Liquid crystal display device

• US 5,174,920 A
• Filed: 03/28/1990
• Issued: 12/29/1992
• Est. Priority Date: 03/28/1989
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Iijima, Chiyoaki
• Primary Examiner(s): Stoll, Robert L.
• Assistant Examiner(s): KELLY, CYNTHIA HARRIS
• Application Number:
  US07/500,658
• Time in Patent Office: 1,007 Days
• Field of Search: 350/350 R, 252/299.66, 252/299.63, 252/299.67, 359/103, 359/81
• US Class Current: 252/299.01
• CPC Class Codes: C09K 19/3001 Cyclohexane rings
• CPC Class Codes: C09K 19/3458 Uncondensed pyrimidines
• CPC Class Codes: C09K 19/42 Mixtures of liquid crystal compounds covered by two or more of the preceding groups C09K19/06 - C09K19/40

Abstract

A liquid crystal display device including a super twisted nematic liquid crystal material with a twist angle between about 180° and 360°. The liquid crystal composition includes at least one of a compound [I] and a compound [II] for lowering the threshold voltage and at least one of a compound [III] and a compound [IV] for widening the d/p range and improving Δ(d/p). Compounds [I]-[IV] are represented by the general formulae: ##STR1## wherein R₁ is R--, RO-- or RCH═CH--, R₂ is R--, RO--, CN-- or F--, ##STR2## X is a single covalent bond, --C.tbd.C--, --CH₂ CH₂ -- or --COO--, ##STR3## if X is not --CH₂ CH₂ --; R₃ is R--, RO-- or RCH═CH--, R₄, R₅ and R₇ are R-- or RO--, Y is a single covalent bond or --CH₂ CH₂ --, ##STR4## if Y is a single covalent bond, ##STR5## R₆ is --CN or --F, ##STR6## and R₈ is --F, or --CN if ##STR7## and R is an alkyl group having from 1 to 9 carbon atoms. The composition includes at least 20 weight percent of compounds [I] and compounds [II] and between about 5 and 55 weight percent of compounds [III] and compounds [IV].

Claims

1. A liquid crystal display device, comprising:

a liquid crystal display cell including a pair of spaced apart opposed electrode substrates, a liquid crystal material in the space between the substrates, and spacer means formed from an elastic resin for separating the substrates, the liquid crystal material having a twist angle between about 180° and

360° and

having a ratio d/p of layer thickness (d) to spiral pitch (p) of the liquid crystal material related to the twist angle (φ

) of the liquid crystal material such that

space="preserve" listing-type="equation">φ

/360-1/4<

d/p<

φ

/360,

the liquid crystal material including at least one of a compound (I) and a compound (II), the total amount of Compound (I) and Compound (II) constituting at least 20 weight percent of the liquid crystal material, wherein Compound (I) is represented by the general formula ##STR113## wherein R₁ is R--, RO-- or RCH═

CH--, R₂ is R--, RO--, CN-- or F--, ##STR114## X is a single covalent bond, --C.tbd.C--, --CH₂ CH₂ -- or --COO--, ##STR115## if X is not --CH₂ CH₂ --; and

R is a linear alkyl group having from 1 to 9 carbon atoms, and Compound (II) is represented by the general formula;

##STR116## wherein R₃ is R--, RO-- or RCH═

CH--, R₄ is R-- or RO--, Y is a single covalent bond or CH₂ CH₂, ##STR117## if Y is a single covalent bond, and R is a linear alkyl group having from 1 to 9 carbon atoms; and

at least one of a Compound (III) and a Compound (IV), the total amount of Compound (III) and Compound (IV) constituting between about 5 and 55 weight percent of the liquid crystal material, wherein Compound (III) is represented by the general formula;

##STR118## wherein R₅ is R-- or RO--, ##STR119## R₆ is --CN or F, and R is a linear alkyl group having from 1 to 9 carbon atoms, and Compound (IV) is represented by the general formula;

##STR120## wherein R₇ is R-- or RO--, ##STR121## and R₈ is --F, or --CN if E is ##STR122## and R is a linear alkyl group having from 1 to 9 carbon atoms; and

a pair of linear polarizers, each having an axis of polarization disposed about the liquid crystal cell.

2. The display device of claim 1, wherein the resin is selected from the group consisting of polystyrene, butadiene polymer, polyurethane, chloroprene polymer and vinyl chloride-vinyl acetate copolymer.