p-Terphenyl derivatives and liquid crystalline compositions

Abstract: New p-terphenyl derivatives useful as components for preparing practical ferroelectric liquid crystalline compositions and excellent in chemical stability, as well as liquid crystalline compositions containing at least one of the p-terphenyl derivatives.

Description: The present invention relates to new liquid crystalline compounds as well as liquid crystalline compositions containing at least one of the liquid crystalline compounds. More particularly, the present invention relates to ferroelectric liquid crystals and to new p-terphenyl derivatives which are useful as components for preparing practical ferroelectric liquid crystalline compositions and excellent in chemical stability as well as liquid crystalline compositions containing at least one of the p-terphenyl derivatives. Liquid crystal display elements are widely used as display elements, e.g. for watches, electronic desk-top computers, personal word processors or pocket-size TV sets. They are, on one hand, characterized by such beneficial characteristics as no eyestrain because of their passive device, low electric power consumption and a thin structure, but on the other hand undergo restrictions in their practical applications because of slow in response and lack of memory effect. In an attempt to expand their areas of application there has been provided, for example, the super twisted nematic (STN) display system, which is an improvement of the twisted nematic (TN) display system. These systems, however, are not sufficient for large screen or graphic display use. Various studies have therefore been made of liquid crystal display elements which can supersede them. One such display system [N.A. Clark et al., Applied Phys. lett., 36, 899 (1980)] utilizes ferroelectric liquid crystals [R.B. Meyer et al., Physique, 36 L-69 (1975)]. Because of its advantageous characteristics such as fast response, which is 100 times as fast as that of conventional systems, and memory effect, it is expected to expand areas of application of liquid crystal display elements. The term "ferroelectric liquid crystal" is used to mean a series of smectic liquid crystals whose molecular longitudinal axis is at a certain angle to the normal of the layer, but in practice the chiral smectic C (SmC*) phase is utilized. In practice, ferroelectric liquid crystals for display elements are used as a liquid crystalline composition comprising a number of ferroelectric liquid crystalline compounds or prepared by blending such compound(s) and one or more compounds having the smectic C (SmC) phase. As is the case with the preparation of nematic liquid crystal display elements, mixing of a number of components is required in this case if different properties required for actual use such as operating temperature range, response time, helical pitch, chemical stability and so on are to be satisfied. Ferroelectric liquid crystalline compositions have not been put to actual use yet, it therefore being desired that a variety of compounds useful as components for such compositions be developed. In particular, there has been need for the development of substances which show the SmC phase over a wide temperature range, and which have the SmC* phase and an adequate spontaneous polarization value. The object of the present invention is to provide new substances which satisfy such need. Known p-terphenyl compounds of analogous structure are disclosed, for example, in EP-A-013277, GB-A-2200912 and Mol. Cryst. Liq. Cryst., 1985, Vol. 123, pp. 185-204. US-A-4 594 465 discloses a variety of compounds suitable for use in liquid crystal materials. These compounds include also terphenyls having the formula: wherein X₁ and X₂ are each H or F and R₁ and R₂ may be alkyl or alkoxy. A preferred feature of the invention in US-A-4 594 465 is a nematic or chiral nematic liquid crystal composition comprising a mixture of two or more compounds. EP-A-0 084 194 relates to anisotropic compounds for liquid crystals forming a nematic phase while the tendency of forming a smectic phase is avoided. It