| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a polyimide film with biaxial optical anisotropy and excellent in durability. <P>SOLUTION: A solution of a polyimide with an imidization ratio of 98-100% is applied on a plastic base material and the solution is dried to form a polyimide film. The polyimide film is stretched together with the plastic base material so that the film has a state of nx>ny>nz, wherein nx denotes the refractive index in the direction where a refractive index is the largest within a plane, ny denotes the refractive index in the direction perpendicular to the direction of nx within the plane, and nz is the refractive index in the direction of thickness. The polyimide is preferably a fluorine-based polyimide since it is excellent in light transmittance and solubility, and preferably has a weight average molecular weight of 50,000-180,000. In addition, the polyimide solution preferably comprises a solvent with a solubility parameter in the range of 17-22 at a measurement condition of an atmospheric pressure of 1 atm and an atmospheric temperature of 25°C. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
