KR20100070311A - Method for producing liquid crystal composition - Google Patents

Abstract

Disclosed is a method for producing a liquid crystal composition which is useful as a constituting member of a liquid crystal display device. This method for producing a liquid crystal composition is characterized in that two or more kinds of liquid crystal compounds, at least one of which has a melting point higher than 30°C, are irradiated with a microwave. This method for producing a liquid crystal composition enables to efficiently produce a liquid crystal composition wherein two or more kinds of liquid crystal compounds are mixed in a short time. A liquid crystal composition produced by this method has high reliability from the viewpoint of specific resistance.

Description

Manufacturing method of liquid crystal composition {METHOD FOR PRODUCING LIQUID CRYSTAL COMPOSITION}

This invention relates to the manufacturing method of the liquid crystal composition useful as a structural member of a liquid crystal display element.

The liquid crystal display element is used for clocks, electronic calculators, various measuring instruments, automobile panels, word processors, electronic notebooks, printers, computers, televisions, and the like. Typical examples of the liquid crystal display include TN (twisted nematic) type, STN (super twisted nematic) type, DS (dynamic light scattering) type, GH (guest host) type or FLC (ferroelectric liquid crystal) capable of fast response. Can be mentioned. Moreover, as a drive system, multiplex drive is generally used from the conventional static drive, and the simple matrix system and the active matrix system have been put to practical use in recent years.

The liquid crystal composition used for these can be normally made by mixing two or more types of compounds, and the physical properties (nematic phase temperature range, refractive index anisotropy (Δn), dielectric anisotropy (Δε), viscosity, elastic constant, etc.) of the liquid crystal composition and electrical Depending on the display method and the driving method of the liquid crystal device for the purpose of optical characteristics (response time, threshold voltage, steepness of the VT curve, etc.), the mixing ratio is determined to match various values, but in most cases It is necessary to have high reliability for heat, light, moisture, and the like. In addition, especially in the case of the active matrix driving method, it is important that the voltage holding ratio VHR is sufficiently high. In order to increase the reliability, specific resistance, and voltage retention (VHR) of the liquid crystal composition, high reliability and voltage retention (VHR) need to be achieved for each of the individual liquid crystal compounds constituting the composition. However, even when a liquid crystal compound having high reliability, specific resistance and voltage retention (VHR) is used, the quality may be deteriorated when the liquid crystal composition which is a mixture thereof is produced.

As a manufacturing method of a liquid crystal composition, the method of melt-mixing by heating, and the method of removing an organic solvent after melt | dissolving and mixing a liquid crystal compound in the organic solvent is proposed (refer patent document 1). However, in the methods proposed to these, quality often deteriorates. For example, in dissolution mixing by heating, the liquid crystal compound is oxidatively decomposed by oxygen at the time of heating, thereby significantly lowering the specific resistance and voltage retention (VHR) of the liquid crystal composition. Moreover, liquid crystal upper limit transition temperature may be reduced and the physical property and electro-optical characteristic of a liquid crystal composition may be changed. Moreover, in the method of making it melt | dissolve in an organic solvent, the specific resistance and voltage retention (VHR) of a liquid crystal composition may fall remarkably by the impurity and dopant of an organic solvent. In addition, the organic solvent remains without being completely removed, and at the same time, it causes the specific resistance of the liquid crystal composition to be lowered or the voltage retention is significantly lowered. On the other hand, the manufacturing method by heating to comparatively low temperature in a pressure reduction state is also proposed, and it is disclosed about manufacture of the liquid crystal composition which has a low resistance value (refer patent document 2). However, the method described in the cited document can be manufactured at a relatively low temperature, but heating is required, and thus adverse effects due to heating cannot be completely excluded, and a facility accompanying heating is also required.

In addition, the method described in the cited document has a problem that a large-scale device with a reduced pressure is required. That is, in order to melt | dissolve a liquid crystal compound, while reducing pressure, the container which endures pressure reduction is needed, and a manufacturing apparatus becomes a large-scale thing necessarily to endure pressure reduction. Moreover, although pressure reduction generally uses a vacuum pump, it is necessary as a facility which also attaches the trap for preventing the backflow of the oil mist used for a vacuum pump, and the cooling apparatus for cooling a trap. As described above, manufacturing the liquid crystal composition under reduced pressure causes an increase in equipment, and excessive investment is inevitable in order to respond to the increasing demand for the liquid crystal composition.

As mentioned above, development of the method of manufacturing a high quality liquid crystal composition with a simpler facility efficiently was desired.

Patent Document 1: Japanese Patent Application Laid-Open No. 5-105876 (Uran, page 5)

Patent Document 2: Japanese Patent Application Laid-Open No. 2002-194356 (Example 4 pages)

[Initiation of invention]

[Problem to Solve Invention]

The problem to be solved by the present invention is to provide a method of producing a liquid crystal composition obtained by mixing two or more liquid crystal compounds, which is highly reliable and can be efficiently manufactured.

[Means for solving the problem]

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining about the said subject, the present inventors completed the present invention. This invention provides the manufacturing method of the liquid crystal composition characterized by irradiating a microwave to 2 or more types of liquid crystal compounds in which at least 1 type of melting | fusing point is larger than 30 degreeC.

[Effects of the Invention]

The manufacturing method of this invention does not require large-scale installations, such as a pressure reduction device and a heating device, and can manufacture highly reliable liquid crystal composition of high quality. That is, it is very practical for the manufacture of the liquid crystal composition which suppresses the fall of specific resistance, produces | generates the impurity, and requires high reliability with little change of a physical property value.

BEST MODE FOR CARRYING OUT THE INVENTION [

An example of the present invention will be described below.

The production method of the present invention efficiently produces a liquid crystal composition by irradiating microwaves to a liquid crystal compound containing two or more liquid crystal compounds having at least one melting point greater than 30 ° C. without using a solvent such as an organic solvent. will be. In particular, it is effective for manufacture of the liquid crystal composition using 2 or more types of liquid crystal compounds with two types of melting | fusing points larger than 30 degreeC, and is more effective for manufacture of the liquid crystal composition using two or more types of liquid crystal compounds with 5 or more types of melting points larger than 30 degreeC. .

60% or more is preferable, as for the content rate of a compound whose melting | fusing point is 30 degreeC or more, 70% or more is more preferable, 80% or more is especially preferable.

The liquid crystal composition may contain additives other than liquid crystal compounds. As an additive, antioxidant, a ultraviolet absorber, an antistatic agent, surfactant, etc. can be used. Moreover, you may contain the liquid crystalline or non-liquid crystalline optically active compound. Since the compound which does not have a liquid crystal frame | skeleton has a bad influence on the characteristic of a liquid crystal, if the addition amount is too large, when adding a compound which does not have a liquid crystal frame | skeleton, the content rate of 5% or less in total is preferable, 3% or less is more preferable, 1 % Or less is particularly preferable.

It is preferable that it is 1 hour or less, and, as for the irradiation time of a microwave, it is more preferable that it is 30 minutes or less. If the temperature at the time of microwave irradiation is too high, the quality of the composition to be produced is deteriorated, and if too low, the production takes time, so there is an optimum temperature. Therefore, it is preferable that it is the range of the liquid-crystal upper limit temperature +50 degreeC of the liquid crystal composition manufactured from 40 degreeC, and it is more preferable that it is the range of +30 degreeC.

300 MHz or more and 3 THz or less are preferable, and, as for the frequency of the microwave used, 500 MHz or more is more preferable. 100 W or more is preferable and 1 kW or more of irradiation intensity is more preferable.

Since the manufacturing method of this invention can manufacture a liquid crystal composition at low temperature, it is possible to manufacture a high quality liquid crystal composition also under normal atmospheric atmosphere. However, in order to manufacture a higher quality liquid crystal composition, it is preferable to perform microwave irradiation under sealed conditions, and it is more preferable to carry out in inert gas atmosphere. As an inert gas, rare gases, such as helium, neon, argon, nitrogen gas, etc. can be used suitably.

Although the manufacturing method of this invention does not need to use a pressure reduction means, it is possible to apply the composition to manufacture also in a reduced pressure state.

Although there is no restriction | limiting in particular in the liquid crystal composition manufactured by the manufacturing method of this invention, When manufacturing under reduced pressure, manufacture of the liquid crystal composition containing a large amount of volatilized comparatively small molecular weight compounds is especially preferable.

As a molecular weight of a liquid crystal compound, it is preferable to contain a compound of 300 or less, and it is more preferable to contain a compound of 250 or less.

In order to manufacture a liquid crystal composition more efficiently, it is preferable that the polarization of the liquid crystal molecule comprised is biased. Specifically, more efficient manufacture becomes possible when it has a specific structure or a functional group in the liquid crystal compound comprised. As a preferable structure, what has at least 1 aromatic ring in the molecule | numerator of a liquid crystal compound is preferable. Moreover, as a preferable functional group, electron withdrawing functional groups, such as a halogen and a cyano group, are preferable, the compound which has these functional groups in a molecule is preferable, and the compound which has the said electron withdrawing functional group in an aromatic ring is more preferable.