discloses among a huge number of compounds also terphenyls of the formula: wherein R¹ and R² may be alkyl or alkoxy and X means halogen. No compounds claimed in the present application are literally mentioned. WO-A-90/02161, a document according to Art. 54(3) EPC, describes liquid crystalline compounds including compounds of the formula: wherein X¹ and X² may be O and each of R¹ and R² a chiral residue. It does not specifically disclose compounds falling under the claims of the present invention. WO-A-89/2039 is also a document according to Art. 54(3) EPC and discloses terphenyl derivatives of the formula wherein R¹ and R² may be alkoxy. It does not specifically disclose compounds falling under the claims of the present invention. It is the object of the present invention to provide substances which have a wider temperature range for the SmC or SmC* phase than these known compounds, and substances which have SmC* phase and an adequate spontaneous polarization value, the substances showing chemical stability and excellent response time. The present invention thus provides p-terphenyl derivatives of the general formula wherein each of R¹ and R² is a straight or branched chain alkyl group having 1-18 carbon atoms, each of Y and Z is a single bond or O, and the terphenyl derivative exhibits a smectic C phase or a chiral smectic C phase. The new compounds according to the present invention, even when used individually, exhibit the SmC or SmC* phase over a wide temperature range. Ferroelectric liquid crystalline compositions with an even wider temperature range for the SmC* phase, however, are obtainable by preparing mixtures of these compounds or mixtures of one or more such compounds with one or more other liquid crystalline compounds or compositions. Accordingly, the p-terphenyl derivatives according to the present invention are useful substances utilizable as components for preparing ferroelectric liquid crystalline compositions for use in ferroelectric liquid crystal display elements. Processes for their preparation will be described below in detail by showing synthetic routes and working examples. The phase transition temperature of synthesized compounds will be affected by the measuring instrument or method or the purity of the substance, it thus being to be understood that measured values will more or less vary. The new p-terphenyl derivatives according to the present invention can be synthesized through a variety of routes, for example according to the routes schematized below. The schematized synthetic routes will now be described below. 4-Alkyloxy-4''-alkyloxy-p-terphenyls and derivatives thereof (I-4) can be synthesized by subjecting 4-bromobiphenyl or its derivative as starting material to acetylation, Baeyer-Villiger oxidation, hydrolysis and etherification and then to cross-coupling reaction with a Grignard reagent prepared from a 4-alkyloxybromobenzene or its derivative. 4-Alkyloxycarbonyl-4''-alkyl-p-terphenyls and derivatives thereof (I-14) can be synthesized by subjecting 4-bromobiphenyl or its derivative as starting material to acylation, reduction, cross-coupling reaction with a Grignard reagent prepared from bromobenzene or its derivative, acetylation, haloform oxidation and esterification. 4-Acyloxy-4''-alkyloxycarbonyl-p-terphenyls and derivatives thereof (II-4) can be synthesized by subjecting anisole or its derivative as starting material to bromination, ether-cleavage and benzyl-etherification followed by conversion into a Grignard reagent, which is then subjected to cross-coupling reaction with a 4-bromo-4'-alkyloxycarbonyl-biphenyl or its derivative followed by ether-cleavage and esterification. The other end compounds (I-1, I-2, I-3, I-5, I-6, I-7, I-8, I-9, I-10, I-11, I-12, I-13, II-1, II-2 and II-3) shown in "Schematized synthetic route examples" can be synthesized by appropriately combining the above mentioned reactions in respective processes. In the examples given below, the notations and abbreviations are used to mean the following: GLC : gas chromatography HPLC : high performance liquid chromatography IR : infra-red rays absorption spectroscopy Mass : mass spectrometry m.p. : melting point C : crystals Sx : unidentified smectic phase S B : smectic B phase SmC, Sc : smectic C phase SmC*, Sc* : chiral smectic C phase S A : smectic A phase Ch : cholesteric phase I : isotropic liquid ? : temperature being indefinite Example 1 A reaction vessel was charged with 10g of 2-fluorophenol, 25g of (S)-1-methylhexyl tosylate, 20g of potassium carbonate and 160 ml of MEK, and the mixture was refluxed with stirring for 14 hours (the disappearance of the starting materials was confirmed by TLC). The reaction liquid was poured into diluted hydrochloric acid and the mixture was extracted with benzene. The extract was washed with water and dried over Glauber's salt, and the solvents were distilled off. The residue was distilled under reduced pressure to obtain 14g (74.5%) of (R)-2-(1-methylhexyl)oxyfluorobenzene. b.p. 113-117°C/9 mmHg A reaction vessel was charged with 13.9g of (R)-2-(1-methylhexyl)oxyfluorobenzene obtained in (a) above and 50 ml of chloroform. To the mixture was added dropwise 12.7g of bromine with stirring at room temperature. The resultant mixture was further stirred at room temperature (until the starting materials were confirmed by GLC to have disappeared) and a 10% aqueous solution of caustic soda was added with stirring. The organic layer was washed with water and dried over Glauber's salt. The solvents were distilled off and the residue was distilled under reduced pressure to obtain 14.2g (74.1%) of (R)-4-(1-methylhexyl)oxy-3-fluorobromobenzene. b.p. 98-110°C/0.3 mmHg A reaction vessel was charged with 20 ml of methylene chloride and 3.2g of anhydrous aluminum chloride. To the mixture was added 4g of octanoyl chloride with stirring at a temperature not higher than -5°C and was then added dropwise a solution of 3g of 4-bromo-2-fluorobiphenyl in 10 ml of methylene chloride. After the dropwise addition, the mixture was reacted for 3 hours with stirring at a temperature not higher than 0°C and then allowed to stand overnight at room temperature. The reaction liquid was poured into ice/diluted hydrochloric acid and the mixture was extracted with benzene. The benzene solution was washed with water, treated with diluted aqueous ammonia, washed with water and then dried over Glauber's salt. The benzene was distilled off and the residue was recrystallized from acetone to obtain 3.8g (84.2%) of 4-octanoyl-2′-fluoro-4′-bromobiphenyl. TLC monospot A reaction vessel was charged with 3.75g of 4-octanoyl-2′-fluoro-4′-bromobiphenyl obtained in (c) above and 20 ml of trifluoroacetic acid. To the mixture was added dropwise 2.4g of triethylsilane with stirring at room temperature. After stirring for 6 hours, the reaction liquid was poured into water and the mixture was extracted with benzene. The benzene extract was washed successively with water, an aqueous solution of sodium hydrogen carbonate and water, and then dried over Glauber's salt. The solvents were distilled off and the residue was distilled in a glass tube oven (GTO) to obtain 2.56g (71.1%) of 4-octyl-2′-fluoro-4′-bromobiphenyl. GTO-set temperature: 150°C/0.2 mmHg. TLC monospot A reaction vessel was charged with 0.4g of magnesium powder and a small piece of iodine. A small portion of a solution of 3.4g of (R)-4-(1-methylhexyl)oxy-3-fluorobromobenzene obtained in (b) above in 20 ml of THF was added. After initiation of the reaction (with heating applied where necessary), the remainder of the THF solution was added dropwise with stirring in such a manner that the resultant mixture was kept refluxed. The mixture was refluxed with stirring for a further period of 2 hours to prepare a Grignard reagent. Another reaction vessel was charged, under a stream of nitrogen, successively with 0.1g of dichlorobistriphenyl-phosphinepalladium[Cl₂Pd(PPh₃)₂], 20 ml of dried THF, 0.5 ml of a 1M solution of diisobutylaluminum hydride[(iso-C₄H₉)₂AlH] in hexane and a solution of 2.2g of 4-octyl-2′-fluoro-4′-bromobiphenyl obtained in (d) above in 20 ml of THF. The previously prepared Grignard reagent was added dropwise with stirring at 50°C and after the dropwise addition the mixture was reacted with stirring for 6 hours at the same temperature. The reaction liquid was poured into diluted hydrochloric acid and the mixture was extracted with benzene. The extract was washed with an aqueous solution of edible salt and dried over Glauber's. The solvents were distilled off and the residue was purified by way of column chromatography on silica gel (eluent: hexane/benzene = 6:1) and then recrystallized from acetone to obtain 1.3g (43.6%) of (R)-4-(1-methylhexyl)oxy-3,3′-difluoro-4″-octyl-p-terphenyl. The purity of this product was at least 99% by HPLC. The resultant substance was confirmed to be the end product in view of its measurement by IR and its molecular ion peak found at 492 by Mass and in view of the starting materials used. This product was inserted into a Mettler hot stage FP-82 and its phase transition was observed under a polarization microscope. A result of the observation is shown in Table 1. Example 2 A reaction vessel was charged with 113g of anhydrous aluminum chloride and 600 ml of methylene chloride. To the mixture was added dropwise 113g of acetyl chloride with stirring at a temperature not higher than 0°C, and was then added dropwise a solution of 100g of 4-bromo-2-fluoro-biphenyl in 400 ml of methylene chloride. The mixture was reacted with stirring for 7 hours while gradually bringing it back to room temperature. The reaction liquid was poured into ice and diluted hydrochloric acid. The methylene chloride layer was washed successively with water, an aqueous solution of sodium hydrogen carbonate and water, and then dried over Glauber's salt. The solvent was then distilled off and the residue was recrystallized from acetone to give 96g (82.2%) of 4-acetyl-2'-fluoro-4'-bromobiphenyl. GLC 100% A reaction vessel was charged with 65g of 4-acetyl-2'-fluoro-4'-bromobiphenyl obtained in (a) above and 300 ml of methylene chloride. To the mixture was added dropwise 500 ml of 88% formic acid and 480 ml of acetic anhydride with stirring at 10°C and was then added 1.5 ml of concentrated sulfuric acid. To the resultant mixture was added dropwise 150 ml of 35% aqueous hydrogen peroxide over a period of 3 hours. After the dropwise addition, the mixture was gradually warmed up to 45-50°C at which temperature it was reacted with stirring for 30 hours. The reaction liquid was poured into ice water and the mixture was extracted with benzene. The extract was washed with an aqueous solution of sodium hydrogen carbonate and then with water, and dried over Glauber's salt. The solvents were distilled off and the residue obtained and 2ℓ of ethyl alcohol were charged into another reaction vessel. To the mixture was added a 25% aqueous solution of caustic potash and the resultant mixture was refluxed with stirring for 8 hours. The reaction liquid was poured into ice and diluted hydrochloric acid and the mixture was extracted with benzene. The extract was washed with an aqueous solution of edible salt and dried over Glauber's salt. The solvent was distilled off and the residue was purified by way of column chromatography on silica gel using benzene as eluent to obtain 28.1g (47.5%) of 4-hydroxy-2'-fluoro-4'-bromobiphenyl. A reaction vessel was charged with 5g of 4-hydroxy-2'-fluoro-4'-bromobiphenyl obtained in (b) above, 5.2g of octyl bromide, 4g of potassium carbonate and 50 ml of 2-butanone (MEK), and the reaction was effected for 8 hours under reflux with stirring. The reaction liquid was poured into diluted hydrochloric acid and the mixture was extracted with benzene. The extract was washed with water and dried over Glauber's salt and then the solvents were distilled off. The residue was distilled in a glass tube oven (GTO) to obtain a fraction (GTO-set temperature: 150°C/0.2 mmHg), which was then purified by way of column chromatography on silica gel (eluent: hexane) to obtain 6.3g (88.7%) of 4-octyloxy-2'-fluoro-4'-bromo-biphenyl. Except that 2.3g of 4-octyloxy-2'-fluoro-4'-bromobiphenyl obtained in (c) above was used in place of 2.2g of 4-octyl-2'-fluoro-4′-bromobiphenyl used in