Optical device containing polymeric material domains having different degrees of randomness

• US 6,627,300 B1
• Filed: 10/11/2000
• Issued: 09/30/2003
• Est. Priority Date: 10/12/1997
• 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, Cross, Elisa M., Tabar, Ronald J., Kent, Susan L., Allen, Richard C., Gangi, Joseph A.
• Primary Examiner(s): Chen, Vivian
• Application Number:
  US09/686,519
• Time in Patent Office: 1,084 Days
• Field of Search: 428/212, 428/323, 428/327, 428/480, 525/88, 525/92.R, 525/92.F, 525/437, 525/444, 264/239, 264/280, 264/291, 359/483, 359/485, 359/487, 359/494, 359/500, 359/577, 359/580, 359/582, 359/586, 359/599
• US Class Current: 428/212
• CPC Class Codes: B29D 11/00009 Production of simple or compound lenses
• 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 5/02 Diffusing elements; Afocal elements
• CPC Class Codes: G02B 5/0808 having a single reflecting layer G02B5/0883, G02B5/0891 take precedence
• CPC Class Codes: G02B 5/0841 comprising organic materials, e.g. polymers
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/254 Polymeric or resinous material
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]

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:

creating a mixture having at least a first phase and a second phase, at least one of said phases comprising a blend of first and second homopolymers which are capable of inter-reacting; and

inter-reacting said first and second homopolymers.

2. The method of claim 1, wherein said first and second homopolymers are inter-reacted before said mixture is created.

3. The method of claim 1, wherein said first and second homopolymers are inter-reacted after said mixture is created.

4. The method of claim 1, wherein said first and second homopolymers are polyesters and are inter-reacted via a transesterification reaction.

5. An optical body made according to claim 1, wherein said optical body exhibits a given birefringence at a lower strain than a corresponding optical body made from a second copolymer having the same monomers in the same ratio but not made from homopolymers.

6. An optical body made according to claim 1, wherein said optical body exhibits a birefringence that is higher for a given strain than a corresponding optical body made from a second copolymer having the same monomers in the same ratio but not made from homopolymers.

7. An optical body made according to claim 1, wherein said optical body exhibits a higher on-axis gain than a corresponding optical body made from a second copolymer having the same monomers in the same ratio but not made from homopolymers.

8. A polarizer made according to claim 1.

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

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

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

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

13. The method of claim 1, further comprising the step of:

extruding the mixture into an optical film.

14. The method of claim 13, wherein the film has a continuous/disperse phase morphology.

15. The method of claim 1, wherein the blend is created at a non-zero shear rate, and wherein the viscosities of said first and second polymeric materials are essentially matched at said non-zero shear rate.

16. The method of claim 1, wherein said first and second homopolymers are inter-reacted to form a copolymer P_n which has a lower degree of randomness than a statistically random copolymer P_r formed from the sane monomers.

17. The method of claim 16, further comprising the step of stretching the copolymer P_r 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.

18. The method of claim 1, wherein the first and second homopolymers are PEN and PET, respectively, wherein the step of inter-reacting the first and second homopolymers results in a copolymer having a mole % NDC composition of between about 75% and 50%, and wherein the intrinsic viscosity of said copolymer is higher than that attainable from a second copolymer having the same monomers in the same ratio but not made from homopolymers.

19. The method of claim 1, wherein the first and second homopolymers are based on first and second monomers, respectively, wherein the step of inter-reacting the first and second homopolymers results in the formation of a first copolymer, and wherein the number average sequence length of said first monomer in said first copolymer is greater than the number average sequence length of said first monomer in a second statistically random copolymer based on the same monomers and ratios of monomers as said first copolymer.

20. The method of claim 1, wherein the first and second homopolymers are based on first and second monomers, respectively, wherein the step of inter-reacting the first and second homopolymers results in the formation of a first copolymer, and wherein the number average sequence length of the first and second monomers in the first copolymer is greater than that in a statistically random second copolymer having the same monomers in the same ratios.

21. The method of claim 1, wherein the step of inter-reacting the first and second homopolymers results in the formation of a copolymer P_n, and further comprising the steps of:

providing a copolymer P_r, wherein copolymer P_r contains essentially the same monomers, in essentially the same ratios, as copolymer P_n, wherein copolymer P_r has a greater degree of randomness than copolymer P_n, and wherein at least one of P_r and P_n exhibits strain-induced birefringence;

creating an article from copolymers P_r and P_n such that the copolymers are present in the first and second phases within the article; and

orienting the article along at least one axis.

