Brightness enhancing reflective polarizer

• US 7,038,745 B2
• Filed: 02/19/2003
• Issued: 05/02/2006
• Est. Priority Date: 12/21/1993
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Cobb, Sanford Jr., Weber, Michael F., Ouderkirk, Andrew J., Stover, Carl A., Benson, Olester Jr., Jonza, James M., Wortman, David L.
• Primary Examiner(s): Parker, Kenneth
• Application Number:
  US10/369,014
• Publication Number:
  US 20030164914A1
• Time in Patent Office: 1,168 Days
• Field of Search: 354496-498, 359/487, 349/105, 349/114, 349/96, 349/98, 349/62
• US Class Current: 349/96
• CPC Class Codes: A47J 36/28 Warming devices generating the heat by exothermic reactions, e.g. heat released by the contact of unslaked lime with water
• CPC Class Codes: B29C 55/023 using multilayered plates or sheets
• CPC Class Codes: B29D 11/00 Producing optical elements, e.g. lenses or prisms grinding or polishing of optical elements B24B; constructional form of optical elements G02B; optical parts of spectacles G02C7/00
• CPC Class Codes: B29K 2995/003 Reflective
• CPC Class Codes: B29K 2995/0034 Polarising
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: B32B 7/023 Optical properties
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• 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 5/305 including organic materials, e.g. polymeric layers
• 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 1/133507 Films for enhancing the luminance
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one

Abstract

A multiple layer reflective polarizer 12 is described. This element is placed between and optical cavity 24 and an LCD module 16 to form an optical display. The reflective polarizer reflects some light into the optical cavity 24 where it is randomized and may ultimately emerge with the correct polarization to be transmitted out of the display.

Claims

1. A brightness enhancing reflective polarizer comprising:

a reflective polarizer adapted to transmit incident light that has a first polarization and to reflect light, incident at angles normal to the reflective polarizer and at relatively large angles from the normal, that has a second polarization; and

a structured surface material adjoined to the reflective polarizer adapted to redirect light incident at relatively large angles from the normal of the reflective polarizer toward the normal.

2. The brightness enhancing device of claim 1, wherein the reflective polarizer comprises a birefringent material arranged to produce interference reflections for light of the second polarization.

3. The brightness enhancing device of claim 2, wherein the reflective polarizer comprises a stack of at least two layers, wherein at least one of the layers has the birefringent material and at least one of adjacent layers has a different refractive index than the birefringent material along at least one axis.

4. A brightness enhancing device of claim 3, wherein a difference in refractive indices of the two layers along a second axis orthogonal to the first axis is essentialy zero.

5. The brightness enhancing device of claim 1, wherein the reflective polarizer has an average transmission of at least 60% for light having the first polarization and incident at 60°

from the normal to the reflective polarizer.

6. The brightness enhancing device of claim 1, wherein the structured surface material comprises a linear array of structures.

7. The brightness enhancing device of claim 6, wherein the linear arry of structures comprises prisms having peak angles in the range of 70 to 110 degrees.

8. The brightness enhancing device of claim 1, wherein the structured surface material comprises diffractive or holographic optical elements.