Polymeric liquid-crystalline compound, liquid-crystal composition containing it, and liquid-crystal device

Abstract: Provided is a polymeric liquid-crystalline compound having in its repeating unit a moiety represented by the following formula (M) X₁-A-X₂-B (M) wherein A represents a bicyclic mesogen; B represents a flexible group represented by the formula wherein X represents a hydrogen atom or a methyl group and Y represents a hydrogen atom or a methyl group, provided that X is not the same as Y, k is 0 or 1, and m1 is 1 to 18, or wherein X represents a hydrogen atom or a methyl group and Y represents a hydrogen atom or a methyl group, provided that X is not the same as Y, k is 0 or 1, m2 is 2 to 10 and m3 is 2 to 5; and X₁ and X₂ each represent a group containing any one of an ester bond, an ether bond and a carbonate bond, and may be the same or different from each other.

Description: The present invention relates to a novel polymeric liquid-crystalline compound having an optically active group in its polymer main chain, a liquid-crystal composition comprising the polymeric liquid-crystalline compound and a liquid-crystal device making use of a film comprising said compound. Polymeric liquid-crystal materials have recently attracted notices as high-function materials. This is considered due to the fact that polymeric liquid crystals have the following superior characteristic features. (1) They can be readily formed into thin films, and make it possible for liquid-crystal devices to have a large area, which has been difficult in low-molecular liquid crystals. (2) Application of aligning treatment such as stretching can give a good state of alignment. (3) A liquid-crystal state of polymers can be retained even at a temperature of not higher than the glass transition temperature, and hence the memory performance can be greatly improved, compared with the case in which low-molecular liquid crystals are used. A problem arising when polymeric liquid crystals are put into practical use has been said to be a slow speed of response to an electric field. The speed of response to an electric field, however, can be considered to be greatly improved by the use of a ferroelectric polymeric liquid crystal having a spontaneous polarization as in low-molecular liquid crystals. In order for a polymeric liquid crystal to exhibit a ferroelectricity, an optically active group must be introduced into a flexible spacer (a flexible chain). With regard to what are called side-chain type polymeric liquid crystals having an acrylic or methacrylic main chain or the like, a report has already been made on ferroelectric polymeric liquid crystals having various molecular structures (see, for example, Japanese Patent Applications Laid-Open No. 63-72784, No. 63-99204 and No. 63-161005). On the other hand, main-chain type polymeric liquid crystals are superior in strength when they are formed into films, and also their molecular chains can be readily aligned by stretching or the like, compared with the side-chain type polymeric liquid crystal. As a result, they can be superior in view of, e.g., the fact that the films can be readily made to have large areas even when a low-molecular liquid crystal is contained. Such a main-chain type ferroelectric polymeric liquid crystal having a bicyclic biphenyl group as a mesogen and an optically active group in the main chain has been reported in Collections of Lecture Drafts for The 14th Liquid Crystal Forum, pp.56-57, September 1988, Japanese Patent Application Laid-Open No.64-65124. What is disclosed in this publication, however, is a monotropic polymeric liquid crystal that renders a chiral smectic phase only when temperature is lowered, and it has been difficult for a stable liquid-crystal phase to be exhibited. In addition, because of use of a specific optically active group, this liquid crystal has a narrow range of selection in view of the control of temperature characteristics, optical characteristics and electrical characteristics and also has not been well satisfactory in view of, e.g., its electrical characteristics. As a result of intensive research carried out on the basis of such conventional techniques, the present inventors have discovered a novel ferroelectric polymeric liquid-crystalline compound, and thus have accomplished the present invention. An object of the present invention is to provide a novel polymeric liquid-crystalline compound or copolymerized polymeric liquid-crystalline compound capable of rendering a broad chiral smectic phase (an Sm* phase) and also capable of readily forming a thin film or being formed into a film, and a liquid-crystal composition containing such polymeric liquid-crystalline compounds and other low-molecular liquid crystal or the like. Another object of the present invention is to provide a liquid-crystal device making use of the above polymeric liquid-crystalline compound or copolymerized polymeric liquid-crystalline compound, or a liquid-crystal composition comprising these polymeric liquid-crystalline compounds and other polymeric compound.