JP5609035B2 - Manufacturing method of liquid crystal material - Google Patents

Description

  The present invention relates to a method for producing a liquid crystal material having a high specific resistance value.

  Liquid crystal display elements have come to be widely used from consumer applications such as liquid crystal televisions, mobile phones and personal computers to industrial applications. These products have a relatively long product life of several years to several tens of years, and operate normally during this period. Therefore, liquid crystal materials used for these products are required to have high stability. A specific stability index of a liquid crystal material is a specific resistance value. In order for a liquid crystal display element to operate normally, the specific resistance value of the liquid crystal material used for the liquid crystal display element must be sufficiently high, and deterioration over time must be suppressed.

Many studies have been made so far to improve the stability of liquid crystal materials. For example, as a method for removing moisture and metal ions in the liquid crystal material, a method of bringing the liquid crystal material into contact with silica gel (see Patent Document 1), a method of bringing into contact with activated alumina (see Patent Document 2), and treatment with an ion exchange resin. A method (see Patent Document 3) and a method of contacting with zeolite (see Patent Document 4) are disclosed. Furthermore, by inserting a liquid crystal compound between a pair of electrodes facing each other and applying an electric field, metal ions such as Na ⁺ and K ^{+ having} relatively high mobility due to the electric field, SO ₄ ²⁻ , NO ₃ ⁻ , Cl ^{− and the like.} And the like (see Patent Documents 5 to 7). These purification methods are methods for removing impurities already contained in the liquid crystal material.

  On the other hand, there are various demands for liquid crystal materials such as high-speed response and high contrast. These physical properties cannot be achieved by a single compound, and a plurality of liquid crystal compounds are mixed to meet the demand as a liquid crystal composition. At that time, it is important that each liquid crystal compound is accurately weighed and its mixing ratio is adjusted to the target value. This is because if an error occurs in the mixing ratio, the physical properties change, and a liquid crystal composition that satisfies the requirements cannot be prepared.

  Here, many liquid crystal compounds are solid at room temperature. For this reason, when the solvent is almost distilled off from the liquid crystal compound in a solution state dissolved in the solvent, crystallization proceeds at a stretch and the whole becomes an integral solid. If the liquid crystal compound is used without completely distilling off the solvent, the liquid crystal compound is not desirable because it causes problems such as reduced stability. For this reason, it is necessary to remove the solvent taken into the crystal of the liquid crystal compound under reduced pressure. However, if the obtained solid mass is large, the solvent taken in does not volatilize and cannot be removed. Further, since the weighing at the time of preparing the liquid crystal composition must be performed while crushing the lump, the operation becomes extremely difficult, and the weighing accuracy cannot be ensured. On the other hand, when the liquid crystal compound is prepared as a powder, it is easy to distill off the solvent and make fine adjustments during weighing. However, the purification method described above involves treating a liquid crystal material in a liquid crystal state or a solution state, and the liquid crystal compound obtained after the treatment does not become powder.

  In order to easily obtain a liquid crystal compound as a powder, recrystallization is effective, and there are many examples in which a liquid crystal compound is actually purified by recrystallization (Patent Document 8). Recrystallization is performed by dissolving a compound in a solvent, precipitating crystals using a difference in solubility due to a temperature difference, evaporation of the solvent, a change in the mixing ratio of the solvent, and the like, and filtering it. At this time, uniform and fine crystals can be obtained by adjusting the deposition rate of the crystals. The powdered liquid crystal compound thus obtained has fine particles, so that the solvent can be easily distilled off and can be easily swollen, so that weighing is easy and fine adjustment of the addition amount is possible. it can. However, generation of static electricity is often a problem in the recrystallization process.

