Ferroelectric liquid crystal device

Abstract: A ferroelectric liquid crystal device having a pair of substrates each provided with voltage appli­ cation means, an orientation control layer formed on at least one of the substrates, and a layer of ferro­ electric liquid crystal composition formed between the pair of substrates, the device being characterized in that the ferroelectric liquid crystal composition comprises at least one compound (a) having an optically active group of the formula (I): and at least one compound (b) which is reverse to the compound (a) in the direction of a helical pitch induced in a nematic phase, the liquid crystal composi­ tion exhibiting at least a smectic C phase, smectic A phase and nematic phase at least 20µm in helical pitch.

Description: The present invention relates to ferroelectric liquid crystal devices, and more particularly to a ferroelectric liquid crystal device having a ferroelectric liquid crystal layer which comprises a specific ferroelectric liquid crystal composition. Liquid crystal display devices most widely used at present are those utilizing a nematic phase but having the drawback that they are not adapted for large-capacity display, for example, with 1000 x 1000 lines. For instance, the usual twisted nametic (TN) liquid crystal display devices suffer loss in contrast with an increase in the number of lines, so that it is practically impossible to fabricate high contrast large-capacity liquid crystal devices of this type with 1000 x 1000 lines. To overcome the drawback of TN liquid crystal display devices, supertwisted nematic (STN) liquid crystal display devices and double supertwisted namatic (DSTN) liquid crystal display devices have been developed, but these devices still have the drawback of lower contrast and lower response speed with increasing number of lines. Such devices presently available are therefore limited to a display capacity of about 1000 x 720 lines. On the other hand, the prior art has already provided liquid crystal display devices of the active matrix type wherein thin-film transistors (TFT) are arranged on a substrate. Although it is technically possible to give devices of this type a large display capacity, for example, of 1000 x 1000 lines, these devices have the drawback of necessitating a long production process and being low in yield and therefore very costly to fabricate. As promising means for overcoming the above problems, ferroelectric liquid crystal display devices have been proposed which operate on a different principle from the TN display device (see N. A. Clark et al., Appl. Phys. Lett., 36 , 899(1980)). The proposed device utilizes the chiral smectic C phase and chiral smectic I phase of ferroelectric liquid crystals. The device can be given a large display capacity with an improved speed of response since the memory property of the crystals is utilized. Furthermore, the device can be produced at a low cost since there is no need to use active components such as thin-film transistors. The ferroelectric liquid crystal display device also has the advantage of having a wide field of view. Thus, such devices appear very promising as large-capacity display devices having at least 1000 x 1000 lines. The liquid crystal material for use in ferroelectric liquid crystal display devices which utilize the smectic C phase must of course exhibit the smectic C phase over a wide temperature range around room temperature and needs to fulfill various other requirements. First, the device for large-capacity display must demonstrate high-speed response and from this viewpoint, the liquid crystal material needs to be highly amenable to spontaneous polarization and be low in viscosity. Further the material needs to exhibit satisfactory orientation and bistability when used for the liquid crystal cell. It is also desired that the material has a tilt angle which is relevant to the contrast and brightness of liquid crystal displays. At present, however, it is impossible for a single compound to fulfill all the desired requirements, so that a plurality of compounds are usually mixed together for use as a liquid crystal composition. To prepare a liquid crystal composition fulfilling the requirements for actual use, it is necessary to use numerous single liquid crystal compounds having a wide variety of properties. It is sometimes likely that compounds which per se exhibit no liquid crystal properties will be useful as components of a liquid crystal composition. The present invention which has been developed in the light of the above situation, seeks to provide a ferroelectric liquid crystal device which is operable in a wide range of temperatures and is satisfactory in orientation and memory property and which exhibits high-speed response at room temperature. The present invention provides a ferroelectric liquid crystal device comprising a pair of substrates each having means for applying a voltage thereto, an orientation control layer formed on at least one of the substrates, and a layer of ferroelectric liquid crystal composition formed between the substrates, characterized in that the ferroelectric liquid crystal composition comprises at least one compound (a) selected from optically active compounds, of the formulae (II) and (II') described below, and at least one compound (b) which in the nematic phase has a reverse induced helical pitch, the liquid crystal composition exhibiting at least a smectic C phase, a smectic A phase and a nematic phase having a in helical pitch of at least 20 