| 摘要 |
PURPOSE:To reduce doming of a shadow mask by forming a coated layer mainly composed of glass at least containing SnO2 having low conductivity on the main surface on the side of an electron gun of a shadow mask having a large number of punched transmitting holes. CONSTITUTION:A coated layer 14 mainly composed of lead borate glass containing SnO2 having low conductivity is applied by a spray method or the like on the main surface of the non-transmitting hole part 13 on the side of an electron gun 6 of a shadow mask 5, which is arranged close the and facing the screen 4 of a color picture tube and having a large number of punched transmitting holes 15, while being crystalized and formed by heat treatment. Accordingly, when a doming phenomenon is generated as the shadow mask 5 is heated by an electron beam, the coated layer 14 made of a low conductivity material is negatively electrified so as to deflect the electron beam 11 to 10a and cancel the doming phenomenon thus doing away with mislanding of the electron beam and preventing deterioration of color purity. |
