Polymer dispersed liquid crystal display device with asymmetric optical diffuser

• US 5,629,785 A
• Filed: 05/04/1995
• Issued: 05/13/1997
• Est. Priority Date: 05/04/1995
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Jelley, Kevin W., Valliath, George T., Chen, Alan G.
• Primary Examiner(s): GROSS, ANITA P
• Application Number:
  US08/434,876
• Time in Patent Office: 740 Days
• Field of Search: 359/69, 359/51, 359/67
• US Class Current: 349/86
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606

Abstract

A display device comprises a polymer dispersed liquid crystal film that includes one or more translucent regions and one or more transparent regions. The back side of the polymer dispersed liquid crystal film is illuminated by collimated light. The front side of the polymer dispersed liquid crystal film is optically coupled to an asymmetric optical diffuser. The asymmetric optical diffuser comprises a plurality of light paths that transmit collimated light emanating through a transparent region of the film, but excludes diffuse light emanating from a translucent region. A preferred asymmetric optical diffuser comprises glass microspheres in a black matrix. In this manner, the asymmetric diffuser substantially improves contrast between a transparent region and a translucent region of a display.

Claims

1. A display device comprising

a polymer dispersed liquid crystal film comprising a transparent polymeric matrix and microdroplets containing a liquid crystal material dispersed within the transparent polymeric matrix, said polymer dispersed liquid crystal film having a front side adapted for emitting light for viewing a display and a back side opposite the front side,

a collimated light source illuminating the back side of the polymer dispersed liquid crystal film, and

an asymmetric optical diffuser optically coupled to the front side of the polymer dispersed liquid crystal film to receive light emitted therefrom, said asymmetric optical diffuser comprising a plurality of light paths that transmit collimated light transmitted through the polymer dispersed liquid crystal film and exclude diffuse light emanating from the polymer dispersed liquid crystal film nonparallel to the collimated light.

2. A display device comprising

a polymer dispersed liquid crystal film comprising a transparent polymeric matrix and microdroplets containing a liquid crystal material dispersed within the transparent polymeric matrix, said polymer dispersed liquid crystal film having a front side wherefrom light emanates for forming a display and a back side opposite the front side, said polymer dispersed liquid crystal film further comprising at least one region switchable in response to an applied electric field between a translucent condition and a transparent condition,

a collimated light source for producing a collimated light beam that illuminates the back side of the polymer dispersed liquid crystal film along an axis generally perpendicular to said back side, and

an asymmetric optical diffuser optically coupled to the front side of the polymer dispersed liquid crystal film to receive light emanating therefrom, said asymmetric optical diffuser comprising an opaque matrix and a plurality of transparent microspheres arranged in the opaque matrix to form light paths through the asymmetric optical diffuser that selectively transmit collimated light along the axis, whereby collimated light transmitted through the region in the transparent condition is transmitted through the asymmetric optical diffuser to create a bright area for a display and diffuse light emanating from the region in the translucent condition in directions nonparallel to the axis are excluded to create a dark area for a display.

3. A display device in accordance with claim 2 further comprising first and second transparent electrodes affixed respectively to the front side and the back side of the polymer dispersed liquid crystal film and adapted for coupling to a remote electrical power source for applying an electric field to switch said region between the translucent condition and the transparent condition.