  In order to obtain a liquid crystal material having a high specific resistance value, each liquid crystal compound that constitutes the liquid crystal compound must also have a high specific resistance value. When recrystallization is performed as a final step before weighing, From the requirement, the liquid crystal compound after the recrystallization must have a high specific resistance value. In order to obtain a liquid crystal compound having a high specific resistance value by recrystallization, it is known that recrystallization is particularly preferably performed from a solvent having a low conductivity such as hexane, heptane or toluene. However, when these solvents with low conductivity are used, static electricity generated during crystal precipitation, stirring, filtration, etc. is charged, and there is a risk of causing a serious disaster such as a fire due to ignitable discharge. In order to enhance the safety, it is useful to use a solvent having a high conductivity and suppress electrostatic charge. However, a solvent having a high conductivity generally tends to dissolve ionic components and the like, so that there is a problem that the specific resistance value of the liquid crystal compound after recrystallization does not reach a practical level due to the influence of these components. Thus, although a safe and practical method for obtaining a liquid crystal compound having a high specific resistance value by recrystallization is eagerly desired, no specific solution has been reported so far.

JP-A-62-210420 Japanese Patent Laid-Open No. 58-1774 JP 52-59081 A JP 63-261224 A Japanese Patent Laid-Open No. 50-108186 Japanese Patent Laid-Open No. 51-11069 Japanese Patent Laid-Open No. 4-86812 JP 2007-176818 A

  It is to provide a highly safe production method of a liquid crystal compound having a high specific resistance value by recrystallization operation, and to provide a liquid crystal composition using the liquid crystal compound obtained by this production method. An object of the present invention is to provide a highly safe recrystallization method for obtaining a liquid crystal compound having a specific resistance value.

  As a result of intensive studies on the target compound of the present invention, the present inventors have found that the above-described problems can be solved by a specific production method, and have completed the present invention.

  The present invention relates to (i) the general formula (1)

(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkenyloxy group having 2 to 6 carbon atoms,
a represents 1, 2 or 3;
A ¹ and A ² are each independently (a) a trans-1,4-cyclohexylene group (one methylene group present in this group or two or more methylene groups not adjacent to each other is —O— or May be replaced by -S-),
(B) a 1,4-phenylene group (one —CH═ present in the group or two or more non-adjacent —CH═ may be replaced by a nitrogen atom), 3,5-difluoro -1,4-phenylene group, and (c) 1,4-bicyclo (2.2.2) octylene group, naphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, and 1,2 , 3,4-tetrahydronaphthalene-2,6-diyl group, a group selected from the group consisting of chroman-2,6-diyl group, the group (a), group (b) or group (c) The hydrogen atoms contained in each may be substituted with a fluorine atom, a trifluoromethyl group, a trifluoromethoxy group or a chlorine atom, and when a plurality of A ¹ are present, they may be the same or different. ,
Z ¹ is a single _{bond, -CH 2 CH 2 -, -} CH = CH -, - CH 2 O -, - OCH 2 -, - CF 2 O -, - OCF 2 -, - represents a COO- or -OCO- However, a plurality of Z ¹ may be the same or different,
Y ¹ is a hydrogen atom, a fluorine atom, a chlorine atom, a trifluoromethyl group, a trifluoromethoxy group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or carbon. The alkenyloxy group of number 2-6 is represented. The specific resistance value of the compound represented by formula (A-1) and (A-2)

20% by mass of the compound represented by the general formula (1) was added to the liquid crystal composition (M-1) having a specific resistance value of 1.0 × 10 ¹³ Ω · m or more. When the specific resistance value of the compound represented by the general formula (1) is less than 8.0 × 10 ¹¹ Ω · m, it is defined by the general formula (1). Alcohol compounds, ketone solvents, ester solvents, ether solvents or nitrile solvents in which the total concentration of lithium ion, sodium ion, ammonium ion, potassium ion, magnesium ion and calcium ion is 1.0 ppb or less. The specific resistance value of the compound represented by the general formula (1) after recrystallization is 8 by distilling off the solvent used for recrystallization after recrystallization using a single or mixed solvent selected from .0x1 Process for producing a compound represented by the general formula of the crystalline state shown over ^{11 Ω · m (1),} (ii) recrystallization method performed when the liquid crystal is added a liquid crystal compound obtained by (iii) the present production method A liquid crystal composition in a state is provided.

