Active matrix liquid crystal liquid crystal light valve including a dielectric mirror upon a leveling layer and having fringing fields

• US 5,056,895 A
• Filed: 05/21/1990
• Issued: 10/15/1991
• Est. Priority Date: 05/21/1990
• Status: Expired due to Term

• Current Assignee: Transamerica Business Credit Corporation (Aegon Ltd.)
• Original Assignee: Greyhawk Systems, Inc.
• Inventors: Kahn, Frederic J.
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): TRICE, RONALD
• Application Number:
  US07/527,753
• Time in Patent Office: 512 Days
• Field of Search: 350/338, 350/331 R, 350/334, 350/336, 350/339 R
• US Class Current: 349/114
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/136277 formed on a semiconductor substrate, e.g. of silicon
• CPC Class Codes: G02F 2201/48 Flattening arrangements

Abstract

An active matrix liquid crystal light valve is disclosed. The addressing matrix has an array of electrodes to create electric fields across the liquid crystal layer. The light valve has a continuous nonconductive reflector layer, separate and distinct from the electrode array of the active matrix. This light valve has a leveling layer disposed on the active matrix to form a planar surface. The reflector layer is formed as a continuous sheet on the planar surface of the leveling layer. An additional invention is the use of fringing fields to switch substantially all of the liquid crystal, including areas not directly over the electrodes.

Claims

1. A matrix addressed liquid crystal light valve device for reflection mode projection, comprising:

a first substrate;

a transparent second substrate positioned substantially parallel to and spaced apart from said first substrate;

a transparent electrode means positioned proximate said transparent second substrate and between said first and second substrates;

first alignment means positioned proximate said transparent electrode means;

addressing active matrix supported by said first substrate, said addressing active matrix including an array of pixel electrodes;

leveling means located adjacent said addressing active matrix to form a substantially planar surface;

substantially nonconductive reflective means separate and distinct from said array of pixel electrodes, said reflective means formed as a continuous sheet on the substantially planar surface of said leveling means;

second aligning means positioned proximate to said reflective means; and

a layer of liquid crystal material positioned between said first and second aligning means.

2. The device of claim 1, wherein said reflective means is a dielectric mirror.

3. The device of claim 1, wherein said leveling means includes a light blocking means.

4. The device of claim 1, wherein said addressing active matrix includes

a plurality of substantially parallel, equally spaced conductive first busses,

a plurality of substantially parallel, equally spaced second busses, said second busses being substantially orthogonal and electrically insulated from said first busses, and

a field effect transistor formed within each cell area defined by the intersection of an adjacent pair of first busses with an adjacent pair of second busses, one of said first busses and one of said second busses in electrical connection with said field effect transistor,

each pixel electrode of said array of pixel electrodes overlying one of said field effect transistors and in electrical connection with said one of said field effect transistors.

5. The device of claim 1, wherein said addressing active matrix further comprises storage capacitor means.

6. The device of claim 5, wherein said storage capacitor means further comprises light blocking means.

7. The device of claim 1, wherein said liquid crystal material has a dielectric relaxation time greater than 15 ms.

8. The device of claim 1, wherein said liquid crystal material switches to full contrast ratio with less than 6 volts.

9. The device of claim 1, wherein said first substrate is a semiconducting substrate.

10. The device of claim 9, wherein said semiconducting substrate is a single crystal silicon wafer suitable for standard integrated circuit processes.

11. The device of claim 1, wherein the distance between adjacent pixel electrodes of said array of pixel electrodes is sufficiently small that the electric fields created by said pixel electrodes of said addressing active matrix have fringing fields which switch substantially all of the liquid crystal material including areas not directly over said pixel electrodes.

12. The device of claim 1, further comprising a plurality of matrix drivers which provide electrical signals to said addressing active matrix, at least a portion of said plurality of matrix drivers located on said first substrate.

13. The device of claim 11 wherein the distance between the adjacent pixel electrodes of said array of pixel electrodes is approximately equal to or less than the thickness of the layer of liquid crystal.

