JP2003277752A - Method for purifying liquid crystal compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for purification by a simple operation which improves reliability (such as resistivity and the like) of a crystal compound and reliability in a panel, to prepare a liquid crystal composition exhibiting high reliability (such as resistivity and the like) and reliability in a panel by using the obtained compound as a constituent component, and to manufacture using the same a highly reliable liquid crystal display element by a simple matrix driving system, an active matrix driving system or the like. <P>SOLUTION: The method for purifying the liquid crystal compound comprises dissolving the crystal compound in an organic solvent, treating it with 1,8- diazabicyclo[5.4.0]-7-undecene and/or 1,5-diazabicyclo[4.3.0]-5-nonene and subsequently removing DBU and DBN. The crystal composition is obtained by using the obtained liquid crystal compound. Thus, improvement in reliability of the liquid crystal compound (such as resistivity and the like) and reliability in a panel, which is hardly accomplished by a conventional purifying method, is simply and readily attained. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel method for purifying a liquid crystal compound, a liquid crystal compound purified by the purification method, a liquid crystal composition containing the compound, and a liquid crystal display device using the composition.

[0002]

2. Description of the Related Art Liquid crystal display devices have come to be used in watches, calculators, various measuring instruments, automobile panels, word processors, electronic notebooks, printers, computers, televisions and the like. Typical liquid crystal display systems are TN (twisted nematic) type, STN (super twisted nematic) type, DS (dynamic light scattering) type, GH (guest host) type, or FLC capable of high-speed response. (Ferroelectric liquid crystal) and the like. Also, as the drive system, the conventional static drive has become more common, and the multiplex drive is becoming more common, and the simple matrix system and recently the active matrix system have been put into practical use. As liquid crystal materials used for these, a great variety of compounds have been synthesized so far, and they are used as a constituent component of a liquid crystal composition depending on the application.

Physical properties of liquid crystal compositions (nematic phase temperature range, refractive index anisotropy (Δn), dielectric anisotropy (Δε), viscosity,
Elastic constants) and electro-optical characteristics (response time, threshold voltage, V-
The steepness of the T curve, etc.) is required to have various values depending on the intended display system and drive system of the liquid crystal element, and further, high reliability against heat and light is required.

Regarding the reliability of the liquid crystal composition, it is necessary that the individual liquid crystal compounds constituting the composition have high reliability and high reliability in the panel.

The reliability of a liquid crystal compound is often used as an index of reliability by preparing a liquid crystal composition and measuring its specific resistance. In addition, the reliability of the liquid crystal composition in the panel is
In many cases, a liquid crystal composition is prepared, sealed in a panel, and the current value thereof is measured to be used as an index of reliability.

However, the specific resistance of the liquid crystal composition cannot be increased due to the presence of trace impurities that are difficult to remove.
In many cases, it has been difficult to raise the current value in the panel, and purification methods have been studied. Conventionally, in order to remove such impurities, it has been necessary to purify by combining operations such as recrystallization, column chromatography, adsorbent treatment, ion exchange treatment, or distillation, if necessary, to produce a liquid crystal compound. In the above, productivity was remarkably reduced.
In addition, the specific resistance of the liquid crystal composition is low, the current value in the panel is high, and the reliability cannot be sufficiently improved no matter how many times the refining operation is repeated. Therefore, the physical properties and electro-optical characteristics are not improved. There were some compounds that were excellent but could not be put to practical use.

[0007]

The problem to be solved by the present invention is to provide a purification method for improving the reliability of a liquid crystal compound and the reliability in a panel by a simple operation. It is an object of the present invention to provide a liquid crystal composition having excellent reliability in a panel, which uses the compound obtained by the above as a constituent, and further to provide a highly reliable liquid crystal display device using the liquid crystal composition.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that 1,8-diazabicyclo [5.4.0] -7-undecene was obtained by dissolving a liquid crystal compound in an organic solvent.
(Hereinafter sometimes referred to as DBU) and / or 1,5-diazabicyclo [4.3.0] -5-nonene (hereinafter sometimes referred to as DBN), and then DBU and DBN are removed. The inventors have found a method for purifying a liquid crystal compound characterized by the above.

Further, by using the obtained compound as a constituent, a liquid crystal composition having high reliability (specific resistance etc.) and reliability in a panel can be prepared,
It has become possible to manufacture a highly reliable liquid crystal display device such as a simple matrix drive system and an active matrix drive system using this, and the present invention has been completed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As a treatment method with DBU and / or DBN, it is preferable to dissolve a liquid crystal compound in an organic solvent and add DBU and / or DBN.
It is preferable to add a stirring step before removing BU and DBN, and the stirring time is preferably 10 minutes or more and 24 hours or less.
Minutes to 12 hours are more preferable, and 30 minutes to 6 hours are particularly preferable.

