Flexible liquid crystal display device with improved mechanical ability

• US 6,559,918 B1
• Filed: 04/02/1999
• Issued: 05/06/2003
• Est. Priority Date: 05/16/1998
• Status: Expired due to Fees

• Current Assignee: Universitaet Stuttgart
• Original Assignee: Institut FUER Netzwerk- und Systemtheorie Labor FUER Bildschirmtechnik
• Inventors: Lueder, Ernst
• Primary Examiner(s): Parker, Kenneth
• Application Number:
  US09/285,922
• Time in Patent Office: 1,495 Days
• Field of Search: 349/113, 349/159, 349/172, 349/171
• US Class Current: 349/172
• CPC Class Codes: G02F 1/133305 Flexible substrates, e.g. plastics, organic film
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/1339 Gaskets; Spacers; Sealing of cells
• CPC Class Codes: G02F 1/13394 spacers regularly patterned on the cell subtrate, e.g. walls, pillars G02F1/133377 takes precedence
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals

Abstract

The liquid crystal display has a liquid crystal cell (15) containing a bistable ferroelectric liquid crystal (12). The liquid crystal cell (15) is a quarter wave cell and includes two opposing covering electrodes (13) arranged in a flexible, preferably plastic, substrate (11) on opposite sides of the bistable ferroelectric liquide crystal (12) and spacers (16) distributed between the covering electrodes (13). A diffuser or reflector (18) is arranged on a rear side of the substrate (11) so that light passes twice through the liquid crystal cell (15). The bistable liquid crystal display with the quarter wave liquid crystal cell is flexible but mechanically stable to mechanical impacts, torsion and bending. Orienting layers (14) for the liquid crystal are applied obliquely or diagonally to the surface of the substrate.

Claims

1. A liquid crystal display device comprising

a flexible substrate (11) made from a flexible material;

and

a liquid crystal cell (15) containing a bistable ferroelectric liquid crystal (12) arranged between opposing covering electrodes (13) and spacers (16) arranged between the covering electrodes (13);

wherein the liquid crystal cell (15) is a quarter wave cell.

2. The liquid crystal display device as defined in claim 1 or 6, wherein said flexible substrate is a plastic foil substrate.

3. The liquid crystal display device as defined in claim 1, wherein said spacers (16) are distributed at a distance of from 40 to 60 μ

m from each other in said liquid crystal cell (15).

4. The liquid crystal display device as defined in claim 1 or 6, wherein said liquid crystal cell (15) has a thickness of about 0.8 μ

m.

5. The liquid crystal display device as defined in claim 1 or 6, further comprising respective orienting layers (14) applied to the opposing covering electrodes (13) for said liquid crystal (12), and wherein said respective orienting layers comprise at least one SiO_x or Ta₂O₅ layer deposited by vacuum vaporization or spraying over the electrodes and obliquely or diagonally inclined to a surface of said substrate.

7. The liquid crystal display device as defined in claim 1, where said spacers (16) each have a thickness of about 0.8 μ

m and a diameter of about 15 μ

m.

8. The liquid crystal display device as defined in claim 7, wherein opposite sides or ends of said spacers (16) have plane surfaces thereon.

9. The liquid crystal display device as defined in claim 1, wherein said spacers (16) each have an adhesive coating and are distributed on said covering electrodes (13) of said liquid crystal cell (15).

10. The liquid crystal display device as defined in claim 1, further comprising a low pressure in the liquid crystal cell.

6. A liquid crystal display device comprising

a flexible substrate (11) made from a flexible material;

a liquid crystal cell (15) containing a bistable ferroelectric liquid crystal (12) arranged between opposing covering electrodes (13) and spacers (16) arranged between the covering electrodes (13); and

a diffuser or reflector (18) on a rear side of said substrate opposite from said liquid crystal cell (15);

whereby the liquid crystal cell (15) is a quarter wave cell.

