KR19980024636A - Racemic Compounds and Antiferroelectric Liquid Crystal Compositions - Google Patents

Abstract

Racemic Compounds of Formula (1)

And an antiferroelectric liquid crystal composition consisting essentially of a mixture of two or more compounds selected from the racemic compound and one antiferroelectric liquid crystal compound of formula (2) or the antiferroelectric liquid crystal compound of formula (2):

The compositions have good steepness, antiferroelectric phase and fast response over a wide range of temperatures, and high contrast.

Description

Racemic Compounds and Antiferroelectric Liquid Crystal Compositions

The present invention relates to a novel racemic chemical, a novel antiferroelectric liquid crystal composition containing the same, and a liquid crystal display device using the same.

Liquid crystal display devices have been developed as attractive display devices to date due to low voltage operability, low power consumption, and thin display possibilities. Moreover, in recent years, liquid crystal display devices have been practically applied in the information field, OA related fields, and TV set fields, and at the same time, they have been applied in various other applications. Under such a situation, energetic development has been carried out to obtain a liquid crystal display element having a display capacity and display quality that is higher than that of a conventional CTR display element.

Liquid crystal display elements used in commercially available liquid crystal display elements are nematic liquid crystals, which are classified into simple matrix driving liquid crystals and active matrix driving liquid crystals based on driving methods.

The simple matrix drive liquid crystal display device is advantageously manufactured in cost because of its simple structure.

However, there are device problems such as low contrast due to cross-talk, difficulty in large-capacity driving, and difficulty in moving picture display due to slow response speed. Therefore, it is necessary to solve a number of technical problems for obtaining a large liquid crystal display device capable of moving display.

On the other hand, the active matrix driving liquid crystal display element needs to form a thin film transistor for each pixel while using the TFT (thin film transistor) method as the mainstream, and for the construction of high production technology and production line Large investment is needed. Active matrix driving is therefore much more disadvantageous in terms of cost compared to simple matrix driving. However, since the active matrix drive liquid crystal display element does not have a crosstalk phenomenon which is a problem of the simple matrix drive method, the contrast is high, and further, the response speed is fast. Therefore, a high-quality liquid crystal device capable of moving display can be obtained. For this reason, among the active matrix driving methods, the TFT method occupies the position as mainstream.

Such large liquid crystal devices of 10 to 20 inches have been developed, and at present, the problem regarding the fateful viewing angle dependence of devices using nematic liquid crystals is important.

Various technical studies have been conducted to solve the viewing angle dependence. As a result, the display having a viewing angle of about 140 ° has been made possible without gray scale inversion. However, the contrast is still largely dependent on the viewing angle, and it is not possible to obtain flat contrast characteristics such as those achieved in the CTR of the wide viewing angle.

Under such a situation, a liquid crystal display element for using a ferroelectric liquid crystal attracts attention as a quick response liquid crystal display element. Surface stabilized ferroelectric liquid crystal (SSFLC) devices, published by Clark and Lagerwell, are noteworthy in that they have fast response speeds and wide viewing angles that have not previously been achieved. Its switching characteristics have been examined in detail, and many ferroelectric liquid crystal compounds have been synthesized in order to optimize various property constants.

In order to achieve a practical device, there have been a number of technical difficulties that must be overcome, such as the realization of memory characteristics due to the difficulty of orientation control and control of layer structure, orientation breakage caused by mechanical impact, and the like, and these problems are a product. Overcoming by producing the device. However, the ferroelectric liquid crystal device still has problems in that color display is not possible because gradation display is impossible in principle, and that moving pictures are difficult because high-speed response is not realized.

Moreover, as another high-speed response liquid crystal display device, development of a device having a switching mechanism different from that of the SSFLC is also underway. There is a liquid crystal display device that uses switching between tristable states of a liquid crystal compound having antiferroelectricity (hereinafter referred to as an antiferroelectric liquid crystal compound) (Japanese Journal of Applied Physics, Vol. 27, pp. L729, 1988).

The antiferroelectric liquid crystal device has three stable states, that is, two uniform states (Ur, U1) and a third state observed in the ferroelectric element. The third state is reported by Chandani as a anti-ferroelectric phase (Japanese Journal of Applied Physics, Vol. 28, pp. L1261 (1989) and Japanese Journal of Applied Physics, Vol. 28, pp. L1265 (1989). The switching between the tristable states is the first characteristic of the antiferroelectric liquid crystal device The second characteristic of the antiferroelectric liquid crystal device is that there is a clear limit on the applied voltage. This is the third characteristic of the antiferroelectric liquid crystal device.

Moreover, a fourth feature of the antiferroelectric liquid crystal is that the layer structure of the antiferroelectric liquid crystal is easily switched when an electric field is applied (Japanese Journal of Applied Physics, Vol. 28, pp. L119 (1989). And Japanese Journal of Applied Physics , Vol. 29, pp. L111 (1990)). Because of the above characteristics, it is possible to produce a liquid crystal display element having a self-healing ability of a defect-free orientation.

By using the above characteristics, a liquid crystal element having excellent contrast with a fast response speed can be achieved.

Furthermore, it has been demonstrated that ferroelectric liquid crystal elements and impossible gray scale display are possible with antiferroelectric liquid crystal elements. As a result, the shift towards full-color display is possible, and the importance of antiferroelectric liquid crystals increases (Preliminary Proceedings of the 4th International Conference on Ferroelectric Liquid Crystals, para. 77, (1993)).

Under these circumstances, energetic development for achieving an antiferroelectric liquid crystal display device is underway, but the present development faces the following problems.

When an antiferroelectric liquid crystal is used in a display element, an antiferroelectric liquid crystal is usually sandwiched between two glass substrates provided in an insulating film and an alignment film. The insulating film is used to prevent a short circuit, which needs to have a certain thickness to completely prevent the short circuit. On the other hand, an alignment film is needed to orient the liquid crystal molecules in a certain direction, which is also necessary to have a certain thickness in order to reduce the orientation disadvantage to as few as possible, which disadvantage occurs when the liquid crystal molecules are aligned. .

When voltage is applied to the liquid crystal display element formed as defined above, and when the thickness of the insulating film and the alignment film is small or absent, the phase transition from the antiferroelectric state to the ferroelectric state occurs rapidly with respect to the applied voltage. However, when the alignment film and the insulating film have a practically necessary thickness, the phase transition from the anti-ferroelectric state to the ferroelectric state occurs slowly with respect to the applied voltage.

In the driving of the antiferroelectric liquid crystal, in order to obtain a memory effect, after applying a voltage for writing, a holding voltage lower than the voltage for writing is continuously applied for a predetermined time. As described above, when the phase transition from the anti-ferroelectric state to the ferroelectric state occurs smoothly with respect to the applied voltage, that is, in the liquid crystal display device lacking steepness, the holding voltage that can be selected is limited to a very narrow range. In this case, since the holding voltage cannot be set, memory characteristics cannot be secured. This means that the antiferroelectric liquid crystal display element is no longer used by itself, which is a serious problem.

Moreover, in the device lacking steepness, the width of the retention voltage that can be selected decreases, so-called driving margin decreases. Therefore, the practical element needs to have high steepness, and requires a liquid crystal material capable of obtaining such steepness.

As described above, it is preferable that the antiferroelectric liquid crystal should have a property of giving high steepness when used in a liquid crystal display device.

Moreover, it was experimentally confirmed that steepness of the liquid crystal display element has a significant relationship with the thickness of each of the insulating film and the alignment film.

It has been considered what perception can explain the relationship. In the following steps, both the insulating film and the alignment film will be referred to as an alignment film.

To help understand this consideration, it will be described with reference to FIGS. 1 to 5 below.

1 shows an equivalent circuit of an antiferroelectric liquid crystal device.

2 shows simulation results of steepness when no alignment film is present.

3 shows simulation results of steepness when the alignment layer is present.

4 shows the optical response in Comparative Examples 1 and 2, the hysteresis with an arrow indicates the optical response in Comparative Example 2 and the hysteresis without an arrow shows the optical response in Comparative Example 1. FIG.

FIG. 5 shows the optical response in Examples 1 and 8, the hysteresis with arrows indicates the optical response in Example 8 and the hysteresis without arrows shows the optical response in Comparative Example 1. FIG.

FIG. 1 shows an equivalent circuit including a current source for generating polarized current in accordance with the added overtime, an alignment film which is a capacitance (C) connected in series with an antiferroelectric liquid crystal, and a drive circuit that is an ideal voltage source.

In Fig. 1, the driving voltage applied to the device is Vex, the voltage generated on the upper and lower surfaces of the alignment film by charging of the polarization half current is Vc, the effective voltage actually applied to the liquid crystal is Veff, the spontaneous polarization of the liquid crystal is P, and the electrode of the liquid crystal device. The area is S, the thickness of the alignment film is d ', and the dielectric constant of the alignment film is ε'.

Vc is calculated as follows.

(1) Vc = PS / C = PSD '/ (Sε') = P (d '/ ε')

Based on the above equation, Veff is represented by the following equation.

(2) Veff = Vex-Vc = Vex-P (d '/ ε')

As shown in equation (2), the voltage actually applied to the liquid crystal is lower than the voltage applied externally by the production of the polarization P of the liquid crystal, the thickness d 'of the alignment film and the inverse of the alignment film dielectric constant 1 / ε'.

Then, when the thickness of the liquid crystal filled in the liquid crystal cell is d, the electric field Eaff actually applied to the liquid crystal is expressed by the following equation.

(3) Eeff = Veff / d

On the other hand, the apparent electric field strength Eex is represented by the following equation (4).

(4): Eex = Vex / d = (Veff + Vc) / d

= Veff / d + P (d '/ ε') / d = Eff + α

[Wherein α = d '/ (ε' d)... … … … … … … … (5)]

When no alignment film is present, the second term in Equation (4) is 0, and then Eex = Eeff.

While the antiferroelectric liquid crystal exhibits the hysteresis of its optical response to the applied voltage, four thresholds are considered for this hysteresis. Each threshold is Eeff (= Eex), in which case these thresholds are not inclined with respect to the electric field. 2 shows this state.

When the alignment film is present, equation (4) is modified to obtain the following equation.

(6): Eeff = Eex = αP

In other words, the effective electric field applied to the liquid crystal is lower than the electric field Eex applied by? As a result, as shown in Fig. 3, the hysteresis deforms to a considerable extent due to the contribution of? P.

From this discussion, the deformation of hysteresis can be largely caused by the spontaneous polarization and the interaction of the alignment layer. In order to obtain liquid crystals with reduced hysteresis modifications, it is necessary to reduce the interaction to the lowest possible level.

For this purpose, specific measures to be taken include the use of an alignment film with a high dielectric constant, a decrease in the thickness of the alignment film and an eight reduction in the liquid crystal spontaneous polarization, as is apparent from the equations (5) and (6). In this measure, there are not many kinds of high dielectric constant compounds that can be used industrially, and therefore it is difficult to select usable alignment films.

As a result, the reduction of the alignment film thickness and the reduction of the spontaneous polarization of the liquid crystal are concrete measures.

