JPH0665660B2 - Liquid crystal compound and liquid crystal composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel optically active liquid crystal compound and a liquid crystal composition containing the liquid crystal.

(Prior Art) Various liquid crystal display devices are currently in practical use. Among them, TN (Twi-sted Nemati) using nematic liquid crystal is used.
The c) type display system has excellent performance such as extremely low power consumption and is widely used. However, this display method has a drawback that the response speed is slow.

Recent industrial technology strongly demands high-speed response also in liquid crystal display elements, and various attempts have been made by improving liquid crystal materials to meet such requirements. Already in response to the above demand, a display device (NAClark, STLagerwall, App that utilizes the optical switching phenomenon of ferroelectric liquid crystal)
l.Phys.Lett., 36 , 899 (1980)) has been proposed. This ferroelectric liquid crystal is said to belong to a chiral smectic C phase (hereinafter abbreviated as SC ^* ) or a chiral smectic H phase (hereinafter abbreviated as HC ^* ) from the viewpoint of the liquid crystal structure.

(Problems to be Solved by the Invention) Table 1 shows a typical known ferroelectric liquid crystal.

(Notes 1 and 2: Ph.Martinot-Lagarde, J.Phy-sique, 37 ,
C3-129 (1976) A. Hallsby, M. Nilsson and B. Ottenh
olm, 3: Mol.Cryst.Liq.Cryst.Letters, 82, 61 (1982)) However, these compounds or cause isomerization in a short time by light and unstable to moisture, hydrolysis It is not preferable for a display device because it has an unstable element that it does not show a liquid crystal phase.

An object of the present invention is to provide a ferroelectric liquid crystal having photochemical and chemical stability without such an unstable element and a composition containing the liquid crystal.

(Means for Solving Problems) In order to solve the above problems, the present inventors have reached the present invention as a result of synthesizing and examining a liquid crystal substance containing many optically active groups.

That is, the present invention has the general formula (I) (In the formula, X and Y represent a hydrogen atom or a halogen atom, provided that they do not simultaneously become a hydrogen atom or a halogen atom, and R ₁ and R ₂ represent an alkyl group having 5 to 18 carbon atoms, and at least One alkyl group is an optically active alkyl group containing an asymmetric carbon atom represented by the following formula, Here, * represents an asymmetric carbon atom, n is an integer of 1 to 5 when X is a hydrogen atom and Y is a halogen atom, and n is 2 to 2 when X is a halogen atom and Y is a hydrogen atom. Which is an integer of 5) and a composition containing the liquid crystal.

The compound of the present invention is typically synthesized by the following synthetic route.

(R ₁ , R ₂ , X and Y are the same as above) That is, 4-substituted phenol and 2 or 3-substituted-4
-Hydroxybenzoic acid was reacted in the presence of concentrated sulfuric acid and boric acid in a toluene solvent to give a 2 or 3-substituted-4-hydroxybenzoic acid 4'-substituted phenyl ester (step
I) and then 4-substituted benzoic acid with N, N'-dicyclohexylcarbodiimide (hereinafter abbreviated as DCC) and 4
-Pyrrolidinopyridine (hereinafter abbreviated as PRLPY) is synthesized by esterification (step II) in the presence of. In addition, as the esterification method, other generally known esterification methods can be used.

Many of the compounds of the present invention exhibit the SC ^* phase, and are characterized in that the temperature range thereof reaches a relatively high temperature of about 50 to 110 ° C.

Therefore, it is suitable for extending the upper limit of the temperature range of the SC ^* phase of the liquid crystal composition.

The liquid crystal composition of the present invention may be composed of one or more compounds of the general formula (I), or may be a liquid crystal composition exhibiting an SC ^* phase at room temperature by mixing the compound of the general formula (I) with another smectic liquid crystal. It is also possible to construct an object, and both exhibit ferroelectricity.

Further, when a compound which does not exhibit the SC ^* phase in the general formula (I) is used as a so-called liquid crystal compound in combination with a compound which exhibits the SC ^* phase in the general formula (I), the same effect as a liquid phase composition can be expected.

(Example) Hereinafter, the production methods and physical properties of representative compounds will be specifically shown in Examples. In the examples, C is a crystalline phase, SA is a smectic A phase, SC ^* is a chiral smectic C phase, ch is a cholesteric (chiral nematic) phase, and I is an isotropic liquid. The value in parentheses indicates the monotropic phase transition temperature.