As a compound comprised, the compound specifically, represented by General formula (I) is preferable.

(In formula, R <^1> and R <^2> is a C1-C16 alkyl group, C1-C16 alkoxy group, C2-C16 alkenyl group, and carbon atom which may each independently be fluorine-substituted. An alkenyloxy group, a fluorine atom, a chlorine atom or a cyano group is selected. A, B and C each independently represent a 1,4-phenylene group, a 2 or 3-fluoro-1,4-phenylene group. , 2,3-difluoro-1,4-phenylene group, 3,5-difluoro-1,4-phenylene group, 2 or 3-chloro-1,4-phenylene group, 2,3-dichloro- 1,4-phenylene group, 3,5-dichloro-1,4-phenylene group, 2-methyl-1,4-phenylene group, 3-methyl-1,4-phenylene group, naphthalene-2,6-diyl group , Phenanthrene-2,7-diyl group, fluorene-2,7-diyl group, trans-1,4-cyclohexylene group, 1,2,3,4-tetrahydronaphthalene-2,6-diyl group , Decahydronaphthalene-2,6-diyl group, trans-1,3-dioxane-2,5-diyl group, pyridine-2,5-diyl group, pyrimidine-2,5-diyl group, pyrazine-2 5-diyl or Li Minced represents a 2,5-diyl group, these groups may also be substituted by fluorine atoms of 1~3, m denotes 0, 1 or 2, Z ¹ and Z ² is a single bond, each independently, -CH ₂ CH ₂ -,-(CH ₂ ) _4- , -OCH _2- , -CH ₂ O-, -COO-, -CH = CH-, -CF = CF-, -CH = NN = CH- or -C≡C-, provided that when m is 2, two Z ² and C may be the same independently or different)

In general formula (I), it is preferable that at least 1 of A, B, and C is an aromatic ring, and it is a 1, 4- phenylene group, 2 or 3-fluoro- 1, 4- phenylene group, 2, 3- difluoro Rho-1,4-phenylene group, 3,5-difluoro-1,4-phenylene group, 2 or 3-chloro-1,4-phenylene group, 2,3-dichloro-1,4-phenylene group, 3,5-dichloro-1,4-phenylene group, 2-methyl-1,4-phenylene group, 3-methyl-1,4-phenylene group, naphthalene-2,6-diyl group, phenanthrene-2,7 -Diyl group, fluorene-2,7-diyl group, 1,2,3,4-tetrahydronaphthalene-2,6-diyl group, pyridine-2,5-diyl group, pyrimidine-2,5- Diyl group, pyrazine-2,5-diyl group or pyridazine-2,5-diyl group are more preferable, A 1, 4- phenylene group, 2 or 3-fluoro- 1, 4- phenylene group, 2, 3 -Difluoro-1,4-phenylene group and 3,5-difluoro-1,4-phenylene group are particularly preferable.

R ¹ and R ² each represent a fluorine atom, a chlorine atom or a cyano group, and the other represents an alkyl group having 1 to 16 carbon atoms, an alkoxy group having 1 to 16 carbon atoms, and an alke having 2 to 16 carbon atoms. Preference is given to compounds which show a nil group and an alkenyloxy group having 3 to 16 carbon atoms.

When manufacturing the liquid crystal composition for TFT by the manufacturing method of this invention, in the compound represented by general formula (I), R <^1> and R <^2> are respectively independently a fluorine atom, a C1-C16 alkyl group, or carbon Preference is given to compounds which represent alkenyl groups having 2 to 16 atoms. In this case, the obtained liquid crystal composition has a high voltage retention.

Hereinafter, although an Example is given and this invention is further explained, this invention is not limited to these Examples. In addition, "%" in the composition of the following example and a comparative example means "mass%."

Microwave irradiation was performed using a microwave irradiation device (special order product) made by Fuji Denpago Co., Ltd. (high frequency output: 6 kW, oscillation frequency: 2450 MHz ± 50 MHz). The following apparatus was used for the analysis of the produced liquid crystal composition.

Gas chromatography: HP6890 from HEWLETT-PACKARD

Reliability was confirmed by measuring the specific resistance of the liquid crystal composition, confirming the generation of impurities by gas chromatography and decomposition of the compound to be blended, measurement of voltage retention, current value, and physical property value.

Example 1 Preparation of Liquid Crystal Composition

The liquid crystal composition (STN1, liquid crystal upper limit temperature 95.1 degreeC) comprised with the following compounds was manufactured.

