Intrinsic polarizer and method of manufacturing an intrinsic polarizer

• US 20060028725A1
• Filed: 08/03/2004
• Published: 02/09/2006
• Est. Priority Date: 08/03/2004
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Mack, Jonathan M., Ralli, Philip J., Nkwantah, Gerald N., Nagarkar, Pradnya V., Gerlach, Michael K.
• Granted Patent: US 7,573,637 B2
• Time in Patent Office: Days
• US Class Current: 359/490
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid

Abstract

An improved method of forming an intrinsic polarizer, referred to as a K-type polarizer, includes stretching a polymeric film a first stretching step. The polymeric film comprises a hydroxylated linear polymer which is converted after the first stretching step to form dichroic, copolymer polyvinylene blocks aligned in the polymeric film. The polymeric film is stretched in a second stretching step while converting the hydroxylated linear polymer. This method produces an improved K-type polarizer with excellent polarizing and color characteristics. For example, the dichroic ratio is higher than 100, the color shift for light passed through the polarizer in a crossed configuration is low, and the absorption of light in the blue region of the visible spectrum is more than one half of the absorption for light in the middle of the visible spectrum.

Claims

1. A method for making a polarizer from a polymeric film having an original length and comprising a hydroxylated linear polymer, the method comprising:

stretching the polymeric film a first stretching step;

converting the hydroxylated linear polymer, after the first stretching step, to form dichroic, copolymer polyvinylene blocks aligned in the polymeric film; and

stretching the polymeric film in a second stretching step while converting the hydroxylated linear polymer.

2. A method as recited in claim 1, wherein the hydroxylated linear polymer is at least one of polyvinyl alcohol, polyvinyl acetal, polyvinyl ketal and polyvinyl ester.

3. A method as recited in claim 1, further comprising exposing the polymeric film to a dehydration catalyst before stretching the polymeric film in the second stretching step.

4. A method as recited in claim 3, wherein exposing the polymeric film to the dehydration catalyst comprises immersing the polymeric film in a bath containing the dehydration catalyst.

5. A method as recited in claim 3, wherein the dehydration catalyst is an aqueous catalyst comprising at least one of hydrochloric acid, hyrdobromic acid, hydroiodic acid, phosphoric acid, and sulphuric acid in methanol.

6. A method as recited in claim 3, wherein dehydration catalyst comprises hydrochloric acid with a concentration ranging from about 0.01 Normal to about 4.0 Normal.

7. A method as recited in claim 3, further comprising stretching the polymeric film in the first stretching step while exposing the polymeric film to the dehydration catalyst.

8. A method as recited in claim 7, further comprising immersing the polymeric film in the dehydration catalyst and stretching the polymeric film in the first stretching step while immersed in the dehydration catalyst.

9. A method as recited in claim 3, further comprising stretching the polymeric film in the first stretching step after exposing the polymeric film to the dehydration catalyst.

10. A method as recited in claim 3, further comprising stretching the polymeric film in the first stretching step before exposing the polymeric film to the dehydration catalyst.

11. A method as recited in claim 3, wherein converting the hydroxylated linear polymer comprises heating the polymeric film to effect partial dehydration of the polymeric film, thereby forming vinylene block segments.

12. A method as recited in claim 11, further comprising converting the polymeric film by heating the polymeric film after exposing the polymeric film to the dehydration catalyst.

13. A method as recited in claim 12, wherein heating the polymeric film comprises exposing the polymeric film to infrared radiation.

14. A method as recited in claim 12, wherein heating the polymeric film comprises convectively heating the polymeric film.

15. A method as recited in claim 1, wherein the second stretching step is bidirectional unrelaxed, unidirectional unrelaxed or parabolic.

16. A method as recited in claim 1, wherein the first stretching step is bidirectional unrelaxed, unidirectional unrelaxed or parabolic.

17. A method as recited in claim 1, wherein the first stretching step comprises stretching the polymeric film to an intermediate length in the range from about 3.5. to about 7 times the original length.

18. A method as recited in claim 17, wherein the second stretching step comprises stretching the polymeric film to a stretched length of about 1.1 to 2.5 times the length of the intermediate length.

19. A method as recited in claim 1, wherein stretching in the first and second stretching steps combines to stretching the polymeric film from about 4 times to about 8.5 times the original length.

20. A method as recited in claim 1, further comprising borating the polymeric film after second stretching step.

21. A method as recited in claim 20, wherein borating the polymeric film comprises exposing the polymeric film to a borating solution containing at least boric acid.

22. A method as recited in claim 21, wherein the solution contains from about 5% to about 20% by weight boric acid.

23. A method as recited in claim 21, wherein the solution also contains one of a sodium borate and a potassium borate.

24. A method as recited in claim 23, wherein the solution contains from about 0% to about 7% by weight sodium borate decahydrate.

25. A method as recited in claim 21, wherein the borating solution has a temperature in excess of 50°

C.

26. A method as recited in claim 25, wherein the borating solution has a temperature in the range from about 70°

C. to about 110°

C.

27. A method as recited in claim 21, further comprising drying the polymeric film after exposing the polymeric film to the borating solution containing at least boric acid.

28. A method as recited in claim 20, further comprising permitting the polymeric film to shrink to a borated length while borating the polymeric film.

29. A method as recited in claim 28, further comprising stretching the polymeric film in a third stretching step after permitting the polymeric film to shrink while borating the polymeric film.

30. A method as recited in claim 29, wherein stretching the polymeric film in the third stretching step comprises stretching the polymeric film up to about 120% of the borated length.

