JPH0643376B2 - Liquid crystalline compound - Google Patents

Description

TECHNICAL FIELD The present invention relates to a ferroelectric liquid crystal compound as a material for a large-sized display device, which is required to have a high-speed response particularly in the property utilization of the electro-optical effect of liquid crystal. It is a thing.

[Prior Art] Most of the liquid crystals that have been put to practical use are nematic,
Among them, the twisted nematic type (TN) has been mainly used for displays with a small number of pixels such as a clock, a wristwatch and a calculator, but the number of pixels is large (for example, the number of signal electrodes is 100).
As described above, when a screen having a relatively large display area is used, the contrast is lowered and the viewing angle is narrowed, so that it becomes impractical.

Two measures were taken to solve this problem. That is, the TN type with a twist angle of 90 ° is increased to 180 to 270 ° to increase the contrast, and a super twist nematic type (STN
The other was the development of a new drive system called an active matrix system that prevents the deterioration of contrast by incorporating transistors and diodes in each pixel.

With these solutions, LCD TVs with a screen size of 2 to 3 inches and a pixel number of 50,000 to 80,000 appear on the market, which is a momentum on the extension of research and development, and a display having a larger display area, such as a CRT. The goal was to set a flat display that could replace the.

However, in the nematic liquid crystal device, since the anisotropy of the dielectric constant is simply used as the driving force by the electric field E, only a small force of the paraelectric material is used, and a high-speed response of m · sec or more is difficult. It has become clear that the display capacity, responsiveness, and display quality are inherently limited in spite of various efforts to meet the required level of detail. On the other hand, ferroelectric liquid crystals have recently attracted attention and expectations as new liquid crystals.

Ferroelectric liquid crystal was synthesized by RB Meyer et al. In 1975 with p-decyloxybenzylden-p'-amino-2-methylbutyl cinnamate (DOBAMBC) (J. de Phys. L).
ett., 36 , 69, 1975), it was confirmed that the chiral smectic C phase is a ferroelectric substance having spontaneous polarization.

In 1980, NA Clark et al. (Appl.Phys.L
ett., 36 , 899, 1980), it is reported that DOBAMBC, which is one of the ferroelectric liquid crystal compounds in the thin film cell, exhibits high-speed switching characteristics of m · sec or less and has bistability.
The potential as an epoch-making display element material attracted attention. The characteristics of ferroelectric liquid crystals are high-speed response and memory property, but the high-speed property showing a response time of the order of μ · sec is unprecedented in other liquid crystals. Ferroelectricity is 1) having a dipole moment or a dipole moment component in the direction perpendicular to the long axis direction of the molecule in view of the structure of liquid crystal molecules, 2) the molecule is a chiral molecule having an optically active group, 3) It is expressed with spontaneous polarization only when the three conditions of being a smectic phase with a tilt angle are satisfied. The driving force of the element in the electric field E is the spontaneous polarization P _s (n
C / cm ² ), and its response speed τ is represented by τ = η / P _S · E (η is viscosity for precession motion with a constant tilt angle), and (MAHandschy .; Appl.Phys. Lett., 41 , 39,
1982), it is found that the spontaneous polarization must be large in order to obtain a fast response.

In addition, JP-A-61-208032, JP-A-61-231082, and JP-A-SHO
The following liquid crystal compounds have been reported in 61-243037 and the like. However, it must be said that it is still insufficient from the viewpoint of high-speed response.

[Problems to be Solved by the Invention] For practical application to devices and devices that utilize the electro-optical effect of ferroelectric liquid crystals, there are still problems such as alignment technology, cell configuration and mass production technology, and driving method. Although there are various problems required, the most important thing is the development of a fast response liquid crystal having a large spontaneous polarization in a wide temperature range.

The present invention seeks to meet this expectation.

[Means for Solving Problems] The occurrence of spontaneous polarization is due to the permanent dipole moment in the direction perpendicular to the long axis of the molecule. Approximately 1/30 of the expected value when the binding moment of> C = 0 is completely oriented
Shows only 0D. This phenomenon is because the rotation of the molecule is not constrained like a solid, it rotates freely, and the positions of the asymmetric carbon and the permanent dipole are separated,
It is said that the effective orientation of the dipole is canceled by rotation and vibration which are internal motions of the molecule, and spontaneous polarization is significantly reduced.

