Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Reexamination Certificate
2001-01-05
2003-05-27
Huff, Mark F. (Department: 1756)
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
C252S299010
Reexamination Certificate
active
06569356
ABSTRACT:
This invention relates to chiral materials and their use as doping, agents for liquid crystals for a wide range of applications including solid state cholesteric filters for projection displays, circular polariser, optical filter. etc.
The addition of a chiral compound to an achiral liquid crystalline phase is one of the procedures currently used for the conversion of achiral into chiral mesophases. The nematic phase, for example, is converted to the cholesteric one when being doped with a small amount of a chiral substance. This conversion manifests itself by the occurrence of an intermolecular helix which is characterised by the-so-called helical twisting power (HTP) given in Equation 1.
HTP
=
[
ⅆ
p
-
1
ⅆ
x
]
X
=
0
≅
p
-
1
x
=
∑
i
x
i
(
HTP
)
i
HTP
(
µm
-
1
)
helical
twisting
power
for
small
concentrations
p
(
µm
)
pitch
of
induced
helix
,
+
for
(
P
)
-
,
-
for
(
M
)
-
helix
x
mole
fraction
of
the
dopant
∑
i
sum
over
all
chiral
conformers
of
the
dopant
x
i
mole
fraction
of
conformer
i
(
1
)
Said HTP is in fact a measure for the efficiency of a given dopant and is determined by the Cano method with solutions of the dopant in the host mesophase. Since the chiral guest and the achiral host compounds are not necessarily compatible at the molecular scale, their binary solution is frequently characterised by undesirable chances of the thermotropic sequence of the initial host liquid crystalline material, like for example a depression of the clearing point. Those changes could in turn have negative effects on the phase properties of the host, such as a decrease of the birefringence etc. Therefore, a chiral dopant is sought so that with very small concentrations of this latter, large values of HTP could be induced.
As such efficient chiral dopants there are the binaphthol derivatives described in GB-A-2 298 202. However chiral binaphthol derivatives may undergo partial racemisation when being heated. Besides, their preparation is expensive because it includes asymmetric resolution of binaphthol racemate as a crucial reaction step.
U.S. Pat. No. 4,835,277 (Choe / Hoechst Celanese Corporation) discloses at Example 1 a polymer of
L
-N-p-nitrophenyl-2-pyrrolidinemethyl acrylate:
Synthetic Metals 57 (1), 1993, 3945-3950 (Feng et al.) discloses compounds of the following formula:
The above two documents are in the field of polymer films showing non-linear optical properties. In unrelated fields the following may be mentioned:
&Circlesolid;
Tet. Lett.
27 (36), 1986, 4303-4306 (Calmes et al.) disclosing a compound of the following formula:
&Circlesolid;
Bull. Chem. Soc. Jpn.
60 (11), 1987, 4190-4192 (Kawanami et aL) disclosing what would appear to be a compound of the following formula:
&Circlesolid;
J. Org. Chem.
57, 1992, 1179-1190 (Goldstein et al.) disclosing a compound of the following formula, an enol ether intermediate in a route for the synthesis of amphibian alkaloids:
The synthesis of chiral compounds bearing a carbon atom as a single asymmetric chiral centre is generally trivial and inexpensive. Nevertheless, their use as doping agents for liquid crystals has only provided mixtures with a relatively small HTP. However, we have now discovered that a further class of compounds, including within its scope compounds that exhibit a sterically hindered single chiral centre, is efficient for producing a large HTP.
Thus the invention provides chiral prolinol derivatives of formula 1:
in which:
A
1
, A
2
and A
4
each independently represents hydrogen; an optionally-substituted methyl group; an optionally-substituted aliphatic group with 2 to 80 C-atoms, in which one or more C-atoms may be replaced by a heteroatom, in such a manner that oxygen atoms are not linked directly to one another; or an optionally-substituted aromatic ring system, with 1 to 80 C-atoms; and
A
3
represents an optionally-substituted aliphatic group with 2 to 80 C-atoms, in which one or more C-atoms may be replaced by a heteroatom, in such a manner that oxygen atoms are not linked directly to one another; or an optionally-substituted aromatic ring system, with 1 to 80 C-atoms;
wherein at least one of the A
1
to A
4
residues includes a polymerisable group, with the proviso that, when the only polymerisable group is in the A
3
residue, the polymerisable group does not comprise a double bond directly connected to the carbon atom linking A
3
and A
4
.