µm. (Since the chiral smectic C phase and the nonchiral smectic C phase are considered to be thermodynamically identical, these phases will be referred to herein as "smectic C phase" without making any distinction between them. Similarly, the chiral nematic phase and the nonchiral nematic phase are considered to be thermodynamically identical, so that these phases will be referred to herein as "nematic phase" without distinguishing between them.) The compounds of the formulae (II) and (II') described below contain a gamma-lactone ring of the formula (I): in which the carbon atoms * are asymmetic carbon atoms which are responsible for the optical activity. The optically active groups of the formula (I) may be in the cis-form or in the trans-form, both of which are usable in the invention. Mixtures of the two forms may be used, also. The compounds of the formula (II) are: in which each of A₁, A₂ and A₃ is a group containing a 6-membered ring which may be substituted, X is -O-, -COO-, -OCO- or a single bond, each of Y₁ and Y₂ is -COO-, -OCO-, -OCH₂-, -CH₂O-, -CH₂CH₂-, -CH=CH-, -C≡C- or a single bond, each of R₁ and R₂ is a straight-chain or branched-chain C₁₋₁₅ alkyl, and each of p, q and r is 0 or 1. Examples of straight-chain and branched-chain C₁₋₁₅ alkyl groups represented by R₁ and R₂ are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, 1- or 2-methylbutyl, hexyl, 1- or 3-methylpentyl, heptyl, 1- or 4-methylhexyl, octyl, 1-methylheptyl, nonyl, 1- or 6-methyloctyl, decyl, 1-methylnonyl, undecyl, 1-methyldecyl, dodecyl and 1-methylundecyl. These alkyl groups may have an asymmetric carbon atom in the carbon chain. Examples of groups containing a 6-membered ring which may be substituted, represented by A₁, A₂ and A₃ are the benzene ring, pyridine ring, pyrimidine ring, pyrazine ring, pyridazine ring, piperazine ring, cyclohexane ring, dioxacyclohexane ring, bicyclo[2,2,2]octane ring and naphthalene ring. One or more hydrogen atoms in the 6-membered ring-containing groups may be substituted with a fluorine atom, chlorine atom, bromine atom, cyano, nitro, methyl or methoxy. Examples of preferred compounds represented by the formula (II) are those represented by the following formulae (II)-1 to (II)-7. in which each of R₁, R₂ and p is as defined above, n is 0 or 1, and Z is CN or F. Tables 1 to 7 set out below give examples of more preferred compounds represented by these formulae. The compounds of the formula (II') are: in which R₉ is a straight-chain or branched-chain C₁₋₁₅ aliphatic hydrocarbon group which may include an intervening oxygen atom, R₁₀ is a straight-chain or branched-chain C₁₋₁₅ alkyl group, A₄ is a phenylone group or cyclohexane group, and each of m and n is 0 to 1. Examples of straight-chain and branched-chain C₁₋₁₅ aliphatic hydrocarbon groups which may have an intervening oxygen atom include alkyl, alkoxyalkyl and alkenyloxyalkyl groups, and these groups have 1 to 15 carbon atoms which may be in a straight-chain or a branched-chain. Specific examples of alkyl groups are those exemplified above for R₁ and R₂. Specific examples of alkoxyalkyl groups are methoxymethyl, ethoxymethyl, propoxymethyl, pentyloxymethyl and hexyloxymethyl. Specific examples of alkenyloxyalkyl groups are allyloxymethyl and allyloxyethyl. Table 8 set out below gives examples of more preferred compounds of the formula (II'). The optically active compound of the formula (II), for example the compound in which X = single bond, Y₁ = single bond, Y₂ = single bond, p = 1, q = 1, and r = 0 can be prepared by reacting optically active epichlorohydrin with a phenol in the presence of a base to obtain a compound of the formula (VI) and reacting this compound with a malonic ester of the formula (VII) R₂-CH(COOR₆)₂ (VII) in the presence of a base. In the above formulae, R₁ and R₂ are as defined for the formula (I), and R₆ is methyl, ethyl or other lower alkyl group. A typical method for preparing the optically active compound of the formula (II') will be illustrated in the following Preparation examples. The optically active compounds of the formulae (II) and (II') do not always exhibit a liquid crystal phase. Even when exhibiting this phase, such compounds are not always useful in respect of the phase series and the temperature range of the smectic C phase. Accordingly, it is much more desirable to use these compounds in combination with other compounds than to use them singly. When the compound of the formula (II) or (II') is added in a suitable amount to nonchiral smectic liquid crystal compounds or composition or to chiral smectic liquid crystal compounds or composition, the composition undergoes enhanced spontaneous polarization to exhibit high-speed response as a ferroelectric liquid crystal composition. However, if the compound is added in a large amount, the use of the composition is very likely to encounter problems such as the crystallization of the added compound in the composition and a reduction in the temperature of transition from S C to S A . It is therefore desirable to add the compound in an amount of 0.1 to 20%, more preferably about 0.5 to 10%. The compounds to be used in combination with compounds of the formulae (II) and (II') are suitably those represented by the following formulae (VIII) to (X). R₇-Z₁-B₁-D₁-B₂-Z₂-R₈ (VIII) R₇-Z₁-B₁-D₁-B₂-D₂-B₃-Z₂-R₈ (IX) in which each of B₁, B₂ and B₃ is a benzene ring, cyclohexane ring, bicyclo[2,2,2]octane ring, pyridine ring, pyrimidine ring, pyrazine ring, pyridazine ring, piperazine ring, dioxacyclohexane ring, naphthalene