AMIDE LIQUID CRYSTAL COMPOUNDS: MIXTURES AND DEVICES USING THEM

Abstract: Novel amides of formula (I), where X is (II), and Y is (III), Z<1>, Z<2> are -O- or NR DEG , R DEG being C1-12 alkyl or H, R<1> is H, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, halogen, cyano, R DEG COOCH(CH3)COO, R DEG OOCCH(CH3)OOC; A, B are -, OOC, COO, CH2CH2, -N=N-, -N(O)=N-; a, b, c, f, g, y are 0 or 1; R is CH3 or phenyl; D, E are H, alkyl, Y'-alkyl, Y''-alkoxy, or D and E together with the N represent the residue of an N-containing heterocyclic group; and ( alpha ) to ( gamma ) represent cyclic groups. Such compounds may be used in ferroelectric smectic liquid cystal mixtures, especially as pitch compensators. Preferred amides have y as O and X-CO-Z<1>-CH(R)- as formulae (IV) or (V). A liquid crystal composition and device using these amides are described.

Description: AMIDE LIQUID CRYSTAL COMPOUNDS: MIXTURES AND DEVICES USING THEM This invention relates to liquid crystal mixtures and to compounds for use in them. The invention is particularly concerned with ferroelectric smectic liquid crystal mixtures and compounds. The invention also relates to electro-optical devices incorporating these mixtues. Ferroelectric smetic liquid crystal materials utilise the ferroelectric properties of the chiral tilted smectic phase, ie the chiral smectic C, F, G, H, I, F and K phases (hereinafter designated S* etc, the asterisk * denoting chirality) . The S* phase is most c c commonly sought for use in electro-optical devices as it is the most fluid, and it is also desirable that the material shows an S phase and a nematic (N) phase at temperatures above the S* phase, to assist c in surface alignment. Ferroelectric liquid crystal materials ideally have a low viscosity, a broad smectic liquid crystal temperature range, stability etc, and should show a high spontaneous polarisation _2 coefficient (Ps, measured in nCcm ). Although some single component materials show these properties, it has become common practice to use a mixture of compounds which together show a chiral tilted smectic phase. Generally such mixtures include at least one compound which shows a smectic phase without necessarily being chiral (" smectic host"), and at least one optically active compound (" chiral dopant") the presence of which in the mixture induces the mixture to show a chiral smectic phase with a usefully high Ps. It is desirable that the chiral tilted smectic phase of such a mixture has a helical pitch length that is comparable to the spacing of the electrodes of the electro-optical device in which it is to be used. The pitch length of a chiral smectic mixture depends upon the "winding" effect of the optically active compounds included in it. A good measure of the winding effect of an optically active compound is the pitch length of the cholesteric (Ch) (chiral nematic (N*) phase induced by the compound when it is mixed with a nematic liquid crystal material a small pitch indicating a powerful winding effect. By observation of the sense of the Ch pitch which is induced, the sense of the helical smectic pitch which would be induced by the compound may also be determined. It is common practice to include two or more optically active compounds in a ferroelectric smectic liquid crystal mixture, one or more of- which are dopants serving to induce a high Ps, and one or more of the others having a winding effect of an opposite sense to that of the dopant(s), but not necessarily inducing a high Ps. The other optically active compound(s) serve(s) to "unwind" the helical phase induced by the dopant(s) and hence can be used to control the S* pitch length. This effect is called "pitch compensation", and it is desirable that an optically active compound used in this way ("a pitch compensator") unwind the helical phase induced by the dopant has a powerful winding effect. It is an object of the present invention to provide novel compounds which may be used as components of ferroelectric smectic liquid crystal mixtures, particularly as optically active dopants and pitch compensators. Other objects and advantages of the present invention will be apparent from the following description. According to