Light pipe and polarized-light source

• US 7,515,339 B2
• Filed: 04/28/2006
• Issued: 04/07/2009
• Est. Priority Date: 05/12/1999
• Status: Expired due to Fees

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Sakuramoto, Takafumi, Miyatake, Minoru
• Primary Examiner(s): Shafer; Ricky D
• Application Number:
  US11/412,909
• Publication Number:
  US 20060193047A1
• Time in Patent Office: 1,075 Days
• Field of Search: 359/494, 359/500, 359/599, 362/19, 362/558, 362/560, 362/615, 362/618, 362/621, 362/624, 362/582, 362/623, 362/625, 349/64, 349/67
• US Class Current: 359/489.2
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• CPC Class Codes: G02B 5/0257 creating an anisotropic diffusion characteristic, i.e. distributing output differently in two perpendicular axes
• 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: G02B 5/0284 used in reflection
• CPC Class Codes: G02B 5/3008 comprising dielectric particles, e.g. birefringent crystals embedded in a matrix
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements

Abstract

A light pipe is obtained by laminating on one or both surfaces of a light-transmitting resin plate a polarized-light scattering plate having fine birefringent domains dispersed therein and hence showing anisotropy in scattering. The polarized-light scattering plate comprises a transparent film having fine domains dispersed therein comprising a liquid crystal polymer which exhibits nematic at temperatures lower than the glass transition temperature of the polymer constituting matrix of the transparent film and has a glass transition temperature of 50° C. or higher. The light pipe as a laminate may further comprise a specular reflection layer, a polarization-retaining lens and a light diffusion layer laminated thereon. The light pipe may further comprise a light source mounted at least on one side face thereof to provide a planar polarized-light source.

Claims

1. A light pipe comprising:

a laminate having a light-transmitting resin plate, and a polarized-light scattering plate laminated on at least one surface of said light-transmitting resin plate, such that said polarized-light scattering plate is disposed outside of an area occupied by said light-transmitting resin plate, said polarized-light scattering plate having fine birefringent domains dispersed therein to exhibit anisotropy in scattering depending on a polarization direction;

a specular reflection layer provided on a first surface of said laminate; and

a polarization-retaining light diffusion layer provided on a second surface of said laminate,

wherein said light-transmitting resin plate is disposed between said polarized-light scattering plate and said polarization-retaining light diffusion layer,

wherein said polarized-light scattering plate is a continuous plate that extends along the entire length of said light-transmitting resin plate, and

wherein said light diffusion layer comprises an optically isotropic light-transmitting resin layer having transparent particles of a refractive index ratio of from 0.9 to 1.1 dispersed therein.

2. A light pipe according to claim 1, wherein said optically isotropic light-transmitting resin is at least one of cellulose triacetate-based resin, methyl polymethacrylate, polycarbonate and norbornene-based resin.

3. A polarized-light source comprising:

a light pipe according to claim 1; and

a light source disposed at least on one side face of said light pipe.

4. A light pipe according to claim 1, wherein said polarized-light scattering plate is separated from said light-transmitting resin plate by a layer of adhesive.

5. A light pipe according to claim 4, wherein said light-transmitting resin plate and said polarized-light scattering plate do not contact each other.

6. A light pipe according to claim 1, further including a light source, a portion of said light source being aligned along a longitudinal direction of said polarized-light scattering plate.

7. A light pipe according to claim 6, wherein a portion of said light source is aligned along a longitudinal direction of said light-transmitting resin plate.

8. A light pipe according to claim 7, further including a reflector, wherein said reflector is extended in a longitudinal direction of said light-transmitting resin plate and said polarized-light scattering plate.

9. A light pipe according to claim 1, wherein said polarized-light scattering plate is positioned between said light-transmitting resin plate and said specular reflection layer, and said light-transmitting resin plate and said polarized-light scattering plate do not contact each other.

10. A light pipe according to claim 1, wherein said polarized-light scattering plate being disposed on an outside surface of said light-transmitting resin plate, such that no open gap exists between said light-transmitting resin plate and said polarized-light scattering plate.

11. A light pipe according to claim 10, wherein said light-transmitting resin plate and said polarized-light scattering plate are bonded to each other by a layer of adhesive.

12. A light pipe according to claim 1, wherein said polarized-light scattering plate is a single plate which substantially overlaps the entire outside surface of said light-transmitting resin plate.

13. A light pipe according to claim 1, wherein said polarized-light scattering plate is a single continuous plate which substantially overlaps the entire outside surface of said light-transmitting resin plate.

14. A light pipe according to claim 13, wherein said polarized-light scattering plate extends along the entire length and the entire width of said light-transmitting resin plate.