Liquid crystal materials and devices

• US 4,462,924 A
• Filed: 09/10/1982
• Issued: 07/31/1984
• Est. Priority Date: 09/13/1978
• Status: Expired due to Term

• Current Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Original Assignee: Secretary of State For In Her Brittanic Majesty's Government of The United Kingdom of Great Britain and Northern Ireland
• Inventors: Raynes, Edward P.
• Primary Examiner(s): Gron, Teddy S.
• Application Number:
  US06/416,608
• Time in Patent Office: 690 Days
• Field of Search: 350/350 R, 252/299.5, 252/299.63, 252/299.64, 252/299.65, 252/299.66, 252/299.67
• US Class Current: 252/299.63
• CPC Class Codes: C09K 19/44 containing compounds with benzene rings directly linked

Abstract

A liquid crystal for use in liquid display devices comprises at least one material from group 1 comprising: ##STR1## at least one of the group 1 materials having n=2, or 4; and at least one material from group 2 comprising: ##STR2## together with an ester liquid crystal material. The ester forms between 10% and 90% (preferably between 30% and 70%) by weight of the total mixture and the group 2 material forms between 5% and 30% by weight of the total mixture.

Examples of the esters have the general formula ##STR3## where R₁, R₂ represent alkyl or alkoxy groups, and ##STR4## where R₃, R₄ represent alkyl groups. All alkyl and alkoxy end groups are unbranched.

Claims

1. A liquid crystal material for multiplex addressed liquid crystal displays comprising

(1) at least one member selected from the group consisting of ##STR180## wherein m and n are integers and n=2 or 4 or m=3 in at least one of said materials,

(2) a liquid crystal material comprising a member selected from the group consisting of ##STR181## wherein p, q, r, and s are integers, and (3) at least one ester having the formula ##STR182## wherein R₁ and R₂ are straight chain alkyl;

said ester (3) forming between 10% and 90% by weight of the total mixture and said liquid crystal material (2) forming between 5% and 30% by weight of the total mixture.

2. A liquid crystal material as claimed in claim 1 and further including a compound of the formula selected from the group consisting of ##STR183## where m and n are each integers of 6 or less.

3. A liquid crystal material as claimed in claim 2 comprising ##STR184## wherein n is 0, 2, 4, or 6.

4. A liquid crystal material as claimed in claim 1 wherein R₁ is an alkyl group having between 1 and 5 carbon atoms.

5. A liquid crystal material as claimed in claim 1 wherein R₂ is an alkyl group having between 3 and 7 atoms.

6. A liquid crystal material as claimed in claim 1 wherein the amount of ester is between 30% and 70% of the total material.

7. A liquid crystal material as claimed in claim 1 wherein p=2.

8. A liquid crystal material as claimed in claim 1 wherein q=5.

9. A liquid crystal material as claimed in claim 1 wherein r=5 or 7.

10. A liquid crystal material as claimed in claim 1 wherein s=5.

11. A liquid crystal material as claimed in claim 1 wherein a small amount of a cholesteric liquid crystal material is added to the mixture to provide a cholesteric pitch between 1500 and 300 microns.

12. A liquid crystal material as claimed in claim 11 wherein up to 0.5% by weight of cholesteric material, ##STR185## is added to the mixture.

13. A liquid crystal material as claimed in claim 11 wherein up to 0.05% by weight of cholesteric material, ##STR186## is added to the mixture.

14. A liquid crystal display device comprising a layer of a liquid crystal material as claimed in claim 1 formed into a layer contained between two slides, at least one of which slides is transparent, both carrying electrode structures and both surface-treated to provide a progressive liquid crystal molecular twist across the layer.