Abstract: A method of forming apertures in a thin metal tape. Cavities having a depth of at least half of the tape thickness are first etched from one side. Etching is then carried out mainly from the other side until apertures having the desired profile have been formed. During etching the first-mentioned side, the said other side is covered with a foil of synthetic resin. Shadow mask for a color television display tube manufactured according to a similar method.

Abstract: Method of manufacturing a display screen for a shadow mask tube by projecting a negative image of the shadow mask on support provided with a first photosensitive layer, removing the unexposed regions by means of a solvent, depositing a second photosensitive layer containing a luminescent material of one color dissolved in a solution which becomes insoluble by exposure but is not attacked by an etchant which affects the first layer, exposing the second layer, and removing the exposed regions of the first layer together with superposed portions of the second layer, by the etchant.

Abstract: A method of manufacturing a luminescent screen of a shadow mask color tube. The phosphor dots on the screen which are separated by a light-absorbing material are smaller than the apertures in the shadow mask. The light-absorbing layer is first provided on the window and the luminescent materials are then provided successively. The inner surface of the window is such that undulations having a spatial frequency from 5 to 50 cm.sup.-.sup.1 or, in other words, wavelengths between 0.2 cm and 0.02 cm, show a depth of less than 1 micron.

Abstract: In the manufacture of screens for cathode-ray tubes, a substantial part of the screens being covered with a non-reflecting substance, hardened polyvinyl alcohol dots of relatively small diameter should be obtained by exposure via a mask with relatively large holes. Owing to an inadequate gradient of the photosensitive polyvinyl alcohol it is not possible to obtain dots of uniform size. The invention enables well-defined, uniform dots to be obtained by superposing a substance on the photosensitive layer which absorbs the light used during exposure, thereby decomposing into substances which do not or not substantially absorb this light. Thus, the effective gradient of the photosensitive polyvinyl alcohol is increased.