H - Electricity – 01 – J
Patent
H - Electricity
01
J
316/12
H01J 9/233 (2006.01) C21D 9/48 (2006.01) H01J 9/14 (2006.01)
Patent
CA 1191193
PHN 9949 12 ABSTRACT: Method of manufacturing a colour selection elec- trode for a colour display tube in which patterns of aper- tures are etched in a comparatively hard steel foil by means of a photoetching process. Mask blanks are cut from the steel foil, each mask blank having a pattern of aper- tures. In order to soften the mask blank in behalf of the subsequent deep drawing the mask blanks are annealed in a furnace. In order to obtain a good magnetic screening by the shadow mask a grain size of the mask material between 0.015 and 0.040 mm with an average grain size between 0.020 and 0.030 mm is necessary. In order to obtain this grain size the mask blanks must be annealed at a tempera- ture from 600°C to 850°C which lies above the temperature at which the mask blanks may adhere together by thermo- molecular welding. In order to prevent rejects as a result of this welding, a stack of mask blanks is laid on a curved substrate prior to annealing, which substrate preferably has the form of a part of a cylinder the radius of which is equal to the radius of the mask after deep drawing. After annealing in a furnace the mask blanks are placed on a flat substratum in which the thermomolecular wells present are interrupted without damaging the mask blanks. By annealing on the substrate the mask blank engages substantially the mould during deep drawing so that no deformations of the mask blank occur during the deep drawing process. .
396077
Koninklijke Philips Electronics N.v.
Van Steinburg C.e.
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