Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-08-10
2001-04-10
Malinowski, Walter J. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06215540
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to image displays which can selectively transmit or reflect light.
BACKGROUND OF THE INVENTION
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 writable areas to carry 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 is a thorough recitation of the 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. The patent recites prior art in forming thin, electronically written pages, including flexible sheets, image modulating material formed from a bistable liquid crystal system, and thin metallic conductor lines on each page. Various ways are disclosed to produce said conductor lines including photolithography, but not selective exposure and photographic development of traces from a photosensitive emulsion. One disadvantage of this structure is that individual pages are bound together and that many multi-layer conductors must pass across the pages to interconnect at the spine of the book.
Fabrication of flexible, electronically written display sheets are 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 bonded to the liquid crystal material. Electrical potential applied to opposing conductive areas operate on the liquid crystal material to expose display areas. The display ceases to present an image when de-energized. Kaychem Industries form electrical flexible displays 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
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.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a display apparatus which uses a minimum number of layers for changing the transmissivity of image forming light.
Another object is to provide a display that can be re-written using electronic means.
These objects are achieved by a display for presenting image forming light to a viewer, comprising:
(a) a transparent substrate;
(b) a transparent, electrically conductive layer formed over the transparent substrate;
(c) a light modulating layer formed over a portion of the transparent, electrically conductive layer being effective in a first stable state to reflect light and in a second stable state to transmit light;
(d) a layer formed over the light modulating layer which includes separate conductive portions; and
(e) electrical conduction means being adapted to be selectively connected to separate conductive portions and being effective in a first condition to apply a first field across selected portions of the light modulating layer which correspond to separate conductive portions to be in the first stable state to reflect light and to apply a second field across selected separate conductive portions of the light modulating layer which correspond to separate conductive portions to be in the second stable state to transmit light.
Displays made in accordance with the present invention can be used to provide a rewritable image display sheet. The sheet can be formed using inexpensive, fast photographic means to expose and develop a display. A single large volume of sheet material can be coated and formed into various types of sheets and cards.
Advantageously, sheets which form displays can be made from simple coatings, and they receive and retain a viewable image with a simple writer and retain the image data without a power source. Displays in the form of sheets in accordance with the present invention are inexpensive, simple and fabricated using low-cost processes
REFERENCES:
patent: 3989356 (1976-11-01), Altman
patent: 4881110 (1989-11-01), Braatz et al.
patent: 5912716 (1999-06-01), Stephenson
patent: 5943067 (1999-08-01), Kong
patent: 5958634 (1999-09-01), Stephenson
patent: 5990994 (1999-11-01), Stephenson
patent: 6067134 (2000-05-01), Akiyama et al.
Eastman Kodak Company
Malinowski Walter J.
Owens Raymond L.
Shaw Stephen H.
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