| 摘要 |
PURPOSE:To enable a photomask with high acuracy to be easilyh obtained by trimming an opaque film formed on one surface of a curved light-transmitting plate by means of laser light so as to obtain a given mask pattern. CONSTITUTION:A curved light-transmitting plate 6 is formed which optically corresponds to the inner surface of spherical plate 2 of a picture tube. Next an opaque film 6 is formed on one surface of the curved light-transmittng plate 5 which faces the inner surface 2a of the face plate 2 during exposure. The opaque film 6 is homogeneously formed over the entire surface for example by vacuum- vapordepositioning a metal such as chromium, aluminum, copper or nickel. After that, the opaque film surface of the curved light-transmitting plate 5 is subjected to trimming by irradiating laser light 7 on the opaque film 6 while controlling a work table which can be triaxially driven in the same manner as when a given mask pattern is obtained by laser light. |
