Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified...
Reexamination Certificate
1999-01-21
2002-10-22
Wu, Shean C. (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
C252S299630, C252S299670, C560S065000, C570S127000, C570S129000, C570S130000
Reexamination Certificate
active
06468606
ABSTRACT:
TECHNICAL FIELD
This invention relates to a novel liquid crystalline compound which can demonstrate favorable properties principally in a twisted nematic liquid crystal composition and a liquid crystal composition having favorable properties using said novel liquid crystalline compound.
BACKGROUND ART
A liquid crystal display element utilizes an optical anisotropy and a dielectric anisotropy which a liquid crystalline material possesses. As a display mode therefor, there are known a twisted nematic mode (TN), a super twisted nematic mode (STN), a dynamic scattering mode (DS), a guest-host mode (G-H), DAP mode and others. As a driving mode therefor, there are known a static-driving mode, a time-sharing driving mode, an active-matrix driving mode, a dual frequency driving mode and others. The properties of liquid crystalline materials used for these various liquid crystal display elements vary depending on the application of the elements, but liquid crystalline materials are required to be stable to external environmental factors such as moisture, air, heat, light, etc. and to show a liquid crystal phase over a wide temperature range around room temperature, with a lower viscosity and a lower driving voltage. In addition, a liquid crystalline material generally used for a liquid crystal display element is composed of several to twenty liquid crystalline compounds for providing the optimum dielectric anisotropy (&Dgr;∈) or optical anisotropy (&Dgr;n) which is required for individual display elements. In view of this, there has been required a compatibility with other liquid crystalline compounds, particularly in recent years, a good low-temperature compatibility from the demand for application under various environments.
A liquid crystalline compound having as a substituent a fluorine atom at the end generally shows a lower dielectric anisotropy (&Dgr;∈) and optical anisotropy (&Dgr;n) as compared with a compound having a cyano group as a substituent, but has a remarkably superior chemical stability to that of the cyano-substituted compound and is considered to cause a less production of ionic impurities due to a change with time. Therefore, the fluorine-containing compounds have been actively used for various modes including an active-matrix mode. The recent trend of development in this field is directed to making a small-sized liquid crystal element including a portable TV and lowering in driving voltage in compliance with the demand for a lower voltage. In order to achieve this object, the development of a compound having a high dielectric anisotropy (&Dgr;∈) is active.
In order to increase a dielectric anisotropy (&Dgr;∈) in the fluorine-containing compound, it is effective to increase the substitution number of a fluorine atom, which is a procedure usually carried out by those skilled in the art. However, it has been empirically realized by those skilled in the art that there is a proportional relationship between the substitution number of a fluorine atom and the viscosity of the compound, and further that there is an inverse relationship between the. substitution number of a fluorine atom and the temperature range of a liquid crystal phase. Accordingly, it has been considered to be difficult to improve a dielectric anisotropy (&Dgr;∈) only, while inhibiting an increase in the viscosity and a reduction in the temperature range of a liquid crystal phase. As an example of the compounds multi-substituted with fluorine atoms, those having the following structure are disclosed.
The dielectric anisotropy values (&Dgr;∈) of the compounds (a), (b) and (c) are high in the order of (c)>(b)>(a). However, the compound (c) is not appreciably good in respect of a compatibility with other liquid crystalline compounds, especially, a low temperature compatibility. On the other hand, the compound (d) shows an example wherein a fluorine atom is laterally substituted on the phenyl ring to which R is attached, but this compound is not so appreciably good in respect of compatibility.
DISCLOSURE OF INVENTION
It is an object of this invention to provide a novel liquid crystalline compound having a relatively low viscosity, a high dielectric anisotropy, a low optical anisotropy and an excellent compatibility with other known liquid crystalline compounds, in particular, an excellent low temperature compatibility, and a liquid crystal composition containing the same.
We have investigated various compounds in an effort to solve the aforesaid problems and found as a liquid crystalline compound with a high dielectric anisotropy, a compound having a phenylbenzoate moiety and a fluorine atom substituted at the ortho-position to the ester carbonyl group. As a result of further study of its physical properties, it has been found that the fluorine atom substituted at the ortho-position to the ester carbonyl group of the phenylbenzoate moiety can serve to improve the viscosity and suppress a reduction in a temperature range of a liquid crystal phase and to exhibit an extremely higher dielectric anisotropy than that as we initially expected and further to accomplish a remarkable effect on improvement in a compatibility with other liquid crystalline compounds, in particular, in a low temperature compatibility, which leads to the completion of the present invention directed to a novel liquid crystalline material.
In the first aspect, the invention relates to phenylbenzoate derivatives represented by formula (1)
wherein R
1
is a hydrogen atom or a straight or branched-chain alkyl group of 1-10 carbons, one or two non-adjacent CH
2
groups of which can be replaced by an oxygen atom or a group of —CH═CH—; X is a hydrogen atom or a halogen atom; A and B each independently represent a 1,4-phenylene group or a trans-1,4-cyclohexylene group, which may be substituted by one or more halogen atoms; Z
1
and Z
2
each independently represent —CH
2
CH
2
—, —CO—O—, —O—CO—, —CH═CH—, —C≡C—, —(CH
2
)
4
— or a covalent bond; m and n each independently represent 0 or 1.
Where R
1
in formula (1) is a group other than a hydrogen atom, the following groups are included as specific groups.
Where R
1
is a straight-chain group, it includes an alkyl group of 1-10 carbons, an alkoxy group of 1-9 carbons, an alkoxyalkyl group of 2-9 carbons, an alkoxyalkoxy group of 2-8 carbons, an alkenyl group of 2-11 carbons, an alkenyloxy group of 2-10 carbons, an alkenyloxyalkyl group of 3-10 carbons and an alkoxyalkenyl group of 3-10 carbons.
Where R
1
is a branched-chain group, it includes an alkyl group of 3-10 carbons, an alkoxy group of 3-9 carbons, an alkoxyalkyl group of 4-9 carbons, an alkoxyalkoxy group of 4-8 carbons, an alkenyl group of 3-11 carbons, an alkenyloxy group of 3-10 carbons, an alkenyloxyalkyl group of 4-10 carbons and an alkoxyalkenyl group of 4-10 carbons.
Where R
1
is a branched-chain group, in particular, an optically active group, the corresponding compound can be used as an additive to induce a twisted structure in a nematic liquid phase or as a component for a chiral smectic liquid crystal having a ferroelectricity.
One preferred embodiment in the first aspect of this invention is a phenylbenzoate derivative of formula (1) wherein m=n=0, both Z
1
and Z
2
are a covalent bond.
Another preferred embodiment in the first aspect of this invention is a phenylbenzoate derivative of formula (1) wherein m=1, n=0, either of Z
1
and Z
2
is a covalent bond, A is a trans-1,4-cyclohexylene group.
A still another preferred embodiment in the first aspect of this invention is a phenylbenzoate derivative of formula (1) wherein m=1, n=0, either of Z
1
and Z
2
is a covalent bond, A is a 1,4-phenylene group.
A still another preferred embodiment in the first aspect of this invention is a phenylbenzoate derivative of formula (1) wherein m=1, n=1, and A and B each are a trans-1,4-cyclohexylene group.
A still another preferred embodiment in the first aspect of this invention is a phenylbenzoate derivative of formula (1) wherei
Goto Yasuyuki
Kondo Tomoyuki
Matsui Shuichi
Miyazawa Kazutoshi
Nakagawa Etsuo
Chisso Corporation
Wu Shean C.
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