Stacked color liquid crystal display device

• US 6,377,321 B1
• Filed: 06/10/1999
• Issued: 04/23/2002
• Est. Priority Date: 03/22/1997
• Status: Expired due to Term

• Current Assignee: Kent Displays Incorporated
• Original Assignee: Kent Displays Incorporated
• Inventors: Urban, Ellison C., Lu, Minhua, Huang, Xiao-Yang, Khan, Asad A., Yuan, Haiji
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): CHOWDHURY, TARIFUR RASHID
• Application Number:
  US09/329,587
• Time in Patent Office: 1,048 Days
• Field of Search: 349/74, 349/80, 349/115, 349/176, 349/76.035
• US Class Current: 349/35
• CPC Class Codes: G02F 1/13473 for wavelength filtering or for colour display without the use of colour mosaic filters
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal

Abstract

A liquid crystal display device includes cell wall structure and a chiral nematic liquid crystal material. The cell wall structure and the liquid crystal cooperate to form focal conic and twisted planar textures that are stable in the absence of a field. A device applies an electric field to the liquid crystal for transforming at least a portion of the material to at least one of the focal conic and twisted planar textures. The liquid crystal material has a pitch length effective to reflect radiation having a wavelength in both the visible and the infrared ranges of the electromagnetic spectrum at intensity that is sufficient for viewing by an observer. One liquid crystal material may be disposed in a single region or two or more liquid crystal materials may be used, each in separate regions even without the infrared reflecting layer. One aspect of the invention is directed to a photolithography method for patterning a substrate of the display. The display may also have multicolor capabilities by including separate layers of at least two or three liquid crystal materials that reflect visible light. A full color stacked display may be produced with grey scale capabilities.

Claims

1. A reflective full color liquid crystal display device comprising:

first chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a first color, second chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a second color, and third chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a third color, the liquid crystal of said first material, said second material and said third material having positive dielectric anisotropy;

planar substrates that form therebetween a first region in which said first material is disposed, a second region in which said second material is disposed and a third region in which said third material is disposed, wherein said first region, said second region and said third region are stacked relative to each other and each of said first material, said second material and said third material extends continuously from near one of said substrates to near an adjacent one of said substrates;

wherein said substrates cooperate with said first material, said second material and said third material to form in said first region, said second region and said third region, scattering focal conic and reflecting planar textures that are stable in the absence of a field;

wherein incident light travels in a direction sequentially through said first region, said second region and said third region, said first region being closest to a viewer, comprising a light absorbing back layer disposed downstream of said third region relative to said direction of incident light;

wherein the incident light is reflected by the planar textures of said first region, said second region and said third region such that reflected light leaving the display exhibits a color that is an additive mixing of combinations of said colors which are reflected from said planar textures, and said incident light passing through said first region, said second region and said third region is absorbed by said light absorbing back layer; and

addressing means for applying an electric field for transforming at least a portion of the liquid crystal of at least one of said first material, said second material and said third material, to at least one of the focal conic and planar textures,

wherein a proportion of at least one of said first material, said second material and said third material exhibits a planar texture in the absence of a field and a proportion of the at least one of said first material, said second material and said third material exhibits a focal conic texture in the absence of a field, wherein said addressing means provides an electric field pulse of sufficient amplitude and duration to change the proportions of the at least one of said first material, said second material and said third material in said planar and focal conic textures, whereby the intensity of light reflected may be selectively adjusted.

2. The display device of claim 1 comprising a layer of visible colored material disposed downstream of at least one of said first region, said second region and said third region relative to said direction of incident light.

3. The display device of claim 1 wherein said light absorbing back layer is a black layer disposed downstream of said third region relative to said direction of incident light.

4. The display device of claim 1 wherein said first region is between a first of said substrates and a second of said substrates, said second region is between a third of said substrates and a fourth of said substrates, and said third region is between a fifth of said substrates and a sixth of said substrates.

