DOUBLE-SIDED TURNING FILM

• US 20080259634A1
• Filed: 04/18/2007
• Published: 10/23/2008
• Est. Priority Date: 04/18/2007
• Status: Active Grant

• Current Assignee: SKC Haas Display Films Co., Ltd. (Dow, Inc.)
• Original Assignee: SKC Haas Display Films Co., Ltd. (Dow, Inc.)
• Inventors: Bourdelais, Robert P., Ishikawa, Tomohiro, Mi, Xiang-Dong, Lei, Herong, Greener, Jehuda, Walton, Robert L., Bomba, Richard D., Neerbasch, Steven J., Palmeri, John M., Ferranti, Michael L., Meissner, Stephen C., Harasta, Louis P.
• Granted Patent: US 7,530,721 B2
• Time in Patent Office: Days
• US Class Current: 362/606
• CPC Class Codes: B29D 11/00663 Production of light guides
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects

Abstract

A backlight device for a display comprising (1) a side-lit light source, (2) a light guide plate and (3) a turning film comprising a light entry and a light exit surface comprising lenticular elements on the exit surface and prismatic structures on the entry surface, wherein the average values of the parameters of the features and the thickness of the film are selected to provide a peak output angle of ±10° from normal to the light exit surface of the light guide plate and an optical gain of at least 1.25. Also disclosed are methods of making the turning film and a display incorporating the backlight.

Claims

1. A backlight device for a display comprising (1) a side-lit light source, (2) a light guide plate, and (3) a turning film comprising melt-extrudable and thermo-formable polymeric material, the turning film comprising prismatic structures on the light entry surface of the film and lenticular elements on the light exit surface of the film, wherein:

(a) the prismatic structures are characterized by an average apex angle (α

+β

) and an average pitch (Q);

(b) the lenticular elements are characterized by an average pitch (P) and an average radius of curvature (R); and

(c) the prismatic structures and lenticular elements are out of registration by an average amount (X), and

(d) the film has average thickness (T);

provided that said averages are selected to provide a peak output angle of ±

10°

from normal to the light exit surface of the light guide plate and an optical gain of at least 1.25.

2. The device of claim 1 wherein the turning film comprises a polymer selected from the group consisting of carbonate, ester, sulfone, ethersulfone, and cyclo-olefin.

3. The device of claim 1 wherein at least one side of the prismatic structure is curved.

4. The device of claim 1 wherein the lens shape for the lenticular element, in cross section, is acircular.

5. The device of claim 1 wherein the prismatic structures vary in height.

6. The device of claim 1 wherein the turning film has an average pitch values P and Q are equal.

7. The device of claim 1 wherein the turning film apex angle is rounded and the apex has a radius less than about 0.26P.

8. The device of claim 1 wherein the turning film prismatic structures are extended along a serpentine path on the light entry surface.

9. The device of claim 1 wherein the turning film lenticular elements are extended along a serpentine path on the light exit surface.

10. The device of claim 1 wherein the turning film value derived from the formula

11. The device of claim 1 wherein the index of refraction of material forming the turning film is in the range from 1.2 to 1.9.

12. The device of claim 1 wherein the average ratio X/P is in the range from about 0.05 to 0.30.

34. A display comprising the backlight of claim 1.

13. A carrierless method for producing a web having a pattern on each side comprising the steps of:

(a) heating the material for forming the web;

(b) pumping the material into a first cavity at a controlled rate;

(c) distributing the material in the first cavity over a length of a slot;

(d) forcing said material into a second cavity formed by a first external land surface, a second external land surface and a surface of a first roller to form a first pattern on the first surface of the web by partially solidifying said material under high-pressure; and

(e) passing said partially solidified material through a nip formed between said first roller and a second roller to form a second pattern on the second surface of the web using pressure between the first and second rollers.

14. The method of claim 13 wherein one of the first and second patterns comprises a prismatic structure characterized by an average apex angle (α

+β

) and an average pitch (Q);

the other pattern comprises lenticular elements characterized by an average pitch (P) and an average radius of curvature (R),

wherein the prismatic structures and lenticular elements are out of registration by an average amount (X), and

wherein the average thickness of the film is (T);

provided that said averages are selected to provide a peak output angle of ±

10°

of normal and an optical gain of at least 1.25.

15. The method of claim 13 further comprising:

(i) sampling the completed web to determine properties of the first and second patterns of optical elements at various points across the width of the web; and

(ii) adjusting the alignment of the patterns of optical elements on the web as a result of the sampling.

16. The method of claim 13 wherein the formed pattern comprises a prismatic structure characterized by an average apex angle (α

+β

) and an average pitch (Q) and lenticular elements characterized by an average pitch (P) and an average radius of curvature (R),

wherein the prismatic structures and lenticular elements on the two sides are out of registration by an average amount (X),

wherein the average thickness of the film is (T);

and wherein the averages are selected to provide a peak output angle of ±

10°

of normal and an optical gain of at least 1.25.

17. A method for producing a web or sheet having aligned patterns of optical elements on opposite sides of the web comprising the steps of

(a) forming on each side of a web patterns of optical elements aligned with each other and oriented in a machine direction, with or without using a carrier web;

(b) sampling the completed web to determine properties of the pattern of optical elements at various points across the width of the web;

(c) adjusting the alignment of the patterns of optical elements on the web as a result of the sampling.

