Virtual mask exposure system for CRT screen manufacture

• US 4,223,083 A
• Filed: 12/27/1977
• Issued: 09/16/1980
• Est. Priority Date: 12/27/1977
• Status: Expired due to Term

• Current Assignee: Tektronix Incorporated (Fortive Corp.)
• Original Assignee: Tektronix Incorporated (Fortive Corp.)
• Inventors: Engstrom, Frederic R.
• Primary Examiner(s): Kimlin, Edward C.
• Application Number:
  US05/864,949
• Time in Patent Office: 994 Days
• Field of Search: 96/44, 96/5, 96/36.1, 96/116, 96/33, 96/27 R, 427/64, 427/68, 354/1
• US Class Current: 430/24
• CPC Class Codes: H01J 9/2276 Development of latent electrostatic images per se G03G15/06

Abstract

An improved method of screening a color cathode ray tube of the shadow mask type is disclosed. The shadow mask is used to form a corresponding virtual mask on the outer or viewing surface of the CRT faceplate. The virtual mask then is employed as a substitute for the shadow mask in the subsequent photoprinting of a color display screen on the faceplates'"'"'s inner surface. Advantages include reduced handling of the fragile shadow mask, which reduces the costs associated with replacing such masks if they become damaged, and better defined and registered phosphor deposits.

Claims

1. In the manufacture of an image display screen for a shadow mask cathode ray tube, said screen including a pattern of photodeposited elements on one face of a transparent support, the method of depositing said elements that includes the steps of:

(1) forming a replica of a cathode ray tube shadow mask on the opposite face of the support, wherein said replica is formed by steps including;

(a) applying a layer of a photosensitive material to said opposite face, (b) mounting said shadow mask adjacent said one face, (c) exposing said photosensitive layer to actinic radiation transmitted through the apertures of said mask to form in said layer a developable latent image of said mask, and (d) treating the exposed photosensitive layer to develop said image,

(2) applying a layer of photosensitive material to said one face, and

(3) exposing said layer to a pattern of actinic radiation transmitted through said mask replica and support.

2. In the manufacture of a cathode ray tube that includes a color display screen comprising an array of phosphor elements disposed on one face of a transparent support, and an apertured shadow mask in spaced opposition to said screen, the method of laying down said array on said support comprising the steps of:

(1) forming a replica of said shadow mask on the opposite face of said support, wherein said replica is formed by steps including;

(a) applying a layer of a photosensitive material to said opposite face of the support, (b) mounting said shadow mask in spaced opposition to the support'"'"'s said one face, (c) projecting actinic radiation from a source thereof through the apertures of said shadow mask and said support to expose portions of said layer and form therein a developable latent image of said mask, (d) disassociating said shadow mask from said support, and (e) treating the exposed photosensitive layer to develop said image,

(2) applying a layer of a photosensitive material to said one face,

(3) exposing said photosensitive layer to a pattern of actinic radiation transmitted through said replica and support, and

(4) developing the exposed layer to produce a pattern of deposits on said one face corresponding to the desired array of phosphor elements.

3. The method of claim 2 including the subsequential step of removing said replica.

4. A method of making an image display screen for a cathode ray tube of the type wherein said screen comprises an array of phosphor elements disposed on the inner surface of the tube'"'"'s faceplate, and wherein an apertured shadow mask is mounted within said tube in spaced relation to said screen, including:

applying a layer of photosensitive material to the outer surface of said faceplate,

mounting an apertured shadow mask in spaced relation to the faceplate'"'"'s inner surface,

directing actinic radiation from a source thereof through the shadow mask apertures and faceplate to expose portions of said layer and form a developable image of said shadow mask therein,

developing said image,

treating the developed image to form on said outer surface a replica of the shadow mask, and

photoprinting an array of phosphor elements on the inner surface of the faceplate by steps that include directing actinic radiation from a source thereof through said replica toward said inner surface.

5. The method of claim 4, including the subsequent step of stripping said mask replica from said faceplate.

6. The method of claim 4, wherein said display screen comprises a regular pattern of phosphor deposits arranged in multicolor groupings, and said shadow mask includes an array of apertures correlated to said pattern, with one such aperture for each grouping.

7. The method of claim 5, wherein said display screen comprises a multiplicity of phosphor dots arranged in multicolor triads.