JPH07100791B2 - Liquid crystal composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid crystal composition used for a liquid crystal display device, a liquid crystal device used for a liquid crystal-optical shutter, or the like, and more specifically, a novel liquid crystal composition having improved response characteristics to an electric field. It is about things.

BACKGROUND ART Liquid crystals have been conventionally applied as electro-optical elements in various fields. Most of the liquid crystal devices currently in practical use are, for example, “Applied Physics” by M. Schadt and W. Helfrich.
Letters "Vo.18, No.4 (1971.2.15), P.127-128" Voltage-Dpendent Optical Activity of a Tw "
TN (twis shown in isted Nematic Liquid Crystal)
ted nematic) type liquid crystal is used.

These are based on the dielectric alignment effect of liquid crystals, and utilize the effect that the average molecular axis direction is directed in a specific direction by an applied electric field due to the dielectric anisotropy of liquid crystal molecules. The optical response speed limit of these devices is said to be milliseconds, which is too slow for many applications. On the other hand, in the application to a large flat panel display, the drive by the simple matrix method is the most effective in consideration of price and productivity. In the simple matrix system, an electrode configuration in which the scanning electrode group and the signal electrode group are configured in a matrix is adopted,
For the driving, a time-division drive method is adopted in which an address signal is sequentially and selectively applied to the scanning electrode group and a predetermined information signal is selectively applied to the signal electrode group in parallel in synchronization with the address signal. To be done.

However, when the above-mentioned TN type liquid crystal is adopted for the element of such a driving system, the scan electrode is selected and the signal electrode is not selected, or the scan electrode is not selected and the signal electrode is selected (so-called “half-area”). A finite electric field is also applied to the selection point "). If the difference between the voltage applied to the selection point and the voltage applied to the semi-selection point is sufficiently large and the voltage threshold value required to align the liquid crystal molecules perpendicularly to the electric field is set to the intermediate voltage value, the display element is Although it operates normally, when the number of scanning lines (N) is increased, the time (duty ratio) that an effective electric field is applied to one selection point while scanning the entire screen (1 frame) Will decrease at a rate of 1 / N. For this reason, the voltage difference as the effective value applied to the selected point and the non-selected point in the case of performing repeated scanning becomes smaller as the number of scanning lines increases, and as a result, lowering of image contrast and crosstalk occur. It is an unavoidable drawback. Such a phenomenon is caused by a liquid crystal having no bistability (a stable state in which liquid crystal molecules are horizontally aligned with respect to an electrode surface, and vertically aligned only when an electric field is effectively applied. Is an inherently unavoidable problem that occurs when (1) is driven by utilizing the temporal accumulation effect (that is, repeated scanning). In order to improve this point, a voltage averaging method, a two-frequency driving method, a multiple matrix method, etc. have already been proposed, but none of them is sufficient, and the display element has a large screen and high density. The current situation is that the number of scanning lines has reached a ceiling because the number of scanning lines cannot be increased sufficiently.

As a solution to these drawbacks of conventional liquid crystal devices, the use of bistable liquid crystal devices is explained by Clark and Lag.
proposed by Erwall (Japanese Patent Laid-Open No. 56-107216, US Pat. No. 4,367,924, etc.). As a bistable liquid crystal, a chiral smectic C phase (Sm
Ferroelectric liquid crystal having C ^* ) or H phase (SmH ^* ) is used. This ferroelectric liquid crystal has a bistable state consisting of a first optical stable state and a second optical stable state with respect to an electric field. Therefore, it is different from the optical modulation element used in the above-mentioned TN type liquid crystal. Differently, for example, the liquid crystal is aligned in the first optically stable state with respect to one electric field vector, and is aligned with the second optically stable state in the other electric field vector. This type of liquid crystal also responds to the applied electric field by
It has the property (bistability) of taking one of the two stable states and maintaining that state when no electric field is applied.

In addition to the above-mentioned characteristic of having bistability, the ferroelectric liquid crystal has an excellent characteristic of high-speed response. This is because the spontaneous polarization of the ferroelectric liquid crystal and the applied electric field directly act to induce the transition of the alignment state, which is 3 to 4 orders faster than the response speed due to the action of the dielectric anisotropy and the electric field.

