Abstract A photographic method of forming light-absorbing stripes on a color cathode ray tube screen between light-emitting phosphor stripes by an optical shadowing technique in which the lightabsorbing stripes are wider than the opaque parts of the shadow mask used to create the optical image. In order to create wider shadows, one set of exposures of the photosensitized screen is made from one set of positions of the light sources, and photographic and deposition steps are carried out to produce a first set of light-absorbing stripes. One edge of each stripe is in the desired location. The exposure process is repeated with the light sources slightly displaced so that, upon further development and deposition steps, a second set of light-absorbing stripes is produced that overlaps the first set so that the width of each stripe is correct and both edges are properly located. The space for light emission between adjacent stripes is therefore narrower than the beams that can strike these stripes by passing through the openings in the shadow mask.
The method of claim 1 in which said second exposure causes said different striped areas to overlap said first stripes of light-absorbing material, whereby the total width of stripes of light-absorbing material following the step of removing the remaining exposed photo-resist material is greater than the width of shadows of said opaque strips of said shadow mask.
Claim 2
Dependent Claim
72 words
The method of claim 1 in which said radiation is directed through said slots along three angularly separate sets of paths to strike three sets of striplike areas of equal width and equal spacing, and the central one of said sets of paths is substantially, but not precisely, perpendicular to said surface at the center thereof, whereby each of said first stripes is displaced laterally in one direction less than its width.
Claim 3
Dependent Claim
33 words
The method of claim 3 in which said different set of angles causes each of said different striped areas to be displaced laterally in the opposite direction a distance less than its width.
Claim 4
Dependent Claim
22 words
The method of claim 4 in which said different set of angles is equal and opposite to said first set of angles.
Claim 5
Dependent Claim
34 words
The method of claim 1 in which radiation for said first exposure reaches said surface along two sets of paths and at least partially overlaps at a first set of locations on said surface.
Claim 6
Dependent Claim
129 words
The method of claim 6 in which radiation for said second exposure reaches said surface along two different sets of paths and overlaps at a second set of locations on said surface, and said method comprises the additional steps of: A. coating said surface a third time with photo-resist material and making a third exposure thereof by radiation along a third pair of sets of paths to overlap at a third set of locations of said surface and leave a third set of striped areas in the shadow; B. removing those portions of said last-named coating in shadow; C. applying a layer of light-absorbing material to those portions of said surface from which the last-named coating has been removed; and D. removing the remaining portions of said last-named material.