JPH07316101A - Antiferroelectric liquid crystal substance - Google Patents

Abstract

(57) [Summary] [Object] To provide an anti-ferroelectric liquid crystal substance having a low threshold voltage and a high tilt angle. [Structure] A novel antiferroelectric liquid crystal substance represented by the following general formula (1). [Chemical 1] (In the formula, n represents an integer of 4, 6, or 8, and C ^* represents an asymmetric carbon.)

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel antiferroelectric liquid crystal substance.

[0002]

2. Description of the Related Art Liquid crystal display devices have been used for various small display devices to date because of their low voltage operability, low power consumption, and thin display capability. However, with the recent application of information, OA-related equipment fields or liquid crystal display elements to the television field, and expansion of applications, high-performance large-sized liquid crystal display elements with display capacities and display quality that exceed conventional CRT display elements have been developed. The demands are rising rapidly.

However, as far as the nematic liquid crystal is used, even in the active matrix driving liquid crystal display element adopted for the liquid crystal television, the complexity of the manufacturing process and the low yield are major problems, and those problems are caused. Although it is gradually improving, its size increase,
Cost reduction is not easy. Moreover, even with a STN type liquid crystal display element of simple matrix drive, it is not always easy to drive a large capacity, and there is a limit in response time, making it difficult to display a moving image. Further, the nematic liquid crystal display device has an essential problem that the viewing angle is narrow. Therefore, it is difficult to say that the nematic liquid crystal display device satisfies the above-mentioned demands for the high-performance large-sized liquid crystal display device.

[0004]

Under such circumstances, a liquid crystal display device using a ferroelectric liquid crystal has attracted attention as a high speed liquid crystal display device. Surface Stabilized Ferroelectric Liquid Crystal (SSF) announced by Clarke and La Gavar
It has been noticed that the LC) device has an unprecedented fast response speed and a wide viewing angle, and its switching characteristics have been studied in detail, and many ferroelectric liquid crystals are used to optimize various physical property constants. It is synthesized. However, the threshold characteristics are insufficient, the contrast is poor due to the chevron structure of the layer, high-speed response has not been realized, alignment control is difficult, and one of the most important features of SSFLC. However, there are problems that it is not easy to realize the bistability, and it is difficult to recover the orientation due to mechanical impact, and it is necessary to overcome these problems for practical use.

Separately from this, the development of an element having a switching mechanism different from that of SSFLC is also in progress. Switching between three stable states of a liquid crystal substance having an antiferroelectric phase (hereinafter referred to as an antiferroelectric liquid crystal substance) is one of these new switching mechanisms (Japanese Journal of
Applied Physics, Vol.27, pp.L729,1988). The antiferroelectric liquid crystal element has three stable states. That is, the two uniform states (Ur,
Ul) and the third state. Chandani et al. Reported that this third state is the antiferroelectric phase (Japanese Journal
ofApplied Physics, Vol.28, pp.L1261, 1989, Japan
ese Journal of Applied Physics, Vol.28, pp.L1265, 1
989). Such switching between tristable states is the first feature of the antiferroelectric liquid crystal element. The second characteristic of the antiferroelectric liquid crystal element is that there is a clear threshold value with respect to the applied voltage. Further, it has a memory property, which is the third feature of the antiferroelectric liquid crystal element. By utilizing these excellent characteristics, it is possible to realize a liquid crystal display device having a high response speed and a good contrast.

Another major feature is that the layer structure is easily switched by an electric field (Ja
panese Journal of Applied Physics, Vol.28, pp.L11
9,1989, Japanese Journal of Applied Physics, Vol.
29, pp.L111, 1990). As a result, it is possible to manufacture a liquid crystal display element having few defects and self-repairing orientation, and a liquid crystal element having excellent contrast can be realized. The number of anti-ferroelectric liquid crystal substances known to date is far smaller than that of ferroelectric liquid crystals due to the short history of research on anti-ferroelectric liquid crystals, but as the research progresses, the number will gradually increase. It is increasing. However, from a practical point of view, when looking at the antiferroelectric liquid crystals that have been synthesized so far, the threshold voltage at the time of the phase transition from the antiferroelectric state to the ferroelectric state is high. Since the voltage is high and the tilt angle is small, the brightness or contrast of the display element is low, and there is a problem that an element with high display quality cannot be obtained.

