US3840881A

US3840881A - Light exposure apparatus for formation of striped phosphor screens of color picture tubes

Info

Publication number: US3840881A
Application number: US00330116A
Authority: US
Inventors: K Koizumi; F Yonai; M Yamauchi; Y Utamura
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 1972-02-07
Filing date: 1973-02-06
Publication date: 1974-10-08
Anticipated expiration: 1991-10-08
Also published as: CA981089A; FR2171189A1; IT977700B; GB1421983A; JPS4883775A; FR2171189B1; DE2305747A1

Abstract

A light exposure apparatus for formation of striped phosphor screens of color picture tubes wherein use is made of a light source assembly substantially serving as a linear light source.

Description

United States Patent Koizumi et a1.

[ Oct. 8, 1974 LIGHT EXPOSURE APPARATUS FOR FORMATION OF STRIPED PHOSPHOR SCREENS OF COLOR PICTURE TUBES [75] Inventors: Kihachiro Koizumi, Chiba; F umiaki Yonai, Mobara; Masaaki Yamauchi, Mobara; Yukihiko Utamura,

Mobara, all of Japan [73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Feb. 6, 1973 [21] Appl. No.: 330,116

[30] Foreign Application Priority Data Feb. 7, 1972 Japan 47-12875 [52] US. Cl. 354/1, 313/92 B [51] Int. Cl. G03b 27/00 [58] Field of Search 95/1 R; 313/92 B [56] References Cited UNITED STATES PATENTS 3,587,417 6/1971 Balder et a1 95/1 R 3,633,058 1/1972 Kouno 313/92 B 3,652,895 3/1972 Tsuneta et al 313/92 B X 3,735,677 5/1973 Jones et al. 313/92 B X Primary Examiner-Richard M. Sheen Attorney, Agent, or Firm-Craig and Antonelli [57] ABSTRACT A light exposure apparatus for formation of striped I phosphor screens of color picture tubes wherein use is made of a light source assembly substantially serving as a linear light source.

8 Claims, 14 Drawing Figures PATENTED 81975 3,840,881

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I FORMATION OF STRIPED PHOSPHOR SCREENS OF COLOR-PICTURE TUBES trodes.

Generally, a light exposure apparatus used for forming phosphor screens of panel portions of color picture tubes-comprises a light source assembly, a correction lens for causing paths of light beams from the light source assembly to approximate paths of electron beams from the electron gun and a base for supporting the panel portion in a predetermined positional relation.

Heretofore, a light source assembly included a collimator having such a construction that the light source assembly as viewed from the panel portion of a color picture tube operates as a point light source, this collimator being used to condense light emitted from a light emitter in cooperation with a reflector. With such a light source assembly, much time has been consumed v in carrying out each light exposure operation for fonning a phosphor screen on the inner surface of the panel portion through a striped color selective electrode in which many slits are formed. An attempt to make the diameter of the point light source larger to increase the amount of light emitted from the light source assembly in an effort to lessen the light exposure time resulted in that the developed phosphor stripes had a width greater than a predetermined one and tended to overlap with adjacent phosphor stripes, thus bringing about a mixture of colors in the resultant phosphor screen. Further,

'with such a light source assembly, it might be possible,

depending upon the shape and/or arrangement of slits formed in a used striped color selective electrode, that each developed phosphor stripe is not continuous, which leads to decrease the quality, particularly, the

efficiency of energy conversion by the resultant phosphor screen;

The primary object of the present invention is to provide an improved light exposure apparatus for forming striped color phosphor screen, free from the abovementioned drawbacks.

In accordance with the present invention, there is provided a light exposure apparatus for formation of striped phosphor screens of panel portions of color picture tubes comprising: a light source assembly including a light emitter, a reflector and a collimating means; a base for supporting the panel portion as well as a striped color selective electrode in a positional relation, the color selective electrode having slits formed therein; and a correction lens for causing paths of light from said light source assembly to approximate paths of electron beams in the color picture tube, the collimating means having its leading portion from which light is to be emitted towards the panel portion through the correction lens; wherein the leading portion of the collimating means is substantially in a linear form as viewedfrom the panel portion so that the light source assembly serves as a linear light source, and wherein the length of the linear leading portion is in the direction of the length of the slits in the striped color selective electrode.

