GB697036A - Photographic copying process - Google Patents

Abstract

697,036. Photographic copying processes. HEIDENHAIN,J. April 3,1951,No. 7748/51. Drawings to Specification. Class 98 (ii). [Also in Group XV] A process for the production of images, characters, measurement graduations, or the like on supports as of glass, metal, and plastics, by the photographic reproduction of an original, is characterized in that a light-sensitive layer capable of being washed out by developing is applied to the support, exposed imagewise by contact or projection by means of the original, and then parts are washed out; image-forming substances are deposited by vaporization on the support and on the exposed parts of the lightsensitive layer; and said exposed parts are thereafter removed together with the substances deposited thereon, so that the deposited substances remain only on the unexposed parts, corresponding in form to the original. The light-sensitive layer with which the support is coated may consist of bichromated albumen, shellac, or the like, and after exposure the unhardened parts are washed away, leaving the support bare. The substance deposited by vaporization on the support and the remaining parts of the layer may be a metal such as chromium, silver, or copper; a salt such as magnesium fluoride or another fluoride; other inorganic compounds such as silicon monoxide or dioxide, or an organic substance. Vaporization may be carried out in vacuum, and different substances may be deposited simultaneously or in succession; e.g. first chromium and then silicon monoxide. The remaining light-hardened layer is then removed as by a solvent, together with the deposit thereon, leaving the deposit only on those parts which were exposed to light. If the light-sensitive layer is bichromated shellac and the substance deposited is chromium, the chromium is treated with nitric acid to render it resistant to the action of caustic soda, and the light-hardened shellac is removed with a weak solution of caustic soda in methylated spirit. If desired, a second substance may be deposited by vaporization on the support and the remaining deposited substance; further, the first substance may be dissolved away, leaving the second substance only on those parts of the support not previously covered by the first substance. The first deposit could, e.g. be formed of silver, and the second substance could be chromium; in this case the silver would be dissolved by nitric acid.