Broadband switchable polarizer

• US 6,473,143 B2
• Filed: 06/05/1998
• Issued: 10/29/2002
• Est. Priority Date: 11/27/1991
• Status: Expired due to Fees

• Current Assignee: Reveo, Inc.
• Original Assignee: Reveo, Inc.
• Inventors: Li, Le, Jiang, Yingqiu, Fan, Bunsen, Faris, Sadeg, Li, Jian-feng
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): NGUYEN, DUNG T
• Application Number:
  US09/093,017
• Publication Number:
  US 20020039156A1
• Time in Patent Office: 1,607 Days
• Field of Search: 349/88, 349/185, 349/86, 349/96, 349/112, 349/113
• US Class Current: 349/88
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: C09B 67/0098 Organic pigments exhibiting interference colours, e.g. nacrous pigments
• CPC Class Codes: C09D 11/037 characterised by the pigment
• CPC Class Codes: C09D 11/17 characterised by colouring agents
• CPC Class Codes: C09K 19/00 Liquid crystal materials
• CPC Class Codes: C09K 19/52 characterised by components which are not liquid crystals, e.g. additives with special physical aspect: solvents, solid particles
• CPC Class Codes: E06B 2009/2464 featuring transparency control by applying voltage, e.g. LCD, electrochromic panels
• CPC Class Codes: E06B 9/24 Screens or other constructions affording protection against light, especially against sunshine; Similar screens for privacy or appearance; Slat blindsoperating, guiding or securing devices or arrangements for roll-type closures E06B9/56; free-hanging flexible screens A47H23/00
• CPC Class Codes: F24S 50/80 for controlling collection or absorption of solar radiation
• CPC Class Codes: G01D 11/28 Structurally-combined illuminating devices
• CPC Class Codes: G02B 27/0093 with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking
• 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: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/133514 Colour filters
• 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 1/133621 providing coloured light G02F1/133617, G02F1/133533 take precedence
• CPC Class Codes: G02F 1/13471 in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells G02F1/13475 takes precedence
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal
• CPC Class Codes: G02F 1/1393 : the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• CPC Class Codes: Y02E 10/40 : Solar thermal energy, e.g. solar towers

Abstract

A light controlling film is disclosed, comprising a polymerized polymer network varying spatially in a direction normal to the film surface, where the polymerized polymer network is a crosslinked high molecular weight polymeric material mixed with a low molecular weight nematic material exibiting cholesteric liquid crystal (CLC) order, wherein wherein an electric field impressed in the film controls the reflection of circularly polarized light.

Claims

1. A light controlling film, the film having a first surface and a second surface, comprising:

a polymerized polymer network, the polymer network varying spatially in a direction normal to the first surface, the polymerized polymer network comprising;

crosslinked high molecular weight polymeric material; and

low molecular weight polymeric material,

wherein the high molecular weight polymeric material and the low molecular weight polymer material form a material having cholesteric liquid crystal (CLC) order, the CLC order oriented with respect to the first and the second surfaces, the pitch of the CLC order varying non-linearly in a direction perpendicular to the first surface,

wherein light having a first polarization and a broad bandwidth incident on the first surface is substantially reflected from the film, and wherein light having a second polarization and the broad bandwidth incident on the first surface is not substantially reflected from the film, and wherein an electric field impressed in the film controls the reflection of light having the first polarization when the electric field has a component in a direction normal to the first surface; and

wherein the crosslinked high molecular weight polymeric material is less than 20% by weight of the film.

2. The light controlling film of claim 1, wherein the crosslinked high molecular weight polymeric material is less than 15% by weight of the film.

3. The light controlling film of claim 2, wherein the crosslinked high molecular weight polymeric material is less than 10% by weight of the film.

4. The light controlling film of claim 1, further comprising electrically conducting material adjacent to the first surface for impressing an electric field in the film, the electrically conducting material transmitting the light having the broad bandwidth and the first polarization.

5. The apparatus of claim 4, further comprising a second electrically conducting material adjacent to the second surface, wherein a voltage applied between the first and the second electrically conducting material impresses an electric field on in the film.

6. The apparatus of claim 5, wherein the second electrically conducting material transmits light having the first bandwidth.

7. The apparatus of claim 5, wherein the first polarization is a circular polarization.

8. The apparatus of claim 7, further comprising a quarter wave retardation plate transparent to light having the first bandwidth in close proximity to the first surface, whereby linearly polarized light incident on the transparent quarter wave retardation plate is controllably reflected.

9. The apparatus of claim 4, further comprising a means for applying an electric field in the film, the electric field varying spatially over the first surface, whereby polarized light is controllably reflected for display purposes.

10. The apparatus of claim 4, further comprising a means for applying an electric field in the film, the electric field having a controllable bias field and a controllable adjustment field, whereby the reflectivity of polarized light may be substantially changed by changing the controllable adjustment field.

11. The apparatus of claim 4, further comprising optical communication means, whereby the light in the optical communication means is controlled.

12. The apparatus of claim 4, further comprising means for directing light on to the first surface, and means for receiving reflected light from the first surface, whereby polarized light with a controllable bandwidth produced in the means for receiving reflected light.

13. The apparatus of claim 4, further comprising laser cavity means, whereby the output of the laser cavity means is controlled by the film when the film is used as a reflective element in the laser cavity.

14. The apparatus of claim 4, further comprising a transparent quarter wave retardation plate in close proximity to the first surface, whereby linearly polarized light incident on the transparent quarter wave retardation plate is controllably reflected.

15. A method of making a light controlling film, the film having a first surface and a second surface, comprising:

applying a mixture of high molecular weight polymeric material and low molecular weight polymeric material on a surface which produces a CLC order in the mixture; and

crosslinking the high molecular weight polymeric material so that the low molecular weight material significantly diffuses throughout the film and remains distributed in a non uniform fashion across the film from the first surface to the second surface;

wherein light having a first polarization and a broad bandwidth incident on the first surface is substantially reflected from the film, and wherein light having a second polarization and the broad bandwidth incident on the first surface is not substantially reflected from the film, wherein an electric field impressed in the film substantially decreases the reflection of light of the first polarization and broad bandwidth, and

wherein the step of crosslinking takes place in a time t₁, long compared to the time t₂ in which the low molecular weight material can significantly diffuse.

16. The method of claim 15, wherein the step of crosslinking takes place includes irradiation of the film by low intensity ultraviolet radiation.

17. The method of claim 16, wherein the step of crosslinking takes place includes irradiation of the film by high intensity ultraviolet radiation having a radiation intensity of less than 1 mw/cm².

18. The method of claim 15, wherein the step of crosslinking takes place includes irradiation of the film by high energy electrons where the electron where the electron energy deposition varies substantially throughout the film.

19. The method of claim 15, wherein the step of crosslinking takes place includes irradiation of the film by light which is substantially nonuniformly absorbed throughout the film.

20. The method of claim 15, wherein the step of crosslinking takes place includes heating the film substantially nonuniformly across the film.