JPH026797B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid crystal composition using a novel liquid crystal compound that has a high transition temperature from a nematic liquid crystal phase to an isotropic liquid phase and a wide liquid crystal temperature range. In the field of display devices, electro-optical elements with low power consumption are desired. Liquid crystal display cells are capable of electrically controlling the alignment of liquid crystal molecules, and have very high electrical resistance, so they have been developed to meet such demands. Attention has been paid. The present invention has the general formula: (In the formula, X represents a halogen atom, an alkyl group having 1 to 8 carbon atoms, or a cyano group, and R represents 1 to 8 carbon atoms.
(representing an alkyl group of 8)
This is a liquid crystal composition containing 0.05-90wt%. The compound represented by the formula () has a high transition temperature from a nematic liquid crystal phase to an isotropic liquid phase, has a wide liquid crystal temperature range, has a low viscosity, and is chemically stable against moisture and light. It is a certain liquid crystal compound. Therefore, a liquid crystal display cell containing the compound represented by the formula () is capable of stable high-speed response display over a wide temperature range. In the compound of formula (), when X is an alkyl group, it is preferable because a linear alkyl group exhibits a particularly high clearing point (temperature at which the nematic liquid crystal phase changes to an isotropic liquid phase). Further, when X is a halogen, it is preferable to use fluorine or chlorine because the viscosity thereof is particularly low. Further, when R is a linear alkyl group, it is preferable because it exhibits a particularly high clearing point. When X or R is an alkyl group and the number of carbon atoms is small, the liquid crystal temperature range is generally narrow;
On the other hand, if the carbon number is large, the viscosity is high, so the number of carbon atoms is 1 to 8, preferably 2 to 6. This compound is used in liquid crystal display elements as a composition mixed with other liquid crystal compounds, but it is generally preferable to use it as a liquid crystal composition with a wide liquid crystal temperature range, and X and/or R are branched alkyl groups. In case the compound of formula () in the composition is 0.05~
5wt% used. When R is a linear alkyl group and X is a linear alkyl group, a fluorine atom, or a chlorine atom, the clearing point is high, so they are used in an amount of 1% to 90% by weight in the composition. This is 0.05-5wt% because it is added in small amounts as an optically active substance when it has a branched alkyl group.
When the alkyl group is a straight-chain alkyl group, it is sufficient to mix 1 to 90 wt% as a liquid crystal material with a high clearing point, and generally it is mixed at about 1 to 30 wt%. many. The components other than the compound of formula () in the composition of the present invention vary depending on the use, required performance, etc., but include components that exhibit liquid crystallinity at high temperatures, low viscosity components for low temperatures, and other components that improve dielectric anisotropy. A component that imparts cholesteric properties, a component that imparts dichroism, a component that imparts conductivity, and various other additives may be appropriately mixed and used. Specifically, there are the following compounds. In the following formulas, R′ and R″ represent groups such as an alkyl group, an alkoxy group, a halogen atom, and a cyano group. Note that these compounds are merely examples, and substitution of a hydrogen atom with a halogen atom, cyano group, methyl group, etc., substitution of a cyclohexane ring, benzene ring with another six-membered ring, five-membered ring, etc., substitution of a ring with a halogen atom, a cyano group, a methyl group, etc. Various materials can be selected and used, such as changing the bonding group between them. The composition of the present invention containing the compound of formula () is used by being injected into a liquid crystal cell. A typical liquid crystal cell is a twisted nematic (TN) type liquid crystal cell, in which transparent electrodes such as In ₂ O ₃ -SnO ₂ are formed in a desired pattern on the inner surface of a transparent substrate such as glass or plastic. as needed
There is one in which the substrates are overcoated with SiO ₂ , polyimide, etc., and a horizontal alignment layer is formed, and the periphery is sealed, liquid crystal is injected, and the injection port is sealed, and polarizing plates are laminated on both outer surfaces. used.
In addition, a phase change type, a guest host type, a dynamic scattering type, or a combination thereof may be used. Furthermore, the structure of the cell includes providing an undercoat layer such as SiO ₂ or Al ₂ O ₃ between the transparent substrate and the transparent electrode, using a reflective electrode, and using a two-layer electrode.
