Low birefringence, low stress film suitable for optical applications

• US 20030127770A1
• Filed: 12/04/2002
• Published: 07/10/2003
• Est. Priority Date: 12/27/2001
• Status: Abandoned Application

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Xi, Kang, Tadros, Safwat
• Application Number:
  US10/309,973
• Publication Number:
  US 20030127770A1
• Time in Patent Office: Days
• US Class Current: 264/175
• CPC Class Codes: B29C 48/0018 combined with shaping by orienting, stretching or shrinking, e.g. film blowing B29C48/0017 takes precedence
• CPC Class Codes: B29C 48/022 characterised by the choice of material
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/35 with rollers
• CPC Class Codes: B29K 2069/00 Use of PC, i.e. polycarbonates or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2105/0002 monomers or prepolymers
• CPC Class Codes: B29K 2705/00 Use of metals, their alloys or their compounds, for preformed parts, e.g. for inserts
• CPC Class Codes: B29L 2007/008 Wide strips, e.g. films, webs
• CPC Class Codes: B29L 2017/005 CD''s, DVD''s
• CPC Class Codes: C08J 2369/00 Characterised by the use of polycarbonates; Derivatives of polycarbonates
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets

Abstract

A process for producing a polycarbonate film suitable for optical media applications having a birefringence of less than about 50 nm and low stress wherein the polycarbonate has a weight average molecular weight of about 30,000 or less and preferably 13,000 to about 25,000, extruding the polycarbonate film at a temperature of about 275° C. to about 360° C., the polycarbonate has a melt viscosity of about 100 to about 275 Pascal and a thickness of about 100 to about 600 μm, advancing the melted polymer film into a gap between two calendering rolls which calendaring rolls are at a temperature below the glass transition temperature, advancing the melted polycarbonate film through the gap and cooling the polycarbonate film wherein the polycarbonate film is extruded at the rate of about 10 to 100 feet per minute; and to a polycarbonate film prepared by the process above described.

Claims

1. A process for producing a continuous aromatic homo-polycarbonate resin film having a low birefringence of about 50 nm or less and a low stress wherein the process comprises extruding a polycarbonate resin film at an extrusion temperature of about 275°

C. to about 360°

C., and at a rate of about 10 to about 100 feet per minute, advancing the melted polymer film into a gap between two calendering rolls wherein the calendaring rolls are at a temperature below the glass transition temperature of the polycarbonate resin, advancing the melted polycarbonate resin film through said gap and cooling the polycarbonate resin film, said extruded polycarbonate resin having a melt viscosity of about 100 to about 275 Pascal and a weight average molecular weight of about 30,000 or less.

2. The process of claim 1 wherein the polycarbonate resin has a weight average molecular weight of about 13,000 to about 25,000.

3. The process of claim 1 wherein the polycarbonate resin film has a thickness of about 100 to about 600 μ

m.

4. The process of claim 1 wherein the polycarbonate resin has a weight average molecular weight of about 18,000 to about 30,000.

5. A polycarbonate resin film having a birefringence of 50 nm or less and low stress prepared by the process of claim 1.

6. A polycarbonate resin film suitable for optical media applications prepared by the process of claim 1.

7. A polycarbonate resin film having a birefringence of 50 nm or less and low stress prepared by the process of claim 4.