In general, antiferroelectric liquid crystal compounds have a large spontaneous polarization, and liquid crystals having relatively good physical properties have spontaneous polarization of 200 nc / cm 2 or more. Therefore, if the alignment film thickness does not decrease much, the hysteresis deformation is considerably large. However, when the thickness of the alignment film is decreased, a problem arises in that the alignment state of the liquid crystal molecules is poor and the contrast cannot be secured. The measures to reduce the alignment film thickness to correct the hysteresis strain are therefore considerably limited.

On the other hand, a suitable compound without spontaneous polarization of the spontaneous polarization of the liquid crystal compound is reduced by the method of mixing with the liquid crystal compound, that is, the concentration of the liquid crystal compound is diluted. However, since the response speed of the liquid crystal is determined by the applied voltage and the production of the spontaneous polarization, a new problem arises in that the response speed decreases when the spontaneous polarization is simply reduced by dilution. In order to obtain devices with reduced strain of hysteresis, satisfactory performance has not been achieved during attempts to develop antiferroelectric liquid crystal compounds having low polarization polarization, low threshold voltage and low viscosity.

1 shows an equivalent circuit of an antiferroelectric liquid crystal device.

2 shows simulation results of steepness when no alignment film is present.

3 shows simulation results of steepness when the alignment layer is present.

4 shows the optical response in Comparative Examples 1 and 2, the hysteresis with an arrow indicates the optical response in Comparative Example 2 and the hysteresis without an arrow shows the optical response in Comparative Example 1. FIG.

FIG. 5 shows the optical response in Examples 1 and 8, the hysteresis with arrows indicates the optical response in Example 8 and the hysteresis without arrows shows the optical response in Comparative Example 1. FIG.

The present invention has been made in view of the above, and has been found by completing the following. By selection and addition of racemic chemicals of suitable chemical structure using spontaneous polarization reduction to reduce the deformation of hysteresis of the antiferroelectric liquid crystal compound, spontaneous polarization can be reduced without reducing the response speed, When using a composition containing racemic chemicals, the liquid crystal device exhibits a reduction in hysteresis strain.

That is, in the present invention, the following general formula (1)

Formula 1

[Wherein m is an integer of 3 to 12, n is an integer of 3 to 8, each of X ¹ and X ² are both hydrogen atoms or one hydrogen atom and the other a fluorine atom, and each of Y ¹ and Y ² are both hydrogen atoms or one hydrogen atom and the other a fluorine atom.

In the present invention, further, the racemic chemical of formula (1) and the following formula (2)

Formula 2

[Wherein R is a straight chain alkyl group having 6 to 12 carbon atoms, Z is a hydrogen atom or a fluorine atom, A is -CH ₃ or -CF ₃ and r is 0 or 1, and if A is -CH ₃ , r is 0 p is an integer from 4 to 10, if A is -CF ₃ , r is 0 and p is an integer from 6 to 8, if A is -CH ₃ and r is 1, s is an integer from 5 to 8 p is an integer of 2 to 4] to provide an antiferroelectric liquid crystal composition substantially composed of the antiferroelectric liquid crystal compound.

The present invention will be described in more detail below.

The racemic chemical of formula (1) is preferably a compound of formula (1) wherein m is an integer of 3 to 6, particularly preferably a compound of formula (1) wherein m is 9 and n is 6. Further, the racemic chemical of formula (1) is preferably a compound of formula (1) wherein each X ¹ , X ² and Y ¹ are all hydrogen atoms and Y ² is a fluorine atom.

The racemic chemical of formula (1) can be easily produced by the following method.

(a) HO-Ph (X) -COOH + RCOCl → RCOO-Ph (X) -COOH

(b) (a) + SOCl ₂ → RCOO-Ph (X) -COCl

(c) AcO-Ph (Y) -COOH + SOCl 2-> AcO-Ph (Y) -COCl

(d) (c) + R '(OH)-> AcO-Ph (Y) -COOR'

(e) (d) + (Ph-CH ₂ NH ₂ ) → HO-Ph (Y) -COOR '

(f) (b) + (e) → the target

In the above formula, AcO- is an acetyl group, each of -Ph (X)-and -Ph (Y)-is a 1,4-phenylene group capable of substituting a fluorine atom, R is a straight alkyl group, and R 'is a racemic alcohol. The residue and Ph- are phenyl groups.

The preparation method will be described briefly below.

(a) shows that fluorine-substituted or unsubstituted p-hydroxybenzoic acid and alkyl chloride chloride react to form an ester.

(b) shows the chlorination of the ester obtained in (a).

(c) shows the chlorination of fluorine-substituted or unsubstituted p-acetoxybenzoic acid with thionyl chloride.

(d) shows that the chloride obtained in (c) reacts with the racemic to form an ester.

(e) represents deacetylation of the ester obtained in (d).

(f) shows the formation of racemic chemicals by the reaction of the chlorides obtained in (b) with the phenols obtained in (e).

The antiferroelectric liquid crystal composition of the present invention consists essentially of the racemic chemical of Formula (1) and the antiferroelectric liquid crystal composition of Formula (2). Compounds of formula (2) include (i) A is -CF ₃ , r is 1, s is an integer from 5 to 8, p is 2 or 4, or (ii) A is -CH ₃ , r is 0 and p Compounds of formula (2) wherein 4 are 6 to 6 are particularly preferred because the compositions containing said compounds are well balanced in various physical properties.

The antiferroelectric liquid crystal compound of formula (2) used in the present invention can be easily prepared as shown in the following method. For example, a compound of formula (2) wherein A = CF ₃ , p = 2, r = 1 and s = 5 is prepared by the following method.

