JPH0456038A - Exposure device for color image receiving tube - Google Patents

Abstract

PURPOSE:To provide good landing characteristics over the whole surface of a fluorescent screen by forming a correction lens so that the refractive index varies continuously from the center of the lens toward the peripheries. CONSTITUTION:The refractive index of a correction lens 22 varies approx. continuously from the center of the lens toward its peripheries as a first order function of the radius about the lens center. Use of this sort of lens 32 permits the moving amount of the beam of light 21 emitted by a light source 20 on the inner surface of a panel 1 along the vertical Y-axis to be different from that along the horizontal axis. That is the movement along the vertical axis can be made twice as large as the movement along the horizontal axis, which allows solving problems in designing a correction lens 22 resulting from difference in the deflection center between the horizontal and vertical axis direction. Thus a fluorescent screen with required characteristics can be accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) This invention relates to an exposure apparatus used for forming a phosphor screen of a color picture tube.

(Prior Art) Generally, a color picture tube has a panel (
1) and a funnel (2), the panel (1) faces a shadow mask (3) in which a large number of electron beam passing holes are formed and is mounted inside the panel (1). ) A phosphor screen (4) is formed on the inner surface. This phosphor screen (4) consists of a stripe-shaped or dot-shaped three-color phosphor layer that emits blue, green, and red light. In addition, in order to improve the contrast of the image drawn on this phosphor screen (4),
There is a so-called black stripe type or black matrix type in which a non-emissive layer mainly composed of carbon or the like is provided in the gap between the color phosphor layers.

The image is displayed on the phosphor screen (4) using three electron beams (613>) emitted from the electron gun (5).

(6G) and (G)i) are deflected horizontally and vertically by a magnetic field formed by a deflection yoke (7) attached to the outside of the funnel (2), and the phosphor screen (4) is scanned horizontally and vertically. It is done by doing.

Therefore, in order to display an image with good color purity on this phosphor screen (4), as shown in FIG.
8) Each electron beam (BB) passed through (6c)
, (OR) respectively correspond to three color phosphor layers (9B)
It is necessary to land correctly on , (9G), and (9R). Regarding this landing, the electron beam passage hole (8) of the shadow mask (3)
and three-color phosphor layer (9B), (9G), (9R)
The positional relationship with each electron beam (13B), (6G
), (6R) The apparent upper injection position (deflection center) changes according to the deflection angle.

Therefore, each phosphor layer of three colors (9B), (9G)
, 3 electron beams (8B) corresponding to (9R)
, (8G), and (6R) to land correctly, the electron beam passing hole (
8) Three-color phosphor layer (913), (9G)
, (9R) needs to be changed.

In other words, as shown in Fig. 6 for the center beam (6G) of three electron beams arranged in a row emitted from an in-line electron gun, the electron beam (6G) has a uniform deflection when the magnetic field strength of the deflection yoke is It moves in a circular orbit within the magnetic field (11) generated by the yoke, and after exiting the magnetic field (11) of this deflection yoke, it moves straight and enters the shadow mask (3).
) through the electron beam passage hole (8) of the phosphor layer (9G).
Land on. Therefore, electron beam (6G)
The apparent upper injection position, that is, the position of the deflection center (F) where the extension of the linear trajectory intersects with the tube axis (X-axis) is the deflection angle γ.
It changes accordingly. In other words, when the deflection angle is γ, the deflection center (P) advances toward the phosphor screen (4) by Δp, compared to the case where the deflection angle is zero (no deflection).
It has characteristics.

On the other hand, conventionally, a phosphor screen is produced by applying a phosphor slurry mainly composed of phosphor and photosensitive resin to the inner surface of a panel (1) and drying it, as shown in FIG. 7(a).
) is exposed through a shadow mask (3) to print a pattern corresponding to the electron beam passing hole (8) of the shadow mask (3), and then developed to remove the unexposed area. As shown in (b), a phosphor layer of any one color, for example a blue phosphor layer (9B), is formed. Then, each of these steps is repeated for other two-color phosphor layers.

Especially for phosphor screens with non-emissive layers.”
Prior to the formation of the two and three color phosphor layers, a photosensitive resin is applied as shown in FIG. After forming a photosensitive resin pattern (IB) corresponding to the passage holes, a non-luminescent paint is applied as shown in (b), and then this non-luminescent paint film (IB) is applied to the underlying layer. Peel off together with the photosensitive resin pattern (IB),
As shown in (C), there are voids (
17), and then, by the method for forming a phosphor layer described above, three-color phosphor layers are formed in the voids (17) of the non-emissive layer (18). Ru.

