JPH068265B2 - 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. Ie 1
One is a super twisted nematic type (ST with a twist angle of 90 ° that increases the contrast by increasing it to 180-270 °).
The other was the development of a new drive system called an active matrix system, which prevents deterioration of contrast by incorporating a transistor or a diode in each pixel.

With these solutions, LCD TVs with a screen size of 2 to 3 inches and a pixel count of 50,000 to 80,000 appear on the market, and as a result of the momentum of research and development, a display with a larger display area, such as a CTR, is displayed. 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. Despite various efforts to meet the required level of detail, it became clear that the display capacity, responsiveness, and display quality are inherently limited. On the other hand, ferroelectric liquid crystals have recently attracted attention and expectations as new liquid crystals.

Ferroelectric liquid crystals are described in R.I. B. P- in 1975 by Meyer et al.
Decyloxybenzylidene-p'-amino-2-methylbutyl cinnamate (DOBAMBC) was synthesized (J. de Phys. Le
tt., 36 , 69, 1975), it was confirmed that the chiral smectic C phase is a ferroelectric substance having spontaneous polarization.

Also, in 1980, N. A. Clark et al. (Appl.Phy
s.Lett., 36 , 899, 1980), DOBAMBC, which is one of the ferroelectric liquid crystal compounds in a thin film cell, exhibits high-speed switching characteristics of m / sec or less, and is reported to have 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) Smectic phase with tilt angle,
It is expressed with spontaneous polarization only when these three conditions are satisfied. The driving force of the element in the electric field E is the spontaneous polarization P _s.
(nC / cm ² ), and its response speed τ is represented by τ = η / P _s · E (η is the viscosity for precession motion with a constant tilt angle) (MAHandschy.; Appl.Phys. Lett., 41 , 39,198
2) It can be seen that spontaneous polarization must be large in order to obtain 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 = O is perfectly oriented
Shows only 0D. This phenomenon is an internal motion of the molecule because the rotation of the molecule is not bound like a solid, so it rotates freely, and the asymmetric carbon and permanent dipole are distant from each other. It is said that the effective orientation of the dipole is canceled by the rotation and the vibration, and the 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 a compound represented by the formula (1) 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 represents an alkyl group having 6 to 12 carbon atoms, R ² represents a linear or branched alkyl group having 1 to 6 carbon atoms,
n represents 0 or 1. ) Is to provide a liquid crystal compound.

Next, a general production method will be briefly described for the synthesis of the benzoic acid derivative (n = 1) of the general formula (I).

Acetoxybenzoic acid chloride was added to a toluene solution of a diol of the formula (II) to react it with benzoic acid derivative (II
I) and then alkoxylated with alkyl iodide to give compound (I
V) get. Next, a phenol derivative (V) is obtained by reacting benzylamine dropwise with the alcohol solution. Next, the separately prepared alkoxybiphenylcarboxylic acid and the phenol derivative (V) are reacted and condensed with dicyclohexylcarbodiimide (DCC) 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).

Acetoxylation of diol (II) with acetyl chloride in toluene gives alcohol (3), which is then alkoxylated with alkyl iodide, and then potassium hydroxide is added to the concentrate to saponify the alcohol (5). ). This is converted to a tosylate (6) with toluenesulfonyl chloride, and then this is added dropwise to an ethanol solution of hydroquinone benzyl ether, followed by hydrogenation with palladium carbon under normal pressure to obtain a phenol derivative (8). next,
Separately prepared alkoxybiphenylcarboxylic acid and phenol derivative (8) were combined with dicyclohexylcarbodiimide (D.
Reaction condensation with CC) gives the ester of general formula (I).

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

Exemplified compound The liquid crystal compound of the present invention is used as a liquid crystal that can be practically used for displays, etc. by expanding the temperature range of the Sc ^* phase by mixing it with an existing ferroelectric liquid crystal or a compound that does not show ferroelectricity and goes through a simple Sc phase. A composition can be obtained. Further, even if the compound of the present invention has poor liquid crystallinity,
A ferroelectric liquid crystal composition having a large spontaneous polarization can be obtained by adding about 5 to 20% to a compound passing through the Sc phase or Sc ^* phase.

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

Example 1 4- (4'-n-octyloxybiphenyl-4-carbonyl) oxyphenyl-3-isopropyloxy-1
-Synthesis of methyl butyl ether (+)-(2S, 4S) -pentanediol 10.4g, pyridine 9.5
g and 70 ml of toluene were stirred, and 7.5 g of acetyl chloride was added dropwise while maintaining the temperature at 20 ° C. After the dropping was completed, stirring was continued for 2 hours, and then the reaction solution was poured into ice water. After liquid separation, the organic layer was dried and distilled to obtain 9.2 g of 4-acetoxypentan-2-ol.