Various applications are possible, such as using a color polarizing plate, using a color filter, using a semiconductor substrate, and using a two-layer element, and various uses such as watches, calculators, measuring instruments, automobile instruments, games, computer terminals, etc. It can be used for Among the compounds of formula (), those in which X is an alkyl group or a halogen atom can be produced, for example, by the following production method. (As long as in the above formula, X is a halogen atom or an alkyl group, and R is an alkyl group.) First step: Alkylbenzene or halobenzene is reacted with cyclohexene and acetyl chloride in the presence of aluminum chloride to form a compound of formula (). Manufacture. Second Step The compound of formula () produced in the first step is treated with a sodium hypochlorite solution or sodium hypobromite solution to produce a compound of formula (). Third Step The compound of formula () produced in the second step is chlorinated using a chlorinating agent such as thionyl chloride or phosphorus oxychloride to produce a compound of formula (). Fourth Step A Grignard reagent prepared from trans-4-alkylcyclohexylmethyl bromide and metallic magnesium is reacted with the compound of formula () produced in the third step in tetrahydrofuran to produce a compound of formula (). Fifth Step The compound of formula () produced in the fourth step is reduced by the Wolff-Xiyner method using hydrazine or the Clemensen method using zinc amalgam and hydrochloric acid to produce a compound of formula (). Among the compounds of formula (), those in which X is a cyano group can be produced by the following production method. (In the formula, R represents an alkyl group) 1st to 5th steps when X is an alkyl group or a halogen atom, using benzene instead of alkylbenzene or halobenzene in the method for producing a product where X is an alkyl group or a halogen atom A compound of formula () is produced by performing the same operation as above. 6th Step The compound of formula () produced in step 5 is reacted with oxalic acid dichloride to produce the compound of formula (XI). Seventh Step: The compound of formula (XII) is produced by reacting the formula (XI) produced in the sixth step with aqueous ammonia. Eighth Step The compound of formula (XII) produced in the seventh step is dehydrated using a dehydrating agent such as phosphorus oxychloride to produce the desired compound of formula (). Next, the present invention will be specifically explained with reference to Examples. Among the compounds of the formula (), those in which X is a linear alkyl group can also be produced from the compound of the formula (), which is an intermediate for the production of those in which X is a cyano group, by the following production method, for example. be able to. 6th step The compound of formula () produced in step 5 is reacted with an alkane carboxylic acid chloride in the presence of a Friedel-Crafts catalyst such as aluminum chloride in an inert organic solvent such as carbon disulfide. , to produce a compound of formula (). Seventh Step The compound of formula () produced in the sixth step is reduced by the Wolff-Xiyner method using hydrazine or the Clemensen method using zinc amalgam to produce a compound of formula (). Next, a specific example of synthesis of the compound of formula () will be shown. Synthesis Example 1 A mixture of acetyl chloride (473 g, 6.0 mol) and cyclohexene (555 g, 6.8 mol) was added to a mixture of chlorobenzene (1500 g, 13.3 mol) and aluminum chloride (1080 g, 8.1 mol) while keeping the temperature below -20°C for about 30 min. The solution was added dropwise over a period of time, and after the addition, the solution was slowly warmed to room temperature. After the generation of hydrogen chloride gas had stopped, the reaction mixture was poured into 1:1 hydrochloric acid 5 to separate the oil layer, and the aqueous layer was extracted with diethyl ether.The organic layers were combined and dried, and then the solvent was distilled off using an evaporator. . The remaining oily substance was distilled under reduced pressure to obtain 1131 g of a fraction with a boiling point of 120° to 130°C/0.1 mmHg. A 1:1 mixture of methanol and ethanol 2 was added to this fraction, cooled in a dry ice/methanol bath, and the resulting crude crystals were recrystallized from 500 ml of methanol.Trans-4-(p-chlorophenyl)-1-acetyl -Cyclohexane
