| 摘要 |
PURPOSE: To obtain a double refractive film which is improved in angle of visibility characteristic by forming the film of a polyacrylate and/or polysulfone soln. by casting and incorporating a specific solvent at a specific ratio into the raw film, then stretching the film. CONSTITUTION: The film of the polyacrylate and/or polysulfone soln. is formed by casting and at least one kind of the solvents selected from the group consisting of tetrahydrofuran and arom. hydrocarbon are incorporated at 3 to 40wt.% to solid content into the raw film and thereafter, the film is stretched. More preferably, the solvent is incorporated at 10 to 30wt.% therein. The solvent of the arom. hydrocarbon preferably consists of xylene and/or toluene. While toluene, xylene and tetrahydrofuran are usable as the solvent for preparing the casting solvent (dope), it takes time for drying and, therefore, the methylene chloride, etc., having a low b.p. are more preferable. The method for adjusting the solvent content includes a method of previously adding a solvent into a dope and adjusting the drying conditions at the time of film formation by casting, a method of exposing the dried original film to the solvent (liquid or vapor) and adjusting the content. |