From the above, in order to realize low voltage driving, a material having a threshold voltage of the phase transition from the antiferroelectric state to the ferroelectric state as low as possible, and a display element having high brightness and higher contrast are provided. In order to realize it, the emergence of a material having a tilt angle as large as possible is strongly desired. The threshold voltage directly affects the driving voltage of the device as described above, but is related to the driving IC in practical devices. An IC is required to drive the liquid crystal element,
It is most economical to put a general-purpose IC on the market into practical use for a liquid crystal device. Commercially available general IC
Drive voltage is less than 30V, preferably
It is preferably 25 V or less, and more preferably 20 V or less. Therefore, it is desirable that the threshold voltage of the liquid crystal display device is 20 V or less, preferably 15 V or less, and further 10 V or less.
Normally, the cell gap of an antiferroelectric liquid crystal element is 2 μm or less, and therefore the threshold voltage per cell gap is 10 V / μm or less, preferably 7.5 V / μm or less, and further 5 V / μm or less.
V / μm or less.

Namekawa et al. (Proceedings of the 17th Liquid Crystal Conference)
98, 1991) is the general formula C _m H _{2m + 1} -O-Ph-Ph-COO-Ph (2-F) -COO-COO-C * H (CF ₃ ) C _n H
_{In the} liquid crystal compound represented by _{2n + 1} (2-F in the formula represents fluorine substitution at the 2-position of the phenyl group), when m is an odd number, the threshold voltage is significantly reduced as compared with the even number. I admit. However, the antiferroelectric liquid crystal in which the 2-position of the phenyl group is substituted with fluorine has a small threshold voltage, but has a very small tilt angle of about 20 °, which makes it difficult to consider application to a practical device. In addition, Muragi et al. (Proceedings of the 17th Liquid Crystal Symposium Lecture, 260, 1991) show that the general formula C _n H _{2n + 1} -O-Ph-Ph-COO-Ph (3-F) -COO-C * H ( In CH ₃ ) C ₆ H ₁₃ (wherein 3-F represents fluorine substitution at the 3-position of the phenyl group), the threshold voltage decreases as n increases, but It has been reported that the threshold voltage is significantly increased by fluorine substitution.

Since the tilt angle has a great influence on the brightness and contrast of the liquid crystal display element, especially on the brightness,
The size is a factor that affects the display quality of the display element.
That is, the tilt angle is related to the light transmittance of the element. The larger the tilt angle is, the higher the light transmittance becomes, and as a result, an element having excellent brightness and contrast can be realized. The maximum tilt angle is 45 ° in the case of antiferroelectric liquid crystal, and it is an important point in the development of antiferroelectric liquid crystal materials to bring the tilt angle of the liquid crystal material as close as possible to this value. In the case of an element having low brightness, for example, in the case of a display, it is possible to compensate for the low brightness by strengthening the backlight, but strengthening the backlight causes an increase in power consumption and is not preferable. For this reason, the tilt angle of the device is at least 27 ° or more, preferably 30 ° or more, and most preferably 35 ° or more. In addition, up to now, there has been no report showing the relationship between the tilt angle and the chemical structure. In addition, the maximum tilt angle of the antiferroelectric liquid crystal reported to date is
It is around 30 °.

The general properties of the anti-ferroelectric liquid crystals synthesized so far are that liquid crystals having a low threshold voltage tend to have a small tilt angle, and liquid crystals having a large tilt angle tend to have a high threshold voltage. strong. Therefore, if a liquid crystal material having both a large tilt angle and a low threshold voltage can be obtained, an antiferroelectric liquid crystal that is extremely effective in practical use can be obtained. The present invention has been made from such a viewpoint, and relates to a novel antiferroelectric liquid crystal material having the above-mentioned two characteristics which are extremely useful in practice.

