Single polarizer reflective liquid crystal display

• US 3,912,369 A
• Filed: 07/02/1974
• Issued: 10/14/1975
• Est. Priority Date: 07/02/1974
• Status: Expired due to Term

• Current Assignee: LXD, Inc.
• Original Assignee: Richard A. Kashnow
• Inventors: Kashnow, Richard A.
• Primary Examiner(s): Bauer, Edward S.
• Application Number:
  US05/485,304
• Time in Patent Office: 469 Days
• Field of Search: 350/16LC,150
• US Class Current: 349/117
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 1/1396 the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell G02F1/141 takes precedence
• CPC Class Codes: G02F 2203/02 reflective

Abstract

A liquid crystal display is disclosed comprising a polarizer, a liquid crystal cell, a quarter wave plate and a reflector. In one embodiment, negative dielectric anisotropy liquid crystal materials are utilized in the cell. In another, positive dielectric anisotropy materials are utilized.

Claims

1. A reflective liquid crystal display device comprising:

polarizing means for transmitting light in a single polarization directiOn;

reflecting means;

a source of control signal;

liquid crystal cell means and quarter wave plate means positioned between said polarizing means and said reflecting means and in optical contact therewith, said liquid crystal cell and said quarter wave plate coacting on incident light polarized parallel to said polarization direction for transmitting elliptically polarized light to said reflector, wherein said liquid crystal cell is coupled to said source and modulates said transmission in accordance with said control signal for displaying information and said liquid crystal cell comprises;

a negative dielectric anisotropy liquid crystal material characterized by quasi-homeotropic boundary conditions having easy axes producing a twisted nematic structure in the bulk in the active state.

2. The reflective liquid crystal display device as set forth in claim 1 wherein said liquid crystal cell is positioned adjacent said polarizing means and said quarter wave plate means is positioned between said liquid crystal cell and said reflecting means.

3. The reflective liquid crystal display device as set forth in claim 2 wherein said liquid crystal material is characterized by a 45* molecular twist in the bulk in the active state.

4. The reflective liquid crystal display device as set forth in claim 3 wherein the easy axis of the boundary of said liquid crystal cell adjacent said polarizing means is parallel to said polarization direction.

5. The reflective liquid crystal display device as set forth in claim 4 wherein said quarter wave plate has one axis thereof parallel to said polarization direction.

6. The reflective liquid crystal display device as set forth in claim 5 wherein said reflective means comprises a metal layer on the surface of said quarter wave plate opposite said liquid crystal cell.

7. The reflective liquid crystal display device as set forth in claim 5 wherein said reflective means comprises:

a light scattering layer on the surface of said quarter wave plate opposite said liquid crystal cell; and

a metal layer on said light scattering layer.

8. The reflective liquid crystal display device as set forth in claim 4 wherein said quarter wave plate has the axes thereof oriented 45* from a line in the plane of said plate parallel to said polarization direction.

9. The reflective liquid crystal display device as set forth in claim 8 wherein said reflective means comprises a metal layer on the surface of said quarter wave plate opposite said liquid crystal cell.

10. The reflective liquid crystal display device as set forth in claim 8 wherein said reflective means comprises:

a light scattering layer on the surface of said quarter wave plate opposite said liquid crystal cell; and

a metal layer on said light scattering layer.

11. A reflective liquid crystal display device comprising:

polarizing means for transmitting light in a single polarization direction;

reflecting means;

a source of control signal;

liquid crystal cell means and quarter wave plate means positioned between said polarizing means and said reflecting means and in optical contact therewith, coacting liquid crystal cell and said quarter wave plate coactint on incident light polarized parallel to said direction for transmitting elliptically polarized light to said reflector, wherein said liquid crystal cell is coupled to said source and modulates said transmission in accordance with said control signal for displaying information;

said liquid crystal cell comprises a positive dielectric anisotropy liquid crystal material characterized by boundary conditions having easy axes producing a 45* twisted nematic structure in the quiescent state; and

said quarter wave plate means has the axes thereof oriented 45* from a line in the plane of said plate parallel to said polarization direction.

12. A reflective liquid crystal display device as set forth in claim 11 wherein thE easy axis of the boundary of said liquid crystal cell adjacent said polarizing means is orthogonal to said polarization direction.

13. The reflective liquid crystal display device as set forth in claim 11 wherein the easy axis of the boundary of said liquid crystal cell adjacent said polarizing means is parallel to said polarization direction.

14. The reflective liquid crystal display device as set forth in claim 11 wherein said reflective means comprises a metal layer on the surface of said quarter wave plate opposite said liquid crystal cell.

15. The reflective liquid crystal display device as set forth in claim 14 wherein said reflective means comprises:

a light scattering layer on the surface of said quarter wave plate opposite said liquid crystal cell; and

a metal layer on said light scattering layer.