Example 1 2-Chloro-4- (4'-octyloxybenzoyloxy) benzoic acid 4 "-(S-(+)-2-methylbutyl) oxyphenyl ester (in general formula (I) (I) 2-chloro-4-hydroxybenzoic acid-4 '-(S
Preparation of-(+)-2-methylbutyl) oxyphenyl ester: 4- (S-(+)-2-methylbutyl) oxyphenol 13g, 2-chloro-4-hydroxybenzoic acid 10.
A mixture of 2 g, concentrated sulfuric acid 250 mg and boric acid 150 mg was added to toluene 300 m.
Stir with l, distilling off the water produced by the reaction 4
The mixture was heated under reflux for 0 hours. After toluene was distilled off under reduced pressure, the residue was recrystallized twice from acetonitrile to obtain 144 g of colorless needle crystals as the desired product. Yield 73%, melting point
The temperature was 148.6-149.2 ° C.

(ii) Esterification: 2-chloro-4-hydroxybenzoic acid 4 ′-(S-(+)-2-methylbutyl) oxyphenyl ester obtained in (i) 1.0 g and 4-octyloxybenzoic acid 740 mg, DCC630mg, PRLPY50mg to methylene chloride 30
It was dissolved in mg and stirred at room temperature for 10 hours. By-produced N, N′−
After separating dicyclohexylurea, the organic layer was washed with 5% hydrochloric acid, 5% aqueous sodium hydroxide solution and water in this order, and dried with anhydrous magnesium sulfate. After distilling off methylene chloride, the remaining crystals were purified by silica gel column chromatography using benzene as an eluent. Further, the obtained crystals were mixed with ethanol-ethyl acetate (10: 1V /
V) was recrystallized twice to give 1.27 g of the target 2-chloro-4- (4'-octyloxybenzoyloxy).
Benzoic acid 4 "-(S-(+)-2-methylbutyl) oxyphenyl ester was obtained as colorless needle crystals. Yield 75%. This product had a C-SA point of 74.9 ° C and an SA-ch point of 100.8 ° C.
The ch-I point was 124.0 ° C.

Example 2 2-Chloro-4- (4'-decyloxybenzoyloxy) benzoic acid 4 "-(S-(+)-2-methylbutyloxyphenyl ester (in general formula (I) Preparation of Example 2 (ii) In the esterification in Example 2, except that decyloxybenzoic acid was used instead of octyloxybenzoic acid, the procedure was carried out according to the method shown in Example 2 (ii). Chloro-4- (4'-decyloxybenzoyloxy) benzoic acid 4 "-(S-(+)-2-methylbutyl) oxyphenyl ester was obtained.

This one has C-SA point 64.0 ℃ SA-ch point 109.9 ℃ ch-I
The point was 120.0 ° C SC ^* -SA point (54.4 ° C).

Example 3 2-chloro-4- (4'-undecyloxy benzoyloxy) benzoic acid 4 "- by (S - - (+) 2-methylbutyl) oxy-phenyl ester (formula (I) R ₁ = C ₁₁ H
₂₃ , X = H, Y = Cl) According to the method of (ii) of Example 2, except that octyloxybenzoic acid was replaced with undecyloxybenzoic acid in the esterification of (ii) of Example 2. 2-chloro-4- (4'-undecyloxybenzoyloxy) benzoic acid 4 "-(S-(+)-2-methylbutyl) which is the object of the operation
Oxyphenyl ester was obtained.

This product had a C-SC ^* point of 60.4 ° C., a SC ^* -SA point of 66.3 ° C., an SA-ch point of 111.5 ° C., a ch-I point of 118.9 ° C. Example 4 2-chloro-4- (4′-dodecyloxybenzoyloxy) benzoic acid 4 ″-(S-(+)-2-methylbutyl) oxyphenyl ester (in the general formula (I), R ₁ ═C ₁₂ H
₂₅ , X = H, Y = Cl) The procedure of Example 2 (ii) was repeated except that octyloxybenzoic acid was replaced with dodecyloxybenzoic acid during the esterification in Example 2 (ii). The desired 2-chloro-4- (4′-dodecyloxybenzoyloxy) benzoic acid 4 ″-(S-(+)-2-methylbutyl) oxyphenyl ester was obtained.

This is C-SC ^* point 60.1 ℃ SC ^* -SA point 72.7 ℃ SA-
The ch point was 113.7 ° C and the ch-I point was 116.4 ° C.

Example 5 2-chloro-4- (4'-decyloxy-benzoyloxy) benzoic acid 4 "- by (S - - (+) 2-methylbutyl) oxy-phenyl ester (formula (I) R ₁ = C ₁₃ H
₂₇ , X = H, Y = Cl) According to the method of (ii) of Example 2, except that octyloxybenzoic acid was replaced with tridecyloxybenzoic acid in the esterification of (ii) of Example 2. 2-chloro-4- (4'-tridecyloxybenzoyloxy) benzoic acid 4 "-(S-(+)-2-methylbutyl) which is the object of the operation
Oxyphenyl ester was obtained.

This is C-SC ^* point 64.2 ℃ SC ^* -SA point 72.7 ℃ SA-
The ch point was 113.7 ° C and the ch-I point was 116.4 ° C.

Example 6 2-chloro-4- (4'-tetradecyloxy benzoyloxy) benzoic acid 4 "- by (S - - (+) 2-methylbutyl) oxy-phenyl ester (formula (I) R ₁ = C
₁₄ H ₂₉ , X = H, Y = Cl) According to the method of (ii) of Example 2, except that tetradecyloxybenzoic acid was used instead of octyloxybenzoic acid in the esterification in (ii) of Example 2. Operation was performed to obtain the desired 2-chloro-4- (4'-tetradecyloxybenzoyloxy) benzoic acid 4 "-(S-(+)-2-methylbutyl) oxyphenyl ester.

This is C-SC ^* point 65.6 ℃ SC ^* -SA point 74.0 ℃ SA-
ch point 114.6 ° C. ch-I point 114.8 ° C. Example 7 2-chloro-4- (4′-hexadecyloxybenzoyloxy) benzoic acid 4 ″-(S-(+)-2-methylbutyl) oxyphenyl ester (general) In the formula (I), R ₁ = C
₁₆ H ₃₃ , X = H, Y = Cl) According to the method of (ii) of Example 2, except that hexadecyloxybenzoic acid was used instead of octyloxybenzoic acid in the esterification of (ii) of Example 2. The purpose of the operation is 2-
Chlor-4- (4′-hexadecyloxybenzoyloxy) benzoic acid 4 ″-(S-(+)-2-methylbutyl) oxyphenyl ester was obtained.

This has a C-SA point of 71.3 ° C SA-I point of 113.9 ° C SC ^* -S
Point A (66.9 ° C.) Example 8 2-chloro-4- (4′-octadecyloxybenzoyloxy) benzoic acid 4 ″-(S-(+)-2-methylbutyl) oxyphenyl ester (in the general formula (I) R ₁ = C
₁₈ H ₃₇ , X = H, Y = Cl) The procedure of Example 2 (ii) was repeated except that octadecyloxybenzoic acid was used instead of octyloxybenzoic acid in the esterification of Example 2 (ii). Purpose of doing 2-
Chloro-4- (4'-octadecyloxybenzoyloxy) benzoic acid 4 "-(S-(+)-2-methylbutyl) oxyphenyl ester was obtained.

This had a C-SA point of 71.3 ° C and an SA-I point of 113.1 ° C.

EXAMPLE 9 3-chloro-4- (4'-octyloxy-benzoyloxy) benzoic acid 4 "- by (S - - (+) 4-methylhexyl) oxy phenyl ester (formula (I) R ₁ = C ₈ H
₁₇ , X = H, Y = Cl) (i) 3-chloro-4-hydroxybenzoic acid 4 '-(S-
Production of (+)-4-methylhexyl) oxyphenyl ester 5.3 g of 4- (S-(+)-4-methylhexyl) oxyphenol, 42 g of 3-chloro-4-hydroxybenzoic acid,
A mixture of 100 mg of concentrated sulfuric acid and 50 mg of boric acid was stirred with 100 ml of toluene, and the mixture was heated under reflux for 23 hours while distilling off water produced by the reaction. After the toluene was distilled off, the remaining crystals were recrystallized twice from acetonitrile to obtain 6.5 g of colorless needle crystals as the desired product. Yield 78%, melting point 135-136
It was ℃.

(ii) Esterification 3-chloro-4-hydroxybenzoic acid 4 ′-(S-(+)-4-methylhexyl) oxyphenyl ester obtained in (i) 1.0 g and octyloxybenzoic acid 690 mg DCC
Dissolve 570 mg and PRLPY 50 mg in 30 ml of methylene chloride at room temperature
Stir for 10 hours. Methylene chloride was distilled off under reduced pressure, and the residue was purified by silica gel column chromatography using benzene as an eluent.

The obtained crystals were added to ethanol-ethyl acetate (10: 1V
/ VB) and recrystallized twice, and 1.1 g of the target 2-chloro-4- (4'-octyloxybenzoyloxy) benzoic acid 4 "-(S-(+)-4-methylhexyl) oxyphenyl The ester was obtained by crystallization from colorless needles, yield 69.
%.

This had a C-ch point of 62.9 ° C and a ch-I point of 134.6 ° C.

Example 10 3-Chloro-4- (4′-decyloxybenzoyloxy) benzoic acid 4 ″-(S-(+)-4-methylhexyl) oxyphenyl ester (R ₁ ═C _{10 in the} general formula (I)) H
₂₁ , Preparation of (X = H, Y = Cl) According to the method shown in (ii) of Example 9 except that decyloxybenzoic acid was used instead of octyloxybenzoic acid in the esterification in (ii) of Example 9. The operation was performed to obtain the desired 3-chloro-4- (4'-decyloxybenzoyloxy) benzoic acid 4 "-(S-(+)-4-methylhexyl) oxyphenyl ester.

This is C-SC ^* point 67.7 ℃ SC ^* -ch point 70.2 ℃ ch-
The point I was 130.8 ° C.

Example 11 3-chloro-4- (4'-dodecyloxy-benzoyloxy) benzoic acid 4 "- by (S - - (+) 4-methylhexyl) oxy phenyl ester (formula (I) R ₁ = C ₁₂ H
₂₅ , X = Cl, Y = S) In the method shown in Example 9 (ii) except that octyloxybenzoic acid was replaced with dodecyloxybenzoic acid in the esterification in Example 9 (ii). The operation was performed according to the procedures described above to obtain the desired 4-chloro-4- (4'-dodecyloxybenzoyloxy) benzoic acid 4 "-(S-(+)-4-methylhexyl) oxyphenyl ester.

This is C-SC ^* point 73.1 ℃ SC ^* -ch point 87.7 ℃ ch-
The point I was 120.8 ° C.

Example 12 In the general formula (I) With R ₁ ═C ₁₂ H ₂₅ , Equivalent mixture with the compound of X = H and Y = Cl shows SC ^* phase up to 66.7 ℃, SA-ch point is 112.1 ℃, and it is an isotropic liquid above 112.1 ℃ and has suitable performance as a display device. .

A cell equipped with a transparent electrode having PVA applied and rubbing the surface with this mixture as an orientation treatment (cell thickness 5 μm)
And apply a DC voltage of 50 V to the S
A uniform monodomain cell was obtained by cooling very slowly (2 ° C./hr) until the C ^* phase was reached. This liquid crystal cell was inserted between two polarizers arranged in a crossed Nicol state, and when a 25 V low frequency (1 Hz) alternating current was applied, a clear switching operation was observed and the contrast was very good and the response speed was also high. A very fast (1.5 msec) liquid crystal display device was obtained.

The spontaneous polarization value Ps of this liquid crystal composition was 3 nC / cm ² .

Claims (2)

[Claims] 1. A liquid crystal compound represented by formula (I). (In the formula, X and Y represent a hydrogen atom or a halogen atom, provided that they do not simultaneously become a hydrogen atom or a halogen atom, and R ₁ and R ₂ represent an alkyl group having 5 to 18 carbon atoms, and at least One alkyl group is an optically active alkyl group containing an asymmetric carbon atom represented by the following formula, Here, * represents an asymmetric carbon atom, n is an integer of 1 to 5 when X is a hydrogen atom and Y is a halogen atom, and n is 2 to 2 when X is a halogen atom and Y is a hydrogen atom. It is an integer of 5) 2. A liquid crystal composition containing at least one liquid crystal compound represented by formula (I). (In the formula, X and Y represent a hydrogen atom or a halogen atom, provided that they do not simultaneously become a hydrogen atom or a halogen atom, and R ₁ and R ₂ represent an alkyl group having 5 to 18 carbon atoms, and at least One alkyl group is an optically active alkyl group containing an asymmetric carbon atom represented by the following formula, Here, * represents an asymmetric carbon atom, n is an integer of 1 to 5 when X is a hydrogen atom and Y is a halogen atom, and n is 2 to 2 when X is a halogen atom and Y is a hydrogen atom. It is an integer of 5)