Terpenoid derivatives and liquid crystal materials and devices c

Details Terpenoid derivatives and liquid crystal materials and devices c Terpenoid derivatives and liquid crystal materials and devices c

1986-09-22

1988-11-15

Gron, Teddy S.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229901, 2522995, 25229963, 25229964, 25229965, 25229966, 25229967, 25229968, 350350F, 350350S, 560 55, 560 59, 560 73, 560102, 560106, 560107, 560108, 560109, 560113, G02F 113, C07C 6976, C07C11910, C07D23926, C09K 1934, C09K 1912, C09K 1920, C09K 1952

Patent

active

047847930

DESCRIPTION:

BRIEF SUMMARY
This invention relates to liquid crystal compounds and liquid crystal mixtures which exhibit ferroelectric properties.
The first work on ferroelectric switching liquid crystal display devices by N A Clark and S T Lagerwall reported in Applied Physics Letter Vol. 36 No. 11 pp 899-901 (June, 1980) (Reference 1) used DOBAMBC or HOBACPC as the ferroelectric liquid crystal. These materials are, for most applications, far from ideal because they are relatively unstable chemically and sensitive to light, their spontaneous polarisation coefficients are relatively small, and their tilted smectic phases are at inconveniently high temperatures and exist over inconveniently high temperatures and exist over inconveniently small temperature ranges.
This invention is concerned with the provision of ferroelectric liquid crystal mixtures having larger coefficients of spontaneous polarisation (P.sub.s) and improved temperature range of tilted smectic phases.
We believe that the relatively small values of P.sub.s exhibited by DOBAMBC and HOBACPC result at least in part from the relatively free rotation in these molecules of the chiral group relative to the remainder of the molecule. It is suggested that a molecule with the same or similar polarity on its chiral group should, in the absence of conflicting factors, exhibit enhanced spontaneous polarisation if the structure of the molecule is modified to increase the steric hindrance to hinder the rotation of the chiral group. However, it is usually the case that the means by which steric hindrance can be achieved militates against the formation of liquid crystal phases, particularly those with a relatively wide temperature range.
The present invention is therefore directed to ferroelectric liquid crystal mixtures having two major constituents neither of which on its own necessarily exhibits any spontaneous polarisation. One of these two constituents, which does not on its own necessarily exhibit any tilted smectic phase, and hence does not on its own necessarily have to exhibit any spontaneous polarisation, is or contains at least one compound which is optically active (chiral) and exhibits a high degree of steric hindrance of the chiral group of its molecule relative to the remainder of the molecule. This first constitutent, which may be a single compound or a mixture is generally described in ferroelectric liquid crystal chemistry as a "dopant".
The second constitutent is provided by a material that is compatible with the first constituent and exhibits a tilted smectic phase, C, I, F, J, K, G, H or X (abbreviated herein to "S.sub.C " etc), over an acceptably wide temperature range. This second material does not necessarily contain any chiral centre in its molecular structure, and hence it likewise does not on its own necessarily have to exhibit any spontaneous polarisation. This second constituent, which may also be a single compound or a mixture, is generally described as a "host" in ferroelectric liquid crystal chemistry. The smetic C phase is generally preferred as this is the most fluid.
These two constituents act co-operatively in the mixture, with the host serving to provide the requisite tilted smectic phase of a ferroelectric mixture, while the dopant provides the requisite chirality of the resulting chiral tilted smectic phase of the mixture, and preferably also inducing a high Ps in the mixture. Chiral smectic liquid crystal phases are identified herein by S*, e.g. S.sub.C *.
According to a first aspect of the present invention there is provided an ester which is a derivative of a terpenoid alcohol and which has the formula (1): having the formula: --(A.sub.3).sub.c --B.sub.3 --(A.sub.4).sub.d --L-- lateral substituents, or a 2,6- or 1,4-linked naphthalene group optionally laterally substituted in one or more positions, or a 1,4-linked phenyl group having one or two .dbd.CH-- groups replaced by nitrogen, particularly a 2,5-linked 1,3-pyrimidine;
wherein each of A.sub.1, A.sub.2, A.sub.3 and A.sub.4 independently represents a 1,4-linked phenyl group optionally carry

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