ring or similar group containing a 6-membered ring, a hydrogen atom of which may be substituted with a fluorine atom, chlorine atom, bromine atom, cyano, nitro, methyl or methoxy group, each of D₁ and D₂ is a single bond or -COO-, -OCO-, -CH=CH-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, -CH₂CH₂-, -OCH₂-, -CH₂O-, -COS- or -SCO- group, each of Z₁ and Z₂ is a single bond or -COO-, OCO-, -O-, -S-, -OCOO-or -CO- group, each of R₇ and R₈ is a straight-chain or branched-chain C₁₋₁₅ alkyl group which may contain an asymmetric carbon atom, and s is 1 or 2. In the ferroelectric liquid crystal composition prepared from compounds of she formulae (II) and (II'), various properties or characteristics of the composition need to be considered collectively so that when the composition is used for a ferroelectric liquid crystal device, the device will exhibit satisfactory characteristics. According to the invention, the ferroelectric liquid crystal composition is to exhibit at least a smectic C phase, a smectic A phase and a nematic phase having a helical pitch of not less than 20 µm in order that the ferroelectric liquid crystal device is satisfactory not only in liquid crystal temperature range, tilt angle and response characteristics but also in orientation and memory property. When the composition exhibiting such a phase series is fabricated into a ferroelectric liquid crystal device and thereafter cooled from an isotropic liquid state, a uniform orientation is readily obtained first in the nematic phase since the helical pitch in this phase is at least 20 µm and is therefore sufficiently greater than the cell thickness (usually about 1.5 to about 8 µm) of the device. If the uniform orientation is obtained in the nematic phase, a uniform orientation is easily obtained in the smectic A phase when the device is further cooled. A satisfactory orientation is obtained also in the smectic C phase when the device is further cooled. When thus satisfactory in orientation, the device is also satisfactory in memory property. The ferroelectric liquid crystal composition exhibiting such smectic C phase, smectic A phase and namatic phase having a helical pitch of at least 20 µm can be obtained by using an optically active compound which is reverse to the optically active compounds of the formulae (II) and (II') in the direction of the helical pitch to be induced in the nematic phase, in combination with the optically active compound of the formula (II) or the optically active compound of the formula (II') in a suitable ratio. The combination can be determined, for example, through trial and error so that the helical pitch of the nematic phase will be at least 20 µm, and various other methods. An exemplary method will now be described. A linear addition rule represented by the equation (XI) is known as the pitch of the nematic phase (see J. E. Adams and W. E. L. Hass, Mol. Cryst. Liq. Cryst., 16 , 33(1972)). I/P = Σ(Ci/Pi) (XI) wherein ΣCi = 1, P is the pitch of a liquid crystal mixture, and Ci is the weight concentration of each component having an intrinsic pitch Pi. First, various optically active compounds are added to a liquid crystal compound or composition exhibiting a nematic phase, followed by the measurement of the nematic phase to estimate the intrinsic pitch Pi of each component. Next, the concentrations of the respective components are adjusted so that the pitch of nematic phase of the ferroelectric liquid crystal composition to be obtained becomes not less than 20 µm, using the values obtained. The optically active compounds to be used for the adjustment of pitch can be those of the compounds represented by the formulae (VIII), (IX) and (X) in which one or each of R₇ and R₈ is an optically active group. If possible, such compounds to be used are preferably those identical with the compound having an optically active group of the formula (I), i.e., the optically active compound of the formula (II) or (II') in the direction of spontaneous polarization to be induced in the smectic phase and having a high value thereof, because it is said that the greater the value of spontaneous polarization grows, the higher the speed of response generally. From such a viewpoint,the compounds having an optically active group of the formula (III) can be mentioned as examples of compounds which are identical with the optically active compounds of the formulae (II) and (II') in the direction of spontaneous polarization to be induced in the smectic C phase, have a relatively high value of spontaneous polarization and reverse to these compounds in the direction of helical pitch to be induced in the nematic phase. in which Z is -COO-, -OCO-, -O- or -CO-, R₃ is a straight-chain or branched-chain C₁₋₁₅ alkyl group, B is CH₃, CN, CF₃, CHF₂, CH₂F or a halogen atom (Cl, Br or F), and the carbon atom * is asymmetric. Preferred examples of such compounds are those given below, whereas the compounds to be used in the invention are not limited to these examples. 1) Compounds of the formula (XI): For example, R′ is C₁₀H₂₁O, R″ is C₆H₁₃ and W is H, Z′ is COO (see K. Terashima et al., Mol. Cryst. Liq. Cryst., 141 , 237(1986)). 2) Compounds of the formula (XII): For example, B is F (see J. Bömeburg et al., 12th Int. LC Conf. FF-18(1988)). 3) Compounds of the formula (XIII): For example, R′ is C₆H₁₃, C₇H₁₅, C₈H₁₇ or C₉H₁₉, R″ is C₅H₁₁, C₆H₁₃, C₇H₁₅, C₉H₁₉ or C₁₀H₂₁ and n is 0 or 1 (see Nohira et al., Papers Presented at 14th LC Conf., 40(1988)). 