THERMAL CONVECTION FLOW LIGHT VALVE

• US 3,788,729 A
• Filed: 04/28/1972
• Issued: 01/29/1974
• Est. Priority Date: 04/28/1972
• Status: Expired due to Term

• Current Assignee: Research Frontiers Incorporated
• Original Assignee: Francis C. Lowell, Matthew Forline, Paul Rosenberg, Robert L. Saxe
• Inventors: Lowell, Francis C., Rosenberg, Paul, Saxe, Robert L., Forline, Matthew
• Primary Examiner(s): Wibert, Ronald L.
• Assistant Examiner(s): McGraw, V. P.
• Application Number:
  US05/248,479
• Time in Patent Office: 641 Days
• Field of Search: 350/147,150,16R,267
• US Class Current: 359/296
• CPC Class Codes: G02F 1/172 based on a suspension of orientable dipolar particles, e.g. suspended particles displays

Abstract

A light valve includes a cell containing a fluid capable of being acted upon by an electric or magnetic field, or both, to change the transmission of light through the fluid, and means for applying such a field thereto. Specifically described is a fluid suspension of minute particles acted upon by an electric field. An external or internal conduit connects opposite edge portions of the cell and heat is applied to the fluid in the cell or conduit to produce a thermal convection flow of the fluid through the cell and conduit.

Claims

1. A light valve including a cell for containing a fluid capable of being acted upon by an electric or magnetic field, or both, to change the transmission of light through the fluid, said cell having spaced wall sections, and means for applying a respective electric or magnetic field, or both, to the fluid between said spaced wall sections to change the light transmission thereof, in which the improvement comprises conduit means for connecting substantially opposite edge portions of said cell, at least one of said conduit means and cell having a portion thereof extending in a direction having a substantial vertical component, and means for producing a thermal gradient in the fluid in said portion having a substantial vertical component to produce a flow of the fluid through said cell.

2. A light valve including a cell containing a fluid suspension of minute particles dispersed therein capable of being acted upon by an electric field to change the transmission of light through the suspension, said cell having wall sections spaced apart a distance which is small compared to the lateral dimensions of the sections to confine the fluid suspension therebetween to a layer, and area electrodes on opposite sides of said layer for producing an electric field through the layer to change the light transmission thereof, in which the improvement comprises conduit means for connecting substantially opposite edge portions of said cell, at least one of said conduit means and cell having a portion thereof extEnding in a direction having a substantial vertical component, and means for producing a thermal gradient in the fluid suspension in said portion having a substantial vertical component to produce a flow of the fluid suspension in said layer.

3. A light valve according to claim 2 in which the spacings of the walls of said cell at said opposite edge portions connected by said conduit means are substantially greater than the spacing of the wall sections in the region of said layer, thereby forming channels at opposite edges of said layer.

4. A light valve according to claim 3 in which a portion of said conduit means extends in a direction having a substantial vertical component, said means for producing a thermal gradient in the fluid suspension including heating means operatively associated with said portion of the conduit means for heating the fluid suspension therein.

5. A light valve according to claim 3 in which said cell extends in a direction having a substantial vertical component and said channels are at upper and lower edges of said layer, and including heating means for heating a region of said cell extending laterally of the cell near the bottom thereof to produce said temperature gradient.

6. A light valve according to claim 3 in which said cell extends in a direction having a substantial vertical component and said channels are at upper and lower edges of said layer, and including means for subjecting at least a portion of the fluid suspension in said layer and at least a portion of said conduit means to different ambient temperatures to thereby produce said temperature gradient.

7. A light valve according to claim 3 in which said cell extends in a direction having a substantial vertical component, said channels are at upper and lower edges of said layer, and said conduit means is a conduit of heat-transmitting material positioned exteriorly of said cell and connecting said channels, and means for subjecting at least a portion of said cell and at least a portion of said conduit to different ambient temperatures to thereby produce said temperature gradient.

8. A light valve according to claim 3 in which said cell extends in a direction having a substantial vertical component and said channels are at upper and lower edges of said layer, said conduit means comprising a barrier wall between the walls of said cell on one side of the region of said layer, said barrier wall being spaced from the corresponding side of the cell and spaced from the top and bottom of the cell to form a conduit between said upper and lower channels of the cell, the spacing of the walls of the cell between said barrier wall and the corresponding side of the cell being substantially greater than the spacing of the wall sections in the region of said layer.

