High-brightness color liquid crystal display panel employing light recycling therein

• US 6,573,961 B2
• Filed: 05/17/1999
• Issued: 06/03/2003
• Est. Priority Date: 06/27/1994
• Status: Expired due to Fees

• Current Assignee: Reveo, Inc.
• Original Assignee: Reveo, Inc.
• Inventors: Wiley, Richard, Faris, Sadeg M., Li, Le, Jiang, Yingqiu, Hochbaum, Aharon, Vartak, Sameer, Galabova, Hristina
• Primary Examiner(s): TON, MINH TOAN T
• Application Number:
  US09/313,124
• Publication Number:
  US 20020113921A1
• Time in Patent Office: 1,478 Days
• Field of Search: 349/96, 349/98, 349/115
• US Class Current: 349/115
• 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: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal
• 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: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• 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 1/133623 Inclined coloured light beams
• 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

Reflective color filters using layers of cholesteric liquid crystals with two different center wavelengths and bandwidths per layer are stacked in two layers to provide colored light for displays. With a two layer stack circularly polarized light of one handedness can be provided. With a two layer stack circulary unpolarized colored light can be provided. With a broadband polarizing filter overlapping other filters in the stack a black matrix can be provided by reflecting all colors and transmitting no light in the overlapping areas. When broadband reflective cholesteric liquid crystals are used two primary colors can be reflected in the same pixel of a display making reflective layers with two reflective portions per layer possible. Color displays having three linear sub-pixels with three primary colors or with four sub-pixels of white, blue, green, and red in a pixel with two colors in a top row and two colors on a bottom row can are made with two colors per layer in two layer stacks. The pixels in the display are arranged such that multiple adjacent sub-pixels in a layer, or row in a layer, with the same color makes the color filters easier to manufacture. Displays using these reflective color filters may have a reflective polarizer for viewing the display at wide angles without color distortion.

Claims

1. A reflective cholesteric liquid crystal color filter comprising:

a first layer of reflective cholesteric liquid crystal color filters of one handedness havig at least a first light reflecting portion reflect a first bandwidth around a first center wavelength and a second light reflecting portion reflecting a second bandwidth around a second center wavelength and,

a second layer of reflective cholesteric liquid crystal color filters of the same handedness as the first layer having at least a third light reflecting portion reflecting a third bandwidth around a third center wavelength, and a fourth light reflecting portion reflecting a fourth bandwidth around a forth center wavelength, the second layer of reflective cholesteric liquid crystal color filters adjacent the first layer of reflective cholesteric liquid crystal color filters such that adjacent first and second layer reflecting portions reflect different wavelengths of incident light of the same handedness and transmit the remaining wavelengths, and

third and fourth layers of cholesteric liquid crystals, the third layer matching the first layer except with opposite handedness and the fourth layer matching the second layer except with opposite handedness such that any incident light with a selected color is transmitted through the color filters and incident light for all other colors is reflected,

wherein the first reflecting portion overlaps the third and fourth reflecting portions and the fourth reflecting portion overlaps the first and second reflective portions, and further wherein the second reflecting portion and third reflecting portion do not overlap each other and reflect the same wavelengths,

such that three bands of wavelengths are transmitted through the two layers.

2. A reflective cholesteric liquid crystal color filter as in claim 1 wherein,

the three center wavelengths are for the colors red, green and blue.

3. A reflective cholesteric lqiud crystal color filter as in claim 2 wherein,

the bandwidths are narrow such that they are matched to the bandwidths of the incident light.

4. A reflective cholesteric liquid crystal color filter as in claim 1 wherein,

the two layers of reflective cholesteric liquid crystal color filters are replaced with one layer having a top portion of cholesteric liquid crystals polymerized to reflect a different wavelength and band width of light than the bottom portion.

5. A reflective cholesteric liquid crystal color filter comprising:

a first layer of reflective cholesteric liquid crystal color filters of one handedness having at least a first light reflecting portion reflecting a first bandwidth around a first center wavelength and a second light reflecting portion reflecting a second bandwidth around a second center wavelength and,

a second layer of reflective cholesteric liquid crystal color filters of the same handedness as the first layer having at least a third light reflecting portion reflecting a third bandwidth around a third center wave length, and a fourth light reflecting portion reflecting a forth bandwidth around a forth center wavelength, the second layer of reflective cholesteric liquid crystal color filters adjacent the first layer of reflecting cholesteric liquid crystal color filters such that adjacent first and second layer reflecting portions reflect different wavelengths of incident light of the same handedness and transmit the remaining wavelengths,

wherein,

the first reflecting portion overlaps the third and fourth reflecting portions and the fourth reflecting portion overlaps the first and second reflective portions,

the second reflecting portion and the third reflecting portion do not overlap each other and reflect the same wavelengths,

such that these bands of wavelengths are transmitted through the two layers, further comprising a layer of reflective color filters forming a black matrix by overlapping the color filters in the first and second layers to reflect the colors not reflected by the first and second layers.

6. A reflective cholesteric liquid crystal color filter as in claim 5 wherein,

a circular polarizer of opposite handedness of the cholesteric liquid crystals in the first and second layers polarizes unpolarized light incident thereon,

a quarter wave plate converts the circulary polarized light transmitted by the first and second layers into linearly polarized.

7. A reflective cholesteric liquid crystal color filter as in claim 5 wherein,

the layers are used in displays having an array of pixels each pixel having three sub-pixels, the width of each light reflecting portions in each layer extends for two sub-pixels of a first color and four sub-pixels of a second color.

8. A reflective cholesteric liquid crystal color filter as in claim 5 wherein,

the layers are used in displays having an array of pixels, each pixel having three sub-pixels, where the adjacent pixels have revered sub-pixel patters such that adjacent pixels have reflective color portions two sub-pixel widths in size, half in each pixel, for ease of manufacture.

19. A reflective cholesteric liquid crystal color filter as in claim 5 wherein,

the light entering the reflective cholesteric liquid crystal color filter emanates from a backlight and is collimated in a collimator and then enters a reflective polarizer for providing a wide view angle without color distortion in the reflective cholesteric liquid crystal color filters,

the light then enters the reflective cholesteric liquid crystal color filter were the adjacent first and second layer reflecting portions reflect different wavelengths of incident light of the same handedness and transmit the remaining wavelengths,

the transmitted light enters a quarter wave plate to be linearly polarized,

the linearly polarized light then enters a liquid crystal light valve to selectively pass light therethrough,

light passing though the light valve passes through an analyzer and a diffuser to illuminate a color display.

9. A reflective cholesteric liquid crystal color filter comprising:

a first layer of reflective cholesteric liquid crystal color filters of one handedness having at least a first light reflecting portion reflecting a first bandwidth around a first center wavelength and a second light reflecting portion reflecting a second bandwidth around a second center wavelength and,

a second layer of reflective cholesteric liquid crystal color filters of the same handedness as the first layer having at least a third light reflecting portion reflecting a third bandwidth around a third center wavelength, and a fourth light reflecting portion reflecting a forth bandwidth around a forth center wavelength, the second layer of reflective cholesteric liquid crystal color filters adjacent the first layer of reflecting cholesteric liquid crystal color filters such that adjacent first and second layer reflecting portions reflect different wavelength of incident light of the same handedness and transmit the remaining wavelengths wherein,

the first bandwidth includes the colors blue and green, and the third bandwidth includes the colors green and red,

the second bandwidth includes the color blue and the fourth bandwidth includes the color red,

a clear transparent portion in the second layer is paired vertically with the first bandwidth,

a clear transparent portion in the first layer is paired vertically with the first bandwidth,

and the fourth reflective portion in the second layer is paired vertically with the second reflective portion in the first layer,

such that red is transmitted through the bandwidth, blue is transmitted through the third bandwidth and green is transmitted through the second and fourth bandwidths to provide the primary colors for a display.

10. A reflective cholesteric liquid crystal color filter as in claim 9 wherein,

the third reflective portions overlap the first reflecting portions and the second reflecting portions and the first reflective portions overlap the third and forth reflective portions, such that a black matrix is formed by reflecting all light in the overlapping portions.

