be printed. However, it is impossible to move only the four corners in the X direction without moving the dot-shaped phosphor film in the Y direction, unless a correction lens having a continuous curved surface is used. It will involve the desired movement.

Means for Solving the Problems The present invention relates to a correction lens in which a plurality of band-shaped regions are connected in the width direction to form a discontinuous surface, and a cross-sectional shape of each of the band-shaped regions in a longitudinal direction is formed on a lens main surface. The belt-shaped region is configured so as to have a surface of a straight line or a curved line having a predetermined inclination, and the cross-sectional shape in each width direction of the band-shaped region has a surface of a straight line substantially parallel to the lens main surface. .

In the correction lens configured as described above, since the belt-shaped regions are continuous in the width direction without a change in the inclination, the projected image of the lens on the photosensitive film is similar to the lens pattern, and the uneven light amount due to the overlapping of the projected images. It is possible to perform exposure processing with a small amount of light even by simply applying a simple vibration to the correction lens, and it is only necessary to perform vibration in one direction, so that the exposure apparatus can be simplified. Further, the optical filter having a continuous distribution can sufficiently cope with it. Further, since each of the belt-like regions constituting the correction lens has a relatively large surface, the glass can be polished and formed accurately.

Next, the present invention will be described with reference to embodiments shown in the drawings.

As shown in FIG. 1, a large number of glass blocks 8a to 8e forming a band-shaped region of the correction lens 7 having a discontinuous curved surface have a wedge-shaped X-direction cross-sectional shape except for a central block 8c. The respective surface inclination angles with respect to the lens principal surface 9 serving as the horizontal reference plane are 8a>8b> 8c <8d> 8e, and gradually increase toward the lens periphery, and are symmetric with respect to the X axis. is there.

FIG. 2 shows an exposure table incorporating such a discontinuous curved surface correction lens 7 together with a conventional continuous curved surface correction lens 10, and its operation is as follows.

Misregistration in which the point of incidence of the electron beam is displaced in the direction indicated by the arrow in FIG. 3 cannot be corrected using a correction lens having a continuous curved surface (A, B, and C require correction). Not position). If this pattern X
In order to correct only the direction deviation, FIG.
Assuming that a correction lens having a wedge-shaped cross section is used as shown in (b) and (c), this correction lens has a continuous curved surface although the inclination in the X direction becomes steeper as the distance from the X axis increases. Therefore, the inclination in the Y direction is automatically determined. As a result, as shown in FIG. 7, even if the dot-shaped phosphor film can be moved outward on the + X side and inward on the -X side, the direction opposite to the desired direction in the Y direction is obtained. Move to.

On the other hand, when a correction lens having a discontinuous curved surface as shown in FIG. 1 embodying the present invention is used, the phosphor film can be moved only in the X direction as shown in FIG. 4 without moving in the Y direction. Can be. That is, the misregistration in FIG. 3 can be corrected as shown in FIG. The pattern shown in FIG. 5 can be easily corrected by the conventional continuous curved surface correction lens 10.

The discontinuous curved surface correction lens according to the second embodiment of the present invention
(A) and (b) of FIG. This correction lens is formed symmetrically with respect to each of the X axis and the Y axis.
The block 8c on the axis forms a strong concave lens in the X direction near the center, and from the block 8c to the blocks 8b and 8c, and also to the blocks 8d and 8e, the curved surface gradually slopes away from the X axis. It has become.

By using such a correction lens, the dot-shaped phosphor film near the center of the phosphor screen can be moved inward as shown in FIG.

In the shadow mask type color picture tube, there is a doming phenomenon in which the vicinity of the center of the shadow mask is locally thermally expanded during operation. When such a phenomenon occurs, the aperture of the shadow mask moves toward the center, and the electron beam takes a trajectory closer to the inside than the predetermined trajectory and hits the phosphor screen. For this reason, it is desirable that the attachment position of the dot-shaped phosphor film is set slightly inward from the electron beam projection point in normal times, and such a correction lens as shown in FIG. 8 is used. Correction can be easily performed.

In the above-described embodiment, the blocks constituting the correction lens are divided in the Y direction, but may be divided in the X direction.
Further, it goes without saying that the face panel side may be vibrated instead of vibrating the lens in order to blur the light amount unevenness.

Effects of the Invention As described above, according to the present invention, even though the correction lens has a discontinuous surface, the influence of uneven light amount can be reduced, and the configuration of the exposure table and the optical filter can be simplified. In addition, since it can be formed of glass, not only can the processing accuracy be improved, but also management becomes easy, and in particular,
By using in combination with a conventional continuous curved surface correction lens, it is possible to cope with correction of any pattern.

[Brief description of the drawings]

FIG. 1 is a perspective view of a correction lens embodying the present invention, FIG. 2 is a side sectional view of an exposure table incorporating the correction lens, and FIGS. 3 to 5 show misregistration and the procedure of correction. FIGS. 6A, 6B, and 6C are front views of a continuous curved surface correction lens having a wedge-shaped cross-sectional shape and its X- and Y-direction cross-sectional views. 8A and 8B are a plan view and a side sectional view of a correction lens according to a second embodiment of the present invention, and FIG. 9 is a diagram showing a correction pattern using the same correction lens. FIG. 10 is a side sectional view of a conventional exposure table, and FIGS. 11 (a), (b) and (c) are plan views of the conventional correction lens and its X and Y sectional views, and FIG. Figure and first
FIG. 3 is a pattern diagram for explaining the conventional procedure of misregistration and its correction. 7 correction lens, 8a to 8e block, 9 lens main surface.

Claims (1)

(57) [Claims] 1. A correction lens in which a plurality of band-shaped regions are connected in the width direction to form a discontinuous surface, wherein each of the band-shaped regions has a predetermined cross-sectional shape in a longitudinal direction with respect to a lens main surface. A color picture tube having a sloped straight or curved surface, wherein the cross-sectional shape of each of the band-shaped regions in a width direction has a straight surface substantially parallel to the lens main surface; Correction lens for phosphor screen formation.