Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Reexamination Certificate
1999-06-02
2004-02-17
Wu, Shean C. (Department: 1756)
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
C252S299610, C570S129000, C570S135000, C549S369000
Reexamination Certificate
active
06692657
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a liquid crystalline compound and a liquid crystal composition, and more particularly, to a novel liquid crystalline compound simultaneously having an alkenyl group and 2,3-difluorophenyl group, a liquid crystal composition containing such a compound, and a liquid crystal display device constituted from such a liquid crystal composition.
BACKGROUND ART
When a voltage is impressed to a conventional TN mode TFT display or a conventional STN display, liquid crystal molecules rotate to extend in the direction perpendicular to the substrate. When such liquid crystal molecules rise diagonally (i.e., such that they extend perpendicular to the substrate), there arise problems in that the optical properties of the liquid crystal molecules differ depending on the angle from which the liquid crystal panel is viewed, and in that the view angle is narrow.
As systems for realizing a wide view angle, the In-Plane-Switching (IPS) system characterized in the formation of comb style electrodes on one substrate (G. Baur, Freiburger Arbeistagung Flussigkristalle, Abstract No. 22 (1993), M. Oh-e, et al., ASIA DISPLAY '95, 577 (1995)), and the Vertically Aligned (VA) system (K. Ohmuro, et al., SID 97 DIGEST, 845 (1997)) have attracted attention, and have been put into practical use.
In the IPS system, since liquid crystal molecules rotate within the surface plane of the glass substrate, the view angle is greatly widened. In the VA system, liquid crystal molecules rotate from the vertical direction to the horizontal direction to the substrate, and a wide view angle is realized by controlling orientation in a kind of multi-domain system.
However, as compared to CRTs, these display systems still have problems, and there are the demands for improvement of response time, improvement of contrast, and decrease of driving voltage.
The liquid crystalline compound employed in IPS and VA systems must have the large negative value of dielectric anisotropy (&Dgr;∈) for its display properties, and a low viscosity for improving response time. Since active matrix driving is utilized as the driving method, the compound must have a high voltage holding ratio (V.H.R.) in order to improve contrast. Various compounds have been known to have negative values of dielectric anisotropy, and the following compounds (a) and (b) are disclosed in Japanese Patent Application Laid Open No. 2-4725 and Japanese-translated PCT Patent Application Laid-open No. 2-503441:
Where, R′ represents an alkyl group or an alkoxy group.
Although each of the above liquid crystalline compounds, (a) and (b), has 2,3-difluoro-1,4-phenylene group as part of its structure, and has a negative &Dgr;∈, |&Dgr;∈| is not sufficiently large and viscosity is high. Furthermore, mutually good solubility its with other liquid crystalline compounds, especially mutually good solubility at very low temperature, is not sufficiently high, and a liquid crystal composition containing such compounds is so unstable that low-temperature storage results in precipitation of crystals or appearance of a smectic phase.
In order to solve the problems involved in the prior art techniques, an object of the present invention is to provide a liquid crystalline compound having a wide temperature range within which a liquid crystal phase exists (hereinafter called a “liquid crystal phase temperature range”), a large negative &Dgr;∈, low viscosity, and mutually good solubility at low temperature, which can contribute to improving response time and contrast and lowering driving voltage in IPS and VA systems and can contribute to improving steepness of the V-T (voltage-transmissivity) curve and contrast by increasing the K
33
/K
11
value in the STN system; a liquid crystal composition containing such liquid crystalline compounds, and a liquid crystal display device constituted from such a liquid crystal composition.
DISCLOSURE OF INVENTION
The present inventors conducted repeated examinations for achieving the above and other objects, and found that each of a group of compounds containing an alkenyl group and 2,3-difluoro-1,4-phenylene group, represented by formula (1), exhibits a large negative &Dgr;∈, wide liquid crystal phase temperature range, low viscosity, and mutually excellent solubility at low temperature, and that &Dgr;∈/∈⊥, can be decreased and the K
33
/K
11
value can be increased by appropriate selection of the positions of double bonds in the alkenyl group to attain the present invention.
