Image projection display screen employing polymer dispersed liquid crystal layer and electrochromic layer

• US 5,416,617 A
• Filed: 07/16/1993
• Issued: 05/16/1995
• Est. Priority Date: 11/22/1991
• Status: Expired due to Fees

• Current Assignee: Thomson-CSF (Thales SA)
• Original Assignee: Thomson-CSF (Thales SA)
• Inventors: Loiseaux, Brigitte, Oppenlander, Andreas, Huignard, Jean-Pierre, Robin, Philippe
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US08/094,042
• Time in Patent Office: 669 Days
• Field of Search: 359/52, 359/51, 359/38, 359/69, 359/70, 359/96, 359/443, 359/265, 359/267, 359/268, 359/275, 359/452, 359/449
• US Class Current: 349/1
• CPC Class Codes: E06B 2009/2464 featuring transparency control by applying voltage, e.g. LCD, electrochromic panels
• CPC Class Codes: E06B 9/24 Screens or other constructions affording protection against light, especially against sunshine; Similar screens for privacy or appearance; Slat blindsoperating, guiding or securing devices or arrangements for roll-type closures E06B9/56; free-hanging flexible screens A47H23/00
• CPC Class Codes: G02F 1/133308 Support structures for LCD panels, e.g. frames or bezels
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/153 Constructional details
• CPC Class Codes: G02F 1/157 Structural association of cells with optical devices, e.g. reflectors or illuminating devices
• CPC Class Codes: G02F 2201/44 Arrangements combining different electro-active layers, e.g. electrochromic, liquid crystal or electroluminescent layers
• CPC Class Codes: G03B 21/56 Projection screens

Abstract

A diffusing display screen resulting from the combination of a cell comprising a polymer dispersed liquid crystal material which can be made diffusing, and of a cell comprising an electrochromic material which can be made absorbing and reflecting. Outside the operating mode, the display screen according to the invention has the advantage of being transparent, and thus capable of being fixed onto any surface (window, wall, etc.).

Claims

1. A diffusing display screen comprising a combination of

a cell (C₁) which comprises a polymer film (P) having an optical index np, in which are dispersed microballs which are oblong in shape, the larger axis thereof being laid out in parallel to the plane of the film, wherein said microballs contain oblong and birefringent liquid crystal molecules of extraordinary index n_e such that n_e is equal to n_p, and

a cell (C₂) which comprises a layer of electrochromic material (E_c), and transparent electrodes (F₂) which allow a voltage to be applied to said cell (C₂) so as to switch said cell (C₂) from a transparent state to an absorbing and reflecting state, wherein both of said cells (C₁) and (C₂) being fixed onto a surface,

wherein said diffusing display screen is for use with a standard image projector and operates in a reflection mode which allows reflection of images whose size may be variable.

2. The diffusing screen of claim 1, wherein said surface is a window.

3. The diffusing screen of claim 1, wherein said surface is a wall.