Siloxane matrix polymers and SPD light valve films incorporating same

• US 6,900,923 B2
• Filed: 06/18/2003
• Issued: 05/31/2005
• Est. Priority Date: 06/18/2003
• Status: Active Grant

• Current Assignee: Research Frontiers Incorporated
• Original Assignee: Research Frontiers Incorporated
• Inventors: Chakrapani, Srinivasan, Slovak, Steven M.
• Primary Examiner(s): Ben, Loha
• Assistant Examiner(s): Dinh, Jack
• Application Number:
  US10/465,489
• Publication Number:
  US 20040257634A1
• Time in Patent Office: 713 Days
• Field of Search: 359/296, 359/253, 359/452, 345/105, 345/107, 345/108, 356/441, 525/176, 428/1.31, 428/1.5, 428/448, 606/192, 252/572, 252/582, 252/583, 252/585, 522/71, 522/99, 522/148, 522/172
• US Class Current: 359/296
• CPC Class Codes: C09K 2323/031 Polarizer or dye
• CPC Class Codes: C09K 2323/05 Bonding or intermediate layer characterised by chemical composition, e.g. sealant or spacer
• CPC Class Codes: G02B 26/026 based on the rotation of particles under the influence of an external field, e.g. gyricons, twisting ball displays based on orientable dipolar particles G02F1/172; based on electrophoresis G02F1/167
• CPC Class Codes: G02F 1/172 based on a suspension of orientable dipolar particles, e.g. suspended particles displays

Abstract

A film suitable for use as a light-modulating unit of a suspended particle device (SPD) light valve. The film comprises a siloxane matrix polymer which has a refractive index>1.4630 and has droplets of a liquid light valve suspension distributed within the matrix. The liquid light valve suspension preferably comprises a polyalkyl (meth)acrylate and/or fluorinated (meth)acrylate suspending polymer and optionally may comprise one or more non-polymeric liquids.

Claims

1. A film suitable for use as a light-modulating unit of a suspended particle device (SPD) light valve, said film comprising a matrix polymer material and having droplets of a liquid light valve suspension distributed within the matrix, wherein said matrix polymer material is siloxane-based and has a refractive index (RI) of >

1.4630.

2. The film according to claim 1, wherein the matrix polymer material is cross-linked in forming said film to produce a cross-linked polymer matrix.

4. The film according to claim 2 or 3, wherein the matrix polymer material further comprises a photoinitiator to facilitate curing of said film by ultraviolet radiation.

5. The film according to claim 4, wherein the photoinitiator is selected from the group consisting of alphahydroxyketones and their blends, alphaamino-ketones, benzyldimethyl-ketals, acylphosphine oxides and their blends, metallocenes, benzoylformate esters, benzoin ethers, benzophenones and mixtures thereof.

6. The film according to claim 1 or 3 wherein the polymer matrix comprises a siloxane matrix polymer which is substantially immiscible with the liquid light valve suspending medium.

7. The film according to claim 6, wherein the siloxane matrix polymer has a refractive index in the range 1.4700 to 1.4750.

8. The film according to claim 7, wherein the siloxane matrix polymer has a refractive index of 1.4717.

9. A light valve comprising a pair of opposed spaced-apart cell walls, and a light modulating element between said cell walls, wherein said light modulating unit comprises the film according to claim 1 or claim 3.

3. A film suitable for use as a light-modulating unit of a suspended particle device (SPD) light valve, said film comprising a matrix polymer material, which matrix polymer material has an RI of >

1.4630 and is cross-linked in forming said film to produce a cross-linked polymer matrix, and having droplets of a liquid light valve suspension medium distributed within the cross-linked matrix, wherein said liquid light valve suspension medium comprises a polyalkyl (meth)acrylate and/or fluorinated (meth)acrylate suspending polymer.

10. An electro-optical device for controlling the transmission of radiation, said device comprising a cell formed of opposed cell walls, a light modulating element between said cell walls, and opposed electrode means operatively associated with said cell walls, said light modulating element comprising a film, said film comprising a siloxane matrix polymer of >

1.4630 RI and having droplets of a liquid light valve suspension distributed within the matrix, said electrode means adapted for applying an electrical field across said suspension, wherein said liquid light valve suspension comprises a polymer selected from the group consisting of a polyalkyl (meth)acrylate polymer, a fluorinated (meth)acrylate polymer and mixtures thereof.

11. The electro-optical device according to claim 10, wherein said matrix polymer material is cross-linked in forming said film to produce a cross-linked polymer matrix.

12. The electro-optical device according to claim 10 or 11 wherein the polymer matrix comprises a siloxane matrix of >

1.4630 RI which is substantially immiscible with the liquid light valve suspending medium.

13. The electro-optical device according to claim 12, wherein the siloxane matrix polymer has a refractive index in the range of 1.4700 to 1.4750.

14. The electro-optical device according to claim 13, wherein the siloxane matrix polymer has a refractive index of 1.4717.

15. The electro-optical device according to claim 12, wherein the matrix polymer material further comprises a photoinitiator to facilitate curing of said film by ultraviolet radiation.

16. The electro-optical device according to claim 15, wherein the photoinitiator is selected from the group consisting of alphahydroxyketones and their blends, alphaamino-ketones, benzldimethyl-ketals, acylphosphine oxides and their blends, metalocenes, benzoylformate esters, benzoin ethers, benzophenones and mixtures thereof.

17. A method of preparing a film suitable for use as a light-modulating unit of a suspended particle device light valve, the method comprising:

preparing a quantity of a siloxane matrix polymer material;

forming an emulsion from the combination of at least a portion of the siloxane matrix polymer material of >

1.4630 RI and a quantity of a liquid light valve suspension, said suspension comprising a plurality of particles suspended in a liquid light valve suspending medium, wherein the liquid light valve suspension comprises a polyalkyl (meth)acrylate, a fluoro (meth)acrylate suspending polymer or a mixture thereof; and

cross-linking the polymer matrix to substantially solidify the matrix polymer and produce a film having droplets of the liquid light valve suspension distributed in the cross-linked polymer matrix.

18. The method according to claim 17, wherein the polymer matrix is cross-linked by exposing said matrix polymer emulsion to a sufficient amount of heat or radiation for a sufficient duration to at least substantially convert said emulsion to a film.

19. The method according to claim 18, where said radiation is electron beam radiation or ultraviolet radiation.

20. The method according to claim 19, wherein said polymer matrix is cross-linked by exposure to ultraviolet radiation and wherein the method further comprises adding a photonitiator to the emulsion to facilitate cross-linking of said polymer matrix.

21. The method according to claim 20, wherein the photoinitiator is selected from the group consisting of alphahydroxyketones and their blends, alphaamino-ketones, benzldimethyl-ketals, acylphosphine oxides and their blends, metalocenes, benzoylformate esters, benzoin ethers, benzophenones and mixtures thereof.

22. The method according to claim 18, where said heat cross-linking further comprises adding a free radical initiator to the emulsion to facilitate cross-linking of said polymer matrix.