Since, in the presentinvention, a light source assembly includes a collimating means having a substantially linear leading portion from which light is to be emitted, and the length of the linear leading portion is in the direction of slits in a used striped color selective electrode, the amount of light emitted per unit time is increased and therefore less exposure time is needed. Further, in the present invention, due to the linear light source, use may be made, to form continuous phosphor stripes, of a mechanically strengthened striped color selective electrode having such slits formed therein that each of them is divided into a plurality of slit divisions, thus each slit being bridged. As a result, the present invention offers a light exposure apparatus useful for forming a striped phosphor screen of a color picture tube on which images are reproduced with a high purity and a sufficient brightness.

The invention will be more readily understood from the following detailed description illustrated by the ac companying drawings, in which:

FIG. 1 is a diagrammatic view of a light exposure apparatus employed in forming a phosphor screen of a color picture tube;

FIGS. 2a and 2b are enlarged partial views of examples of striped color selective electrode;

FIGS. 30 and 3b are elevational and sectional views of a collimator of a light source assembly and its associated members of a conventional light exposure apparatus;

FIG. 4 is an enlarged partial view of an example of a striped phosphor screen;

FIG. 5a is an elevational view of a collimator of a light source assembly and its associated members used.

in an embodiment of the present invention;

FIGS. 5b and 5c are sectional views taken along lines Sb-Sb and Sc-Sc of FIG. 5a;

FIG. 6 is an enlarged partial view of an example of a striped phosphor screen formed by using a light exposure apparatus of the present invention; and

FIGS. 7a, 7b, 8a and 8b are elevational and sectional views of other examples of collimators and their associated members in other embodiments of the present invention, the sectional views being taken along lines 7b-7b and 8b 8b respectively.

FIG. 1 shows a light exposure apparatus generally employed in forming a phosphor screen of acolor picture tube which includes such a color selective electrode as a shadow mask. Reference numeral 1 designates a light source assembly. A correction lens 3 is provided for causing paths of light 2 from the light source assembly 1 to approximate paths of electron beams. A base 5 is for supporting a panel portion 4 as well as a color selective electrode 11 of a color picture tube in a predetermined positional relation. The light source assembly 1 includes a light emitter 6 consisting of, for example, a high voltage mercury-arc lamp, a reflector 7, a collimator Sand a casing 9. Light emitted from the emitter 1 either directly enters or is reflected at the reflector 7 to enter the collimator 8 and is condensed therein to emanate from a leading portion 10of the collimator 8 towards the panel portion 4, thus spreading uniformly over the color selective electrode 11 with the leading portion 10 serving as a point light source. The color selective electrode 11 is positioned adjacent-to the panel portion 11 on its inner side so that a phosphor material applied for each color by means of, for example, the slurry method, to the inner surface of the panel portion 4 is exposed to light emitted from the light source assembly 1 and passed through the correction lens 3 and the color selective electrode 11 to the applied phosphor material.

Examples of currently used striped color selective electrodes are shown in FIGS. 2a and 2b in enlarged views. These striped color selective electrodes are used to form striped phosphor screens of color picture tubes. In FIG. 2a, the color selective electrode is provided with a plurality of continuous slits 12 arranged in parallel with one another at a spacing of about 0.6 mm, the width of the slits being about 0.1 0.12 mm. Thus, the electrode being provided with many slits at such a small spacing is not strong enough to be shaped in a form other than flat or cylindrical. Meanwhile, in FIG. 2b, each of the slits similar to those of FIG. 2a is separated by bridges 13 into slit divisions 12a. The color selective electrode of FIG. 2b is thus mechanically strengthened. The arrangement of the bridges 13 may be such that they are about 0.06 0.12 mm long (i.e., wide) and spaced about 0.6 0.8 mm from the adjacent ones in the direction of the length of the slit divisions 12a and that the bridges 13 in the slits stagger the slit divisions 12a.