18. The method of claim 17 wherein the formed patterns comprise a prismatic structure characterized by an apex angle (α

+β

) and an average pitch (Q) and lenticular elements characterized by an average pitch (P) and an average radius of curvature (R),

wherein the prismatic structures and lenticular elements on the two sides are out of registration by an average amount X, and

wherein the average thickness of the film is T;

and wherein the averages are selected to provide a peak output angle of ±

10°

of normal and an optical gain of at least 1.25.

19. A method for producing a web having a pattern on each side comprising:

(a) forming a web with a first pattern on one surface using a curing process, wherein the first pattern is parallel to the machine direction;

(b) melting a polymeric material for forming a second patterned surface;

(c) pumping the material through an extrusion die forming a melt curtain at a controlled rate;

(d) directing said material into a nip formed by a first roller and the web, and a second roller partially solidifying said material under high-pressure to form the second pattern on the opposing surface of the web wherein the second pattern is parallel to the machine direction; and

(e) directing the web along the surface of one of the rollers while cooling and stripping the web when it has approximately reached the glass transition temperature of the polymeric material.

20. The method of claim 19 wherein the formed pattern comprises a prismatic structure characterized by an average apex angle (α

+β

) and an average pitch (Q) and lenticular elements on the opposite surface characterized by an average pitch (P) and an average radius of curvature (R),

wherein the prismatic structures and lenticular elements on the two patterned surfaces are out of registration by an average amount X, and

wherein the average thickness of the film is T;

and wherein the averages are selected to provide a peak output angle of ±

10°

of normal and an optical gain of at least 1.25.

21. A method for producing a web having a pattern on each side comprising:

(a) forming the web with a first pattern on one surface using a curing process, wherein the first pattern is parallel to the machine direction;

(b) forming a second pattern on the opposite surface using a curing process, wherein the second pattern is parallel to the first surface.

22. The method of claim 21 wherein the formed pattern comprises a prismatic structure characterized by an average apex angle (α

+β

) and an average pitch (Q) and lenticular elements on the opposite surface characterized by an average pitch (P) and an average radius of curvature (R),

wherein the prismatic structures and lenticular elements on the two patterned surfaces are out of registration by an average amount X, and

wherein the average thickness of the film is T;

and wherein the averages are selected to provide a peak output angle of ±

10°

of normal and an optical gain of at least 1.25.

23. A backlight device for a display comprising (1) a side-lit light source, (2) a light guide plate and (3) a turning film comprising a light entry and a light exit surface comprising lenticular elements on the exit surface and prismatic structures on the entry surface, wherein

(a) the prismatic structures are characterized by an apex angle (α

+β

) and an average pitch (Q);

(b) the lenticular elements are characterized by an average pitch (P) and an average radius of curvature (R); and

(c) wherein the prismatic structures and lenticular elements are out of registration by an average amount X,

(d) the thickness of the film is T;

provided that the averages are selected to provide a peak output angle of ±

10°

of normal to the light exit surface of the light guide plate and an optical gain of at least 1.25.

24. The device of claim 23 wherein, for the turning film, both average pitch values P and Q are equal.

25. The device of claim 23 wherein, for the turning film, the apex angle is rounded and the apex has a radius less than about 0.26P.

26. The device of claim 23 wherein, for the turning film, at least one side of the elongated prismatic structure is curved.

27. The device of claim 23 wherein, for the turning film, the lens shape for the lenticular element, in cross-section, is acircular.

28. The device of claim 23 wherein, for the turning film, the lens shape for the lenticular element, in cross-section, is substantially circular.

29. The device of claim 23 wherein, for the turning film, the ratio R/P is in the range from about 0.9 to 5.

30. The device of claim 23 wherein, for the turning film, the value of the formula:

31. The device of claim 23 wherein, for the turning film, the index of refraction for the material forming the turning film is in the range from 1.2 to 1.9.

32. The device of claim 23 wherein, for the turning film, the ratio average of X/P is in the range from about 0.05 to 0.30.

33. The device of claim 23 having a light entry and a light exit surface comprising lenticular elements on the exit surface and prismatic structures on the entry surface, wherein

(a) the prismatic structures are characterized by an apex angle (α

+β

) and an average pitch (Q);

(b) the lenticular elements are characterized by an average pitch (P) and an average radius of curvature (R); and

(c) wherein the prismatic structures and lenticular elements are out of registration by an average amount X,

(d) the thickness of the film is T;

provided that the averages of the angles and extent out of registration, are such that (α

+β

) are in the range of 58 to 74° and

the extent out of registration is such that ratio X/P is in the range of 0.05 to 0.30.

35. A display comprising the backlight of claim 23.

36. A carrierless method for producing a web having a pattern on each side comprising the steps of:

(a) heating the material for forming the web;

(b) pumping the material into a first cavity at a controlled rate;

(c) distributing the material in the first cavity over a length of a slot;

(d) forcing said material into a second cavity formed by a first external land surface, a second external land surface and a surface of a first roller to form a first pattern on the first surface of the web by partially solidifying said material under high-pressure;

(e) passing said partially solidified material through a nip formed between said first roller and a second roller to form a second pattern on the second surface of the web using pressure between the first and second rollers.

37. A carrierless method for producing a web having a pattern on each side comprising the steps of:

(a) melting a polymeric material for forming the web;

(b) pumping the material through an extrusion die forming a melt curtain at a controlled rate;

(c) directing said material into a nip formed by a first roller and a second roller partially solidifying said material under high-pressure to form on each side of the web a pattern parallel to the machine direction; and

(d) directing the web along the surface of one of the rollers while cooling and stripping the web when it has approximately reached the glass transition temperature of the polymeric material.