(a) AcO-Ph (Z) -COOH + SOCl _2- > AcO-Ph (Z) -COCl

(b) (a) + HOC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅

¡Æ AcO-Ph (Z) -COOC * H (CF ₃ ) (CH ₂ ) ₅ OC2H ₅

(c) (b) + Ph-CH ₂ NH ₂

→ HO-Ph (Z) -COOC * H (CF ₃ ) (CH ₂ ) ₅ OC ₂ H ₅

(d) RO-Ph-Ph-COOH + SOCl _2- > RO-Ph-Ph-COCl

(e) (b) + (d) → antiferroelectric liquid crystal compound

In the above formula, AcO- is an acetyl group, -Ph (Z) is a 1,4-phenylene group which can be substituted with fluorine, Ph- is a phenyl group, -Ph- is a 1,4-phenylene group and C ^* is an asymmetric carbon atom to be.

(a) shows the chlorination of fluorine-substituted or unsubstituted p-acetoxybenzoic acid with thionyl chloride.

(b) shows that the chloride obtained in (a) reacts with an alcohol to form an ester.

(c) shows the deacetylation of the ester obtained in (b).

(d) shows the chlorination of alkyloxybiphenylcarboxylic acid.

(e) shows the formation of a liquid crystal by reaction of the phenol obtained in (c) with the chloride obtained in (d).

The antiferroelectric liquid crystal composition of the present invention consists essentially of the racemic compound of formula (1) and the antiferroelectric liquid crystal compound of formula (2). Specifically, the total amount of compounds of the formulas (1) and (2) is at least 70%, preferably at least 80% with respect to the total composition.

The compound mixing ratio of the compound of the formula (1): The compound of the formula (2) is in a molar ratio, preferably 1:99 to 60:40, particularly preferably 5:95 to 50:50.

In addition, the followings were also found in the present invention. While one compound of formula (2) or at least two compounds can be used, it is preferred to use a mixture of at least two compounds of formula (2) as compounds of formula (2), wherein (i) A is -CF ₃ , r is 1, s is an integer of 5 to 8, p is 2 or 4, and (ii) A is -CH ₃ , r is 0 and p is an integer of 4 to 6 It is particularly preferable to use a mixture of the compounds of), and it is possible to obtain a liquid crystal display number which is excellent in the orientation characteristic and steepness and exhibits high contrast.

It is preferable that the antiferroelectric liquid crystal composition of the present invention has at least one smectic A phase and an antiferroelectric phase in a temperature range of 0 to 40 ° C. The antiferroelectric liquid crystal composition of the present invention is preferably used in antiferroelectric liquid crystal display digits using a composition disposed on a pair of electrode substrates.

EXAMPLE

The invention will be described with reference to the following examples, which are not intended to limit the invention.

Example 1

Preparation of 4- (1-methylheptyloxycarbonyl) phenyl = 4-decanoyloxybenzoate (Formula (1): m = 9, X ¹ = X ² = Y ¹ = Y ² = H, n = 6 ( E1))

(1) Preparation of 4-decanoyloxybenzoic acid

12.7 g of p-hydroxybenzoic acid is added to 150 mL of dichloromethane and the resulting suspension is added to 10.2 g (0.0917 mol) of triethylamine. The mixture is stirred to form a homogeneous solution. To the solution is added 18.3 g (0.096 mol) of decanoyl chloride in an appropriate proportion without refluxing dichloromethane. Then 1.0 g (0.0085 mol) of 4-dimethylaminopyridine is added and the mixture is stirred overnight at room temperature. The resulting reaction mixture is extracted with ether. The ether is evaporated and the crude product is washed with hexane and dried to give 19.4 g (85% yield) of the intended carboxylic acid as the desired product.

(2) Preparation of 4-acetoxy-1- (1-methylheptyloxycarbonyl) benzene

60 ml of thionyl chloride is added to 10.8 g (0.06 mol) of 40 acetoxybenzoic acid, and the mixture is reacted under reflux for 7 hours. Excess thionyl chloride is then evaporated and 10 ml of pyridine and 5.24 g (0.0402 mol) of 1,2-octanol are added dropwise. After the dropwise addition, the mixture is stirred for one day at room temperature, and then the reaction mixture is diluted with 20 ml of ether. The organic layer is washed with successively diluted hydrochloric acid, 1N aqueous sodium hydroxide solution and water, and dried over magnesium sulfate. The solvent is evaporated and the crude product produced by silica gel column chromatography using hexane / ethyl acetate as the solvent is purified to give 10.6 g (90% yield) of the target product.

(3) Preparation of 4-hydroxy-1- (1-methylheptyloxycarbonyl) benzene

10.6 g (0.0361 mol) of the compound obtained in the above (2) is dissolved in 250 ml of ethanol, and 7.74 g (0.0772 mol) of benzylamine is added dropwise. The mixture is stirred at room temperature for one day, then diluted with 300 ml of ether, washed with successively diluted hydrochloric acid and water and dried over magnesium sulfate. The solvent is evaporated and then 8.9 g (98% yield) of the desired product is obtained using silica gel column chromatography for isolation purification.

(4) Preparation of 4- (1-methylheptyloxycarbonyl) phenyl = 4-n-decanoyloxybenzoic acid

15 ml of thionyl chloride is added to 3.1 mmol of the compound obtained in (3) above, and the mixture is refluxed with heating for 5 hours. Excess thionyl chloride is evaporated, then 2 ml of pyridine and 2.12 mmol of the compound obtained in (3) are added and the mixture is allowed to react for 10 hours at room temperature.

After completion of the reaction, the reaction mixture is diluted with 300 ml of ether and washed with successively diluted hydrochloric acid, 1N aqueous sodium carbonate solution and water, and the organic layer is dried over magnesium sulfate. The solvent is then evaporated and silica gel chromatography is used for isolation to afford 0.96 g (87% yield) of the desired product.