As has been briefly set forth above, a light source assembly used heretofore in a conventional light exposure apparatus serves as a point light source. An example of a construction of the essential part of a prior art light source assembly is shown in FIGS. 3a and 3b, in which at one end face of a collimator casing 9a a small opening 14 is formed and the leading portion of a collimator 8 placed within the casing 9a is exposed through the small opening 14. As is known, the amount of light emitted from the light source assembly is proportional to the apparent area of the leading portion 10 as viewed from the panel portion (not shown). For example, with a light source assembly serving as a point light source having a diameter of 1.5 mm, i.e., when the diameter of the leading portion 10 is 1.5 mm, it usually requires about 30 40 minutes to carry out an operation of exposing each kind of applied phosphor material to light from the light source assembly to form a complete phosphor screen on the inner surface of the panel portion of a 14 inch-color picture tube. If the diameter of the leading portion of the collimator is increased to a larger one, the developed phosphor stripes have a width larger than is intended to be obtained with a result that they are overlapped with adjacent ones to cause mixture of colors. In the above-mentioned example, the color selective electrode used is such as shown in FIG. 2a. If an improved color selective electrode such as shown in FIG. 2b is used together with the above-mentioned conventional light source assembly, the resulting phosphor stripes must be such as shown in FIG. 4 in which three kinds i.e., red(R), green (G) and blue(B) phosphor stripes 15 are interrupted by discontinuities 16, which leads to a decrease of the color purity and brightness of reproduced images on the resulting phosphor screen.

Reference will now be made to some embodiments of the present invention, removing such inconveniences as have been mentioned above.

FIGS. 5a-5c show a collimator means and its associated members in elevational and sectional views, which constitute a light source assembly used in a light exposure apparatus embodying the present invention. A collimator 17 has a slender leading portion 18 protruding from an opening 20 formed also in a slender shape at an end face of a collimator casing 19. This collimator means makes the total light source assembly including the collimator means operate as a linear light source in contrast with the conventional point light source. Clearly, the direction D of the length of the slender leading portion 18, i.e., of the linear light source assembly should be concurrent with the direction of the length of slits in a used striped color selective electrode, i.e., of phosphor stripes to be formed. Due to the slender or linear light source assembly, the amount of light emitted per unit time is increased, thereby shortening the time required for completing a light exposure operation. As is well known, the positional relation of the slender or linear leading portion 18 of the light source assembly with respect to the panel portion and to the striped color selective electrode must be changed for each color in order to complete a striped phosphor screen as shown in FIG. 6 in an enlarged view. Further, even though use is made of such a mechanically strengthened striped color selective electrode as shown in FIG. 2b, the linear light source assembly of the present invention makes it possible to form a striped phosphor screen 21 consisting of three kinds of, i.e., red (R), g een (G) and blue (B), continuous phosphor stripes as shown in FIG. 6.

It was proved that a linear light source assembly including a collimator means which has its slender leading portion having a size 1.5 mm X 6 mm required 3-5 minutes for carrying out an operation of exposing each kind of applied phosphor material to light from the light source assembly to form a complete phosphor screen of a 14 inch-color picture tube. This means that the required light exposure time is reduced to one-sixth to one-tenth of the light exposure time when the conventional point light source having a diameter of 1.5 mm is used. This rate of reduction of the exposure time is higher as compared with the ratio between the apparent areas of the light source assemblies of the present invention and of the prior art. Thus, it can be understood that a collimator having a slender leading portion in accordance with the present invention suffers from less loss of light and is therefore more efficient than a conventional collimator.

Although in the above embodiment, the leading portion ofa collimator means, i.e., ofa light source assembly is in a slender form, the present invention is not limited thereto. The point is that the light exposure apparatus of the present invention includes a light source assembly having such a linear leading portion that the light source assembly, as a whole, serves as a substantially linear light source when viewed from the panel portion of a color picture tube.

FIGS. 7a and 7b show another example of the major part of the light source assembly in an embodiment of the present invention. Here, a single collimator 17a has a leading portion consisting of two slender leading ends 18a aligned or arranged on one line. The number of the aligned slender leading ends of the single collimator 17a may be more than two.

FIGS. 8a and 8b show another example similar to FIGS. 7a and 7b, in which two collimators 17b are provided within a casing, each of them having a leading end 18b which serves as a point light source. The line on which the two leading ends 18b lie is in the direction of the length of slits of a used striped color selective electrode, so that the light source assembly, as a whole, serves as a linear light source. Again in this example,

the number of the aligned leading ends 18b may be more than two.

Pereferable ranges of effective dimensions of the leading portion of the linear light source assembly are that the length is 8 40 mm and the width is 0.3 3.5 mm. It is clear that when such collimators as are shown in FIGS. 7a and 8a are used, the effective length of the leading portion is determined by the distance between the extremities of two opposite outermost leading ends and the effective width may be equal to the width or the diameter of the aligned leading ends.

