Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified...
Reexamination Certificate
2001-04-25
2003-09-23
Wu, Shean C. (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
C570S128000, C252S299010, C252S299630
Reexamination Certificate
active
06623810
ABSTRACT:
FIELD OF ART
The present invention relates to novel phenylacetylene compounds having at least one alkoxy group bound to its skeleton and novel phenylacetylene compounds having a cyclopropane or alkenyl group bound to its skeleton, which compounds are useful as a material for fabricating liquid crystal display devices or as a constituent of liquid crystal compositions. The present invention also relates to liquid crystal compositions having a large refractive index anisotropy (&Dgr;n), and liquid crystal elements produced with such compositions such as optical shutters or display devices including STN (supertwisted nematic) liquid crystal elements, or polymer dispersed liquid crystal (PDLC) elements.
BACKGROUND ART
Improvement in performance of liquid crystal display elements has become essential with the recent development in information-oriented society. For higher processing speed and performance, liquid crystal compositions need to contain a material having a large refractive index anisotropy.
A tolan compound is known as liquid crystal having a relatively large refractive index anisotropy (Mol. Cryst. Liq. Cryst., Vol.23, p233 (1973)). However, the refractive index anisotropy of this compound is about 0.2, which is not yet large enough.
There is also developed a compound represented by the formula:
wherein “Alkyl” stands for an alkyl group (JP-A-2-83340). Though this compound has a refractive index anisotropy of 0.3 or larger, it has poor compatibility with other liquid crystals, and is thus not practical.
There is further developed, aiming at improvement in the compatibility with other liquid crystals, a compound represented by the formula:
wherein R stands for an alkyl group, Y stands for R, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, or a cyano group; H
1
to H
12
each stands for a hydrogen, fluorine, or chlorine atom, and at least one of H
1
to H
12
is a fluorine or chlorine atom (JP-A-9-216841). This compound is improved in compatibility with other liquid crystals, but is not yet sufficient in refractive index anisotropy.
On the other hand, with the recent development in information-oriented society, display devices has been assuming importance as one type of man-machine interfaces. Among the display devices, flat displays, in particular liquid crystal displays (LCDs) have been rapidly spreading for their thinness, light weight, low driving voltage, and low power consumption. Among liquid crystal elements including such liquid crystal displays, matrix type liquid crystal elements that can provide a large amount of information employ two types of addressing systems, active and simple matrices.
In the active matrix elements, each pixel is provided with a thin film transistor made of polysilicon or amorphous silicon or a diode, as a nonlinear element. However, simple matrix elements currently prevails for its costs and productivity, since active matrix elements have problems in increasing areal size, reducing of costs, and increasing density, due to its complex manufacture process and low process yield.
Simple matrix liquid crystal elements currently in practical use are mainly TN (twisted nematic) or STN liquid crystal elements. TN elements are widely used as display devices for watches and calculators. In this system, the electro-optical property curve is not steep, and the contrast remarkably decreases as the duty increases, which properties cause difficulties in creating large displays. STN elements, which have been developed for overcoming such disadvantages of the TN elements, can be used for fabricating large displays owing to its steep electro-optical property curve, and are now used for manufacturing displays of laptop personal computers.
Though STN elements have superior properties compared to TN elements, these elements yet have problems to be solved for realizing still larger displays, lower costs, and higher density. For example, STN liquid crystal elements are still insufficient in viewing angle and response speed compared to TFT liquid crystal elements, which are typically used in active matrix displays. High response speed is particularly essential for large displays, higher density, and movie pictures display.
One of the effective means for increasing the response speed of STN liquid crystal elements is to reduce the cell thickness. However, STN elements utilize birefringence effect for displaying, which requires suppression of change in optical properties and color tone of the panel, i.e. requires maintenance of retardation R represented by R=(&Dgr;n×d) at a particular optimum value, so that the reduction in cell thickness d will require increase in refractive index anisotropy &Dgr;n.
Liquid crystal compositions with larger &Dgr;n have, however, larger viscosity in general, and thus are not suitable for achieving high response speed. Liquid crystal compositions having larger &Dgr;n and lower viscosity are demanded.
In addition, response parameter &eegr;/&Dgr;n
2
is known to be well correlated with response speed, and the smaller the value of the response parameter, the shorter the response speed tends to be. Thus, liquid crystal having a smaller response parameter is desired.
However, compounds having larger &Dgr;n are generally poor in compatibility with other liquid crystals, and have difficulty in exhibiting a nematic phase over a wide temperature range in lower temperature region. JP-A-9-216841 discloses, for example, a composition containing a liquid crystal compound that has a large &Dgr;n and improved compatibility with other liquid crystals. Though this compound is said to have stability at lower temperatures, &Dgr;n of the composition per se is not very large.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide a novel phenylacetylene compound that has a large refractive index anisotropy, is easy to mix with other liquid crystals, and has advantageous stability against light.
It is another object of the present invention to provide a liquid crystal composition having a large refractive index anisotropy (&Dgr;n), and a liquid crystal element produced with such a liquid crystal composition that may be used for manufacturing optical shutters and display devices.
It is yet another object of the present invention to provide a liquid crystal composition that has a large refractive index anisotropy and exhibits a nematic phase over a wide temperature range including room temperature, a liquid crystal composition that has a small response parameter (&eegr;/&Dgr;n
2
) and provides excellent response time, and a liquid crystal element produced with such a composition.
According to the present invention, there is provided a phenylacetylene compound represented by the formula (1A):
wherein A
1
to A
12
each independently stands for a hydrogen atom, a fluorine atom, an alkoxy group having 1 to 10 carbon atoms, or an alkyl group having 1 to 10 carbon atoms optionally substituted with at least one fluorine atom, with at least one of A
1
to A
12
being an alkoxy group having 1 to 10 carbon atoms; R
1
and R
2
each independently stands for a hydrogen atom, a fluorine atom, a cyano group, —SF
5
, —NCS, a 4-R
3
-(cycloalkyl) group, a 4-R
3
-(cycloalkenyl) group, or a R
4
—(O)q group, wherein R
3
stands for a hydrogen atom or a straight or branched alkyl group having 1 to 12 carbon atoms optionally substituted with at least one fluorine atom, R
4
stands for a straight or branched alkyl group having 1 to 12 carbon atoms optionally substituted with at least one fluorine atom, and q is 0 or 1.
According to the present invention, there is also provided a phenylacetylene compound represented by the formula (2A):
wherein A
1
to A
12
each independently stands for a hydrogen atom, a fluorine atom, or an alkyl or alkoxy group having 1 to 10 carbon atoms optionally substituted with at least one fluorine atom, with at least one of A
1
to A
12
being an alkyl or alkoxy group having 1 to 10 carbon atoms optionally substituted with at least one fluorine atom; B stands for:
R
1
stands for
Fujisawa Koichi
Iwakura Kazunori
Minai Masayoshi
Sekine Chizu
Birch & Stewart Kolasch & Birch, LLP
Sumitomo Chemical Company Limited
Wu Shean C.
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