(including a polymeric liquid crystal) or low-molecular compound (including a low-molecular liquid crystal), and thereby making it possible to readily achieve large-area display, to exhibit a good switching effect and to be utilized as a device in which various electro-optic effects are applied. The present invention provides a polymeric liquid-crystalline compound as specified in claim 1. Thus, the present invention provides a polymeric liquid-crystalline compound comprising a main chain having a repeating unit represented by the following formula (Ia). wherein are each selected from any one of provided that at least one of represents Y 1 represents any one of a single bond, -CH=CH-, -C≡C, -N=N-, -CH=N-, -CH 2 CH 2 - and -CH 2 O-; B represents a flexible group represented by the formula wherein X represents a hydrogen atom or a methyl group and Y represents a hydrogen atom or a methyl group, provided that X is not the same as Y, k is 0 or 1, and ml is 1 to 18, or wherein X represents a hydrogen atom or a methyl group and Y represents a hydrogen atom or a methyl group, provided that X is not the same as Y, k is 0 or 1, m2 is 2 to 10 and m3 is 2 to 5; X 1 and X 2 each represent a group containing any one of an ester bond, an ether bond and a carbonate bond, and may be the same or different from each other; and n represents 5 to 1,000. Similarly, the present invention also provides a liquid-crystal composition comprising the compound of the formula (Ia), and a liquid-crystal device comprising such a liquid-crystal composition. The present invention further provides a copolymerized polymeric liquid-crystalline compound comprising a main chain having a repeating unit represented by the formula (IIa) as specified in claim 1, a liquid-crystal composition comprising such a compound, and a liquid-crystal device comprising such a liquid-crystal composition. The present invention still further provides a copolymerized polymeric liquid-crystalline compound comprising a main chain having a repeating unit represented by the formula (IIIa) as specified in claim 1, a liquid-crystal composition comprising such a compound, and a liquid-crystal device comprising such a liquid-crystal composition. The invention is advantageously developed by the features mentioned in the dependent claims. Fig. 1 is a cross-sectional view of a liquid-crystal device used in Example 4. Fig. 2 is a oblique view of a liquid-crystal device provided with a polarizing plate, used in Example 4. Fig. 3 is a view to illustrate Example 9. Fig. 4 is a plane view of a liquid-crystal device in which transparent electrodes are disposed in the form of a matrix. Figs. 5 to 7 are cross-sectional views of liquid-crystal devices. Fig. 8 illustrates the constitution of a display apparatus. Fig. 9 illustrates the constitution of a recording apparatus. Fig. 10 is a view to illustrate Example 10. The present invention will be described below in detail. The bicyclic mesogen group used in the present invention gives a lower liquid crystal temperature range and hence can be used with ease from the viewpoint of practical use, compared with polycyclic types of three or more ring structures, when the formation of a liquid crystal phase is taken into account. In addition, since the above polycyclic types tend to result in a complicated liquid-crystal phase transition pattern, the molecular structure can be controlled relatively with difficulty in order for a liquid crystal to render a chiral smectic phase. The bicyclic type is preferred also in this respect. X 1 and X 2 each represent a group containing any one of an ester bond, an ether bond and a carbonate bond, and may be the same or different from each other. Of these, the polyester represented by the following formula (IV) is particularly preferred since it can readily give a high-molecular weight material and can have a chiral smectic phase with ease. As specified in claim 1 the group B is represented by wherein X represents a hydrogen atom or a methyl group and Y represents a hydrogen atom or a methyl group, provided that X is not the same as Y, k is 0 or 1, and ml is 1 to 18, or wherein X represents a hydrogen atom or a methyl group and Y represents a hydrogen atom or a methyl group, provided that X is not the same as Y, k is 0 or 1, m2 is 2 to 10 and m3 is 2 to 5, and is a flexible group derived from an optically active lactic acid. Preferred examples are as shown below: (The asterisk * represents an optically active group). These groups can be derived from diols. Methods of synthesizing these are described in Japanese Patent Application Laid-Open No. 1-93553. The optically active flexible group used in the present invention comprises an asymmetric carbon atom to which an oxygen atom having a polarity is directly bonded, hence a large spontaneous polarization. This is preferable in view of response speed. The optically active flexible group is also rich in flexibility because of its ether bond, hence a high liquid crystallinity that is, bringing about a broad temperature range for the formation of a liquid crystal phase. The letter symbol C represents a mesogen group as defined in claim 1. The letter symbol D represents a group represented by the same formula as B but with a different molecular structure or represents a straight-chain or branched alkylene. The letter symbol E represents a flexible group containing no optically active group. A flexible group refers to a skeletal moiety, positioned between mesogen groups, from which the bonding group bonded to the mesogen groups is excluded and which is a straight chain or branched chain group containing