Method for making optical devices from homopolymers

• US 6,673,275 B1
• Filed: 10/11/2000
• Issued: 01/06/2004
• Est. Priority Date: 10/12/1999
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Hebrink, Timothy J., Johnson, Stephen A., Condo, Peter D., Merrill, William Ward, Tabar, Ronald J., Kent, Susan L., Allen, Richard C., Gangi, Joseph A., Cross, Elisa M.
• Primary Examiner(s): Vargot, Mathieu D.
• Application Number:
  US09/686,498
• Time in Patent Office: 1,182 Days
• Field of Search: 264/1.1, 264/1.31, 264/1.34, 264/2.7, 264/290.2, 359/483, 359/494, 359/500, 359/599
• US Class Current: 264/1.1
• CPC Class Codes: C08L 2666/18 Polyesters or polycarbonates according to C08L67/00 - C08L69/00; Derivatives thereof
• CPC Class Codes: C08L 67/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds C08L67/06 takes precedence
• CPC Class Codes: G02B 1/04 made of organic materials, e.g. plastics G02B1/08 takes precedence
• CPC Class Codes: G02B 5/3025 Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state G02B5/3008, G02B5/3016 take precedence
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid

Abstract

An improved optical film having a continuous/disperse phase morphology and a method for making the same is provided. At least one of the continuous and disperse phases comprises a blend of homopolymers which are inter-reacted, as by transesterification. The resulting films exhibit a higher degree of birefringence for a given level of strain than analogous films in which the blend is replaced by a random copolymer.

Claims

1. A method of forming an optical device, comprising the steps of:

providing first and second monomers;

inter-reacting said first and second monomers to form a copolymer P_n which has a lower degree of randomness than a statistically random copolymer P_r formed from the same monomers; and

stretching the copolymer P_n in at least one direction such that copolymer P_n exhibits a birefringence b, wherein |b|>

|k|, and wherein k is the maximum birefringence obtainable by the statistically random copolymer P_r at the same stretch ratio and under the same stretching conditions.

2. A polarizer made according to claim 1.

3. A forward-scattering diffuser made according to claim 1.

4. The method of claim 1, wherein said first and second monomers are reacted to give a copolymer having a degree of randomness of less than about 70%.

5. The method of claim 1, wherein said first and second monomers are reacted to give a copolymer having a degree of randomness of less than about 50%.

6. The method of claim 1, wherein said first and second monomers are reacted to give a copolymer having a degree of randomness of less than about 40%.

7. The method of claim 1, wherein the step of inter-reacting said first and second monomers comprises the steps of (a) solid state polymerizing the first and second monomers to form first and second homopolymers, respectively;

and

crosslinking the first and second homopolymers to form a block copolymer.

8. The method of claim 7, wherein the first and second homopolymers are blended together and coextruded as a molten mass.

9. The method of claim 8, wherein the extrudate comprises a continuous phase and a disperse phase.

10. The method of claim 8, wherein the first and second homopolymers are crosslinked during extrusion.

11. The method of claim 7, wherein the first and second homopolymers are PEN and PET, respectively.

12. The method of claim 7, wherein the first and second homopolymers are condensation homopolymers.

13. The method of claim 7, wherein the first and second homopolymers are crosslinked via a transesterification reaction.

14. The method of claim 7, wherein at least one of the first and second homopolymers is a polyester.

15. The method of claim 7, wherein at least one of the first and second homopolymers is a polyamide.

16. The method of claim 7, wherein at least one of the first and second homopolymers is a copolyesteramide.

17. The method of claim 7, wherein the copolymer has an intrinsic viscosity of at least 0.53.

18. The method of claim 1, wherein the copolymer has an intrinsic viscosity of at least 0.56.

19. The method of claim 1, wherein the copolymer is stretched to a stretch ratio of at least 1.25:

1 in the machine direction, and is stretched to a stretch ratio of at least 5.1;

1 in the transverse direction.