Method of producing thermoplastic polycarbonate films having low optical retardation values
US6913714B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Nov 21, 2002 |
| Grant date | Jul 5, 2005 |
| Priority date | — |
| Expiry date | Nov 5, 2023 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29K2995/0032
- WIPO fieldOther special machines
- WIPO sectorMechanical engineering
Abstract
A method of preparing a thermoplastic polycarbonate film having an optical retardation value of less than or equal to 20 nm, is described. The method includes: (a) forming a molten extrudate (20) of a thermoplastic polycarbonate polymer in an extruder (11) having a terminal die (17) through which the molten extrudate is passed, the molten extrudate having a temperature of 150° C. to 400° C. upon emerging from terminal die (17); and (b) passing molten extrudate (20), from die (17), between two counter-rotating rolls (23 and 26) each having an elastomeric polymer surface (35 and 38), the counter-rotating rolls having a roll speed ratio and a nip (41), the distance between the terminal die (17) and the nip (41) being a die-nip distance (47). The extrudate temperature, the roll speed ratio and the die-nip distance (47) are each selected such that a thermoplastic polycarbonate film (32) having an optical retardation value of less than or equal to 20 nm is formed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.