a first aspect of the present invention an opti¬ cally active compound is provided, being an amide of formula I below: .CO.N Formula I wherein X is a group having the structure: wherein Y is a srouø having the structure: wherein Z 1 and Z? are independently selected from -0- , -NR°-, where R β is C ._ ^ alkyl or hydrogen; wherein Fr is hydrogen, alkyl, alkoxy, alkylcarbonyloxy, alkoxy- carbonyl, hydrogen, halogen, CN , P. * C00CH(CH-, )C00 or R°00CH- (CH-)OOC: wherein A and B are independently selected from a single covalent bond, COO, 00C, CH 2 CH 2 , -N=N-, -M(0)=N-: wherein a, b, c, f, g and y are independently 0 or 1 : wherein R is methyl or phenyl: and wherein D and E are independently selected from hydrogen, alkyl -Y -alkyl, -Y -alkoxy, wherein Y and Y are indepenαently selec¬ ted from the structures from which Y may be selected, or D and E together with the N represent the residue of a heterocyclic N-con¬ taining ring systeπ wherein each of the cyclic groups A to G\ are independently selected from 1,4-linked phenyl optionally carrying one or more substituents and/or having one or two =CH- units replaced by nitrogen; 1,4-linked trans-cyclohexane optionally carrying one or more substituents and/or having one or two CK„ groups replaced by oxygen, nitrogen or sulphur; or bicyclo(2,2,2) octane. Many amides of Formula I are suitable for use as components of ferroelectric smectic liquid crystal mixtures as dopants but especially as pitch compensators. According to a further aspect of the invention there is therefore provided a ferroelectric smectic liquid crystal mixture which contains at least one amide of Formula I. Particular usefulness for use as a component of such a mixture is among the factors deciding the structural preferences discussed below. I Preferably y is 0 and Z is -0-. Compounds of this structure have the additional advantage of ease of synthesis. Preferably R is methyl. Preferably the amid-of Formula I contains not more than three of the cyclicgroups \-^/ ^o ( G > Preferably R contains 1-12 carbon atoms and is alkyl or alkoxy, which may be n-alkyl or n-alkoxy, or branched (iso) or chiral alkyl or alkoxy. Preferred alkyl groups contain 5-12 carbon atoms, and preferred chiral alkyl groups are 2-methylbutyl and 2-methylheptyl. Preferably R when present contains 1—4 carbon atoms. Preferably all of the rings when present are phenyl and unsubstituted, but a preferred lateral substituent is fluorine. Some preferred examples of structures for the acyl group of the amide of Formula I are listed in table 1 below, where the cyclic groups shown may carry substituents as defined above, particularly a lateral fluorine substituent. Structures la and Ip are especially preferred. Table 1 R 1 - θ * 5>-G00GH( )G0 la R 1 -<g - θ)-G0N(R O )GH(R)C0 If R X - θ - )-G00GH(R)C0 lb lg R 1 -/ r /θ -COOGH(R)GO lc Ih R 1 * ^^-<Q)-C00-(θ)-GCN(R O )CH(R)G0 11 R X →(θ)-/^-GOO-<Q)-CO_T(R 0 )GH(R)CO 11 R X -¥VQ>-G00-<©>-G0N(R O )CH(R)G0 1m R x -/ i θ-σoo> o)-coocH(R)co lr R X -- θ)- >-GOO-/θ)-GOOCH(R)GO Is It The group N(E)D may have a number of preferred structures encompassed by Formula I, as discussed below. N(E)D may be a primary amine or anilino group, ie -NHR' where R* is alkyl, especially n-alkyl containing up to 10 carbon atoms where n is 0 to 5 and where R" is alkyl or alkoxy especially n-alkyl or n-alkoxy containing up to 10 carbon atoms. R" when present preferably is in the para (•-.) position, and n is preferably 1 or 0. N(E)D may be a secondary amine or anilino group, ie where R' and R" are independently alkyl containing up to 10 carbon atoms, and R"' is alkyl or alkoxy containing up to 10 carbon atoms. R', R" and R"' are preferably n-alkyl or n-alkoxy containing up to 6 carbon atoms, n is 0-5, preferably o or 1 and R"' when present is preferably in the para (4) position. When N(E)D represents a heterocyclic N- containing ring system it is preferably a five or six membered heterocyclic ring system, which may contain a second nitrogen or an oxygen atom in the ring. Some preferred heterocyclic ring systems from which N(E)D may be selected include the following: ( R' ) n where (R') indicates that one or more substituents R' may be present n on the ring, R* being selected from alkyl, alkoxy, halogen, C 3 and CN. When present R' is preferably n-alkyl containing up to 8 carbon atoms, especially methyl, n may have valves from 0 up to the total number of available substitution positions on the ring, but is preferably 0, 1 or 2. Amides of formula I may be prepared from the appropriate base H-N(E)D and the appropriate carboxylic acid by well known methods for the synthesis of amides. As the asymmetric centre indicated by -K in formula I is either in an alpha-hydroxycarboxylic acid group (eg a lactate ** * group -0-CH(CH.