Fluoro-substituted alkenyl compounds, liquid crystal...

Details Fluoro-substituted alkenyl compounds, liquid crystal... Fluoro-substituted alkenyl compounds, liquid crystal...

2001-05-22

2003-07-29

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299610, C252S299630, C252S299660, C570S128000, C570S129000, C570S144000

Reexamination Certificate

active

06599590

ABSTRACT:

TECHNICAL FIELD
This invention relates to liquid crystalline compounds and liquid crystal compositions, and more particularly, to liquid crystalline fluoro-substituted alkenyl compounds as a suitable component for the liquid crystal compositions especially for TN mode, STN mode, TFT mode, and OCB mode, liquid crystal compositions comprising such compounds, and liquid crystal display elements comprising such liquid crystal compositions.
The expression “liquid crystalline compound” is used herein as the general term for a compound possessing a liquid crystal phase and a compound exhibiting no liquid crystal phase and yet serving as a useful constitutional component for a liquid crystal composition.
RELATED ART
The liquid crystal display element utilizes the optical anisotropy and the dielectric anisotropy possessed by a liquid crystal substance. It is sorted into various types according to the display mode such as twisted nematic (TN) mode, dynamic scattering (DS) mode, guest-host (G-H) mode, deforming of aligned phases (DAP) mode, supertwisted nematic (STN) mode, voltage control birefringence (VCB, ECB, or TB) mode, vertical aligning (VA) mode, multidomain vertical aligning (MVA) mode and OCB mode, utilizing liquid crystal substances with different properties suitable for each mode. The liquid crystal substances which are used for these display modes are required to be stable to moisture, air, heat, and light.
A liquid crystal display element requiring a lower driving voltage and yet manifesting a high contrast has been demanded in these years. For the purpose of lowering the driving voltage, it is important to increase dielectric anisotropy value (&Dgr;∈) of a given liquid crystal material. Particularly, for the purpose of heightening the contrast of the liquid crystal display element of the STN mode, the curve of voltage transmittance of a given liquid crystal display element needs to be very steep. For this, a large elastic constant ratio (K
33
/K
11
) of the liquid crystal material is required.
EP 0330216 A discloses the below (1-a) and WO91/06522 discloses the below (1-b), as a liquid crystal material exhibiting a positive dielectric anisotropy value.
These compounds, however, have small &Dgr;∈ and small K
33
/K
11
ratio and thus are not sufficient for solving the problems mentioned above. Though WO91/06522 claims the compounds containing a cyano group, the description discloses neither the structure nor the data of such compounds.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid crystalline compound which has a broad temperature range for liquid crystal phases applicable to various modes of liquid crystal display elements, can show any optical anisotropy value (&Dgr;n) depending on combination of factors such as a ring structure and a substituent, and is stable against the influence of moisture, air, heat, and light.
More specifically, the invention aims at providing a liquid crystalline compound which eliminates the conventional technical defects mentioned above thereby possessing a large &Dgr;∈ and a large K
33
/K
11
ratio.
Another object of the invention is to provide a liquid crystal composition comprising the above compound, which can impart the merits of a low driving voltage and a high contrast to a liquid crystal display element.
Further object of the invention is to provide a liquid crystal display element comprising the liquid crystal composition.
The present inventors, as a result of diligent study, have found that the following liquid crystalline compounds possess a large &Dgr;∈ and a large K
33
/K
11
ratio.
More specifically, (a) the compounds of the following formula (1) wherein the ring A
3
is not a cyclohexane ring; (b) the compounds represented by the formula (1) which contain a monofluoroalkenyl group or a difluoroalkenyl group when the ring A
3
is a cyclohexane ring and Z
3
is not a single bond and which further contain a cyano group; and (c) the compounds represented by the formula (1) which contain a monofluoroalkenyl group or a difluoroalkenyl group when the ring A
3
is a cyclohexane ring and Z
3
is a single bond and which contain, in addition to a cyano group, a benzene ring having at least one hydrogen atom substituted by F.
The present inventors have further found that the liquid crystal compositions comprising such compounds are the materials best suitable for achieving a low driving voltage and the manifestation of a high contrast in various liquid crystal display elements, and finally completed the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a fluoro-substituted alkenyl compound represented by the formula (1):
wherein Y
1
, Y
2
, Y
3
and Y
4
are each independently H or F, provided that at least one of Y
1
and Y
2
is F; Q
1
is a single bond or an alkylene group of 1-20 carbon atoms, at least one —CH
2
— being optionally substituted by —O—, provided that two or more —O— are not adjacent to each other; Q
2
is a single bond or —C≡C—; Rings A
1
, A
2
and A
3
are each independently a cyclohexane ring, a dioxane ring, a cyclohexene ring, a pyrimidine ring, a pyridine ring, or a benzene ring, or a benzene ring having at least one hydrogen atom substituted by F; Z
1
, Z
2
and Z
3
are each independently a single bond, —CH
2
CH
2
—, —CH
2
O—, —OCH
2
—, —COO—, —OCO—, —CH═CH—, —C≡C—, —CF
2
O—, or —OCF
2
; and m and n are each independently 0 or 1; provided that Y
3
is F when Ring A
3
is a cyclohexane ring and Z
3
is a single bond.
This invention further provides a fluoro-substituted alkenyl compound represented by the formula (1) wherein m and n are both 0.
This invention further provides a fluoro-substituted alkenyl compound represented by the formula (1) wherein Ring A
3
is a dioxane ring, a cyclohexene ring, a pyrimidine ring, a pyridine ring, or a benzene ring, or a benzene ring having at least one hydrogen atom substituted by F.
In one embodiment of the invention, there is provided a fluoro-substituted alkenyl compound represented by the formula (1) wherein Ring A
3
is a cyclohexane ring.
In another embodiment of the invention, there is provided a fluoro-substituted alkenyl compound represented by the formula (1) wherein Z
3
is —COO—.
In another embodiment of the invention, there is provided a fluoro-substituted alkenyl compound represented by the formula (1) wherein both Y
1
and Y
2
are F.
This invention also provides a liquid crystal composition comprising a fluoro-substituted alkenyl compound represented by the formula (1).
This invention further provides a liquid crystal composition comprising as a first component a fluoro-substituted alkenyl compound represented by the formula (1) and as a second component a compound selected from the group consisting of the compounds represented by the formulas (2), (3) and (4)
wherein R
1
is an alkyl group of 1-10 carbon atoms, at least one —CH
2
— being optionally substituted by —O— or —CH═CH—, provided that two or more of —O— are not adjacent to each other, and at least one H atom being optionally substituted by F; X
1
is F, Cl, OCF
3
, —OCF
2
H, —CF
3
, —CF
2
H, —CFH
2
, —OCF
2
CF
2
H, or —OCF
2
CFHCF
3
; L
1
and L
2
are each independently H or F; Z
4
and Z
5
are each independently —(CH
2
)
2
, —(CH
2
)
4
—, —COO—, —CF
2
O—, —OCF
2
—, —CH═CH—, or a single bond; Rings A and B are each independently a cyclohexane ring, a dioxane ring, or a benzene ring, or a benzene ring having at least one hydrogen atom substituted by F; and Ring C is a cyclohexane ring, a benzene ring, or a benzene ring having at least one hydrogen atom substituted by F.
The invention further provides a liquid crystal composition comprising as a first component a fluoro-substituted alkenyl compound represented by the formula (1) and as a second component a compound selected from the group consisting of the compounds represented by the formulas (5) and (6)
wherein R
2
and R
3
are each independently an alkyl group of 1-10 carbon atoms, at least one —CH
2
— being optionally substituted

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