no cyclic group. Preferred examples of the group D other than or different from the group B are straight-chain alkylene groups as exemplified by and and alkyl groups having a branch, as exemplified by the following: The above examples of the alkyl group having a branch may also apply to the above group E. In the present invention, the polymeric liquid-crystalline compound into which the ester bond having a repeating unit represented by the formula (IIa) has been introduced can be synthesized by molten polymerization or solution polymerization which is a usual polycondensation reaction. In the molten polymerization, for example, the compound is synthesized by ester exchange reaction between a dialkyl ester of dicarboxylic acid and a diol containing an optically active group. In order to smoothly carry out the reaction, it is preferred to add a known esterification catalyst as exemplified by an organic titanium compound such as a tetra-n-propyl ester, a tetra-isopropyl ester or a tetra-n-butyl ester of titanic acid, an organic tin compound, antimony trioxide, or an acetate of lead, zinc, manganese, calcium or the like. In the solution polymerization, for example, a condensation reaction by dehydrohalogenation between an acid halide containing a mesogen group and a diol containing an optically active group may be used. In the present invention, in order to control temperature characteristics, optical characteristics, electrical characteristics and so forth, it is also preferred to use as the polymeric liquid-crystalline compound a combination of two or more of the group or B in the formula (Ia). The polymeric liquid-crystalline compound or copolymerized polymeric liquid-crystalline compound obtained through the present reaction may be purified by a usual method such as reprecipitation or filtration, and then used as it is or optionally after purified by subjecting to a chromatography. The polymeric liquid-crystalline compound or copolymerized polymeric liquid-crystalline compound of the present invention may have a degree of polymerization of from 5 to 1,000; furthermore it shows a weight average molecular weight (Mw) of from 2,000 to 500,000, and preferably from 5,000 to 100,000. Examples of the polymeric liquid-crystalline compound or copolymerized polymeric liquid-crystalline compound of the present invention having the repeating unit represented by the formulas (Ia), (IIa) and (IIIa) are given below, which, however, are not limited to these. (m1 = 1 to 18, m3 = 2 to 5, x+y = 1, n = 5 to 1,000). Of these, particularly preferred is a compound that renders a chiral smectic phase, like the copolymerized polymeric liquid-crystalline compound of a polymeric liquid crystal comprising a homopolymer that renders the smectic-C phase and a polymeric liquid crystal having a repeating unit containing an optically active group (for example, Nos. 79, 80,...). In the copolymerized polymeric liquid-crystalline compound of the present invention, the flexible chain represented by B is held in an amount of not less than 1 mol %, and preferably not less than 10 mol %, based on the total flexible chains. An amount less than 1 mol % may result in a difficulty for the compound to render a chiral smectic phase. Referring next to the liquid-crystal composition of the present invention, it comprises the polymeric liquid-crystalline compound and/or the copolymerized polymeric liquid-crystalline compound, described above, and, for example, a low-molecular liquid crystal. There are no particular limitations on the low-molecular liquid crystal so long as it has a good compatibility with the polymeric liquid-crystalline compound and copolymerized polymeric liquid-crystalline compound. The low-molecular liquid crystal may be used alone, or a mixture of two or more kinds may be used. Preferred examples thereof are optically active low-molecular liquid crystals as shown by the following formulas (1) to (15) or low-molecular liquid crystals not optically active as shown by the following formulas (16) to (35). In view of response performance, it is preferred to use the former. In the following, "Cryst." refers to "Crystal phase", "Iso" to "Isotropic phase" and "Cholest." to "Cholesteric phase". Examples of liquid crystal compounds that render non-chiral smectic phase: Into the liquid-crystal composition of the present invention, other low-molecular compound, polymeric compound and polymeric liquid-crystalline compound can also be mixed. Namely, those which do not cause the chiral smectic phase to disappear and have good compatibility may be appropriately selected and used. For example, polymeric liquid-crystalline compounds that can be additionally used in combination may include the following: In the following formulas (36) to (48), 15 ≧ p ≧ 1. In the liquid-crystal-composition containing the polymeric liquid-crystalline compound or copolymerized polymeric liquid-crystalline compound, the polymeric liquid-crystalline compound or copolymerized polymeric liquid-crystalline compound should be contained in an amount of not less than 5 % by weight, and preferably not less than 10 % by weight. An amount less than 5 % by weight may result in a lowering of the alignment stability to pressure, thermal stimulation, etc., which is attributable to the anisotropy of the polymeric liquid-crystalline compound. When the