-)C0- ) or in an a inoacid group (eg - H.CH(CH.,)CQ-) it is convenient to start the preparation of the amides from the optically pure enantiomes of the alpha-hydroxycarboxylic acid or arciino acid. Some suitable generally applicable routes are routes A, B and G shown in Figs. 1, 2 and 3. where x is 1, 2 or 3 and R' is alkyl or alkoxy. The amide H0GH(R)C0N^ used in step C(ii) nay be prepared for example from the corresponding alpha-hydroxycarboxylic acid by a reaction analogous to step A(iv), with the prelimnary prec¬ autionary step of protecting the a . ha-hydroxyl group as shown for example in route D in Fig. •+ In routes A, B, G and D the general procedure is as below: Route A (i) 90?- aq methanol, 20% aq Gs CO-, pH 7; PhCH 2 Br, DMF (ii) a. when x is 2, _.,_T-dicyclohexylcarbo- -diimide (DCC), *+-(N-pyrrolidino)pyridine (N-PPy), CH^Cl^ b. when x is 3, 1 -@>- θ -{θ - C00H ' S0C1.,, Et-N O^Cl- (iii) % Pd-G, ethyl acetate, H- (iv) (CH.)_C.C0C1, 0 N-CH-. ; H-N? , C Ϊ-CH-. 33 >— i 3 D ' 65 3 Route B (i) R 1 -L/θ i-C00H, oxalyl chloride, DMF; amino acid, CHgC ,, NaHCO.- (ii) as in route A step (iv) Route G (i) aq NaOH, ethanol, PhCH 2 Br (ii) as route A step (iv), H0GH(R)G0NJ (iii) Pd-C, ethanol, H 2 (iv) as route A step (ii) (v) as rout B step (i), HN(R o )CH(R)C00H (vi) as route A step (iv) (vii) as route G step (iii) (viii) as route A step (ii) Route D (i) aq NaOH, ethanol, ?hGH 2 3r (ii) as step A(iv) (iii) 5? Pd-G, ethanol, Pl- ϊ__ny of the starting materials for Routes A, B and G are commercially available in optically pure enantiomeric forms. For example the alpha hydroxycarboxylic acids lactic acid and mandelic acid, which may be used in steps A(i), and (ii): R R=CH- = lactic acid = mandelic acid are atailable from the Aldrich Chemical Company. The amino acid used in Routes B and C may also be a commer¬ cially available naturally occurring amino acid, such as those listed in Table 2 below, in which the group R which is present in the structure is indicated. Table 2 amino acid _R Glycine H C-, -Alanine CH. Valine (CH 3 ) 2 CH Leucine (CH ) 2 .CH.CH 2 Isoleucine CH-.CH 2 .CH(CH-) The aaino acids listed in Table 2 all have hydrogen as R . To prepare amino acids where R is alkyl, the alkylation methods described by E Fischer and W Lipschitz, "Chem. Ber" (1915) p 360-378 where the preparation of N-methylalanine, N-methy} leucine, N- tπethylphenylalanine and N-methyl-tyrosine are described. Examples and further discussion of methods similar to step B(i) and C(v) are given in Applicant's copending GB 8620111 and PCT?/GB86/00599- Exa ples of suitable bases for use in Routes A and C and C(vi), ie compounds H-N(E)D are listed below in Table 3. Table 3 H-NHC n H 2n+1 for all values of n=1 to 12 inclusive. H-N(C n H 2π+1 )(CmH 2 _, +1 ) for all values of n and m independently selected from 1 to 12 inclusive. selected , R 3 is preferably methyl. A ferroelectric smectic liquid crystal mixture of the invention will normally contain at least one smectic host (or defined above). Some preferred classes of compounds from which the smectic host compound(s) may be selected are shown in table 4 below many of which are commercially available. Hosts containing one or more compounds of formulae 4.1 or 4.2 are particularly preferred. The mixture will contain at least one amide of Formula I, which may be present as a race ic mixture of its optical enantiomers but is preferably present as an optically active enantiomer for example to function as a chiral dopant. In a preferred embodiment the mixture also contains at least one other optically active smectogenic compound, for example to function as