Light pipe and polarized-light source

• US 7,446,938 B2
• Filed: 04/28/2006
• Issued: 11/04/2008
• 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:
  US11/412,908
• Publication Number:
  US 20060215265A1
• Time in Patent Office: 921 Days
• Field of Search: 359/492, 359/500, 359/599, 362/19, 362/606, 362/615, 362/618, 362/620, 362/623, 362/558, 362/560, 362/617, 362/619, 362/624, 362/627, 362/629, 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, 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, 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 lens sheet provided on a second surface of said laminate,

wherein said light-transmitting resin plate and said polarized-light scattering plate are bonded to each other.

2. A light pipe according to claim 1, wherein said lens sheet comprises one or more resins having a low birefringence.

3. A light pipe according to claim 1, wherein said lens sheet comprises at least one of a cellulose triacetate-based resin, methyl polymethacrylate, polycarbonate and norbornene-based resin.

4. A light pipe according to claim 1, wherein said lens sheet has a linear or dotted roughened structure provided on one surface thereof.

5. A light pipe according to claim 4, wherein said lens sheet has a linear roughened structure and a linear direction is parallel to or perpendicular to a light axis of the polarized-light scattering plate.

6. A light pipe according to claim 1, further comprising a polarization-retaining light diffusion layer provided between said lens sheet and said laminate or on an emission side of said lens sheet.

7. A polarized-light source comprising:

a light pipe according to claim 1, wherein said light source is disposed on one side face of said light pipe.

8. A light pipe according to claim 1, wherein said polarized-light scattering plate is a continuous plate that extends along the entire length of said light-transmitting resin plate.

9. A light pipe according to claim 8, wherein said polarized-light scattering plate is a single continuous plate which substantially overlaps the entire outside surface of said light-transmitting resin plate.

10. A light pipe according to claim 9, wherein said polarized-light scattering plate extends along the entire length and the entire width of said light-transmitting resin plate.

11. A light pipe according to claim 1, wherein a portion of said light source is aligned along a longitudinal direction of said polarized-light scattering plate.

12. A light pipe according to claim 11, wherein a portion of said light source is aligned along a longitudinal direction of said light-transmitting resin plate.

13. A light pipe according to claim 12, wherein said reflector is extended in a longitudinal direction of said light-transmitting resin plate and said polarized-light scattering plate.

14. 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.

15. 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.