4) Compounds of the formula (XIV): For example, R′ is C₈H₁₇, and R″ is C₆H₁₃ (see A. Yoshizawa et al., Jpn. J. Appl. Phys., 28 , L1269 (1989)). 5) Compounds of the formula (XV): n is 0 or 1, W is H, Cl, Br, F or CN (see Yoshida et al., 15th LC Conf., 1AO1(1989)). 6) Compounds of the formula (XVI): For example, R′ is C₈H₁₇, R″ is and B is Cl (see T. Sakurai et al., J. Chem. Soc., Commun. 978 (1986)). 7) Compounds of the formula (XVII): For example, m is 0 or 1, R′-(O) n - (n is 0 or 1) is C₇H₁₅O-, C₈H₁₇O- or C₁₀H₂₁-, B is CH₃, CF₃, CHF₂ or CH₂F, and R″′ is C₆H₁₃, C₈H₁₇ or CH₂COOC₂H₅ (see, for example, K. Yoshino et al., Jpn. J. Appl. Phys., 26 , L77(1987)). 8) Compounds of the formula (XVIII): For example, R′ is C₉H₁₉, R″ is -CH(CH₃)₂, and B is CH₃ or CN (see I. Sage et al., Ferroelectrics, 85 (1988)). 9) Compounds of the formula (XIX): For example, R′ is C₆H₁₃ and R″″ is (see Miyazawa et al., Papers Presented at 14th LC Conf., 52(1988)). 10) Compounds of the formula (XX): For example, R′ is C H , and R″ is CH₂CH(CH₃)₂ (see C. Tschierske et al., 2nd Ind. Conf. FLC, 83 (1989)). 11) Compounds of the formula (XXI): For example, R′ is C₁₀H₂₁ (see D. M. Walba et al., J. Am. CHem. Soc., 110 , 8686(1988)). 12) Compounds of the formula (XXII): For example, R′ is C₈H₁₇, and Z is CO or CH₂ (see Murakami et al., Papers Presented at 14th LC Conf., 20(1988), and Murakami et al., 15th LC Conf., 1A16(1988)). 13) Compounds of the formula (XXIII): For example, R′ is C₈H₁₇, and R″ is C₈H₁₇ (see M. Koden et al., Mol. Cryst. Liq. Cryst. Lett., 6 , 197(1989)). 14) Compounds of the formula (XXIV): R′ is C₁₀H₂₁ R″ is C₆₁₃, and Y′ is -COO-, -OEO or -OCH₂, Y₂ is COO or O, X is H or Cl (see N. Nakauchi et al., Jpn. J. Appl. Phys. 28 , L1258(1989), and Ikemoto et al., 15th LC Conf., 1A05 (1989)). 15) Compounds of the formula (XXV): For example, R' is C₈H₁₇, R'' is C₄H₉ or C₆H₁₃, and m is 0 or 1. 16) Compounds of the formula (XXVI): For example, R' is C₈H₁₇, R'' is C₂H₅ or C₃H₇, n is 0 or 1, and In the foregoing formulae (XI) to (XXVI), R' and R'' are the same or different and are each a straight-chain or branched-chain C₁₋₁₅ alkyl or alkoxy group, preferably C₅₋₁₁ alkyl or alkoxy group, R''' is a straight-chain or branched-chain C₁₋₁₅ alkyl or alkoxy group or CH₂COOC₂H₅, R'''' is and B is CH₃, CF₃, CHF₂, CH₂F, halogen (Cl, F or Br) or CN, W is H, halogen or CN and Z' is O or COO. A ferroelectric liquid crystal device embodying the invention will now be described. Fig. 1 of the accompanying drawings is a sectional view showing an example of a liquid crystal device in which the ferroelectric liquid crystal composition of the invention is used. The example shown in Fig. 1 is a display device of the transmitting type which comprises insulating substrates 1 and 2, electrically conductive films 3 and 4, insulating films 5, orientation control layers 6, a sealant 7, the ferroelectric liquid crystal composition 8, and a polarizing plate 9. The insulating substrates 1 and 2 are light-transmitting substrates, which are usual glass substrates. The substrates 1 and 2 are respectively formed with transparent electrodes 3 and 4 of specified pattern, each in the form of a conductive film of InO₃, SnO₂ or ITO (Indium-Tin Oxide). The insulating film 5 is usually formed over the electrode but can be dispensed with as the case may be. The insulating film 5 is, for example, an inorganic thin film of SiO₂, SiN x or Al₂O₃, or an organic thin film of polyimide, photoresist resin or high polymer liquid crystal. The insulating film 5, when in the form of an inorganic thin film, can be formed by sputtering, CVD (Chemical Vapor Deposition), solution coating or other method. Further, the insulating film 5, when in the form of an organic thin film, can be prepared by applying a solution of an organic substance or of a precursor thereof by spinner coating, dip coating, screen printing, roll coating or other method, and curing the coating under predetermined conditions (as by heating or irradiation with light), or by vacuum evaporation, sputtering, CVD or LB (Langumuir-Blodgett) method. The orientation control layer 6 is formed over the insulating film 5. However, if the insulating film 5 is omitted, the orientation control layer 6 is formed directly over each of the conductive layers 3 and 4. The orientation control layer is in the form of an inorganic layer or an organic layer. The orientation control layer, when of the inorganic type, is usually formed by vacuum evaporation of silicon oxide. Rotary vacuum evaporation or a similar method can also be resorted to. When the orientation control layer is of the organic type, nylon, polyvinyl alcohol and polyimide are all usable, and the surface of the layer is usually rubbed. Further orientation can be effected with use of a high polymer liquid crystal or LB film or a magnetic field, or by spacer edge method. The layer can also be prepared from SiO₂ or SiN x by vacuum evaporation, sputtering or CVD, followed by rubbing of the surface. Subsequently, the two insulating substrates are placed over each other, and the liquid crystal composition 8 is injected into the space between them to obtain a ferroelectric liquid crystal device. Although the device described with reference to Fig. 1 is a switching device with one pixel, the ferroelectric liquid crystal composition of the invention can be used for display devices with a large-capacity matrix. In this case, the wires on the upper and lower substrates are combined into a matrix as shown in the schematic plan view of Fig. 2. The liquid crystal device of the matrix type can