As described above, the ferroelectric liquid crystal potentially has extremely excellent characteristics, and by utilizing such characteristics, it is considerably essential to many of the problems of the conventional TN type element described above. You get an improvement. In particular, it is expected to be applied to high-speed optical optical shutters and high-density, large-screen displays. For this reason, although extensive research has been conducted on liquid crystal materials having ferroelectricity, the ferroelectric liquid crystal materials developed to date are sufficient for use in liquid crystal elements, including low-temperature operating characteristics and high-speed response. It is hard to say that it has characteristics.

Object of the Invention An object of the present invention is to provide a liquid crystal composition exhibiting a smectic C ^* phase in a low temperature region by mixing a specific liquid crystal compound, and at the same time, to obtain various display characteristics which cannot be obtained by a single liquid crystal compound. A liquid crystal composition having the same and a liquid crystal device using the composition.

SUMMARY OF THE INVENTION That is, the present invention provides the following general formula (I) (In the formula, R ₁ is a linear alkyl group or a linear alkoxy group having 4 to 18 carbon atoms, R ₂ is a linear alkyl group having 1 to 18 carbon atoms, C ^* is an asymmetric carbon atom, and l and m is 1 or 2) and at least one of the optically active liquid crystal compounds represented by the following general formula (II) (In the formula, R ₃ is a linear alkyl group having 4 to 18 carbon atoms or a linear alkoxy group, R ₄ is a linear alkyl group having 1 to 18 carbon atoms, and C ^* is an asymmetric carbon atom.) The present invention provides a liquid crystal composition containing at least one of the optically active liquid crystal compounds represented, and a liquid crystal element comprising the liquid crystal composition arranged between a pair of electrode substrates.

According to the study by the present inventors, by mixing the liquid crystal compounds of the above formulas (I) and (II), the temperature range that gives a chiral smectic phase is It has been found that the display characteristics are improved by expanding the spread and the response speed, especially on the low temperature side.

In particular, the following general formula (III) where l = 1 and m = 2 in the above formula (I) (In the formula, R ₁ and R ₂ are the same as those in formula (I)), and a combination of at least one liquid crystal compound represented by the formula (II) and at least one liquid crystal compound represented by the formula (II). In this case, a liquid crystal composition having particularly excellent characteristics can be obtained. In particular such a liquid crystal composition may form a SmC ^* exhibiting ferroelectric properties in a low temperature range as described below, moreover SmC ^*
At that time, excellent high-speed response can be exhibited.

Hereinafter, the present invention will be described in more detail. In the following description, “%” and “part” representing the quantitative ratio are based on weight.

DETAILED DESCRIPTION OF THE INVENTION The liquid crystal compound represented by the formula (I) is described in the specification of Japanese Patent Application No. 60-247994 by the present inventors, and preferably the following compound described in the specification. General formula (A) (In the above general formula, R ₂ represents a linear, branched or cyclic saturated or unsaturated hydrocarbon group having 1 to 18 carbon atoms. C
^{* Indicates} an asymmetric carbon atom. X represents a removable substituent selected from an OH group, a halogen, a benzyloxy group, a phenoxy group, a toluenesulfonic acid group, an acetyloxy group, and a trifluoroacetyloxy group) via an optically active substance represented by It is preferably formed. For example, it can be synthesized by the following reaction via an optically active substance in which X is an OH group in the above formula (A).

(Here, R ₁ , R ₂ , 1, and m are as defined above.) The liquid crystal compound represented by the general formula (II) has the following general formula (B). (In the above general formula, R ₄ represents a linear, branched, or cyclic saturated or unsaturated hydrocarbon group of 1 to 18. C ^* represents an asymmetric carbon atom. Y represents an OH group or halogen. (Br, Cl,
I), a benzyloxy group, a phenoxy group, a toluenesulfonic acid group, an acetyloxy group, and a trifluoroacetyloxy group, which is a removable substituent selected from the following). Is preferred. For example, in the above formula (B), it can be synthesized by the following reaction via an optically active substance in which Y is an OH group.

(Here, R ₃ and R ₄ have the same meanings as described above.) The structural formulas of the specific liquid crystal compound examples represented by the general formulas (I) and (II) and the phase transition temperatures of the liquid crystals are shown in Table 1 and Table 1 below. 1
Shown in.

The liquid crystal compound is represented by the general formulas (I) and (II), and the present invention is not limited to the compounds listed here.