5. The display device of claim 1 wherein said first region is between a first of said substrates and a second of said substrates, said second region is between said second substrate and a third of said substrates, and said third region is between said third substrate and a fourth of said substrates.

6. The display device of claim 1 wherein said first material, said second material and said third material are free from polymer.

7. The display device of claim 1 wherein said substrates are comprised of glass.

8. The display device of claim 1 wherein said substrates form a fourth region comprising a fourth chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect infrared radiation and said substrates cooperate with said fourth material to form focal conic and twisted planar textures that are stable in the absence of a field, said means for applying an electric field being adapted to transform at least a portion of the liquid crystal of said fourth material to at least one of the focal conic and twisted planar textures.

9. The display device of claim 8 further comprising a layer of black material that allows passage of infrared radiation therethrough, said layer being disposed adjacent and upstream of the fourth material with respect to a direction of travel of incident light.

10. The display device of claim 1 comprising means for lighting said display.

11. The display device of claim 1 comprising spacer members of a predetermined thickness disposed between adjacent said substrates in said first region, said second region and said third region.

12. The liquid crystal display of claim 1 wherein the first color, the second color and the third color each are a different color selected from the group of colors consisting of blue, green and red.

13. The display device of claim 12 wherein said first material, said second material and said third material are free from polymer.

14. The display device of claim 12 wherein said substrates are comprised of glass.

15. The display device of claim 12 comprising spacer members of a predetermined thickness disposed between adjacent said substrates in said first region, said second region and said third region.

16. The display device of claim 1 wherein said addressing means is adapted to provide AC voltage pulses.

17. A reflective liquid crystal display device comprising:

first chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a first color and second chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a second color, the liquid crystal of said first material and said second material having positive dielectric anisotropy;

planar substrates that form therebetween a first region in which said first material is disposed and a second region in which said second material is disposed, wherein said first region and said second region are stacked relative to each other and each of said first material and said second material extends continuously from near one of said substrates to near an adjacent one of said substrates;

wherein said substrates cooperate with said first material and said second material to form in said first region and said second region, scattering focal conic and reflecting planar textures that are stable in the absence of a field;

wherein incident light travels in a direction sequentially through said first region and said second region, said first region being closest to a viewer, comprising a light absorbing back layer disposed downstream of said second region relative to said direction of incident light;

wherein the incident light is reflected by the planar textures of said first region and said second region such that reflected light leaving the display exhibits a color that is an additive mixing of combinations of said colors which are reflected from said planar textures, and said incident light passing through said first region and said second region is absorbed by said light absorbing back layer; and

addressing means for applying an electric field for transforming at least a portion of the liquid crystal of at least one of said first material and said second material, to at least one of the focal conic and planar textures,

wherein a proportion of at least one of said first material and said second material exhibits a planar texture in the absence of a field and a proportion of the at least one of said first material and said second material exhibits a focal conic texture in the absence of a field, wherein said addressing means provides an electric field pulse of sufficient amplitude and duration to change the proportions of the at least one of said first material and said second material in said planar and focal conic textures, whereby the intensity of light reflected may be selectively adjusted.

18. The display device of claim 17 wherein said light absorbing back layer comprises a layer of black material.

19. The display device of claim 17 wherein said first region is between a first of said substrates and a second of said substrates, and said second region is between a third of said substrates and a fourth of said substrates.

20. The display device of claim 17 wherein said first region is between a first of said substrates and a second of said substrates, and said second region is between said second substrate and a third of said substrates.

21. The display device of claim 17 wherein said first material and said second material are free from polymer.

22. The display device of claim 17 wherein said substrates are comprised of glass.

23. The display device of claim 17 wherein said substrates form a third region comprising third chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect infrared radiation and said substrates cooperate with said third material to form focal conic and twisted planar textures that are stable in the absence of a field, said means for applying an electric field being adapted to transform at least a portion of the liquid crystal of said third material to at least one of the focal conic and twisted planar textures.