9. A light valve according to claim 8 in which said means for producing a temperature gradient comprises electric heating means for heating the fluid suspension in said conduit.

10. A light valve according to claim 8 in which said means for producing a temperature gradient comprises electric heating means extending laterally of said cell below said area electrodes.

11. A light valve according to claim 10 in which said electric heating means comprises an electrical resistive coating on the inner surface of at least one of the walls of the cell below the area electrode on the respective wall and insulated therefrom.

12. A light valve according to claim 3 in which said cell extends in a direction having a substantial vertical component and said channels are at upper and lower edges of said layer, said conduit means comprising a pair of barrier walls between the walls of said cell on respectively opposite sides of the region of said layer, said barrier walls being spaced from the respective sides of the cell and spaced from the top and bottom of the cell to form a pair of conduits between said upper and lower channels of the cell, the spacing of the walls of the cell between said barrier walls and the respective sidEs of the cell being substantially greater than the spacing of the wall sections in the region of said layer.

13. A light valve according to claim 12 in which said means for producing a temperature gradient comprises electric heating means for heating the fluid suspension in each of said conduits.

14. A light valve according to claim 3 in which said cell and at least a portion of said conduit means are at different vertical levels with a portion of the conduit means extending in a direction having a substantial vertical component, and said channels are at horizontally separated edges of said layer.

15. A light valve according to claim 14 in which said means for producing a thermal gradient includes heating means operatively associated with said portion of the conduit having a substantial vertical component.

16. A light valve according to claim 14 in which said cell is at a lower vertical level than a portion of said conduit means, and said means for producing a thermal gradient includes heating means operatively associated with one of said channels for heating the fluid suspension therein.

17. A light valve according to claim 16 in which said heating means comprises an electrical heating element in said one channel, and including a barrier wall in said one channel positioned between said heating element and the adjacent edge of said layer and spaced from the adjacent edge of the layer, one end of said barrier wall being spaced from the adjacent edge of the cell to allow flow of the fluid suspension thereby.

18. A light valve according to claim 15 in which said cell is disposed generally horizontally and said flow of the fluid suspension in said layer is in a generally horizontal direction.

19. A light valve including a cell for containing a fluid capable of being acted upon by an electric or magnetic field, or both, to change the transmission of light through the fluid, said cell having spaced wall sections and means for applying a respective electric or magnetic field, or both, to the fluid between said spaced wall sections to change the light transmission thereof, in which the improvement comprises means for producing a thermal gradient in the fluid to produce a flow of the fluid through said cell when said fluid is being acted upon by said electric or magnetic field or both.

20. The light valve of claim 19 wherein the fluid is a fluid suspension.

21. A light valve including a cell for containing a fluid capable of being acted upon by an electric or magnetic field, or both, to change the transmission of light through the fluid, said cell having spaced wall sections and means for applying a respective electric or magnetic field, or both, to the fluid between said spaced wall sections to change the light transmission thereof, in which the improvement comprises means for producing a thermal gradient in the fluid to produce a flow of the fluid through said cell in a defined path to prevent significant agglomeration in the fluid.

22. The light valve of claim 21 wherein the fluid is a fluid suspension.

23. The method of preventing significant agglomeration in a fluid suspension in a light valve wherein the light valve includes a cell for containing the fluid suspension which is capable of being acted upon by an electric or magnetic field, or both, to change the transmission of light through the fluid suspension comprising the steps of producing a thermal gradient in the fluid suspension when said fluid suspenson is being acted upon by the electric or magnetic field or both and causing a flow of the fluid suspension through the cell by means of the thermal gradient.

24. The method of preventing significant agglomeration in a fluid suspension in a light valve wherein the light valve includes a cell for containing the fluid suspension which is capable of bring acted upon by an electric or magnetic field, or both, to change the transmission of light through the fluid suspension comprising the steps of producing a thermal gradient in the fluid suspEnsion and causing a flow of the fluid suspension through the cell in a defined path by means of the thermal gradient.