EXAMPLES 2-7

3-fluoro-4- (1-methylheptyloxycarbonyl) phenyl = 4-decanoyloxybenzoate (Formula (1): m = 9, X ¹ = X ² = Y ¹ = H, Y ² = F , n = 6 (E2)), 4- (1-methylheptyloxycarbonyl) phenyl = 2-fluoro-4-decanoyloxybenzoate (Formula (1): m = 9, X ¹ = Y ² = Y ¹ = H, X ² = F, n = 6 (E3)), 4- (1-methylheptyloxycarbonyl) phenyl = 3-fluoro-4-decanoyloxybenzoate (Formula (1): m = 9, X ² = X ¹ = Y ² = H, Y ¹ = F, n = 6 (E4)), 2-fluoro-4- (1-methylheptyloxycarbonyl) phenyl = 4-decanoyloxy Benzoate (Formula (1) m = 9, X ¹ = X ² = Y ² = H, Y ¹ = F, n = 6 (E5)), 2-fluoro-4- (1-methylheptyloxycarbonyl ) Phenyl = 2-fluoro-4-decanoyloxybenzoate (Formula (1) m = 9, X ¹ = X ² = H, Y ² = Y ¹ = F, n = 6 (E6)), and 2 -Fluoro-4- (1-methylheptyloxycarbonyl) phenyl = 3-fluoro-4-decanoyloxybenzoate (Formula (1) m = 9, X ¹ = Y ¹ = H, X ² = Y Preparation of ² = F, n = 6 (E7))

The desired product is obtained in the same manner as in Example 1 except for using p-hydroxybenzoic acid or 4-acetoxy benzoic acid which is substituted with fluorine on benzene if necessary.

Table 1 shows the 1 H-NMR data of the target compounds obtained in Examples 1 to 7, whose chemical structures are represented by (E1) to (E7).

TABLE 1

Comparative Example 1

The antiferroelectric liquid crystal compounds (2A, 2B) of the following compounds are mixed in a compound (2A) / compound (2B) mixing ratio 70/30 (molar ratio) to obtain an antiferroelectric liquid crystal composition. Table 2 shows the sequence obtained of the obtained composition.

2A: C ₉ H ₁₉ O-Ph-Ph-COO-Ph (3F) -COO-C ^* H (CH ₃ ) (CH ₂ ) ₅ OC ₂ H ₅

(Formula (2): R = C ₉ H ₁₉ , Z = F, A = CF ₃ , r = 1, s = 5, p = 2)

2B: C ₈ H ₁₇ O-Ph-Ph-COO-Ph (3F) -COO-C ^* H (CH ₃ ) C ₅ H ₁₁

(Formula (2): R = C ₈ H ₁₇ , Z = F, A = CF ₃ , r = 0, p = 5)

When a triangular wave voltage is applied to the antiferroelectric liquid crystal composition at 60 ° C., as shown in FIG. 4, it has optical response hysteresis with respect to the applied voltage, and a deformation of a huge hysteresis is observed. In addition, the response time is measured at 60 ° C. in the spontaneous polarization of the composition and the transition from antiferroelectric to ferroelectric. Table 3 shows the results. The optical response hysteresis, response time and spontaneous polarization were measured as follows.

A liquid crystal cell (cell thickness 2 mu m) of an ITO electrode having a rubberized polyimide thin film (30 nm) is filled in an isotropic state with a liquid crystal. The cell is then gradually cooled at a rate of 1.0 ° C./min to orient the liquid crystal. The cells are arranged between orthogonal deflection plates so that the layer direction of the liquid crystal is parallel to the analyzer or deflection plate.

An A ± 30V triangular wave voltage having a frequency of 30 MHz is applied to the cell, and an optical response hysteresis is obtained in which a photomultiplier tube measures a change in the amount of transmitted light of the liquid crystal composition.

In the transition from antiferroelectric phase to ferroelectric phase, the response time is defined as the time required to change the transmittance of 10% to 90% at 100% maximum transmittance and 0% minimum transmittance while applying a 30V voltage having a frequency of 10 Hz. do.

Spontaneous polarization is obtained by applying a 25V triangle wave at 60 ° C and measuring the polarization inversion current.

Comparative Example 2

An optically active compound (3A) of the following compound was further mixed with a semiferroelectric liquid crystal compound (2A, 2B) used in Comparative Example 1 at a 2A / 2B / 3A mixing ratio (molar ratio) of 60/20/20, and Comparative Example 1 The sequence, optical response hysteresis, spontaneous polarization and response time of the composition are measured in the same manner as.

Tables 2 and 3 show the results.

3A: C ₉ H ₁₉ O-COO-Ph (3F) -COO-C ^* H (CH ₃ ) C ₆ H ₁₃ (R sieve)

4 shows the optical response hysteresis of the composition.

As shown in FIG. 4, while the optical hysteresis of the composition is improved by the addition of 3A, the response speed decreases.

Example 8

The racemic compound (E5) obtained in Example 5 was mixed with the semiferroelectric liquid crystal compounds (2A, 2B) at a 2A / 2B / E5 mixing ratio of 56/24/20, and the sequence of the composition was obtained in the same manner as in Comparative Example 1. Optical response hysteresis, spontaneous polarization and response time are measured.

Tables 2 and 3 show the results.

In addition, FIG. 5 shows the optical response hysteresis of the composition.

As shown in FIG. 5, the optical hysteresis of the composition is improved and although its spontaneous polarization is about half, it exhibits fast response.

TABLE 2

In Table 2, the number in () is the transition temperature (unit: ° C), Cr is the crystalline phase, SCA ^* is the antiferroelectric phase, SC ^* is the ferroelectric phase, SA is the smectic A phase, and I is isotropic phase. .

TABLE 3

EXAMPLES 9-13

A semiferroelectric liquid crystal composition which is a semiferroelectric liquid crystal compound (2A and 2B) at a mixture ratio of 2A / 2B racemic compound of 56/24/20 (molar ratio) of one of the racemic compounds (E1, E4, E3, E6 or E7); By mixing, an antiferroelectric liquid crystal composition is obtained.

Example 14

49/21/30 (molar ratio) mixes a semiferroelectric liquid crystal compound with a racemic compound (E5) in a 2A / 2B / E5 mixing ratio, and obtains a semiferroelectric liquid crystal composition.

The antiferroelectric liquid crystal compositions obtained in Examples 9 to 14 are measured for phase series, optical response hysteresis, spontaneous polarization and response, respectively. Tables 4 and 5 show the results.

When the triangular voltage is applied at 60 ° C., the optical response hysteresis is measured with respect to the voltage to which the antiferroelectric liquid crystal composition is applied. While the composition obtained in Comparative Example 1 shows a deformation of large hysteresis, the composition obtained in this Example shows reduced steepness.

The spontaneous polarization is obtained by measuring the polarization inversion current while applying a triangular wave of 25V at 60 ° C.

TABLE 4

In Table 3, the values in () represent the transition temperature (unit: ° C), Cr is the crystalline phase, SCA ^* is the antiferroelectric phase, SC ^* is the ferroelectric phase, SA is the smectic A phase, and I is isotropic phase. do.

TABLE 5

Example 15

Preparation of 3-fluoro-4- (1-methylbutyloxycarbonyl) phenyl = 4-decanoyloxybenzoate

(1) Preparation of 4-decanoyloxybenzoic acid

12.7 g (0.0917 mol) of p-hydroxybenzoic acid are added to 150 mL of dichloromethane and 10.2 g (0.0917 mol) of triethylamine are added to the resulting suspension. The mixture is stirred until a homogeneous solution is formed. 18.3 g (0.096 mol) of decanoyl chloride is added to the solution in an appropriate proportion without refluxing dichloromethane. Then 1.0 g (0.0085 mol) of 4-dimethylaminopyridine is added and the mixture is stirred overnight at room temperature.

1N hydrochloric acid is added to the resulting reaction mixture and the mixture is extracted with ether. The ether is evaporated and the resulting crude product is washed with hexane and dried to give 19.4 g (85% yield) of the intended carboxylic acid as the desired product.

(2) Preparation of 4-acetoxy-2-fluoro-1- (1-methylbutyloxycarbonyl) benzene

60 ml of thionyl chloride is added to 10.8 g (0.06 mol) of 4-acetoxy-2-fluoro-benzoic acid and the mixture is reacted under reflux for 7 hours. Excess thionyl chloride is then evaporated and then 10 ml of pyridine and 3.5 g (0.0402 mol) of 2-pentanol are added dropwise.

After the dropwise addition, the mixture is stirred at room temperature for one day, and then the reaction mixture is diluted with 200 ml of ether. The organic layer was washed with successively diluted hydrochloric acid, 1N aqueous sodium hydroxide solution and water, and dried over magnesium sulfate. The solvent is evaporated and the crude target product produced by silica gel column chromatography using hexane / ethyl acetate as solvent is purified to give 10.8 g (90% yield) of the target product.

(3) Preparation of 3-fluoro-4-hydroxy-1- (1-methylbutyloxycarbonyl) benzene

9.7 g (0.0361 mol) of the compound obtained in the above (2) is dissolved in 250 ml of ethanol, and 7.74 g (0.0772 mol) of benzylamine is added dropwise. The mixture is further stirred at room temperature for one day, then diluted with 300 ml of ether, washed with successively diluted hydrochloric acid and water and then dried over magnesium sulfate. The solvent is evaporated and then 8.0 g (98% yield) of the desired product is obtained using silica gel column chromatography for isolation.

(4) Preparation of 3-fluoro-4- (1-methylbutyloxycarbonyl) phenyl = 4-n-decanoyloxybenzoate

15 ml of thionyl chloride is added to 3.1 mmol of the compound obtained in (1) above, and the mixture is stirred under heating for 5 hours. Excess thionyl chloride is evaporated, then 2 ml of pyridine and 2.12 mmol of the compound obtained in (3) above are added and the mixture is allowed to react at room temperature for 10 hours. After completion of the reaction, the reaction mixture is diluted with 300 ml of ether and washed with successively diluted hydrochloric acid, 1N aqueous sodium carbonate solution and water, and the organic layer is dried over magnesium sulfate. The solvent is then evaporated and 9.2 g (1.84 mmol, 87% yield) of the desired product is obtained using silica gel column chromatography for isolation.

[Examples 16-21]

Example 16 Preparation of 3-Fluoro-4- (1-methylheptyloxycarbonyl) phenyl = 4-decanoyloxybenzoate (Formula (1): m = 9, n = 5, X ¹ = X ² = Y ¹ = H, Y ² = F (E9))

Example 17 Preparation of 3-fluoro-4- (1-methylnonyloxycarbonyl) phenyl = 4-decanoyloxybenzoate (Formula (1): m = 9, n = 8, X ¹ = X ² = Y ¹ = H, Y ² = F (E10))

Example 18 Preparation of 3-fluoro-4- (1-methylheptyloxycarbonyl) phenyl = 4-butanoyloxybenzoate (Formula (1): m = 3, n = 6, X ¹ = X ² = Y ¹ = H, Y ² = F (E11))

Example 19 Preparation of 3-fluoro-4- (1-methylheptyloxycarbonyl) phenyl = 4-hexanoyloxybenzoate (Formula (1): m = 5, n = 6, X ¹ = X ² = Y ¹ = H, Y ² = F (E12))

Example 20 Preparation of 3-Fluoro-4- (1-methylheptyloxycarbonyl) phenyl = 4-octanoyloxybenzoate (Formula (1): m = 7, n = 6, X ¹ = X ² = Y ¹ = H, Y ² = F (E13))

Example 21 Preparation of 3-Fluoro-4- (1-methylheptyloxycarbonyl) phenyl = 4-undecanoyloxybenzoate (Formula (1): m = 10, n = 6, X ¹ = X ² = Y ¹ = H, Y ² = F (E14))

The compound in Examples 16 to 21 was obtained by the same method as in Example 15.

