Liquid crystal display with twist angle less than 80 degrees

• US 4,609,255 A
• Filed: 06/29/1984
• Issued: 09/02/1986
• Est. Priority Date: 07/01/1983
• Status: Expired due to Fees

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Leenhouts, Frans, de Zwart, Maarten
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/626,196
• Time in Patent Office: 795 Days
• Field of Search: 350/337, 350/341
• US Class Current: 349/103
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/13725 based on guest-host interaction G02F1/13762, G02F1/13737, take precedence

Abstract

A liquid crystal display wherein in order to obtain an improved contrast without diminishing the brightness of the display, the angle of twist is reduced in the case of a liquid crystal display according to the rotating cell principle, polarizers with greater extinction power are used and up to 3% by weight of a suitable dye is added. Thus, a largely achromatic display is also obtained.

Claims

1. A liquid crystal display comprising:

two parallel support plates separated by a peripheral border to form a cell in the space between said plates and said border;

a layer of nematic liquid crystal with positive dielectric anisotropy filled in said cell;

electrode coatings formed on inside surfaces of said plates;

first and second orientation coatings formed on respective of said electrode coatings, said orientation coatings defining orientation directions enclosing an angle (α

) less than 80°

,

a first polarizer associated with said first orientation coating and having a polarization direction which runs parallel to the orientation direction of said first orientation coating;

a second polarizer associated with said second orientation coating and having a polarization direction which runs perpendicular to the orientation direction of the second orientation coating;

said polarizers having an extinction power greater than 100;

said liquid crystal layer having a thickness (d) and defining an anisotropy of an index of refraction (Δ

n) the product of which is less than 1.3 μ

m; and

a dichroic dye of up to 3% by weight added to the liquid crystal layer.

2. A liquid crystal display according to claim 1, wherein said dichroic dye has a spectral color forming the complement of a spectral color for the product of the thickness (d) and the anisotropy of the index of refraction (Δ

n) of the liquid crystal.

3. A liquid crystal display according to claim 2, wherein the angle (α

) enclosed by the orientation directions in between 60° and

40°

.

4. A liquid crystal display according to claim 2, wherein the extinction power of the polarizers is greater than 1000.

5. A liquid crystal display, according to claim 2, wherein said liquid crystal layer comprises less than 2% by weight of said dichroic dye.