OPTICAL SHEET AND DISPLAY DEVICE

• US 20110216416A1
• Filed: 09/17/2009
• Published: 09/08/2011
• Est. Priority Date: 09/17/2008
• Status: Active Grant

• Current Assignee: Dai Nippon Printing Company Limited
• Original Assignee: Dai Nippon Printing Company Limited
• Inventors: Kashiwagi, Tsuyoshi, Sadahiro, Tetsuya, Amemiya, Hiroyuki, Ichikawa, Nobuhiko
• Granted Patent: US 8,891,169 B2
• Time in Patent Office: Days
• US Class Current: 359/609
• CPC Class Codes: B32B 2264/00 Composition or properties of particles which form a particulate layer or are present as additives
• CPC Class Codes: B32B 2307/40 having particular optical properties
• CPC Class Codes: B32B 2307/402 Coloured
• CPC Class Codes: B32B 2307/418 Refractive
• CPC Class Codes: B32B 2307/732 Dimensional properties
• CPC Class Codes: B32B 2457/20 Displays, e.g. liquid crystal displays, plasma displays
• CPC Class Codes: B32B 2457/202 LCD, i.e. liquid crystal displays
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/16 specially treated, e.g. irradiated
• CPC Class Codes: B32B 27/28 comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
• CPC Class Codes: B32B 27/302 comprising aromatic vinyl (co)polymers, e.g. styrenic (co)polymers
• CPC Class Codes: B32B 27/308 comprising acrylic (co)polymers
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: B32B 27/38 comprising epoxy resins
• CPC Class Codes: B32B 3/18 characterised by an internal layer formed of separate pieces of material which are juxtaposed side-by-side B32B5/02 takes precedence
• CPC Class Codes: B32B 5/142 Variation across the area of the layer
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: G02B 5/003 Light absorbing elements
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 5/045 : Prism arrays
• CPC Class Codes: G03B 21/62 : Translucent screens

Abstract

There is provided an optical sheet and a display device which hardly cause a change in color depending on the observation angle of an image.

The optical sheet comprises a plurality of layers, at least one of the plurality of layers being an optical functional sheet layer which includes prisms arranged in parallel along a surface of the optical sheet in such a way that light is transmittable; and light-absorbing portions arranged in parallel between the prisms in such a way as to absorb light, at least another one of the layers being a light diffusing material-containing layer with optical diffusing particles dispersed in a sheet-shaped base material, and the optical sheet satisfying a relation of Nd_K<Nd_R and νd_K<νd_R, wherein Nd_K is a refractive index of the base material of the light diffusing material-containing layer and νd_K is an Abbe number thereof, and Nd_R is a refractive index of the optical diffusing particles and νd_R is an Abbe number thereof.

Claims

1. An optical sheet comprising:

a plurality of layers,

at least one of the plurality of layers being an optical functional sheet layer which includes;

prisms arranged in parallel along a surface of the optical sheet in such a way that light is transmittable; and

light-absorbing portions arranged in parallel between the prisms in such a way as to absorb light,

at least another one of the layers being a light diffusing material-containing layer with optical diffusing particles dispersed in a sheet-shaped base material, and

the optical sheet satisfying a relation of Nd_K<

Nd_R and ν

d_K<

ν

d_R, wherein Nd_K is a refractive index of the base material of the light diffusing material-containing layer and ν

d_K is an Abbe number thereof, Nd_R is a refractive index of the optical diffusing particles and ν

d_R is an Abbe number thereof.

2. The optical sheet according to claim 1, wherein a difference between the refractive indices Nd_K and Nd_R is 0.02 or more and 0.06 or less.

3. The optical sheet according to claim 1, wherein a difference between the Abbe numbers ν

d_K and ν

d_R is 10 or more and 30 or less.

4. The optical sheet according to 1, wherein an average diameter of the optical diffusing particles contained in the light diffusing material-containing layer is 4 μ

m or more and 16 μ

m or less.

5. The optical sheet according to claim 1, wherein the base material of the light diffusing material-containing layer is made of an organic material and the optical diffusing particles are formed of an inorganic material.

6. The optical sheet according to claim 1, wherein a binder made of resin is filled in the light-absorbing portion of the optical functional sheet layer and light absorbing particles having an average diameter of 1 μ

m are dispersed in the binder.

7. The optical sheet according to claim 1, wherein the prisms of the optical functional sheet layer and the light-absorbing portion are formed to extend in a longitudinal direction while maintaining a predetermined cross section, two of the optical functional sheet layers are laminated so that a longitudinal direction of the light-absorbing portion of one of the optical functional sheet layers of the two optical functional sheet layers and a longitudinal direction of the light-absorbing portion of the other optical functional sheet layer of the two optical functional sheet layers have a predetermined angle.

8. The optical sheet according to claim 7, wherein the predetermined angle is 90 degrees.

9. The optical sheet according to any claim 1, wherein the light-absorbing portion of the optical functional sheet layer is formed into a shape of lattices crossing at a predetermined angle.

10. The optical sheet according to claim 9, wherein the predetermined angle is 90 degrees.

11. The optical sheet according to claim 1, wherein the plurality of layers comprises at least one of a base material layer to be used as a base layer of the optical functional sheet layer, an adhesive layer, an antiglare film layer, and a TAC film layer, in addition to the optical functional sheet layer and the light diffusing material-containing layer.

12. The optical sheet according to claim 1, wherein the plurality of layers comprise an anti-glare film layer in addition to the optical functional sheet layer and the light diffusing material-containing layer, and the light diffusing material-containing layer is provided between the optical functional sheet layer and the antiglare film layer.

13. The optical sheet according to claim 1, wherein the light diffusing material-containing layer has an anti-glare function.

14. A display device comprising the optical sheet according to claim 1.