composition is used in the form of a film, the polymeric liquid-crystalline compound should be contained in an amount of not less than 30 % by weight, and preferably not less than 50 % by weight, in view of form retention. From the requirement for device designing, it is preferred to use the above polymeric liquid-crystalline compound and copolymerized polymeric liquid-crystalline compound together with other polymers, polymeric liquid crystals, low-molecular compounds or low-molecular liquid crystals, in combination of their respectively plural kinds, so that the temperature characteristics, optical characteristics, electrical characteristics, etc. can be readily controlled. To the liquid-crystal composition according to the present invention, it is possible to add coloring matters, light stabilizers, light absorbents, antioxidants, plasticizers, etc. Referring next to the liquid-crystal device of the present invention, it comprises a substrate and, provided thereon, a film comprising the polymeric liquid-crystalline compound or copolymerized polymeric liquid-crystalline compound as previously described, or the liquid-crystal composition containing these polymeric liquid-crystalline compounds. As a specific constitution of the liquid-crystal device of the present invention, the polymeric liquid-crystalline compound, the copolymerized polymeric liquid-crystalline compound or the polymeric liquid-crystal composition may be formed into a thin film from its molten state and the film thus formed may be inserted and adhered between substrates provided with electrodes. When the film is adhered, a suitable spacer may be provided between the film comprising the polymeric liquid-crystalline compound, copolymerized polymeric liquid-crystallinecompound or polymeric liquid-crystal composition and the electrodes so that the insulation between the electrodes can be kept. Alternatively, without the substrates, electrodes may be directly provided on the film comprising the polymeric liquid-crystalline compound, copolymerized polymeric liquid-crystalline compound or polymeric liquid-crystal composition. In this embodiment, a flexible liquid-crystal device in the form of film can be obtained. The film comprising the polymeric liquid-crystalline compound, copolymerized polymeric liquid-crystalline compound or polymeric liquid-crystal composition can also be formed by dissolving the polymeric liquid-crystalline compound, copolymerized polymeric liquid-crystalline compound or polymeric liquid-crystal composition in a solvent such as dichloroethane, THF, cyclohexanone or chloroform to bring it into a solution and then into a film. More specifically, as a method of forming the film, it is possible to apply methods for making usual plastic films, i.e., melt extrusion, casting from solution, calendering or spin coating. According to the present invention, when a liquid crystal phase is formed in the liquid-crystal device, the above polymeric liquid-crystalline compound, copolymerized polymeric liquid-crystalline compound or polymeric liquid-crystal composition may be formed into a film and then the film may be subjected to a stretching alignment treatment, so that liquid-crystal molecules can be aligned in a high performance. As methods for the stretching alignment treatment, monoaxial stretching or the like can be applied. Alternatively, a plastic substrate serving as a support may be coated with a solution comprising the polymeric liquid-crystalline compound, copolymerized polymeric liquid-crystalline compound or polymeric liquid-crystal composition to laminate a film comprising the polymeric liquid-crystalline compound, copolymerized polymeric liquid-crystalline compound or polymeric liquid-crystal composition, and then the resulting laminate as a whole may be stretched. Still alternatively, a cell in which a liquid-crystal film is held between a pair of substrates may be formed and then the film may be aligned by stretching. The liquid-crystal device of the present invention may also comprise a pair of substrates having been subjected to alignment treatment, between which the polymeric liquid-crystalline compound, copolymerized polymeric liquid-crystalline compound or polymeric liquid-crystal composition is sealed in a molten state kept at a temperature higher than the isotropic phase transition temperature. As the alignment treatment for the substrates, it is possible to apply a method in which an organic thin film made of polyimide, polyamide, polyvinyl alcohol, polysiloxane, polyimide amide or the like is monoaxially or biaxially aligned by rubbing, a method in which an inorganic film made of SiO 2 , ZnS, MgO or the like is monoaxially or biaxially aligned by rubbing, or a method to use a surface obtained by oblique vacuum deposition of an inorganic compound such as SiO 2 , SiO, MgO or MgF 2 . In the embodiment in which the polymeric liquid-crystalline compound, copolymerized polymeric liquid-crystalline compound or polymeric liquid-crystal composition is held between a pair of substrates, a good alignment can also be obtained by shearing, which is carried out by minutely slipping the upper and lower substrates. The constitution of the liquid-crystal device of the present invention may vary depending on various uses. An example of the construction commonly used will be described herein. Fig. 1 