[0011]

The present invention has the following general formula:
It is a novel antiferroelectric liquid crystal substance represented by (1).

[Chemical 2] (In the formula, n represents an integer of 4, 6, or 8, and C ^* represents an asymmetric carbon).

In the present invention, the general formula of antiferroelectric liquid crystal is represented by C _n H _{2n + 1} -O-Ph-Ph-COO-Ph (3-F) -COO-C * H (CH ₃ ) C _m H When expressed by _{2m + 1} (3-F indicates fluorine substitution to the phenyl group), the threshold voltage and the tilt angle which should be sufficiently satisfied from a practical point of view when n = 9 and the most physical properties are obtained. The present invention has been completed by finding that the liquid crystal becomes a well-balanced liquid crystal. In the present invention, among the compounds represented by the general formula (1), n is preferably 6 or 8 (Examples 2 and 3), and particularly preferably n is 6 (Example 2).

The optically active alcohol used in the present invention is commercially available or can be obtained by optical resolution of a racemate. An example of the method for producing the target liquid crystal compound of the present invention is shown by a reaction formula as follows. (1) C ₉ H ₁₉ -O-Ph-Ph-COOH + SOCl ₂ → C ₉ H ₁₉ -O-Ph-Ph-
COCl (2) AcO-Ph (3-F) -COOH + SOCl ₂ → AcO-Ph (3-F) -CO
Cl (3) AcO-Ph (3-F) -COCl + CH ₃ C * H (OH) C _n H _{2n + 1} → AcO-Ph
(3-F) -COO-C * H (CH ₃ ) C _n H _{2n * 1} (4) AcO-Ph (3-F) -COO-C * H (CH ₃ ) C _n H _{2n + 1} + ( Ph-CH ₂ NH
₂ ) → H-Ph (3-F) -COO-C * H (CH ₃ ) C _n H _{2n + 1} (5) C ₉ H ₁₉ -O-Ph-Ph-COCl + H-Ph (3-F ) -COO-C * H (CH ₃ ) C
_n H _{2n + 1} → target liquid crystal compound

[0014]

The present invention can provide a novel antiferroelectric liquid crystal substance. The novel anti-ferroelectric liquid crystal material and anti-ferroelectric liquid crystal composition provided by the present invention have two excellent properties of low threshold voltage and high tilt angle, and are the three characteristics. It can be used for a liquid crystal display device by utilizing switching between stable states, a clear threshold characteristic, and good memory property.

[0015]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these. Example 1 Preparation of R-3-fluoro-4- (1-methyl-pentyloxycarbonyl) phenyl-4′-n-nonyloxybiphenyl-4-carboxylate (when n = 4 in the general formula (1)) .

(1) Production of 4- (4'-n-nonyloxy) biphenylcarboxylic acid 4- (4'-hydroxy) biphenylcarboxylic acid 10.5 g, n-
15.2 g of nonyl bromide was added to a mixed solution of 1500 ml (milliliter) of ethanol and 200 ml of water, and the mixture was reacted under reflux for 10 hours. Further, 500 ml of water was added and the mixture was stirred for 3 hours. After completion of the reaction, concentrated hydrochloric acid was added to make the solution acidic, and then 500 ml of the solvent was distilled off and cooled to room temperature to obtain a white solid. After washing it thoroughly with water, it was recrystallized from chloroform to give the desired white crystals.
12.7 g was obtained.

(2) Preparation of 4-acetoxy-2-fluorobenzoic acid 4.3 g of 2-fluoro-4-hydroxybenzoic acid and acetic anhydride
8.4 g was mixed in a two-necked flask. Five drops of sulfuric acid were added under water cooling. After the exotherm subsided, the mixture was heated at 80 ° C for 30 minutes. Then, the reaction mixture was poured into cold water, and the precipitated crystals were filtered. The crystals were dried in vacuum and used in the next step. The yield was 4.7 g.

