Optical: systems and elements – Holographic system or element – Using a hologram as an optical element
Patent
1993-02-05
1994-11-01
Sikes, William L.
Optical: systems and elements
Holographic system or element
Using a hologram as an optical element
359 81, 359100, 430 20, G02F 11341
Patent
active
053611527
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for producing liquid-crystal cells using ferroelectric liquid crystals (FLC).
BACKGROUND OF THE INVENTION
Liquid-crystal cells using FLC have drawn increasing attention as elements that can be used as displays in watches, hand-held calculators, various OA (office automation) equipment and television sets. A liquid-crystal cell using FLC is currently manufactured by a process that comprises the steps of placing a pair of electrode plates in such a way that their electrode sides face each other, bonding the plates together by means of a sealant provided in the periphery to leave a central hollow portion that is to be filled with a liquid crystal, and injection FLC into the follow portion through an inlet in the sealed portion by capillary action under high-temperature and high-vacuum conditions. A problem with this method is that since the gap between the two electrode plates for the FLC liquid-crystal cell is so small (ca. 2 .mu.m) compared to cells using conventional twisted nematic liquid crystals that it takes quite a long time for filling the cell with FLC even if pressure is applied. Further, FLC is so viscous compared to nematic liquid crystals even if it is heated for injection that defoaming (removal of air and other gases that are contained in the liquid crystal) is difficult to achieve or can only be performed unevenly. It is known from EP-A-0 292 244 to prepare liquid-crystal cells without injecting FLC by capillarity by forming a coated FLC layer on one electrode plate. However, there is no mentioning of heating for defoaming said FLC layer and to provide homogeneity in its structure. Also, FLC layer and adhesive layer are formed on different electrodes according to EP-A-0 292 244.
SUMMARY OF THE INVENTION
The present invention has been accomplished under these circumstances on the basis of the finding that excellent liquid-crystal cells for use of ferroelectric liquid crystals can be produced by combining the following two techniques, i.e., preliminarily forming a coated FLC layer on electrode plates without injecting FLC by capillarity, and heating said coated FLC layer for deforming and to provide homogeniety in its structure.
The present invention relates to a process for producing a liquid-crystal cell which comprises the steps of: electrode plate that has an electrode; surrounded by said sealant portion, with a spacer being preliminarily provided in said portion; or the portion surrounded by said sealant portion; or surrounded by said sealant portion and thereafter providing a spacer over said composition; the coated plate during or after evacuation up to the temperature at which the liquid-crystal composition exhibits an isotropic liquid or nematic phase; other electrode which has an electrode faces the side of said one electrode containing the thermally defoamed coated layer of the liquid-crystal composition and compressing the two electrode plates together; and
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1a-1c show schematically the major steps of the process of the present invention, in which FIG. 1a and 1b are plan views and FIG. 1c is a perspective view.
DETAILED DESCRIPTION
In step (b), the spacer can be provided by one or more of the following methods: contains it; partially exposed to light, followed by development of the exposed or non-exposed area to form a spacer (directly), which is then coated with the composition (the photosensitive resin may be positive-type or negative-type action); and partially etched to form a spacer (directly) and the composition is subsequently coated.
The purpose of providing the spacer is to provide a cell of uniform thickness.
Methods i) and iii) may be implemented by either a wet system (using Freon gases as a carrier) or a dry system (dusting air).
In method iv), either positive-type or negative-type photoresists can be used as photosensitive resins. An example of the positive-type photosensitive resins is AZ 1300 SF of Hoechst AG and an example of the negative-type photos
REFERENCES:
patent: 4691995 (1987-09-01), Yamazaki et al.
patent: 4917473 (1990-04-01), Watanabe
Patent Abstract of Japan, Production of Liquid Crystal Display Panel, vol. 10, (1986), S. 506.
Escher Claus
Harada Takamasa
Illian Gerhard
Ohlendorf Dieter
Rieger Heinz
Duong Tai V.
Hoechst Aktiengesellschaft
Sikes William L.
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