a chiral dopant (as defined above). By "smectogenic" is meant that the compound wither shows a smectic phase, especially smectic C, or else that it may be mixed with a smectic material to result in a smectic mixture. If the mixture contains such a optically active compound as well as an amide of Formula I, then preferably the sense of the helical pitch induced in the smectic phase by at least " one of the smectogenic optically active compounds is opposite to that induced by at least one of the amides of Formula I, so that the amide of Formula I functions as a pitch compensator to control, eg to lengthen or shorten the helical pitch of the S* phase induced by the smectogenic compound. Preferably when used as a pitch compensator only one optically active amide of formula is included in the mixture, together with only one chiral dopant, the dopant not being an amide of Formula I. A large number of chiral dopants is known; some preferred classes of chiral dopants which may be used together with an amide of Formula I as pitch compensator are listed in table 5, those of structure 5.5 being especially preferred particularly those with n=0 and R being branched alkyl. Other known chiral dopants include the optically active compounds disclosed in EPA's 86306261, 0110299, 0152217, 0164814, 0174191, 136845, 168963, 160416, 167328, 115693, 153826, 131373, 175591, 157519, 159872- GB 8629322; PCT GB/87/00131 and W086/0087 among others. Table 4 racemic race ic where R A and RB are G - 2 n-alkyl or n-alkoxy. Table 5 CH R°- θ - δ)-C00CHC00-R° 5.1 where n-alkoxy, an ndependently con a n ng - 1 carbon atms, E and R is G- _ n-alkyl, branched chain alkyl, cycloalkyl or phenylalkyl. n in structure 5-5 is 0 or 1. A further advantage of the amides of Formula I is that when included in a ferroelectric smectic liquid crystal mixture, especially as pitch compensators, in many cases they are particularly helpful in suppressing undesirable smectic phases which might otherwise occur at low temperatures. It is sometimes desirable that the mixture does show an S phase at a temperature above the S* phase, for example to assist in alignment of the liquid crystal material, and in such cases it may be desirable to include an additive such as a compound of general formula RAA -_</θ^)_-/<§7-\}_-rc<nono_-</7o : -)-_p RB] A 3 where R ' and R are as defined above to promote the appearance of such an S phase. In other cases it may be desirable to include other additives to further suppress the appearance of low temperature S or S_ D, phases, such as compounds of general structure: A B where R and R are as defined above. Typically when an amide cf Formula I is used as a chiral dopant in a ferroelectric smectic liquid crystal mixture, the mixture has the following composition: One or more host compounds, eg j 1 to 99 weight % table 4 compounds. j (preferably up to 90%) One or more optically active 1 to 30 weight % amides of Formula I Additives, eg to control . . . . f 0 to 20 weight % other smectic phases Typically when an amide of Formula I is used as a pitch compensator together with a chiral dopant not being an amide of Formula I, the mixture has the following composition: One or more host compounds, I 1 to 99 weight % eg table 4 compounds J (preferably up to 90%) One or more chiral dopants, 1 1 to 30 weight % eg table 5 compounds J Optically active amide ] 0.001 to 10 weight % of Formula I J (preferably 0.01 to 2.5 weight %) Additives, eg to control " j other smectic phases J 0 to 20 weight % The total in each case being 100 weight %. The relative amounts of each of the above components in the mixture will depend upon the use for -which the mixture is intended and the composition can be tailored to fit the requirements. Generally the Ps of the mixture is directly proportional to the amount of the chiral dopant in the mixture, and the unwinding effect of a pitch compensator is proportional to the amount of the compensator present. Such a mixture may be used in any of the known types of ferroelectric smectic liquid crystal electro-optic device, for example as describee in Appl. Phys. Lett.26, (1980) p899. An example of such a device is the "Clark Lagerwall Device", described in