(3) Preparation of 4-acetoxy-2-fluoro-1- (1-methylpentyloxycarbonyl) benzene 4-acetoxy-2-fluorobenzoic acid (1.2 g) was added to thionyl chloride (7 ml) and the mixture was reacted under reflux for 5 hours. Let Then, excess thionyl chloride was distilled off, and then a mixture of 1 ml of pyridine, 4 ml of dry ether and 0.5 g of R-(+)-2-hexanol was added dropwise. After the dropping, the mixture was stirred overnight at room temperature, diluted with 200 ml of ether, and the organic layer was diluted with dilute hydrochloric acid, 1N sodium hydroxide aqueous solution,
It was washed with water in that order and dried over magnesium sulfate. The solvent was distilled off, and the crude target substance was purified by silica gel column chromatography using hexane / ethyl acetate as a solvent to give the target substance 1.0.
got g.

(4) Preparation of 4-hydroxy-2-fluoro- (1-methylpentyloxybenzene) 1.0 g of the compound obtained in (3) above was dissolved in 30 ml of ethanol, and 3 g of benzylamine was added dropwise. The mixture was stirred at room temperature for 24 hours, diluted with 300 ml of ether, washed with diluted hydrochloric acid and water in this order, and dried over magnesium sulfate.
After the solvent was distilled off, the residue was isolated and purified by silica gel column chromatography to obtain 0.5 g of the desired product.

(5) Preparation of 3-fluoro-4- (1-methylpentyloxycarbonylphenyl) -4'-n-nonyloxybiphenyl-4-carboxylate 0.9 g of the compound obtained in the above (1) was added to thionyl chloride. 10 ml was added and the mixture was heated under reflux for 10 hours. After distilling off excess thionyl chloride, 10 ml of pyridine and 25 ml of toluene were added, and then
25 ml of a benzene solution containing 0.5 g of the compound obtained in (4) above was added dropwise, and the mixture was reacted at room temperature for 10 hours. After the reaction is complete, ether
The mixture was diluted with 300 ml, washed with diluted hydrochloric acid, a 1N sodium carbonate aqueous solution and water in this order, and the organic layer was dried over magnesium sulfate. Then, the solvent was distilled off and the residue was isolated by silica gel chromatography. Then, the product was recrystallized from ethanol to obtain 0.6 g of the desired product.

The 1H-NMR spectrum of the desired product obtained in (5) above is shown in FIG. The peak numbers in FIG. 1 correspond to the hydrogen atom numbers in the chemical structure of the target substance shown below. The phases were identified by observing the texture and measuring DSC (differential differential scanning calorimeter). The phase sequence of the compound of the present invention was as described below.

Next, the threshold voltage and tilt angle of the present liquid crystal were measured. The measurement was performed by the following method. A liquid crystal cell with an ITO electrode (cell thickness 2 μm) having a rubbed polyimide thin film was filled with the above compound in an isotropic phase state. The cell was gradually cooled at 1.0 ° C./min to orient the liquid crystal in the SA phase. The cell was installed between the orthogonal deflection plates so that the liquid crystal layer direction was parallel to the analyzer or polarizer, and ± 25V, 0.5 Hz triangular wave voltage was applied to the cell,
The change in the amount of transmitted light was measured by a photomultiplier.

As a result, in the temperature range of 125 ° C. to 61 ° C.,
A double hysteresis response history peculiar to the antiferroelectric phase as shown in FIG. 2 was observed. The minimum and maximum values of light transmittance in the figure are defined as 0% and 100%. The circles in the figure indicate that the transmittance is 10% and 90%, and the voltage at this position is defined as the threshold voltage. The voltage at 90% transmittance when changing from antiferroelectric to ferroelectric state is the threshold voltage VTH1 (V / μm), and the voltage at 90% transmittance when changing from ferroelectric to antiferroelectric state is VTH2 (V / μm)
As a result, the superiority or inferiority of the liquid crystal physical properties is judged by the magnitude of this value. Further, the voltage was applied to rotate the sample until a dark field appeared, and the tilt angle was obtained from the angle. The results are shown in Tables 1 to 3 below.

