Optical film and a liquid crystal display using the same

• US 6,903,788 B2
• Filed: 07/03/2002
• Issued: 06/07/2005
• Est. Priority Date: 07/05/2001
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Kawamoto, Ikuo, Shiraogawa, Miki, Motomura, Hironori
• Primary Examiner(s): TON, MINH TOAN T
• Application Number:
  US10/188,330
• Publication Number:
  US 20030071947A1
• Time in Patent Office: 1,070 Days
• Field of Search: 349113-115, 349/122, 349/69, 359494-495, 359/487
• US Class Current: 349/115
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0071 with elongated shape, e.g. tube
• CPC Class Codes: G02F 1/133543 Cholesteric polarisers
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n

Abstract

An optical film having excellent light utilization efficiency and high brightness, and a liquid crystal display using the optical film. The optical film is formed by laminating integrally a brightness enhancement film (A) that separates natural light into transmitted light and reflected light and a collimating film (B) having an uneven portion on a surface thereof. Since an air interface is eliminated by the integral lamination of the brightness enhancement film and the collimating film, stray light is reduced, and the brightness enhancement film has an improved efficiency in reflecting and polarizing light; thereby, enhancing the brightness.

Claims

1. A liquid crystal display having an optical film provided on at least one surface of a liquid crystal cell,

the optical film comprising a brightness enhancement film (A) that separates natural light into transmitted light and reflected light and a collimating film (B) having a uneven portion on one surface thereof, said collimating film having a surface facing a display side of the liquid crystal display and a surface opposed to the display side of the liquid crystal display;

wherein the brightness enhancement film (A) and the collimating film (B) are integrally laminated with each other so that the uneven portion of the collimating film is provided on the surface opposed to the display side of the liquid crystal display.

2. The liquid crystal display according to claim 1, wherein the light passing through the brightness enhancement film (A) is linearly-polarized light.

3. The liquid crystal display according to claim 1, wherein the collimating film (B) comprises a prism portion.

4. The liquid crystal display according to claim 1, wherein the brightness enhancement film (A) is formed by integrally laminating a cholesteric liquid crystal layer, a λ

/4 plate, and an absorption dichroic polarizing plate in this order.

5. The liquid crystal display according to claim 4, wherein the cholesteric liquid crystal layer is formed by supporting an oriented film of a cholesteric liquid crystal polymer or an oriented liquid crystal layer thereof on a film substrate.

6. The liquid crystal display according to claim 4, wherein the cholesteric liquid crystal layer comprises at least two liquid crystal layers laminated with each other, and the liquid crystal layers have different reflection wavelengths.

7. The liquid crystal display according to claim 1, wherein the brightness enhancement film (A) and the collimating film (B) are integrally laminated via either an adhesive or a pressure-sensitive adhesive.

8. The liquid crystal display according to claim 1, wherein the brightness enhancement film is applied with a resin to which a prism pattern is transferred for providing a light condensing function.

9. The liquid crystal display according to claim 1, wherein the collimating film comprises a prism portion and converges light emitted at an angle in a range of 30°

to 80°

with respect to a normal line to a vicinity of the normal line.

10. The liquid crystal display according to claim 9, wherein the prism of the collimating film has a chevron shape with an apex angle in a range of 20°

to 80°

.

11. The liquid crystal display according to claim 9, wherein the prism of the collimating film has a wave shape.

12. The liquid crystal display according to claim 1, further comprising a backlight.

13. A liquid crystal display according to claim 1, wherein said optical film has a side facing a display side of the liquid crystal display and a side opposed to the display side of the liquid crystal display, and the collimating film is on a the side of the optical film opposed to the display side of the liquid crystal display.

14. The liquid crystal display according to claim 13, wherein the light passing through the brightness enhancement film (A) is linearly-polarized light.

15. The liquid crystal display according to claim 14, wherein the brightness enhancement film (A) is a laminated body of a cholesteric liquid crystal layer and a λ

/4 plate.

16. The liquid crystal display according to claim 13, wherein the collimating film (B) comprises a prism portion.

17. The liquid crystal display according to claim 13, wherein the brightness enhancement film (A) that separates natural light into light transmitted as linearly-polarized light and reflected light containing reusable circularly-polarized light and the collimating film (B) having a prism portion on one surface thereof are integrally laminated with each other.

18. The liquid crystal display according to claim 13, wherein the brightness enhancement film (A) is formed by integrally laminating a cholesteric liquid crystal layer, a λ

/14 plate, and an absorption dichroic polarizing plate in this order.

19. The liquid crystal display according to claim 18, wherein the cholesteric liquid crystal layer is formed by supporting an oriented film of a cholesteric liquid crystal polymer or an oriented liquid crystal layer thereof on a film substrate.

20. The liquid crystal display according to claim 18, wherein the cholesteric liquid crystal layer comprises at least two liquid crystal layers laminated with each other, and the liquid crystal layers have different reflection wavelengths.

21. The liquid crystal display according to claim 13, wherein the brightness enhancement film (A) and the collimating film (B) are integrally laminated via either an adhesive or a pressure-sensitive adhesive.

22. The liquid crystal display according to claim 13, wherein the brightness enhancement film is applied with a resin to which a prism pattern is transferred for providing a light condensing function.

23. The liquid crystal display according to claim 13, wherein the collimating film comprises a prism portion and converges light emitted at an angle in a range of 30°

to 80°

with respect to a normal line to a vicinity of the normal line.

24. The liquid crystal display according to claim 13, wherein the prism of the collimating film has a chevron shape with an apex angle in a range of 20°

to 80°

.

25. The liquid crystal display according to claim 23, wherein the prism of the collimating film has a wave shape.