Reference 1, and also in "Recent Developments in Condensed Matter Physics" J^ f p309, (1981) (Reference 3). The physics of this device, and methods of constructing σn<i . are well known. In practice such a device usually consists of two sub¬ strates, at least one of which is optically transparent, electrodes on the inner surfaces of the substrates and a layer of the liquid crystal material sandwiched between the substrates. The Clark Lagerwall device uses a layer of liquid crystal material between the substrates of a thickness comparable to or less than the helical pitch of the S* configuration, which causes the helix to be unwound by surface interactions. In its unwound state the material has two surface stabilised states with director orientations (ie molecular tilt direction) at twice the tilt angle to one another, and also permanent dipσle orientations perpendicular to the substrates ut in opposite directions. An alternative approach to providing cell3 for a Clark- Lagerwall device having a thicker layer of liquid crystal material is to use an applied electric field to induce homogeneous alignment through interaction with the dielectric ' anistropy of the liquid crystal material. This effect requires a chiral smectic material having a negative dielectric anisotrαpy, eg provided by incorpora¬ tion of a compound having a lateral halogen or cyaπo substituent. Such a compound may itself be chiral or πoπ-chiral and smectic or non-smectic. In general chiral smectic C materials (S 5 are used in these displays because these are the most fluid, but in principle the ώσre ordered chiral smectics could also be used. A pleochroic dye may also be incorporated in the liquid crystal material to enhance the electro-optic effect. Such a device incorporating compounds of Formula I offers the possibility of a high switching speed of a few microseconds - as demonstrated in Reference 3 - together with bistable storage capa¬ bility; consequently it is likely to have important applications in displays, optical processing devices, and optical storage devices. According to the present invention in a further aspect, there_ is provided an electro-optical device, operating by a ferroelectric effect in a liquid crystal material, wherein the liquid crystal material is a mixture of compounds at least one of which is a co - pound of Formula I. The device may, for example, be a Clark-Lagerwall device as described above, and may comprise two substrates at least one of which is optically transparent, electrodes on the inner surfaces of the substrates, and a layer of the liquid crystal material sandwiched between the substr tes. The liquid crystal mixtures incorporating a compound of Formula I are especially suited for use in rapidly switched large screen (eg A size) displays, such as are used in portable computers, desk top calculators and visual display units, and by using appropriately shaped substrates and electrodes the electro-optical device of the invention _ay be made in this form. In this description and the accompaying examples the following symbols and abbreviations are used: and Ph represent a phenyl (benzene) ring. <_) C using sodium D line. tic thin layer chrom tography. c concentration. S, R designations of absolute configuration of chiral centre. (+), (-) designations of sense of optical rotation of an optically active (chiral) material. All temperatures are given in G. The invention will now be described by way of example only with reference to Figs 1 to 4 which illustrate preparative routes for compounds of formula 1 and Fig 5 which shows a sectional view of a liquid crystal electro-optic display device. Exa Dle 1 Route A Step lA( i ) Preparation of S-( -)- M O - CH CO-_ H -_- P -_ ( A ) 3 S-(+)- Lactic acid (18.0 g) was dissolved in methanol (360 cm ) 3 and water (40 cm ) v/as added. The solution was titrated to pH 7.0 (pH meter or pH paper) with a 20% aqueous solution of caesium carbonate 3 (ca. 160cm ). The solvent was removed under reduced pressure at 50°C and the residue v/as re-evaporated twice from N, -dimethylformamide 3 (DI'IF) (2 x 100cm ) at the same temperature. The white solid caesium 3 salt obtained was stirred wit benzyl bromide (34.2g) in DMF (300 cm ) for 15 h. The caesium bromide was filtered off, the filtrate was concentr 3 ated and then ether was added to the residue (150 cm ) . The organic 3 layer was v/ashed successively with water (100 cm ) , saturated NaHC0_ 3 3 (500 cm ) and water (100 cm ) and finally dried (MgS04) . After removal of the solvent, the residual liquid was distilled under reduced pressure to afford the product as colourless liquid, yield 28.8g (30%), bp 96°C (0.05 mm Hg) o ~ § 4 - 12.9 (c 0.01, CHC1 ) . l.ote: Commercially available S-(+)- lactic acid (Aldrich) was redistilled before it was used. Ref. S.S.Wang, J. Org. Chem. 4l, 3 8, (1976). Step lA( ii) Preparation of s-(+)- C s H n co_ : CH-_- P (B) To a stirred mixture of 4-octyloxybiphenyl -4'-carbo;cylic acid (10.8 g) , S-(-)-benzyl lactate (A) (5.G g) and 4-pyrrolidinopyridine (n-PFY) (0.49 g) in sieve-dried CH„C1- (250 cu J ) , a solution of l.,N- άicyclohexylcarbodiimiάe (DCC) (7.5 g) in sieve dried CH-Cl- (50 cm ) _. _. was added slowly. The reaction mixture was stirred for 5h at room temperature. The N.ff-dicyclohe ylurea (DCU) was filtered off and the fil ra e v/as washed wuccβtsεύvely with water (100 cm") , 5- aqueous acetic acid (100 cm°) , water (2 x 100 cm ) and finally dried (I-ϊgSO ) . After removal of the solvent, the crude diester was purified by column chro atography using silica gel and dichloromethane : petroleum fraction (bp 60-80°C) (4 : 1) as eluent. The product was crystallised from ethanol. Yield 11.lg (6S%) , mp 62.5°C, { * -__ " ] ^ + 24.7 (c 0.01, CHC1-). Ref. A. Hassner & V. Alexanian, Tetrahedron Letters 4j5, 4475, (1978). Step lA(iii) Preparation of CH 3 S -(+)- C 8 M n O -^^-CD l CH . COiVi (C) Compound (B) (11.Og) was dissolved in ethyl ethanoate (150 ml), 5% Pd on charcoal (200 mg) v/as added and the mixture was stirred under an atmosphere of hydrogen overnight. After hydrogenation 3 (500 cm of hydrogen consumed) was completed, the catalyst was filtered cff and the filtrate was evaporated to dryness. The colourless solid residue (singiispot by tic) was crystallised from petroleum fraction (bp 60-80°C) to give the required carboxylic acid (C) as L -i 24 oi I + 40.8° (c 0.01 CHCl . Step lA(iv) Preparation of S-(+)- 8 H π O H j ( D ) A stirred solution of compound (C) (1.59 g 0.004 mol) and ri-methylmorpholine (0.40 g, 0.004 mol) in sodium dried toluene (30 ml) v/as cooled to 0°C and trimethylace yl chloride (0.43 g, 0.004 ι,ιol) in sodium-dried toluene (5ml) was added dropwise. After 2 hr at 0°C, n-butylamine (θ.35g» 0.0043 mol) in sodium-dried toluene (5ml) was added dropwise to the reaction mixture. The mixture was then stored at 8 C overnight. The mixture was then diluted with toluene (40 ml) and washed successively with aqueous NaHGO^, water, aqueous HCl and water and finally dried ( gSO-.). After removal of the solvent, the crude amide was purified by column chromatography on silica gel, using chloroform : ethyl etha- noate (95:5) as eluent. The product was recrystallised from ethanol : ethyl ethanoate (3:1) to afford compound D as colourless needles Yield 1.15 S (64 ) p 168° C [O-l]^ = +62.4° (in GHG1 cone 0.01). Analogous amides were prepared using the appropriate amine instead of n-butylamine in step lA(iv), and the appropriate car- boxylic acid. Properties of some of these are listed in tables 6 and 7 below. TABLE 6 GH- 1 J '-<__>-<o>- ' COOGHGO-A -x 8.0 NHBu 168 +62.4 9 N eBu 69 +51.3 0.121 0.120 10 N eΞt 71.5 +48.3 0.062 0.081 3.0 100.0 +56.8 0.C61 0.075 10 82.0 +56.6 0.028 0.033 8.0 N •-^Λ /'p ent 96.5 +60.0 3.0 ^\/ 109.0 +53.3 9 N ^"\ 93 *° +54.1 0.066 0.075 10 N-^ 89.0 +59.1 He 10 65.5 +68.0 0.096 0.107 10 N I 48.0 +75 0.060 0.058 * N^ e 10 H- θ -Bu 151.0 +87.7 0.066 0.079 10 NH- θ -0Me 74.0 +179.08 TABLE 7 CH- I J R- θ)- Q>-G00-cQ -C00CHG0-A A Liq Cryst Transitions 9.0 NMeBu CC 11114411 ( ( 111111 )) SS** +29.6 c 9.0- ^ Me C 140 I +35.0 0.091 0.10 C 79 158 BP 159 I +40.5 0.077 0.069 Note: a. the S* phase was monotropic. b. appears to form a Ch phase at c j a 80°C (on rapid cooling) but recrystalisation occurred almost instantaneously at the same temperature. In tables 6 and 7 the following abbreviations are used: R = 8.0 means C 0 H,_0, 9 means C_H, n , 10 