14. An active matrix addressed liquid crystal light valve device for reflection mode projection, comprising:

a first substrate;

a transparent second substrate positioned substantially parallel to and spaced apart from said first substrate;

a transparent electrode means positioned proximate said transparent second substrate and between said first and second substrates;

first alignment means positioned proximate said transparent first electrode;

an addressing active matrix supported by said first substrate, said addressing active matrix including a plurality of substantially parallel, equally spaced conductive first busses, a plurality of substantially parallel, equally spaced conductive second busses, said first busses being substantially orthogonal and electrically insulated from said second busses, a field effect transistor formed within each cell area defined by the intersection of an adjacent pair of first busses with an adjacent pair of second busses, one of said first busses and one of said second busses in electrical connection with said first effect transistor, and an array of electrodes, each electrode of said array of electrodes overlying one of said field effect transistors and in electrical connection with said one of said field effect transistors;

leveling means located adjacent said addressing active matrix to form a substantially planar surface;

substantially nonconductive reflective means separate and distinct from the array of electrodes, said reflective means formed as a continuous sheet on the substantially planar surface of said leveling means;

second aligning means positioned proximate to said reflective means; and

a layer of liquid crystal material positioned between said first and second aligning means;

the distance between adjacent electrodes of said array of electrodes being sufficiently small that the electric fields created by said electrodes of said addressing active matrix have fringing fields which switch substantially all of the liquid crystal material including areas not directly over said electrodes.

15. In a matrix addressed device, the structure comprising:

first and second substrates;

a layer of liquid crystal material positioned between said first and second substrates;

an addressing active matrix supported by said first substrate, said addressing active matrix including an array of electrodes;

a leveling layer disposed on said addressing active matrix to provide a substantially planar surface; and

a substantially nonconductive reflective means separate and distinct from said array of electrodes, disposed as a continuous layer upon the planar surface of said leveling layer.

16. An matrix addressed liquid crystal light valve device, comprising:

first and second substrates;

a layer of liquid crystal material having a thickness positioned between said first and second substrates; and

means for applying electric fields across said layer of liquid crystal material in order to switch the liquid crystal material, said applying means including an array of spaced apart electrodes, adjacent electrodes of said array of electrodes having a distance therebetween;

said layer of liquid crystal material having a first region directly over said electrodes and a second region directly over the spaces between said adjacent electrodes;

the distance between adjacent electrodes of said array of electrodes being sufficiently small that the electric fields which switch the liquid crystal material in said first region have fringing fields which switch substantially all of the liquid crystal material in said second region.

17. The device of claim 16 wherein said device further comprises light reflective means located between said first and second substrates.

18. The device of claim 16 wherein the distance between adjacent electrodes of said array of electrodes is approximately equal to or less than the thickness of the layer of liquid crystal material.

19. In a matrix addressed liquid crystal light valve device including a layer of liquid crystal material, means for applying electric fields across said layer of liquid crystal material to change the molecular configuration of the layer of liquid crystal material, and an addressing active matrix structure positioned on one side of said layer of liquid crystal material for controlling the operation of said electric field applying means, the improvement comprising:

an array of spaced-apart pixel electrodes forming part of said addressing active matrix and serving as part of said means for applying an electric field, said pixel electrodes being positioned sufficiently close to one another so as to result in fringing fields across the liquid crystal material disposed over the areas between the pixel electrodes, to change the molecular configuration of the liquid crystal material in the areas between the pixel electrodes so that light passing through said areas is affected by the liquid crystal material in a similar manner to light passing through the areas over the nearest adjacent pixel electrode.

20. In a matrix addressed liquid crystal light valve device including a layer of liquid crystal material having a light receiving side and a reflector facing side, means for applying an electric field across said layer of liquid crystal material to change the molecular configuration of said layer of liquid crystal material and thereby affect light passing therethrough, and an addressing active matrix positioned on the reflector facing side of said layer of liquid crystal material for controlling the operation of said electric field applying means, the improvement comprising:

a continuous substantially nonconductive layer having a light reflecting surface separate and distinct from both said addressing active matrix and said means for applying an electric field and located on the reflector facing side of said layer of liquid crystal material with its light reflecting surface facing said liquid crystal material, said non-conductive layer serving as a light reflecting means; and

an array of spaced-apart pixel electrodes forming part of said addressing active matrix and serving as part of said means for applying an electric field, said pixel electrodes being positioned sufficiently close to one another so as to result in fringing fields across the liquid crystal material disposed over the areas between the pixel electrodes to change the molecular configuration of the liquid crystal material in the areas between pixel electrodes so that light passing through said areas is affected by the liquid crystal material in a similar manner to light passing through the areas above the nearest adjacent pixel electrode.

21. In a matrix addressed device, the structure comprising:

first and second substrates;

a layer of liquid crystal material positioned between said first and second substrates;

an addressing matrix including an array of spaced apart electrodes, said addressing matrix supported by said first substrate to define a non-planar surface;

leveling means disposed on said non-planar surface to provide a substantially planar surface; and

a substantially nonconductive reflective means separate and distinct from said addressing matrix, disposed as a continuous layer upon said planar surface.