24. The display device of claim 23 wherein said light absorbing back layer comprises a layer of black material that allows passage of infrared radiation therethrough, said layer being disposed adjacent and upstream of said third material with respect to said direction of travel of incident light.

25. The display device of claim 17 comprising means for lighting said display.

26. The display device of claim 17 comprising spacer members of a predetermined thickness disposed between adjacent said substrates in said first region and said second region.

27. A light modulating polymer-free reflective liquid crystal display device comprising:

first chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a first color, second chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a second color, and third chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a third color, the liquid crystal of said first material, said second material and said third material having positive dielectric anisotropy;

planar substrates that form therebetween a first region in which said first material is disposed, a second region in which said second material is disposed and a third region in which said third material is disposed, wherein said first region, said second region and said third region are stacked relative to each other;

wherein said substrates cooperate with said first material, said second material and said third material to form in said first region, said second region and said third region, scattering focal conic and reflecting planar textures that are stable in the absence of a field;

wherein incident light travels in a direction sequentially through said first region, said second region and said third region, said first region being closest to a viewer, comprising a light absorbing back layer disposed downstream of said third region relative to said direction of incident light;

wherein the incident light is reflected by the planar textures of said first region, said second region and said third region such that reflected light leaving the display exhibits a color that is an additive mixing of combinations of said colors which are reflected from said planar textures, and said incident light passing through said first region, said second region and said third region is absorbed by said light absorbing back layer; and

means for addressing said first material, said second material and said third material, said means being adapted to selectively establish an electric field pulse of an amplitude and duration effective to transform at least a portion of said liquid crystal in at least one of said first region, said second region and said third region from the focal conic texture to the light reflecting planar texture, and said means being adapted to selectively establish an electric field pulse of an amplitude and duration effective to transform at least a portion of said liquid crystal in at least one of said first region, said second region and third region from the light reflecting planar texture to the focal conic texture.

28. The display device of claim 27 wherein the pitch lengths of the liquid crystal of said first material, said second material and said third material are effective to reflect color selected from the group of colors consisting of blue, green and red.

29. A light modulating polymer-free reflective liquid crystal display device comprising:

first chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a first color and second chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a second color, the liquid crystal of said first material and said second material having positive dielectric anisotropy;

planar substrates that form therebetween a first region in which said first material is disposed and a second region in which said second material is disposed, wherein said first region and said second region are stacked relative to each other and each of said first material and said second material extends continuously from near one of said substrates to near an adjacent one of said substrates;

wherein said substrates cooperate with said first material and said second material to form in said first region and said second region, scattering focal conic and reflecting planar textures that are stable in the absence of a field;

wherein incident light travels in a direction sequentially through said first region and said second region, said first region being closest to a viewer, comprising a light absorbing back layer disposed downstream of said second region relative to said direction of incident light;

wherein the incident light is reflected by the planar textures of said first region and said second region such that reflected light leaving the display exhibits a color that is an additive mixing of combinations of said colors which are reflected from said planar textures, and said incident light passing through said first region and said second region is absorbed by said light absorbing back layer; and

means for addressing said first material and said second material, said means being adapted to selectively establish an electric field pulse of an amplitude and duration effective to transform at least a portion of said liquid crystal in at least one of said first region and said second region from the focal conic texture to the light reflecting planar texture, and said means being adapted to selectively establish an electric field pulse of an amplitude and duration effective to transform at least a portion of said liquid crystal in at least one of said first region and said second region from the light reflecting planar texture to the focal conic texture.

