Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Patent
1996-11-14
1998-12-08
Dang, Hung X.
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
349 33, 349139, 349 1, 349 20, G02F 11333, G02F 1137
Patent
active
058477861
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a liquid crystal orienting method for changing the display mode of a reversible polymer dispersed liquid crystal film employed in a liquid crystal display medium, and a liquid crystal orienting apparatus.
BACKGROUND ART
Reversible display elements to which visible information is rewritable have become widely noticed. Mode of display of those reversible display elements changes when energy is applied temporarily to those reversible display elements by an external energy source, and the displayed information is held after energy has been removed to maintain a recording state. Such a displayed information storing property of these reversible display elements is utilized.
For example, one of the previously proposed reversible display elements employs a polymer-fatty-acid film of a material prepared by dispersing a fatty acid in a polymer matrix to utilize the properties of the fatty acid that changes between a white, opaque phase and a transparent phase. Another previously proposed reversible display element utilizes the reversible opening and closing of lactone rings of a leuco dye by a developer/subtracter agent. A third previously proposed reversible display element employs a polymer liquid crystal. These liquid crystal display elements have problems in durability to rewriting, preservation and aptitude for allowing rapid erasing of displayed information. Various liquid crystal display mediums provided with a liquid crystal display element employing a polymer dispersed liquid crystal film (hereinafter referred to as "PDLC film") formed by dispersing a smectic liquid crystal or the like in a polymer matrix are proposed in, for instance, JP-A No. 4-71899, and JP-A Nos. 5-294092 and 5-301489 applied for patent by the applicant of the present patent application.
The principle of recording visible information on and erasing visible information from the PDLC film uses light scattering and light transmission (change in the light absorptive power when a dichroic dye is used in combination with the liquid crystal and guest-host effect is available) due to the orderly change of the orientation of the liquid crystal molecules (change between a homeotropic orientation state or a homogeneous orientation state, and a random orientation state) by heat and an electric field.
When an opaque state (light scattering state) is used as a recording state, and a transparent state (light transmitting state) is as an erasing state, information can be written to the PDLC film with a heating means, such as a thermal head capable of spot-heating, and information can be erased from the PDLC film by holding the PDLC film, for instance, between electrodes and applying an electric field of an intensity exceeding a threshold for orienting the liquid crystal.
Accordingly, the liquid crystal display element employing a PDLC film may be called electrical liquid crystal display.
A liquid crystal display medium provided with a PDLC film and a conductive layer is disclosed in JP-A No. 4-71899. A transparent state in which this PDLC film is set by orienting the liquid crystal thereof by applying an electric field thereto is used as an erasing state or a recording state. A method of orienting the liquid crystal of the liquid crystal display medium grounds a conductive layer in contact with the PDLC film, and disposes the PDLC film between the conductive layer and an electrode or a surface charger included in an apparatus. This method is obviously analogous with a method of orienting the liquid crystal of a liquid crystal display panel. In JP-A No. 4-71899, the conductive layer underlying the PDLC film has a portion extending beyond the PDLC film and exposed on the surface of the liquid crystal display medium to form a terminal. The liquid crystal display medium must accurately be positioned to bring a grounding electrode to the terminal. There is the possibility of unsatisfactory orientation of the liquid crystal (unsatisfactory erasing or writing) due to faulty contact, and the deterioration of
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Miyanowaki Shin
Shimada Naoki
Dai Nippon Printing Co. Ltd.
Dang Hung X.
Duong Tai V.
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