Liquid crystal display having a double-refracting compensation layer

• US 5,311,339 A
• Filed: 08/12/1992
• Issued: 05/10/1994
• Est. Priority Date: 10/04/1991
• Status: Expired due to Term

• Current Assignee: Optrex Europe GmbH (Kyocera Corporation)
• Original Assignee: Optrex Europe GmbH (Kyocera Corporation)
• Inventors: Ott, Thomas, Fertig, Werner, Wahl, Jurgen
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US07/929,696
• Time in Patent Office: 636 Days
• Field of Search: 359/53, 359/73, 359/63, 359/69, 359/75
• US Class Current: 349/76
• CPC Class Codes: G02F 1/133631 with a spatial distribution of the retardation value
• CPC Class Codes: G02F 1/133636 with twisted orientation, e.g. comprising helically oriented LC-molecules or a plurality of twisted birefringent sublayers
• 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

Abstract

A liquid-crystal display has a liquid-crystal cell (1) which is formed of two substrates (2) spaced apart from each other, and is filled with a nematic liquid-crystal substance (4). On the cell inner-space side, electrode layers (3) which can be acted on by voltage are arranged on the substrates (2). On the cell outside space side, a double-refracting compensation layer extends over the cell surface. Liquid-crystal cell (1) and compensation layer are arranged between two polarization filters (11). The compensation layer is developed over its surface with a plurality of regions adjacent to each other. The amount of the double refraction of the regions differs from each other by a small amount.

Claims

1. A liquid-crystal display comprising

a controllable liquid crystal cell;

wherein the controllable liquid-crystal cell comprises two substrates arranged spaced apart from each other and being filled with a liquid-crystal substance;

the cell further comprises electrode layers which can be acted on by voltage and are arranged on the substrates within the cell;

the liquid crystal display further comprises a compensation layer arranged outside the cell and extending over a surface of the cell, the compensation layer being a double-refracting compensation layer;

the display further comprises a polarization filter assembly having at least one filter, the filter assembly providing a filter in front of the liquid crystal cell and the compensation layer or behind the liquid crystal cell and the compensation layer or on opposite sides of the liquid-crystal cell and the compensation layer; and

the compensation layer comprises a plurality of adjacent regions providing double refraction to light rays passing therethrough, the amount of the double refraction of neighboring regions differing by a small amount from each other.

2. A display according to claim 1, wherein

the regions of different amount of double refraction have a smaller size than can be resolved by the human eye.

3. A display according to claim 1, wherein

said double-refracting compensation layer comprises a non-controllable second liquid-crystal cell having two substrates spaced apart from each other and being filled with a twisted nematic liquid-crystal substance, the regions of different amount of double refraction being located on a surface of said second liquid crystal cell.

4. A display according to claim 3, wherein

the liquid-crystal substance of either one or both the liquid-crystal cells is of the nematic type having a twist angle of 90°

or more.

5. A display according to claim 1, wherein

the regions of differing amounts of double refraction are formed by regions of different cell thickness.

6. A display according to claim 5, wherein

the regions of different amount double refraction are formed by a plurality of depressions formed on a surface of the compensation layer facing said controllable liquid crystal cell.

7. A display according to claim 6, wherein

the depressions have a depth which corresponds approximately to the amount of the differences in layer thickness of the liquid-crystal layer of the controllable liquid-crystal cell over the length of the surface thereof.

8. A display according to claim 6, wherein

the depressions are distributed uniformly.

9. A display according to claim 6, wherein

the depressions are distributed non-uniformly.

10. A display according to claim 6, wherein

said double-refracting compensation layer comprises a non-controllable second liquid-crystal cell having two substrates spaced apart from each other and being filled with a twisted nematic liquid-crystal substance;

and

the depressions are formed on a substrate of the second liquid-crystal cell.

11. A display according to claim 6, wherein

said double-refracting compensation layer comprises a non-controllable second liquid-crystal cell having two substrates spaced apart from each other and being filled with a twisted nematic liquid-crystal substance;

and

a surface of a substrate of the second liquid-crystal cell is provided with a coating having the depressions.

12. A display according to claim 1, wherein

the double-refracting compensation layer comprises a plurality of layers of optically transmissive material.

13. A display according to claim 12, wherein

a first and a second of the optically transmissive layers of the compensation layer are arranged on opposite sides of the controllable liquid-crystal cell.

14. A display according to claim 1, wherein

the double refracting compensation layer is formed of at least one foil.

15. A display according to claim 14, wherein

the regions of different amount of double refraction are produced by a temperature treatment of the foil.

16. A display according to claim 14, wherein

regions of different amount of double refraction are formed by formation of a surface of the foil with a plurality of depressions.

17. A display according to claim 16, wherein

the depressions are distributed uniformly.

18. A display according to claim 16, wherein

the depressions are distributed non-uniformly.

19. A display according to claim 16, wherein

the depressions are produced by embossing.