Therefore, in order to increase the spontaneous polarization, it is conceivable to bring the positions of the asymmetric carbon and the permanent dipole as close as possible, or to directly insert a halogen atom or a bond having a large polarization into the asymmetric carbon.

Under these circumstances, the present inventors have conducted various studies on the molecular structure including an optically active group in an effective liquid crystal compound having a large spontaneous polarization. As a result, the following general formula (I)
The present invention has been completed by finding that the compound represented by the formula (3) has a relatively large spontaneous polarization over a wide range.

That is, the present invention is a general formula showing ferroelectricity and excellent in high-speed response. (In the formula, R ₁ is an alkyl group having 6 to 12 carbon atoms, and ▲ R ^* ₂ ▼ is a branched alkylene group having a total carbon number of 3 to 5 and having an asymmetric carbon. ₃ represents an alkyl group having 1 to 6 carbon atoms, and n represents 0 or 1.).

Next, a general production method will be briefly described for the synthesis of the benzoic acid derivative (n = 1) of the general formula (I). In the formula, m is 0
2, THP represents tetrahydropyran, and Me represents a methyl group.

First, after protecting the hydroxyl group of oxyacid ester (2) with tetrahydropyran, the carboxyl group is reduced to methylol with lithium aluminum hydride and treated with alkyl iodide to give the ether compound of (5). obtain.
The alcohol (6) obtained by removing the protecting group is reacted with acetoxybenzoic acid chloride to obtain a benzoic acid derivative (7). Benzylamine is added to this to decompose it, and the phenol derivative of (8) is obtained. Next, the separately prepared alkoxybiphenylcarboxylic acid and the phenol derivative (8) are subjected to an esterification reaction to obtain an ester of the general formula (I).

Next, a general production method will be briefly described for the synthesis of the phenol derivative (n = 0) of the general formula (I). Where m is 0
~ 2, Me represents a methyl group.

The oxyacid ester (2) is converted to methanesulfonylalkyl lactate (9) with methanesulfonyl chloride. Then, it is reacted with benzyloxyphenol to obtain the compound (10). This is reduced with lithium aluminum hydride to obtain the alcohol compound (11). The alcohol body is reacted with alkyl iodide to obtain an ether body (12). Then, hydrogenate with palladium carbon under normal pressure to
(13) The phenol body (13) is reacted with an alkoxybiphenylcarboxylic acid chloride to obtain an ester of the general formula (I).

Representative examples of the liquid crystal compound represented by the general formula (I) are shown below.

(1) (2) (3) (Four) (Five) (6) (7) (8) (9) (Ten) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (twenty one) (twenty two) The liquid crystalline compound according to the present invention can be used in combination with an existing ferroelectric liquid crystal or a compound that does not exhibit ferroelectricity and goes through a simple S _C phase to expand the temperature range of the S _C ^* phase,
It is possible to obtain a liquid crystal composition that can be practically used for displays and the like. Further, also poor liquid crystalline compounds according to the present invention, the compound through the S _C phase or S _C ^* phase 5-20
%, It is possible to obtain a ferroelectric liquid crystal composition having a large spontaneous polarization.

[Examples] Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples, and Application Examples.

Example 1 Synthesis of 3-hydroxybutyl ethyl ether 6 g of 3-hydroxybutyric acid methyl ester and 5 g of 2,3-dihydropyran were reacted in ether to obtain 10.5 g of a protected ester. This was placed in 150 ml of a tetrahydrofuran solution, 1.5 g of lithium aluminum hydride was added, and the mixture was reduced at room temperature for methylolation to obtain 8.7 g of a product. Next, take 7.0 g of this and add 80 ml of tetrahydrofuran.
Ethyl iodide (11.6 g) was reacted with lithium hydride (3 g) to obtain an ether compound (7 g). This was put in 7 ml of methanol and the protecting group was removed with 30 mg of p-toluenesulfonic acid to obtain 4 g of the target compound (theoretical yield: 63.5).
%).

Example 2 p-Hydroxybenzoic acid (1-methyl-3-ethoxy)
Synthesis of Propyl Ester First, 5 g of acetoxybenzoic acid was chlorinated with 19.8 g of thionyl chloride, and excess thionyl chloride was distilled off. Then, the total amount and the ether derivative 4 g obtained in Example 1, pyridine
2.6 g was reacted in 50 ml of toluene at 0-5 ° C for 1 hour and then at room temperature for 2 hours. Then, it was diluted with water, neutralized with acidic sodium carbonate, washed well with saturated saline, and then toluene was recovered to obtain 7.4 g of p-acetoxybenzoic acid (1-methyl-3-ethoxy) propyl ester. (Theoretical yield 82.5%).

