| 摘要 |
1,240,697. Shrinkable polypropylene film. RICOH K.K. 14 Oct., 1968 [2 Nov., 1967; 11 Nov., 1967], No. 48516/68. Heading B5B. [Also in Division G2] An exposed diapositive film is made by selectively exposing a prestretched polypropylene film to heat radiation in accordance with a desired image whereby the exposed areas become wrinkled. The film may have a shrinkage after heating to 120‹ C. for 1 minute of less than 5% in the longitudinal and transverse directions, or less than 1% in one said direction and less than 15% in the other directions. As disclosed, film is placed in heat-conductive contact with a newspaper original print and is exposed to IR radiation. The shrinkable polypropylene film is made either by heat-treatment of commercial film under controlled shrinkage conditions or by extrusion and winding under conditions to produce a shrinkable film. In examples, films having shrinkabilities in the above ranges are so produced. |
