AUTOMATIC DARKENING AND GLARE REDUCING LIQUID CRYSTAL MIRROR

• US 20100026917A1
• Filed: 12/23/2008
• Published: 02/04/2010
• Est. Priority Date: 08/04/2008
• Status: Active Grant

• Current Assignee: Opti-Source, LLC
• Original Assignee: Opti-Source, LLC
• Inventors: Wen, Walter Y., Hines, Robin, Chang, C.T.
• Granted Patent: US 8,446,550 B2
• Time in Patent Office: Days
• US Class Current: 349/1
• CPC Class Codes: B60R 1/088 using a cell of electrically changeable optical characteristic, e.g. liquid-crystal or electrochromic mirrors
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/13318 Circuits comprising a photodetector
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/133555 Transflectors
• CPC Class Codes: G02F 1/13725 based on guest-host interaction G02F1/13762, G02F1/13737, take precedence

Abstract

An automatic darkening and glare reducing liquid crystal mirror for vehicles is disclosed. The mirror has a front substrate (101) of transparent glass or plastic and a back substrate (109) of glass or plastic with a highly reflective or transflective mirrored coating (108). The front and back substrates are spaced apart a small distance to define a liquid crystal cell between the substrates and a liquid crystal fluid (106) incorporating dichroic dyes is contained within the liquid crystal cell. A conductive thin film (102) is applied onto the interior surface of the front substrate and the reflective or transflective coating (108) of the back substrate also is conductive. An alignment compound is deposited on the conductive thin film (102) and on the reflective or transflective coating (108) and the alignment compound bounds the liquid crystal cell. An electronic control circuit is adapted to apply selectively a voltage signal to the conductive thin film and the reflective or transflective coating (108) to affect the transmittance of the liquid crystal fluid, and thereby the darkness of the mirror. The nature of the alignment compound determines a home or rest alignment of the liquid crystal molecules, either parallel or perpendicular to the substrates, and thus determines whether the mirror is normally dark (a “dark mode” mirror) or normally bright (a “bright mode” mirror). Application of a voltage signal to a dark mode mirror lightens it while application of a voltage signal to a bright mode mirror darkens the mirror. A headlight sensor (302) and an ambient sensor (301) are coupled to the electronic control circuit and the circuit is configured to darken the mirror in response to signals from the sensors indicating that the ambient light intensity is below a predetermined threshold (equivalent to nighttime) and the intensity of light from headlights impinging on the mirror is above a predetermined threshold (equivalent to a glare condition).

Claims

1. A liquid crystal mirror comprising:

a substantially transparent front substrate having interior and exterior surfaces;

a reflective back substrate having interior and exterior surfaces and being spaced from the front substrate to define a cell between the interior surfaces of the substrates; and

a liquid crystal fluid contained in the cell.

2. A liquid crystal mirror as claimed in claim 1 and further comprising dichroic dye molecules incorporated into the liquid crystal fluid.

3. A liquid crystal mirror as claimed in claim 1 and wherein the interior surface of the back substrate is coated with a reflective material or a transflective material.

4. A liquid crystal mirror as claimed in claim 3 and wherein the reflective material or the transflective material is selected from a group consisting of silicon-oxides, titanium-oxide, silver, aluminum, enhanced aluminum, and chrome.

5. A liquid crystal mirror as claimed in claim 3 and wherein the reflective material or the transflective material is conductive and further comprising a conductive thin film on the interior surface of the front substrate, the reflective material or transflective material and the conductive thin film forming electrodes on opposite sides of the cell.

6. A liquid crystal mirror as claimed in claim 5 and further comprising an alignment compound on opposite sides of and bounding the cell.

7. A liquid crystal mirror as claimed in claim 6 and further comprising a control circuit coupled to the electrodes for selectively applying a voltage signal to the electrodes, the voltage signal causing an electric field that affects the liquid crystal fluid to change the reflectivity of the mirror.

8. A liquid crystal mirror as claimed in claim 7 and wherein the alignment compound is configured to cause molecules within the liquid crystal fluid to align substantially parallel with the interior surfaces of the top and bottom substrates when no voltage signal is applied to the electrodes.

9. A liquid crystal mirror as claimed in claim 7 and wherein the alignment compound is configured to cause molecules within the liquid crystal fluid to align substantially perpendicular to the interior surfaces of the top and bottom substrates when no voltage signal is applied to the electrodes.

10. A liquid crystal mirror as claimed in claim 1 and further comprising at least one display incorporated into and visible through the mirror.

11. A liquid crystal mirror as claimed in claim 10 and wherein the display is selected from the group consisting of a temperature display, a compass display, a clock display, a bluetooth display, a garage opener display, a tire pressure display, an information display, a global positioning satellite display, a back-up camera display, and combinations thereof.