be driven by various drive methods previously proposed (see, for example, Wakita, Uemura, Ohnishi, Ohba, Furubayashi and Ohta, National Technical Report, 33 , 44(1987)). Synthesis of compounds of the formula (I) Preparation 1 (i) To a mixture of 5.55g of R-(-)-epichlorohydrin (optical purity: 99% or more), 2.46g of 4-(trans-4-n-pentylcyclo-hexyl)phenol of the formula: , and 0.04g of benzyltriethylammonium chloride was dropwise added a solution of 0.45g of sodium hydroxide in 15ml of water taking 20 minutes at 60°C under stirring. The reaction mixture was refluxed for an hour and then cooled to room temperature. Further the mixture was extracted twice with ether and washed once with a saturated aqueous solution of sodium chloride. The solvent was epoxypropyl 4-(trans-4-n-pentylcyclohexyl)phenyl ether (1.8g) of the formula. [α] 25 / D : +4.44° (C=1.36,CH₂Cl₂) NMR(CDCl₃)δ: 0.45-2.50(21H,m), 2.50-3.00 (2H,m), 3.15-3.50 (1H,m), 3.70-4.30 (2H,m), 6.79 (2H,d,J=9.0Hz), 7.09 (2H,d,J=9.0Hz) (ii) A 50% by weight suspension of sodium hydride in mineral oil (222mg) was washed twice with dry ether, to which 10ml of dry tetrahydrofuran was added. To the suspension was dropwise added 1.07g of dimethyl n-butylmalonate taking 5 minutes at 40°C under stirring. To the resultant was dropwise added 1.41g of (S)-2,3-epoxypropyl-4-(trans-4-n-pentylcyclohexyl) phenyl ether obtained in the above (i). The reaction mixture was refluxed for 20 hours under stirring and then cooled to room temperature. 4N-Hydrochloric acid was dropwise added to the reaction mixture to adjust it to pH1. The resultant was extracted twice with ether and washed once with saturated sodium chloride aqueous solution, and the solvent was evaporated under reduced pressure. The residue was purified by a silica gel column chromatography to obtain two γ-lactone derivatives, i.e.,a (2S,4S) isomer of the following formula (500mg) and the corresponding (2R,4S) isomer (440mg). The properties of the (2S, 4S)isomer are as follows: Phase transition temperature: [α] 23 / D : +33.45°(C=0.658, CH₂Cl₂) NMR(CDCl₃)δ : 0.88-1.98(30H,m), 2.38-2.67(3H,m), 4.07-4.13(2H,m), 4.67-4.73(1H,m), 6.83(2H,d,J=8.3Hz), 7.12 (2H,d,J=8.3Hz) IR: νmax(KBr) : 1762cm⁻¹ Elementary analysis for C₂₆H₄₀O₃ Calculated (%): C:77.95; H:10.07 Found (%): C:77.91; H:10.12 Preparation 2 (i) 2.50g of a phenol derivative of the formula: 4.25g of R-(-)-epichlorohydrin and 20mg of benzyl triethyl ammonium chloride (the latter two compounds were the same ones as used in Preparation 1) were dissolved in 3ml of dimethylformamide. To the solution was dropwise added 24% by weight sodium hydroxide aqueous solution (1.2 equivalents) at 60°C. The mixture was allowed to react for 40 minutes at the same temperature, then cooled to room temperature and extracted with ether. The solvent was evaporated under reduced pressure. The residue was purified by a silica gel column chromatography to obtain an S isomer of glycidyl ether (1.62g) of the following formula: mp : 90°C [α] 25 / D : +4.44° (C=1.01, CH₂Cl₂) NMR(CDCl₃)δ : 0.50-3.00(19H,m), 3.10-3.50(1H,m), 3.80-4.30(2H,m), 6.75-7.60(8H,m) (ii) 370mg of the S-isomer of glycidyl ether obtained in the preceding process (i), 442mg of diethyl n-propylmalonate, 134mg of potassium tert-butoxide and 3ml of tert-butyl alcohol were mixed and refluxed for 10 hours under stirring. The reaction mixture was allowed to cool to room temperature. After 4N-hydrochloric acid was added to the mixture to adjust it to pH1, the mixture was washed with water and methanol to give white crystals. The crystals were purified by a silica gel chromatography to give 240mg of a (2S,4S) isomer of the following formula and 140mg of the corresponding (2R,4S)isomer. The properties of the (2S,4S)isomer are as follows. Phase transition temperature : [α] 25 / D : +32.67° (C=1.081, CH₂Cl₂) NMR(CDCl₃)δ: 0.70-3.00(27H,m), 4.00-4.25(2H,m), 4.40-4.85(1H,m), 6.60-7.60(8H,m) IR νmax(KBr) : 1762cm⁻¹ (C=0) Preparations 3 to 5 The (2S,4S)isomers of γ-lactone derivatives of the following formulas were obtained in the same manner as that in Preparation 2. Preparation 6 (i) 1.01g of the compound of the formula: 2.01g of R-(-)-epichlorohydrin and 16mg of benzyl triethyl ammonium chloride (the latter two compounds were the same ones as used in Preparation 1) were mixed and heated to 70°C. To the mixture was dropwise added 650mg of 24% by weight sodium hydroxide aqueous solution. The resultant was stirred for 2 hours at 70°C, and cooled to room temperature. The mixture was extracted trice with chloroform, dried over anhydrous magnesium sulfate and distilled under reduced pressure to remove the solvent. The residue was recrystallized from hexane to obtain 380mg of an S isomer of glycidyl ether of the following formula: mp : 65°C [α] 25 / D : +1.90° (C=0.46, CH₂Cl₂) NMR(CDCl₃)δ: 0.6-3.0(19H,m), 3.2-3.6(1H,m), 3.9-4.5(2H,m), 6.99(2H,d,J=9.0Hz), 8.36(2H,d,J=9.0Hz), 8.55(2H,s) (ii) 320mg of the S-isomer of glycidyl ether obtained in the preceding process (i), 400mg of dimethyl n-hexylmalonate and 116mg of potassium tert-butoxide were dissolved in 3.5ml tert-butyl alcohol, followed by refluxing under stirring for 6 hours. The reaction mixture was treated in the same manner as that in Preparation 2 to obtain 270mg of a mixture of diastereomers of a γ-lactone derivative [(2S, 4S)/(2R, 4S) = 9/1]. Further, the mixture was purified to obtain 210mg of the (2S, 4S)isomer of the -lactone derivative of the following formula: NMR(CDCl₃)δ: 0.85-0.90(6H,m), 1.27-1.64(21H,m), 1.82-1.95(2H,m) 2.47-2.70(4H,m), 