Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified...
Reexamination Certificate
1999-06-16
2002-10-01
Wu, Shean C. (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
C252S299610, C252S299630, C252S299660, C544S242000, C544S298000, C544S335000, C546S192000, C546S251000, C549S013000, C549S369000, C549S428000, C570S127000, C570S129000, C570S131000
Reexamination Certificate
active
06458433
ABSTRACT:
This application is a 371 application of International Application No. PCT/JP97/04633 filed Dec. 16, 1997.
TECHNICAL FIELD
The present invention relates to liquid crystalline compounds and liquid crystal compositions. More specifically, the invention relates to novel liquid crystalline compounds simultaneously having butylene group or propylenoxy group, and 2,3-difluorophenyl group in the compounds; to liquid crystal compositions comprising the compound; and further to liquid crystal display devices fabricated by using the liquid crystal composition.
BACKGROUND ART
Display devices produced by employing optical anisotropy and dielectric anisotropy which are characteristics of liquid crystalline compounds (the term “liquid crystalline compounds” is used in this specification as a general term for the compounds which exhibit a liquid crystal phase and for the compounds which do not exhibit a liquid crystal phase but are useful as component of liquid crystal compositions) have widely been utilized for tabletop calculators, word processors, and TV sets including watches, and the demand for the devices are rising year after year.
Liquid crystal phase is broadly classified into nematic phase, smectic phase, and cholesteric phase. Among them, nematic phase has most widely been employed for display devices. As display mode applied for liquid crystal display, TN (twisted nematic) display mode, DS (dynamic scattering) display mode, guest-host display mode, and DAP (Deformation of Aligned Phases) display mode have been developed corresponding to electro-optic effects.
In recent years, coloring of liquid crystal displays has rapidly been advanced, and thin film transistor (TFT) display mode and super twisted nematic (STN) display mode are main streams in TN display mode as display mode. On the other hand, CRT which is a main stream of current television screen is expected to be replaced by liquid crystal displays sooner or later. In order to realize the replacement, liquid crystal displays must have display characteristics comparable to those of CRT.
In the research and development of liquid crystal displays, one's energies have been devoted to the improvement of response speed, contrast, and viewing angle as important subject. Among them, response speed and contrast became such an extent as equal to those of CRT as a result of repeated improvements in TFT display mode. However, a wide viewing angle comparable to that of CRT has not yet been actualized, whereas some improvements such as an improvement in the orientational direction of liquid crystal molecules and the use of a phase difference plate have been made as to viewing angle.
Although it is an active matrix mode similar to that of TFT display mode, in-plane-switching (IPS) display mode which is characterized in that comb type electrodes are formed only one side of substrate is lately performed on the stage as a mode for actualizing a wide viewing angle (G. Baur, Freiburger Arbeistagung Flussigkristalle, Abstract No. 22 (1993) and M. Oh-e et al., ASIA DISPLAY '95, 577 (1995)). When liquid crystalline compounds having a negative dielectric anisotropy value (&Dgr;&egr;) was used in IPS display mode, a dramatically wide viewing angle was obtained.
However, this IPS display mode has such a defect that response speed is considerably low compared with conventional TFT display mode or STN display mode. Then, liquid crystalline compounds having a negative and large &Dgr;&egr; and a low viscosity have been required in IPS display mode.
Also, since active matrix driving mode is employed in IPS mode as described above, liquid crystalline compounds having a high voltage holding ratio (V. H. R.) are more preferable.
Various compounds having a negative dielectric anisotropy value are already known. In Laid-open Japanese Patent Publication No. Hei 2-4724 and Tokuhyo (Laid-open Japanese WO publication) No. Hei 2-503441, compounds having 2,3-difluoro-1,4-phenylene group in their partial structure are disclosed as liquid crystal compound having a negative &Dgr;&egr;.
It is considered that in the compounds having such partial structure, fluorine atoms substituted at positions 2 and 3 act so as to increase dipole moment in the direction of the minor axis of molecules to make dipole moment of the major axis smaller than the dipole moment in the direction of minor axis, and as the result, the compounds come to have a negative dielectric anisotropy value. However, compounds having such partial structure become slightly narrow in their temperature range exhibiting a liquid crystal phase compared with compounds in which hydrogen atoms of phenylene group are not replaced by fluorine atoms, their miscibility with other liquid crystalline compounds particularly at very low temperatures can hardly be said to be excellent, and sometimes such phenomena that smectic phase is developed and crystals are separated in liquid crystal compositions in a low temperature region are observed.
Compounds expressed by the following formula (a) are described in Tokuhyo No. Hei 2-503441:
wherein R and R′ represent an alkyl group and alkoxy group, respectively.
Whereas structural formula of the compounds is described in the publication mentioned above, physical properties and the likes necessary for judging the utility of the compounds as liquid crystalline compound are not described at all therein. Based on the consideration by the present inventors, whereas an improvement in miscibility by the compounds of the formula (a) described above compared with compounds having no 1,2-ethylene group can be surmised since the compounds of the formula (a) have 1,2-ethylene group as bonding group in skeleton structure, their effect can not be said to be sufficient.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide liquid crystalline compounds which are wide particularly in temperature range of liquid crystal phase, have a low viscosity, have a negative and large &Dgr;&egr;, and are improved in solubility at low temperatures; to provide liquid crystal compositions comprising the compound; and to provide liquid crystal display devices fabricated by using the liquid crystal composition, thereby to overcome the problems in conventional technologies described above.
Then, compounds expressed by the general formula (1) and simultaneously having butylene group or propylenoxy group, and 2,3-difluoro-1,4-phenylene group in the structure of compounds were diligently investigated by the present inventors. As the result of the investigation, it has been found out that the compounds are characterized in that they are wide in temperature range exhibiting a liquid crystal phase, are low in viscosity, and have a negative and large &Dgr;∈, as well as they are remarkably excellent in miscibility at low temperatures, leading to the accomplishment of the present invention.
That is, the present invention is summarized as follows:
[1] A liquid crystalline compound expressed by the general formula (1)
wherein R
1
represents an alkyl group having 1 to 15 carbon atoms in which alkyl group, not-adjacent any methylene group may be replaced by oxygen atom or vinylene group, and any hydrogen atom in the alkyl group may be replaced by fluorine atom; ring A
1
, ring A
2
, and ring A
3
independently represent trans-1,4-cyclohexylene group, trans-1,4-silacyclohexylene group, pyrimidine-2,5-diyl group, pyridine-2,5-diyl group, 1,3-dioxane-2,5-diyl group, tetrahydropyran-2,5-diyl group, 1,3-dithian-2,5-diyl group, or tetrahydrothiopyran-2,5-diyl group, or 1,4-phenylene group in which one or more hydrogen atoms on the six-membered ring may be replaced by a halogen atom; X
1
, X
2
, and X
3
independently represent —(CH
2
)
4
—, —(CH
2
)
3
O—, —O(CH
2
)
3
—, or single bond; Y
1
represents hydrogen atom or an alkyl group having 1 to 15 carbon atoms in which alkyl group not-adjacent any methylene group may be replaced by oxygen atom or vinylene group; m and n are independently 0 or 1; and any atom which constitutes this compound may be replaced by its isotope.
Kato Takashi
Matsui Shuichi
Miyazawa Kazutoshi
Nakagawa Etsuo
Takeshita Fusayuki
Chisso Corporation
Wenderoth , Lind & Ponack, L.L.P.
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