JPS6312056B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel substance, and more particularly to a constituent substance of a liquid crystal composition that has negative dielectric anisotropy and a significantly large value. Liquid crystal materials with negative dielectric anisotropy are used in light-scattering type liquid crystal display devices that utilize the dynamic scattering of the liquid crystal layer when voltage is applied, and utilize the birefringence of liquid crystals by controlling the tilt of the liquid crystal. The so-called DAP type liquid crystal display device displays multicolors using a polarizing plate.
Furthermore, it is already well known that it is an important component of a so-called guest-host type color display device that uses a liquid crystal material containing a specific dye. The present invention provides components and compositions of novel liquid crystal compositions having negative and large dielectric anisotropy, which are suitable for forming liquid crystal materials used in these liquid crystal display devices. In the above-mentioned liquid crystal display device, it is necessary to lower the minimum voltage required for the liquid crystal to start responding to applied voltage, that is, the threshold voltage, and to show sufficient contrast for visual viewing. In order to reduce the required operating voltage, the dielectric anisotropy (Δε) of the liquid crystal material is required to have a large negative value.
However, for example, in MBBA (methoxybenzylidene butylaniline), which is well known as a liquid crystal with negative induced anisotropy, △ε is approximately -0.5, and in liquid crystals made of benzoic acid phenyl esters, △ε is at most -0.4. It is. Therefore, it is desired to develop a liquid crystal material in which Δε has an even larger negative value. A substance having one cyano group on the side of the molecule has been proposed as one of the substances that can meet such demands. i.e. bis-(4'-n-alkylbenzylidene)
-2-cyano-1,4-phenylenediamine (JP 52-71393) and 4-alkyl-4'-biphenylcarboxylic acid 4-
Alkyl 2-cyanophenyl ester (Japanese Unexamined Patent Publication No. 118450/1983), etc. have been filed and published. For substances with one of these CN groups, the value of △ε is certainly the same as the previous one.
Although it shows a large negative value compared to MBBA, etc., the liquid crystal temperature range is higher than room temperature, so it cannot be used alone.In order to maintain the liquid crystal state at room temperature, the liquid crystal temperature range must be at room temperature. -Used in combination with other liquid crystal materials with small Δε values. However, when these substances are added to such an extent as to bring about the effect of lowering the operating voltage as described above, other physical properties, such as response speed, are undesirably affected. It is presumed that this is because these substances have relatively large molecular weights, which increases their viscosity. Therefore, in order to reduce the amount added as much as possible and obtain a sufficient effect, it is desirable to use a substance in which Δε has a larger negative value. The present inventors focused on this point and searched for a liquid crystal compound having two CN groups on the same side, and as a result, they invented a compound of the following formula and filed a patent application (Japanese Patent Application No. 115591/1989). issue). (However, in the above formula, R ₁ and R ₂ are hydrogen or carbon number 1
~10 alkyl group or alkyloxy group) This compound has a dielectric anisotropy of more than -20, which is clear when compared with the dielectric anisotropy of the compound of formula () above, which is -4. , it can be said that it has an extremely large negative dielectric anisotropy value.
However, since the compound of formula () has a relatively high melting point (C-N point), its amount (use ratio) should not be used too much as a component of a liquid crystal composition that maintains a liquid crystal state near room temperature. I couldn't raise it. Therefore, there is a practical limit to the magnitude of the negative dielectric anisotropy of a liquid crystal material containing the compound of formula (). The present inventors have previously developed a novel compound with the general formula (However, in the above formula, R ¹ represents a straight chain alkyl group having 3 to 5 carbon atoms, and R ² represents a straight chain alkyl group having 1 to 10 carbon atoms.) 3-n-alkyloxy-6 represented by -(trans-4'-alkylcyclohexanecarboxy)-phthalonitrile (Patent application 145508/1983, 140710/1983, 1984-)
