Liquid crystal compounds

Details Liquid crystal compounds Liquid crystal compounds

2001-10-17

2004-06-08

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299610, C252S299620, C252S299630, C252S299670, C560S055000, C560S056000, C560S085000, C560S128000

Reexamination Certificate

active

06746729

ABSTRACT:

The invention relates to new liquid crystalline compounds, mixtures of those compounds and their application in optical and electro-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 these optical components depends upon its associated optical properties such as the optical anisotropy, refractive index, transparency and dispersion.
LCPs are manufactured by orientating a layer of a polymerisable liquid crystal single compound or mixture on an orientated substrate and cross-linking that layer to form a liquid crystal polymer (LCP) network. The configuration imposed by the orientation layer on the polymerisable LC single compound or mixture becomes fixed or frozen into the LCP network formed on cross-linking. The resulting LCP films are characterised by a high viscosity and are stable to mechanical stresses, temperature and light exposure. It is highly desirable that the polymerisable LC compounds used in the manufacture of the LCPs are chemically and thermally stable, stable to electromagnetic radiation, soluble in standard solvents and miscible with other LC components. The compounds should also exhibit liquid crystalline properties over the range 0 to 150° C., preferably 25 to 100° C.
Polymerisable liquid crystal compounds are known from EP 0 748 852, EP 0 700 981, EP 0 699 731, US 5 567 349, WO 97/00600, WO 98/52905 and WO 95/22586. These compounds are characterised by a relatively narrow liquid crystal range.
Materials comprising LCPs are generally prepared from a mixture of components, which includes at least one polymerisable LC single compound. The properties of the LCP material thus prepared depend upon the nature and properties of the components comprising the mixture. It is highly desirable that the components used in the preparation of the LCP materials are compatible. If the components of the mixture are incompatible, the corresponding mixtures may possess thermodynamic properties that make them unsuitable for use in LC devices. Incompatible LC mixtures are characterised by properties such as a depression of the clearing point, a reduction in the liquid crystalline range and problems in achieving a uniform orientation of the LCP material in the preparation of devices.
There is therefore a need for a liquid crystalline single compound or mixture which exhibits a broad liquid-cnrstalline thermal range and which can, alternatively or additionally, 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. There is also need for further liquid crystalline mixture components that are compatible with the other components of a liquid crystal mixture.
It has been surprisingly found that by using certain long chain compounds containing at least one mesogenic group, it is possible to prepare mixtures and materials having the ability to address, at least in part, the needs described above.
A first aspect of the invention provides a compound of formula I:
wherein
A
1
to A
4
are independently selected from the group consisting hydrogen, a methyl group and a hydrocarbon group containing from 2 to 80 carbon atoms in which one or more carbon atoms are optionally replaced by a heteroatom selected from the group consisting —O—, —S—, and —N— with the proviso that firstly no two oxygen atoms are joined together and secondly that at least one of A
1
to A
4
includes a polymerisable group;
B
1
represents a hydrocarbon group containing from 4 to 80 carbon atoms, in which one or more carbon atoms are optionally replaced by a heteroatom selected from the group consisting —O—, —S—, and —N— with the proviso that no two oxygen atoms are joined together;
MG
1
and MG
2
are the same or different and each independently represents an aromatic or non-aromatic carbocyclic or heterocyclic ring system containing from 2 to 80 carbon atoms, with the proviso that firstly at least one of MG
1
and MG
2
comprises at least two ring systems and secondly when MG
1
and MG
2
are identical either A
1
and A
2
or A
3
and A
4
are different or at least three of A
1
to A
4
are different.
The compounds of the invention are chiral or achiral and preferably have a substantially linear backbone, the groups A
1
, MG
1
, B
1
, MG
2
and A
2
being linearly arranged with respect to each other. It has been surprisingly found that the compounds of formula I can adopt a liquid crystalline mesophase over a broad thermal range. In addition they are characterised by melting points that are considerably lower than those of at least one of their mesogenic constituents. They are also valuable in the production of well-oriented LCP films having either a high or low optical birefringence and variable tilt.
For each of the groups A
1
to A
4
, the term “hydrocarbon” is understood to include straight-chain and branched alkyl, alkenyl and alkynyl groups as well as cyclic groups. The terms “alkyl”, “alkenyl” and “alkynyl” will accordingly be understood to include branched and straight chained groups. It will therefore be appreciated that one or more of the groups A
1
to A
4
may be selected from the group consisting of a C
1
-C
20
alkyl, C
1
-C
20
alkoxy, C
1
-C
20
alkoxycarbonyl, C
1
-C
20
alkylcarbonyl and a C
1
-C
20
alkylcarbonyloxy group. Examples of C
1-20
alkyl groups that may be present in the compounds of the present invention include, without limitation, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl and the like. Examples of C
1-20
alkoxy groups that may be present in the compounds of the present invention include, without limitation, methoxy, ethoxy, n-propoxy, isopropoxy, butoxy, pentyloxy, exyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy and the like. Examples of C
1
-C
20
alkoxycarbonyl groups that may be present in the compounds of the present invention include, without limitation, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentyloxycarbonyl, hexyloxycarbonyl, octyloxycarbonyl, nonyloxycarbonyl decyloxycarbonyl, undecyloxycarbonyl, dodecyloxycarbonyl and the like. Examples of C
1
-C
20
alkylcarbonyl groups that may be present in the compounds of the present invention include, without limitation, acetyl, propionyl, butyryl, valeryl, hexanoyl, heptanoyl, octanoyl, nonanoyl, decanoyl, undecanoyl, dodecanoyl, terdecanoyl and the like. Examples of C
1
-C
20
alkylcarbonyloxy groups that may be present in the compounds of the present invention include, without limitation, acetoxy, propionyloxy, butyryloxy, valeryloxy, hexanoyloxy, heptanoyloxy, octanoyloxy, nonanoyloxy, decanoyloxy, undecanoyloxy, dodecanoyloxy, terdecanoyloxy and the like. Cyclic groups may contain up to 6 ring carbon atoms.
For the group B
1
, the term “hydrocarbon” is understood to include straight-chain and branched alkylene, alkenylene and alkynylene groups. The terms “alkylene”, “alkenylene” and “alkynylene” will be accordingly understood to include branched and straight chain groups.
Each of the hydrocarbon groups of A
1
to A
4
and B
1
are optionally substituted by a substituent selected from the group consisting of C
1-20
alkyl, C
2-20
alkenyl, C
2-20
alkynyl, C
4-20
aryl, C
3-20
cycloalkyl, C
3-20
cycloalkenyl, C
3-20
cycloalkynyl, amino, cyano, epoxy, halogen, hydroxy, nitro or oxo.
By the term “halogen” it should be understood to include fluorine, chlorine, bromine and

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