DISPLAY DEVICES UTILIZING LIQUID CRYSTAL LIGHT MODULATION

• US 3,731,986 A
• Filed: 04/22/1971
• Issued: 05/08/1973
• Est. Priority Date: 04/22/1971
• Status: Expired due to Term

• Current Assignee: James L. Fergason
• Original Assignee: James L. Fergason
• Inventors: Fergason, James L.
• Primary Examiner(s): Bauer, Edward S.
• Application Number:
  US05/136,441
• Time in Patent Office: 747 Days
• Field of Search: 350/150,157,160 252/408 340/324R
• US Class Current: 349/33
• CPC Class Codes: C09K 19/02 characterised by optical, electrical or physical properties of the components, in general
• CPC Class Codes: G02F 1/133 Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements arrangements or circuits for control of liquid crystal elements in a matrix, not structurally associated with these elements G09G3/36
• 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

Abstract

Optical display devices for converting electrical intelligence into optical images with the use of a shutter device comprising a layer of liquid crystal material sandwiched between opposing parallel plates coated with transparent conducting films. These plates, with the liquid crystal material therebetween, are disposed between and parallel to a pair of polarizers such that when an electrical potential is established across the conducting films and the liquid crystal layer, the device will change from a light transmitting to opaque medium, or vice versa, depending upon the orientation of the two polarizers. By forming the two conducting films in the shape of a desired optical image, that image can be made to appear or disappear, depending upon whether a potential is established between the conducting films. Furthermore, by creating separate conducting areas, as by etching the conducting films, any given number of conductive regions can be switched ON while other regions are not affected to produce any one of a number of different images with the same liquid crystal sandwich assembly. Finally, by etching a pattern of strips of transparent conducting material on the two opposing plates, by orienting the strips on the respective plates at right angles to each other, and by selectively applying pulsed voltages to the strips on the respective plates, the area of liquid crystal layer can be scanned point by point to produce with the same display any one of a number of optical images such as numerals, letters or the like. The invention has particular utility in computer and calculator read-outs, for example, since the display can be energized at a voltage level compatible with that used to drive the integrated circuitry used in such devices without the necessity for relatively high voltage driving circuitry.

Claims

2. The device of claim 1 wherein said liquid crystal material comprises a mixture of 40 percent bis-(4'"'"''"'"'-n-octyloxybenzal)-2-chlorophenylenediamine, 50 percent p-methylbenzal-p'"'"''"'"'-n-butylaniline and 10 percent p-cyanobenzal-p'"'"''"'"'-n-butylaniline.

3. The device of claim 1 wherein said polarizers comprise polarizing sheets on the sides of said plates opposite said liquid crystal material.

4. The device of claim 1 wherein said polarizers comprise dichroic films.

5. The device of claim 4 wherein said dichroic films are deposited on said conducting films and are in contact with the liquid crystal material.

6. The device of claim 1 wherein the crystal material is nematic and of positive dielectric anisotropy.

7. The device of claim 1 wherein one of said polarizers polarizes light at right angles to the other, whereby light will pass through the entirety of said sandwich structure with no electrical potential established between said films, said films acting to block the passage of light through selected areas of said sandwich structure upon application of a potential difference between said films.

8. The device of claim 1 wherein said films on the respective plates are in the form of a desired image.

9. The device of claim 1 wherein said films on the respective plates are in the form of mutually insulated strips which cross each other.

10. The device of claim 9 including means for applying pulses to the mutually insulated strips on the respective plates.

11. The device of claim 10 including means for applying pulses of one polarity in succession to the strips on one of said plates, and means for simultaneously and selectively applying pulses of the opposite polarity to the strips on the other of said plates, each of said pulses of the opposite polarity being in phase with at least one of the pulses of said one polarity, whereby light transmitting characteristics of said sandwich structure will be varied at selected crossings of the strips on the respective plates to form an optical image.

12. The device of claim 11 wherein said pulses of one polarity and said pulses of the opposite polarity occur during a frame period, and including means for continually repeating said frame period.

13. The device of claim 1 wherein one of said plates is coated with mutually insulated film portions of transparent conducting material arranged to form any one of a plurality of images, the other of said plates being coated with an unbroken area of conducting material which covers the entire area of the portions on the opposite plate, and means for selectively establishing a potential between the film on said other plate and selected ones of said portions on said one plate.