JPH0655693B2 - Biphenyl ester compound and ferroelectric smectic liquid crystal composition using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a biphenyl ester compound used for a display element or an electro-optical element and a ferroelectric smectic liquid crystal composition using the same.

[Prior Art] A liquid crystal display element using a nematic liquid crystal conventionally used for a display unit of a watch calculator or the like has a response speed which is much slower than that of another display element, for example, a light emitting diode. Applications in areas where response is required, such as optical communication and liquid crystal display devices for printer heads, have been limited.

Recently, a liquid crystal display device using a smectic liquid crystal exhibiting ferroelectricity has been reported as a liquid crystal display device exhibiting high-speed response (for example, NAClark, STLagerwall, Appl.Phys.
Lett. 36 , 899 (1980)) is attracting attention.

Ferroelectric smectic liquid crystals include a chiral smectic C phase and a chiral smectic H phase, which have a layered structure in which liquid crystal molecules are tilted rather than perpendicular to the stacking direction of the layers. The liquid crystal molecules are arranged so that this tilt direction spirals with respect to the stacking direction of the layers, and spontaneous polarization occurs in a direction parallel to this layer and perpendicular to the liquid crystal molecules, resulting in ferroelectricity. Indicates. This helical structure is considered to be the cause of the ferroelectricity.
A material exhibiting ferroelectricity exhibits responsiveness as a ferroelectric substance to an electric field, and reorients by inverting the direction of spontaneous polarization according to the direction of the electric field. In addition, an element using a ferroelectric smectic liquid crystal has a memory property, and researches using this memory property for high-density display are being actively conducted.

[Problems to be Solved by the Invention] As a ferroelectric smectic liquid crystal, conventionally, many compounds of a Schiff base type as shown below have been studied.

p-decyloxybenzylidene-p'-amino-2-methylbutyl-cinnamic acid ester (DOBAMBC).

However, since such a Schiff base type compound is easily hydrolyzed, there is a problem that it is easily decomposed by water.

Further, as an ester type compound exhibiting a chiral smectic C phase, a compound represented by the following general formula (II) has been known.

(GW Gray et al. Mol.Cryst.Liq.Cryst., 1976, 37 189-211) (R is a linear alkyl group having 5 to 10 carbon atoms) Although this ester compound can withstand moisture, the temperature at which it exhibits a chiral smectic phase is considerably higher than room temperature. However, it has a drawback that the display element must be heated before use.

[Means for Solving the Problem] The present invention has been made to solve the above-described problems, and has the general formula (In the formula, R represents a linear alkyl group having 4 to 6 carbon atoms)
And a biphenyl ester compound represented by the formula (I) and at least one biphenyl ester compound represented by the general formula (I).

In the present invention, the linear carbon number represented by R in the general formula (I) is preferably 4 to 6 because the melting point is high when it is small and the viscosity is high when it is too large.

C ₃ H ₇ -CH (CH ₃ ) -CH ₂ -is a 2-methylpentyl group, and D
Form and L form are present, but the racemic form is preferable because it does not affect the helical pitch in the case of a liquid crystal composition.

The compound represented by the general formula (I) is used for a ferroelectric smectic liquid crystal display device or an electro-optical device, so that it has another chiral smectic C phase in a desired temperature range. Alternatively, it is appropriately mixed with a smectic liquid crystal or an optically active substance and used as a ferroelectric smectic liquid crystal composition. Further, nematic liquid crystal, non-liquid crystal, dichroic dye or the like may be added for adjusting the spiral pitch or for displaying color. When the content of the compound represented by the general formula (I) in the ferroelectric smectic liquid crystal composition of the present invention is too large, the spontaneous polarization of the composition tends to be small, and when it is too small, Has a small effect of lowering the lower limit temperature of the ferroelectric smectic phase, and is therefore 1 to 80 wt%, preferably 2 to 40 wt%.

Examples of the counterpart compound used as a ferroelectric smectic liquid crystal composition by mixing with the compound of the general formula (I) of the present invention include the following.

In the following examples, R ^* represents an optically active alkyl group or alkoxy group, R has no relation to R of the present invention, and represents a linear or branched alkyl group or alkoxy group, which is identical to one compound. , R ^* and R are not limited to the same group.

In addition to these, various known liquid crystal or non-liquid crystal liquid crystal additives can be used in combination, and examples thereof include the following.

And compounds obtained by substituting a part of hydrogen atoms of these benzene ring, cyclohexane ring and the like with halogen, cyano group, methyl group and the like.

Examples of this are compounds such as the following compounds having a negative dielectric anisotropy. In the following examples, R has nothing to do with R of the present invention and represents a linear or branched alkyl group having 1 to 12 carbon atoms, and even if the same R is shown in one compound, They are not necessarily the same groups.

Examples of the dichroic dye include dyes used in so-called guest-host type liquid crystal display devices such as trisazo type and anthraquinone type.

The ferroelectric liquid crystal display element or the electro-optical element is arranged so as to sandwich the liquid crystal layer, and at least one substrate is transparent and has a plurality of substrates having electrodes on the whole surface or a part thereof, and surrounds the liquid crystal layer. And a seal member formed between the electrode substrates. In the liquid crystal display element, the thickness between the substrates is 0.
5 to 20 μm is preferable. Further, the substrates may be subjected to alignment control processing parallel to each of them. As a means for controlling the orientation, an orientation control film may be applied partially or entirely on the electrode substrate. As the orientation control film, a polymer material such as polyimide having a refractive index of 1.5 or more is preferable. Furthermore, at least one polarizer is preferably attached to the liquid crystal element. At least two electrode substrates are required, but a larger number of electrode substrates may be stacked and used.

The compound of the present invention can be synthesized, for example, by the route shown below.

4-Bromophenyl (III) and 2-methyl-1-bromopentane are subjected to Grignard reaction to give compound (IV), which is reacted with acetyl chloride and aluminum chloride to give compound (V). Further, a compound (VI) is obtained by a haloform reaction, and reacted with an excess of thionyl chloride to give a compound (VII). This is reacted with compound (VIII) to synthesize (I).

[Examples] Example 1 49.5 g of 2-methyl-1-bromopentane (III) and 9.7 g of magnesium in an ether form were used as Grignard reagents in ether by a conventional method and added to an ether solution of 48.9 g of 4-bromobiphenyl. And stirred for 4 hours. After adding dilute hydrochloric acid, the organic layer extracted with ether is washed with water, dried over anhydrous magnesium sulfate, and the solvent is distilled off. Recrystallization from hexane gave 26.1 g of 4- (2-methylpentylbiphenyl (IV).

Acetyl chloride (9.5 g) was added to a mixture of 4- (2-methylpentylbiphenyl (IV) (26.1 g), aluminum chloride (16.1 g) and dichloroethane (70 ml), and the mixture was stirred overnight. This was added to dilute hydrochloric acid and extracted with dichloroethane. After washing with water, it is dried over anhydrous magnesium sulfate and the solvent is distilled off.
Recrystallization from hexane gave 20.0 g of 4- (2-methylpentyl) biphenyl-methylketone (V).

4- (2-Methylpentyl) biphenyl-methylketone (V) (20.0 g) was dissolved in dioxane (150 ml) to give bromine (35.2 g, N).
It was added dropwise to a mixture of 25.0 g aOH and 120 ml water. After stirring for 3 hours, hydrochloric acid is added to make the mixture acidic and the white precipitate formed is removed. After washing this with water, recrystallized from ethanol,
14.0 g of 4- (2-methylpentyl) biphenyl-4'-carboxylic acid (VI) was obtained.

4- (2-methylpentyl) biphenyl-4'-carboxylic acid (VI) 2.8 g (0.01 mol) and thionyl chloride 4.8 g (0.04 mol),
After heating 8 ml of carbon tetrachloride under reflux for 6 hours, excess thionyl chloride and the solvent were distilled off to obtain an acid chloride (VII). To a solution of acid chloride (VII) in toluene, 1.8 g (0.01 mol) of 4-pentyloxyphenol and 1.5 g of pyridine were added, and the mixture was stirred for 6 hours. , Wash in order of water. After the organic layer was dried over anhydrous sodium sulfate, the solvent was distilled off,
A solid was obtained. This was recrystallized from ethanol, further subjected to toluene-activated alumina chromatography, and further recrystallized from ethanol to obtain the desired 4-pentyloxyphenyl-4- (2-methylpentyl) biphenyl-4'-carboxylic acid ester. Obtained.