is a cross-sectional view of a liquid-crystal device, Fig. 2 is a oblique view of a liquid-crystal device provided with a polarizing plate, Fig. 4 is a plane view of a liquid-crystal device in which transparent electrodes are disposed in the form of a matrix, and Figs. 5 to 7 are cross-sectional views of liquid-crystal devices according to other embodiments. In the drawings, reference numerals 1, 1' denote substrates; 2, 2', transparent electrodes; 3, 3' aligning layers; 4, an adhesive layer; 5, a polymeric liquid-crystal layer; 6, 6', polarizing plates; 7, 7', polarizing directions; 8, a liquid-crystal device; 9, a polyester film; 10, a reflective layer serving also as an electrode; and 11, an Al reflective layer. Taking an example of the liquid-crystal device in the form of film from among the above respective liquid-crystal devices, Fig. 8 illustrates the construction of a display apparatus in which such a liquid-crystal device is used as a display device. Fig. 9 illustrates the construction of a recording apparatus in which each of the above liquid-crystal devices is used as a recording device. In these drawings, reference numerals 12, 12' denote rollers; 13, a display area; 14, a temperature sensor; 15, a flat heater; 16, a erasing means; 17, a light source; 18, a Fresnel lens; 19, a thermal head (a writing means); 20, a semiconductor laser; 21, a polarizer; 22, a beam splitter; 23, an analyzer; 24, a moving stage; and 25, a light-intensity detector. The present invention will be described below in greater detail by giving Examples. Example 1 To 3.0 g of diethyl-4,4'-biphenyl dicarboxylate and 2.6 g of a diol represented by the following formula, 0.0015 g of tetra-isopropyl titanate was added. Under a nitrogen gas atmosphere, the temperature was raised to 150°C by heating and reaction was carried out for 1 hour with stirring. Subsequently, the reaction was similarly carried out at 180°C for 2 hours, and thereafter the temperature was raised to 230°C in 1 hour. The reaction system was made to reduced pressure, under which the reaction was further carried out for 5 hours. Polymerization was completed at a degree of vacuum of 0.5 mmHg. The polymer obtained from the reaction was dissolved in chloroform, and thereafter the solution was put in a 20-fold amount of methanol. The precipitate formed was filtered, followed by drying under a reduced pressure to give 2.5 g of a milk-white polymer (a). Polymer (a): DSC measurement and polarizing-microscopic observation revealed that the liquid-crystal phase transition points were as follows. (Cryst.: Crystal phase; SmC*: Chiral smectic C phase; SmA: Smectic A phase; Iso.: Isotropic phase) The polymer (a) was subjected to GPC (gel permeation chromatography) to measure its molecular weight distribution using a chloroform solution. As a result, the following was found: Mn = 1.2 x 10 4 Mw = 3.0 x 10 4 The specific rotation was [α] 25 / D = +4.5° (C = 1.05; solvent: chloroform). NMR data (δppm(TMS)): 1.2 (d, 3H, methine) 3.7 -3.85 (m, 2H, methylene) 4.5 (m, 6H, methylene) 7.65 (d, 4H, phenylene) 8.1 (d, 4H, phenylene) Example 2 Example 1 was repeated except that the diol used therein was replaced with a compound (3.5 g) represented by the following formula, to give 2.8 g of a milk-white polymer (b). Polymer (b): DSC measurement and polarizing-microscopic observation revealed that the liquid-crystal phase transition points were as follows: (gl.: glass phase) The molecular weight distribution and specific rotation of the polymer (b) were measured to obtain the following results: Mn = 1.3 x 10 4 Mw = 4.0 x 10 4 [α ] 25 D = +4.0 (C = 1.02; solvent: chloroform) NMR data (δppm(TMS)): 1.2 (d, H, methine) 4.5 (m, 1H, methylene) 7.7 (d, 4H, phenylene) 8.1 (d, 4H, phenylene) Example 3 Using the polymeric liquid-crystalline compounds (a) and (b) obtained in Examples 1 and 2, films were obtained, respectively, in the following way. The above compounds were each made into a 20 wt.% solution of dichloroethane, and casted on a glass plate, followed by drying to form films, which were then monoaxially stretched by 200 % at 100°C to give a monoaxially oriented films of 10 µm thick each. The resulting stretched films were each pressure-bonded between a pair of glass substrates each provided thereon with a flat ITO electrode [thickness: 130 nm (1,300 Å)] on which a polyimide aligning film of 60 nm (600 Å) thick having been subjected to rubbing was formed. The-devices were gradually cooled from Isotropic phase to 130°C, 63°C, respectively (SmC* phase), and thereafter a voltage of ±20 V/µm was applied in the state of the SmC* phase. As a result, there were shown responses at a speed of about 80 msec in the film of (a) and about 90 msec in the film of (b). Example 4 A test was carried out to examine the compatibility between the polymeric liquid-crystalline compound (a) obtained in Example 1 and the low-molecular liquid crystal (14) previously shown. As a result, the same phase as that of the low-molecular liquid crystal (14) was recognized over a wide compositional range. Table 1 shows phase transition temperatures of polymeric liquid-crystal compositions of various blend systems between the compound (a) and the liquid crystal (14). Example 5 The polymeric liquid-crystal compositions (compositional ratio of (a)/(14): 1/4, 1/1) shown in Example 4 were each