Comparative Examples 1 and 2 R-3-Fluoro-4- (1-methyl-pentyloxycarbonyl) phenyl-4'-n-octyloxybiphenyl-4-carboxylate (Comparative Example 1) and R-3- Fluoro-4- (1-methyl-pentyloxycarbonyl) phenyl-4'-n-decyloxybiphenyl-4-carboxylate (Comparative Example 2)
In Example 1, 4- (4'-n-octyloxy) biphenylcarboxylic acid or 4- (4'-n-decyloxy) biphenylcarboxylic acid was used in place of 4- (4'-n-nonyloxy) biphenylcarboxylic acid. The target product was produced in the same manner as in Example 1 using an acid. 1H-NMR spectral data, phase series, threshold voltage and tilt angle of these compounds were measured.
The results are shown in Tables 1 to 3.

[0025]

[Chemical 3]

[0026]

[Table 1] NMR spectrum (ppm) Hydrogen number 1 2 3 4 5 6 7 8 Example 1 4.0 7.0 7.6 7.7 8.2 7.1 8.0 5.2 Comparative example 1 4.0 7.0 7.6 7.7 8.2 7.1 8.0 5.2 Comparative example 2 4.0 7.0 7.6 7.7 8.2 7.1 8.0 5.2

[0027]

[Table 2] Phase Sequence Example 1 I (144) SA (127) SC * (125) SCA * (61) Cr Comparative Example 1 I (149) SA (129) SCA * (20) SIA * (-12 ) SX Comparative Example 2 I (141) SA (126) SC * (121) SCA * (1) SIA * (-20) Cr * () The value in parentheses indicates temperature (° C). * In the above phase series, I is isotropic phase, SA is smectic A phase, SC
* Indicates a smectic C phase of a ferroelectric phase, SCA * indicates a smectic C phase of an antiferroelectric phase, and Cr indicates a crystalline phase.

[0028]

[Table 3] Threshold voltage and tilt angle VTH1 (V / μm) VTH2 (V / μm) θ (°) Measurement temperature (° C) Example 1 11.0 7.9 27 115 Comparative example 1 25.0 18.0 30 119 Comparative example 2 14.1 9.6 29 110 Although the liquid crystal of Comparative Example 1 has a relatively large tilt angle, when the threshold voltage is high and the cell gap of the liquid crystal cell is set to 2 μm, a driving voltage of 50 V or more is required and it cannot be practically used. The liquid crystal of Comparative Example 2 is also difficult to drive at a voltage of 30 V or less.

Examples 2-3 R-3-fluoro-4- (1-methyl-heptyloxycarbonyl) phenyl-4'-n-nonyloxybiphenyl-4-carboxylate (Example 2) and R-3- Preparation of fluoro-4- (1-methyl-nonyloxycarbonyl) phenyl-4'-n-nonyloxybiphenyl-4-carboxylate (Example 3) (when n = 6, 8 in the general formula (1)) In Example 1, instead of 4-hydroxy-2-fluoro- (1-methylpentyloxy) benzene, 4-hydroxy-2-fluoro- (1-methylheptyloxy) benzene or 4-hydroxy-2-fluoro- (1-methylnonyloxy)
The target product was produced in the same manner as in Example 1 except that benzene was used. The results of measuring physical properties as in Example 1 are shown in Tables 4 to 6 below.

Comparative Examples 3, 4 R-3-Fluoro-4- (1-methyl-heptyloxycarbonyl) phenyl-4'-n-octyloxybiphenyl-4-carboxylate (Comparative Example 3) and R-3- Fluoro-4- (1-methyl-heptyloxycarbonyl) phenyl-4'-n-decyloxybiphenyl-4-carboxylate (Comparative Example 4)
Production of Example 2 In Example 2, 4- (4'-n-octyloxy) biphenylcarboxylic acid or 4- (4'-n-decyloxy) biphenylcarboxylic acid was used instead of 4- (4'-n-nonyloxy) biphenylcarboxylic acid. The target product was produced in the same manner as in Example 2 using an acid. 1H-NMR spectral data, phase series, threshold voltage and tilt angle of these compounds were measured.
The results are shown in Tables 4-6.