4.13-4.25(2H,m), 4.70-4.77(1H,m), 6.99(2H,d,J=9.1Hz), 8.37(2H,d,J=8.9Hz), 8.57(2H,s) IR(nujol) : 1778cm⁻¹ The compounds of the formula (I) which were obtained in the above Preparations 1 to 6 and have an optically active group were used as Compounds No. 110, No 210, No. 202, No. 204, No. 208 and No. 301 in the following examples. Preparation 7 (i) To a suspension of 2.82g of 4-(4-n-octylphenyl) phenol in 40ml of 1,2-dichloroethane were added under ice cooling, 6ml of a solution of boron trichloride (2M) in 1,2-dichloroethane, and then 0.82ml of methyl thiocyanate and 1.33g of aluminum chloride. The mixture was stirred at room temperature until the aluminum chloride is dissolved, further stirred for 3 hours at 80°C and cooled to room temperature. To the resulting mixture was added further 33ml of 4N-sodium hydroxide solution. The mixture was stirred for 30 minutes at 75 to 80°C. After cooling, the reaction mixture was washed with methylene chloride. The aqueous phase was adjusted to pH2 with 6N hydrochloric acid and extracted with ether. The extract was dried and evaporated under reduced pressure to obtain crude crystals. The crystals were purified by a silica gel column chromatography to give 2.03g of 4-(4-n-octylphenyl)-2-cyanophenol. (ii) To a solution of 1.9g of 4-(4-octylphenyl)2-cyanophenol obtained in the preceding (i) in 40ml of tert-butyl alcohol were added 832mg of potassium tert-butoxide, and then 2.5ml of R-(-)-epichlorohydrin and 100mg of 4-(N,N-dimethylamino)pyridine. The resultant was stirred for 2 days at room temperature and concentrated under reduced pressure. The residue to which water was added was extracted with ether. The extract was dried and distilled to obtain a crude product. The product was purified by a silica gel column chromatography to give 750mg of an S-isomer of glycidyl ether of the following formula. (iii) A mixture of 363mg of the S-isomer of glycidyl ether obtained in the preceding (ii), 303mg of diethyl n-propylmalonate, 157mg of potassium tertbutoxide and 10ml of tert-butyl alcohol was refluxed under stirring for 6 hours. The reaction mixture was allowed to cool to room temperature, adjusted to pH2 by adding water and then 4N-hydrochloric acid, and extracted with chloroform. An oil obtained from the extract was subjected to a silica gel column chromatography to afford 33mg of a (2S, 4S)isomer and 25mg of (2R, 4S)isomer of the lactone derivative of the following formulae. Phase transition temperature : [α]²³ : +31.83° (C=1.09, CH₂Cl₂) NMR(CDCl₃)δ: 0.88(3H,t,J=6.6Hz), 0.97(3H,t,J=7.1Hz), 1.25-1.32(10H,m), 1.41-1.58(3H,m), 1.59-1.66(2H,m), 1.85-2.07(2H,m), 2.55-2.78(4H,m), 4.31(2H,d,J=4.3Hz), 4.74-4.83(1H,m), 7.00-7.77(7H,m) IR (KBr): 2232cm⁻¹ ( C≡N) 1768cm⁻¹ (C=0) Phase transition temperature : [α] 23 / D : +18.26° (C=0.87, CH₂Cl₂) NMR(CDCl₃)δ: 0.88(3H,t,J=6.8Hz), 0.98(3H,t,J=7.1Hz), 1.25-1.27(12H,m), 1.45-1.56(2H,m), 1.60-1.62(1H,m), 1.85-1.95(1H,m), 2.12-2.22(3H,m), 3.05-3.10(1H,m), 4.19(1H,dd,J=3.3Hz, 10.3Hz), 4.37(1H,dd,J=3.3Hz, 10.3Hz), 4.84-4.89(1H,m), 7.00-7.77(7H,m) IR (KBr): 2232cm⁻¹ (νC≡N) 1768cm⁻¹ (νC=0) Preparation 8 (i) 25g of 4-Iodophenol was dissolved in 100ml of tert-butyl alcohol. To the solution was added 14.01g of potassium tert-butoxide, and the resultant was stirred for 4 hours at 40 to 45°C. To the solution was gradually added n-octylbromide (24.14g) under ice cooling and further the mixture was stirred for 3 hours at room temperature. The solvent was evaporated from the reaction mixture under reduced pressure. The residue to which water was added was extracted with chloroform to obtain a crude product, which was subjected to a silica gel column chromatography. The solvent was evaporated under reduced pressure from the eluate obtained by use of chloroform as an eluent to give 12g of the intended compound of 4-(n-octyloxy) iodobenzene. (ii) A mixture of 25g of 4-bromo-2-fluorophenol, 19g of potassium carbonate and 100ml of acetone was refluxed under stirring for 30 minutes. The reaction mixture was cooled, to which 17.40g of benzyl chloride were dropwise added taking 15 minutes. The resultant was refluxed under stirring for 7 hours and filtered. The filtrate was distilled to remove acetone. The residue to which water was added was extracted with chloroform. The extract was washed, dried and purified by a silica gel column chromatography using chloroform. The eluate was evaporated under reduced pressure to obtain 22.24g of the intended benzyl 4-bromo-2-fluorophenyl ether. (iii) Benzyl 4-(4′-n-octyloxyphenyl)-2-fluorophenyl ether (5.6g) was prepared from 14.06g of benzyl 4-bromo-2-fluorophenyl ether obtained in the above (ii), 1.22 of ribbon like magnesium and 11.61g of 4-n-octyloxyiodobenzene. (iv) 4-(4′-n-Octyloxyphenyl)-2-fluorophenol (3.71g) was prepared from a mixture of 5g of benzyl 4-(4′-n-octylphenyl)-2-fluorophenyl ether obtained in the above (ii), 2.5g of 5% Pd-C (water content : 52%) and 200ml of ethyl acetate. (v) S-Isomer of glycidyl ether of the following formula (2.17g) was prepared from 2.68g of 4-(4′-n-octyloxyphenyl)-2-fluorophenol obtained in the above (iv), 1.12g of potassium tert-butoxide, 3.3ml of R-(-)-epichlorohydrin, 50mg of 4-(N,N-dimethylamino)pyridine and 60ml of tert-butyl alcohol. (vi) A mixture of 650mg of the S-isomer of glycidyl ether obtained in the above (v), 529mg of diethyl n-propylmalonate, 274mg of potassium tert-butoxide and 20ml of tert-butyl alcohol was refluxed under stirring for 1.5 hours. The resultant was treated in the same manner as in Preparation 1 