The present invention is described as follows.
According to a first aspect of the present invention, there is provided a liquid crystalline compound represented by the following general formula (1):
where, R
1
represents hydrogen, fluorine, an alkyl group having 1 to 15 carbon atoms, or an alkenyl group having 2 to 15 carbon atoms; each of rings A
1
, A
2
and A
3
independently represents trans-1,4-cyclohexylene group, 1,4-cyclohexenylene group, trans-1,4-silacyclohexylene group, 1,4-phenylene group, 2,3-difluoro-1,4-phenylene group, 2-fluoro-1,4-phenylene group, 3-fluoro-1,4-phenylene group, pyrimidine-2,5-diyl group, pyridine-2,5-diyl group, 1,3-dioxane-2,5-diyl group, tetrahydropyrane-2,5-diyl group, 1,3-dithiane-2,5-diyl group, or tetrahydrothiopyrane-2,5-diyl group; X
1
represents hydrogen or fluorine; Y
1
represents hydrogen or an alkyl group having 1 to 15 carbon atoms, in which each of optional nonadjacent methylene groups (—CH
2
—) may be substituted by oxygen; 1 represents an integer from 1 to 10; in which each of optional nonadjacent methylene groups in (—CH
2
—)
1
may be substituted by oxygen; and each of m and n independently represents 0 or 1.
According to a second aspect of the present invention, there is provided a liquid crystalline compound according to the first aspect, wherein the ring Al in the general formula (1) is trans-1,4-cyclohexylene group and m and n are both 0.
According to a third aspect of the present invention, there is provided a liquid crystalline compound according to the first aspect, wherein each of the rings A
1
and A
2
in general formula (1) is independently trans-1,4-cyclohexylene group, 2,3-difluoro-1,4-phenylene group or 1,3-dioxane-2,5-diyl group; m is 1; and n is 0.
According to a fourth aspect of the present invention, there is provided a liquid crystalline compound according to the first aspect, wherein each of the rings A
1
, A
2
and A
3
in general formula (1) is independently trans-1,4-cyclohexylene group, 2,3-difluoro-1,4-phenylene group or 1,3-dioxane-2,5-diyl group; and m and n are both 1.
According to a fifth aspect of the present invention, there is provided a liquid crystal composition comprising at least two components, characterized by containing at least one liquid crystalline compound represented by general formula (1).
According to a sixth aspect of the present invention, there is provided a liquid crystal composition comprising at least one liquid crystalline compound according to any of the first through fourth aspects as a first component and at least one compound selected from a group consisting of compounds represented by general formulas (2), (3) and (4) as a second component,
where R
2
represents an alkyl group having 1 to 10 carbon atoms, in which each of optional nonadjacent methylene groups may be substituted by oxygen or —CH═CH— group, and in which each of optional hydrogen in these methylene groups may be substituted by fluorine; Y
2
represents fluorine, chlorine, —OCF
3
, —OCF
2
H, —CF
3
, —CF
2
H, —CFH
2
, —OCF
2
CF
2
H or —OCF
2
CFHCF
3
; each of L
1
and L
2
independently represents hydrogen or fluorine; each of Z
1
and Z
2
independently represents 1,2-ethylene group, vinylene group, 1,4-butylene group, —COO—, —CF
2
O—, —OCF
2
— or a single bond; ring B represents trans-1,4-cyclohexylene group, 1,3-dioxane-2,5-diyl group or 1,4-phenylene group, in which each of hydrogen may be substituted by fluorine; and ring C represents trans-1,4-cyclohexylene group or 1,4-phenylene group, i
Bernhardt Henry
Kato Takashi
Kondo Tomoyuki
Kubo Yasuhiro
Matsui Shuichi
Chisso Corporation
McDermott & Will & Emery
Wu Shean C.
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