sealed, as they were in the state of an isotropic phase, into a liquid-crystal cell as shown in Fig. 1, comprising a pair of glass substrates 1 and 1' respectively provided thereon with flat ITO electrodes 2 and 2' [thickness: 130 nm (1,300 Å)] on which polyimide aligning films 3 and 3' of 60 nm (600 Å) thick having been subjected to rubbing were respectively formed, which substrates were adhered through an adhesive layer 4 in the manner that the thickness of a liquid-crystal layer between the substrates was set to be 10 µm. Under observation with a polarizing microscope, an electric field of ±20 V/µm was applied to the device where the liquid crystal rendered the SmC* phase. As a result, it was observed that the molecules were inverted in response to the electric field. Table 2 shows the speed of response to the electric field. . As shown in Fig. 2, the above liquid-crystal device, designated by reference numeral 8, was inserted between two polarizing plates 6 and 6' crossing at right angles and then an electric field was applied in the same manner as in the above. As a result, it was observed that light and dark changes in transmitted light were produced in response to the electric field. In Fig. 2, the arrows denoted as 7 and 7' indicate the polarizing directions of the polarizing plates 6 and 6', respectively. Compositional ratio (a)/(14) Temperature (°C) Response speed 1/4 100 900 µs " 110 680 µs " 130 600 µs 1/1 100 2.5 ms " 130 1.8 ms Example 6 Example 1 was repeated except that the diol used therein was replaced with two kinds of compounds represented by the following formulas, which were used in the compositional ratios as shown in Table 3. Copolymers (c) were thus obtained. Copolymer (c): Liquid-crystal devices were prepared in the same manner as in Example 3 from the copolymers having the respective compositional ratios (Examples 6-1 and 6-2). A voltage of ±20 V/µm was applied to the devices where the liquid crystal rendered the chiral smectic C phase, and response speeds were observed to obtain the results as shown in Table 3. Comparative Example 1 Example 6 was repeated but using a polymer of x = 0, to obtain the results shown in Table 3. x (mol%) y (mol%) Response speed (msec.) Mn / Mw Example: 6-1 75 20 150 1.1x10 4 /2.2x10 4 6-2 50 50 80 8.5x10 3 /1.8x10 4 Comparative Example: 1 0 100 No response 1.4x10 4 /4.3x10 4 Example 7 A test was carried out to examine the compatibility between the copolymer (c)-1 obtained in Example 6-1 and the low-molecular liquid crystal (14). As a result, the same phase as that of the low-molecular liquid crystal (14) was recognized over a wide compositional range. Table 4 shows phase transition temperatures of polymeric liquid-crystal compositions of various blend systems between the copolymer (c)-1 and the liquid crystal (14). The polymeric liquid-crystal compositions (compositional ratio of (c)-1/(14): 1/4, 1/1) shown in Example 7 were each sealed, as they were in the state of an isotropic phase, into the same liquid-crystal device as in Example 5. An electric field of ±20 V/µm was applied to the device where the liquid crystal rendered the SmC* phase. As a result, it was observed that the molecules were inverted in response to the electric field. Table 5 shows the speed of response to the electric field. Compositional ratio (c)-1/(14) Temperature (°C) Response speed 1/4 110 1.2 ms " 120 0.9 ms 1/1 60 4.2 ms " 90 2.0 ms Example 9 Example 1 was repeated except that the diol used therein was replaced with two kinds of compounds represented by the following formulas, which were used in the compositional ratios as shown in Table 6. Copolymers (d) were thus obtained. Copolymer (d): Fig. 3 shows a phase diagram based on the results of DSC measurement and polarizing-microscopic observation. In the drawing, "Ch" indicates "Cholesteric phase". Liquid-crystal devices were prepared in the same manner as in Example 3 from the copolymers having the respective compositional ratios. A voltage of +20 V/µm was applied to the devices where the liquid crystal rendered the chiral smectic C phase, and response speeds were observed to obtain the results as shown in Table 6. Comparative Example 2 Example 9 was repeated but using a polymer of x = 0, to obtain the results shown in Table 6. x (mol%) y (mol%) Response speed (msec.) Mn / Mw Example 9: 100 0 200 8.5x10 3 /1.6x10 4 70 30 70 8.2x10 3 /1.5x10 4 50 50 40 6.4x10 3 /1.1x10 4 20 80 300 8.7x10 3 /1.6x10 4 Comparative Example 2: 0 100 No response 6.3x10 3 /1.2x10 4 Comparative Example 3 The polymeric liquid-crystalline compound represented by the following structural formula was formed into a film, and the film was monoaxially stretched. The film thus treated was inserted between glass substrates each provided thereon with an ITO transparent electrode on which a polyimide aligning film was formed, which substrates were pressure-bonded by heating in the manner that its thickness was set to be about 5 µm. The device was gradually cooled from Isotropic phase to SmC* phase and an alignment with multiple domains was obtained. Using relatively large domains among them, a voltage of ±20 V/µm was applied to reveal that there was shown a response speed of about 500 msec. Mn = 5.3 x 10 3 Mw = 8.5 x 10 3 Example 10 A copolymer was obtained in the same manner as in Example 9 except that the diol in Example 1 was