Next, dissolve it in 25 ml of ethanol, cool it, add 2.8 g of benzylamine, react at 20-25 ° C for 2 hours, distill off ethanol, dissolve in a mixed solvent of chloroform and methanol, and pass through a silica gel column. purity
3.3 g of the target compound (99%) was obtained (theoretical yield: 63.6%).

Example 3 4- (4'-n-octyloxybiphenyl-4-carbonyloxy) benzoic acid (1-methyl-3-ethoxy)
Synthesis of Propyl Ester 1.5 g of the benzoic acid derivative obtained in Example 2 and 1.58 g of n-octyloxybiphenylcarboxylic acid were mixed with 50 ml of dichloromethane.
It was dissolved in ml, a small amount of dimethylaminopyridine and dicyclohexylcarbodiimide were added thereto, and the mixture was reacted at room temperature for 2 hours. Dichloromethane was distilled off to obtain 5.4 g of a crude product. This was dissolved in a mixed solvent of chloroform and methanol, passed through a silica gel column, and recrystallized with ethanol to give 4- (4'-n-octyloxybiphenyl-4-carbonyloxy) benzoic acid (1- Methyl-3-ethoxy) propyl ester 1.8 g (theoretical yield 68.
7%) (Exemplified Compound 5) was obtained.

The analytical values of this compound are shown below.

Specific rotation: [α] ▲ ²⁴ _D ▼ ＝ 31.8 ° NMR: 0.90 (3H, t, J = 6.9Hz), 1.17 (3H, t, J = 7.0Hz), 1.83
(11H, m), 1.48 (2H, m), 1.81 (2H, m), 1.92 (1H, m), 2.05 (1H,
m), 3.5 (4H, m), 4.02 (2H, m), 5.32 (1H, m), 7.01 (2H, m), 7.32
(2H, m), 7.58 (2H, m), 7.70 (2H, m), 8.14 (2H, m), 8.23 (2H, m) Example 4 4- (4'-n-hexyloxybiphenyl-4- Carbonyloxy) benzoic acid (1-methyl-3-ethoxy)
Synthesis of propyl ester 4- (4'-n-hexyloxybiphenylcarboxylic acid
1.45 g and the parahydroxybenzoic acid derivative obtained in Example 2
After reacting with 1.5 g in the same manner as in Example 3, purification and recrystallization were performed to give 4- (4'-n-hexyloxybiphenyl-4-carbonyloxy) benzoic acid (1-
Methyl-3-ethoxy) propyl ester (1.95 g, theoretical yield 77.0%) was obtained (Exemplary Compound 4).

Example 5 Synthesis of ethyl 2- [4- (benzyloxy) phenoxy] propionate (s) -Ethyl lactate 303 g, 350 ml of ether and 400 ml of pyridine were mixed to give a solution of methanesulfonyl chloride 350.
g at room temperature. After reacting for 3 hours, the reaction solution is poured into water and extracted with ether. The ether layer was washed with water, dried and distilled under reduced pressure to obtain methanesulfonylethyl lactate.

A solution of 235 g of this methanesulfonylethyl lactate in 240 ml of ethanol was added to benzyloxyphenol 2
After 40 g, caustic potash 162 g, water 190 ml, and ethanol 1.2 were mixed with stirring, the mixture was added dropwise at room temperature and then reacted under reflux for 4 hours. Then, after distilling off ethanol, water 3 was added to dilute, and the mixture was extracted and washed with ether. The aqueous layer was weakly acidified with hydrochloric acid, extracted with ethyl acetate, washed with water, dried and concentrated under reduced pressure to obtain 240 g of a crude product. This was recrystallized from benzene to obtain 125 g (theoretical yield: 38.3%) of the target compound having a melting point of 133 to 134 ° C.