30. A method of addressing a light modulating polymer-free reflective display device comprising first chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a first color, second chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a second color, and third chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a third color, the liquid crystal of said first material, said second material and said third material having positive dielectric anisotropy, cell wall structure comprising cell walls that form a first region in which said first material is disposed, a second region in which said second material is disposed and a third region in which said third material is disposed, wherein said first region, said second region and said third region are stacked relative to each other and each of said first material, said second material and said third material extends continuously from near one of said cell walls to near an adjacent one of said cell walls, wherein said cell wall structure cooperates with said first material, said second material and said third material to form in said first region, said second region and said third region, focal conic and planar textures that are stable in the absence of a field, wherein incident light travels in a direction sequentially through said first region, said second region and said third region, said first region being closest to a viewer, comprising a light absorbing back layer disposed downstream of said third region relative to said direction of incident light, said method comprising:

reflecting incident light with the planar textures of said first region, said second region and said third region such that reflected light leaving the display exhibits a color that is an additive mixing of combinations of said colors which are reflected from said planar textures;

absorbing with said light absorbing back layer said incident light passing through said first region, said second region and said third region; and

selectively applying electric field pulses to at least one of said first material, said second material and said third material of an amplitude and duration effective to transform at least a portion of the liquid crystal of the at least one of said first material, said second material and said third material from a focal conic texture to a light reflecting planar texture, or from a light reflecting planar texture to a focal conic texture.

31. The method of claim 30 comprising applying A.C. voltage pulses.

32. A method of selectively adjusting the intensity of reflection of a liquid crystal display, comprising first chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a first color, second chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a second color, and third chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a third color, between a maximum and a minimum intensity, the liquid crystal of said first material, said second material and said third material having positive dielectric anisotropy, wherein cell wall structure comprises cell walls that form a first region in which said first material is disposed, a second region in which said second material is disposed and a third region in which said third material is disposed, and said first region, said second region and said third region are stacked relative to each other and each of said first material, said second material and said third material extends continuously from near one of said cell walls to near an adjacent one of said cell walls, wherein light travels sequentially through said first layer, said second layer and said third layer, and wherein a light absorbing back layer is disposed downstream of said third layer, said method comprising:

subjecting at least one of said first material, said second material and said third material to an electric field pulse of sufficient amplitude and duration to cause a proportion of the at least one of said first material, said second material and said third material to exhibit a planar texture in the absence of a field and a proportion of the at least one of said first material, said second material and said third material to exhibit a focal conic texture in the absence of a field, whereby the at least one of said first material, said second material and said third material will reflect a selected intensity between said maximum and said minimum that is proportional to the amount of the at least one of said first material, said second material and said third material in said focal conic and planar textures in the absence of a field; and

absorbing light passing through said first layer, said second layer and said third layer with said light absorbing back layer.

33. A method of selectively adjusting the intensity of reflection of a liquid crystal display, comprising first chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a first color and second chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a second color, between a maximum and a minimum intensity, the liquid crystal of said first material and said second material having positive dielectric anisotropy, wherein cell wall structure comprises cell walls that form a first region in which said first material is disposed and a second region in which said second material is disposed, and said first region and said second region are stacked relative to each other and each of said first material and said second material extends continuously from near one of said cell walls to near an adjacent one of said cell walls, wherein light travels sequentially through said first layer and said second layer, and wherein a light absorbing back layer is disposed downstream of said second layer, said method comprising

subjecting at least one of said first material and said second material to an electric field pulse of sufficient amplitude and duration to cause a proportion of the at least one of said first material and said second material to exhibit a planar texture in the absence of a field and a proportion of the at least one of said first material and said second material to exhibit a focal conic texture in the absence of a field, whereby the at least one of said first material and said second material will reflect a selected intensity between said maximum and said minimum that is proportional to the amount of the at least one of said first material and said second material in said focal conic and planar textures in the absence of a field;

and

absorbing light passing through said first layer and said second layer with said light absorbing back layer.

