Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-06-26
2001-11-27
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S187000
Reexamination Certificate
active
06323928
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to image displays that can selectively transmit or reflect actinic light.
BACKGROUND OF THE INVENTION
Currently, images can be displayed sheets of paper carrying permanent inks or displayed on electronically modulated surfaces such as cathode ray displays or liquid crystal displays. Sheet materials can carry magnetically written areas carrying ticketing or financial information, however magnetically written data is not visible.
For an example of electronically writable displays, see PCT/WO 97/04398, entitled “electronic Book With Multiple Page Displays.” This reference discloses the assembling of multiple electronically written display sheets into a “book”, each sheet provided with means to individually address each page. The disclosure sets forth prior art in forming thin, electronically written pages, including flexible sheets, image modulating material formed from a bi-stable liquid crystal system, and thin metallic conductor lines on each page. The device described requires “. . . transparent conducting polymers . . . ” formed over the light modulating material. Formation of transparent conductors of the required conductivity require complex vacuum sputtering and photo-lithographic processes.
Fabrication of flexible, electronically written display sheets is disclosed in U.S. Pat. No. 4,435,047. A first sheet has transparent ITO conductive areas and a second sheet has electrically conductive inks printed on display areas. The sheets can be glass, but in practice have been formed of Mylar polyester. A dispersion of liquid crystal material in a binder is coated on the first sheet, and the second sheet is pressed onto the liquid crystal material. Electrical potential applied to opposing conductive areas operates on the liquid crystal material to expose display areas. The display ceases to present an image when de-energized. The Taliq Company supplied products formed using the two sheet method. Offsetting the two sheets permitted connection to conductive traces on the two sheets.
The prior art typically requires multiple, separate layers to build up the display. The electrical traces and transparent conductive layers are typically formed through repeated vacuum deposition and photolithography of materials on the substrate. These processes are expensive and require long processing times on capital intensive equipment.
The prior art discloses isolating each conductor on separate sides of the display, and connecting the traces to drive electronics using solder connections, wire bonds or pressure contact. Such connections do require that both sets of traces be exposed on a surface for the connection process. The uniform, multi-layer structure prevents connection to the inner conductive layer.
A problem with the prior art is that layers that should not be distinguished frequently are distinguishable and can be seen by a viewer thereby degrading the quality of the viewed image.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a display which has opaque conductive images formed in an effective manner with a minimum number of steps.
This object can be achieved by a method of forming a display in which images can be selectively presented to a viewer, comprising the steps of:
a) providing a transparent substrate;
b) forming a transparent, electrically conductive layer over the transparent substrate;
c) forming a light modulating layer including liquid crystal material in a polymer binder over the transparent, electrically conductive layer;
d) forming conductive colored segments over the light modulating layer by directly depositing colored conductive material in an imagewise pattern, the pattern providing viewable and conductive images;
e) forming a colored dielectric layer over the conductive colored segments and the light modulating layer, the color of the dielectric layer being selected in relation to the color of the viewable color conductive segments so that when the light modulating layer is effective in a first condition, the viewing of the viewable color conductive segment images is prevented and in a second condition permits the viewing of the viewable color conductive segment images; and
f) providing electrical connections so that an electrical field can be applied across selected ones of such viewable and conductive segments and the transparent, electrically conductive layer to cause the light modulating layer underlying the selected ones of the viewable and conductive images to change from the first condition to the second condition so as to present such color conductive segment images for viewing by the viewer.
In one embodiment of this invention the light modulating layer is oriented to a light transmitting state. This is accomplished by heating the light modulating layer to a temperature in a range of 80 degrees C. or higher. In this temperature range the chiral pneumatic material is switched from the planar state reflecting light to the focal-conic light transmitting state.
The disclosed structure has the advantage of presenting esthetically pleasing images to a viewer without the images being adversely affected by a problem of the viewer distinguishing between different colors of different layers in the display.
With the light modulating layer in the light transmitting state, both the conductive colored segments and the colored dielectric layer are viewable. It is desirable to have the conductive colored segments indistinguishable from the colored dielectric layer.
As the light modulating layer is subjected to an electrical field in the regions of the selected conductive colored segments it will cause the light modulating layer to change from a focal conic light transmitting state to a planar state reflecting light in the region of the selected conductive colored segment. In accordance with the invention a display includes two distinguishable colors and is easy to read and discern the intended image. The first distinguishable color is that of the conductive colored segments and the colored dielectric layer. The second distinguishable color is the light modulating layer that has been changed to the planar state reflecting light in the region of the selected conductive colored segment.
REFERENCES:
patent: 4435047 (1984-03-01), Fergason
patent: 5437811 (1995-08-01), Doane et al.
patent: 5695682 (1997-12-01), Doane et al.
patent: 6236442 (2001-05-01), Stephenson et al.
patent: WO 97/04398 (1997-02-01), None
Chowdhury Tarifur R.
Eastman Kodak Company
Owens Raymond L.
Sikes William L.
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