Example 6 Synthesis of 2- (4-hydroxyphenoxy) propyl ethyl ether 26 g of lithium aluminum hydride was suspended in tetrahydrofuran 1.1 in a nitrogen gas stream, and the temperature was 10 to 15 ° C.
To this solution, 169 g of ethyl 2- [4- (benzyloxy) phenoxy] propionate obtained in Example 5 was maintained.
Was added dropwise to 340 ml of tetrahydrofuran over 2.5 hours. After stirring at room temperature for 1 hour, lithium aluminum hydride was decomposed with methanol, 600 ml of water was added to dilute, and the mixture was extracted with ether. The ether layer was washed with water, dried and concentrated to obtain 139 g of a crude product. This was recrystallized from heptane to obtain 97 g of 2- (4-benzyloxyphenoxy) propyl alcohol having a melting point of 43 to 44 ° C. Take 85g of this alcohol and use tetrahydrofuran 21
Dissolve in 0 ml and pass through nitrogen gas while sodium hydride 1
7 g was suspended, 66.7 g of ethyl iodide was added dropwise, the mixture was reacted for 2 hours while maintaining the liquid temperature at 50 to 60 ° C., and then tetrahydrofuran was distilled off. Add 300 ml of water, extract with benzene, wash the benzene layer with water, dry, and concentrate under reduced pressure to 92 g.
2- (4-benzyloxyphenoxy) propyl ethyl ether was obtained. 48 g of this ether was taken, dissolved in 400 ml of methanol, 4 g of 10% palladium carbon was suspended, and hydrogenated at about 50 ° C. for 6 hours under normal pressure. After separating the catalyst,
Concentration under reduced pressure gave 32 g of crude 2- (4-hydroxyphenoxy) propyl ethyl ether. This was purified by column chromatography using 600 g of silica gel to obtain 24- (2-hydroxyphenoxy) propylethyl ether (24 g, theoretical yield: 16.4%). The gas chromatographic purity of this product is 99%
Met.

Example 7 Synthesis of 4- [4 '-(decyloxybiphenyl) carboxy] phenyl (1-methyl-2-ethoxy) ethyl ether 3.92 g of 2- (4-hydroxyphenoxy) propyl ethyl ether obtained in Example 6 was obtained. Dissolve in 30 ml of toluene and add 2.37 g of pyridine to a solution of 7.4 g in 10 ml of toluene.
-A solution in which decyloxybiphenylcarboxylic acid chloride was dissolved was added, and the mixture was reacted at 80 to 90 ° C for 3 hours. After completion of the reaction, the mixture was poured into water, separated, the organic layer was washed with water, dried and concentrated under reduced pressure to obtain 10.6 g of a crude target compound. This was chromatographically purified using 30 g of silica gel and further recrystallized with ethanol to give purified 4- [4′-
(Decyloxybiphenyl) carbooxy] phenyl (1-methyl-2-ethoxy) ethyl ether 6.1 g
(Theoretical yield 57.3%) (Exemplary compound 14) was obtained.

The analytical values of this compound are shown below.

^{_{M S: 532 (M *)}} NMR: 0.91 (3H, t, J = 8.7Hz), 1.48 (22H, m), 1.82 (2H, m), 3.
08 (4H, m), 3.98 (2H, m), 4.53 (1H, m), 6.97 (4H, m), 7.13 (2H,
m), 7.57 (2H, m), 7.70 (2H, m), 8.22 (2H, m) Example 8 4- [4 '-(octyloxybiphenyl) carbooxy] phenyl (1-methyl-2-ethoxy) ethyl Synthesis of ether The procedure of Example 7 was repeated except that 6.87 g of 4-octyloxybiphenylcarboxylic acid chloride was used in place of 4-decyloxybiphenylcarboxylic acid chloride, and 4- [4'- having a melting point of 64 ° C. 7.2 g (theoretical yield 71.4%) of (octyloxybiphenyl) carbooxy] phenyl (1-methyl-2-ethoxy) ethyl ether (Exemplary compound 13) was obtained.

The analytical values of this compound are shown below.

