Fluorine-containing benzothiazoles, and their use in...

Details Fluorine-containing benzothiazoles, and their use in... Fluorine-containing benzothiazoles, and their use in...

2000-03-22

2002-08-20

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299610, C252S299620, C252S299630

Reexamination Certificate

active

06436489

ABSTRACT:

Besides nematic and cholesteric liquid crystals, optically active, tilted, smectic (ferroelectric) liquid crystals have also recently been used in commercial display devices.
Clark and Lagerwall have been able to show that the use of ferroelectric liquid crystals (FLCs) in very thin cells results in opto-electrical switching or display elements which have response times which are faster by a factor of up to 1000 compared with conventional TN (“twisted nematic”) cells (see, for example, EP-A 0 032 362). Owing to this and other favorable properties, for example the possibility of bistable switching and the fact that the contrast is virtually independent of the viewing angle, FLCs are basically highly suitable for areas of application such as computer displays.
For a more in-depth explanation of the technical requirements of FLCs, see European Patent Application 97118671.3 and DE-A 197 48 432.
Benzothiazole derivatives are disclosed in JP-A 09059266 as components of liquid-crystalline mixtures.
Benzothiazoles having one or more F substituents have been described as constituents of complex structures having a pharmacological action, for example in
EP-A-0 714 893,
EP-A-0 795 550, and
EP-A-0 733 365.
These publications do not reveal any suitability of mono- or difluorinated benzothiazoles as components of liquid-crystalline, in particular smectic mixtures and a part of these benzothiazoles.
Since the development, in particular of ferroelectric liquid-crystal mixtures, can in no way be regarded as complete, the manufacturers of displays are interested in a very wide variety of components for mixtures, partly because only the interaction of the liquid-crystalline mixtures with the individual components of the display device or of the cells (for example the alignment layer) allow conclusions to be drawn on the quality of the liquid crystalline mixtures too.
It has now been found that fluorinated benzothiazoles of the formula (I), even when admixed in small amounts, have a favorable effect on the properties of liquid-crystal mixtures, in particular chiral smectic mixtures, for example regarding the dielectric anisotropy and/or the melting point, but also regarding the switching behavior.
The invention relates to the use of compounds of the formula (I) below in liquid-crystal mixtures, preferably smectic and nematic liquid-crystal mixtures, particularly preferably ferroelectric liquid-crystal mixtures. Particular preference is given to use in ferroelectric liquid-crystal mixtures operated in inverse mode or in displays having active matrix elements; very particular preference is given to use in ferroelectric liquid-crystal mixtures operated in inverse mode.
The invention furthermore relates to liquid-crystal mixtures, preferably smectic and nematic liquid-crystal mixtures, particularly preferably ferroelectric liquid-crystal mixtures, which comprise one or more compounds of the formula (I) below
where the symbols and indices have the following meanings:
X
1
and X
2
, independently of one another, are —CH—, —CF—, the —(R
1
)—C— group or the —(R
1
—A
1
—M
1
)C— group
Y
1
and Y
2
, independently of one another, are hydrogen or fluorine, but are not simultaneously fluorine
with the provisos that:
x1) X
2
is the —(R
1
)C— group or the —(R
1
—A
1
—M
1
)C— group, and X
1
is —CF—, Y
1
is F and Y
2
is H, or
x2) X
1
is the —(R
1
)C— group or the —(R
1
—A
1
—M
1
)C— group, and X
2
is —CF—, Y
2
is F and Y
1
is H, or
x3) X
2
is the —(R
1
)C— group or the —(R
1
—A
1
—M
1
)C— group, and X
1
is —CH—, Y
1
is H and Y
2
is F, or
x4) X
1
is the —(R
1
)C— group or the —(R
1
—A
1
—M
1
)C— group, and X
2
is —CH—, Y
2
is H and Y
1
is F,
x5) X
2
is the —(R
1
)C— group or the —(R
1
—A
1
—M
1
)C— group, and X
1
is —CH—, Y
1
is F and Y
2
is H
R
1
and R
2