9917). The present inventors further explored the surroundings of the compounds of the above formula () and found that the compound of the following general formula () can be used for the same purposes as the compound of the formula (), resulting in the present invention. That is, the present invention is based on the general formula (However, in the above formula, R ¹ and R ² represent an alkyl group having 1 to 10 carbon atoms.) 3-n-alkyloxy-6-(trans-4'-alkyloxycyclohexanecarboxy)-phthalonitrile and a liquid crystal composition having a negative dielectric anisotropy that includes at least one kind of the present compound. The compound () has a large negative dielectric anisotropy reaching about -17 to -18 in the molten state in a nematic liquid crystal material. Furthermore, this compound is chemically stable, and the fact that it is a colorless substance that does not absorb light with a wavelength of 360 nm or longer means that its stability will not be impaired even when combined with any other known practical liquid crystal. means. A specific example of this compound () is 3-n-propyloxy-6-(trans-4'-
butoxycyclohexanecarboxy)-phthalonitrile, 3-n-butoxy-6-(trans-
4'-butoxycyclohexanecarboxy)-phthalonitrile (mp80.3℃), 3-n-pentyloxy-6-(trans-4'-butoxycyclohexanecarboxy)-phthalonitrile (mp62.5℃),
3-n-hexyloxy-6-(trans-4'-
butoxycyclohexanecarboxy)-phthalonitrile, 3-n-propyloxy-6-(trans-4'-pentyloxycyclohexanecarboxy)-phthalonitrile, 3-n-butoxy-6-
(trans-4'-pentyloxycyclohexanecarboxy)-phthalonitrile, 3-n-pentyloxy-6-(trans-4'-pentyloxycyclohexanecarboxy)-phthalonitrile (mp61.5℃), 3-n-propyl Oxy-6-
(trans-4′-hexyloxycyclohexanecarboxy)-phthalonitrile (mp94.3~94.5
°C), 3-n-butoxy-6-(trans-4'-
hexyloxycyclohexanecarboxy)-phthalonitrile (mp81.1-81.7℃), 3-n-pentyloxy-6-trans-4'-hexyloxycyclohexanecarboxy)-phthalonitrile (mp96.4-96.6℃), 3- n-hexyloxy-6
-(trans-4'-hexyloxycyclohexanecarboxy)-phthalonitrile, 3-n-hexyloxy-6-(trans-4'-heptyloxycyclohexanecarboxy)-phthalonitrile, and the like. These compounds () are produced by the following method. First, 2,3-dicyano-p-hydroquinone is treated with an alkylating agent such as p-toluenesulfonic acid alkyl ester or alkyl bromide in the presence of an alkali to obtain its monoalkyl ether, and trans-4- An alkyloxycyclohexanecarboxylic acid halide is reacted in a basic solvent such as pyridine. 2,3- of this raw material
Dicyano-p-hydroquinone is a substance that has been known for a long time, and is described in the literature Thiele and Meisenheimer,
Berichte, 33, 675, (1900). Trans-4-alkyloxycyclohexanecarboxylic acid is also synthesized by hydrogenating the corresponding substituted benzoic acid. The compound () of the present invention generally has a smaller tendency to form a liquid crystal phase than the compound of the general formula (). However, it can also be used in combination with nematic liquid crystal materials or with other nematic liquid crystal materials, preferably with compounds of the general formula (), to produce liquid crystal mixtures having a highly negative dielectric anisotropy.
These liquid crystal mixtures enable use at lower voltages than conventional liquid crystal materials in display elements due to the so-called guest-host effect, DAP effect, and DSM effect. The liquid crystal material that becomes the base for adding the compound () is a liquid crystal whose Δε is a negative value, or a liquid crystal whose value is small even if it is positive. For example, Schiff liquid crystal compounds such as MBBA (methoxybenzylidene butylaniline) and EBBA (ethoxybenzylidene butylaniline), ester liquid crystals that do not have a cyano group in the rose position (for example, p-methoxybenzoic acid
p'-pentylphenyl ester, 4'-alkylcyclohexanecarboxylic acid p'-alkoxyphenyl ester, etc.), p-methoxy-p'-butylazoxybenzene, p-methoxy-p'-ethylazoxybenzene, etc. Examples include various azoxybenzene-based liquid crystal compounds. In addition, because of the large negative dielectric anisotropy of the compound (), by adding a small amount of this compound to a liquid crystal material with positive dielectric anisotropy, it is possible to improve the dielectric properties without changing the other properties of the base liquid crystal. It serves to reduce only the anisotropy value. The present invention will be explained in more detail with reference to Examples below. Example 1 (In formula (), R ¹ is n-C ₅ H ₁₁ and R ² is n-C ₆ H ₁₃
2,3-dicyano-p-hydroquinone 50g,
After stirring and heating 375 ml of 5% aqueous sodium hydroxide solution and 113 g of p-toluenesulfonic acid n-pentyl ester under reflux for 7 hours in a three-necked flask, the mixture was transferred to a separating funnel, and toluene and aqueous sodium hydroxide solution were added. , 2,3-dicyano-p-hydroquinone monopentyl ether and unreacted 2,3-dicyano-p-hydroquinone were extracted into the alkaline aqueous layer. Most of the hydroquinone is removed by acidifying the alkaline aqueous layer with hydrochloric acid, collecting the precipitated solid, dissolving it in 1 part toluene, and heating it. When the filtered toluene solution is cooled, crude 2,3-dicyano-p-hydroquinone monopentyl ether precipitates, which is separated and recrystallized from aqueous methanol to give mp150-153.
