Abstract: The invention provides a lamp screw cap (200) comprising a thread structure (220), wherein the thread structure (220) comprises repetitive elements (225) defining tops (230), valleys (240), and a central plane (250), wherein tops (230) protrude relative to the central plane (250) and wherein the valleys (240) are recessed relative to the central plane (250), wherein: for a plurality of tops (230) applies that each top (230) comprises a first top segment (231), a second top segment (232), and a middle top segment (233), together defining the top (230), wherein the middle top segment (233) is configured most remote from the central plane (250); for a plurality of valleys (240) applies that each valley (240) comprises a first valley segment (241), a second valley segment (242), and a middle valley segment (243), together defining the valley (240), wherein the middle valley segment (243) is configured most remote from the central plane (250); the first top segment (231), the second top segment (232), the first va

Abstract: A screen for a color display tube or display window has a structure of apertures in a black matrix and electro-luminescent material in the apertures. Steps in producing the screen include applying the black matrix and the electro-luminescent material, and exposing photosensitive material on the display window to light emitted by a light source and passed through a lens system and a shadow mask. The shadow mask is suspended from the display window and the lens system is positioned between the light source and the shadow mask. On the screen, the lens system realizes a microscopic light distribution of the light originating from the light source radiating towards the screen. The photosensitive material includes a bleaching dye functioning as a contrast enhancer in at least one of the process steps.

Abstract: In the manufacturing process of a screen (6), for use in a color display tube (1), a photosensitive process step, referred to as the exposure process, is used for applying the black matrix pattern and the phosphor layers to the display window (3) to form the screen (6). The robustness of this exposure process is dependent on, amongst others, the shape of the microscopic light distribution on the display window (3). It appears that in color display tubes (1) with an increased deflection angle, or in tubes with a real flat outer surface, the exposure process becomes more and more critical. According to the invention, this problem can be overcome by adding a bleaching dye to the photosensitive material used for the exposure process. This bleaching dye's action in the center of the microscopic light distribution is stronger than in the peripheral portions.

Abstract: In a colour display tube (1), the shadow mask (13) serves as the colour selective element. The major part of the electrons emitted by the electron gun (10) are intercepted by the shadow mask (13). These electrons can be absorbed by the shadow mask (13) or they can be reflected. In the first situation, where the electrons are absorbed, the shadow mask (13) is heated as a result of which it will be deformed, leading to misregistration of the electron beams (7, 8, 9) when they impinge upon the phosphor screen (6), causing colour impurities on the colour display tube (1). This phenomenon is commonly referred to as doming. In the second situation, where the electrons are reflected, degradation of the contrast performance takes place because the reflected electrons hit the phosphor screen (6) at totally different positions, leading to the generation of stray light. Both doming and contrast performance are important for the quality of a colour display tube (1).