LIQUID CRYSTAL DISPLAY

• US 3,837,729 A
• Filed: 05/14/1973
• Issued: 09/24/1974
• Est. Priority Date: 05/14/1973
• Status: Expired due to Term

• Current Assignee: Thomas B. Harsch
• Original Assignee: Thomas B. Harsch
• Inventors: Harsch, Thomas B.
• Primary Examiner(s): Bauer, Edward S.
• Assistant Examiner(s): Koren, Matthew W.
• Application Number:
  US05/360,306
• Time in Patent Office: 498 Days
• Field of Search: 350/16LC
• US Class Current: 349/178
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/134327 Segmented, e.g. alpha numeric display
• 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

High efficiency reflection without ghosts or distracting background images is obtained in a liquid crystal display of the type having a twisted nematic structure. The display employs only a single polarizer on the front face of the display; while the rear surface is provided with a reflector assembly which will scatter and reflect polarized light without depolarizing the same. The reflector can comprise a transparent plate having a diffused surface facing the liquid crystal layer and a metalized reflecting backing on its opposite side. Alternately, the reflector assembly can comprise a metalized reflecting surface which is roughened to produce the required scattering effect.

Claims

1. A liquid crystal electro-optical display comprising a layer of liquid crystal material of positive dielectric anisotropy disposed between front and rear transparent parallel plates, both of said plates being coated with films of transparent conducting material on the sides thereof facing said liquid crystal layer, the films of transparent conducting material on said front plate being on only selected areas thereof, means for effecting a twisted nematic structure in said layer of liquid crystal material, a polarizer on the side of said layer of liquid crystal material adjacent said front plate, said polarizer being the only one in said display, and a reflector assembly disposed on the other side of said layer of liquid crystal material adjacent said rear plate, the reflector assembly being such as to cause at least a portion of the light passing through areas of the front plate not coated with the conducting material to be returned from the reflector assembly so as to intersect an area of the front plate which is coated with conducting material.

2. The liquid crystal display of claim 1 wherein said reflector assembly comprises a transparent plate having a diffusing surface on its side adjacent the rear transparent parallel plate and a reflective surface on its other side.

3. The liquid crystal display of claim 1 wherein said reflector assembly comprises a metalized reflector having a roughened surface adjacent said rear transparent plate.

4. The liquid crystal display of claim 3 wherein said reflector assembly is formed from metalized granules.

5. The liquid crystal display of claim 1 wherein the films of transparent conducting material on said front plate comprise conducting strips adapted to form an alphanumerical display, the conducting strips having cut-away portions.

6. The liquid crystal display of claim 1 whereIn said reflector assembly is such as to scatter polarized light without depolarizing the same.