Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Reexamination Certificate
1999-07-28
2001-06-19
Kelly, C. H. (Department: 1756)
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
C252S299630, C570S129000, C570S127000, C570S144000
Reexamination Certificate
active
06248260
ABSTRACT:
This application is a 371 application of International Application No. PCT/JP98/00365 field Jan. 29, 1998.
TECHNICAL FIELD
The present invention relates to liquid crystalline compounds and liquid crystal compositions. More specifically, the invention relates to liquid crystalline compounds having a fluoroalkyl group at both terminals and being preferable as component of liquid crystal compositions, particularly of liquid crystal compositions for TFT, liquid crystal compositions comprising the compound, and liquid crystal display devices fabricated by using the liquid crystal composition.
BACKGROUND ART
Liquid crystal display devices employ optical (refractive) anisotropy and dielectric anisotropy of liquid crystal substances, and are divided into various modes such as TN mode (twisted nematic mode), DS mode (dynamic scattering mode), G.H mode (guest-host mode), DAP (deformation of aligned phase mode), and STN mode (super twisted nematic mode) according to their display modes. Properties of liquid crystal substances suitable for each of the display mode are different. Recently, liquid crystal display devices particularly having a higher display quality are required, and demand for display devices of active matrix mode represented by TFT mode (thin film transistor mode) is increased in order to respond to the requirement. Liquid crystal substances used in display devices of any mode are necessary to be stable against moisture, air, heat, and light. Besides, the liquid crystal substances must exhibit a liquid crystal phase in a temperature range as large as possible with room temperature being its center, be low in viscosity, be excellent in miscibility with other liquid crystalline compounds (hereinafter used as a general term for the compounds having a liquid crystal phase and the compounds which do not impair a liquid crystal phase when mixed with other liquid crystal compounds) and liquid crystal compositions, have a high dielectric anisotropy value
(&Dgr;∈), and have an optimum optical anisotropy value (&Dgr;n). However, liquid crystal substances which completely satisfy such requirements by single compound have not been found, and it is a current situation that liquid crystal compositions obtained by mixing several to several tens kind of liquid crystalline compounds are used.
It is lately required in particular to liquid crystal display devices of TFT mode that they maintain a high contrast during frame time and can favorably be driven even at low temperatures. In order to cope with these requirements, advent of liquid crystalline compounds and liquid crystal compositions exhibiting a higher voltage holding ratio than that of conventional liquid crystal materials is expected for the former, and advent of liquid crystalline compounds which more hardly deposit crystals or develop smectic phase at low temperatures, that is, liquid crystalline compounds excellent in the miscibility with other liquid crystalline compounds and liquid crystal compositions at low temperatures is hoped for the latter.
Heretofore, as liquid crystal materials having a high voltage holding ratio and a high &Dgr;∈, fluorine type compounds, for example, trifluorophenyl derivatives expressed by the formula (10) (Laid-open Japanese Patent Publication No. Hei 02-233626), and trifluoromethylphenyl derivatives expressed by the formula (11) and trifluoromethoxyphenyl derivatives expressed by the formula (12) (Laid-open Japanese Patent Publication No. Hei 04-506361) are known.
Whereas these compounds have an electron withdrawing group at one terminal, the alkyl chain length (total of the number of carbon atoms and the number of oxygen atom in the chain) in the group is 2 or less. Accordingly, these compounds readily deposit crystals or develop smectic phase at low temperatures when mixed with other liquid crystal substances.
On the other hand, as component of liquid crystal compositions which makes excellent driving of liquid crystal display devices of TFT mode possible even at low temperatures, compounds a part of which is replaced by a fluorine substituted alkoxy group expressed by the formula (13) in which the number of carbon atom in the electron withdrawing group at one terminal is 2 (Laid-open Japanese Patent Publication No. Hei 7-145099) and compounds expressed by one of the formulas (14) to (18) in which the number of carbon atom described above is 2 or more (WO 88/08441, DE 4142519, DE 4329592, DE 4308028, and DE 19513007 in turn) are also known.
These compounds having an electron withdrawing group at one terminal are still insufficient as component of liquid crystal compositions for driving at low temperatures, and for instance, are liable to cause an extreme lowering in response speed and poor display at low temperatures.
Further, compounds which are formed into a structure having an electron withdrawing group at both terminals by providing F, or an alkyl group or alkoxy group in which fluorine atom is introduced, for example, CF
3
or OCF
3
at the other terminal are known (Laid-open Japanese Patent Publication No. Hei 04-506817).
However, such compounds are not sufficient in the miscibility with other liquid crystals at low temperatures, and the compound expressed by the following formula (19) does not exhibit even a liquid crystal phase.
As described above, compounds excellent in the miscibility at low temperatures with other liquid crystals at low temperatures while having a high voltage holding ration and a high &Dgr;∈ have not been attained.
DISCLOSURE OF THE INVENTION
An object of the present invention is to eliminate the defects in the prior art described above. Another object of the present invention is to provide liquid crystalline compounds which are excellent in the miscibility with existing liquid crystalline compounds even at low temperatures, and electrically and chemically stable while having a high voltage holding ratio and a high &Dgr;∈, to provide liquid crystal compositions comprising the compound, and to provide liquid crystal display devices fabricated by using the composition.
As a result of diligent investigations by the present inventors, it has been found out that the compounds which are composed of a skeleton of two rings or three rings each of which rings is not linked through a bonding group, have a structure in which an electron withdrawing group is bonded at both terminals, the electron withdrawing group at one side is an alkyl chain having one fluorine atom at terminal and the group at the other side is one selected from fluoroalkyl chains and fluoroalkoxy chains are effective, 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 n0 is an integer of 2 to 10; n1 and n2 are each independently 0 or 1; ring A1 and ring A2 each independently represent a group selected from the groups expressed by one of the formulas (a) to (i);
Q
1
and Q
2
each independently represent hydrogen atom, fluorine atom, or chlorine atom; Y represents a fluoroalkyl group having 2 to 7 carbon atoms; and each atom which constitutes the compound may be its isotope.
(2) The liquid crystalline compound recited in paragraph (1) above wherein n1 is 0.
(3) The liquid crystalline compound recited in paragraph (1) above wherein n1 is 1.
(4) The liquid crystalline compound recited in paragraph (1) above wherein n2 is 0.
(5) The liquid crystalline compound recited in paragraph (1) above wherein n2 is 1.
(6) The liquid crystalline compound recited in paragraph (1) above wherein n1 is 1 and ring A1 is a group selected from the groups expressed by any one of the formulas (a) to (d).
(7) A liquid crystal composition comprising at least one liquid crystalline compound recited in any one of paragraphs (1) to (6) above.
(8) A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in any one of paragraphs (1) to (6) above, and comprising, as a second component, at least one compound selected
Haseba Yasuhiro
Kubo Yasuhiro
Matsui Shuichi
Miyazawa Kazutoshi
Nakagawa Etsuo
Chisso Corporation
Kelly C. H.
Wenderoth , Lind & Ponack, L.L.P.
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