LIQUID CRYSTAL DISPLAY APPARATUS

• US 3,807,831 A
• Filed: 06/20/1972
• Issued: 04/30/1974
• Est. Priority Date: 06/20/1972
• Status: Expired due to Term

• Current Assignee: Babcock Display Products Incorporated
• Original Assignee: Richard A. Soref
• Inventors: Soref, Richard A.
• Primary Examiner(s): Bauer, Edward S.
• Application Number:
  US05/264,679
• Time in Patent Office: 679 Days
• Field of Search: 350/150,16R,16LC
• US Class Current: 349/141
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 2201/124 interdigital

Abstract

A flat screen, electrically controlled, display device is provided that includes a very thin layer of liquid crystalline material of the nematic type. The liquid crystal material is one whose optical phase shift transmission is a sensitive and direct function of the electric field within it, allowing controlled optical transmission in conjunction with polarizers. The nematic material is placed in a flat-sided cell between transparent planar front and rear cell elements which define the thickness of the nematic layer. Birefringence of the nematic liquid crystal is controlled by voltages applied to interleaved arrays of alternate parallel electrodes coated on the inner surface of only one of the transparent cell elements.

Claims

1. Apparatus for optically displaying changes in the optical birefringence of an electric field sensitive liquid crystal comprising, a plurality of elongate electrodes, an optically transparent dielectric substrate for supporting said plurality of elongate electrodes in spaced, substantially parallel relation for permitting homeotropic alignment of the molecules of an electric field sensitive liquid crystal in the absence of an applied electric field to form a first substantially transparent state, an optically transparent dielectric wall closely spaced from and parallel to said optically transparent dielectric substrate, an electric field sensitive liquid crystal having positive dielectric anisotropy disposed between said optically transparent dielectric substrate and said optically transparent dielectric wall, said electric field sensitive liquid crystal having a sufficiently high resistivity to effectively prevent current flow therethrough, said electric field sensitive liquid crystal further having a second state substantially equal in transparency to said first substantially transparent state in the presence of an electric field whose major component is parallel to saId optically transparent dielectric substrate and has an intensity above a predetermined value characterized by alignment of the molecules thereof substantially parallel to said electric field major component, means for providing an electric field between adjacent ones of said plurality of electrodes for changing the optical birefringence of said electric field sensitive liquid crystal, said electric field having a frequency such that the major component of the electric field is parallel to said optically transparent dielectric substrate, and a dielectric enclosure for hermetically sealing said optically transparent dielectric substrate to said optically transparent dielectric wall for completing the enclosure of a thin layer of said electric field sensitive liquid crystal.

2. Apparatus as described in claim 1 wherein said electric field sensitive liquid crystal has a resistivity lying substantially between 109 and substantially 1013 ohm-centimeters.

3. Apparatus as described in claim 2 wherein said elongate electrodes are spaced apart from substantially 10 to substantially 40 microns center-to-center, said elongate electrodes having widths lying substantially between 30 to substantially 50 per cent of said center-to-center spacing.

4. Apparatus as described in claim 2 wherein said thin layer of electric field sensitive liquid crystal has a thickness lying substantially between 0.5 and 1.5 microns.

5. Apparatus of the kind described in claim 1 further including:

mirror means adjacent one of said optically transparent dielectric substrate or said optically transparent dielectric wall, and optical circular polarizer means opposite said mirror means permitting passage of light through said electric field sensitive liquid crystal for providing said change in optical birefringence in the presence of said electric field major component of predetermined value.

6. Apparatus as described in claim 5 wherein said mirror means comprises diffuse reflection means adapting said apparatus for operating with diffuse light for optically displaying said characteristic of an electric field.

7. Apparatus as described in claim 5 wherein said mirror means comprises specular reflection means adapting said apparatus for operation with light from a discrete light source when optically displaying said characteristic of an electric field.

8. Apparatus as described in claim 1 further including:

optical linear analyzer means adjacent one of said optically transparent substrate or said optically transparent dielectric wall, and optical linear polarizer means opposite said optical linear analyzer means permitting passage of light through said electric field sensitive liquid crystal providing said change in optical birefringence in the presence of said electric field major component of predetermined value.

9. Apparatus as described in claim 1 further including:

mirror means adjacent one of said optically transparent substrate or optically transparent wall, optical linear polarizer means opposite said mirror means, and optical linear analyzer means interposed between said mirror means and said one of said optically transparent substrate or optically transparent wall, the optical axes of said optical linear polarizer means and of said optical linear analyzer means being disposed substantially at 45* to said elongate electrodes

10. Apparatus as described in claim 9 wherein said optical axes of said optical linear polarizer means and said optical linear analyzer means are mutually perpendicular.

11. Apparatus as described in claim 9 wherein said optical axes of said optical linear polarizer means and said optical linear analyzer means are parallel.

12. Apparatus as described in claim 9 wherein said mirror means comprises diffuse reflection means adapting said apparatus for operation with diffuse light for optically displaying said characteristic of an electric field.

13. Apparatus as described in claim 9 wherein said mirror means comprises specular reflection means adapting said apparatus for operation with light from a discrete source when optically displaying said characteristic of an electric field.