Comparative Examples 5 and 6 R-3-fluoro-4- (1-methyl-nonyloxycarbonyl)
Phenyl-4'-n-octyloxybiphenyl-4-carboxylate (Comparative Example 5) and R-3-fluoro-4- (1-methyl-nonyloxycarbonyl) phenyl-4'-n-decyloxybiphenyl-4 -Production of carboxylate (Comparative Example 6) In Example 3, 4- (4'-n-octyloxy) biphenylcarboxylic acid or 4- (4'-n-octyloxy) biphenylcarboxylic acid was used instead of 4- (4'-n-nonyloxy) biphenylcarboxylic acid. Using'-n-decyloxy) biphenylcarboxylic acid, a target product was produced in the same manner as in Example 2. 1H-NMR spectral data, phase series, threshold voltage and tilt angle of these compounds were measured.
The results are shown in Tables 4-6.

[0032]

[Chemical 4]

[0033]

[Chemical 5]

[0034]

[Table 4] NMR spectrum (ppm) Hydrogen number 1 2 3 4 5 6 7 8 Example 2 4.0 7.0 7.6 7.7 8.2 7.1 8.0 5.2 Comparative example 3 4.0 7.0 7.6 7.7 8.2 7.1 8.0 5.2 〃 4 4.0 7.0 7.6 7.7 8.2 7.1 8.0 5.2 Example 3 4.0 7.0 7.6 7.7 8.2 7.1 8.0 5.2 Comparative Example 5 4.0 7.0 7.6 7.7 8.2 7.1 8.0 5.2 〃 6 4.0 7.0 7.6 7.7 8.2 7.1 8.0 5.2

[0035]

[Table 5] Phase Sequence Example 2 I (133) SA (124) SCA * (14) (-26) Cr Comparative Example 3 I (140) SA (121) SCA * (20) SIA * 〃 4 I ( 110) SA (86) SC * (79) SCA * (65) SIA * Example 3 I (99) SA (70) SC * (66) SCA * (-5) Cr Comparative Example 5 I (131) SA ( 114) SC * (113) SCA * (23) SX 〃 6 I (108) SA (78) SC * (74) SCγ * (58) SCA * (52) Cr * () is the temperature (℃) Indicates. * In the above phase series, I is isotropic phase, SA is smectic A phase, SC
* Indicates a smectic C phase of a ferroelectric phase, SCA * indicates a smectic C phase of an antiferroelectric phase, and Cr indicates a crystalline phase.

[0036]

[Table 6] Threshold voltage and tilt angle VTH1 (V / μm) VTH2 (V / μm) θ (°) Measurement temperature (° C) Example 2 6.0 3.0 32 113 Comparative Example 3 13.0 3.0 29 111 Comparative Example 4 5.3 2.9 27 68 Example 3 5.5 2.5 28 56 Comparative Example 5 15.0 12.0 29 100 Comparative Example 6 4.5 2.5 26 48 The liquid crystal compounds of Comparative Examples 3 and 5 have a high threshold voltage and are difficult to drive at a voltage of 30 V or less. . Further, the tilt angles of the liquid crystals of Comparative Examples 4 and 6 were small.

[Brief description of drawings]

FIG. 1 shows an NMR spectrum of a liquid crystal compound in Example 1.

FIG. 2 shows the optical response of the liquid crystal compound in Example 1 to an applied voltage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Matsumoto 22 Wadai, Tsukuba, Ibaraki Mitsubishi Gas Chemical Co., Ltd.

Claims (2)

[Claims] 1. A novel antiferroelectric liquid crystal substance represented by the following general formula (1). [Chemical 1] (In the formula, n represents an integer of 4, 6, or 8, and C ^* represents an asymmetric carbon). 2. The antiferroelectric liquid crystal substance according to claim 1, wherein n is 6 in the general formula (1).