| 摘要 |
PURPOSE:To raise contrast performance and quality by increasing gradually light permeability from the center of face plate to its peripheral part for a fluorescent screen structure provided with such an opening that the opening ratio is smaller gradually from the center of face plate toward its peripheral part. CONSTITUTION:A face plate is designed to have such a light permeability that it is approx. 60% at the central part, gradually increased toward peripheral part, and approx. 85% at the peripheral part; that is, the light permeability is in the relationship 1.1<=TPE/TPC<=2.0, where TPC is the light permeability of the central part of face plate and TPE is the light permeability of the face plate, corresponding to a point farthest away from the central part of the face plate within effective picture during the working time of color Braun tube. Thus, contrast can be improved and also light output difference between the central part and peripheral part of face plate and blackly appearance at the peripheral part during the nonworking time of Braun tube can be eliminated. |