4-acetoxypentan-2-ol 9.0 g, silver oxide 21.3
g, isopropyl iodide 20.9g, ether 60m at room temperature 3
Stir for hours. After passing through the precipitate and concentrating the liquid, 5.0 g of potassium hydroxide, 30 m of ethanol, 5 m of water were added to this.
Was added and the mixture was heated under reflux for 1 hour. Then, it was cooled and extracted with ether. The ether solution was concentrated, and the concentrate was purified by silica gel column chromatography (chloroform was used as a developing solvent) to obtain 5.2 g of 4-isopropyloxypentan-2-ol.

5.0 g of this 4-isopropyloxypentan-2-ol
And 20 m of pyridine were mixed and stirred, and 7.2 g of p-toluenesulfonyl chloride was added while maintaining the temperature at 0 to 5 ° C, and stirring was continued for 4 hours. After the reaction was completed, this was added to 30 m of ice water,
After extraction with -hexane, the hexane solution was dried and concentrated to obtain tosylate.

Hydroquinone benzyl ether 5.3g, potassium hydroxide
While heating and refluxing 1.6 g, ethanol 30 m, and water 1 m, tosylate was added dropwise thereto. After refluxing for 2 hours,
After cooling, 50 m of water was added and the mixture was extracted with ether. After concentrating the ether solution, 0.5 g of 10% palladium carbon and 50 m of ethanol were added, and hydrogenation was carried out at room temperature under normal pressure to obtain 3.0 g of hydroquinone-3-isopropyloxy-1-methylbutyl ether.

4-n-octyloxybiphenyl-4-carboxylic acid 4.
Dichloromethane 50m was added to 0g, hydroquinone-3-isopropyloxy-1-methylbutyl ether 2.9g, N, N'-dicyclohexylcarbodiimide 2.8g, and 4-dimethylaminopyridine 0.2g, and the mixture was stirred for 2 hours. After completion of the reaction, the reaction solution was passed and the solution was concentrated. The product was purified by silica gel column chromatography (chloroform was used as a developing solvent) to give a 4-mp melting point of 59 ° C.
6.4 g (theoretical yield 96.2%, Exemplified Compound 7) of (4'-n-octyloxybiphenyl-4-carbonyl) oxyphenyl-3-isopropyloxy-1-methylbutyl ether was obtained.

The analytical values of this compound are shown below.

Specific rotation: ▲ [α] ²⁵ _D ▼ = 3.02 ° Ms: 546 (M ⁺ ) NMR: 0.90 (3H, t, J = 6.9Hz), 1.16 (9H, m), 1.31 (8H, m), 1.34 (3H, d), 1.49 (2H, m), 1.55 (1H, m), 1.81 (2H, m), 2.08 (1H, m), 3.67 (2H, m), 4.02 (2H, t, J = 6.58 HZ), 4.49 (1H, m), 6.98 (4H, m), 7.13 (2H, m), 7.58 (2H, m), 7.69 (2H, m), 8.23 (2H, m) Example 2 4- ( Synthesis of 4'-n-octyloxybiphenyl-4-carbonyl) oxyphenyl-3-ethoxy-1-methylbutyl ether The procedure of Example 1 was repeated using ethyl iodide instead of isopropyl iodide. 4- (4'- with a melting point of 55 ° C
n-octyloxybiphenyl-4-carbonyl) oxyphenyl-3-ethoxy-1-methylbutyl ether
5.9 g (theoretical yield 95.6%) (Exemplified compound 4) was obtained.

Example 3 4- (4'-n-octyloxybiphenyl-4-carbonyl) oxyphenyl-3- (1-methylpropyl)
Synthesis of oxy-1-methylbutyl ether 2-iodobutane was used in place of isopropyl iodide in Example 1, and the same procedure as in Example 1 was carried out to obtain 4-oxyethylene having a melting point of 48 ° C.
6.2 g of (4'-n-octyloxybiphenyl-4-carbonyl) oxyphenyl-3- (1-methylpropyl) oxy-1-methylbutyl ether (theoretical yield 90.9%)
(Exemplified compound 9) was obtained.