Example 1 (e), the same operation was performed in the same manner as in Example 1 (e) to obtain 0.5g (17%) of (R)-4-(1-methylhexyl)oxy-3,3′-difluoro-4″-octyloxy-p-terphenyl. The purity of this product was at least 99% by HPLC. The resultant substance was confirmed to be the end product in view of its measurement by IR and its molecular ion peak found at 508 by Mass and in view of the starting materials used. This product was inserted into a Mettler hot stage FP-82 and its phase transition was observed under a polarization microscope. A result of the observation is shown in Table 1. Example 3 A reaction vessel was charged with 15g of 2-fluorophenol, 25.9g of octylbromide, 46.2 g of potassium carbonate and 150 ml of cyclohexanone, and the mixture was stirred at 120-130°C for 12 hours. The reaction liquid was poured into diluted hydrochloric acid and the mixture was extracted with benzene. The extract was washed with water and dried over Glauber's salt. The solvents were distilled off, and the residue and 100 ml of chloroform were charged into a separate reaction vessel. With stirring at room temperature 44g of bromine was added dropwise and the mixture wa stirred at the same temperature for 6 hours and then poured into a diluted aqueous solution of caustic soda with stirring. The chloroform layer was washed with water and dried over Glauber's salt. The solvent was distilled off and the residue was distilled under reduced pressure to obtain 32g (78.8%) of 4-octyloxy-3-fluorobromobenzene. b.p. 122-130°C/0.3 mmHg Except that 3.6g of 4-octyloxy-3-fluorobromobenzene obtained in (a) above was used in place of 3.4g of (R)-4-(1-methylhexyl)oxy-3-fluorobromobenzene used in Example 1 (e), the operation was performed in the same manner as in Example 1 (e) to obtain 1.0g (32.6%) of 4-octyloxy-4''-octyl- 3,3'-difluoro-p-terphenyl. The purity of this product was at least 99% by HPLC. The resultant substance was confirmed to be the end product in view of its measurement by IR and its molecular ion peak found at 506 by Mass and in view of the starting materials used. This product was inserted into a Mettler hot stage FP-82 and its phase transition was observed under a polarization microscope. A result of the observation is shown in Table 2. Example 4 Except that 3.6g of 4-octyloxy-3-fluorobromobenzene obtained in Example 3 (a) and 2.2g of 4-octyloxy-2'-fluoro-4'-bromobiphenyl obtained in Example 2 (c) were used in place of 3.4g of (R)-4-(1-methylhexyl)oxy-3-fluorobromobenzene and 2.2g of 4-octyl-2'-fluoro-4'-bromobiphenyl used in Example 1 (e), respectively, the operation was performed in the same manner as in Example 1 (e) to obtain 0.42g (13.9%) of 4,4''-dioctyloxy-3,3'-difluoro-p-terphenyl. The purity of this product was at least 98% by HPLC. The resultant substance was confirmed to be the end product in view of its measurement by IR and its molecular ion peak found at 522 by Mass and in view of the starting materials used. This product was inserted into a Mettler hot stage FP-82 and its phase transition was observed under a polarization microscope. A result of the observation is shown in Table 2. Example 5 Except that 17g of racemic-4-methylhexyl bromide was used in place of 25g of (S)-1- methylhexyl tosylate used in Example 1 (a), the operation was performed in the same manner as in Example 1 (a) to obtain 15g (80%) of racemic-2-(4-methylhexyl) oxyfluorobenzene. b.p. 120-122°C/7 mmHg Except that 13.9g of racemic-2-(4-methylhexyl)oxyfluorobenzene obtained in (a) above was used in place of 13.9g of (R)-2-(1-methylhexyl)oxyfluorobenzene used in Example 1 (b), the operation was performed in the same manner as in Example 1 (b) to obtain 16.7g (87%) of racemic-4-(4-methylhexyl)oxy-3-fluorobromobenzene. b.p. 124-134°C/0.25 mmHg Except that 3.4g of racemic-4-(4-methylhexyl)oxy-3-fluorobromobenzene obtained in (b) above and 2.2g of 4-octyloxy-2′-fluoro-4′-bromobiphenyl obtained in Example 2 (c) were used in place of 3.4g of (R)-4-(1-methylhexyl)oxy-3-fluorobromobenzene and 2.2g of 4-octyl-2′-fluoro-4′-bromobiphenyl used in Example 1 (e), respectively, the operation was