replaced with two kinds of compounds represented by the following formulas. Copolymer: Fig. 10 shows a phase diagram based on the results of DSC measurement and polarizing-microscopic observation. In the drawing, "Tg" indicates "Glass transition temperature". Molecular weight of the copolymer shown in Fig. 10: x = 100 75 50 25 Mn : 1.2x10 4 1.4x10 4 8.9x10 3 6.5x10 3 Mw : 3.3x10 4 2.3x10 4 1.5x10 4 1.2x10 4 Comparative Example 4 Example 1 was repeated except that the diol used therein was replaced with a compound represented by the following formula, to give a polymeric liquid-crystalline compound represented by the following structural formula. Polymer: Mn = 7.8 x 10 3 Mw = 1.8 x 10 4 DSC measurement and polarizing-microscopic observation revealed that the liquid-crystal phase transition points were as follows, and the liquid crystal rendered the SmC* phase only in the course of the temperature drop. Comparative Example 5 Example 1 was repeated except that the diol used therein was replaced with a compound (1.5 g) represented by the following formula, to give 1.2 g of a polymer (e). Polymer (e); Phase transition point of the polymer (e): Mn = 1.2 x 10 4 Mw - 3/3 x 10 4 Examples 11 to 16 Example 1 was repeated except that the compounds used therein was replaced with the combinations of mesogen group precursors and diols as shown in the following Table 7. Polymers as shown in Table 8 were thus obtained. DSC measurement and polarizing-microscopic observation revealed that the liquid-crystal phase transition points were as shown in Table 9. Example 17 To a solution of 3.7 g of 4,4'-dihydroxybiphenyl in 150 ml of pyridine kept at 5°C or less under an atmosphere of nitrogen gas, a dichloromethane solution of 5.1 g of a chlorocarbonate compound represented by the formula was dropwise added with stirring. After stirring for 1 hour, the reaction mixture was further stirred at room temperature for 40 hours. The reaction mixture was treated with a dilute hydrochloric acid, and then the dichloromethane solution was washed with water. The concentrated dichloromethane solution was put into methanol, and the precipitate thus produced was purified several times by the same procedure, followed by drying under reduced pressure to give 1.8 g of a polymer of the formula Mn / Mw = 8,300/19,000 [α ] 25 D = +4.8°(C = 0.95; solvent: chloroform) NMR data (δppm(TMS)): 1.4 (d; 3H, methyl) 2.1 (m; 2H, methylene) 3.6, 4.5 (m, t; 6H, methylene) 5.3, (m, 1H, methine) 7.6, (d; 4H, phenylene) 8.0, (d; 4H, phenylene) Liquid-crystal phase transition points were as follows: Example 18 The following polymer was obtained in the same manner as in Example 1. Mn = 1.0 x 10 4 Mw = 2.3 x 10 4 As a result, liquid-crystal phase transition points were as follows: As having been described above, it is possible according to the present invention to readily obtain a novel polymeric liquid-crystalline compound or copolymerized polymeric liquid-crystalline compound and a liquid-crystal composition containing these polymeric liquid-crystalline compounds and a low-molecular liquid crystal, that can render a chiral smectic phase (Sm* phase) over a wide temperature range, can stably exhibit the chiral smectic phase at the time of both temperature rise and temperature drop, and also can form a thin film or be formed into a film with ease. Besides, formation of a variety of copolymerized polymeric liquid-crystalline compounds makes it possible to give variety to the control of liquid-crystal temperature range or the control of electrical characteristics. Moreover, when these polymeric liquid-crystalline compound, copolymerized polymeric liquid-crystalline compound and liquid-crystal composition are applied in liquid-crystal devices, the large-area device can be readily achieved. At the same time, application of an electric field when the liquid crystal renders the SmC* phase brings about a stable and good switching effect, so that it is possible to obtain liquid-crystal devices capable of being utilized as devices in which various electro-optic effects are applied. In addition, when the liquid-crystal composition comprising the specific polymeric liquid-crystalline compounds of the present invention is obtained, the response can be improved compared with the sole use of the polymeric liquid-crystalline compound or the copolymerized polymeric liquid-crystalline compound and hence the present invention can be made more useful in view of the functions required when used as the device prepared in the form of a film. Furthermore, the copolymerization with a polymeric liquid crystal having a smectic phase is carried out to widen and stabilize the temperature range of a chiral smectic phase so that the chiral smectic phase rendered when a polymeric liquid crystal having an optically active group is formed can be stably exhibited and the temperature range therefor can be more expanded. Hence, it is possible to provide more useful copolymerized polymeric liquid-¶ crystalline compound and compositions thereof. Thus, the present invention can be said to be more effective for settling the existing circumstances in which the polymeric liquid crystals comprising a main chain having an optically active group and a mesogen group have sufficiently exhibited the chiral smectic phase only in a few examples and have had limitations on their utilization.

Claims: A polymeric liquid-crystalline compound comprising a main chain having a repeating unit represented by any one of the following formulas (Ia), (IIa) and (IIIa): wherein are each selected from any one of provided that at least one of represents Y 1 represents any one of a single bond, -CH=CH-, -C≡C, -N=N-, -CH=N-, -CH 2 CH 2 - and -CH 2 O-; B represents a flexible group derived from an optically active lactic acid and represented by the formula wherein X represents a hydrogen atom or a methyl group and Y represents a hydrogen atom or a methyl group, provided that X is not the same as Y, k is 0 or 1, and m1 is 1 to 18, or wherein X represents a hydrogen atom or a methyl group and Y represents a hydrogen atom or a methyl group, provided that X is not the same Y, k is 0 or 1, m2 is 2 to 10 and m3 is 2 to 5; X 1 and X 2 each represent a group containing any one of an ester bond, an ether bond and a carbonate bond, and may be the same or different from each other; and n represents 5 to 1,000, wherein Y 1 , B, X 1 , X 2 and n are as defined above provided that B is held in an amount of not less than 1 mol % based on the total flexible groups; C represents a mesogen group wherein and Y 1 are as defined above. D represents a group represented by the same formula as B or a straight-chain or branched alkylene, provided that D is not the same as B; and x + y = 1, wherein Y 1 , B, X 1 , X 2 , n and x + y are as defined above, provided that B is held in an amount of not less than 1 mol% based on the total flexible groups as defined above, C represents a mesogen as defined above, E represents a flexible group which is a straight-chain or branched-chain group containing no optically active group; and said polymeric liquid-crystalline compound having a weight average molecular weight (Mw) of from 2,000 to 500,000. The polymeric liquid-crystalline compound according to Claim 1, wherein said is-selected from the following structural formulas: The polymeric liquid-crystalline compound according to Claim 1, wherein said group represented by B is selected from the following structural formulas: A liquid-crystal composition comprising the polymeric liquid-crystalline compound according to claim 1 in an amount of not less than 5 parts by weight based on 100 parts by weight of the liquid-crystal composition. A liquid-crystal composition comprising the polymeric liquid-crystalline compound according to claim 1 in an amount of not less that 10 parts by weight based on 100 parts by weight of the liquid-crystal composition. A liquid-crystal composition according to claim 4 or 5, comprising further a low-molecular liquid crystal compound. A liquid-crystal composition according to claim 6 wherein said low-molecular liquid crystal compound is at least one compound represented by the following formulae (1) to (35): The polymeric liquid crystalline-compound according to claim 1, wherein each B in the formulae (Ia), (IIa) and (IIIa) represents an optically active group, respectively. The polymeric liquid crystalline-compound according to claim 1, wherein said group represented by D is selected from the structural formulas and and the asterisk * representing an optically active group. The polymeric liquid crystalline-compound according to claim 1, wherein said group represented by E is selected from the structural formulas The polymeric liquid crystalline-compound according to claim 1, wherein the homopolymer having a repeating unit of the polymeric liquid crystal represented by -(X 1 -C-X 2 -E)- in the formula renders a smectic C phase. A-liquid-crystal device comprising a substrate and, provided thereon, a film comprising the polymeric liquid-crystalline compound according to Claim 1. The liquid-crystal device according to Claim 12, wherein said film has been subjected to alignment treatment. The liquid-crystal device according to claim 13, wherein said alignment treatment is a stretching alignment treatment. The liquid-crystal device according to claim 13, which is further provided with an aligning film. A liquid-crystal device comprising a substrate and, provided thereon, a film of a liquid-crystalline composition comprising the polymeric liquid-crystalline compound according to claim 1. A liquid-crystal device according to claim 16, wherein said compound is contained in said liquid-crystal composition in an amount of not less than 5 parts by weight based on 100 parts by weight of said composition. The liquid-crystal device according to claim 16 or 17, wherein said film has been subjected to alignment treatment. The liquid-crystal device according to claim 16 or 17, wherein said alignment treatment is a stretching alignment treatment. The liquid-crystal device according to claim 16 or 17, which is further provided with an aligning film.

Inventors: SATO KOICHI, TOSHIDA YOMISHI, YOSHINAGA KAZUO, SATO, KOICHI, TOSHIDA, YOMISHI, YOSHINAGA, KAZUO, SATO, KOICHI, C/O CANON KABUSHIKI KAISHA, TOSHIDA, YOMISHI, C/O CANON KABUSHIKI KAISHA, YOSHINAGA, KAZUO, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1990
Main classification: C09K19
IPC codes: C09K19