11. A reflective cholesteric liquid crystal color filter as in claim 10 wherein,

third and fourth layers of cholesteric liquid crystals are added, the third layer matching the first layer except with opposite handedness and the fourth layer matching the second layer except with opposite handedness such that any incident light with a selected color is transmitted through the color fitters and incident light for all other colors is reflected.

12. A reflective cholesteric liquid crystal color filter as in claim 10 wherein,

a circular polarizer of opposite handedness of the cholesteric liquid crystals in the first and second layers polarizes unpolarized light incident thereon,

a quarter wave plate converts the circularly polarized light transmitted by the first and second layers into linearly polarized light.

13. A reflective cholesteric liquid crystal color filter as in claim 12 wherein,

the circular polarizer is a broad band cholesteric liquid crystal polarizer.

14. A reflective cholesteric liquid crystal color filter as in claim 10 wherein,

the layers are used in displays having an array of pixels, each pixel having three sub-pixels, where the adjacent pixels have reversed sub-pixel patterns such that adjacent pixels have reflective color portions two sub-pixel widths in size, half in each pixel, for ease of manufacture.

15. A reflective choleric liquid crystal color filter as in claim 9 wherein,

third and forth layers of cholesteric liquid crystals are added, the third layer matching the first layer except with opposite handedness and the forth layer matching the second layer except with opposite handedness such that any incident light with a selected color is transmitted through the color filters and incident light for all other colors is reflected.

16. A reflective cholesteric liquid crystal color filter as in claim 9 wherein,

a circular polarizer of opposite handedness of the cholesteric liquid crystals in the first and second layers polars unpolarized light incident thereon,

a black matrix layer blocks light from the polarizer before it is transmitted to the first and seconds layers,

a quarter wave plate converts the circularly polarized light transmitted by the first and second layers into linearly polarized light.

17. A reflective cholesteric liquid crystal color filter as in claim 16 wherein, the circular polarizer is a broad band cholesteric liquid crystal polarizer.

18. A reflective cholesteric liquid crystal color filter as in claim 9 wherein,

the layers are used in displays having an array of pixels, each pixel having three sub-pixels, where the adjacent pixels have reversed sub-pixel patterns such that adjacent pixels have reflective color portions two sub-pixel widths in size, half in each pixel, for ease of manufacture.

20. A reflective cholesteric liquid crystal color filter as in claim 9 wherein,

the bandwidth are narrow such that they are matched to the bandwidth of the incident light.

21. A reflective cholesteric liquid crystal color filter as in claim 9 wherein,

the two layers of reflective cholesteric liquid crystal color filters are replaced with one layer having a top portion of cholesteric liquid crystals polymerized to reflect a different wavelength and bind width of light than the bottom portion.

22. A reflective cholesteric fluid crystal color filter comprising:

a first layer of reflective cholesteric liquid crystal color filters of one handedness having at least a first light reflecting portion reflecting a first bandwidth around a first center wavelength, a second light reflecting portion reflecting a second bandwidth around a second center wavelength and a third light reflecting portion reflecting a third bandwidth around a third center wavelength and,

a second layer of reflective cholesteric liquid crystal color filters of the same handedness as the first layer having at least a fourth light reflecting portion reflecting a forth bandwidth around a forth center wavelengths, a fifth reflecting portion having a fifth bandwidth around a fifth center wavelength and a sixth reflecting portion having a sixth bandwidth around a six center wavelength, the second layer of reflective cholesteric liquid crystal color filters adjacent the first layer of reflective cholesteric liquid crystal color filters such that adjacent first and second layer reflecting portions reflect different wavelengths of incident light of the same handedness and transmit the remaining wavelengths wherein

the bandwidths and center wavelengths of the first layer an the second layer are the same, and overlap each other such that the first reflecting portion is vertically adjacent the fourth and fifth reflective portions, the second reflective portion is vertically adjacent the fifth and sixth reflective portions and the third reflective portion is vertically adjacent the sixth and fourth reflective portions,

further comprising a third and a forth layer identical to the first and second layers with opposite handedness, the third and layers aligned to match the reflecting portion positions of the first and second layers, such that any incident light with a selected color is transmitted through the color filters and incident light for all other colors is reflected.

23. A reflective cholesteric liquid crystal color filter as in claim 22 wherein,

the three center wavelengths are for the colors red, green and blue.