Yield 2.7g Yield 60.8% By observation under a polarization microscope with a hot stage, this compound changed from a smectic C phase to a nematic phase at 165.1 ° C at 75.1 ° C and from a nematic phase to an isotropic liquid at 164.2 ° C. I understood. As shown in Table 1, when compared with the compound of Comparative Example 1 having an n-hexyl group, the temperature showing the smectic C phase was low, and it was closer to room temperature. Further, when compared with the compound having a 2-methylbutyl group (Comparative Example 2), the compound of Comparative Example 2 exhibits a smectic C phase only when the temperature is lowered, but this compound also exhibits the smectic C phase in a wide temperature range when the temperature is raised. .

The IR spectrum (KBr tablet) of this compound is shown in FIG.

Example 2 Instead of 4-pentyloxyphenol in Example 1, 4-butyloxyphenol was used, and 4-butyloxyphenyl-4- (2-methylpentyl) biphenyl-4′-carboxylic acid ester was similarly prepared. Obtained.

Yield 2.8g Yield 65.2% Observation by a polarizing microscope with a hot stage revealed that this compound changed from an isotropic liquid to a nematic phase at 173.2 ° C at 63.2 ° C and from a nematic phase to a smectic C phase at 64.6 ° C. I understood.

Comparing this with a compound having a 2-methylbutyl group as shown in Table 1, it is found that the compound of the present invention induces a smectic C phase by converting it to a 2-methylpentyl group. IR spectrum of this compound (KBr
The lock is shown in FIG.

Example 3 In place of 4-pentyloxyphenol in Example 1, 4-hexyloxyphenol was used, and similarly 4-
Hexyloxyphenyl-4- (2-methylpentyl) biphenyl-4'-carboxylic acid ester was obtained.

Yield 2.9 g Yield 63.6% By observation under a polarizing microscope with a hot stage, it was found that this compound changed from a crystal at 51.7 ° C to a nematic phase at 162.5 ° C to an isotropic liquid.

Comparing this with a compound having a 2-methylbutyl group as shown in Table 1, it is found that the temperature range of the smectic C phase is wide.

The IR spectrum (KBr tablet) of this compound is shown in FIG.

As can be seen from Table-3, as compared with the composition A, the composition B containing the compound of the present invention has a significantly lower minimum temperature of the chiral smectic C phase, and exhibits the chiral smectic C phase in a wide temperature range.

As can be seen from Table 3, in comparison with the composition A, the composition B containing the compound of the present invention has a significantly lower minimum temperature of the chiral smectic C phase, and exhibits the chiral smectic C phase in a wide temperature range.

Example 5 The compound of Example 1 and p-decyloxy benzylidene-p′-ami
Put no-2-methylbutyl-cinnamate (DOBAMBC) in a sample tube and leave it in an atmosphere of temperature 80 ° C and humidity 90% for 20 hours,
The change in melting point before and after that was examined. Since DOBAMBC is susceptible to hydrolysis due to the Schiff base type, the melting point was lowered by 3.6 ° C, whereas the compound of Example 1 only lowered the melting point by 0.3 ° C, indicating that there is no practical problem. .

EFFECTS OF THE INVENTION The present invention provides a chemically stable biphenyl ester compound represented by the general formula (I) having a smectic C phase at room temperature and a ferroelectric smectic containing at least one compound. By providing the liquid crystal composition, it has an excellent effect that a display element or an electro-optical element which is excellent in reliability and can be driven at room temperature can be formed.

[Brief description of drawings]

FIG. 1, FIG. 2, and FIG. 3 are IR spectrum diagrams of the compounds of Example 1, Example 2, and Example 3.

Claims (2)

[Claims] 1. A general formula (In the formula, R represents a linear alkyl group having 4 to 6 carbon atoms)
A biphenyl ester compound represented by. 2. General formula (In the formula, R represents a linear alkyl group having 4 to 6 carbon atoms)
A ferroelectric smectic liquid crystal composition comprising at least one biphenyl ester compound represented by: