GB1458229A - Shadow-mask colour cathode ray tubes - Google Patents

Abstract

1458229 Colour television tubes RCA CORPORATION 28 Dec 1973 [29 Dec 1972] 60089/73 Heading HID In a colour cathode-ray tube with a phosphordot screen and a shadow mask, at least one side of the mask, and the inner surface of the screen, have heat reflecting and heat absorbing surface areas for transferring heat faster from the central portions of the mask than from its margins. "Doming", which arises because the mask is ordinarily heated more in the middle, is thus reduced. As shown, the tube 11 has a faceplate 15 and a funnel 13 which, in the neighbourhood of a magnetic shield 44, has a conducting coating 17. A screen 25 with a set of three-colour phosphor dots on the faceplate 15 carries a reflecting layer 31, which in turn carries, in its central part, an infra-red absorbing layer 33, (see also Fig. 3, not shown). An apertured shadow mask 35, closely spaced from screen 25, is mounted on a frame 43 which also carries shield 44, the assembly being spring-mounted on faceplate 15. Both sides of mask 35 are blackened, and an infra-red reflective layer 41 surrounding an infra-red absorbing layer 47 is deposited on the margins. (See also Fig. 2, not shown). The absorbing layers 33, 47 are about the same in shape and size. In operation, heat is radiated from the mask more in the centre and less at the margins, so that "doming" is minimized. In modifications, a reflecting layer may be deposited on the margin of the gun side of the mask 35, and if the magnetic shield is omitted, the conductive coating 17 is made of reflecting aluminium covered in central parts by an absorbing graphite layer. Other modifications of details are disclosed. Temperature changes are described and shown graphically.