Light pipe and polarized-light source

• US 20070014007A1
• Filed: 04/28/2006
• Published: 01/18/2007
• Est. Priority Date: 05/12/1999
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Sakuramoto, Takafumi, Miyatake, Minoru
• Granted Patent: US 7,532,398 B2
• Time in Patent Office: Days
• US Class Current: 359/494
• 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 birefringent 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 having fine birefringent domains dispersed therein to exhibit anisotropy in scattering depending on a polarization direction; and

a specular reflection layer provided on one surface of said laminate.

2. A light pipe according to claim 1, wherein a phase difference due to birefringence of the light-transmitting resin plate is 50 nm or more based on an average phase difference in a plane of said light-transmitting resin plate.

3. A light pipe according to claim 2, wherein a retardation axis of the light-transmitting resin plate and a light axis of the polarized-light scattering plate in the laminate cross each other at an angle of 5 degrees or more.

4. 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.