In both cases of forming the phosphor layer and the non-emissive layer, the light that exposes the phosphor slurry coating (13) formed on the inner surface of the panel and the photosensitive phosphor screen forming layer made of photosensitive resin travels in a straight line. In the exposure process, an exposure apparatus shown in FIG. 9 is used. This exposure device includes a light source (20) that emits light to be projected onto a photosensitive phosphor screen forming layer formed on the inner surface of the panel (1) through a shadow mask (3) attached to the panel (1). and its panel (1
) and the light source (20), a correction lens (22) is arranged to approximate the trajectory of the light (21) emitted from the light source (20) to the trajectory of the electron beam emitted from the electron gun, and further, This correction lens (22) and the shadow mask (
3), an opening (20) for projecting light emitted from the light source (20) onto a part of the photosensitive phosphor screen forming layer;
23) is formed, and by driving a drive device (not shown),
A shutter (24) for partial exposure is arranged so that the light passing through the aperture (23) is projected onto the entire area of the photosensitive phosphor screen forming layer.

A spherical lens was once used as the correction lens (22) disposed in such an exposure device, but as the structure of color picture tubes has become more complex, a simple lens has
It is no longer possible to correct the −Δp characteristic, and aspheric lenses with complicated surface shapes are now used.

The surface shape of this aspherical lens is expressed in an orthogonal coordinate system (X, Y, Z axes) with the origin at the center of the bottom surface of the lens, and the surface height X at any point is xw=f (y, z)・・・・・・・・・・・・・・・
... Represented by (1). Also, in polar coordinates (', θ), x-f(r, θ)...
... (2), - is expressed as "7 θ-1an-' (y/z), and within the - shell, for example, equation (1) is expressed as a polynomial.

Design of a correction lens using such a formula involves tracking how the light emitted from the light source changes over the entire phosphor screen with respect to the amount of change in each of the coefficients a and j. It is designed so that the error from the electron beam incident position across the entire screen is a constant value (usually 100 microfronfs or less. However, even if designed in this way,
It is relatively easy to reduce the error at a limited number of points on the correction lens, but even if the coefficient a+j is set to reduce the error at any point on the correction lens, the coefficient a1j is generally Since it acts to increase the error at most other points, it is extremely difficult to design the error at all points on the phosphor screen to be less than a desired error. Even if a high-performance ultra-high-speed computer is used, not only is the design time-consuming, but in many cases, changing the coefficients ajj requires judgment based on extensive experience.

Therefore, in color picture tubes with complex deflection magnetic fields, such as 110-degree deflection color picture tubes with large deflection angles and large color picture tubes, it takes a lot of time to design the correction lens, and it is difficult to achieve the desired γ-Δp characteristics. It cannot be used as a correction lens with

As another method of designing correction lenses,
In Publication No. 83 and Japanese Patent Publication No. 49-22770, the first
As shown in Figure O, a method is shown in which the correction lens (22) is divided into a plurality of parts and the slope of the surface of each part is determined. With such a method, the trajectory of light can be accurately approximated to the trajectory of the electron beam for each divided portion, and a correction lens that fully satisfies the γ-Δp characteristic can be obtained.

However, such a correction lens (22) has a step (26) at the boundary between the divided parts, so it is particularly difficult to use a black stripe type or black lens in which a non-emissive layer is provided between the three-color phosphor layers. For a matrix-type phosphor screen, unevenness is likely to occur on the phosphor screen due to non-uniformity in the amount of light caused by the steps (26). Methods to solve this problem include a method of swinging the correction lens (22) during exposure and a method of shielding the stepped portion from light, but neither of these methods can sufficiently reduce the unevenness of the phosphor screen.

(Problems to be Solved by the Invention) As described above, in the phosphor screen of a color picture tube, a pattern corresponding to the electron beam passing holes of the shadow mask is printed on the photosensitive phosphor screen forming layer formed on the inner surface of the panel. When attaching the beam, a correction lens is used to approximate the trajectory of the light emitted from the light source to the trajectory of the electron beam deflected by the magnetic field formed by the deflection yoke. However, the surface shape of this correction lens is complex and it is difficult to design it so that good landing can be obtained at all points on the phosphor screen, especially for wide deflection angle color picture tubes and large color picture tubes. For color picture tubes with complex deflection magnetic fields, such as those with complicated deflection magnetic fields, the desired correction lens cannot be obtained.