34. A method of producing additive color images from a stacked chiral nematic liquid crystal display, comprising:

passing incident light into a first layer and a second layer of the display, said first layer and said second layer being stacked relative to one another, said first layer comprising first chiral nematic liquid crystal material having a pitch length effective to reflect visible light of a first color and said second layer comprising second chiral nematic liquid crystal material having a pitch length effective to reflect visible light of a second color, the liquid crystal of said first material and said second material having positive dielectric anisotropy;

wherein incident light travels in a direction sequentially through said first region and said second region, said first region being closest to a viewer, comprising a light absorbing layer disposed downstream of said second region relative to said direction of incident light;

absorbing said incident light passing through said first region and said second region with said light absorbing back layer;

electrically addressing said first layer and said second layer to reflect visible light from the display of one of said first color and said second color by transforming a portion of the liquid crystal of one of said first layer and said second layer into the planar texture;

electrically addressing said first layer and said second layer to reflect visible light from the display of a color that is additive of said first color and said second color by transforming portions of the liquid crystal of said first layer and said second layer into the planar texture;

wherein a proportion of at least one of said first material and said second material exhibits a planar texture in the absence of a field and a proportion of the at least one of said first material and said second material exhibits a focal conic texture in the absence of a field; and

selectively adjusting the intensity of light reflected by said planar texture by using said addressing means to provide an electric field pulse of sufficient amplitude and duration effective to change the proportions of the at least one of said first material and said second material in said planar and focal conic textures.

35. A method of producing additive color images from a stacked chiral nematic liquid crystal display, comprising:

passing incident light into a first layer, a second layer and a third layer of the display, said first layer, said second layer and said third layer being stacked relative to one another, said first layer comprising first chiral nematic liquid crystal material having a pitch length effective to reflect visible light of a first color, said second layer comprising second chiral nematic liquid crystal material having a pitch length effective to reflect visible light of a second color, and said third layer comprising third chiral nematic liquid crystal material having a pitch length effective to reflect visible light of a third color, the liquid crystal of said first material, said second material and said third material having positive dielectric anisotropy;

wherein incident light travels in a direction sequentially through said first region, said second region and said third region, said first region being closest to a viewer, comprising a light absorbing layer disposed downstream of said third region relative to said direction of incident light;

absorbing said incident light passing through said first region, said second region and said third region with said light absorbing back layer;

electrically addressing said first layer, said second layer and said third layer to reflect visible light from the display of one of said first color, said second color and said third color by transforming a portion of the liquid crystal of one of said first layer, said second layer and said third layer into the planar texture;

electrically addressing said first layer, said second layer and said third layer to reflect visible light from the display of a color that is additive of said first color, said second color and said third color by transforming portions of the liquid crystal of said first layer, said second layer and said third layer into the planar texture;

wherein a proportion of at least one of said first material, said second material and said third material exhibits a planar texture in the absence of a field and a proportion of the at least one of said first material, said second material and said third material exhibits a focal conic texture in the absence of a field; and

selectively adjusting the intensity of light reflected by said planar texture by using said addressing means to provide an electric field pulse of sufficient amplitude and duration effective to change the proportions of the at least one of said first material, said second material and said third material in said planar and focal conic textures.

36. A reflective full color liquid crystal display device comprising:

first chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a first color, second chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a second color, and third chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a third color, the liquid crystal of said first material, said second material and said third material having positive dielectric anisotropy;

planar substrates that form therebetween a first region in which said first material is disposed, a second region in which said second material is disposed and a third region in which said third material is disposed, wherein said first region, said second region and said third region are stacked relative to each other and each of said first material, said second material and said third material extends continuously from near one of said substrates to near an adjacent one of said substrates;

wherein said substrates cooperate with said first material, said second material and said third material to form in said first region, said second region and said third region, scattering focal conic and reflecting planar textures that are stable in the absence of a field;

wherein incident light travels in a direction sequentially through said first region, said second region and said third region, said first region being closest to a viewer, comprising a light absorbing back layer disposed downstream of said third region relative to said direction of incident light;