means C -rt H_, o 1/ 9 19 1U <_.l ex. Me = methyl Et = ethyl Bu = n-butyl Pent = n-pe tyl melting point (°C) optical rotation at 24°C, Na-D line, in Chloroform. N* = Chiral nematic pitch ( ) in E7 at room temperature measured by (L) • *_ laser diffraction, ( ) = carnot wedge C = solid crystal I = isotropic liquid BP = blue phase Ch = cholesteric (chiral nematic) E7 is a nematic liquid crystal mixture having a composition: n-C^-^-c^-CN 25 wt The Ps and tilt angle of some of the above compounds was measured in a mixture with a smectic material having a composition: xture rred to er as The Ps was measured at a temperature 10°C below the S* - 5 transition of the mixture, and extrapolated to 100% of the compound (ext Ps). Compound ext Ps Tilt Angle (°) CH, C 9 H 19 -<δ)-<§-G00CHC0N.--/ 35 18 1-5 Ta b les 6 and 7 therefore show the extremly small Ch pitch of the compounds, and their suitability for inclusion in a ferroelectric smectic liquid crystal material is shown by selected examples giving a Ps in a smectic mixture. * . The compounds wherein the group N(E)D was -]$^~~-- QR or -NH--- 0 / --GH- 5 showed exceptionally small Ch pitches. Example 2 A ferroelectric smectic liquid crystal mixture was prepared having the following compostion: HI (as defined above) SO wt% D ( + )_ L _ The optical activity of the two optically active compounds was chosen so that the amide functioned as a pitch compensator to the dopant cyano-compound. This mixture had liquid crystal transition temperatures (°C): and was S* at room temperature and lower. The mixture therefore contained less than 0.5 weight % of the amide pitch compensator. An example of the use of a compound of Formula I in a liquid crystal material and device embodying the present inven¬ tion will now be described with reference to Figure 5. In Figure 5 a liquid crystal cell comprises a layer 1 of liquid crystal material exhibiting a chiral smectic phase sand¬ wiched between, a glass slide 2 having a transparent conducting layer 3 on its surface, eg of tin oxide or indium oxide, and a glass slide k having a transparent conducting layer 5 on its surface. The slides 2,1. bearing the layers >5 are respec- tively coated by films 6,7 of a polyimide polymer. Prior to construction of the cell the films 6 and7 are rubbed with a soft tissue iα a given direction the rubbing directions being arranged parallel upon construction of the cell. A spacer 8 eg of polymethyl methacrylate, separates the slides 2, 4 to the required distance, eg 5 microns. The liquid crystal material 1 ' is introduced between the slides 2,4 to the required distance, eg 5 microns. The liquid crystal material 1 is introduced between the slides 2,4 by filling the space between the slides 2, _, and spacer 8 and sealing the spacer Q in a vacuum in a known way. Preferably the liquid crystal material is in the smec¬ tic A, nematic or isotropic liquid phase (obtained by heating the material) when it is Introduced beteen the slides 2,4 _c facilitate alignment of the liquid crystal molecules with the rubbing directions on the slides 2, *> A polarizer 9 is arranged with its polarization axis parallel to the rubbing direction on the films 6,7 an< -*- an analyzer (crossed polarizer) 10 is arranged with its polar¬ ization axis perpendicular to that rubbing direction. When a square wave voltage (from a conventional source not shown) varying between about +10 volts and -10 volts is applied across the cell by making contact with the layers 3 an *-*- 5 the cell Is rapidly switched upon the change in sign of the voltage between a dark state and a light state as explained above. In an alternative device (not shown) based on the cell construction shown in Figure 5 c * ιe layers 3 3 - n ~ 5 ma -Y ^ e sexectively shaped in a known way, eg by photoetching or deposition through a mask, eg to provide one or more display symbols, eg letters, numerals, words or graphics and the like as conventionally seen on displays. The electrode portions formed thereby may be addressed In a variety of ways which include multiplexed operation. The chiral smectic liquid crystal mixture of example 2 above is suitable for use as the layer 1 of liquid crystal rat- erial in this device.

