Reproduction d'un original transparent en demi-tons sous forme d'une image tramée

1,177,482. Production of screen images. GEVAERT-AGFA N.V. Dec.28, 1966 [Jan. 11, 1966], No. 1351/66. Heading G2M. Continuous tone transparencies are recorded by exposing to radiation (preferably visible or infrared) through the transparency and across line screen a water-permeable, heat-sensitive material which charges its water-permeability on heating and also containing a substance which absorbs the radiation and heats the layer on such absorption so that a latent screen dot image of the transparency is produced. The heat-sensitive materials preferred are those described in Specifications 1,139,894 and 1,139,892 which become less water-permeable on heating and those in Specification 1,154, 568 which become more waterpermeable on heating. In the examples, a support is coated with polyvinyl alcohol, gelatine or polyvinylpyrrolidone in which is dispersed polyethylene particles and carbon black or silver. This heatsensitive material is placed in contact with a magenta contact screen and a continuous tone transparency and flash exposed through the screen and transparency so that the areas correspondingtothebackground of the transparency are exposed and become less water-permeable. The latent image is developed either by washing out the more water-permeable areas or by bleaching the silver out of the areas to leave a negative screen image of the transparency. Positive screen images are produced by using a heat-sensitive material of gelatine with a high Bloom gel strength and colloidal silver as in Specification 1,154, 568.