JPS6212620B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exposure apparatus that rotates an optical filter between a light source and a surface to be exposed.

In the process of forming a fluorescent surface of a color picture tube, the fluorescent photosensitive layer uniformly coated on the inner surface of the face panel is exposed to external light through an attached shadow mask, and development and other processing steps are repeated. A fluorescent surface having a large number of dots or stripes is produced by this method.

As shown in FIG. 1, a face panel 1 has a fluorescent photosensitive layer 2 coated on its inner surface, and a shadow mask 3 is attached thereto. The exposure light beam emitted from the light source 4 reaches the phosphor photosensitive layer 2 through a correction lens 5, a correction filter 6, and a shadow mask 3. The correction filter 6 for adjusting the exposure dose distribution is shown in FIG. As shown, the transmittance is low in the center and increases toward the periphery. This correction filter 6 consists of a transparent substrate 7 made of glass or the like and a metal thin film 8 made of nickel, chromium, chromel, inconel, platinum, rhodium, rubidium, etc.
It was formed by vapor deposition.

The conventional correction filter 6 has the following drawbacks. Nickel, chromium, chromel, vapor deposition materials
When Inconel is used, the metal thin film 8 undergoes a large change in transmittance over time due to oxidation, and platinum, rhodium, and rubidium have poor adhesion to the glass substrate and are difficult to handle. Furthermore, in the case of manufacturing, it is difficult to design the shape of the evaporation source and the evaporation mask to obtain the transmittance distribution shown in Figure 2, and in practice it is a process of trial and error, and it is difficult to set the evaporation conditions, making it difficult to reproduce. It was poor in quality and could only be made one piece at a time, resulting in a huge loss from an industrial perspective.

The purpose of the correction filter 6 as described above is to adjust the light intensity distribution on the phosphor photosensitive layer 2 during exposure, so in order to realize this purpose, it is necessary to use a certain transmittance like that of a conventional metal vapor deposited film. It does not have to be a semipermeable membrane with a For example, as shown in FIG. 3, if a filter 11 is formed in which a light shielding part 9 made of a substance that does not transmit any light is provided on a part of the substrate 10, and this filter 11 is rotated between the light source 4 and the face panel 1. , it is possible to obtain the same light amount limiting effect as a semi-transparent membrane.

If we consider this filter 11 further,
The light shielding part 9 has a width ω(γ) with respect to the distance γ from the center, and when it is rotated, the effective transmittance (γ) at the distance γ becomes γ≠0 and (γ)= (1-ω(γ)/2πγ)×100[%]...
...Equation 1 is obtained. In other words, to obtain the target transmittance distribution, ω
It is sufficient to determine the width of (γ).

At the rotation center where γ=0, if there is a light shield with a transmittance of 0%, the light reaching the phosphor photosensitive layer 2 will be 0, and if there is no light shield, the light reaching the photosensitive layer 2 will be 100%.
This becomes the singular point of the target transmittance distribution. As described above, the above-described filter 11 had a major problem near the center, so it was not put into practical use.

The present invention is an optical filter that can arbitrarily realize the entire transmittance distribution, including the transmittance near the center, and a method for manufacturing the same. I will explain in detail.

Since the center of rotation of the correction filter is the same as if it were stationary, the transmittance would be 0 if there was a light shielding part. However, since it is sufficient to obtain the light amount distribution on the surface of the phosphor photosensitive layer 2, and there is a sufficient distance between the correction filter and the face panel 1, a large number of dot-shaped light shielding parts are provided to block the light beam. By utilizing the effects of shadows and penumbra, it is possible to guide light even to the position directly behind the light shielding part. FIG. 4 shows the correction filter 1 of this embodiment.
2 is shown. This correction filter 12 has a light shielding portion formed by a large number of small square light shielding dots 13. The above-mentioned dot-shaped light-shielding part may be a dot-shaped light-transmitting part, and its shape can be changed in various ways, and these will be described later as other embodiments.

