Method of forming a display using cholesteric material

Details Method of forming a display using cholesteric material Method of forming a display using cholesteric material

2001-12-21

2003-11-04

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

With viewing layer of specified composition

C428S001400, C252S299010, C349S088000, C349S111000, C430S020000

Reexamination Certificate

active

06641873

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to liquid crystal displays and, more particularly, to a liquid crystal display, which produces a more esthetically pleasing image.
BACKGROUND OF THE INVENTION
Liquid crystal displays are well known in the art and have many applications. They are found in watches, clocks, and provide the display for many devices. In one particular type of display using a liquid crystal, an image is preformed in a patterned transparent conductive layer and a liquid crystal layer is coated over such patterned transparent conductive layer. Currently, information is displayed using assembled sheets of paper carrying permanent inks or displayed on electronically modulated surfaces such as cathode ray displays or liquid crystal displays. Other sheet materials can carry magnetically written areas carrying ticketing or financial information, however magnetically written data is not visible.
A structure is disclosed in PCT/WO 97/04398, entitled “Electronic Book With Multiple Display Pages” which includes a recitation of prior art of thin, electronically written display technologies. Disclosed is the assembling of multiple display sheets that are bound into a “book”, each sheet provided with means to individually address each page. In PCT/WO 97/04398 prior techniques are set forth for 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 . . . ”. It would be advantageous to generate a display sheet that could use opaque electrical conductors that were printed.
Fabrication of flexible, electronically written display sheets is disclosed in U.S. Pat. No. 4,435,047. A first sheet has transparent indium-tin-oxide (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. Currently, Taliq products form electrical interconnection by offsetting the two sheets and contacting trace conductors from each of 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. Because most display structures are formed of glass, two sheets are used and are offset to permit connection to two separate and exposed sets of traces that are disposed on separate sheets.
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, multilayer structure prevents connection to the inner conductive layer.
In the case of electronic display means, power must be provided to view images. Printed sheets receive ink and cannot be rewritten. In the case of magnetically written media such as magnetic areas on the back of credit cards, the information is not readable. It would be advantageous to provide a flexible sheet that can be rewritten using electronic techniques. While these devices are now available and effective, they still have deficiency in image quality.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a simple yet effective method for improving the image quality of a liquid crystal display.
This object is achieved by A method of making a display, comprising the steps of:
a) providing a transparent support and providing a conductive transparent layer formed thereover;
b) patterning the transparent conductive layer;
c) coating a soluble layer including liquid crystal material dispersed in a polymer matrix over the patterned transparent layer and drying such coated soluble layer;
d) providing an opaque hydrophobic conductive layer over the dried coated soluble layer;
e) patterning the opaque hydrophobic layer to form conductors leaving exposed portions of the transparent dried coated soluble layer, the position of the conductors relative to the transparent conductive layer defines image pixels; and
f) removing by a solvent the exposed portions of the dried coated soluble layer so that when a potential for each pixel is applied between the patterned transparent conductive layer and patterned corresponding opaque hydrophobic conductors, an image is provided by the dried coated soluble layer which is viewable by an observer.
ADVANTAGES
The present invention, by the addition of a simple solvent removing step, permits improvement in image quality by changing the spectral response of the display by removing the exposed portions of the dried coated water soluble layer so as to minimize haze and improve the clarity of the image when viewed by an observer.


REFERENCES:
patent: 4435047 (1984-03-01), Fergason
patent: 5437811 (1995-08-01), Doane et al.
patent: 5986729 (1999-11-01), Yamanaka et al.
patent: WO 97/04398 (1997-02-01), None

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