As a result of various investigations into the causes, the inventor discovered that the major cause of difficulty in designing a correction lens is the difference between the γ-Δp characteristics of horizontal deflection and the γ-Δp characteristics of vertical deflection of electron beams. I found a headline.

That is, the surface height X at an arbitrary point P of the correction lens (22) shown in FIG. On-axis (Z-axis) and vertical axis (Y-axis)
For the above, each curve is a curve that completely satisfies each landing characteristic, so the surface height only if it matches,
Both the Y-axis direction and the Z-axis direction are completely corrected. However, as shown in Figure 12(a), 21 on the Z axis
When the surface height of point P is determined from this zl in the Y-axis direction, the surface height of point P becomes x2 on the curve (28a). On the other hand, the same (b
), the surface height x(y
, 0), and determine the surface height of point P in the Z-axis direction from this yl, the surface height of point P is curved (28b)
The above becomes X3, and the correction from the Z-axis to the Y-axis direction and the correction from the Y-axis to the Z-axis direction do not necessarily match. In fact, there are many cases where they do not match.

This is based on the difference between the center of deflection when the electron beam is deflected in the horizontal direction and the center of deflection when it is deflected in the vertical direction. In this respect, it has been found that it is impossible to design a correction lens that satisfactorily corrects the landing error.

This problem is most likely to occur in color picture tubes, such as black-striped color picture tubes, which have a phosphor screen consisting of a phosphor layer in the form of long stripes in the vertical direction, and do not require consideration of vertical landing. Although this is not so much of a problem, it has a significant effect on color picture tubes with dot-shaped phosphor layers, especially wide deflection angle color picture tubes with a deflection angle of 110 degrees, and large color picture tubes.

This invention was made in view of the above problems, and
It is an object of the present invention to configure an exposure apparatus that can easily form a phosphor screen that cannot be sufficiently corrected with a conventional correction lens.

[Structure of the Invention] (Means for Solving the Problems) In an exposure device for a color picture tube used to form a phosphor screen of a color picture tube, a photosensitive phosphor formed on the inner surface of a panel positioned at a predetermined position. A correction lens that approximates the trajectory of the light emitted from the light source projected onto the screen forming layer to the trajectory of the electron beam emitted from the electron gun of a color picture tube is refracted almost continuously from the center of the lens toward the periphery. The lens has a variable ratio.

(Function) As described above, the correction lens that approximates the trajectory of the light emitted from the light source to the trajectory of the electron beam emitted from the electron gun of a color picture tube is installed almost continuously from the center of the lens toward the periphery. If the lens has a refractive index that changes in Therefore, a color picture tube with good landing characteristics can be manufactured.

(Example) Hereinafter, the present invention will be described based on an example with reference to the drawings.

FIG. 1 shows an exposure apparatus that is one embodiment of the present invention.

This exposure apparatus has a support base (30) that positions and supports the panel (1), and a light source (
20) are arranged. As this light source (20),
Typically, air-cooled or water-cooled ultra-high pressure mercury lamps are used. The support stand (30) is placed on this light source (20).
) A light source (20) that projects through a shadow mask (3) onto a photosensitive phosphor screen forming layer (31) such as phosphor slurry or photosensitive resin coated on the inner surface of the panel (1) positioned at A correction lens (32) made of an aspherical lens that approximates the trajectory of the light (2I) emitted from the
) are placed.

This correction lens (32) is usually made of graded refractive index glass (
GRIN) (Gradlent Index Gl
It is made of glass called FF1
As shown by the straight line (34) in FIG. 2, the refractive index changes almost continuously from the center of the lens toward the periphery as a linear function of the radius from the center of the lens. Here, "nearly continuous" does not only mean that it changes continuously;
This also includes cases where there is a gradual change. In the illustrated lens, the refractive index at the lens center O is 1.50, increases in proportion to the radius toward the periphery, and changes to 1.60 outside the lens P.

