Liquid crystal display device

Patent metadata

Field	Value
Publication number	US-9759974-B2
Application number	US-201114346503-A
Country	US
Kind code	B2
Filing date	Oct 31, 2011
Priority date	Oct 31, 2011
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A reflective display device includes a pixel structure ( 200 ) and a liquid crystal ( 210 ) containing a dye. The pixel structure ( 200 ) provides the liquid crystal ( 210 ) with a first tilt state and a second tilt state that are stable absent application of an electric field. In the first tilt state, the liquid crystal ( 210 ) is in an untwisted configuration. In the second tilt state, the liquid crystal ( 210 ) is in a twisted configuration, and the dye has an effective absorption that is higher than an effective absorption of the dye when the liquid crystal ( 210 ) is in the first tilt state.

First claim

What is claimed is:

1. A reflective display device comprising:
a liquid crystal containing a dye; and
a pixel structure containing the liquid crystal within a cell gap, wherein:
the pixel structure permits the liquid crystal material to switch between a first tilt state and a second tilt state;
the liquid crystal material is receptive to application of a voltage to transition between the first tilt state and the second tilt state, the liquid crystal material stably persisting in a current tilt state absent voltage application after the application of the voltage to transition to the current tilt state;
in the first tilt state, the liquid crystal is in an untwisted configuration;
in the second tilt state, the liquid crystal is in a twisted configuration in which the liquid crystal orients the dye to create a fingerprint pattern for absorption of light, and the dye has an effective absorption that is higher than an effective absorption of the dye when the liquid crystal is in the first tilt state.

2. The device of claim 1 , wherein the liquid crystal has a helical pitch that is between 0.8 and 1.3 times a thickness of the cell gap.

3. The device of claim 1 , wherein the liquid crystal has a helical pitch that is between 0.9 and 1.1 times a thickness of the cell gap.

4. The device of claim 1 , wherein the pixel structure is selected from a group consisting of a zenithal bistable device, an electrophoretic particle controlled nematic device, and a post-aligned bistable nematic device.

5. A reflective display device comprising:
a liquid crystal containing a dye; and
a pixel structure containing the liquid crystal within a cell gap such that a ratio of the cell width to a helical pitch of the liquid crystal is greater than 0.8, wherein:
the pixel structure permits the liquid crystal to switch between a first tilt state and a second tilt state;
the liquid crystal receptive to application of a first voltage to transition from the first tilt state to the second tilt state, the liquid crystal stably persisting in the second tilt state after transition thereto absent voltage application;
the liquid crystal receptive to application of a second voltage to transition from the second tilt state to the first tilt state, the liquid crystal persisting in the first tilt state after transition thereto absent voltage application;
in the first tilt state, the liquid crystal is in an untwisted configuration; and
in the second tilt state, the liquid crystal is in a twisted configuration, and the dye has an effective absorption that is higher than an effective absorption of the dye when the liquid crystal is in the first tilt state.

6. The device of claim 5 , wherein the pixel structure is selected from a group consisting of a zenithal bistable device, an electrophoretic particle controlled nematic device, and a post-aligned bistable nematic device.

7. The device of claim 5 , wherein the liquid crystal comprises a nematic liquid crystal and further contains a chiral additive.

8. The device of claim 5 , wherein the ratio of the helical pitch to the cell width is in a range that is between 0.9 and 1.1.

9. The device of claim 5 , wherein the pixel structure comprises:
a first layer having a surface that provides homeotropic anchoring of the liquid crystal; and
a second layer having a surface that is patterned so that the first and second tilt states are stable absent application of the voltage.

10. The device of claim 9 , wherein the surface of the second layer contains a microstructure.

11. The device of claim 5 , wherein the pixel structure comprises:
a first layer having a surface that provides homeotropic anchoring of the liquid crystal;
a second layer having a surface that provides homogeneous anchoring of the liquid crystal; and
electrophoretic particles in the liquid crystal.

12. The device of claim 5 , wherein the pixel structure comprises a first surface and a second surface that are asymmetric in that the first surfaces gives the liquid crystal an alignment that differs from an alignment that the second surface gives to the liquid crystal.

13. A process comprising:
providing in a gap of a pixel structure a liquid crystal containing a dye; and
applying voltage to switch the liquid crystal in the pixel structure between a first stable tilt state and a second stable tilt state, the liquid crystal stably persisting in a current tilt state absent voltage application after the application of the voltage to transition to the current tilt state, wherein:
in the first stable tilt state, the liquid crystal is in an untwisted configuration; and
in the second stable tilt state, the liquid crystal is in a twisted configuration, and the dye has an effective absorption that is higher than an effective absorption of the dye when the liquid crystal is in the first stable state,
wherein the first and second stable tilt states are stable absent application of a voltage.

14. The process of claim 13 , wherein the liquid crystal has a helical pitch such that a ratio of a cell width of the pixel structure to a helical pitch of the liquid crystal is greater than 0.8.

15. The process of claim 13 , wherein in the second tilt state, the dye in the liquid crystal creates a fingerprint pattern for absorption of light.

Assignees

• Kitson Stephen
• Matranga Mario Ariosto
• Taphouse Timothy
• Younger Daniel M
• Newton Christopher
• Hewlett Packard Development Co Lp

Inventors

• Kitson Stephen
• Matranga Mario Ariosto
• Taphouse Timothy
• Younger Daniel M
• Newton Christopher

Classifications

• G02F1/1396 Primary

  the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell (G02F1/141 takes precedence) · CPC title

• G02F1/13725

  based on guest-host interaction (G02F1/13762, G02F1/13737, take precedence) · CPC title

• G02F1/133707 Primary

  Structures for producing distorted electric fields, e.g. bumps, protrusions, recesses, slits in pixel electrodes · CPC title