Laterally substituted curable liquid crystals

Details Laterally substituted curable liquid crystals Laterally substituted curable liquid crystals

2001-09-17

2004-05-11

Huff, Mark F. (Department: 1756)

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

C252S299010, C252S299610, C252S299630, C560S061000, C560S085000

Reexamination Certificate

active

06733690

ABSTRACT:

The present invention relates to laterally substituted curable Liquid Crystals (LCPs) having mesogenic properties or properties which cause these LCPs to be compatible with a mesogenic molecular structure. In particular the present invention relates to laterally substituted curable Liquid Crystals (LCPs) with adjustable optical anisotropy and in parallel with low melting point or good supercoolability, relatively high clearing point and good alignment properties and the use of such LCPs in the preparation of substantially uniform or patterned film in which the orientation of the LCP molecules in the plane and relative to the plane of the substrate can be controlled.
Films prepared from curable Liquid Crystals (LCP films) are well known to a skilled person and are used in the preparation of optical and electro-optical devices. U.S. Pat. No. 5,650,534 discloses compounds and mixtures used to prepare components suitable for use non-linear optical (NLO) applications. These compounds are optically active and exhibit chiral smectic or chiral nematic mesophases. U.S. Pat. No. 5,707,544 also discloses compounds and mixtures suitable for use in NLO applications. However, these compounds are characterised by relatively high melting points. U.S. Pat. No. 5,593,617 discloses photochemically polymerisable liquid crystal compounds and mixtures, which are used to prepare optical and electronic components. However, these mixtures have a relatively narrow operating range and are unsuitable for use at higher temperatures.
LCP films are generally manufactured by using known coating techniques such as spin coating. This involves casting an organic solution of a cross-linkable LCP or LCP mixture onto a substrate provided with an orientation layer. The organic solvent is subsequently removed to give a well-oriented, solvent-free mesogenic LCP layer, which in turn is cross-linked to give an LCP film. The desired optical performance of such films depends crucially on some reproducible physical parameters which the LCP material has to fulfill simultaneously. Such properties are a nematic mesophase, a high clearing point, a low melting point or a low tendency to crystallise when cooled below melting point (supercooling), good solubility in organic solvents, good miscibility with other LCPs, good aligning properties on orientation layers, and the ability to form an adjustable tilt out of the substrate plane essentially free of tilt domains and disclinations. Tilt domains are regions within the LCP film in which the long axes of the LCP molecules form tilt angles out of the plane of the substrate of the same size but in opposite direction. Disclinations are borderlines of neighbouring tilt domains where LCP molecules of opposite tilt angles are adjacent. These tilt domains and disclinations result in both a disturbance in the uniform appearance of the film and an inhomogeneous optical performance.
Good aligning properties and the ability to form an adjustable tilt angle are of particular relevance if photo-orientated and photo-patterned orientation layers are used for the orientation of LCPs. This so-called linear photo-polymerisation (LPP) technology (cf. e.g.
Nature
, 381, p. 212 (1996)) allows the production of not only uniform but also structured (photo-patterned) orientation layers. If such structured orientation layers are used for the orientation of LCPs, the LCP molecules should adapt the information given by the orientation layer with respect to the direction of alignment and the tilt angle.
For adjusting the optical properties of the layers and films prepared from LCPs as for example retardation films, it is further essential to have available a variety of LCP materials with differing optical anisotropy, mainly high optical anisotropy. It is known that LCPs exhibiting a high optical anisotropy often show a negative impact on several of the above properties. Particularly the formation of smectic mesophases, high melting points, an enhanced tendency to crystallise, a low solubility in organic solvents or reduced miscibility with other LCPs is observed. Furthermore the ability of homogeneous alignment free of tilt domains and disclinations is often reduced.
There is, therefore, a need for a new LCP material that may be used in the preparation of an LCP mixture, which significantly reduces the aforementioned disadvantages. The present invention addresses that need.
A first aspect of the invention provides a compound of formula (I)
wherein
G
1
and G
2
independently represent a polymerisable mesogenic residue;
X represents a group selected from —CH
2
—, —O—, —CO—, —COO—, —OOC—, —CONR′—, —OCOO—, —OCONR′;
Sp represents a group of the formula —(CH
2
)
p
— in which p is an integer of 1 to 18 and in which one or two non adjacent —CH
2
— groups are optionally replaced by —CH═CH—; or in which one or two —CH
2
— groups are optionally replaced by one or two groups selected from the group consisting of —O—, —CO—, —COO—, —OOC—, —CONR′—, —OCOO—, —OCONR′ with the proviso that firstly the spacer group does not contain two adjacent heteroatoms and secondly when X is —CH
2
—, p can also have a value of 0; and
M represents an achiral group of formula (II)
 in which
A and B independently represent a six membered isocyclic or heterocyclic group or naphthalenediyl;
C is selected from the group consisting of a five and six membered isocyclic or heterocyclic group or naphthalenediyl;
n
1
and n
2
are 0 or 1 with the proviso that firstly 1≦n
1
+n
2
≦2 and secondly, when C is naphthalenediyl 0≦n
1
+n
2
≦2;
Z
1
is selected from the group consisting of —O—, —COO—, —OOC—, —CO—, —CONR′—, —NR′CO—, OCOO—, —OCONR′—, —NR′COO— and a single bond;
 in which
R′ is selected from the group consisting of hydrogen, a lower achiral alkyl group and a lower achiral alkenyl group;
Z
2
and Z
3
are independently selected from the group consisting of single bond, —COO—, —OOC—, —CH
2
—CH
2
—, —CH
2
O—, —OCH
2
—, —CH═CH—, —C≡C—, —(CH
2
)
4
— and —(CH
2
)
3
O—; and
R
1
is selected from the group consisting of —CN, —COR, —COOR, —OCOR, —CONR′R, —NR′COR, OCOOR, —OCONR′R, —NR′COOR, —F, —Cl, —CF
3
, —OCF
3
, —OR and —R
 in which
R is selected from the group consisting of hydrogen, an achiral C
1-18
alkyl group and an achiral C
4-18
is alkenyl group with the double bond at 3-position or higher; and
R′ is as defined above;
with the proviso that at most one of the rings A, B and C is a naphthalenediyl group.
In addition to the laterally substituted mesogenic compounds referred to above, such compounds are also disclosed in WO 95/24454 and WO 95/24455. However, many of these compounds are not suitable for preparing LCP films with high optical anisotropy without one or more of the aforementioned disadvantages. It has been found that by using the compounds of the present invention it is possible to control the optical anisotropy of LCPs without significant increase of melting point or decrease of clearing point. In addition they generally have a surprisingly low tendency to crystallise even far below the melting point (good supercoolability). Furthermore they generally exhibit enhanced alignment properties especially on structured LPP orientation layers, they are able to form tilt angles and show a decreased tendency to form tilt domains and disclinations. Furthermore the compounds of the invention have a comparatively good solubility in organic solvents and a high miscibility with other LCP compounds.
The optical anisotropy of the compounds of the invention may be easily adapted to requirements only by selecting different groups of M of formula I without changing the main core of the molecule. This allows an economical access to a broad range of LCPs exhibiting different optical anisotropies with a minimum of chemical steps in their production.
The polymerisable mesogenic residues G
1
and G
2
may be the same or different, but are preferably the same.
The group X is preferably selected from the group consisting

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