Liquid crystal display having positive and negative uniaxially oriented polymer films

• US 5,249,071 A
• Filed: 11/20/1991
• Issued: 09/28/1993
• Est. Priority Date: 11/22/1990
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Yoshimura, Yumi, Yoshimizu, Toshiyuki, Ohnishi, Hiroshi, Kishimoto, Keiko
• Primary Examiner(s): Heyman, John S.
• Assistant Examiner(s): GROSS, ANITA P
• Application Number:
  US07/795,324
• Time in Patent Office: 678 Days
• Field of Search: 359/73, 359/63
• US Class Current: 349/102
• CPC Class Codes: G02F 1/133634 the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis
• CPC Class Codes: G02F 1/1397 the twist being substantially higher than 90°, e.g. STN-, SBE-, OMI-LC cells
• CPC Class Codes: G02F 2413/13 Positive birefingence
• CPC Class Codes: G02F 2413/14 Negative birefingence

Abstract

In a supertwist type liquid crystal display, a pair of upper and lower polarizers and polymer films are disposed in such an arrangement that the upper polarizer, first uniaxial oriented polymer film, second uniaxial oriented polymer film, supertwist type liquid crystal cell, third uniaxial oriented polymer film, first biaxial oriented polymer film and the lower polarizer are sequentially piled on in this order, and each of said first, second and third uniaxial oriented polymer films has a positive optical anisotropy and said first biaxial oriented polymer film has a negative optical anisotropy.

Claims

1. A liquid crystal display with a supertwist type liquid crystal panel including a supertwist type liquid crystal layer interposed between upper and lower substrates, comprising:

a uniaxial oriented polymer film member having a positive optical anisotropy with a small retardation in a direction normal to a plane of said uniaxial oriented polymer film member; and

a biaxial oriented polymer film having a negative optical anisotropy with a small phase difference not more than 20 nm in the plane of the film and a retardation value of 200 nm to 400 nm in a direction normal to said biaxial oriented polymer film,

wherein said uniaxial oriented polymer film member and said biaxial oriented polymer film are disposed on opposite sides of said supertwist type liquid crystal panel so as to act as an optical compensator.

2. The liquid crystal display of claim 1, wherein said uniaxial oriented polymer film member includes first, second, and third uniaxial oriented polymer films such that an upper polarizer, said first uniaxial oriented polymer film, said second uniaxial oriented polymer film, said supertwist type liquid crystal layer, said third uniaxial oriented polymer film, said biaxial oriented polymer film, and a lower polarizer are sequentially arranged in this order.

3. The liquid crystal display of claim 2, wherein said first second, and third uniaxial oriented polymer films each have a thickness of 50 μ

m.

4. The liquid crystal display of claim 2, wherein said first, second, and third uniaxial oriented polymer films are made of polycarbonate or polyvinyl alcohol.

5. The liquid crystal display of claim 2, wherein said biaxial oriented polymer film has a thickness of 0.2 to 0.3 mm.

6. The liquid crystal display of claim 2, wherein said biaxial oriented polymer film is made of polystyrene or polymethylmethacrylate.

7. The liquid crystal display according to claim 2, wherein

a slow axis of said first uniaxial oriented polymer film and a slow axis of said second uniaxial oriented polymer film form an angle of 25 to 35 degrees,

wherein an angle formed by the slow axis of said second uniaxial oriented polymer film and an orientation axis of liquid crystal molecules of said lower substrate is greater than an angle formed by an orientation axis of liquid crystal molecules of said upper substrate and said orientation axis of liquid crystal molecules of said lower substrate, in a counterclockwise direction,

wherein an angle formed by a slow axis of said third uniaxial oriented polymer film and said slow axis of said first uniaxial oriented polymer film is greater than an angle formed by said orientation axis of liquid crystal molecules of said lower substrate and said slow axis of said first uniaxial oriented polymer film, in a counterclockwise direction,

wherein an absorption axis of said upper polarizer is set at an orientation of approximately 15 degrees in a counterclockwise direction from the slow axis of said first uniaxial oriented polymer film,

wherein an absorption axis of said lower polarizer is set at an orientation of approximately 50 degrees in the counterclockwise direction from the slow axis of said third uniaxial oriented polymer film,

wherein a retardation value in a normal direction of said biaxial oriented polymer film is approximately equal to a retardation value in a plane of said third uniaxial oriented polymer film, and

wherein the orientation axis of the liquid crystal molecules of said upper substrate or the slow axis of said third uniaxial oriented polymer film is set in a direction of viewing.

8. The liquid crystal display of claim 7, wherein said slow axis of said first uniaxial oriented polymer film and said slow axis of said second uniaxial oriented polymer film form an angle of 30 degrees.

9. The liquid crystal display of claim 1, further comprising upper and lower orientation films on opposite sides and directly adjacent to said supertwist type liquid crystal layer, wherein said upper and lower orientation films are made of an organic polymer.

10. The liquid crystal display of claim 1, wherein said supertwist type liquid crystal layer is twisted 240 degrees in a clockwise direction.

11. The liquid crystal display of claim 1, wherein the retardation value of said biaxial oriented polymer film is 250 nm in the normal direction.

12. The liquid crystal display of claim 1, wherein the retardation value of said biaxial oriented polymer film is 400 nm in the normal direction.

13. The liquid crystal display of claim 1, wherein as the retardation value of said biaxial oriented polymer in the normal direction is increased, a viewing angle in a specific direction is expanded.

14. The liquid crystal display of claim 13, wherein the viewing angle in the specific direction is 65 degrees when the retardation value is 250 nm and 86 degrees when the retardation value is 400 nm.