Claims: CLAIMS 1. An amide having a formula: R E X-CO-Z 1 - -Y-G0-Z 2 * -GHG0N ' y * " ^ D where X has a structure: where Y has a structure: where Z 1 and Z2 are independently selected from -0- and -NR 0 -, where R° is C alkyl or hydrogen; where R is hydrogen, alkyl, alkoxy, alkylcarbonyloxy, alkoxycarbonyl, hydrogen, halogen, CN, R° C00CH(CH 3 )C00 or R°00CH(CH 3 )00C; where A and B are independently selected from a single covalent bond, COO, 00C, CH 2 CH 2 , -N=N-, -N(0)=N-; where a, b, c, f, g and y are independently 0 or 1; where R is methyl or phenyl; I where D and E are independently selected from hydrogen, alkyl -Y -alkyl, II I II -Y -alkoxy, wherein Y and Y are independently selected from the structures from which Y may be selected, or D and E together with the N represent the residue of a heterocyclic N-containing ring system, and where each of the cyclic groups are independently selected from 1,4-1inked phenyl optionally carrying one or more substituents and/or having one or more =C-i- units replaced by nitrogen; 1,4-linked trans-cyclohexane optionally carrying one or more substituents and/or having one or more CH ? groups replaced by oxygen, nitrogen or sulphur; or bicycto (2,2,2) octane. 2. An amide according to claim 1 characterised in that y is 0 and Z is -0-. 3. An amide according to claim 2 characterised in that R is methyl. 4. An amide according to claim 3 characterised in that XCOZ has a structure selected from * 1 -<θWθ-∞°- and R X -<0>-<0)-Goo-g)-coo- 5. An amide according to claim 4 characterised in that R is n-alkyl or n-alkoxy containing 1 to 12 carbon atoms. 6. An amide according to claim 2 characterised in that -N(Ξ)D is a primary amine or primary anilino group having a structure selected from -NHR' where R is alkyl and R is alkyl or alkoxy, n is 0 to 5, and R and R contain up to 10 carbon atoms. I 7. An amide according to claim 6 characterised in that R and R are II n-alkyl or n-alkdxy, n is 1 and R is in the para (4) position. 8. An amide according to claim 2 characterised in that -N(E)D is a secondary amine or anilino group having a structure selected from -NR'R" and t It where R and R are independently alkyl containing up to 10 carbon atoms, II I and R is alkyl or alkoxy containing up to 10 carbon atoms and n is 0 to 5. I II II I 9. An amide according to claim 8 characterised in that R , R and R II I are selected from n-alkyl and n-alkoxy, n is 1 and R is in the para (4) position. 10. An amide according to claim 2 characterised in that -N(E)D represents a 5 or 6 membered heterocyclic ring system which may contain a second nitrogen or an oxygen atom in the ring system. 11. An amide according to claim 10 characterised in that the heterocyclic ring system has a structure selected from the following: (H?') n (H') n <R') a <a') a (R * )n where R is a substituent selected from alkyl, alkoxy, halogen, CF and CN_ and n may have valves from 0 up to the total number of available substitution positions on the ring. 12. An amide according to claim 11 characterised in that n is 0, 1 or 2 and R is n-alkyl containing up to 8 carbon atoms. 13. A ferroelectric smectic liquid crystal material being a mixture of at least two compounds, characterised in that at least one of the compounds is an amide as claimed in any one of claims 1 to 3. 14. A ferroelectric smectic liquid crystal material being a mixture of at least two compounds characterised in that at least one of the compounds is an optically active amide as claimed in any one of claims 4 to 12. 15. A material according to claim 14 characterised in that the amide has a structure in which N(E)D is selected from: 16. A material according to claim 14 characterised in that it contains at least one compound of general formula A 3 where R and R are independently C n-alkyl or n-alkoxy. 17. A material according to claim 14 characterised in that the material contains at least one optically active smectogenic compound which is not an amide of Formula I. 18. A material according to claim 17 characterised in that the smectogenic compound is selected from compounds having a general formula - o where R may be n-alkyl or n-alkoxy, and R may be n-alkyl or C D n-alkoxy, and R independently containing 1 - 12 carbon atms, and R E is G _ n-alkyl, branched chain alkyl, cycloalkyl or phenylalkyl and n is 0 or 1. 19. A material according to claim 17 characterised in that the smectogenic compound has a formula C E where R is n-alkyl or n-alkoxy containing 1-12 carbon atoms and R is C. __ n-alkyl branched alkyl, cyclo alkyl or phenyl alkyl, n being 0 or 1. 20. A material according to claim 19 characterised in that the smectogenic compound has a ormula where R" is branched alkyl, 21, A ferroelectric smectic liquid crystal electro-optic display device characterised in that it uses a liquid crystal material that includes at least one compound of Formula I.

Inventors: BRADSHAW MADELINE JOAN, BRIMMELL VICTORIA, GRAY GEORGE WILLIAM, LACEY DAVID, MING LAWRENCE KAM, SCROWSTON RICHARD MICHAEL, TOYNE KENNETH JOHNSON, BRADSHAW, MADELINE, JOAN, BRIMMELL, VICTORIA, GRAY, GEORGE, WILLIAM, LACEY, DAVID, MING, LAWRENCE, KAM, SCROWSTON, RICHARD, MICHAEL, TOYNE, KENNETH, JOHNSON
Applicants: SECR DEFENCE BRIT, THE SECRETARY OF STATE FOR DEFENCE IN HER MAJESTY'
Application year: 1987
Main classification: C07C103
IPC codes: C07C67, C07C231, C07C241, C07C253, C07D207, C07D211, C07D231, C07D233, C07D239, C07D295, C09K19, G02F1