  By the production method of the present invention, a liquid crystal compound having a high specific resistance value can be obtained by a safe recrystallization operation. Therefore, the present invention is useful in that a liquid crystal composition for producing a liquid crystal display element that can be used for a long period of time can be obtained. Furthermore, it is useful in that the risk of disaster during the recrystallization operation is reduced.

In the general formula (1), at least one of A ^{1 and} A ² is a group (A)

Or group (B)

It is preferable to select from. In group (B),

Is more preferable.

When at least one of A ¹ or A ² is selected from the group (A), it is preferable to select A ² from the group (A).

When at least one of A ^{1 and} A ² is selected from the group (A), Y ¹ is preferably a fluorine atom, R ¹ is preferably a methyl group, an ethyl group, a propyl group, a butyl group or a pentyl group, and Z ¹ Is preferably a single bond, —CH ₂ CH ₂ —, —CF ₂ O— or —OCF ₂ —.

When at least one of A ^{1 and} A ² is selected from the group (B), R ¹ and Y ¹ are each independently an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, or a carbon number Represents an alkoxy group having 1 to 6 carbon atoms or an alkenyloxy group having 2 to 6 carbon atoms, but includes a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a vinyl group, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, pentoxy group, 3-butenyloxy and 4-pentenyl group are preferable, ^{Z 1} is a single _{bond, -CH 2 CH 2 -, -} CH 2 O -, - OCH 2 -, - CF 2 O- or OCF ₂ - are preferable.

The specific resistance value of the liquid crystal composition obtained by adding 20% by mass of the compound represented by the general formula (1) to the liquid crystal composition (M-1) having a specific resistance value of 1.0 × 10 ¹³ Ω · m or more is obtained. In the case of less than 8.0 × 10 ¹¹ Ω · m, a liquid crystal display device using a liquid crystal composition containing the compound represented by the general formula (1) may cause a display defect. When the specific resistance value of the liquid crystal composition obtained by adding 20% by mass of the compound represented by the general formula (1) to 1) is 8.0 × 10 ¹¹ Ω · m or more, such a situation does not occur. Operates without problems even for long-term use. In order to obtain higher reliability, it is desirable to increase the specific resistance value. However, if the refining process is repeated in order to increase the specific resistance value, the yield will be reduced and it will not be possible to manufacture at low cost. Therefore, practically, 20 mass of the compound represented by the general formula (1) after purification is added to the liquid crystal composition (M-1) having a specific resistance value of 1.0 × 10 ¹³ Ω · m or more. % Is preferably 8.0 × 10 ¹¹ Ω · m, preferably 1.0 × 10 ¹² Ω · m, preferably 5.0 × 10 ¹² Ω · m, 1.0 × 10 ¹³ Ω · m is preferable. This specific resistance value is preferably as high as possible, but the liquid crystal compound is organic and has its limitations.

When the specific resistance value of the compound represented by the general formula (1) before purification used in the present invention has a sufficiently high specific value, it is not necessary to perform the present purification. If it is too low, the present invention needs to be repeated several times. Therefore, the lower limit is preferably 9.9 × 10 ¹¹ Ω · m, preferably 8.0 × 10 ¹¹ Ω · m, more preferably 5.0 × 10 ¹¹ Ω · m, and 1.0 × 10 ¹¹ Ω · m. m is preferable, 1.0 × 10 ¹⁰ Ω · m is preferable, 1.0 × 10 ⁹ Ω · m is preferable, 1.0 × 10 ⁸ Ω · m is preferable, and the upper limit value is 9.9 × 10 ¹¹ Ω M is preferable, 8.0 × 10 ¹¹ Ω · m is preferable, 5.0 × 10 ¹¹ Ω · m is preferable, 1.0 × 10 ¹¹ Ω · m is preferable, and 1.0 × 10 ¹⁰ Ω · m is preferable. Is preferable, 1.0 × 10 ⁹ Ω · m is preferable, and 1.0 × 10 ⁸ Ω · m is preferable.