Table 6 shows the NMR data of the target product obtained in Examples 15 to 21, the chemical structure of which is represented by (E8) to (E14).

TABLE 6

[Examples 22-28]

The racemic compounds (E8) to (E14) obtained in Examples 15 to 21 and 56/24/20 (molar ratio) with a composition containing the same antiferroelectric liquid crystal compounds (2A and 2B) as those used in Comparative Example 1 In each of the 2A / 2B racemic compound mixing ratios), they are mixed to obtain a semiferroelectric liquid crystal compound.

The phase sequence, optical response hysteresis, spontaneous polarization and response time of the composition obtained in the same manner as in Comparative Example 1 were measured. Table 7 shows the result with the result of the comparative example 1 as a reference.

Although the spontaneous polarization of the composition was significantly reduced, all of the compositions obtained in Examples 22-28 improved in optical hysteresis and exhibit fast response.

TABLE 7

In the phase series of Table 7, () values indicate transition temperature (° C), Cr is crystalline phase, SCA ^* is antiferroelectric phase, SC ^* is ferroelectric phase, SA is smectic A phase, and I is isotropic phase. do.

Example 29

In the present invention, a compound is prepared by mixing the following compounds (i) to (iii) and the following compound (iv) selected from the compounds of the formulas (1) and (2), wherein the composition has a phase sequence, response time, tilt angle, and antiferroelectric. Measure for light exposure and steepness in the state. Tables 8 and 9 show the results.

In the formula, -Ph- represents a 1,4-phenylene group, -Ph (3F)-represents a 1,4-phenylene group containing a fluorine substituted at the 3-position, and a C ^* asymmetric carbon atom.

Phase series are obtained by tissue challenge and DSC measurements via a polarizing microscope. Response time, tilt angle, light exposure and steepness are obtained as follows.

The compound is filled in an isotropic state in a liquid crystal cell (cell thickness 2 mu m) of an ITO electrode having a rubber-treated polyimide thin film. The cell is then gently cooled at the rate of 1 ° C./min to orient the liquid crystal. The cells are arranged between orthogonal deflection plates so that the layer direction of the liquid crystal is parallel to the analyzer or deflection plate.

Response time (response time I: transition from antiferroelectric to ferroelectric) is a change of 10% to 90% transmittance at 100% maximum transmittance and 0% minimum transmittance with a 30V triangular wave voltage of frequency 10 Hz. It is defined as the time required for.

The inclination angle is applied to the test cell at 30 ° C by applying a ± 30V triangular wave voltage having a frequency of 30 Hz, and measuring the rotation of the test cell until the dark field is found.

Light exposure (light transmittance in antiferroelectric state) is obtained as follows.

Cool the test cell to 30 ° C and reduce the zig-zag coupling by applying a ± 30V sphere-wave voltage at a frequency of 30 Hz for 5 minutes. In addition, the amount of light transmitted through the cell is detected by a photomultiplier, and the test cell is rotated so that the amount of light transmitted in both antiferroelectric states generated in the switching is equivalent.

After applying a voltage, the amount of light transmitted in the antiferroelectric state is measured with a photomultiplier. In addition, a 30V direct current voltage was applied to the cell to make the composition ferroelectric, and the amount of light transmitted in this state was measured with a photomultiplier.

Then, empty cells are placed between orthogonal deflection plates, and the amount of transmitted light is similarly measured.

The transmitted light amount is treated as light leak by the polarizing plate. When the amount of light transmitted in the ferroelectric state is 100% and the amount of light transmitted in the empty cell is 0%, the light transmittance (light exposure) is obtained in the antiferroelectric state.

In the hysteresis curve of the transition from the antiferroelectric state to the ferroelectric state, when a 30V triangular wave voltage of 30 kHz is applied to the test cell, steepness is defined as follows.

Steepness = (0.9-0.1) / (V ₉₀ -V ₁₀ ) (Unit: 1 / V)

V ₉₀ = voltage at 90% transmittance

V ₁₀ = voltage at 10% transmittance

The larger the value obtained by calculating based on the above equation, the better the steepness of the liquid crystal.

Example 30

The following compounds (i) and (iii) selected from the compounds of the formulas (1) and (2) are mixed to form a composition, the composition being subjected to light exposure and steepness in the phase sequence, response time, tilt angle, antiferroelectric state. Measure for Tables 8 and 9 show the results.

Wherein -Ph-, -Ph (3F)-and C ^* are as defined in Example 29.

Comparative Example 3

In the present invention, a compound is prepared by mixing the following compounds (i) and (ii) selected from the compound of formula (2), and the composition is prepared for phase sequence, response time, tilt angle, light exposure and steepness in antiferroelectric state. Measure

Tables 8 and 9 show the results.

In the above formulae, -Ph-, -Ph (3F)-and C ^* are as defined in Example 29.

TABLE 8

In the phase series of Table 8, () values indicate transition temperature (° C), Cr is a crystalline phase, SCA ^* is an antiferroelectric phase, SC ^* is a ferroelectric phase, SA is a smectic A phase, and I is an isotropic phase. Display.

TABLE 9

Example 31

In the present invention, the following compounds (i) to (iii) are selected and mixed from the compounds of the formulas (1) and (2) to form a composition, and the composition is subjected to light exposure in the phase sequence, response time, tilt angle and antiferroelectric state. Measure for Tables 10 and 11 show the results.