performed in the same manner as in Example 1 (e) to obtain 0.23g of racemic-4-(4-methylhexyl)oxy-3,3′-difluoro-4″-octyloxy-p-terphenyl. The purity of this product was at least 99% by HPLC. The resultant substance was confirmed to be the end product in view of its measurement by IR and its molecular ion peak found at 508 by Mass and in view of the starting materials used. This product was inserted into a Mettler hot stage FP-82 and its phase transition was observed under a polarization microscope. A result of the observation is shown in Table 2. Example 6 A 3µm-thick liquid crystalline cell, provided with transparent electrodes, was prepared by subjecting the polyvinyl alcohol (PVA) - coated surface to a parallel aligning treatment by rubbing. The compound obtained in Example 2 was enclosed in the liquid crystalline cell and gradually cooled from the isotropic liquid phase to SmC* phase to prepare a liquid crystal element. This liquid crystal element was interposed between two polarization panels and a 200 Hz square wave of ± 25 V was applied thereto. Response times were determined from changes in intensity of transmission light. As a result, the response time was 180 µsec at 77°C and 180 µsec also at 50°C, showing a good dependency on temperature. Example 7 The compound from Example 3, a non-chiral substance with a SmC phase, and that from Example 2, a chiral substance, were mixed together in a ratio of 90:10 by weight to prepare a liquid crystalline composition. This composition showed the SmC* phase at 56-104°C. When the composition was used in the same manner as in Example 6 to prepare a liquid crystal element, its response time was found to be 280 µsec (measurement temperature: 102°C) and 320 µsec (measurement temperature: 70°C). Example 8 Each of the compounds obtained in Examples 1 and 2 was mixed, in a ratio of 10:90 by weight, with the following pyrimidine-type liquid crystalline composition, respectively, to prepare new liquid crystalline compositions. These compostions were each used in the same manner as in Example 6 to prepare liquid crystal elements and their response times were determined. The results are shown below. Pyrimidine-type liquid crystalline composition used: The temperature range for the SmC phase, found upon cooling, of this liquid crystalline composition was 54-12°C. Compound of the invention added Response time (µ sec) Measurement temperature(°C) SmC* temperature range upon cooling(°C) Example 1 252 49 52∼2 Example 2 241 51 54∼1 As is apparent from the above, the compounds of the present invention are useful substances utilizable for the manufacture of practical, ferroelectric liquid crystal display elements.

Claims: P-terphenyl derivative of the general formula: wherein each of R¹ and R² is a straight or branched chain alkyl group having 1-18 carbon atoms, each of Y and Z is a single bond or O and the terphenyl derivative exhibits a smectic C phase or chiral smectic C phase. The p-terphenyl derivative according to claim 1 wherein Y is O and Z is a single bond or O. The p-terphenyl derivative according to claim 2 wherein R¹ is an asymmetric carbon-containing alkyl group having 4-18 carbon atoms and R² is a straight chain alkyl group having 1-18 carbon atoms. The p-terphenyl derivative according to claim 2 wherein both R¹ and R² are straight chain alkyl groups having 1-18 carbon atoms. A liquid crystalline composition comprising at least one p-terphenyl derivative of the general formula (1) according to any one of claims 1 to 4. The use of a p-terphenyl derivative of the general formula (1) according to any one of claims 1 to 4 for the production of a display element, e.g. for watches, electronic desk-top computers, personal word processors or pocket-size TV sets.

Inventors: FUJII TSUNENORI, INOUE HIROMI, KURIHARA MAKOTO, SUGIURA ATSUSHI, SUZUKI KENJI, FUJII, TSUNENORI, INOUE, HIROMI, KURIHARA, MAKOTO, SUGIURA, ATSUSHI, SUZUKI, KENJI
Applicants: KANTO KAGAKU, KANTO KAGAKU KABUSHIKI KAISHA
Application year: 1989
Main classification: C07C43
IPC codes: C07C69, C07C13, C07C1, C07C43, C07C67, G02F1, C07C17, C09K19, C07C41, C07C25