wherein the incident light is reflected by the planar textures of said first region, said second region and said third region such that reflected light leaving the display exhibits a color that is an additive mixing of combinations of said colors which are reflected from said planar textures, and said incident light passing through said first region, said second region and said third region is absorbed by said light absorbing back layer; and

a first and second set of spaced apart electrodes bounding at least a portion of the first material in the first region, a third and fourth set of spaced apart electrodes bounding at least a portion of the second material in the second region, a fifth and sixth set of spaced apart electrodes bounding at least a portion of the third material in the third region, drive circuitry electrically coupled to the first, second, third, fourth, fifth and sixth sets of electrodes for applying selected voltages to one or more of the first, second, third, fourth, fifth and sixth sets of electrodes for transforming at least a portion of the liquid crystal of at least one of said first material, said second material and said third material, to at least one of the scattering focal conic and reflecting planar textures;

wherein a proportion of at least one of said first material, said second material and said third material exhibits a planar texture in the absence of a field and a proportion of the at least one of said first material, said second material and said third material exhibits a focal conic texture in the absence of a field, wherein at least one of the said first, second, third, fourth, fifth and sixth sets of electrodes provides an electric field pulse of sufficient amplitude and duration to change the proportions of the at least one of said first material, said second material and said third material in said planar and focal conic textures, whereby the intensity of light reflected may be selectively adjusted.

37. The reflective liquid crystal display device of claim 36 wherein the first and second sets of electrodes are substantially orthogonal to each other, the third and fourth sets of electrodes are substantially orthogonal to each other, and the fifth and sixth sets of electrodes are substantially orthogonal to each other.

38. A reflective liquid crystal display device comprising:

first chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a first color and second chiral nematic liquid crystal material comprising liquid crystal having a pitch length effective to reflect visible light of a second color, the liquid crystal of said first material and said second material having positive dielectric anisotropy;

planar substrates that form therebetween a first region in which said first material is disposed and a second region in which said second material is disposed, wherein said first region and said second region are stacked relative to each other and each of said first material and said second material extends continuously from near one of said substrates to near an adjacent one of said substrates;

wherein said substrates cooperate with said first material and said second material to form in said first region and said second region, scattering focal conic and reflecting planar textures that are stable in the absence of a field;

wherein incident light travels in a direction sequentially through said first region and said second region, said first region being closest to a viewer, comprising a light absorbing back layer disposed downstream of said second region relative to said direction of incident light;

wherein the incident light is reflected by the planar textures of said first region and said second region such that reflected light leaving the display exhibits a color that is an additive mixing of combinations of said colors which are reflected from said planar textures, and said incident light passing through said first region and said second region is absorbed by said light absorbing back layer; and

a first and second set of spaced apart electrodes bounding at least a portion of the first material in the first region and a third and fourth set of spaced apart electrodes bounding at least a portion of the second material in the second region, drive circuitry electrically coupled to the first, second, third and fourth sets of electrodes for applying selected voltages to one or more of the first, second, third and fourth sets of electrodes for transforming at least a portion of the liquid crystal of at least one of said first material and said second material, to at least one of the scattering focal conic and reflecting planar textures;

wherein a proportion of at least one of said first material and said second material exhibits a planar texture in the absence of a field and a proportion of the at least one of said first material and said second material exhibits a focal conic texture in the absence of a field, wherein at least one of said first, second, third and fourth sets of electrodes provides an electric field pulse of sufficient amplitude and duration to change the proportions of the at least one of said first material and said second material in said planar and focal conic textures, whereby the intensity of light reflected may be selectively adjusted.

39. The reflective liquid crystal display device of claim 38 wherein the drive circuitry includes two drive circuits, the first drive circuit being electrically connected to the first and second sets of electrodes and the second drive circuit being electrically connected to the third and fourth sets of electrodes.

40. The reflective liquid crystal display device of claim 38 wherein the first and second sets of electrodes are substantially orthogonal to each other, and the third and fourth sets of electrodes are substantially orthogonal to each other.