  Before recrystallization, it is not necessary to perform other purification methods or recrystallization as long as it has sufficient purity to withstand use. However, in order to obtain a liquid crystal compound with sufficient purity, other purification methods must be used in advance. It is preferable to carry out the method and recrystallization. In addition, the compound represented by the general formula (1) before purification used in the present invention is not particularly defined as chemical purity, but it is used without any other purification after the purification of the present invention. It is preferable to use a gas chromatography (column: DB-1, carrier gas: helium) with an area ratio of 95% or more, preferably 97% or more, more preferably 99% or more, and 99.5%. The above is desirable, and 99.8% or more is more desirable. At this time, a compound that does not cause a decrease in specific resistance value, or a compound whose characteristics have already been confirmed and whose influence has been confirmed and an allowable concentration is defined is represented by the general formula (1) in the determination of chemical purity. You may include in the compound represented.

  Moreover, it is preferable to perform column chromatography before recrystallization to remove ionic impurities that cause a decrease in specific resistance value. It is preferable to use silica gel, alumina, or both as a purification agent used for column chromatography. The developing solvent used at that time is preferably a single or mixed solvent selected from hexane, heptane or toluene.

  For recrystallization, a solvent having a total concentration of lithium ions, sodium ions, ammonium ions, potassium ions, magnesium ions and calcium ions of 1.0 ppb or less may be used, but the preparation method is not limited. When the sum of the above concentrations of the solvent to be used exceeds 1.0 ppb, it can be reduced to 1.0 ppb or less by treating with an ion exchange resin, for example.

  The solvent used for recrystallization is selected from methanol, ethanol, 1-propanol, 2-propanol, acetone, 2-butanone, ethyl acetate, diethyl ether, tetrahydrofuran, methyl-t-butyl ether, acetonitrile or propionitrile. Single or mixed solvents are preferred, and single or mixed solvents selected from methanol, ethanol, acetone or 2-butanone are more preferred.

  Recrystallization can be performed by dissolving the compound represented by the general formula (1) in a solvent and then cooling to a temperature lower than the temperature at which it was dissolved. Although it is preferable to completely dissolve the compound, an undissolved portion may remain within the range in which the subsequent crystallization and filtration operations are not hindered. In cooling, it may be cooled rapidly or slowly. After cooling, the temperature may be kept constant, or crystals may be precipitated while further cooling. Moreover, when precipitating a crystal | crystallization, you may stir or may stand still. Stirring is preferred when the crystal sizes are aligned and the crystal size is not too large. As another recrystallization method, the compound represented by the general formula (1) can be dissolved in a highly soluble solvent, and then added with a solvent having low solubility for crystallization.

  The solvent after the recrystallization can be distilled off under reduced pressure at room temperature or with heating. At this time, the heating means is not particularly limited, and any method can be adopted as long as it can be controlled within a range of several degrees from the set temperature. For ease of implementation, a method of immersing a container filled with a liquid crystal compound in a temperature-controlled container filled with a solution, a method of heating the container with a mantle heater or the like, and a flow of flowing heated liquid on a shelf loaded with a liquid crystal compound The method of providing a path and heating by this is mentioned. Further, when the solvent is distilled off, the liquid crystal compound is cooled by the heat of vaporization, so that the above-mentioned means can be carried out with an unheated solution for the purpose of reducing the temperature drop. It is also possible to remove the solvent without using these methods and without controlling the temperature. In order to shorten the working time, the lower limit temperature is preferably 20 ° C, preferably 30 ° C, preferably 35 ° C, and more preferably 40 ° C. The upper limit temperature is preferably higher because the solvent distillation rate increases when the temperature is raised, but if the temperature is too high, decomposition or oxidation of the liquid crystal compound occurs, which is not preferred. Further, heating to a temperature higher than the melting point is not preferable because when it is cooled to room temperature after drying, it becomes an integral solid and cannot be obtained as a powder. For this reason, less than melting | fusing point is preferable, 60 degreeC is preferable, 55 degreeC is preferable, 50 degreeC is preferable, 45 degreeC is preferable and 40 degreeC is preferable. When the solvent is distilled off, the container or shelf containing the liquid crystal compound may be stationary or may be moved. However, it is preferable to rotate or vibrate from the viewpoint of efficiency.

