Ferroelectric liquid crystal display device having equalizing means

• US 5,033,825 A
• Filed: 12/22/1989
• Issued: 07/23/1991
• Est. Priority Date: 12/26/1988
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Ishikawa, Masahito, Murayama, Akio, Matsumoto, Shoichi, Yamamoto, Tomiaki
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): MAI, HUY KIM
• Application Number:
  US07/455,002
• Time in Patent Office: 578 Days
• Field of Search: 350/350 S, 350/347 E, 350/339 R, 350/337
• US Class Current: 349/102
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/141 using ferroelectric liquid crystals
• CPC Class Codes: G02F 2202/40 Materials having a particular birefringence, retardation
• CPC Class Codes: G02F 2413/01 Number of plates being 1
• CPC Class Codes: G02F 2413/08 with a particular optical axis orientation

Abstract

A light crystal cell comprising a pair of substrates arranged substantially parallel and provided with electrodes on their opposite surfaces, and a ferroelectric liquid crystal composition held between these substrates, two polarizers arranged on either side of said liquid crystal cell, and an optical retardation film for equalizing the states of polarization of transmitted light that has passed through parts of said liquid crystal cell of different thickness. It is preferable that this optical retardation film is inserted between the liquid crystal cell and a polarizer. The number of optical retardation films need not however be limited to one, and several such films may be used. A polarizer and optical retardation film may also be assembled as one unit.

Claims

1. A ferroelectric liquid crystal display device , comprising:

a liquid crystal cell containing a pair of substrates arranged substantially parallel and provided with electrodes on their opposite surfaces, and a ferroelectric liquid crystal composition held between these substrates,

two polarizers arranged on either side of said liquid crystal cell, and

a means of equalizing the states of polarization of transmitted light that has passed through parts of said liquid crystal cell of different thickness.

2. A liquid crystal display device according to claim 1, wherein said equalization means is inserted between said liquid crystal cell and either one of said polarizers.

3. A liquid crystal display device according to claim 1 or 2, wherein said equalization means is an optical retardation film.

4. A liquid crystal display device according to claim 3, wherein the thickness of said liquid crystal cell is from 1 μ

m to 5 μ

m.

5. A liquid crystal display device according to claim 3, wherein said optical retardation film and the adjacent polarizer are assembled as one unit.