In the formula, -Ph- represents a 1,4-phenylene group, -Ph (3F)-represents a 1,4-phenylene group containing a fluorine substituted at the 3-position, and a C ^* asymmetric carbon atom.

Example 32

In the present invention, the following compounds (i) to (iii) are selected and mixed from the compounds of the formulas (1) and (2) to form a composition, and the composition is subjected to light exposure in the phase sequence, response time, tilt angle and antiferroelectric state. Measure for Tables 10 and 11 show the results.

Wherein -Ph-, -Ph (3F)-and C ^* are as defined in Example 31.

Example 33

In the present invention, the following compounds (i) to (iii) are selected and mixed from the compounds of the formulas (1) and (2) to form a composition, and the composition is subjected to light exposure in the phase sequence, response time, tilt angle and antiferroelectric state. Measure for Tables 10 and 11 show the results.

Wherein -Ph-, -Ph (3F)-and C ^* are as defined in Example 31.

TABLE 10

TABLE 11

Example 34

In the present invention, the following compounds (i) and (iii) are selected and mixed from the compounds of the formulas (1) and (2) to make a composition, and the composition is subjected to light exposure in the phase sequence, response time, tilt angle and antiferroelectric state. Measure for Tables 11 and 12 show the results.

A composition is prepared from the same compounds as those in Example 34, except that compound (iv) is replaced with the following compound (iv-B).

(iv-B) C ₉ H ₁₉ -COO-Ph-COO-Ph (3F) -COO- (CH ₂ ) ₅ CH ₃

The composition is measured for phase sequence, response time, tilt angle, light exposure and steepness in an antiferroelectric state. Tables 12 and 13 show the results.

Example 36

A composition is prepared from the same compounds as those of Example 34, except that compound (iii) is replaced with the following compound (iii-B).

(iii-B) C ₇ H ₁₅ -COO-Ph (3F) -COO-Ph (3F) -COO- (CH ₃ ) C ₅ H ₁₁

The composition is measured for phase sequence, response time, tilt angle, light exposure and steepness in an antiferroelectric state. Tables 12 and 13 show the results.

TABLE 12

TABLE 13

The present invention provides novel racemic compounds and novel antiferroelectric liquid crystal compositions. The antiferroelectric liquid crystal composition of the present invention provides an antiferroelectric liquid crystal display digit with excellent steepness, has an antiferroelectric phase in a wide temperature range, and exhibits a high speed response, which therefore has high display quality and high contrast.

Claims (12)

Racemic Compounds of Formula (1): Formula 1 [Wherein m is an integer of 3 to 12, n is an integer of 3 to 8, each of X ¹ and X ² are both hydrogen atoms or one hydrogen atom and the other a fluorine atom, and each of Y ¹ and Y ² are both hydrogen atoms or one hydrogen atom and the other a fluorine atom]. The racemic compound of claim 1, wherein the racemic compound has formula (1) wherein m is an integer from 3 to 10. 3. 3. The racemic compound according to claim 1 or 2, wherein the racemic compound each of X ¹ , X ² and Y ¹ are all hydrogen atoms and Y ² is a fluorine atom. Racemic Chemicals of Formula (1) Formula 1 [Wherein m is an integer of 3 to 12, n is an integer of 3 to 8, each of X ¹ and X ² are both hydrogen atoms or one hydrogen atom and the other a fluorine atom, and each of Y ¹ and Y ² Are all hydrogen atoms or one hydrogen atom and the other a fluorine atom] and an antiferroelectric liquid crystal composition substantially composed of the antiferroelectric liquid crystal compound of formula (2): Formula 2 [Wherein R is a straight chain alkyl group having 6 to 12 carbon atoms, Z is a hydrogen atom or a fluorine atom, A is -CH ₃ or -CF ₃ and r is 0 or 1, and if A is -CH ₃ , r is 0 p is an integer from 4 to 10, if A is -CF _3, if r is 0, p is an integer from 6 to 8, and if A is -CH ₃ and r is 1, s is an integer from 5 to 8 P is an integer of 2 or 4 and C ^* is an asymmetric carbon atom. The antiferroelectric liquid crystal composition according to claim 4, wherein the composition contains a compound of formula (1) wherein m is 9. The antiferroelectric liquid crystal composition according to claim 4 or 5, wherein the composition contains a compound of formula (1) wherein each of X ¹ , X ² and Y ¹ are all hydrogen atoms and Y ² is a fluorine atom. The antiferroelectric composition of any one of claims 4 to 6, wherein the composition contains a compound of formula (2) wherein A is -CH ₃ , r is 1, s is an integer from 5 to 8 and p is an integer from 2 or 4. Liquid crystal composition. The antiferroelectric liquid crystal composition according to any one of claims 4 to 6, wherein the composition contains a compound of formula (2) wherein A is -CH ₃ , r is 0 and p is an integer of 4 or 6. 8. The antiferroelectric liquid crystal composition according to claim 4, wherein the composition contains the racemic compound of formula (1) and the antiferroelectric liquid crystal compound of formula (2) in a molar ratio of 1:99 to 60:40. The antiferroelectric liquid crystal composition according to claim 4, wherein at least the smectic A phase is present at a higher temperature side than the antiferroelectric phase, and the antiferroelectric phase has an upper limit temperature of 40 ° C or higher and a lower limit temperature of 0 ° C or lower. The antiferroelectric liquid crystal composition according to claim 4, wherein at least two compounds selected from the antiferroelectric liquid crystal compound of the formula (2) are mixed and used. The antiferroelectric liquid crystal display of Claim 4 formed by arrangement | positioning of an antiferroelectric liquid crystal composition between a pair of electrode substrates.