Light diffuser with variable diffusion

• US 6,846,098 B2
• Filed: 05/16/2002
• Issued: 01/25/2005
• Est. Priority Date: 05/16/2002
• Status: Expired due to Fees

• Current Assignee: Rohm and Haas Denmark Finance A/S (Dow, Inc.)
• Original Assignee: Eastman Kodak Company
• Inventors: Bourdelais, Robert P., Kaminsky, Cheryl J.
• Primary Examiner(s): Cariaso, Alan
• Assistant Examiner(s): Negron, Ismael
• Application Number:
  US10/147,703
• Publication Number:
  US 20030214812A1
• Time in Patent Office: 985 Days
• Field of Search: 362/19, 362/23, 362/26, 362/29, 362/30, 362/31, 362/317, 362/326, 362/327, 362/328, 362/330, 362/339, 362/351, 362/355, 362/551, 362/558, 362/560, 362/561, 405/41, 405/46, 405/53, 405/82, 385/129, 385/130, 385/131, 385/900, 349/64, 359/599
• US Class Current: 362/330
• CPC Class Codes: G02B 5/0221 the surface having an irregular structure G02B5/0226 takes precedence
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• CPC Class Codes: G02B 5/0247 by means of voids or pores
• CPC Class Codes: G02B 5/0263 with positional variation of the diffusing properties, e.g. gradient or patterned diffuser
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606

Abstract

A light diffuser comprises a film bearing a macro diffusion efficiency variation in which the efficiency variation is greater than 5% between two locations that are separated by at least 2 cm where the diffuser comprises a base and a plurality of convex or concave complex lenses on the surface of the base.

Claims

1. A light diffuser comprising a film bearing a macro diffusion efficiency variation in which the efficiency variation that is greater than 5% between two locations that are separated by at least 2 cm, the diffuser comprising a base and a plurality of convex or concave complex lenses comprising a plurality of lenses of all different sizes and shapes formed on top of one another and overlapping one another on the surface of said base.

2. The light diffuser of claim 1 wherein the diffusion efficiency varies by more than 10 percent in two different locations of the diffuser.

3. The light diffuser of claim 1 wherein the diffusion efficiency varies more than 50 percent in two different locations of the diffuser.

4. The light diffuser of claim 1 wherein the diffusion efficiency variation comprises a gradient.

5. The light diffuser of claim 1 being rectangular in shape wherein there is diffusion efficiency variation along a diagonal of the rectangle.

6. The light diffuser of claim 1 being rectangular in shape wherein there is diffusion efficiency variation along the width or height of the rectangle.

7. The light diffuser of claim 1 wherein there is diffusion efficiency variation from the geometric center to the perimeter of the diffuser.

8. The light diffuser of claim 1 wherein there is diffusion efficiency variation along the perimeter of the diffuser.

9. The light diffuser of claim 1 wherein the diffusion efficiency variation is such that iso-efficiency exhibits an elliptical pattern about the center of the diffuser.

10. The light diffuser of claim 1 wherein the diffusion efficiency variation comprises a repeating pattern.

11. The light diffuser of claim 1 wherein the diffusion efficiency variation comprises a specular component.

12. The light diffuser of claim 1 wherein the diffusion efficiency variation provides values at least 10% less in a perimeter area than in the center of said light diffuser.

13. The plurality of complex lenses of claim 1 wherein the said convex or concave complex lenses are randomly distributed on the surface.

14. The plurality of complex lenses of claim 1 wherein the said convex or concave lenses are present on both the top and bottom surfaces of said transparent polymeric film.

15. The plurality of complex lenses of claim 1 wherein said concave or convex complex lenses have a average frequency in any direction of 5 to 250 complex lenses/mm.

16. The plurality of complex lenses of claim 1 wherein said concave or convex complex lenses have an average width in the x and y direction of 3 to 60 microns.

17. The plurality of complex lenses of claim 1 wherein said concave or convex complex lenses have a height/diameter ratio of 0.03 to 1.0.

18. The plurality of complex lenses of claim 1 wherein said concave or convex complex lenses comprise a multiple of minor lenses wherein the minor lenses have a width in the x and y direction of 2 to 20 microns.

19. The transparent polymeric film of claim 18 wherein the number of minor lenses per major lens is 2 to 60.

20. The light diffuser of claim 1 wherein said light diffuser comprises a surface diffuser.

21. The light diffuser of claim 1 wherein said light diffuser comprises a bulk diffuser.

22. The light diffuser of claim 1 wherein variable light diffusion efficiency is the result of differences in the composition of diffusion elements.

23. The light diffuser of claim 1 wherein variable light diffusion efficiency is the result of differences in surface microstructures.

24. A back lighted imaging media comprising a light source and the light diffuser of claim 1.

25. A liquid crystal device comprising a light source and the light diffuser of claim 1, wherein the light diffuser is located between the light source and a polarizing film.

26. A liquid crystal device component comprising a light source and the light diffuser of claim 1.

27. The light diffuser of claim 1 further comprising a microvoided polymer sheet.

28. The light diffuser of claim 27 wherein the diffusion efficiency varies more than 50 percent in two different locations of the diffuser.

29. The light diffuser of claim 27 being rectangular in shape wherein there is diffusion efficiency variation along the width or height of the rectangle.

30. The light diffuser of claim 27 wherein there is diffusion efficiency variation along the perimeter of the diffuser.

31. The light diffuser of claim 27 wherein the diffusion efficiency variation comprises a specular component.

32. A back lighted imaging media comprising a light source and the light diffuser of claim 27.

33. A liquid crystal device comprising a light source and the light diffuser of claim 27, wherein the light diffuser is located between the light source and a polarizing film.

34. A process for forming a light diffusing polymeric film comprising selectively modifying a light diffuser by applying a gradient or pattern by at least one of heat and pressure, to produce a variable diffusion film;

said film having a plurality of lenses of all different sizes and shapes formed on top of one another and overlapping one another.

35. The process of claim 34 wherein heat is used to apply a gradient or pattern to the light diffuser.

36. The process of claim 34 wherein pressure is used to apply a gradient or pattem to the light diffuser.

37. The process of claim 34 wherein the light diffusion efficiency is selectively modified after the film is formed.