Obtained 165g. Yield 12%, melting point 74.6℃. Next, a sodium hypobromite aqueous solution obtained by dropping bromine (385 g, 2.41 mol) into an aqueous solution 1 of sodium hydroxide (264 g, 8.6 mol) was added to trans-4-(p-chlorophenyl)-1-acetylcyclohexane ( 165 g, 0.70 mol) in 800 ml of dioxane solution. After stirring at room temperature for 2 hours after the dropwise addition, neutral organic matter was removed by extraction with ether, and the aqueous layer was acidified using hydrochloric acid to obtain colorless crystals. This was separated, washed with water, and dried to obtain 160 g of trans-4-(p-chlorophenyl)cyclohexanecarboxylic acid. Yield 96%, melting point 235℃
(Disassembly). Next, trans-4-(p-chlorophenyl)cyclohexanecarboxylic acid (160 g, 0.67 mol) was stirred with 100 ml of thionyl chloride and 500 ml of carbon tetrachloride at reflux temperature for a day and night, then the solvent was distilled off using an evaporator, and then the pressure was reduced. By distillation, trans-4-(p-chlorophenyl)cyclohexanecarboxylic acid chloride was obtained as a yellow liquid. Yield 152g, yield 88%, boiling point 144℃/0.3
mmHg. Grignard reagent was then prepared from trans-4-n-butylcyclohexylmethyl bromide (18.6 g, 0.08 mol) and magnesium metal (2.0 g, 0.08 gram atom) in 150 ml of tetrahydrofuran; -chlorophenyl)cyclohexanecarboxylic acid chloride (20.6
g, 0.08 mol) and tetrahydrofuran (50 ml) while keeping the temperature below -50°C. After the addition, stirring was continued for 2 hours, 100 ml of water was added to separate the oil layer, and the aqueous layer was extracted with diethyl ether. The organic layers were combined into one, washed with a 20% aqueous sodium hydroxide solution, washed with water, dried, and the solvent was distilled off. The remaining solid was recrystallized twice from hexane to give the formula 8.3 g of the compound was obtained. Yield 28%, melting point 74.0℃. Then the expression The compound (8.3 g, 0.022 mol), 6 ml of hydrazine hydrate, and 6 g of potassium hydroxide were heated in 100 ml of diethylene glycol at 190°C for 12 hours, then poured into water, extracted with chloroform, dried, and the solvent was distilled off. A yellow solid remained. Recrystallize this twice with ethanol to obtain the desired formula 7.3 g of the compound was obtained. The yield was 92%, and observation under a polarizing microscope with a hot stage showed that the compound had a nematic liquid crystal phase between 54.3°C and 149.2°C. The ¹ H NMR spectrum of this compound was as follows. ¹ H NMR (CDCl ₃ solvent, TMS internal standard) δ (ppm) 7.3-7.0 A ₂ B ₂ pattern 4H 2.6-0.7 complex m. 33H The KBr tablet IR spectrum of this compound is shown in FIG. Synthesis Example 2 The following series of operations were carried out in the same manner as in Synthesis Example 1 except that chlorobenzene was replaced with fluorobenzene to obtain the compound shown below. Trans-4-(p-fluorophenyl)-1-
Acetylcyclohexane yield 14%, melting point 51.2℃. Trans-4-(p-fluorophenyl)cyclohexanecarboxylic acid Yield 91%, melting point 201℃ (decomposition) Trans-4-(p-fluorophenyl)cyclohexanecarboxylic acid chloride Yield 91%, boiling point 120
°C/0.3mmHg formula Compound with yield 25%, melting point 62.4℃, formula The compound with a yield of 85% was found to have a nematic phase between 72.3°C and 126.5°C. ¹ H, ¹⁹ F NMR of this compound was as follows. ¹ H NMR (CDCl ₃ solvent TMS internal standard) δppm 7.3-6.8 complex m. 4H 2.6-0.7 complex m. 33H ¹⁹ F NMR (CDCl ₃ solvent CFCl ₃ internal standard) ψ ^* (ppm) 116.5 t (J=9Hz) of t(J=5Hz) The KBr tablet IR spectrum of this compound is shown in FIG. Synthesis Example 3 The following compound was obtained by performing the following series of operations in the same manner as in Synthesis Example 1, using benzene instead of chlorobenzene. Trans-4-phenyl-1-acetylcyclohexane Yield 27% Trans-4-phenylcyclohexanecarboxylic acid Yield 90% Trans-4-phenylcyclohexanecarboxylic acid chloride Yield 87% Boiling point 140℃/0.6mmHg Formula Compound Yield 36% Melting point 68.9℃ Formula Compound Yield 83% Melting point 54.0℃ The following formula compound (65.2g, 0.2mol) in 280ml of carbon disulfide
29.2g of anhydrous aluminum chloride,
It was added dropwise to a mixture of 27.8 g of oxalic acid dichloride and 280 ml of carbon disulfide at 15°C over 30 minutes.
After stirring for a further minute, the mixture was heated under reflux for 1 hour. The reaction mixture was transferred to a mixture of ice and concentrated hydrochloric acid (5:1) for decomposition, and then extracted with toluene. 300 ml of 20% KOH was added to the extracted toluene layer, and the mixture was heated under reflux for 3 hours. After neutralizing this reaction mixture with hydrochloric acid, the toluene layer was separated, and after distilling off the toluene using a rotary evaporator, the formula 41.4g of the compound was obtained. Yield 56%, IR ^KBr 〓 _C=O 1680cm
^-1 . The formula obtained in this way (37.0 g, 0.1 mol) of thionyl chloride 50
ml, mixed with 200 ml of benzene, heated under reflux for 5 hours, and then distilled off excess thionyl chloride and benzene using a rotary evaporator. The compound was obtained. IR ^KBr 〓 _C=O 1770cm ^-1 The benzene solution of the above acid chloride was added dropwise to 200ml of concentrated ammonia water at 5°C, the precipitate formed was removed, and the formula 31g of the compound was obtained, yield 82%, melting point 26.5°C. The formula obtained in this way compound (19 g, 0.05 mol) of chlorobenzene 50
This suspension was added to a mixture of 7.5 g of pyridine, 35 ml of chlorobenzene, and 8 g of phosphorus oxychloride at 0°C over about 30 minutes, and then
The mixture was heated to 55°C over a period of minutes and kept at this temperature for 1 hour. After the reaction, the reaction mixture was transferred onto ice to destroy excess phosphorus oxychloride. The oil layer was extracted with benzene, and the extract was dried over anhydrous magnesium sulfate.
Low-boiling components were distilled off using a rotary evaporator to obtain a solid product, which was recrystallized from hexane and further purified by chromatography using alumina as a fixed layer and toluene as a developing solution. , further recrystallized from hexane to give the formula 13.4g of a colorless compound represented by was obtained. Yield 74
%. This compound was found to exhibit a nematic liquid crystal phase between 63.5°C and 189.8°C. ¹ H NMR (CDCl ₃ solvent, TMS internal standard) of this compound was as follows. δ (ppm) 0.7~2.6 complex m 33H 7.2~7.7 A ₂ B ₂ pattern 4H The IR spectrum of this compound (KBr tablet) is
As shown in the figure. Synthesis Example 4 By using trans-4-n-propylcyclohexylmethyl bromide in place of trans-4-n-butylcyclohexylmethyl bromide in Synthesis Example 3 and performing the same procedure, the formula The compound was obtained. Melting point 67.2℃ The following formula (40.0 g, 0.13 mol) and anhydrous aluminum chloride (21 g, 0.16 mol) in 300 ml of carbon disulfide.
Propionic acid chloride (14.8 g, 0.16 mol) was added dropwise to this mixture at 15°C, and the mixture was stirred at room temperature for 4 hours after the dropwise addition. The reaction mixture was poured into 20% diluted hydrochloric acid, extracted with ether, dried, and the solvent was distilled off to obtain yellow crystals, which were recrystallized from hexane (300 ml) to obtain the formula The compound was obtained. Yield 36.0g, yield 77%, melting point
88.4℃. Then the expression The compound (36.0 g, 0.098 mol), 55 ml of hydrazine hydrate, and 55 g of potassium hydroxide were heated in 500 ml of diethylene glycol at 190°C for 12 hours, poured into water, extracted with chloroform, dried, and the solvent was distilled off. Recrystallize the remaining solid twice from ethanol to obtain the desired formula The compound was obtained. Yield: 30.8g, yield: 88%. Observation under a polarizing microscope equipped with a hot stage shows that this compound exhibits a smectic liquid crystal phase at room temperature, transitions from a smectic liquid crystal phase to a nematic liquid crystal phase at 141.8°C, and then changes from a nematic liquid crystal phase to an isotropic liquid crystal phase at 144.0°C. It was found that it metastasized to ¹ H NMR of this compound was as follows. ¹ H NMR (CDCl ₃ solvent, TMS internal standard) δ 7.05 s 4H δ 2.55 t J=7Hz 2H δ 2.6-0.7 complex m 36H Synthesis Examples 5-14 The following compounds were obtained in the same manner as in Synthesis Example 1. formula compound formula of Compound Nematic liquid crystal phase 77.0℃～155.0℃ ¹ H NMR (CDCl ₃ solvent, TMS internal standard) δ 7.3～7.0 A ₂ B ₂ pattern 4H 2.6～0.7 complex m 31H Formula compound formula of compound formula of Compound Nematic liquid crystal phase 64.3℃～130.2℃ ¹ H NMR (CDCl ₃ solvent, TMS internal standard) δ 7.3～6.8 complex m 4H 2.6～0.7 complex m 31H ¹⁹ F NMR (CDCl ₃ solvent, CFCl ₃ internal standard) φ 116.5 t(J=9Hz) of t(J=5Hz) Formula compound formula of compound formula of compound formula of compound formula of Compound Synthesis Examples 15 to 17 The following compounds were obtained in the same manner as in Synthesis Example 3. formula compound formula of Compound of Nematic liquid crystal phase 86.3℃～197.1℃ ^1H NMR (CDCl ₃ solvent, TMS internal standard) δ 7.7～7.2 A ₂ B ₂ pattern 4H 2.6～0.7 complex m. 31H Formula Examples of compounds with formula The viscosity of liquid crystal compositions using the compounds synthesized in Synthesis Examples 1 to 4 was compared using the compound as a comparative example. Trans-1-n-propyl-4-(4'-ethoxyphenyl)cyclohexane 25wt%, trans-1-n-propyl-4-(4'-n-butoxyphenyl)cyclohexane 20wt% and Merck Liquid Crystal ZLI-1083 The 55 wt% mixture (hereinafter referred to as base liquid crystal A) exhibited a viscosity of 45.3 cSt at 0°C. This mother liquid crystal A90wt% and each compound 10wt
Table 1 shows the viscosity at 0°C of the mixture with %.

【table】

[Table] As can be seen from this table, all of the liquid crystal compositions of the present invention exhibited low viscosity. The liquid crystal composition of the present invention contains 1 compound of formula ().
It is mixed with other types of nematic liquid crystals, cholesteric liquid crystals, smectic liquid crystals, dichroic dyes, etc., and is used as a liquid crystal display element by being sealed between transparent substrates having electrodes of a desired shape. As an example of this liquid crystal display element, an example in which it is applied to a TN (twisted nematic) liquid crystal display element will be shown. Two patterned glass substrates with transparent electrodes were rubbed, arranged so that the rubbing directions were perpendicular and the transparent electrode surfaces faced each other, and the periphery was sealed with a sealant so that the cell spacing was 8 μm. A liquid crystal composition in which 7 to 10 wt% of the compounds of Examples 1 to 3 were added to the base liquid crystal A was injected into the cell formed.
The injection port was sealed. Next, a voltage of 100 Hz AC was applied to this liquid crystal display element, and the change in light transmittance in a direction tilted 10 degrees from the normal direction of the substrate toward the direction with the strongest contrast was measured. Ten%
The changed applied voltage was defined as the threshold voltage _V10 . Table 2 shows the threshold voltage V ₁₀ at −20° C. and the temperature Tc at which the nematic liquid crystal phase changes to an isotropic liquid.

【table】

[Table] As can be seen from this table, the liquid crystal display element using the liquid crystal composition of the present invention was able to increase Tc with almost no increase in threshold voltage. Furthermore, this element may have various undercoats, overcoats for alignment control, polarizing plates, filters, reflective layers, etc. as necessary, and may be used as a multilayer cell or in combination with other display elements. Various methods can be used that use a semiconductor substrate or a light source. In addition, as a driving method for the liquid crystal display element, methods known in the liquid crystal display element industry are adopted, such as the dynamic scattering (DSM) method, the twisted nematic (TN) method, and the guest host (GH) method. be able to. The compounds of the present invention have a high transition temperature from a nematic liquid crystal phase to an isotropic liquid phase, have a wide liquid crystal temperature range, are chemically stable, and have low viscosity, making them extremely promising. A liquid crystal display element containing the compound of the present invention is capable of displaying a display that is stable over a wide temperature range and exhibits quick response, and thus can be applied to various uses including vehicles.

[Brief explanation of drawings]

Figures 1 to 3 show compounds of examples of the present invention.
It is an IR spectrum diagram.

Claims (1)

[Claims] 1. General formula (In the formula, X represents a halogen atom, an alkyl group having 1 to 8 carbon atoms, or a cyano group, and R represents an alkyl group having 1 to 8 carbon atoms) in an amount of 0.05 to 90 wt%. liquid crystal composition. 2 Compounds in which X represents a fluorine atom, a chlorine atom, a linear alkyl group having 1 to 8 carbon atoms, or a cyano group, and R is a linear alkyl group having 1 to 8 carbon atoms in the formula () The liquid crystal composition according to claim 1, which contains 1 to 90 wt% of.