  The crystal obtained by the production method of the present invention and the crystal of the present invention are then mixed with another liquid crystal compound without further purification to prepare a liquid crystal composition. After forming the liquid crystal composition, filtration or treatment with an adsorbent may be performed as necessary.

  It is preferable that the liquid crystal compound does not contain the solvent used for recrystallization, but it may be any concentration that does not adversely affect the liquid crystal composition. The concentration is preferably 200 ppm or less, preferably 100 ppm or less, preferably 50 ppm or less, and more preferably 20 ppm or less.

EXAMPLES Hereinafter, although an Example is given and this invention is further explained in full detail, this invention is not limited to these Examples. Further, “%” in the compositions of the following examples and comparative examples means “mass%”. An ion chromatograph was used for analysis of the ion concentration in the solvent, and the concentrations of lithium ion, sodium ion, ammonium ion, potassium ion, magnesium ion and calcium ion were calculated by an absolute calibration curve method. The specific resistance value of the liquid crystal composition was obtained by putting the liquid crystal composition in a measurement cell and measuring the resistance value when a voltage (DC) of 1 V was applied at 25 ° C.
Example 1 Recrystallization of Compound Represented by Formula (1-1) (1)
Formula (A-1) and (A-2)

In a liquid crystal composition (M-1) having a specific resistance of 1.0 × 10 ¹³ Ω · m,

The specific resistance value of the liquid crystal composition to which 20% of the compound represented by the formula was added was 1.0 × 10 ¹¹ Ω · m. 25 g of the compound represented by the formula (1-1) was purified by column chromatography (filler: silica gel and alumina, developing solvent: hexane), and the solvent was distilled off under reduced pressure. The residue was dissolved in 50 mL of acetone having a total concentration of lithium ion, sodium ion, ammonium ion, potassium ion, magnesium ion and calcium ion of 0.13 ppb, and was crystallized by stirring at 5 ° C. for 10 minutes. It was allowed to stand for 16 hours in a freezer at 0 ° C. To filter out the crystals, it was poured into Nutsche with a filter. When the charge potential of the crystal obtained on the filter was measured, it was 0.0 kV, and no electrostatic charge was observed. The obtained crystals were transferred to an eggplant flask, depressurized with a vacuum pump (266 Pa), and the solvent was distilled off while rotating the eggplant flask. At this time, the flask was immersed in a 40 ° C. hot water bath to control the temperature. After 20 hours, 22.9 g of the compound represented by the formula (1-1) was obtained as powder crystals. The specific resistance value of the liquid crystal composition obtained by adding 20% of the obtained compound represented by the formula (1-1) to the liquid crystal composition (M-1) having a specific resistance value of 1.0 × 10 ¹³ Ω · m. Was 1.4 × 10 ¹² Ω · m.

(Comparative Example 1) Recrystallization of the compound represented by the formula (1-1) (2)
In Example 1, the same operation was performed using acetone whose total concentration of lithium ions, sodium ions, ammonium ions, potassium ions, magnesium ions and calcium ions was 1.35 ppb for recrystallization. The specific resistance value of the liquid crystal composition obtained by adding 20% of the compound represented by the formula (1-1) to the liquid crystal composition (M-1) was 6.0 × 10 ¹¹ Ω · m.