C. crystals were obtained (yield: 21 g). On the other hand, trans-4
19.5 g of -hexyloxycyclohexanecarboxylic acid (mp48-50°C) was heated with 5.0 ml of thionyl chloride under reflux for 40 minutes, and excess thionyl chloride was distilled off to obtain an acid chloride. This was added dropwise as a 100 ml toluene solution into a solution of 20 g of 2,3-dicyano-p-hydroquinone monopentyl ether dissolved in 300 ml of pyridine while cooling with water and stirring. 50
After heating and stirring at ℃ for 1 hour, cool, add ice and 6N hydrochloric acid to make acidic, add 200ml of toluene, filter to remove solids, separate the layers to take the toluene layer, wash this with water, 2N Cleaning with caustic soda water,
After washing again with water, toluene was distilled off, and the residue was recrystallized from ethanol to obtain the target product, 3-pentyloxy-6-(trans-4'-n-hexyloxycyclohexanecarboxy)-phthalonitrile, as a colorless product. 16.5 g of crystals were obtained. It melts at a melting point of 96.4-96.6°C and produces an isotropic liquid. When this isotropic liquid is cooled, it forms a smectic liquid crystal phase, and when it is reheated, it forms a smectic liquid crystal phase.
Produces an isotropic liquid at 66° to 66.4°C. Moreover, the smectic liquid crystal phase crystallizes after a while, and the resulting crystals melt at 80.2 to 80.4°C to become an isotropic liquid. Moreover, the elemental analysis values are in good agreement with the calculated values as shown below.

[Table] Example 2 (Manufacture of formula () where R ¹ is n-C ₄ H ₉ R ² is n-C ₆ H ₁₃ ) 50 g of 2,3-dicyano-p-hydroquinone,
After stirring and heating 380 ml of 5% aqueous sodium hydroxide solution and 106 g of p-toluenesulfonic acid n-butyl ester under reflux for 7 hours in a three-necked flask, the mixture was transferred to a separating funnel, and toluene and aqueous caustic soda solution were added. , 3-dicyano-p-hydroquinone monobutyl ether and unreacted 2,3-dicyano-p-hydroquinone were extracted into the alkaline aqueous layer. The alkaline aqueous layer is acidified with hydrochloric acid, the precipitated solid is collected, and it is dissolved in toluene of 1 and heated.
-dicyano-p-hydroquinone is removed and the toluene layer is cooled to precipitate 2,3-dicyano-p-hydroquinone monobutyl ether, which is separated and recrystallized from aqueous methanol to give m.
Crystals with p·157 to 159°C were obtained (yield: 22 g). Meanwhile, 20.0 g of trans-4-hexyloxycyclohexanecarboxylic acid was added to 50 ml of thionyl chloride under reflux.
After heating for 40 minutes, excess thionyl chloride was distilled off to obtain acid chloride. This was made into a 100 ml toluene solution and was added dropwise to the above solution of 19.5 g of 2,3-dicyano-p-hydroquinone monobutyl ether dissolved in 300 ml of pyridine while cooling with water and stirring. 1 at 50℃
After heating and stirring for a period of time, cool, add ice and 6N hydrochloric acid to make acidic, add 200ml of toluene, remove excess solids, separate the layers to obtain a toluene layer, wash this with water, wash with 2N caustic soda water, After washing again with water, toluene is distilled off, and the residue is recrystallized from ethanol to obtain the target product, 3-butyloxy-6-
Colorless crystals of (trans-4'-n-hexyloxycyclohexanecarboxy)-phthalonitrile
18.7g was obtained. This material melts at 81.1-81.7°C and becomes an isotropic liquid. When this liquid is cooled, crystallization occurs before the substance reaches a temperature at which it exhibits a liquid crystal phase, so the liquid crystal phase cannot be observed. Furthermore, the crystals obtained by elemental analysis are in good agreement with the calculated values as shown below.