The exposure state using the correction filter 12 is
As shown in the figure. Considering the optical path reaching the surface of the phosphor photosensitive layer 2 regarding the two adjacent transparent parts a and b in the center of the correction filter 12, the part a' that does not become the penumbra of the respective transparent parts a and b , b' partially overlap, the transmittance can be controlled even in the center. The conditions at this time can be expressed by the size d and pitch p of the light-shielding dots 13 as follows: p<1/2 (d+h/L·C)...Formula 2. Here, L is the distance from the light source 4 to the phosphor photosensitive layer 2, h is the distance from the correction filter 12 to the phosphor photosensitive layer 2, and C is the size of the light source 4. The size C of this light source 4 is the size of the tip of a high-pressure mercury lamp when the light is guided by a colt, or the effective diameter of a rotating high-pressure mercury lamp with a slit, which is approximately 0.5~ 5.0mm
It is.

Using the size d and pitch p of the light shielding dot 13, the transmittance TMo of the central part of the correction filter 12 is calculated.
When calculated, TMo=(1- ^d2 / ^p2 )×100[%]...Equation 3 is obtained.

FIG. 6 shows a TMo diagram of (Equation 3). for example
To find the correction filter for a 20 inch 90° deflection color picture tube, L = 290 mm, H = 100 mm, C = 2.0 mm.
Then, (Equation 2) represents the left side of the straight line A-B in Figure 6, and in this range, the central transmittance TMo = 40%.
As an example, a point p (p=0.4 mm, d=0.31 mm) is obtained.

On the other hand, the transmittance TM at a distance of γ from the center is expressed as TM=100−ω(γ)/2πγ(100−TMo) [%]...Equation 4 based on the concept of (Formula 1). Even if the value of ω(γ) is determined, the shape 14 of the light shielding portion existing portion shown by the broken line as shown in FIG. 4 can be arbitrarily selected, but in general, it is easier to design a shape that is close to point symmetry.

Next, an embodiment of a method for manufacturing the correction filter 12 shown in FIG. 4 will be described in order of process.

First, a negative dot pattern 15 in which the shape of the light-shielding dots 13 is determined is formed. On the other hand, a negative grade pattern 16 in which the shape 14 of the light-shielding portion existing portion is determined is formed. Next, a positive pattern identical to that shown in FIG. 4 is formed from these two negative patterns 15 and 16 by a photographic method. A polyvinyl alcohol solution of ammonium dichromate is applied to a transparent glass substrate, and the positive pattern is closely exposed to light. The unexposed portions are developed and removed, and the dot-shaped exposed glass surface is etched with hydrofluoric acid to form recesses. Then, the correction filter 12 is obtained by filling this recess with a pigment or the like that does not transmit light.

In the embodiment described above, it is possible to combine several types of negative grade patterns 16 for one negative dot pattern 15. This is because when the transmittance TMo of the center part is the same but the size of the correction filter 12 is different, that is, when the size of the face panel 1 is different from 20 inches to 14 inches, or when the deflection angle is different, the shape of the light shielding part is different. This can be easily solved by simply changing the diameter of the negative grade pattern 16 that defines the grade pattern 14, which is very advantageous in the actual manufacturing process.

In addition, as shown in Figure 9, the central transmittance TMo
If you combine the dot pattern 15 that gives 40% with the negative grade pattern 16 where the transmittance is 0% at the point γ from the center, you will get a correction filter with the solid line transmittance curve 17. When a negative grade pattern 16 such that the transmittance is 20% at a point r from the center is combined with the dot pattern 15, a correction filter having a transmittance curve 18 indicated by a broken line is obtained. However, as long as the latter correction filter is used in the range from the center to γ, the effective transmittance curve 19 shown by the dashed dot line becomes the transmittance at the center.
A correction filter with TMo=50% is obtained. This is related to the ratio of the amount of light received by the phosphor photosensitive layer 2, so a correction filter with a center area of 40% and a peripheral area of 80% is substantially equivalent to a correction filter with a center area of 50% and a peripheral area of 100%. To become.