^{_{M S: 504 (M *)}} NMR: 0.91 (3H, t, J = 7.0Hz), 1.36 (18H, m), 1.82 (2H, m), 3.
50 (4H, m), 4.02 (2H, m), 4.53 (1H, m), 6.98 (4H, m), 7.13 (2H,
m), 7.58 (2H, m), 7.67 (2H, m), 8.23 (2H, m) Example 9 4- [4 '-(hexyloxybiphenyl) carbooxy] phenyl (1-methyl-3-butoxy) propyl Synthesis of ether Using methyl 3-hydroxybutyrate in place of the starting lactate ester, the same procedure as in Example 5 was repeated to give 3- [4
-(Benzyloxy) phenoxy] methyl butyrate,
Treatment with lithium aluminum hydride gave a butanol derivative. Then, replace butyl iodide with ethyl iodide,
4- [4 ′-(hexyloxy) having a melting point of 85 ° C. was operated in the same manner as in Examples 6 and 7, except that 4-hexyloxybiphenylcarboxylic acid chloride was used in place of 4-decyloxybiphenylcarboxylic acid chloride. Biphenyl) carboxy] phenyl (1-methyl-3-butoxy) propyl ether (Exemplary Compound 21) was obtained.

Example 10 Synthesis of 4- [4 '-(octyloxybiphenyl) carboxy] phenyl (1-methyl-3-butoxy) propyl ether Example 5 Methyl 3-hydroxybutyrate was used instead of the starting lactate ester. Perform the same operation as in 3- [4
-(Benzyloxy) phenoxy] methyl butyrate,
Treatment with lithium aluminum hydride gave a butanol derivative. Then, the same procedure as in Examples 6 and 7 was carried out except that 4-octyloxybiphenylcarboxylic acid chloride was used in place of 4-decyloxybiphenylcarboxylic acid chloride, and after column purification, recrystallization with ethanol was performed. 4- [4 '-(octyloxybiphenyl) carboxy] phenyl (1-methyl-3- with a melting point of 45 ° C
Ethoxy) propyl ether (Exemplary compound 19) was obtained (theoretical yield 44.6%).

The analytical values of this compound are shown below.

Specific rotation: [α] ▲ ²⁴ _D ▼ = -17.73 ° Example 11 4- (4'-n-octyloxybiphenyl-4-carbonyloxy) benzoic acid (1-methyl-) obtained in Example 3
Liquid crystal properties were measured for 3-ethoxy) propyl ester.

After providing a transparent electrode on the glass plate, further coating the polymer on it, and rubbing it in a certain direction,
A liquid crystal cell was obtained by assembling two substrates so that the rubbing directions were parallel to each other and using spacers to a certain thickness. The thickness of the cell is 3 μm.

This compound was injected into this cell, a helium-neon laser and a photomultiplier tube were used, and a square wave AC of ± 20 V was applied, and the electro-optical effect of the liquid crystal was observed. A response was confirmed, and it was confirmed that the material could be used as a liquid crystal display device.

On the other hand, the phase transition temperature was determined by observation with a differential scanning calorimeter and a polarizing microscope. Note that S ₁ is an undetermined liquid crystal phase.
The results of these measurements are shown in Table 1.

Examples 12 to 18 The phase transition temperature and various characteristic values of the compound of the present invention were measured in the same manner as in Example 11. The results are shown in Table-1.

Comparative Examples 1 and 2 DM Walba et al. (JACS, 108 , 5210, 1986), which are compounds reported, having the chemical structure relatively similar to that of the liquid crystalline compound of the present invention,
The phase transition temperature and various characteristic values were measured in the same manner as in Example 11. The results are shown in Table-1.

Comparative compound-1 Comparative compound-2 These compounds show the S _C ^* phase at a relatively low temperature, but the spontaneous polarization is small and the response speed is not so fast. On the other hand, the liquid crystalline compound of the present invention has a slightly higher S _C ^* phase appearance temperature, but is excellent in spontaneous polarization and response speed.

Application Examples 1 to 3 In a display device, various liquid crystal compounds were mixed in order to obtain a liquid crystal composition exhibiting a high-speed response over a wider range of actual use temperatures, and the performance thereof was investigated. In addition, the response characteristics as a liquid crystal display device were evaluated by using the liquid crystalline compounds obtained in the examples. The measurement direction was the same as in Example 11. Typical examples are shown in Table-2.

[Effects of the Invention] The liquid crystalline compound of the present invention exhibits high-speed response in image display and exhibits ferroelectricity in a wide temperature range, and thus meets future needs for high-density and large-sized displays. It is possible.

Claims (1)

[Claims] 1. A general formula (In the formula, R ₁ is an alkyl group having 6 to 12 carbon atoms, R ₂ ^* is a branched alkylene group having a total carbon number of 3 to 5 and having an asymmetric carbon, and R ₃ is A liquid crystal compound represented by C1 to C6 alkyl group, and n represents 0 or 1.).