The amount of each compound described above was measured in a 150 ml separable flask. This separable flask was set in a microwave generator, and the microwaves were irradiated and heated at an output of 1 kW. After 10 minutes of irradiation, microwave irradiation was stopped, the separable flask was cooled and taken out from the microwave irradiation device to obtain 100 g of STN1 in the nematic liquid crystal state.

When the specific resistance of the produced liquid crystal composition was measured, it was 1.1 x 10 ¹¹ Ωcm. Moreover, when the produced liquid crystal composition was analyzed by gas chromatography, the substance other than the compound which mix | blended was not mixed and produced, and the decomposition | disassembly of the compound which mix | blended was not seen, either. When the physical property of the produced liquid crystal composition was measured, the desired characteristic was obtained. The liquid crystal was injected into the STN panel, and the electro-optical characteristics were measured to obtain desired characteristics. As mentioned above, it is clear that the liquid crystal composition of Example 1 has very high reliability.

The manufacturing method of this invention was able to manufacture the high quality liquid crystal composition in 40 minutes, without requiring large scale equipment.

(Comparative Example 1) Preparation of liquid crystal composition under reduced pressure

In the same manner as in Example 1, a liquid crystal composition (STN1) was produced according to the method described in JP-A-2002-194356.

A predetermined liquid crystal compound was weighed into a branched flask. This branched flask was attached to a rotary evaporator. The branched flask was immersed in an oil bath at 50 ° C. and spun. The rotary evaporator was slowly depressurized to 20 kPa over 5 minutes by a vacuum pump. The temperature of the oil bath was set to 110 ° C, and the temperature was raised to 5 ° C / min. 30 minutes after the liquid crystal changed to a liquid state and became transparent, the oil bath was changed to a water bath and cooled. After falling to room temperature, the rotation was stopped and the pressure was stopped. After returning to atmospheric pressure by substituting the inside of a flask with nitrogen gas, the branched flask was removed from the rotary evaporator and 100g of STN1 of the nematic liquid crystal state was obtained.

When the specific resistance of the produced liquid crystal composition was measured, it was 1.2 x 10 ¹¹ Ωcm. When the produced liquid crystal composition was analyzed by gas chromatography, the substance other than the compound which mix | blended was not mixed and produced, and the decomposition | disassembly of the compound which mix | blended was not seen, either. When the physical property of the produced liquid crystal composition was measured, the desired characteristic was obtained. However, some volatilization of the compound with a relatively low molecular weight was confirmed, and the composition changed. In addition, it is necessary to use a pressure reduction device or a heating device that requires a large-scale facility for production, and a long production time is required.

Comparative Example 2 Preparation of Liquid Crystal Composition in Air

In the same manner as in Example 1, a liquid crystal composition (STN1) was produced according to the method described in JP-A-5-105876.

A predetermined liquid crystal compound was weighed into a branched flask. A magnetic rotor was placed in this branched flask, placed on a 50 ° C hotplate, and stirred by rotating the rotor while raising the temperature of the hotplate to 110 ° C at 5 ° C / min. After 30 minutes after the liquid crystal had changed to a liquid state and became transparent, the heating of the hot plate was stopped and gradually returned to room temperature. 100g of STN1 of the nematic liquid crystal state was obtained.

When the specific resistance of the produced liquid crystal composition was measured, it was 1.1 x 10 ⁹ Ωcm. When the produced liquid crystal composition was analyzed by gas chromatography, many substances other than the compound compound appeared, and it turned out that the liquid crystal compound which comprises a liquid crystal composition oxidatively decomposes. When the temperature before a liquid crystal upper limit was measured, it fell to 94.0 degreeC and the quality deterioration was large. In the manufacturing method of the comparative example 2, it is clear that it is inferior to an Example from the point of reliability of the produced liquid crystal composition.

Example 2 Preparation of Liquid Crystal Composition

The liquid crystal composition (TFT1, liquid crystal upper limit temperature 68.0 degreeC) comprised with the following compounds was manufactured.

The amount of each compound described above was measured in a 150 ml separable flask. This separable flask was set in a microwave generator, and the microwaves were irradiated and heated at an output of 1 kW. After 10 minutes of irradiation, microwave irradiation was stopped, the separable flask was cooled, taken out from the microwave irradiation device, and 100 g of TFT1 in a nematic liquid crystal state was obtained.