As described above, the correction filter 12 of this embodiment is
By forming a large number of small light shielding dots 13, it is possible to arbitrarily achieve the transmittance especially in the central part, and furthermore, the transmittance distribution curve to the peripheral part can also be arbitrarily obtained as the shape 14 of the light shielding part existing part. . This correction filter 12 does not change over time like conventional correction filters made of vapor-deposited metal thin films, and overcomes the drawbacks of poor reproducibility in the vapor deposition process and the inability to form large numbers of highly accurate filters. , mass production was possible with sufficient precision. This transmittance distribution was achieved with high precision because, as mentioned in the above manufacturing method, it is possible to combine the two components of the dot pattern 15 and the grade pattern 16.
Furthermore, a color picture tube of high quality and low cost can be obtained in that it can immediately respond to changes in the size of the color picture tube with the same degree of precision.

The correction filter 12 of the above embodiment has a light shielding dot 1.
Although the shape of No. 3 is a small square, since the present invention provides a large number of small light-shielding parts or light-transmitting parts, it can be formed into various shapes. Next, some other embodiments will be briefly described with reference to the drawings from FIG. 10 onwards.

FIG. 10 shows the correction filter 21 when the shape of the light-shielding dot 20 is a small circle, and the central transmittance corresponding to the above (formula 3) is: becomes. However, d is the diameter of the light-shielding dot 20, and p is its pitch. Transmittance at distance γ from center
TM〓 is given by (Equation 4).

The correction filter 22 shown in FIG. 11 has a checkered light-shielding portion 23, and the light-transmitting portion has a square dot shape. If one side of this light-transmitting part is d' and the pitch is p, the transmittance at the center is TMo=d' ² /p ² ×100 [%] . . . Equation 6.

The correction filter 24 shown in FIG. 12 has circular light-shielding dots of the same diameter arranged densely (pitch p) in the center and increasing in pitch toward the periphery.
The transmittance at the center is the same as (Equation 5), and the change in pitch can be determined according to (Equation 4).

In the correction filter 25 shown in FIG. 13, the pitch of the light-shielding dots is uniform, and the size of the light-shielding dots becomes smaller toward the periphery. In this case as well, it can be easily determined from (Equation 5) and (Equation 4).

Although the above explanation has been given by taking as an example the correction filter used in the manufacture of color picture tubes, it is possible to realize the present invention by using an optical filter that particularly limits the amount of light, and a sufficient effect can be achieved.

As described in detail above, according to the present invention,
An optical filter that rotates between a light source and a surface to be exposed has a large number of spot-like or lattice-like light-shielding parts on the surface of its transparent substrate, and the width of the light-shielding part at the center of the optical filter is and pitch are respectively d,
p, the distance from the light source to the exposed surface is L,
When the distance from the optical filter to the exposed surface is h, and the diameter of the light source is C, p<(1/2)
The structure is configured so that the relationship (d+h/L・C) is established, and the effective exposure amount at the center of the exposed surface is set to a predetermined value by utilizing the effects of the true shadow and penumbra of light. This method is particularly effective when applied to the formation of fluorescent surfaces in color picture tubes.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the exposure state, FIG. 2 is a transmittance distribution curve diagram, FIG. 3 is a top view of a filter having a light shielding part, and FIG. 4 is a top view of an optical filter of an exposure apparatus in which the present invention is implemented. Figure 5 is a front view of the exposure state using the optical filter shown in Figure 4, and Figure 6 is a front view of the exposure state using the optical filter shown in Figure 4.
Figure 7 is a top view of the dot pattern, Figure 8 is a top view of the grade pattern, Figure 9 is a transmittance distribution curve diagram, and Figure 10 is a diagram of the relationship between the shape of the optical filter and the central transmittance. , Fig. 11, Fig. 12, Fig. 1
FIG. 3 is a top view showing another embodiment. 12... Correction filter, 13... Light shielding dot,
20... Light shielding dot, 21... Correction filter, 2
2...Correction filter, 23...Checkered light shielding part,
24, 25...Correction filter.

Claims (1)

[Scope of Claims] 1. An optical filter that rotates between a light source and a surface to be exposed has a large number of spot-like or lattice-like light-shielding parts on the plate surface of a transparent substrate, and the center of the optical filter Let d and p be the width and pitch of the light-shielding portion at the section, respectively, L be the distance from the light source to the exposed surface, h be the distance from the optical filter to the exposed surface, and C be the diameter of the light source. An exposure apparatus characterized in that the following relationship holds true: p<(1/2)(d+h/L・C).