| 摘要 |
PURPOSE:To manufacture the titled sheet inexpensively, by covering thermoplastic resin A on both surfaces with thermoplastic resin B non-adhesive to the resin A, by extruding these resins together, and by separating then the layer of the resin B from the resin A. CONSTITUTION:Thermoplastic resin A (ex.: PVC, methacrylate resin, PS) is covered on both surfaces with thermoplastic resin B (ex.: low-density PE in the case when the resin A is hard PVC), and in this state, these resins are extruded together into a sheet. Thereafter the exterior thermoplastic resin B is separated from the resin A, and thereby a sheet virtually free from optical anisotropy can be obtained simply and inexpensively. The ratio of A to the total thickness of the sheet extruded together is preferably less than 90%, and when said ratio exceeds 90%, the optical anisotropy sometimes occurs undesirably. The above-stated sheet virtually free from the optical anisotropy is protected from the sticking of foreign particles etc. in the processes of production, conveyance, cutting, etc., since it is covered with the sheets of the resin B when manufactured, and thus it is advantageous, in particular, when it is used for a field of an optical recording material for an optical disc apparatus etc. which tends to be much impaired by foreign particles. |