(Comparative example 2) Recrystallization (3) of the compound represented by the formula (1-1)
In Example 1, the same operation was performed using hexane for recrystallization. As a result, the absolute value of the charging potential of the filtered crystal was 22.0 kV or more. When this charged crystal generates a brush discharge with the conductor, it is estimated that the discharge energy is equal to or higher than the minimum ignition energy (0.24 mJ) of hexane. Therefore, if the conditions overlap, there is a danger of igniting the solvent hexane. In addition, when using a metal instrument during filtration, if there is a lack of grounding, an unstable charge is generated in the metal instrument due to electrostatic induction, charge separation, etc., causing an ignitable spark discharge. The possibility is considered and it is very dangerous.

Example 2 Recrystallization of Compound Represented by Formula (1-1) (4)
In Example 1, 50 mL of ethanol having a total concentration of lithium ion, sodium ion, ammonium ion, potassium ion, magnesium ion and calcium ion of 0.20 ppb was used for recrystallization, and the same operation was performed. The charged potential of the crystal during filtration was 0.0 kV, and the yield was 23.9 g. The specific resistance value of the liquid crystal composition obtained by adding 20% of the compound represented by the formula (1-1) to the liquid crystal composition (M-1) was 2.0 × 10 ¹² Ω · m.

Example 3 Recrystallization of Compound Represented by Formula (1-1) (5)
In Example 1, 25 mL of acetone having a total concentration of lithium ion, sodium ion, ammonium ion, potassium ion, magnesium ion and calcium ion of 0.13 ppb and lithium ion, sodium ion, ammonium ion, potassium ion, The same operation was performed using a mixed solvent composed of 25 mL of ethanol having a total concentration of magnesium ions and calcium ions of 0.20 ppb. The charged potential of the crystal during filtration was 0.0 kV, and the yield was 23.6 g. The specific resistance value of the liquid crystal composition obtained by adding 20% of the compound represented by the formula (1-1) to the liquid crystal composition (M-1) was 2.0 × 10 ¹² Ω · m.

Example 4 Treatment of Solvent with Ion Exchange Resin 100 mL of acetone with a total concentration of lithium ion, sodium ion, ammonium ion, potassium ion, magnesium ion and calcium ion of 1.56 ppb and lithium ion, sodium ion and ammonium ion A mixed solvent A consisting of 100 mL of ethanol having a total concentration of potassium ion, magnesium ion and calcium ion of 1.84 ppb was prepared. A glass chromatograph tube was filled with 5 g of a mixture of a cation exchange resin and an anion exchange resin, and 50 mL of the mixed solvent A was passed through to wash the ion exchange resin. Thereafter, 150 mL of the mixed solvent A was passed through and collected in a clean glass flask. When the obtained mixed solvent was analyzed, the total concentration of lithium ions, sodium ions, ammonium ions, potassium ions, magnesium ions and calcium ions was 0.15 ppb. Using this mixed solvent, the same operation as in the method described in Example 1 was performed. The charged potential of the crystal during filtration was 0.0 kV, and the yield was 23.4 g. The specific resistance value of the liquid crystal composition obtained by adding 20% of the compound represented by the formula (1-1) to the liquid crystal composition (M-1) was 1.1 × 10 ¹² Ω · m.

(Example 5)
In Example 1, the same operation was performed using the compounds shown in the following table instead of the compound represented by Formula (1-1). In addition, the specific resistance value in a table | surface is a thing of the liquid crystal composition which added 20% of each compound to the liquid crystal composition (M-1).

Claims (14)

General formula (1)

