Patent GB-692888-A (GB)
Title: Improvements in or relating to the production of patterned films
Inventor: FLANAGAN WILLIAM FRANCIS
IPC: B29C48/13
Filed: 1951-01-02
Abstract: <PICT:0692888/IV (a)/1> <PICT:0692888/IV (a)/2> A plastic film having wrinkled and smooth areas arranged in a pattern is obtained by applying a solution of one or more of the following resins or resin-like substances, viz. a vinyl acetate or chloride polymer or copolymer, a vinyl chloride-vinylidene chloride copolymer, chlorinated rubber, a styrene polymer or copolymer, cellulose acetate, cellulose acetopropionate, cellulose aceto-butyrate, methyl cellulose, vinyl butyrate polymer, polyethylene, butadiene copolymers, or a methyl methacrylate polymer, to a supporting surface and differentially heating different areas of the deposited layer of solution to a stage where one group only of these areas is covered with a soft skin, and then applying water to the film.  Wrinkles are formed in the areas which have reached the soft skin stage of setting when the water is applied.  The water treatment may be applied when the film is still substantially fluid in the other areas or it may be applied at a later stage when the more rapidly-heated areas have passed through the soft-skin stage and have become substantially fully set and when the more slowly heated areas have just reached the soft-skin stage.  Differential heating may be effected by supporting the film-layer on a material having areas of different specific heats, e.g. on a metal plate or band in which areas have been cut out and the spaces filled with material of low thermal conductivity, or on a glass plate, or paper, or fabric belt supported on a metal plate or band in which areas have been cut out.  A stainless steel belt in which holes have been cut out and filled with asbestos, or a paper sheet which has been printed with metal in the desired pattern, may be used.  In an example, the film-forming solution comprises vinyl chloridevinyl acetate copolymer, butyl acetate, methyl ethyl ketone, cyclohexanone and diethylhexyl phthalate.  As shown in Fig. 1, a glass plate 12 rests on a metal plate 11 in which are holes 13.  A film-forming solution is applied to the glass plate to form a film 14 from which solvent is evaporated by heat from infra-red lamps 15. Since plate 11 has a different heat conductivity from that of air, the areas of the film located over the metal become heated faster than those over the holes.  When a skin has formed in the background areas of the film but not in the pattern, the film is taken off frame 10 and immersed in water so that wrinkles develop only on the areas which had formed a skin.  If the heating of the film is continued till the skin and underlying areas have hardened and a skin has just formed on the more slowly heated areas, the subsequent treatment with water produces wrinkles only in the latter areas.  As shown in Fig. 2, an endless flexible belt 16, e.g. of fabric or paper, is disposed over an inner belt 17 which is constructed for differential heating. Belt 17 has cut-outs arranged in the form of the pattern desired in the film. Film-forming solution from container 31 is applied to the belt by spout 33 and is spread by knife 34.  Infra-red lamps 36 heat the film until the skin has developed in the desired areas, the pattern of the cut-outs in belt 17 being reproduced in the film. The heated film then enters container 37 and is immersed in water 38 containing a wetting agent.  The film passes to container 39 where it is rinsed by water 40 and is prepared for peeling by immersion in trisodium phosphate solution contained in vessel 41. The film 44 is detached from the belt 16 and wound on spool 43. If desired, the supporting layer for the film may be of wood, ceramic material or plastic material.  Dyes, pigments, plasticizers and other substances may be incorporated in the film-forming solution.