When the specific resistance of the produced liquid crystal composition was measured, it was 1.5 x 10 ¹⁴ Ωcm. Moreover, when the produced liquid crystal composition was analyzed by gas chromatography, the substance other than the compound which mix | blended was not mixed and produced, and the decomposition | disassembly of the compound which mix | blended was not seen, either. When the physical property of the produced liquid crystal composition was measured, the desired characteristic was obtained. The desired characteristic was obtained when this liquid crystal was injected into TFT panel, and the electro-optical characteristic was measured. Moreover, the voltage retention in the case of using for a TFT panel was also high enough.

The manufacturing method of this invention was able to manufacture the high quality liquid crystal composition in 40 minutes, without requiring large scale equipment. As mentioned above, it is clear that the liquid crystal composition of Example 2 has very high reliability.

Comparative Example 3 Preparation of Liquid Crystal Composition Under reduced pressure

In the same manner as in Example 2, a liquid crystal composition (TFT1) was produced according to the method described in JP-A-2002-194356.

A predetermined liquid crystal compound was weighed into a branched flask. This branched flask was attached to a rotary evaporator. The branched flask was immersed in an oil bath at 50 ° C. and spun. The rotary evaporator was slowly depressurized to 20 kPa over 5 minutes by a vacuum pump. The temperature of the oil bath was set to 85 degreeC, and it heated up at 5 degree-C / min. 30 minutes after the liquid crystal changed to a liquid state and became transparent, the oil bath was changed to a water bath and cooled. After falling to room temperature, the rotation was stopped and the pressure was stopped. After returning to atmospheric pressure by substituting the inside of a flask with nitrogen gas, the branched flask was removed from the rotary evaporator and 100g of TFT1 of a nematic liquid crystal state was obtained.

When the specific resistance of the produced liquid crystal composition was measured, it was 1.2 x 10 ¹⁴ Ωcm. When the produced liquid crystal composition was analyzed by gas chromatography, the substance other than the compound which mix | blended was not mixed and produced, and the decomposition | disassembly of the compound which mix | blended was not seen, either. When the physical property of the produced liquid crystal composition was measured, the desired characteristic was obtained. However, some volatilization of the compound with a relatively low molecular weight was confirmed, and the composition changed. In addition, it is necessary to use a pressure reduction device or a heating device that requires a large-scale facility for production, and a long production time is required.

Comparative Example 4 Preparation of Liquid Crystal Composition in Air

In the same manner as in Example 2, a liquid crystal composition (TFT1) was produced according to the method described in JP-A-5-105876.

A predetermined liquid crystal compound was weighed into a branched flask. A magnetic rotor was placed in this branched flask, placed on a 50 ° C hotplate, and stirred by rotating the rotor while raising the temperature of the hotplate to 85 ° C at 5 ° C / min. After 30 minutes after the liquid crystal had changed to a liquid state and became transparent, the heating of the hot plate was stopped and gradually returned to room temperature. 100g of TFT1 of the nematic liquid crystal state was obtained.

When the specific resistance of the produced liquid crystal composition was measured, it was 1.3 × 10 ¹³ Ωcm. When the produced liquid crystal composition was analyzed by gas chromatography, many substances other than the compound compound appeared, and it turned out that the liquid crystal compound which comprises a liquid crystal composition oxidatively decomposes. When the temperature before a liquid crystal upper limit was measured, it fell to 66.8 degreeC and the quality deterioration was large. In the manufacturing method of the comparative example 4, it is clear that it is inferior to an Example by the point of reliability of the produced liquid crystal composition.

The manufacturing method of this invention suppresses the fall of specific resistance, is very practical for manufacture of the liquid crystal composition in which high reliability with little generation | occurrence | production of an impurity and few fluctuation | variation of a physical property value is calculated | required.

Claims (7)

Microwave is irradiated to 2 or more types of liquid crystal compounds with at least 1 type of melting | fusing point larger than 30 degreeC, The manufacturing method of the liquid crystal composition characterized by the above-mentioned. The method of claim 1, The manufacturing method in which at least 2 sorts of melting | fusing points are larger than 30 degreeC in a liquid crystal compound. The method of claim 1, The manufacturing method whose irradiation time of a microwave is 1 hour or less. The method of claim 1, The manufacturing method which irradiates a microwave under reduced pressure. The method of claim 1, The manufacturing method which irradiates a microwave in inert gas atmosphere. The method of claim 1, The manufacturing method in which the temperature at the time of microwave irradiation is the range of the liquid-crystal upper limit temperature +50 degreeC of the liquid crystal composition manufactured from 40 degreeC. The method of claim 4, wherein The manufacturing method which uses an inert gas when returning a reduced pressure state to atmospheric pressure.