| 摘要 |
PURPOSE:To easily obtain a heat resistant optical film high in optical isotropy with a simple equipment by heat treating a film made of a thermoplastic resin having glass transition point equal to a specific temp. or above, at a lower temp. than the glass transition point and making each of the double refractive index of the film, retardation value and its deviation equal to a specific value or below. CONSTITUTION:The film made of the thermoplastic resin having >=190 deg.C glass transition point is heat treated in the temp. range from a temp. at which the coefficient of linear expansion of the film starts to increase with the start of the microbrown movement of the molecule chain constituting the film to the lower temp. than the glass transition point. And the film is controlled to <=5X10<-5> in the double refractive index, <=15nm in the retardation value of the film and <=10% in the deviation without eliminating the flatness of the film. As a result, the film high in optical isotropy and useful as a transparent electrode substrate for flexible liquid crystal display element is obtained without using special equipment, tools or the like and without eliminating the flatness of the film. |
