Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified...
Reexamination Certificate
2001-12-28
2004-06-08
Wu, Shean C. (Department: 1756)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
C252S299620, C560S005000, C560S006000, C560S119000, C570S129000, C570S183000, C570S187000
Reexamination Certificate
active
06746728
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel liquid crystal compound comprising a tetrahydronaphthalene derivative which is useful as an electrooptical liquid crystal display material, as well as a liquid crystal composition containing such a compound and a liquid crystal display element utilizing the compound.
BACKGROUND ART
Liquid crystal display elements are now used not only in clocks and calculators, but also in various types of measuring instruments, automobile instrument panels, word processors, personal digital assistants, printers, computers and televisions. Typical examples of liquid crystal display methods include TN (twisted nematic) types, STN (super twisted nematic) types, DS (dynamic scattering) types, GH (guest host) types, or methods which enable high speed response such as FLC (ferroelectric liquid crystal) types or AFLC (antiferroelectric liquid crystal) types. In addition, multiplex driving is replacing the conventional static driving as the most common type of driving method, and moreover, simple matrix systems, and more recently, active matrix systems, have also come into practical use.
Extremely large numbers of different liquid crystal compounds have been synthesized for use as liquid crystal materials, and these are selected and used depending on the display method, the driving method and the final use of the display. However the demand for improved performance (such as improved display quality or increased display screen size) from liquid crystal display elements has grown stronger over the years, and development of new liquid crystal compounds to satisfy these demands is ongoing.
Liquid crystal compounds generally comprise a central skeleton part known as the core, with terminal portions on both sides. Typically, the most common ring structure that composes the core portion of the liquid crystal compound is a 1,4-phenylene group (which may be substituted with one or two halogen atoms, cyano groups, or methyl groups or the like) and a trans-1,4-cyclohexylene group. However, liquid crystal compounds composed solely of a 1,4-phenylene group and a trans-1,4-cyclohexylene group are limited in terms of the variety of possible compounds and the associated characteristics, and are currently unable to adequately accommodate the aforementioned demands.
Ring structures which have been investigated other than the 1,4-phenylene group and trans-1,4-cyclohexylene group described above include heterocyclic ring systems such as a pyridine-2,5-diyl group, pyrimidine-2,5-diyl group, and a 1,3-dioxane-trans-2,5-diyl group, and fused ring systems such as a trans-decahydronaphthalene-2,6-diyl group, naphthalene-2,6-diyl group, tetrahydronaphthalene-2,6-diyl group, bicyclo[2.2.2]octane-1,4-diyl group, and a spiro[3.3]heptane-2,6-diyl group, although production problems (including technical problems and cost) and stability problems mean that only a very small number are currently used in practical applications.
Of these fused ring systems, the tetrahydronaphthalene-2,6-diyl group is a ring structure that has been known for considerable time, although synthetic examples are extremely few, and furthermore, characteristics of the ring structure other than the liquid crystallinity (the phase transition temperature), in particular the characteristics of the structure as a nematic liquid crystal, are virtually unknown. (Recently, it was reported that an optically active alcohol ester of tetrahydronaphthalene-2-carboxylic acid showed smectic liquid crystal characteristics, and in particular highly interesting characteristics as a ferroelectric liquid crystal and an antiferroelectric liquid crystal. Furthermore, a ferroelectric liquid crystal skeleton comprising a fluorine containing tetrahydronaphthalene structure has also been recently reported.)
In a typical liquid crystal compound, at least one of the terminal portions is a chain like (side chain) group, and in cases in which the dielectric anisotropy is positive, so-called p-type liquid crystals, then the other terminal portion is usually a polar group.
In TN or STN display methods, in order to reduce the associated driving voltage, a w compound with a large positive dielectric anisotropy (p-type) is required. In order to satisfy this requirement, typically compounds with a cyano group at the molecule terminal, and moreover at least one fluorine atom in the same direction on the molecule are used. The reported tetrahydronaphthalene derivatives almost all have a dielectric anisotropy between 0 and a negative value, so-called n-type liquid crystals, and the only examples of p-type liquid crystals where a polar group has been introduced onto a tetrahydronaphthalene skeleton are limited to compounds with a phenyltetrahydronaphthalene skeleton or a phenyl tetrahydronaphthalene-2-carboxylate skeleton, and no comments have been made about the electrooptical characteristics, nor examples given of potential applications (Helv. Chim. Acta, 65, 1318-1330 (1992)).
Examples of p-type compounds for use with the aforementioned active matrix driving method include only compounds with a fluorine atom, a fluoroalkoxy group or a fluoroalkyl group as the polar group, and no reports have been made of a tetrahydronaphthalene compound. Furthermore, although many liquid crystal compounds which are tetrahydronaphthalene derivatives are not particularly co-soluble with other liquid crystal compounds, it is thought that introducing a side substituent (a fluorine atom is particularly desirable) into the tetrahydronaphthalene skeleton would be effective in alleviating this problem. In terms of application to the aforementioned active matrix system, it is thought that substitution with a fluorine group would also be effective in the case in which a polar group is introduced directly into the tetrahydronaphthalene ring. There are no actual synthetic examples of this type of fluorotetrahydronaphthalene derivative, and at present it is impossible to even estimate the properties of this type of compound.
In liquid crystal compounds, it is known that replacing the alkyl group typically used as the side chain portion with an alkenyl group, results in superior effects such as an improvement in liquid crystallinity, a reduction in viscosity, and improvements in the sharpness of the display characteristics. However, these alkenyl groups are usually introduced via direct bonding to a cyclohexane ring, and no compounds have been reported where such an introduction has occurred on an aromatic ring, or more particularly a tetrahydronaphthalene ring.
Similarly, tetrahydronaphthalene derivatives with a side chain such as an alkoxylalkyl group, a fluoroalkyl group, a fluoroalkenyl group, or a fluoroalkenyloxy group or the like, have also not been reported.
In terms of the ring structure linkage group within the core of a liquid crystal compound, in addition to single bonds and ester groups (—COO—, —OCO—), many bivalent organic groups such as a 1,2-ethylene group (—CH
2
CH
2
—), an ethynylene group (—C≡C—) or a difluoroethenylene group (—CF═CF—) are also known, although such groups are unknown within tetrahydronaphthalene derivatives.
DISCLOSURE OF INVENTION
The problem which the present invention attempts to resolve is to provide a novel compound with a tetrahydronaphthalene skeleton, and furthermore to provide a practical liquid crystal composition using such a compound.
As a result of intensive investigations aimed at resolving the above problem, the present inventors discovered compounds with a tetrahydronaphthalene skeleton which could be produced with ease, which in the main showed liquid crystallinity over a wide temperature range, and which regardless of the liquid crystallinity or otherwise of any single compound, upon addition to a composition, could be mixed with the composition without any lowering in the response speed (in a large number of cases the response speed improves), without any marked narrowing of the targeted liquid crystal temperature range (in a large number of cases the temperature range widens), and wi
Frings Rainer Bruno
Grahe Gerwald
Kusumoto Tetsuo
Nagashima Yutaka
Negishi Makoto
Armstrong Kratz Quintos Hanson & Brooks, LLP
Dainippon Ink and Chemicals Inc.
Wu Shean C.
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