When such a correction lens (32) is used, the light source (2)
The amount of movement of the light (21) emitted from the panel (1) on the inner surface of the panel (1) can be made different in the vertical axis (Y-axis) direction and the horizontal axis (Z-axis) direction. That is, as shown in FIGS. 3(a) and 3(b), for a 32-inch color picture tube with an aspect ratio of 16:9, a correction lens (32) with the refractive index distribution shown in FIG. 2 is arranged, and the panel is (1) As a result of measuring the amount of movement of light on the inner surface, when a correction lens with a constant refractive index of 1.54 is placed, as shown in (a), the vertical axis 130μ at the top, 34 at the diagonal
It moved by 0 μm, and the difference was 210 μm, but (b)
As shown in , the movement in the horizontal axis direction was almost zero on both the vertical axis and the horizontal axis, and the movement was 100 μ in the diagonal area. That is,
By using the refractive index distribution correction lens (32) shown in Figure 2 above, it is possible to move approximately twice as much in the vertical axis direction as in the horizontal axis direction. A desired phosphor screen can be formed by solving the design problem of the correction lens (22) due to the difference in the deflection center.

In the above embodiment, the refractive index of the correction lens is changed by a linear function of the radius from the center of the lens, but the refractive index of the correction lens may be changed by another function.
Further, instead of being a function of the radius from the center of the lens, it may be a function of the position in the horizontal axis direction or the vertical axis direction. Alternatively, the correction lens may be manufactured by appropriately designing a correction lens, measuring the refractive index of the lens, and determining a surface expression for the necessary correction lens based on the measured data.

[Effect of the invention] A correction lens that approximates the trajectory of the light emitted from the light source projected onto the phosphor screen forming layer formed on the inner surface of the panel to the trajectory of the electron beam emitted from the electron gun of the color picture tube is equipped with a refracting lens. In the past, it was difficult to design a corrective lens that had both the slope and thickness of the lens surface at all points on the lens surface, given that the ratio changes almost continuously from the center of the lens toward the periphery. is used as a product, especially for forming phosphor screens for wide deflection angle color picture tubes and large color picture tubes where the three-color phosphor layer of the phosphor screen is dot-shaped and the electron beam passage hole of the shadow mask is circular. This can be used to create a color picture tube with good landing characteristics over the entire phosphor screen.

[Brief explanation of drawings]

Figures 1 to 3 are detailed explanatory diagrams of this invention.
The figure shows the main part configuration of an exposure device for a color picture tube, which is an embodiment of the same, FIG. 2 shows the change in the refractive index of the correction lens, and FIGS. A diagram showing the amount of movement of light from the light source in the vertical axis direction and a diagram showing the amount of movement in the horizontal axis direction by the correction lens, Figure 4 is a diagram showing the configuration of a color picture tube, and Figure 5 is a diagram showing the amount of movement of light from the light source in the horizontal axis direction. FIG. 6 is a diagram for explaining the positional relationship between the color phosphor layer and the electron beam passing hole of the shadow mask. FIG. 6 is a diagram for explaining the influence of the deflection magnetic field on the electron beam. FIG. 7(a)
and (b) are diagrams for explaining the method for forming three-color phosphor layers of a color picture tube phosphor screen, and FIG.
a) to C) are diagrams for explaining the method of forming a non-emissive layer of a color picture tube phosphor screen, respectively; FIG. 9 is a diagram showing the configuration of a conventional color picture tube exposure device; and FIG.
Figures (a) and (b) are a plan view and a sectional view showing the configuration of a correction lens divided into multiple parts, respectively, and the first
Figure 1 is a diagram for explaining the conventional correction lens design method, and Figures 12 (a) and (b) are the surface shape and y of the z-P cross section of the conventional compensation lens shown in Figure 11, respectively.
It is a figure showing the surface shape of the -p cross section. 1... Panel, 20... Light source, 21...
Light, 31... Photosensitive phosphor screen forming layer, 33...
Correcting lens, agent Patent attorney Norio Ogo

Claims (1)

[Claims] The photosensitive phosphor screen forming layer is provided between a panel positioned at a predetermined position and a light source that emits light to be projected onto the photosensitive phosphor screen forming layer formed on the inner surface of the panel. In a color picture tube exposure device that is equipped with a correction lens that approximates the trajectory of the projected light to the trajectory of the electron beam emitted from the electron gun of the color picture tube, the correction lens has a refractive index that changes from the center of the lens to the periphery. 1. An exposure device for a color picture tube, characterized by comprising a lens that changes almost continuously as it approaches.