COLOR TUBE HAVING SHADOW MASK WHOSE CENTER-TO-CENTER APERTURE SPACINGS INCREASE RADIALLY OUTWARD FROM MASK CENTER

摘要

1,165,766. Colour television tubes. THORNAEI RADIO VALVES & TUBES Ltd. 6 June, 1967, No. 26126/67. Heading H1D. In a colour cathode-ray tube employing a shadow mask, the spacing between the centres of the holes of the shadow mask, measured along the surface of the mask, in both the radial and circumferential directions, is greater at the edge of the mask than at the centre. The increase of spacing outwards from the centre of the mask is preferably such that the spacing is substantially uniform over any small area. The shadow mask may be spaced uniformly from the tube screen, on which substantially tangential circular phosphor dots are deposited which increase in size from the centre of the screen outwards. The size of the apertures in the shadow mask may also be varied. An optical method of producing a master negative of the shadow mask with the required hole spacing is described in which a spherical photo-sensitive surface is disposed outside but touching the centre of a smaller spherical mask having a uniform pattern of apertures therein and developing a pattern on the photosensitive surface using a source of light disposed between the centres of curvature of the mask and surface.