to obtain 310mg of a (2S, 4S)isomer and 102mg of a (2R, 4S)isomer of a γ-lactone derivative of the following formula. Phase transition temperature: [α] 21 / D : +38.35° (C=1.02, CH₂Cl₂) NMR(CDCl₃)δ: 0.89(3H,t,J=6.7Hz), 0.97(3H,t,J=7.1Hz), 1.2-1.6(13H,m), 1.74-2.0(4H,m), 2.45-2.6(1H,m), 2.6-2.75(1H,m), 3.99(2H,t,J=6.6Hz), 4.15-4.3(2H,m), 4.7-4.8(1H,m), 6.8-7.5(7H,m) IR (KBr): 1764cm⁻¹ (νC=0) MS (EI): m/z 456(M⁺) Phase transition temperature: [α] 21 / D : +21.51° (C=0.79, CH₂Cl₂) NMR(CDCl₃)δ: 0.89(3H,t,J=6.8Hz), 0.98(3H,t,J=7.1Hz), 1.2-1.55(13H,m), 1.75-1.9(3H,m), 2.05-2.2(1H,m), 2.45-2.56(1H,m), 2.85-2.95(1H,m), 3.99(2H,t,J=6.6Hz), 4.15(1H,dd,J=3.5, 10.3Hz), 4.26(1H,dd,J=3.5, 10.3Hz), 4.75-4.85(1H,m), 6.9-7.4(7H,m) IR (KBr): 1770cm-1 (νC=0) MS (EI): m/z 456(M⁺) Synthesis of compounds of the formula (II′) Preparation 9 (i) To a mixture of 50% sodium hydroxide (40g), (S)-epichlorohydrin (24g) and tetrabutyl ammonium hydrogen sulfate (400mg) is added dropwise n-hexanol (6ml) while cooling at 20 - 25°C. After stirring the reaction mixture at the same temperature for additional 3 hours, water is added to the mixture and the product is extracted with ether. The extract is purified by distillation under reduced pressure to give (S)-n-hexylglycidyl ether (3.35g). (ii) To a solution of diisopropylamine (505mg) in tetrahydrofuran (10ml) cooled at -78°C is added dropwise a 15% solution of n-butyllithium in hexane (3ml) and the temperature is raised gradually to 0°C and the mixture is stirred for 30 minutes. To this reaction solution is added dropwise a solution of 4-(4′-n-heptyl)-biphenylacetic acid (682mg) in tetrahydrofuran (3ml) and the mixture is stirred for 1 hour. The reaction solution is cooled to -78°C and a solution of (S)-n-hexylglycidyl ether (445mg) in tetrahydrofuran (1ml) is added dropwise. After the temperature of the reaction solution is gradually raised to room temperature and the reaction solution is stirred for 6 hours, water is added and the mixture is acidified with hydrochloric acid, followed by extraction of the product with chloroform. To the extract is added dry benzene and a catalytic amount of sulfuric acid and the mixture is stirred with heating for 6 hours while draining benzene in portions. After cooling, the benzene is distilled off under reduced pressure and the residue is purified by silica gel column chromatography to give γ-lactone derivatives (2S, 4R) (401mg) and (2R, 4R) (465mg) of the following formulas, respectively. (2S, 4R) isomer: Phase transition temperature: [α] 22 / D : -2.17° (C=1.07, CH₂CL₂) NMR(CDCl₃)δ: 0.86-0.91(6H,m), 1.29-1.61(18H,m), 2.28-2.42(1H,m), 2.61-2.76(3H,m), 3.52(2H,t,J=6.60Hz), 3.61-3.75(2H,m), 3.92(1H,dd,J=9.16Hz, 12.09Hz), 4.62-4.67(1H,m), 7.25(2H,d,J=8.06Hz), 7.35 (2H,d,J=8.42Hz), 7.48(2H,d,J=8.42Hz), 7.57(2H,d,J=8.06Hz) (2R, 4R) isomer: Phase transition temperature: [α] 22 / D : -37.95° (C=1.003, CH₂Cl₂) NMR(CDCl₃)δ: 0.86-0.90(6H,m), 1.29-1.60(18H,m), 2.45-2.57(1H,m), 2.61-2.74(3H,m), 3.51(2H,t,J=6.68Hz), 3.60-3.75(2H,m), 4.09(1H,t,J=9.35Hz), 4.74-4.78(1H,m), 7.24(2H,d,J=8.06Hz), 7.33(2H,d,J=8.43Hz), 7.48(2H,d,J=8.43Hz), 7.57(2H,d,J=8.06Hz) Example 1 A nematic liquid crystal composition (1) shown in Table 9 was prepared. A Cano type cell in the shape of wedge was made by conducting a horizontal orientation treatment of a pair of glass substrates and facing their orientation layers in the manner that their rubbed directions are reverse. The thickness of each of the parts of the cell was measured. Each of the compounds shown in Table 10 in an amount of about 1% by weight was added to the liquid crystal composition (1) obtain a nematic liquid crystal compositions, which was injected to the above Cano type cell. This cell was placed at the position between 2 sheets of polarizing plates arranged in perpendicular with respect to their polarizing directions and the disclination line was observed. The helical pitch of the injected nematic liquid crystal composition was determined on the basis of the thickness of the cell at the position where a disclination line appeared. The 1/pi of each of the compounds was evaluated from the helical pitch value, using the equation (X). The results are shown in Table 10. Example 2 Each of the compounds shown in Table 11 in an amount of 30% by weight was added to the liquid crystal composition (1) to obtain a liquid crystal composition showing nematic phase. The helical pitch directions in nematic phase of the compounds in Table 11 are well known. On the other hand, each of the compounds shown in Table 10 in an amount of 1 to 30% by weight was also added to the liquid crystal composition (1) to obtain compositions showing nematic phase. A nematic liquid crystal composition prepared from a compound in Table 11 was brought in contact on a slide with that prepared from a compound in Table 10 and an area where both the compositions are in contact was observed by a polarization microscope. The direction of the helical pitch induced in a compound in Table 10 in nematic phase was determined by observing whether a schlieren structure appears or not, which occurs in the contacting area only when the helical pitch is very large. Example 3 The liquid crystal composition (2) shown in Table 12 was prepared, which is a nonchiral smectic C liquid crystal composition containing no optically active compound. Each of the compounds shown in Table 10 in an amount of 2% by weight was added to the liquid crystal composition (2) to obtain a chiral smectic C liquid crystal composition. Two glass substrates