Abstract: Compounds which may be used as a dopant or host in a ferroelectric chiral smectic liquid crystal mixture. The compounds are characterized in that they are derivates of an X-hydroxy carboxylic acid and contain the chiral unit (I), in which Ro may be alkyl, alkoxy, halogen, formula (II), where b may be 0 to 3 and the phenyl ring may be substituted, and a is 0 or 1. The chiral unit is combined with a range of mesogenic combinations of groups. Lactic acid derivatives are described in detail (i.e. Ro.dbd.methyl) together with various preparative routes, for example the compound formula (III), which has dopant properties in a range of hosts.

Abstract: A dyesheet for thermal transfer printing comprises a substrate supporting a transfer coat comprising one or more thermally transferable dyes dispersed throughout a polymeric binder comprising a mixture of polyvinylbutyral and a cellulosic polymer in which the percentage by weight of polyvinylbutyral lies within the range 65-85%.

Abstract: A thermal transfer printing sheet suitable for the printing of black images in a dye diffusion thermal transfer printing process. The sheet comprises a substrate having a coating comprising a black dye mixture comprising from 5 to 60% of a dye of Formula 1, from 5 to 60% of Formula 2, from 5 to 60% of a dye of Formula 3 and/or from 1 to 60% of a dye of Formula 4.

Abstract: A transfer sheet, suitable for use in a dye diffusion thermal transfer printing process for the production of images in accordance with a pattern information signal, comprising a substrate having a coating comprising a binder, one or more anthraquinone dyes of Formula I ##STR1## wherein R.sup.1 represents alkyl, alkenyl, cycloalkyl, haloalkyl, cyanoalkyl, alkoxyalkyl, alkoxyalkoxyalky, hydroxyalkyl, hydroxyalkoxyalkyl, hydroxyalkylthioalkyl, tetrahydrofurfuryl, alkenyloxyalkyl, tetrahydrofurfuryloxyalkyl, alkoxycarbonylalkyl, alkoxycarbonyloxyalkyl or alkoxycarbonyloxyalkyl, andR.sup.2 represents any of the substituents represented by R.sup.1 or a radical of the formula: ##STR2## wherein R.sup.3, R.sup.4 and R.sup.5 each independently represents hydrogen, halogen, and one or more bisazo dyes of Formula II:A--N.dbd.N--B--N.dbd.N--E IIwherein:A is the residue of a diazotizable phenylamine or naphthylamine, A--NH.sub.

Abstract: A thermal transfer printing sheet comprising a substrate having a coating comprising a mixture of dyes of 20-50% of Formula I and of 80-50% of Formula II. ##STR1## wherein: R.sup.1 is C.sub.1-12 -alkyl;x is halogen; andR.sup.2 is aryl or C.sub.1-4 -alkyl unsubstituted or substituted by C.sub.1-4 -alkoxy, C.sub.1-4 -alkoxy-C.sub.1-4 -alkoxy or aryl.

Abstract: A method for improving the stability of a color print formed by dye-diffusion thermal transfer printing, comprises placing against the print a panel of transfer coat comprising a dye-absorbant binder which is substantially free from any thermally transferable materials, and heating at least those areas of the print to which one or more dyes have been transferred, thereby to cause absorption by said panel of dye molecules at the surface of the print. This may conveniently be carried out as part of the printing operation by using a dyesheet having a transfer coat comprising a plurality of uniform panels containing different colored thermally transferable dyes held in a dye-absorbant binder, and further panels comprising a dye-absorbant binder which is substantially free from any thermally transferable materials.

Abstract: A dyesheet for thermal transfer printing comprises a substrate supporting a transfer coat comprising a plurality of uniform panels containing different colored thermally transferable dyes, and a further panel in which instead of a colored dye there is a thermally transferable colorless absorber of ultraviolet radiation. Using such a dyesheet, a layer of UV absorber can be applied very simply as an extension of the printing process, by causing the receiver to pass through the printer once more, in contact with the further panel, essentially as though the UV absorber were merely a further color to be added to the print.

Abstract: A thermal transfer printing sheet suitable for use in a thermal transfer printing process, comprising a substrate having a coating comprising a binder and an anthraquinone of the Formula I: ##STR1## or a mixture of an anthraquinone dye of the Formula I and a disazo dye of Formula II:A-N=N-B-N=N-E IIwherein:Z is hydrogen or an optionally substituted aliphatic or an optionally substituted aryl radical;A is the residue of a diazotizable phenylamino or naphthylamine, A-NH.sub.2, carrying no more than one unsaturated electron-withdrawing group;B is an optionally substituted thiophen-2,5-ylene or thiazol-2,5-xylene; andE is the residue of an aromatic coupling component E-X wherein X is an atom or group displaceable by a diazotized aromatic amine.

Abstract: A compound having ferroelectric liquid crystal properties of the formula: ##STR1## wherein A is the residue of a liquid crystal material or a liquid crystal compatible material;X is O or S;n is 0 or 1;Y is any inert group which does not cause the melting point of the compound of Formula I to exceed 200.degree. C.;R.sup.1 is selected from H, C.sub.1-4 -alkyl and halogen; andR.sup.2 is C.sub.1-4 -alkyl or halogen;provided that R.sup.1 and R.sup.2 are different. In a suitable environment the compound is capable of alignment in two metastable states and is therefore suitable for use in multiplex-addressed, liquid crystal devices, such as flat bed large area screens and displays.

Abstract: Novel lactic acid derivatives which may be used as a component of a ferroelectric smectic liquid crystal mixture, which derivatives have the general formula: ##STR1## in which R.sub.1 is alkyl or alkoxy and R.sub.2 is alkyl. Liquid crystalline compositions containing these compounds are also described.