11. A liquid crystal display device comprising

a liquid crystal cell (15) consisting of a quarter wave cell and containing a bistable ferroelectric liquid crystal (12), said liquid crystal cell (15) comprising two opposing covering electrodes (13) arranged on opposite sides of said bistable ferroelectric liquid crystal (12) and spacers (16) distributed between said covering electrodes;

a flexible substrate (11) made from a flexible plastic material, in which said liquid crystal cell (15) is arranged; and

a diffuser or reflector (18) arranged on a rear side of said substrate (11) so that light passes twice through said liquid crystal cell (15).

12. The liquid crystal display device as defined in claim 11, wherein said spacers (16) each have a thickness of about 0.8 μ

m.

13. The liquid crystal display device as defined in claim 11, further comprising respective orienting layers (14) for said bistable ferroelectric liquid crystal (12) and wherein said respective orienting layers (14) are applied to the opposing covering electrodes (13) and each comprise at least one SiO_x or Ta₂O₅ layer obliquely or diagonally deposited by vacuum vaporization or spraying over the covering electrodes.

14. The liquid crystal display device as defined in claim 13, further comprising an adhesive border (17) extending around a periphery of said liquid crystal cell (15) between said orienting layers (14) so as to form a reservoir for said bistable ferroelectric liquid crystal (12).

15. A flexible liquid crystal display device comprising

a single liquid crystal cell (15) consisting of a quarter wave cell and containing a single bistable ferroelectric liquid crystal (12) and means for switching said bistable ferroelectric liquid crystal between two states, said means for switching said bistable ferroelectric liquid crystal comprising two opposing covering electrodes (13) arranged on opposite sides of said single bistable ferroelectric liquid crystal (12) and spacers (16) distributed between said covering electrodes;

a flexible substrate (11) made from a flexible plastic material, within which said liquid crystal cell (15) is arranged; and

wherein the liquid crystal cell (15) is a quarter wave cell.

16. The flexible liquid crystal display device as defined in claim 15, further comprising respective orienting layers (14) for said bistable ferroelectric liquid crystal (12) and wherein said respective orienting layers (14) are arranged between said opposing covering electrodes (13) and said bistable ferroelectric liquid crystal (12) and said orienting layers (14) each comprise at least one SiO_x or Ta₂O₅ layer obliquely or diagonally deposited by vacuum vaporization or spraying over the covering electrodes.

17. A flexible liquid crystal display device comprising

a flexible substrate (11) consisting of a flexible plastic material;

a liquid crystal cell (15) arranged within said flexible substrate (11), said liquid crystal cell (15) consisting of a quarter wave cell and wherein said liquid crystal cell (15) comprises a bistable ferroelectric liquid crystal (12), opposing covering electrodes (13) for switching said bistable ferroelectric liquid crystal between two states, said covering electrodes (13) being arranged on opposite sides of said liquid crystal, a plurality of spacers (16) distributed between said covering electrodes (13) to provide mechanical stability and maintain thickness, and respective orienting layers (14) for said bistable ferroelectric liquid crystal (12) arranged between said covering electrodes (13) and said bistable ferroelectric liquid crystal (12), said orienting layers (14) each comprising at least one SiO_x or Ta₂O₃ layer obliquely or diagonally deposited by vacuum vaporization or spraying over the covering electrodes; and

an adhesive border (17) extending around a periphery of said liquid crystal cell (15) between said orienting layers (14) so as to form a reservoir for said bistable ferroelectric liquid crystal (12) and wherein a low pressure exists within said reservoir.

18. The flexible liquid crystal display device as defined in claim 17, wherein said spacers (16) each have a thickness of about 0.8 μ

m and further comprising a diffuser or reflector (18) arranged on a rear side of said substrate (11) so that light passes twice through said liquid crystal cell (15).

19. The flexible liquid crystal display device as defined in claim 18, having a bending radius of less than 1.5 cm and a switching potential of under 5 V between 0°

C. and 60°

C.