High optical purity copolymer film

Abstract

The invention relates to a high optical purity toughened copolymer film or coating. The copolymer is a graft or block copolymer, preferably acrylic, preferably produced by a controlled radical polymerization having an extremely low degree of particulate contamination and excellent optical properties. The film or coating is preferably formed by solvent-casting on a temporary substrate or solvent-coating on a permanent substrate.

Description

Claims

1. A high optical purity toughened copolymer film or coating comprising a block or graft copolymer having hard and soft blocks, wherein said film or coating contains less than 0.5 visible defects per square foot.

2. The high optical purity film or coating of claim 1 wherein said film is formed by a solvent-casting film process or a solvent-coating process.

3. The high optical purity film or coating of claim 1 wherein said hard block comprises primarily methylmethacrylate units and said soft block comprises primarily alkyl acrylate units.

4. The high optical purity film or coating of claim 1 consisting of the block or graft copolymer.

5. The high optical purity film or coating of any of claim 1 comprising from 5 to 95 weight percent of said block or graft copolymer and from 5 to 95 percent by weight of a thermoplastic matrix polymer

6. The high optical purity film or coating of claim 1 wherein said hard block has a Tg of greater than 20° C. and preferably greater than 50° C., and said low Tg block has a Tg of less than 20° C., and preferably less than 0° C.

7. The high optical purity film or coating of claim 1 wherein said block or graft copolymer has a molecular weight of from 1,000 to 1,000,000 g/mol.

8. The high optical purity film or coating of claim 1 wherein said block or graft copolymer is formed by controlled radical polymerization.

9. The high optical purity film or coating of claim 1 wherein said block or graft copolymer is formed by nitroxide-mediated controlled radical polymerization.

10. The high optical purity film or coating of claim 1 wherein said film contains no particle greater than 30 microns, and preferably no greater than 5 microns.

11. The high optical purity film or coating of claim 1 wherein said film has a variation of thickness of no more than 3% of the film thickness.

12. The high optical purity film or coating of claim 1 wherein said film or coating further comprises one or more additives selected from the group consisting of pigments, dyes, plasticizers, antioxidants, heat stabilizers, UV stabilizers, processing additives, lubricants and impact modifiers.

13. The high optical purity film or coating of claim 1 wherein said film or coating retains its original optical properties under mechanical stress and during thermo-processimg.

14. A process for forming a toughened acrylic copolymer-based film or coating comprising the steps of: a) forming a block or graft copolymer by a controlled radical polymerization, having hard and soft blocks;b) forming a stable polymer/solvent admixture of said block or graft copolymer in a solvent;c) coating said polymer/solvent admixture onto a substrate;d) evaporating said solvent to form a film or coating.

15. The process of claim 14 wherein said polymer/solvent admixture is coated onto said substrate by solvent-casting or solvent-coating.

16. The process of claim 14 further comprising the step of filtering said polymer/solvent admixture of step b) through a filter of 30 microns or less, prior to coating.

17. The process of any of claim 14 further comprising the step of blending said block or graft copolymer with a thermoplastic matrix polymer, prior to said coating step c).

18. The process of any of claim 14, wherein said step d) evaporation of solvent forms a toughened film which is then removed from the substrate for further processing into or onto a finished article.

19. The process of any of claim 14 wherein said step d) forms a toughened coating which is adhered onto said substrate.