[Table] Example 3 (Manufacture of formula () where R ¹ is n-C ₃ H ₇ R ² is n-C ₆ H ₁₃ ) 2,3-dicyano-p-hydroquinone 50 g,
After stirring and heating 375 ml of 5% aqueous sodium hydroxide solution and 100 g of p-toluenesulfonic acid n-propyl ester under reflux for 7 hours in a three-necked flask,
The mixture was transferred to a separatory funnel, toluene and aqueous caustic soda were added thereto, and 2,3-dicyano-p-hydroquinone monopropyl ether and unreacted 2,3-dicyano-p-hydroquinone were extracted into the alkaline aqueous layer. The alkaline aqueous layer is acidified with hydrochloric acid, the precipitated solid is collected, and it is dissolved in toluene (1) and heated to produce 2,3-dicyano-
Since p-hydroquinone monopropyl ether precipitated, it was separated and recrystallized from water-containing methanol to obtain crystals with a m.p. of 175-176°C (yield: 19
g). On the other hand, 20.0 g of trans-4-hexyloxylcyclohexanecarboxylic acid was heated with 50 ml of thionyl chloride under reflux for 40 minutes, and excess thionyl chloride was distilled off to obtain an acid chloride. This was made into a 100 ml toluene solution and was added dropwise to the above solution of 17.5 g of 2,3-dicyano-p-hydroquinone monopropyl ether in 300 ml of pyridine while cooling with water and stirring. After heating and stirring at 50℃ for 1 hour, cool and add 6N with ice.
Add hydrochloric acid to make acidic, add 200ml of toluene, filter to remove solids, separate the layers, take toluene layer, wash with water, wash with 2N caustic soda water, wash again with water, and add toluene. The target product 3- is distilled off and the residue is recrystallized from ethanol.
19.3 g of colorless crystals of propyloxy-6-(trans-4'-n-hexyloxycyclohexanecarboxy)-phthalonitrile were obtained. This thing is
It melts at 94.3 to 94.5°C to become an isotropic liquid, and when this liquid is cooled, crystallization occurs before the substance reaches the temperature at which it exhibits a liquid crystal phase, so the liquid crystal phase cannot be observed. In exactly the same way as above, in formula (), R ¹ is C ₂ H ₅ ,
R ² is C ₆ H ₁₃ , i.e. 3-ethyloxy-6-
(Trans-4'-n-hexyloxycyclohexanecarboxy)-phthalonitrile was produced.
Its melting point was 115-116.2°C. Example 4 (Use Example 1) A liquid crystal mixture consisting of 2 parts of p-methoxybenzoic acid p'-pentylphenyl ester and 1 part of p-hexyloxybenzoic acid p'-pentylphenyl ester was a nematic liquid crystal at 15 to 48°C. Has a temperature range, △
ε is +0.1. Using this as a base liquid crystal, add 0.44 g of 3-n-pentyloxy-6-(trans-4'-hexyloxycyclohexanecarboxy)-phthalonitrile obtained in Example 1 to 9.56 g of it.
A mixture of g has a clearing point of 44.2°C and does not crystallize at room temperature. This mixture was sealed in a cell with a vertically aligned electrode distance (gap) of approximately 9 μm, and the voltage-current characteristics were measured at a frequency of 1 KHz, and a value of -0.57 was obtained for Δε. By extrapolation from this result, the compound of formula () used here (where R ¹ or C ₅ H ₁₁ and R ² is C ₆ H ₁₃
The value of -15.1 is obtained as △ε of the object) itself. Mixture of above as host and as guest
When the so-called guest-host effect was observed by adding 1% by weight of dye D-52 manufactured by BDH, the threshold voltage for this effect was 3.6V and the saturation voltage was 5.0V. This is because the compound of formula () has a high negative △ε value in the liquid crystal phase, which results in a change in the orientation state of the liquid crystal phase (from an orientation perpendicular to the electrode plane to an orientation parallel to the electrode plane). This shows that the voltage required for (change in) was significantly reduced. Example 5 (Use Example 2) 33.5 parts of p-methoxybenzoic acid p'-n-pentylphenyl ester, 16.5 parts of p-hexyloxybenzoic acid p-n-pentylphenyl ester, trans-4-n-butylcyclohexane Carboxylic acid p-ethoxyphenyl ester 16.5 parts, trans-4-n-butylcyclohexanecarboxylic acid
The △ε of the liquid crystal composition consisting of 33.5 parts of p'-hexyloxyphenyl ester is negative, and its N-point is 58.4°C, and no crystal precipitation was observed even if it was stored at -5°C for a long time. do not have. To this, 1% by weight of anthraquinone dye D=52 manufactured by BDH was added as a guest, and the thickness was vertically aligned.
