Light diffusion sheet and backlight unit using the same

• US 20020114169A1
• Filed: 02/22/2002
• Published: 08/22/2002
• Est. Priority Date: 02/22/2001
• Status: Active Grant

• Current Assignee: Keiwa KK
• Original Assignee: Keiwa KK
• Inventors: Harada, Kenichi, Masaki, Hitoshi
• Granted Patent: US 6,709,143 B2
• Time in Patent Office: Days
• US Class Current: 362/558
• CPC Class Codes: F21V 3/04 characterised by materials, surface treatments or coatings
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects

Abstract

A light diffusion sheet comprising a transparent base material sheet; a light diffusion layer laminated on a surface of the base material sheet and containing beads dispersed within a binder; and a sticking-inhibiting layer laminated on a rear face of the base material sheet, wherein the binder of the light diffusion layer contains a thermosetting resin and the sticking-inhibiting layer is a resin layer containing an ionizing radiation curable resin. In the light diffusion sheet of the invention, which employs an ionizing radiation curable resin for the binder of the sticking-inhibiting layer, the cross-linking density of the binder can be increased, whereby the wear resistance of the sticking-inhibiting layer as well as the wear resistance of the rear face of the light diffusion sheet can be increased. Further, possible occurrence of scratches in the sticking-inhibiting layer, which is attributable to the contact between the sticking-inhibiting layer and the beads of the light diffusion layer, can be effectively avoided.

Claims

1. A light diffusion sheet comprising:

a transparent base sheet;

a light diffusion layer laminated on a surface of the base sheet and containing beads dispersed within a binder; and

a sticking-inhibiting layer laminated on a rear face of the base sheet,

wherein the binder of the light diffusion layer contains a thermosetting resin and the sticking-inhibiting layer is a resin layer containing an ionizing radiation-curable resin.

2. A light diffusion sheet according to claim 1, wherein said sticking-inhibiting layer is a flat resin layer.

3. A light diffusion sheet according to claim 1, wherein said sticking-inhibiting layer contains beads dispersed therein.

4. A light diffusion sheet according to claim 1, wherein said ionizing radiation-curable resin is an ultraviolet-curable resin.

5. A light diffusion sheet according to claim 4, wherein said ultraviolet-curable resin is so formed as to have a glass-transition temperature (Tg) of 20°

C. to 50°

C.

6. A light diffusion sheet according to claim 4, wherein said ultraviolet-curable resin is so formed as to have a glass-transition temperature (Tg) of 50°

C. to 150°

C.

7. A light diffusion sheet according to claim 1, wherein the light diffusion layer further contains wax particles dispersed within the binder.

8. A light diffusion sheet according to claim 1, wherein said sticking-inhibiting layer further contains wax particles dispersed within the resin layer.

9. A light diffusion sheet according to claim 7, wherein the particles of said wax project from the surface of the binder.

10. A light diffusion sheet according to claim 8, wherein the particles of said wax project from the surface of the resin layer.

11. A light diffusion sheet according to claim 7, wherein the average particle size of the wax is within the range of from 1 to 25 μ

m.

12. A light diffusion sheet according to claim 8, wherein the average particle size of the wax is within the range of from 1 to 25 μ

m.

13. A light diffusion sheet according to claim 7, wherein the amount of the wax contained in the light diffusion layer is within the range of from 0.5 to 5 wt % based on the weight of the binder.

14. A light diffusion sheet according to claim 8, wherein the amount of the wax contained in the sticking-inhibiting layer is within the range of from 0.5 to 5 wt % based on the weight of the resin layer.

15. A light diffusion sheet according to claim 7, wherein said wax is selected from the group consisting of polyethylene wax, polypropylene wax, polytetrafluoroethylene wax and the combinations of these waxes.

16. A light diffusion sheet according to claim 8, wherein said wax is selected from the group consisting of polyethylene wax, polypropylene wax, polytetrafluoroethylene wax and the combinations of these waxes.

17. A light diffusion sheet according to claim 1, wherein said light diffusion layer further contains micro inorganic filler particles dispersed within the binder.

18. A light diffusion sheet according to claim 1, wherein said sticking-inhibiting layer further contains micro inorganic filler particles dispersed within the resin layer.

19. A light diffusion sheet according to claim 17, wherein the average particle diameter of said micro inorganic filler is within the range of from 5 nm to 1 μ

m.

20. A light diffusion sheet according to claim 18, wherein the average particle diameter of said micro inorganic filler is within the range of from 5 nm to 1 μ

m.

21. A light diffusion sheet according to claim 17, wherein the amount of the micro inorganic filler is 10 to 500 parts by weight per 100 parts of the polymer of the light diffusion layer or the sticking-inhibiting layer.

22. A light diffusion sheet according to claim 18, wherein the amount of the micro inorganic filler is 10 to 500 parts by weight per 100 parts of the polymer of the light diffusion layer or the sticking-inhibiting layer.

23. A light diffusion sheet according to claim 17, wherein said micro inorganic filler is colloidal silica.

24. A light diffusion sheet according to claim 18, wherein said micro inorganic filler is colloidal silica.

25. A backlight unit for use in a liquid crystal display, the unit comprising a lamp;

a light guide plate disposed beside the lamp for guiding light beams to a front side of the light guide plate, the light beams having been emitted from the lamp; and

the light diffusion sheet of claim 1 and disposed on the front side of the light guide plate.