, independently of one another, are a straight-chain or branched alkyl radical (with or without asymmetrical carbon atoms) having 1 to 20 carbon atoms, where
a) one or two non-terminal —CH
2
— groups may be replaced by —O— and/or —C(═O)— and/or —Si(CH
3
)
2
—, with the proviso that two adjacent —CH
2
— groups cannot be replaced by heteroatoms, and/or
b) one or more —CH
2
— groups may be replaced by —CH═CH— and/or —C≡C—, and/or
c) one —CH
2
— group may be replaced by cyclopropane-1,2-diyl, cyclobutane-1,3-diyl, cyclopentane-1,3-diyl, bicyclo-[1.1.1]pentane-1,3-diyl or cyclohexane-1,4-diyl, and/or
d) one or more H atoms may be replaced by F, and/or
e) in the case of a branched alkyl radical containing asymmetrical carbon atoms, the asymmetrical carbon atoms either have —CH
3
, —OCH
3
, —CF
3
, F, CN and/or Cl as substituents, or are incorporated into a 3— to 7-membered ring, in which, in addition, one or two non-adjacent —CH
2
— groups may be replaced by —O— and one —CH
2
— group may be replaced by —OC(═O)—
A
1
and A
2
, independently of one another, are phenylene-1,4-diyl, unsubstituted, monosubstituted or disubstituted by CN or F, phenylene-1,3-diyl, unsubstituted, monosubstituted or disubstituted by CN or F, cyclohexane-1,4-diyl, in which one or two H atoms may be replaced by CN and/or CH
3
and/or F, 1-cyclohexene-1,4-diyl, in which one H atom may be replaced by F, 1-alkyl-1-silacyclohexane-1,4-diyl, pyridine-2,5-diyl, unsubstituted or monosubstituted by F, pyrimidine-2,5-diyl, unsubstituted or monosubstituted by F, 1,1′-biphenyl-4,4′-diyl, unsubstituted, monosubstituted or disubstituted by F, or 1,1′-phenylcyclohexyl-4,4′-diyl, in which the phenyl moiety is unsubstituted, monosubstituted or disubstituted by F
M
1
is undirected and is —OC(═O)—, —OC(═O)O—, —OCH
2
—, —(CH
2
)
n
—, —OC(═O)CH
2
CH
2
—, —OCH
2
CH
2
CH
2
—, —C≡C— or a single bond
n is from 1 to 6.
Undirected is intended to mean that, in the case of asymmetrical groups, mirror and mirror image of the group can be employed.
According to one embodiment, the proviso x
5
) does not apply.
The symbols and indices in the formula (I) preferably have the following meanings:
R
1
and R
2
, independently of one another, are preferably a straight-chain or branched alkyl radical (with or without asymmetrical carbon atoms) having 2 to 18 carbon atoms, where
a) one —CH
2
— group may be replaced by —O—, and/or
b) one or more H atoms may be replaced by F.
R
1
and R
2
, independently of one another, are particularly preferably a straight-chain or branched alkyl radical (with or without asymmetrical carbon atoms) having 3 to 16 carbon atoms, where
c) one —CH
2
— group may be replaced by —O—.
A
1
and A
2
, independently of one another, are preferably phenylene-1,4-diyl, phenylene-1,3-diyl, 1,1′-biphenyl-4,4′-diyl or 1,1′-phenylcyclohexyl-4,4′-diyl.
A
1
and A
2
, independently of one another, are particularly preferably phenylene-1,4-diyl.
n may have the value 2, 4, 5 or 6.
The following compounds of the formulae (I-1) to (I-5) are particularly preferably employed:
where R
1
and R
2
have the above-mentioned meanings and preferences.
According to one embodiment of the invention, the formula (I-5) is not one of the preferred compounds.
The invention also relates to the fluorinated benzothiazoles of the formula (1) with the exception of the proviso x4) or the formula (I-4).
The compounds according to the invention and employed according to the invention are prepared by methods known per se from the literature, as described in standard works on organic synthesis, for example Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart.
However, it may prove necessary to vary or modify the literature methods for the requirements of mesogenic units, since, for example, functional derivatives having long (>C6) alkyl chains frequently have lower reactivity than, for example, the methyl and ethyl analogs.
Particular reference is made in this connection to the following references, which describe in general terms the synthesis of benzothiazole derivatives, but which do not reveal to the person skilled in the art the fluorinated benzothiazoles

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