The guest-host effect was observed by enclosing it in a 10 μm cell and measuring the change in light transmittance due to voltage using light with a wavelength of 540 nm, and its operating characteristics were found to be 4.8 V and saturated. The voltage is
It was 6.3V. On the other hand, 3-n-propoxy-6-(trans-
4′-hexyloxycyclohexanecarboxy)
Phthalonitrile 5 parts 3-n-butoxy-6-
A mixture of three compounds: 5 parts of (trans-4'-hexyloxycyclohexanecarboxy)phthalonitrile and 5 parts of 3-n-pentyloxy-6-(trans-4'-hexyloxycyclohexanecarboxy)phthalonitrile, total 15 A liquid crystal composition was obtained. Δε of this liquid crystal composition is −
3.8, and the N-I point was 50.3°C. Using this liquid crystal composition as a host, we added 1% by weight of the same guest dye (i.e. D-52) and observed the guest-host effect in the same manner to determine the operating characteristics, and found that the threshold voltage was The voltage was 1.8V, and the saturation voltage was 2.8V. This value is much lower than the value when the compound of the present invention is not added. The fact that the threshold voltage and saturation voltage can be lowered by adding the compound of formula () of the present invention in this way means that the operating voltage when performing positive color display due to the guest-host effect is significantly increased. This is a very significant point when using liquid crystals. Example 6 (Use Example 3) Same base liquid crystal as Example 5, namely p-methoxybenzoic acid p-pentylphenyl ester 33.5
parts, p-hexyloxybenzoic acid p'-n-pentylphenyl ester 16.5 parts, trans-4-n-
3-pentyloxy-6 of the present invention is added to 75 parts of a liquid crystal consisting of 16.5 parts of butylcyclohexanecarboxylic acid p'-ethoxyphenyl ester and 33.5 parts of trans-4-n-butylcyclohexanecarboxylic acid p'-hexyloxyphenyl ester. -(trans-4-hexyloxycyclohexanecarboxy)-phthalonitrile (in the formula (), R=
_{C5H11 ,} ^R1 = _C6H13 ) 5 parts, 3-pentyloxy-6'(trans-4 _- butyloxycyclohexanecarboxy)-phthalonitrile (()
In the formula, R = C ₅ H ₁₁ , R ¹ = C ₄ H ₉ ) 5 parts,
and 3-n related to the invention of the applicant's earlier application.
-Butoxy-6-(trans-4'-butylcyclohexanecarboxy)-phthalonitrile 5 parts, 3
-n-butoxy-6-(trans-4-pentylcyclohexanecarboxy)-phthalonitrile 5
Section, (the above two are patent application No. 53-145508) and 3-n
A liquid crystal composition was prepared by adding 5 parts of -bentyloxy-6-(trans-4-hexylcyclohexanecarboxy)-phthalonitrile (Japanese Patent Application No. 53-140710). Δε of this liquid crystal composition is −4.3,
The NI point was 47°C. this as host
1% by weight of dye D-52 manufactured by BDH as a guest
When the guest-host effect was observed in the same manner as in Example 5, the threshold voltage was found to be
The voltage was 1.5V, and the saturation voltage was 2.4V.

Claims (1)

[Claims] 1. General formula (However, in the above formula, R ¹ and R ² represent an alkyl group having 1 to 10 carbon atoms.) 3-n-alkyloxy-6-(trans-4'-alkyloxycyclohexanecarboxy)-phthalonitrile kind. 2 General formula characterized by reacting mono-n-alkyl ether of 2,3-dicyano-p-hydroquinone with trans-4-alkyloxycyclohexanecarboxylic acid halide in a basic solvent (However, in the above formula, R ¹ and R ² represent an alkyl group having 1 to 10 carbon atoms.) Manufacturing method. 3 General formula (However, in the above formula, R ¹ and R ² represent an alkyl group having 1 to 10 carbon atoms.) 3-n-alkyloxy-6-(trans-4'-alkyloxycyclohexanecarboxy)-phthalo A liquid crystal composition with negative dielectric anisotropy, characterized in that it contains at least one type of nitrile.