The temperature condition when DBU and / or DBN is added and stirred is preferably 0 ° C to 30 ° C, particularly preferably 15 ° C to 25 ° C.

The addition ratio of DBU and / or DBN used in the present invention is preferably 0.001% by mass to 20% by mass, more preferably 0.01% by mass to 18% by mass, and further preferably 0.1% by mass to 15% with respect to the liquid crystal compound to be purified. Mass% is more preferable, and 1 mass% to 10 mass% is particularly preferable.

The organic solvent is preferably a hydrocarbon solvent, and the aliphatic hydrocarbon solvent may be linear, branched, or cyclic pentane, hexane, heptane, octane, nonane or decane, and aromatic carbon. As the hydrogen-based solvent, benzene, toluene and xylene are preferable, n-hexane, cyclohexane, n-heptane, toluene and xylene are more preferable, and n-hexane, cyclohexane and toluene are particularly preferable.

The water washing step is a step of washing the water by stirring a two-phase system of a liquid crystal compound dissolved in a solvent and water, and then separating the used water to separate the used water. The steps are similar except that an aqueous solution of acid or base is used instead of water.

The water used in the water washing step is preferably ion-exchanged water, distilled water or ultrapure water, and ion-exchanged water is particularly preferable. The conductivity of ion-exchanged water is preferably 1.0 μS / cm or less, and particularly preferably 0.5 μS / cm or less.

The acid used in the acid washing step is preferably an inorganic acid aqueous solution, more preferably an aqueous hydrochloric acid solution or an aqueous sulfuric acid solution, and its concentration is preferably 3% by volume to 15% by volume, and 6% by volume to 12% by volume. More preferable.

As the base used in the alkali washing step,
Inorganic bases are preferred, and when sodium bicarbonate water is used, its concentration is
1% to 8.1% by weight is preferred, and 8.1% by weight is particularly preferred.

In the purification step after the water washing step and the acid and alkali washing step, it is preferable to carry out one or more kinds selected from recrystallization, column chromatography and adsorbent treatment, and it is preferable to perform adsorbent treatment. It is more preferable to carry out recrystallization after treatment with the adsorbent.

The liquid crystal compound which is the object of the purification method of the present invention is represented by the general formula (I)

[Chemical 2] (In the formula, R is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms,
Alkoxyl group, alkoxyl alkyl group, alkenyl
Represents a group or alkenyloxy group, which has 1 carbon atom
Substituted with an alkoxyl group or an alkenyloxy group of
Any one or more hydrogen atoms in the chain
It may be substituted with a nitrogen atom. A, B, C and D are
Independently trans-1,4-cyclohexylene groups, 1 or more
1,4-phenylene optionally substituted with the above fluorine atoms
Group, naphth optionally substituted with one or more fluorine atoms
Talen-2,6-diyl group, substituted with one or more fluorine atoms
An optionally tetrahydronaphthalene-2,6-diyl group,
Decahydronaphthalene-2,6-diyl group, one or more fluorine
Phenanthrene-3,8-di, optionally substituted with atoms
Group, a group which may be substituted with one or more fluorine atoms.
Trahydrophenanthrene-3,8-diyl group, 1 or more
Octahydrophenane optionally substituted with a fluorine atom
Tren-3,8-diyl group, perhydrophenanthrene-3,8-
Diyl group, pyridine-2,5-diyl group, pyrimidine-2,5-di
Yl group, pyrazine-2,5-diyl group, pyridazine-3,6-diyl group
Group or trans-1,3-dioxane-2,5-diyl group
Then L¹~ L^FourAre independently -COO-, -OCO-, -CH₂CH
₂-, -CH₂CH (CH₃)-,-CH (CH₃) CH₂-, -CH₂O-, -OCH₂-, -C
F₂O-, -OCF₂-, -CH₂CH₂CH₂CH₂-, -CH = CHCH₂CH₂-, -CH₂C
H = CHCH ₂-, -CH₂CH₂CH = CH-, -OCH₂CH₂CH₂-, -CH₂OCH₂CH₂
-, -CH₂CH₂OCH₂-, -CH₂CH₂CH₂O-, -CF₂OCH₂CH₂-, -CH₂C
H₂OCF₂-, -CF = CF-, -CH = CH-, -C≡C- or single bond
You a, b, c and d each independently represent 0 or 1,
At least one represents 1. Z is a cyano group, a fluorine atom,
Chlorine atom, trifluoromethyl group, trifluoromethoxy
Si group, difluoromethoxy group, fluorine having 2 to 3 carbon atoms
Substituted alkoxyl group, straight-chain alkenyl group having 2 to 7 carbon atoms
It represents a alkyl group or an alkenyl group. Compound represented by)
It is suitable for purification.