What we claim is:

1. A light exposure apparatus for the formation of a striped phosphor screen on the panel portion of a color picture tube including a striped color selective electrode having a plurality of slits comprising:

a light source assembly including a light emitter, a reflector and a collimating member;

a base for supporting the panel portion of a color picture tube and the striped color selective electrode with the plurality of slits in a predetermined positional relationship with respect to said light source assembly; and correction lens disposed between said light source assembly and said base for causing paths of light from said light source assembly to approximate paths of electron beams in the color picture tube, said collimating member having a light emitting portion facing said base and said correction lens; said light emitting portion of said collimating member being shaped substantially in a linear form as viewed from said base so that said light source assembly serves as a linear light source, and being oriented such that the length of said linear light emitting portion is in the direction of the length of the slits in the striped color selective electrode.

2. The light exposure apparatus as defined in claim 1, wherein said collimating member is a single collimator.

3. The light exposure apparatus as defined in claim 2, wherein said single collimator has a plurality of light emitting portions which in combination form said linear light source.

4. The light exposure apparatus as defined in claim 1, wherein said collimating member is a plurality of collimators, each having a light emitting portion, the light emitting portions of said collimators as a whole forming said linear light source.

5. A light exposure apparatus for the formation of a striped phosphor screen for a color picture tube, comprising a mask having a plurality of aligned slits therein, light beam generating means facing said mask for projecting light through said aligned slits, and lens means disposed between said light beam generating means and said mask for causing the paths of light from said light beam generating means to approximate the paths of electron beams in a color picture tube, said light beam generating means including a light emitter and a collimating member having a light receiving portion disposed adjacent said light emitter and a light emitting portion facing said lens means and said mask, the light emitting portion of said collimating member having a plurality of light emitting points disposed along a common line so that said light beam generating means serves as a linear light source, said collimating member being oriented with said light emitting points disposed in alignment with the direction of the length of said slits in said mask.

6. A light exposure apparatus as defined in claim 5, wherein said light emitting portion of said collimating member is a continuous linear light emitting surface.

7. A light exposure apparatus as defined in claim 5,

wherein said light emitting portion of said collimating member comprises a pair of linear light emitting surfaces aligned along said common line.

8. A light exposure apparatus as defined in claim 5, wherein said light emitting portion of said collimating member comprises a pair of circular light emitting surfaces spaced along said common line.

Notice of Adverse Decision in Interference,

In Interference N 0. 99,342, involving Patent No. 3,840,881, K. Koizumi, F. Yonai, M. Yamauchi and Y. Utamura, LIGHT EXPOSURE APPARA- TUS F OR FORMATION OF STRIPED PHOSPHOR SCREENS OF COLOR PICTURE TUBES, final judgment adverse to the patentees was rendered Dec. 20, 1976, as to

claims

1, 2, 3, 5, 6 and 8.

[Oyficial Gazette Mamh 22, 1.977.]

Notice of Adverse Decision in Interference In Interference No. 99,342, involving Patent No. 3,840,881, K. Koizumi, F. Yonai, M. Yamauchi and Y. Utamum, LIGHT EXPOSURE APPARA- TUS F OR FORMATION OF STRIPED PHOSPHOR SCREENS OF COLOR PICTURE TUBES, final judgment adverse to the patentees was rendered Dec. 20, 1976, as to

claims

1, 2, 3, 5, 6 and 8.

[Oficial Gazette March 22, 1977.]

Claims

1. A light exposure apparatus for the formation of a striped phosphor screen on the panel portion of a color picture tube including a striped color selective electrode having a plurality of slits comprising: a light source assembly including a light emitter, a reflector and a collimating member; a base for supporting the panel portion of a color picture tube and the striped color selective elEctrode with the plurality of slits in a predetermined positional relationship with respect to said light source assembly; and a correction lens disposed between said light source assembly and said base for causing paths of light from said light source assembly to approximate paths of electron beams in the color picture tube, said collimating member having a light emitting portion facing said base and said correction lens; said light emitting portion of said collimating member being shaped substantially in a linear form as viewed from said base so that said light source assembly serves as a linear light source, and being oriented such that the length of said linear light emitting portion is in the direction of the length of the slits in the striped color selective electrode.

7. A light exposure apparatus as defined in claim 5, wherein said light emitting portion of said collimating member comprises a pair of linear light emitting surfaces aligned along said common line.