In the table, the symbols in the column of phase transition temperature indicate the following phases, respectively.

Cryst .: Crystal phase, SmA: Smectic A phase, SmC ^* : Chiral smectic C phase, N: Nematic phase, Ch: Cholesteric phase, Iso: Isotropic phase, Sm1, Sm2, SmA, smectic phase other than SmC ^* (not yet Identification).

The liquid crystal composition of the present invention is preferably formed by mixing at least one 1 to 99% of the liquid crystal compound of the above formula (I) and at least 99 to 1% of the above liquid crystal compound of the formula (II). .

In addition to the liquid crystal compounds of the above formulas (I) and (II), the liquid crystal device of the present invention is combined with a ferroelectric liquid crystal represented by the following formulas (1) to (13) to obtain SmC ^*. It is possible to lower the temperature and expand the temperature range.

In such a case, the total amount of the liquid crystal compound of the above formula (I) and the liquid crystal compound of the above formula (II) is used in a proportion of 1 to 99%, particularly 5 to 99% of the obtained liquid crystal composition. Preferably.

Further, a composition that can be used as a ferroelectric liquid crystal can be obtained by blending with a smectic liquid crystal which is not itself chiral as represented by the following formulas 1) to 5).

In this case, it is preferable to use the liquid crystal compound of the present invention represented by the general formulas (I) and (II) in an amount of 1 to 99% by weight, particularly 5 to 95% by weight of the liquid crystal composition.

Further, the liquid crystal element of the present invention is obtained by disposing the liquid crystal composition of the present invention obtained as described above between a pair of electrode substrates. For example, in order to form a liquid crystal element of simple matrix drive, a scan electrode group may be formed on one substrate and a signal electrode group may be formed on the other substrate.

Hereinafter, the present invention will be described in more detail with reference to examples.

Production Example 1 The liquid crystal compound 3 (p′-decyloxybiphenylcarboxylic acid p ″ (2-ethoxypropyloxycarbonyl) phenyl ester) shown in Table 1 was produced.

That is, 4 g of decyloxybiphenylcarboxylic acid (1.13 ×
20 ml of SOCl ₂ was added to 10 ⁻² mol) and the mixture was heated under reflux for 3.5 hours.
Excessive SOCl ₂ was distilled off to obtain decyloxybiphenylcarboxylic acid chloride.

The obtained acid chloride was dissolved in 10 ml of toluene, and dissolved in 16 ml of pyridine. 2.35 g (1.13 × 10 ^-2 mol) of optically active p-hydroxybenzoic acid 2-ethoxypropyl ester.
The mixture was added dropwise to the mixture, allowed to stand at room temperature for 55 minutes, and then stirred for 3 hours and 50 minutes.

The reaction mixture was extracted into cold water, washed with 6N HCl solution and water, dried and evaporated to remove 4.4 g of p'-decyloxybiphenylcarboxylic acid p "(2-ethoxypropyloxycarbonyl) phenyl ester. After further purification by silica gel column chromatography, recrystallization was performed 1.
8 g of purified product was obtained.

The following IR and NMR data were obtained on the product.

IR: 2940, 2870, 1740, 1610, 1515, 1480, 1395, 1295, 11
35, 1090. ¹ H-NMR: 6.8 to 8.2 ppm (12H), 3.3 to 4.3 ppm (7H), 0.8 to 1.8 ppm
(25H).

Production Example 2 The liquid crystal compound 12 (4 (2′-octyloxypropoxy) phenyl-4′-dodecyloxybiphenyl-4-carboxylate) in Table 2 was synthesized.

85 g of 4-oxybiphenyl was dissolved in 1.5N-NaOH solution 1.5, reacted with 2 mol of methylsulfuric acid so that the temperature did not exceed 60 ° C, and then raised to 70 ° C over 30 minutes. Recrystallized from ethanol, melting point 80.5 ℃
4-methoxybiphenyl crystals (yield 90-95%) were obtained.

11.5 g of 4-methoxybiphenyl was dissolved in 75 ml of freshly distilled carbon disulfide and then cooled to 0-2 ° C,
9.5 g of anhydrous aluminum chloride was quickly added with stirring. Then, 5.8 ml of acetyl chloride was added dropwise over 5 to 10 minutes. Then the temperature was gradually raised to 35 ° C. to complete the reaction. Reflux for about 45 minutes and then cool to 60 ml of cold concentrated hydrochloric acid.
Was added and disassembled. By blowing water vapor into the solvent to remove the solvent, by rapidly cooling with good stirring,
This produced brownish pink crystals. To remove the isomeric 3-ketone, it was extracted twice with 40 ml of ether and then recrystallized from isopropyl alcohol. As a result, the melting point
4-Acetyl-4'-methoxybiphenyl at 156.5 ° C was obtained with a yield of 60-77%.

18 g of 4-acetyl-4'-methoxybiphenyl was dissolved in 285 ml of dioxane and oxidized with dilute sodium hypobromite. Recrystallization from ethanol and acetic acid gave 4'-methoxybiphenyl-4-carboxylic acid with a melting point of 285 ° C.

After refluxing 25 g of 4'-methoxybiphenyl-4-carboxylic acid, 200 ml of acetic acid and 48% bromic acid for 12 to 14 hours, 2.5
Put into the water. After cooling, by collecting the crystals,
4'-Hydroxybiphenylcarboxylic acid having a melting point of 288 to 291 ° C was obtained with a yield of 90 to 95%.

0.01 mol of p-oxybiphenylcarboxylic acid and 0.02 mol of potassium hydroxide were dissolved in 300 ml of alcohol and 3 ml of water.
Then, 1.2 mol of n-dodecyl bromide was added, and the mixture was refluxed for 12 hours. A 10% solution containing 1.12 g of potassium hydroxide was refluxed for 2 hours to be hydrolyzed and then recrystallized with ethanol and glacial acetic acid to obtain 4'-n-dodecyloxybiphenyl-carboxylic acid.

4'-n-dodecyloxybiphenylcarboxylic acid 1.23 g
To the mixture was added thionyl chloride (40 ml) and the mixture was heated under reflux for 5 hours. Thionyl chloride was distilled off, 40 ml of dry benzene was further added, and the mixture was distilled off again. After adding 40 ml of dry pyridine and cooling, a solution of 1.37 g of hydroquinone mono (2'-dodecyloxypropyl) ether dissolved in 36 ml of dry benzene was added dropwise, and after stirring for 16 hours, the mixture was heated under reflux for 4 hours. After cooling
Add 150 ml of 10% HCl aqueous solution and extract with benzene.
_It was washed with a ₂ CO ₃ aqueous solution and water, and dried over anhydrous Na ₂ SO ₄ . By distilling off benzene and recrystallizing with ethanol,
(4 (2'-octyloxypropoxy) phenyl-
4'-dodecyloxybiphenyl-4-carboxylate) was obtained. The following IR and NMR data were obtained on the product.

IR (cm ^-1 ): 2920, 2840, 1730, 1600, 1520, 1290, 1200, 1085, 76
Five.

NMR: 8.3-6.9ppm (12H), 4.0-3.5ppm (7H), 1.6-0.9ppm
(41H).

Example 1 The liquid crystal compound 3 and the liquid crystal compound 12 obtained in the above Production Examples 1 and 2 were mixed. The change in phase transition temperature (temperature rising process) of the obtained liquid crystal composition is shown in FIG. 1 as a phase diagram. Further, FIG. 2 shows the change in spontaneous polarization of the composition depending on the composition.

Spontaneous polarization is described by K. Miyasato et al. “Direct measurement method of spontaneous polarization of ferroelectric liquid crystal by triangular wave” (Journal of the Japan Society of Applied Physics 22 and 10).
Issue, L (661) 1983, (“Direct Method with Triangul
ar Waves for Measuring Spontaneous Polarization
in Ferroelectric Liquid Crystal ", as described by
K. Miyasato et al. (Jap.J.Appl.Phys.22, No.10, L661
(1983))).

As is clear from FIG. 1, when the liquid crystal compounds 3 and 12 are mixed in a ratio of 1: 2, the temperature range of SmC ^* ) is greatly expanded,
Keeps SmC ^* relatively stable even at supercooling temperatures.

The response speed of the above liquid crystal composition (1: 2 mixture) was measured. That is, the liquid crystal composition is sandwiched between a pair of electrode substrates that have been subjected to a rubbing treatment on a polyimide coating covering the electrodes,
With a liquid crystal layer thickness of 2 μm, a voltage of 10 V was applied as a peak-to-peak voltage, and an optical response under a crossed Nicols was detected to measure the response speed.

