Abstract:
GLASS COMPOSITIONS CONSISTING ESSENTIALLY, BY WEIGHT, OF 57-62% SIO2, 2-3.5% AL2O3, 4-10% K2O, 5-11% NA2O, 10-16% BAO, 1-10% ZNO, 0.1-4% WO3, 0.2-0.6% CEO2, LESS THAN 5% CAO, LESS THAN 2% MGO AND LESS THAN 1% PBO, WHEREIN THE TOTAL OF THE AMOUNTS OF CAO, MGO AND BAO EXCEEDS 14% AND THE TOTAL OF THE AMOUNTS OF BAO, ZNO, WO3, AND PBO EXCEEDS 12%.
Abstract:
A D.C. voltage is applied between an anode terminal and stem pins of a cathode ray tube, using the anode terminal as a negative terminal to cause cathode spot at an edge of an internal electric conductive film of the cathode ray tube. Thus, the edge of the internal electric conductive film is so conditioned that the dielectric breakdown strength of a glass neck tube of the cathode ray tube is graded up.