31. An intrinsic polarizer, comprising:

a sheet of PVA-type matrix containing vinylene polymer blocks, the sheet defining a pass polarization axis and a block polarization axis perpendicular to the pass polarization axis, light having an electrical vector parallel to the pass polarization axis being substantially transmitted through the sheet and light having an electrical vector parallel to the block polarization axis being substantially absorbed by the vinylene polymer blocks, the sheet exhibiting a ratio, R, having a value of less than 2, where R is the ratio of the intrinsic absorbance for light at 550 nm polarized parallel to the block polarization axis over the intrinsic absorbance for light at 400 nm polarized parallel to the block polarization axis, and exhibiting a polarization efficiency ratio in excess of 99%.

32. A polarizer as recited in claim 31, wherein the value of R is less than 1.7.

33. A polarizer as recited in claim 31, wherein the polarization efficiency ratio is greater than 99.5%.

34. A polarizer as recited in claim 33, wherein the polarization efficiency ratio is greater than 99.8%.

35. A polarizer as recited in claim 31, wherein the average light transmission for unpolarized light, Kv, through the sheet is greater than 42%.

36. A polarizer as recited in claim 35, wherein Kv has a value greater than 43%.

37. A polarizer as recited in claim 31, wherein the sheet exhibits a dichroic ratio of more than 100.

38. A polarizer as recited in claim 37, wherein the sheet exhibits a dichroic ratio of more than 110.

39. A polarizer as recited in claim 31, wherein the sheet exhibits an intrinsic absorption spectrum such that, when crossed with an identical sheet and illuminated with a cold cathode fluorescent tube (CCFT) light source, the sheet transmits light having an a* co-ordinate with a magnitude of less than 2 and a b* co-ordinate with a magnitude of less than 2.

40. An intrinsic polarizer, comprising:

a sheet of PVA-type matrix containing vinylene polymer blocks, the sheet defining a pass polarization axis and a block polarization axis perpendicular to the pass polarization axis, light having an electrical vector parallel to the pass polarization axis being substantially transmitted through the sheet and light having an electrical vector parallel to the block polarization axis being substantially absorbed by the vinylene polymer blocks, the sheet having an intrinsic absorption spectrum such that, when crossed with an identical sheet and illuminated with a cold cathode fluorescent tube (CCFT) light source, the sheet transmits light having an a* co-ordinate with a magnitude of less than 2 and a b* co-ordinate with a magnitude of less than 2.

41. A polarizer as recited in claim 40, wherein the transmitted light has an a* value with a magnitude less than 1.

42. A polarizer as recited in claim 40, wherein the transmitted light has a b* value with a magnitude less than 1.

43. A polarizer as recited in claim 40, wherein the transmitted light has an a* value with a magnitude of less than 1 and a b* value with a magnitude less than 1.

44. A polarizer as recited in claim 40, wherein the sheet exhibits a ratio, R, having a value of less than 2, where R is a ratio of absorbance for light at 550 nm polarized parallel to the block polarization axis over absorbance for light at 400 nm polarized parallel to the block polarization axis.

45. A polarizer as recited in claim 44, wherein R has a value of less than 1.7.

46. A polarizer as recited in claim 40, wherein the sheet exhibits a polarization efficiency in excess of 99%.

47. A polarizer as recited in claim 46, wherein the polarization efficiency ratio is greater than 99.5%.

48. A polarizer as recited in claim 46, wherein the polarization efficiency ratio is greater than 99.8%.

49. A polarizer as recited in claim 40, wherein the average light transmission for unpolarized light, Kv, through the sheet is greater than 42%.

50. A polarizer as recited in claim 49, wherein Kv has a value greater than 43%.

51. A polarizer as recited in claim 40, wherein the sheet exhibits a polarization dichroic ratio of more than 100.

52. A polarizer as recited in claim 51, wherein the sheet exhibits a dichroic ratio of more than 110.

53. An intrinsic polarizer, comprising:

a sheet of PVA-type matrix containing vinylene polymer blocks, the sheet defining a pass polarization axis and a block polarization axis perpendicular to the pass polarization axis, light having an electrical vector parallel to the pass polarization axis being substantially transmitted through the sheet and light having an electrical vector parallel to the block polarization axis being substantially absorbed by the vinylene blocks, the sheet exhibiting a dichroic ratio of more than 100.

54. A polarizer as recited in claim 53, wherein the dichroic ratio is more than 110.

55. A polarizer as recited in claim 53, wherein the average light transmission for unpolarized light, Kv, through the sheet is greater than 42%.

56. A polarizer as recited in claim 55, wherein Kv has a value greater than 43%.

57. A polarizer as recited in claim 53, wherein the sheet exhibits a ratio, R, having a value of less than 2, where R is a ratio of absorbance for light at 550 nm polarized parallel to the block polarization axis over absorbance for light at 400 nm polarized parallel to the block polarization axis.

58. A polarizer as recited in claim 57, wherein R has a value of less than 1.7.

59. A polarizer as recited in claim 53, wherein the sheet exhibits a polarization efficiency in excess of 99%.

60. A polarizer as recited in claim 59, wherein the polarization efficiency ratio is greater than 99.5%.

61. A polarizer as recited in claim 60, wherein the polarization efficiency ratio is greater than 99.8%.

62. A polarizer as recited in claim 53, wherein the sheet exhibits an intrinsic absorption spectrum such that, when crossed with an identical sheet and illuminated with a cold cathode fluorescent tube (CCFT) light source, the sheet transmits light having an a* co-ordinate with a magnitude of less than 2 and a b* co-ordinate with a magnitude of less than 2.