22. The method of claim 21, wherein the refractive index differential between said first and second domains is at least 0.01 along a first axis.

23. The method of claim 21, wherein each of P_r and P_n are polyesters, and wherein copolymers P_r and P_n have % transesterifications of k and t, respectively, where k>

t.

24. The method of claim 21, wherein P_r and P_n are derived from monomers selected from the group consisting of monomers m₁, . . . , m_k, wherein the % by weight of each of monomers m₁, . . . , m_k present in P_r, based on the total weight of P_r, is w_r1, . . . , w_rk, respectively, wherein the % by weight of each of monomers m₁, . . . , m_k present in P_n, based on the total weight of P_n, is w_n1, . . . , w_nk, respectively, wherein the magnitude of the vector |w_r−

w_n| is less than about 15%, where w_r=[w_r1, . . . , w_rk] and w_n=[w_n1, . . . , w_nk], and wherein copolymers P_r and P_n have % transesterifications of k and t, respectively, where k>

t.

25. The method of claim 24, wherein the article is oriented along at least ore axis such that the difference in refractive indices between the first and second material domains is at least 0.03 along a first axis and is less than 0.01 along a second axis.

26. A polarizer, comprising:

a continuous phase and a disperse phase;

wherein at least one of said continuous and disperse phases comprises a blend of first and second homopolymers which are capable of inter-reacting to form a copolymer.

27. The polarizer of claim 26, wherein said first and second homopolymers are reacted to give a copolymer having a degree of randomness of less than about 70%.

28. The polarizer of claim 26, wherein said first and second homopolymers are reacted to give a copolymer having a degree of randomness of less than about 50%.

29. The polarizer of claim 26, wherein said first and second homopolymers are reacted to give a copolymer having a degree of randomness of less than about 40%.

30. A method for making an optical device, comprising the steps of:

providing a portion of material comprising a continuous phase and a disperse phase, wherein at least one of the continuous and disperse phases comprises a blend of at least a first and second homopolymer capable of inter-reacting; and

orienting the material in at least one direction until the material exhibits a level of birefringence Δ

n which is greater than Δ

n_max, wherein Δ

n_max is the maximum level of birefringence obtainable, under the same orientation conditions, for a portion of the continuous/disperse phase material of the same dimensions in which the blend is replaced by a like amount of a random copolymer comprising the same monomeric units, and the same ratios of monomeric units, as said blend.

31. The method of claim 30, wherein the material is oriented by stretching.

32. The method of claim 30, wherein Δ

n≧

0.05.

33. The method of claim 30, wherein each of said first and second homopolymers are polyesters.

34. The method of claim 30, further comprising the step of:

inter-reacting said first and second homopolymers.

35. The method of claim 34, wherein each of said first and second homopolymers is a polyester, and wherein said first and second homopolymers are inter-reacted by way of a transesterification reaction.

36. The method of claim 34, wherein each of said first and second homopolymers is an amide, and wherein said first and second homopolymers are inter-reacted by way of a transamidation reaction.

37. The method of claim 34, wherein the inter-reaction produces a copolymer, and wherein the copolymer has a degree of randomness of less than about 70%.

38. The method of claim 34, wherein the inter-reaction produces a copolymer, and wherein the copolymer has a degree of randomness of less than about 50%.

39. The method of claim 34, wherein the inter-reaction produces a copolymer, and wherein the copolymer has a degree of randomness of less than about 40%.

40. A method for making an optical device, comprising the steps of:

providing a material comprising a continuous phase and a disperse phase,

wherein at least one of said continuous and disperse phases comprises a blend of at least first and second homopolymers;

inter-reacting said first and second homopolymers so as to produce a modified material; and

forming said modified material into an optical device.

41. The method of claim 40, wherein said optical device specularly transmits visible light polarized along a first axis and scatters visible light polarized along a second axis.

42. The method of claim 40, wherein said first and second homopolymers are polyesters.

43. The method of claim 40, wherein said first and second homopolymers are inter-reacted via a transesterification reaction.

44. The method of claim 40, wherein the inter-reaction produces a copolymer, and wherein the copolymer has a degree of randomness of less than about 70%.

45. The method of claim 40, wherein the inter-reaction produces a copolymer, and wherein the copolymer has a degree of randomness of less than about 50%.

46. The method of claim 40, wherein the inter-reaction produces a copolymer, and wherein the copolymer has a degree of randomness of less than about 40%.