each was laminated by ITO film electrode, SiO₂ insulating film and PVA film. The upper PVA film was rubbed. These two glass substrates were set to make a cell leaving 2µm clearance between these substrates. The above chiral smectic C liquid crystal composition was injected to the above cell. This cell was placed at the position between 2 sheets of polarizers arranged in perpendicular with respect to their polarizing directions. When voltage was applied to the cell, a change was observed in the intensity of the transmitted light. The direction of the spontaneous polarization (Ps) induced in smectic C phase of each of the compounds was determined from the relationship of the direction of the applied voltage with the response direction of liquid crystal molecules found on the basis of the change of the intensity of the transmitted light. The results are shown in Table 12. Example 4 Ferroelectric liquid crystal compositions 30 to 35 were prepared from the compounds shown in Tables 10 and 13. These compositions were prepared so as to have a phase sequence of a smectic C phase, smectic A phase and nematic phase, and 20µm of a helical pitch in nematic phase. The values of the phase change temperature and the helical pitch in nematic phase obtained by calculating using the equation (X) are shown in Table 15. A Cano type cell in the shape of wedge similar to that used in Example 1 was prepared except that the thickness in the thicker portion of the cell is 10µm. Each of the compositions 30 to 35 was injected to the above cell. No disclination line was observed in the above cells, which demonstrated that the helical pitches in nematic phase of these compositions are 20µm or more. Example 5 Two glass substrates each was laminated by ITO film electrode, SiO₂ insulating film and PVA film. The upper PVA film was rubbed. These two glass substrates were set to make a cell facing their orientation films each to others in the same rubbing direction and leaving 2µm clearance between these films. Each of the ferroelectric liquid crystal compositions prepared in Example 4 was injected to the above cell. The cell was then heated at a temperature to change the liquid crystal composition into an isotropic liquid and then cooled to room temperature at the rate of 1°C/min to obtain a ferroelectric liquid crystal element having good orientation. The above element was placed at the position between two sheets of polarizers arranged in perpendicular with respect to their polarizing directions. A voltage was applied to the cell and the characteristics were evaluated.

Claims: A ferroelectric liquid crystal device comprising a pair of substrates (1,2) each having means (3,4) for applying a voltage thereto, an orientation control layer (6) formed on at least one of the substrates, and a layer of ferroelectric liquid crystal composition (8) formed between the substrates, characterized in that the ferroelectric liquid crystal composition comprises at least one compound (a) selected from optically active compounds of the formula (II): in which each of A₁, A₂ and A₃ is a group containing a 6-membered ring which may be substituted, X is -0-, -C00-, -OCO- or a single bond, each of Y₁ and Y₂ is -COO-, -OCO-, -OCH₂-, -CH₂O-, -CH₂CH₂-, -CH=CH-, -C≡C-or a single bond, each of R₁ and R₂ is straight-chain or branched-chain C₁₋₁₅ alkyl, and each of p, q and r is 0 or 1, and optically active compounds of the formula (II'): in which R₉ is a straight-chain or branched-chain C₁₋₁₅ aliphatic hydrocarbon group which may include an intervening oxygen atom, R₁₀ is a straight-chain or branched-chain C₁₋₁₅ alkyl group, A₄ is a phenylene group or cyclohexane group, and each of m and n is 0 or 1, and at least one compound (b) which in the nematic phase has a reverse induced helical pitch, the liquid crystal composition exhibiting at least a smectic C phase, a smectic A phase and a nematic phase having a helical pitch of at least 20 µm. A device according to claim 1, wherein the group R₂-X-(A₁-Y₁) p -(A₂-Y₂) q -(A₃) r is selected from in which R₂ and p have the meanings specified in claim 1, n is 0 or 1, and Z' is -CN or F. A device according to claim 1 or claim 2, wherein R₁ is a straight-chain or branched-chain C₁₋₁₂ alkyl and R₂ is a straight-chain or branched-chain C₅₋₁₁ alkyl. A device according to any one of claims 1 to 3, wherein the compound (b) is a compound having an optically active group of the formula (III): in which Z is -C00-, -0C0-, -0- or -C0-, B is CH₃, CN, halogen, CH₂F, CHF₂ or CF₃, and R is a straight-chain or branched-chain C₁₋₁₅ alkyl. A device according to any one of claims 1 to 3, wherein the compound (b) is of the formula: in which R' and R'' are the same of different and each is a straight-chain or branched-chain C₁₋₁₅ alkyl or alkoxy group, R''' is straight-chain or branched-chain C₁₋₁₅ alkyl or alkoxy group or CH₂COOC₂H₅, B is CH₃, CN, CF₃, CHF₂, CH₂F or a halogen (C1, F or Br), Y is -COO-, -OCO-, -OCH₂-or-CH₂O-, and each of n and m is 0 or 1. A device according to any one of claims 1 to 3, wherein the compound (b) is of the formula (II) or (II').

Inventors: FUNADA FUMIAKI, KITAMURA TOHRU, KODEN MITSUHIRO, KURATATE TOMOAKI, SAKAGUCHI KAZUHIKO, SHIOMI YUTAKA, TAKEHIRA YOSHIKAZU, FUNADA, FUMIAKI, KITAMURA, TOHRU, KODEN, MITSUHIRO, KURATATE, TOMOAKI, SAKAGUCHI, KAZUHIKO, SHIOMI, YUTAKA, TAKEHIRA, YOSHIKAZU
Applicants: DAISO CO LTD, SHARP KK, DAISO CO., LTD., SHARP KABUSHIKI KAISHA
Application year: 1990
Main classification: C09K19
IPC codes: C07D315, C07D307, C07D405, C09K19, C07D239