Liquid crystal display utilizing reflected light

• US 3,924,932 A
• Filed: 08/09/1974
• Issued: 12/09/1975
• Est. Priority Date: 08/09/1974
• Status: Expired due to Term

• Current Assignee: Mititaka Yamamoto
• Original Assignee: Mititaka Yamamoto
• Inventors: Yamamoto, Mititaka
• Primary Examiner(s): Bauer, Edward S.
• Application Number:
  US05/496,193
• Time in Patent Office: 487 Days
• Field of Search: 350/150,16LC
• US Class Current: 349/84
• CPC Class Codes: G02F 1/1335 Structural association of cells with optical devices, e.g. polarisers or reflectors

Abstract

Apparatus for increasing the contrast ratio in a liquid crystal display by increasing the intensity of ambient light which is available to the eye of an observer. The usual liquid crystal display assembly utilizing a twist nematic or field effect liquid crystal in the reflective mode has a top polarizer, transparent support members on either side of a liquid crystal layer, transparent electrodes arranged in predetermined fashion on opposite sides of the liquid crystal layer in electrical contact therewith, a bottom polarizer and a light reflector adjacent to the bottom polarizer. In this disclosure, the top polarizer is removed from the liquid crystal display assembly and placed at an angle relative to the surface thereof. The top polarizer is in such a position as to intercept ambient light which has initially passed through and then been reflected back through the liquid crystal display. The reflected light is polarized in predetermined patterns as determined by electric fields created between electrodes on opposite sides of the liquid crystal layer and thereby provides a light/dark pattern to a viewer positioned on the side of the top polarizer away from that approached by the reflected light. High contrast ratios result as available ambient light energy is conserved by requiring to pass through the top polarizer only once.

Claims

1. In combination with a liquid crystal assembly of the type having sequential layers including a first transparent support plate, a covering transparent electrode attached to one side of the first support plate, a field effect liquid crystal in electrical contact with the covering transparent electrode, a second transparent support plate adjacent to the field effect liquid crystal, a predetermined array of transparent electrodes attached to one side of the second transparent support plate in electrical communication with the field effect liquid crystal, and a first light polarizer attached to the other side of the second transparent support plate, a second polarizer inclined relative to the other side of the first transparent support plate, and a reflector in juxtaposition with the first polarizer, whereby ambient light incident on the first transparent support plate on the side of said second polarizer forming an acute angle therewith may pass through the liquid crystal assembly, impinge on said reflector, and pass back through the liquid crystal assembly to impinge on said second polarizer, so that ambient light energy loss due to reflected and absorbed energy is limited to that occurring during transmission of the ambient light energy through said first polarizer twice and said second polarizer once, whereby an observer positioned on the side of said second polarizer forming an obtuse angle with the first transparent support plate may observe greater light and dark contrast according to the polarization of the reflected light as determined by electric fields applied between the covering transparent and predetermined array of transparent electrodes.

2. A combination as in claim 1 wherein said reflector has a focal point on the side of said second polarizer forming an obtuse angle with the first support plate, whereby reflected ambient light is concentrated on the back of said second polarizer.

3. A combination as in claim 2 together with an outer case for housing the liquid crystal display, said outer case having an opening therein for passing light incident on the first transparent support plate.

4. A combination as in claim 1 together with an outer case for housing the liquid crystal display, said outer case having an opening therein for passing light incident on the first transparent support plate.