Liquid crystalline compounds

Details Liquid crystalline compounds Liquid crystalline compounds

2001-04-10

2003-10-07

Huff, Mark F. (Department: 1756)

Compositions

Liquid crystal compositions

C252S299610

Reexamination Certificate

active

06630076

ABSTRACT:

The invention relates to new liquid crystalline compounds, mixtures of those compounds and their application in optical devices. More particularly, it relates to the use of a component of a polymerisable liquid crystalline mixture in the production of orientated liquid crystalline polymers; compounds used as components in polymerisable liquid crystalline mixtures; liquid crystalline mixtures comprising these components, liquid crystalline polymers prepared from such components; and liquid crystalline devices comprising those compounds.
Liquid crystal polymers (LCPs) are used in the manufacture of optical components such as waveguides, optical gratings, filters, retarders, piezoelectric cells and non-linear optical cells and films. The choice of LCP for use in any one of the aforementioned optical components depends upon its associated optical properties such as the optical anisotropy, refractive index, transparency and dispersion. Optical filters, for example, contain LCPs having a large anisotropy (&Dgr;n) and a low dispersion (n=f(&lgr;)).
In some applications there is a requirement to produce LCPs in which the component molecules adopt a specific tilt angle or orientation with respect to the plane of the substrate or to a plane perpendicular to the substrate. These LCP materials can be used as optical components such as compensation layers and retarders. Such optical components may be used in the production of liquid crystal devices (LCDs) with improved viewing angles, for example.
LCPs are manufactured by orientating a layer of a polymerisable liquid crystal single compound or mixture on an orientated substrate and cross-linking the mesogenic layer to form a liquid crystal polymer (LCP) network. Polymerisable LC compounds used in the manufacture of the LCPs need to be chemically and thermally stable, stable to electromagnetic radiation, soluble in standard solvents and miscible with other LC components, and to exhibit liquid crystalline properties over the range 25 to 150° C., preferably 25 to 80° C. The configuration imposed by the orientation layer on the polymerisable LC single compound or mixture becomes fixed or frozen into the LCP network formed upon cross-linking. The resulting LCP films have a high viscosity and are stable to mechanical stresses, temperature and light exposure.
There is therefore a need for a liquid crystalline single compound or mixture which exhibits a broad liquid-crystalline thermal range and which can be orientated on a substrate prior to cross-linking in such a way that the orientation of the LC single compound or mixture on the substrate remains stable over the period required for manufacturing the LCP network. Components which may be used in photo-crosslinkable liquid crystalline layers are particularly desirable.
Compounds known from the prior art include those disclosed in EP-A-0675186, EP-A-0700981 and EP-A-0748852 (all F. Hoffmann-La Roche A G). The three earlier documents disclose compounds such as (taken from EP-A-0675186):
U.S. Pat. No. 3,971,824 (Van Meter et al./Eastman Kodak Company) discloses in its broadest aspect compounds of the following formula:
though in fact there is no enabling disclosure of anything other than the following:
where X is chlorine.
Previous strategies used for obtaining the desired thermal and optical properties with a given LCP material have mainly relied upon mixtures of compounds comprising at least one liquid crystalline polymerisable monomer and the combination of their individual properties. However due to the general incompatibility of the latter components at the molecular scale, the thermodynamic behaviour of their corresponding mixtures is generally undesirable (for example, a depression of the clearing point, a reduction of the liquid crystalline range etc.), besides some problems of miscibility between the different components of the mixture leading to difficulties in achieving a uniform orientation of the LCP material. To ameliorate this situation, a new concept of obtaining LCP materials of special thermal and optical properties was investigated. This concept uses chemical junctions at lateral positions of different molecules, at least one of them being mesogenic, having each one or more of the properties which are required in the final LCP material. Depending on the application, these properties can be selectively induced from at least one of the mesogenic stairs of the new “staircase molecules”.
Thus the invention provides chiral or achiral “staircase” compounds of formula I:
wherein:
A
1
to A
6
each independently represent hydrogen; an optionally-substituted methyl group; or an optionally-substituted hydrocarbon group of 2 to 80 C-atoms, in which one or more C-atoms may be replaced by a heteroatom, in such a way that oxygen atoms are not linked to one another;
B
1
and B
2
each independently represent a single bond, an oxygen atom or an optionally-substituted hydrocarbon group of 1 to 80 C-atoms, in which one or more C-atoms may be replaced by a heteroatom, in such a way that oxygen atoms are not linked to one another;
MG
1
and MG
3
each independently represent an optionally-substituted aliphatic group with 1 to 80 C-atoms, in which one or more C-atoms may be replaced by a heteroatom, in such a way that oxygen atoms are not linked to one another; or an optionally-substituted aromatic or non-aromatic carbocyclic or heterocyclic ring system; with 1 to 80 C-atoms;
MG
2
represents a group comprising at least two and up to four optionally-substituted aromatic or non-aromatic carbocyclic or heterocyclic ring systems, with 1 to 80 C-atoms, wherein, when MG
2
represents a group comprising four optionally-substituted ring systems, at least three of the ring systems are aligned in between B
1
and B
2
;
n1 and n2 are each independently 1 or 2, where “n1=2” (or “n2=2”) indicates the presence of two separate linkages via the groups B
1
(or the groups B
2
) between the groups MG
1
and MG
2
(or MG
2
and MG
3
); and
n3 is a positive integer up to 1000;
with the proviso that:
when A
3
and A
4
both represent hydrogen, then both MG
1
and MG
3
represent an araliphatic group with 1 to 80 C-atoms, in which one or more C-atoms may be replaced by a heteroatom, or an optionally-substituted aromatic or non-aromatic carbocyclic or heterocyclic ring system, with 1 to 80 C-atoms; and at least two of A
1
, A
2
, A
5
and A
6
each independently represent an optionally-substituted hydrocarbon group of 3 to 80 C-atoms, in which one or more C-atoms may be replaced by a heteroatom;
when A
1
, A
2
, A
5
and A
6
all represent hydrogen, then A
3
and A
4
both represent an optionally-substituted hydrocarbon group of 3 to 80 C-atoms, in which one or more C-atoms may be replaced by a heteroatom; and
when MG
2
represents a group comprising two or three optionally-substituted ring systems, then neither of A
3
and A
4
includes an aromatic ring.
The term “aliphatic” includes straight-chain and branched alkylene, 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. Likewise, the terms“alkyl” and “alkylene”, as used herein, includes straight-chain and branched groups, as well as saturated and unsaturated groups.
When MG
2
represents a group comprising four optionally-substituted ring systems, at least three of the ring systems are aligned in between B
1
and B
2
. Thus, at least three of the rings are all in a discrete identifiable block positioned in between B
1
and B
2
, not in an arbitrarily defined region with some of the rings protruding from the axis of the molecule connecting B
1
with B
2.
Comparison may be made with compounds such as Compound I-a of EP-A-0675186:
which could be drawn with an arbitrarily defined Z-shaped central portion

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