The results are shown in Table 3 below.

As can be seen from the above, the mixed liquid crystal composition (3 + 12 (1: 2)) according to the present invention has a faster response and a better response speed than a single liquid crystal compound even at a low temperature.

Example 2 Liquid crystal compound 3 and liquid crystal compound 15 were mixed at a ratio of 28:72 to obtain a liquid crystal composition. This liquid crystal composition is
It showed a SmC ^* phase at ~ 137 ° C. A device was prepared using this composition in the same manner as in Example 1, and the response speed was changed under the same conditions.
When measured at a temperature of 80 ° C., it was 210 μsec and the characteristics were improved compared to the case where a single liquid crystal compound was used. (Note that the response speed of the liquid crystal compound 15 alone at 100 ° C. is 270 μsec.) Example 3 The liquid crystal compound 7 and the liquid crystal compound 12 shown in Table 1 were
Mixing was performed at a ratio of 30:70 to obtain a liquid crystal composition. 55 to 95 ° C
Had an SmC ^* phase.

Using this liquid crystal composition, a device was prepared in the same manner as in Example 1, and the measurement was carried out under the same conditions at a response speed of 80 ° C., and it was 200 μsec, and the response speed was improved.

Example 4 Liquid crystal compounds 3, 10 and 12 were mixed at a ratio of 31: 7: 62 to obtain a liquid crystal composition. A device was prepared using this composition in the same manner as in Example 1, and the response speed was measured at a temperature of 70 ° C. under exactly the same conditions. As a result, 190 μsec was obtained and the characteristics were improved as compared with the case of using the liquid crystal compound 10. It was

Effects of the Invention As can be seen from the above examples, by mixing the liquid crystal compounds represented by the general formulas (I) and (II) according to the present invention, as compared with the individual liquid crystal compounds,
A liquid crystal composition having a chiral smectic C phase spread to the low temperature side and excellent characteristics such as an improved response speed which are not found in a single liquid crystal compound can be obtained.

[Brief description of drawings]

FIG. 1 shows the liquid crystal compound 3 and the liquid crystal compound 12 according to Example 1.
Phase diagram showing the change in composition of the phase transition temperature due to the mixing of
Similarly, FIG. 2 is a correlation diagram with the composition of spontaneous polarization. Representative figure: Figure 1

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kazuo Yoshinaga 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Kenji Shinjo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (56) References JP 62-123141 (JP, A) JP 62-209044 (JP, A)

Claims (3)

[Claims] 1. The following general formula (I): (In the formula, R ₁ is a linear alkyl group or a linear alkoxy group having 4 to 18 carbon atoms, R ₂ is a linear alkyl group having 1 to 18 carbon atoms, C ^* is an asymmetric carbon atom, and l is And m is 1 or 2) and at least one optically active liquid crystal compound represented by the following general formula (II) (In the formula, R ₃ is a linear alkyl group or a linear alkoxy group having ₄ to 18 carbon atoms, R ₄ is a linear alkyl group having 1 to 18 carbon atoms, and C ^* is an asymmetric carbon atom.) And at least one kind of the optically active liquid crystal compound represented by the formula. 2. In the general formula (I), m is 2 and l
And at least one kind of optically active liquid crystal compound in which 1 is 1,
The liquid crystal composition according to claim 1, containing at least one kind of the optically active liquid crystal compound represented by the general formula (II). 3. The following general formula (I) (In the formula, R ₁ is a linear alkyl group or a linear alkoxy group having 4 to 18 carbon atoms, R ₂ is a linear alkyl group having 1 to 18 carbon atoms, C ^* is an asymmetric carbon atom, l and m are 1 or 2) and at least one of the optically active liquid crystal compounds represented by the general formula (II) (In the formula, R ₃ is a linear alkyl group having 4 to 18 carbon atoms or a linear alkoxy group, R ₄ is a linear alkyl group having 1 to 18 carbon atoms, and C ^* is an asymmetric carbon atom.) A liquid crystal device comprising a liquid crystal composition containing at least one kind of an optically active liquid crystal compound represented by the formula, and a liquid crystal composition containing the liquid crystal composition, the liquid crystal composition being disposed between a pair of electrode substrates.