(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkenyloxy group having 2 to 6 carbon atoms,
a represents 1, 2 or 3;
A ¹ and A ² are each independently (a) a trans-1,4-cyclohexylene group (one methylene group present in this group or two or more methylene groups not adjacent to each other is —O— or -S-))
(B) a 1,4-phenylene group (one —CH═ present in the group or two or more non-adjacent —CH═ may be replaced by a nitrogen atom), 3,5-difluoro -1,4-phenylene group, and (c) 1,4-bicyclo (2.2.2) octylene group, naphthalene-2,6-diyl group, decahydronaphthalene-2,6-diyl group, and 1,2 , 3,4-tetrahydronaphthalene-2,6-diyl group, a group selected from the group consisting of chroman-2,6-diyl group, the group (a), group (b) or group (c) The hydrogen atoms contained in each may be substituted with a fluorine atom, a trifluoromethyl group, a trifluoromethoxy group or a chlorine atom, and when a plurality of A ¹ are present, they may be the same or different. ,
Z ¹ is a single _{bond, -CH 2 CH 2 -, -} CH = CH -, - CH 2 O -, - OCH 2 -, - CF 2 O -, - OCF 2 -, - represents a COO- or -OCO- However, a plurality of Z ¹ may be the same or different,
Y ¹ is a hydrogen atom, a fluorine atom, a chlorine atom, a trifluoromethyl group, a trifluoromethoxy group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or carbon. The alkenyloxy group of number 2-6 is represented. The specific resistance value of the compound represented by formula (A-1) and (A-2)

20% by mass of the compound represented by the general formula (1) was added to the liquid crystal composition (M-1) having a specific resistance value of 1.0 × 10 ¹³ Ω · m or more. When the specific resistance value of the compound represented by the general formula (1) is less than 8.0 × 10 ¹¹ Ω · m, it is defined by the general formula (1). Alcohol compounds, ketone solvents, ester solvents, ether solvents or nitrile solvents in which the total concentration of lithium ion, sodium ion, ammonium ion, potassium ion, magnesium ion and calcium ion is 1.0 ppb or less. The specific resistance value of the compound represented by the general formula (1) after recrystallization is 8 by distilling off the solvent used for recrystallization after recrystallization using a single or mixed solvent selected from .0x1 Method for producing a compound represented by the general formula of the crystalline state shown over ^{11 Ω} · m (1). In general formula (1), at least one of A ^{1 and} A ² is

The manufacturing method of Claim 1 showing. The production method according to claim 1 or 2, wherein Y ¹ in the general formula (1) represents a fluorine atom. In General Formula (1), R ¹ is a methyl group, an ethyl group, a propyl group, a butyl group, or a pentyl group, and Z ¹ is a single bond, —CH ₂ CH ₂ —, —CF ₂ O—, or —OCF ₂ —. The production method according to claim 1, which represents In general formula (1), at least one of A ^{1 and} A ² is

The manufacturing method of Claim 1 showing. In the general formula (1), R ¹ and Y ¹ are each independently methyl, ethyl, propyl, butyl, pentyl, vinyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, 3 - represents a butenyloxy group or a 4-pentenyl group, ^{Z 1} is a single _{bond, -CH 2 CH 2 -, -} CH 2 O- or -OCH ₂ - the method of claim 1 or 5, wherein represents the. In general formula (1), at least one of A ^{1 and} A ² is

The manufacturing method of Claim 1 or 6 showing. A single solvent selected from methanol, ethanol, 1-propanol, 2-propanol, acetone, 2-butanone, ethyl acetate, diethyl ether, tetrahydrofuran, methyl-t-butyl ether, acetonitrile or propionitrile. Or it is a mixed solvent, The manufacturing method in any one of Claims 1-7. The production method according to claim 8, wherein the solvent used for recrystallization is a single or mixed solvent selected from methanol, ethanol, acetone or 2-butanone. The manufacturing method characterized by refine | purifying the compound represented by General formula (1) by column chromatography before performing the manufacturing method in any one of Claims 1-9. The method according to claim 1, wherein a solvent treated with an ion exchange resin is used for recrystallization. The manufacturing method in any one of Claims 1-11 in which the specific resistance value of the compound represented by General formula (1) after recrystallization shows 1.0 * 10 < ¹² > (omega | ohm) * m or more. The manufacturing method of the liquid-crystal composition containing the compound represented by General formula (1) manufactured by the method in any one of Claims 1-12. The recrystallization method performed when implementing the manufacturing method in any one of Claims 1-12.