Example 4 4- (4'-n-octyloxybiphenyl-4-carbonyl) oxybenzoic acid-3-isopropyloxy-1
-Synthesis of methyl butyl ester (+)-(2S, 4S) -pentanediol 10.4g, pyridine 9.5g,
70 m of toluene was stirred, and 17.3 g of 4-acetoxybenzoic acid chloride was added dropwise while maintaining at 0 to 5 ° C. After the dropping was completed, stirring was continued for 2 hours, and then the reaction solution was poured into ice water. After liquid separation, the organic layer was dried and concentrated, and the concentrate was purified by silica gel column chromatography (chloroform was used as a developing solvent) to obtain 16.1 g of 4- (4
-Acetoxybenzoyl) oxypentan-2-ol was obtained.

4- (4-acetoxybenzoyl) oxypentane-2
-All 15.0g, silver oxide 20.8g, isopropyl iodide 20.4
g and 60 m of ether were stirred at room temperature for 3 hours. After precipitation, the solution was concentrated to obtain 13.1 g of 4-acetoxybenzoic acid-3-isopropyloxy-1-methylbutyl ester.

4-acetoxybenzoic acid-3-isopropyloxy-1
50 ml of ethanol was added to 13.0 g of methyl butyl ester, and 13.6 g of benzylamine was added dropwise at 10 ° C. with stirring. The mixture was stirred at room temperature for 5 hours and then concentrated. The concentrate was purified by silica gel column chromatography (benzene: ethyl acetate = 30: 1 was used as a developing solvent).
8.4 g of 4-hydroxybenzoic acid-3-isopropyloxy-1-methylbutyl ester was obtained.

4-n-octyloxybiphenyl-4-carboxylic acid 1
0.1 g, 4-hydroxybenzoic acid-3-isopropyloxy-1-methylbutyl ester 8.2 g, N, N'-dicyclohexylcarbodiimide 6.4 g, and 4-dimethylaminopyridine 0.4 g were added with dichloromethane 100 m and stirred for 2 hours. After completion of the reaction, the reaction solution was passed and the solution was concentrated. The concentrate was purified by silica gel column chromatography (chloroform was used as a developing solvent) to give a melting point of 7
4- (4'-n-octyloxybiphenyl-at 6.8 ° C
4-Carbonyl) oxybenzoic acid-3-isopropyloxy-1-methylbutyl ether 14.1 g (theoretical yield 79.7
%) (Exemplified Compound 17) was obtained.

The analytical values of this compound are shown below.

Specific rotation: [α] ▲ ²⁵ _D ▼ = + 47.4 ° Ms: 576 (M ⁺ ) NMR: 0.90 (3H, t, J = 6.8Hz), 1.04 (3H, d, J = 6.1Hz), 1.13 (3H, d, J = 6.1Hz), 1.17 (3H, d, J = 6.1Hz), 1.48 ~ 1.44 (11H, m), 1.48 (2H, m), 1.72 ~ 1.82 (4H, m), 3.60 ( 2H, m), 4.02 (2H, t, J = 6.6Hz), 5.34 (1H, m), 7.01 (2H, m), 7.32 (2H, m), 7.58 (2H, m), 7.70 (2H, m ), 8.12 (2H, m), 8.25 (2H, m) Example 5 4- (4′-n-octyloxybiphenyl-4-carbonyl) oxyphenyl-3-isopropyloxy-1-obtained in Example 1 Liquid crystal properties were measured for methyl butyl ether. A transparent electrode is provided on the glass plate, a polymer is further coated on it, and it is rubbed in a certain direction. Then, the rubbing directions of the two substrates are made parallel, and a certain thickness is used by using a spacer. The assembled liquid crystal cell was used as a liquid crystal cell. The thickness of the cell is 3 μm.

This compound was injected into this cell, a square wave AC of ± 20 V was applied using a helium-neon laser and a photomultiplier, 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 6 to 8 The phase transition temperature and various characteristic values of the compound of the present invention were measured in the same manner as in Example 5. The results are shown in Table-1.

As a comparative example, the phase transition temperature and various characteristic values of the following compounds were measured in the same manner as in Example 5, and the results are shown in Table 1.

Application Example 1 In a display device, in order to obtain a liquid crystal composition exhibiting a high-speed response over a wider range of actual operating temperatures, various liquid crystal compounds were mixed and the performance thereof was investigated. In addition, the liquid crystal compounds obtained in the examples were used to evaluate the response characteristics as a liquid crystal display device. The measurement method was the same as in Example 5. The results are shown in Table-1. Application example 1
The composition of the liquid crystal composition used in the above is as follows.

[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. Therefore, it is possible to meet future needs for high-density and large-sized displays. It is possible.

Claims (1)

[Claims] 1. A general formula (In the formula, R ¹ represents an alkyl group having 6 to 12 carbon atoms, R ² represents a linear or branched alkyl group having 1 to 6 carbon atoms,
n represents 0 or 1. ) A liquid crystal compound represented by: