Bicyclooctane derivatives

Details Bicyclooctane derivatives Bicyclooctane derivatives

1987-04-23

1989-09-19

Gron, Teddy S.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

2522995, 350350X, 350350S, 558414, 558423, 558425, C09K 1932, C07C12164, C07C 2522, C07C 43225

Patent

active

048679046

DESCRIPTION:

BRIEF SUMMARY
The invention relates to new bicyclooctane derivatives of the Formula I ##STR2## wherein R.sup.1 and R.sup.2 are each an alkyl group which has 1 to 12 C atoms and in which one or two non-adjacent CH.sub.2 groups can also be replaced by --O--, --CO--, --O--CO--, --CO--O-- and/or --CH.dbd.CH--, substituted by F or Cl, and the other group is 1,4-phenylene or 1,4-cyclohexylene, and A.sup.1 is also a single bond, subject to the provisos that to the CN group, if A.sup.1 is a single bond, Z is a --CH.sub.2 CH.sub.2 -- group and R.sup.2 is CN, group and one F-substituent in A.sup.2 is located in the meta-position relative to R.sup.2, single bond and the lateral substituent in A.sup.2 is F.
These substances can be used as components of liquid-crystal phases, in particular for displays based on the principle of the twisted cell or the guest-host effect, the field effect or the bi-stability effect.
The invention was based on the problem of finding new, stable, liquid-crystal or mesogenic compounds suitable for use as components of liquid-crystal phases.
It has been found that the bicyclooctane derivatives of the Formula I are excellently suitable for use as components of liquid-crystal phases. In particular, they make it possible to prepare stable liquid-crystal phases which have a relatively high ratio of the elastic constants K.sub.3 /K.sub.1 and a positive or negative dielectric anisotropy and are particularly suitable for field effect and/or bi-stability effect displays. In field effect displays using mixtures of negative dielectric anisotropy, the phases according to the invention exhibit particularly steep characteristic lines, as a result of which it is possible to achieve high multiplex ratios. In field effect displays using mixtures of positive dielectric anisotropy, the addition of compounds according to the invention results in particularly flat characteristic lines. By this means the number of possible greysteps in TFT-addressed displays based on the principle of the twisted cell or the guest-host effect is decisively enlarged. Compounds of the Formula I wherein R.sup.2 is CN are particularly suitable for this purpose.
In liquid-crystal displays having memory properties based on bi-stability effects, the addition of compounds according to the invention results in an increase in tolerance for the uniformity of the layer thickness of the display to the pitch of the liquid-crystal mixture, as a result of which the mass production of such displays is decisively facilitated.
In addition, the provision of the compounds of the Formula I considerably enlarges, in a very general manner, the range of liquid-crystal substances suitable, from various aspects of technical performance in use, for the preparation of liquid-crystal mixtures.
The compounds of the Formula I have a wide field of use.
They can be added to liquid crystal base materials composed of other classes of compounds in order to increase the K.sub.3 /K.sub.1 values of such a phase, or can themselves serve as a base material having high K.sub.3 /K.sub.1 values.
The invention therefore relates to the bicyclooctane derivatives of the Formula I and to a process for their preparation which consists in subjecting an appropriate diazonium tetrafluoroborate to thermal decomposition or reacting an appropriate nitro compound with caesium fluoride in order to prepare fluorine compounds, or treating an appropriate diazonium salt with copper (I) chloride in order to prepare chlorine compounds, or treating with a reducing agent a compound which otherwise corresponds to the Formula I but contains one or more reducible group(s) and/or additional C--C bond(s) instead of H atoms, or etherifying an appropriate hydroxyl compound in order to prepare ethers of the Formula I, or reducing a corresponding keto compound in order to prepare compounds of the Formula I containing an ethyl bridge.
The invention also relates to the use of the compounds of the formula I as components of liquid-crystal phases. The invention also relates to liquid-crystal phases containing at least one

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