12. A liquid crystal mirror as claimed in claim 1 and further comprising clips on the mirror for clipping the mirror onto an ancillary structure.

13. A liquid crystal mirror as claimed in claim 1 and further comprising an ultraviolet protective coating on the exterior surface on the front substrate.

14. A liquid crystal mirror as claimed in claim 13 and wherein the ultraviolet protective coating comprises a polymer base carrier incorporating a material selected from a group consisting of an inorganic optical thin film of an oxide, UV absorption reagents, Tinuvian compounds, and Univul.

15. A liquid crystal mirror as claimed in claim 1 and further comprising a protective coating on the exterior surface of the front substrate.

16. A liquid crystal mirror as claimed in claim 15 and wherein the protective coating is selected from a group consisting of non-conductive ITO, Titanium Oxide, Titanium Nitride, and passivation thin films.

17. A liquid crystal mirror as claimed in claim 1 and further comprising an abrasion resistive coating on the exterior surface of the front substrate.

18. A liquid crystal mirror as claimed in claim 1 and wherein the cell has a thickness between about 3 microns and about 12 microns.

19. A liquid crystal mirror as claimed in claim 1 and wherein the liquid crystal fluid comprises a dichroic dye mixture dissolved in a liquid crystal material with a positive dielectric anisotropy constant.

20. A liquid crystal mirror as claimed in claim 1 and wherein the liquid crystal fluid comprises a dichroic dye mixture dissolved in a liquid crystal material with a negative dielectric anisotropy constant.

21. A liquid crystal mirror as claimed in claim 1 and wherein the front and back substrates are substantially flat.

22. A liquid crystal mirror as claimed in claim 1 and wherein the front and back substrates are curved.

23. A liquid crystal mirror as claimed in claim 1 and further comprising an electronic control circuit for selectively causing the liquid crystal fluid to darken in response to light thereby darkening the mirror.

24. A liquid crystal mirror as claimed in claim 23 and wherein the electronic control circuit comprises a headlight sensor for darkening the mirror in response to light of an intensity above a predetermined headlight threshold impinging on the mirror and an ambient sensor for sensing ambient light intensity, the ambient sensor overriding operation of the headlight sensor to prevent darkening of the mirror when ambient light intensity is above a predetermined ambient threshold.

25. A liquid crystal mirror as claimed in claim 24 and wherein the headlight threshold and the ambient threshold are substantially the same.

26. A liquid crystal mirror as claimed in claim 24 and wherein the ambient threshold corresponds generally to ambient lighting conditions at dusk.

27. A liquid crystal mirror as claimed in claim 24 and wherein the ambient threshold corresponds generally to ambient lighting conditions about fifteen minutes before sunset.

28. A liquid crystal mirror as claimed in claim 24 and wherein the electronic control circuit includes a time delay on the response of the ambient sensor to prevent flickering of the mirror.

29. A liquid crystal mirror as claimed in claim 24 and wherein the electronic control circuit includes a time delay on the response of the headlight sensor to prevent flickering of the mirror.

30. A liquid crystal mirror that darkens in response to headlights impinging on the mirror, the liquid crystal mirror comprising:

a substantially transparent front substrate having interior and exterior surfaces and a conductive film on the interior surface of the front substrate;

a back substrate having interior and exterior surfaces and being spaced from the front substrate to define a liquid crystal cell between the interior surfaces of the substrates;

an at least partially reflective and conductive coating on the interior surface of the back substrate;

an alignment compound on opposite sides of and bounding the liquid crystal cell;

a liquid crystal fluid contained within the liquid crystal cell, the liquid crystal fluid including a dichroic dye;

an electronic control circuit coupled to the conductive film on the front substrate and the reflective conductive film on the back substrate, the electronic control circuit adapted selectively to apply a voltage signal to the films to affect the transmittance of the liquid crystal fluid; and

a headlight sensor coupled to the electronic circuit for sensing an intensity of light impinging on the mirror, the electronic circuit applying a voltage signal or discontinuing a voltage signal to reduce the transmittance of the liquid crystal fluid in response to a light intensity sensed by the headlight sensor above a predetermined headlight threshold.

31. The liquid crystal mirror of claim 30 and further comprising an ambient light sensor coupled to the electronic control circuit for sensing an intensity of ambient light, the electronic control circuit not responding to signals from the headlight sensor when the ambient sensor senses ambient light intensity above a predetermined ambient threshold.

32. The liquid crystal mirror of claim 31 and wherein the headlight threshold and the ambient threshold are substantially the same.

33. The liquid crystal mirror of claim 31 and wherein the electronic circuit includes time delays applied to signals from the headlight and ambient sensors to prevent rapid changes in the transmittance of the liquid crystal fluid.