The term “aliphatic” includes straight-chain and branched alkyl, as well as saturated and unsaturated groups. Possible substituents include alkyl, aryl (thus giving an araliphatic group) and cycloalkyl, as well as amino, cyano, epoxy, halogen, hydroxy, nitro, oxo etc. Possible heteroatoms which may replace carbon atoms include nitrogen, oxygen and sulphur. In the case of nitrogen further substitution is possible with groups such as alkyl, aryl and cycloalkyl.
The compounds of the invention have surprisingly been found to be efficient for producing a large HTP, even those that exhibit a single chiral centre. Of course, other chiral groups may be present elsewhere in the molecule.
The compounds of the invention may be used as doping agents for liquid crystals for a wide range of applications including solid state cholesteric filters for projection displays, circular polariser, optical filter, etc.
Note that, although one or more of A
1
, A
2
and A
4
may independently represent hydrogen or an optionally-substituted methyl group, A
3
always represents a bulkier optionally-substituted aliphatic group with 2 to 80 C-atoms, in which one or more C-atoms may be replaced by a heteroatom, or an optionally-substituted aromatic ring system. Thus at least one such bulkier group is always present in the compounds of the invention. Although one or both of A
1
and A
4
may represent a small group such as hydrogen or methyl, it is preferable to have several bulky groups. Thus, preferably A
1
, A
3
and A
4
each independently represents an optionally-substituted aliphatic group with 2 to 80 C-atoms, in which one or more C-atoms, may be replaced by a heteroatom, in such a manner that oxygen atoms are not linked directly to one another; or an optionally-substituted aromatic ring system, with 1 to 80 C-atoms.
Preferred embodiments of the invention relates to chiral prolinol derivatives of formula I. wherein:
A
3
and A
4
have each independently one of the meanings of formula II:
—X
1
—(Sp
1
)
n
—X
2
—(MG)—X
3
—(Sp
2
)
m
—P (II)
A
2
is a hydrogen atom or has one of the meanings of formula II
b
or one of the meanings of formula II
c:
and
A
1
has one of the meanings of formula II
b
or one of the meanings of formula II
c:
—(Sp
1
)
n
—X
2
—(MG)—X
3
—(Sp
2
)
m
—P (II
b
)
—(Sp
1
)
n
—X
2
—(MG)—X
4
(II
c
)
in which:
X
1
to X
3
each independently denote —O—, —S—, —NH—, —N(CH
3
)—, —CH(OH)—, —CO—, —CH
2
(CO)—, —SO—, —CH
2
(SO)—, —SO
2
—, —CH
2
(SO
2
)—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —SOO—, —OSO—, —SOS—, —CH
2
—CH
2
—, —OCH
2
—, —CH
2
O—, —C(H=CH—, —C≡C— or a single bond;
X
4
is a halogen;
Sp
1
and Sp
2
are each independently straight or branched spacer groups having 1 to 20 C-atoms which may be unsubstituted, mono- or polysubstituted by halogen or CN, it being also possible for one or more CH
2
groups to be replaced, in each case independently from one another, by —O—, —S—, —NH—, —N(CH
3
)—, —CH(OH)—, —CO—, —CH
2
(CO)—, —SO—, —CH
2
(SO)—, —SO
2
—, —CH
2
(SO
2
)—, —COO—, —OCO—, —OCO—O—, —S—CO—, —CO—S—, —SOO—, —OSO—, —SOS—, —C≡C—,
Cherkaoui Zoubair
Schmitt Klaus
Huff Mark F.
Rolic AG
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