Polarization component, polarization light source and image display apparatus using the same

• US 7,982,952 B2
• Filed: 05/17/2010
• Issued: 07/19/2011
• Est. Priority Date: 04/23/2002
• Status: Expired due to Fees

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Hara, Kazutaka, Miyatake, Minoru
• Primary Examiner(s): Shafer; Ricky D
• Application Number:
  US12/781,398
• Publication Number:
  US 20100226007A1
• Time in Patent Office: 428 Days
• Field of Search: 359/487, 359/495, 359/501, 359/485.01, 359/487.04, 359/489.07, 359/490.01, 349/96, 349/117
• US Class Current: 359/485.01
• CPC Class Codes: G02B 5/3016 involving passive liquid crystal elements optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528
• CPC Class Codes: G02B 5/3025 Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state G02B5/3008, G02B5/3016 take precedence
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133543 Cholesteric polarisers
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 1/133634 the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis
• CPC Class Codes: H10K 50/86 Arrangements for improving contrast, e.g. preventing reflection of ambient light
• CPC Class Codes: H10K 59/8791 Arrangements for improving contrast, e.g. preventing reflection of ambient light

Abstract

A polarization component, capable of efficiently reflecting an obliquely transmitted light beam toward a light source without degrading the transmission-polarization property of a perpendicular incident light beam, is provided. A C-plate having an oblique retardation of at least λ/8 with respect to a light beam inclined by at least 30° is disposed between at least two reflective circular polarizer layers whose selective reflection wavelength bands of polarized light overlapping each other. A combination of a reflective linear polarizer and a quarter wavelength plate may be used instead of the reflective circular polarizer. Alternatively, a combination of two reflective linear polarizer layers and two quarter wavelength plate layers (Nz≧2) disposed therebetween can provide a similar effect. Further, a combination of two reflective linear polarizer layers and a half wavelength plate (Nz≧1.5) disposed therebetween may be used. When reflective linear polarizer layers are used, they must be bonded together with their axial directions set at a certain angle. The polarization component is preferably used in various image display apparatuses such as liquid crystal display apparatuses and organic EL display apparatuses.

Claims

1. A polarization component comprising, at least, two reflective polarizer layers and an intermediate layer disposed between the reflective polarizer layers, wherein

the two reflective polarizer layers are reflective linear polarizer layers that selectively transmit one of linearly polarized light beams crossing each other at right angles while selectively reflecting the other one of said linearly polarized light beams,

the two reflective linear polarizer layers have selective reflection wavelength bands for selective reflection of polarized light, the bands overlapping each other at least partially,

the intermediate layer comprises a single optical layer or a laminate of at least two optical layers, and the intermediate layer has a function of transmitting an incident linearly polarized light beam while changing or not changing a polarization direction, according to an incidence direction,

the two reflective linear polarizer layers are disposed at an angle so as to have in-plane slow axis directions for transmitting a light beam that is included in incident linearly polarized light and that enters in a direction perpendicular to the incidence surface while efficiently reflecting a light beam entering from an oblique direction.

2. The polarization component according to claim 1, wherein the overlapping region of the selective reflection wavelength bands in the two reflective linear polarizer layers comprises a wavelength range of 540 to 560 nm.