In the general formula (I), a compound in which R represents a linear alkyl group having 1 to 7 carbon atoms or a linear alkenyl group having 2 to 7 carbon atoms is preferable, and Z is a cyano group or a fluorine atom. Represents a chlorine atom, a trifluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group or a fluorine-substituted alkoxyl group having 2 to 3 carbon atoms, and exists L ¹ to
It is more preferable to purify a compound in which L ⁴ represents —COO—, —OCO—, —CF ₂ O—, —OCF ₂ — or —C≡C—. These compounds have a strong anisotropy of P
Since it is a type liquid crystal material, and impurities such as ionic substances are easily taken in, sufficient reliability cannot be obtained by conventional purification methods.

In the present purification method, the liquid crystal compound may be purified alone or as a liquid crystal composition in which two or more kinds of liquid crystal compounds are mixed.

[0022]

The present invention will be further described below by showing Examples of the present invention. However, the present invention is not limited to these examples.

(Evaluation of reliability of compound) Base liquid crystal composition (H)

[Chemical 3]

A liquid crystal composition was prepared by adding 10% by mass of the liquid crystal compound purified by the method of the present invention to (in the formula,% represents mass%) and heating and dissolving. UV (Suntest) irradiation 30
Minute sample (hereinafter UV) and untreated sample (hereinafter initial) were prepared, and the specific resistance (Ω
-Cm) was measured and used as an index of the reliability of the liquid crystal compound. The specific resistance (Ω · cm) was measured with an electrometer MMAII-17A manufactured by Kawaguchi Electric Co., Ltd. by applying 1VDC using a liquid electrode LP-05 type having a cell gap of 1 mm.

(Reliability Evaluation in Panel) The liquid crystal composition prepared for measuring the specific resistance was used as a liquid crystal cell for TN (cell gap 8.3
(UV-curable resin (3Bond, T
A liquid crystal cell was prepared by sealing with hree Bond 3026).

A sample whose current value was measured immediately after the liquid crystal cell was prepared was used as an initial sample (hereinafter abbreviated as initial). Using Suntest (Original Hanau) for liquid crystal cells
UV irradiation sample (UV
(Abbreviated as V). Use a liquid crystal cell in an oven at 80 ℃ for 350
A sample that has been heated for a period of time is a heated sample
And

The current value is measured by applying a rectangular wave (Vap = 2.5V) to the liquid crystal cell produced using the circuit shown in FIG. 1 and observing the voltage waveform applied across the 50KΩ resistor in the circuit. Went by. From the observed voltage waveform (Fig. 2), Vr (mV)
And the electrode area of the liquid crystal cell: W (cm ² )

[Equation 1] The current value was calculated by. At this time, three liquid crystal cells were produced under each condition, the current value was measured, and the current value obtained by averaging the current values obtained from the three cells was used as an index of reliability in the panel. did.

(Example) 1,8-diazabicyclo [5.4.0] -7-
Resistivity and current value when 10 mass% of undecene was added

[Chemical 4] 7 g of the compound (II) was dissolved in 35 mL of toluene, 10% by mass of 1,8-diazabicyclo [5.4.0] -7-undecene was added to the compound (II), and the mixture was stirred at 25 ° C. for 30 minutes. Deionized water 35mL
(0.35 μS / cm), the organic layer was washed once, and then the organic layer was washed twice with 35 mL of a 9 vol% hydrochloric acid aqueous solution. After washing the organic layer twice with 35 mL of deionized water (conductivity 0.35 μS / cm), after washing the organic layer twice with 35 mL of saturated sodium hydrogen carbonate solution, with 35 mL of deionized water (conductivity 0.35 μS / cm), the organic The layers were washed 4 times. Silica gel 0.35g / Alumina 0.35g as adsorbent
Was added and stirred for 30 minutes. After the adsorbent was filtered off with a 1 μm Millipore filter, the solvent was distilled off under reduced pressure. The crystals were recrystallized from methanol, and the precipitated crystals were filtered and dried to obtain 6.6 g of purified compound (II). The measurement results of the specific resistance and current value of the liquid crystal composition for evaluation using the obtained compound (II) are as follows.

[0029]

[Table 1]

Comparative Example 5 g of compound (II) was dissolved in 25 mL of toluene, and the organic layer was washed twice with 25 mL (0.35 μS / cm) of ion-exchanged water, and then 0.25 g of silica gel / alumina as an adsorbent.
0.25g was added and stirred for 30 minutes. After the adsorbent was filtered off with a 1 μm Millipore filter, the solvent was distilled off under reduced pressure. The crystals were recrystallized from methanol, and the crystallized crystals were filtered and dried to obtain 4.6 g of purified compound (II). The measurement results of the specific resistance and current value of the liquid crystal composition for evaluation using the obtained compound (II) are as follows.

[Table 2]

The results of the compound obtained in the example according to the purification method of the present invention and the compound of the comparative example obtained by purification by a known method are compared. In the example, the specific resistance is improved three times or more in the initial stage and twice in UV as compared with the comparative example. The current value is
It can be seen that UV is reduced by about 12% and heating is reduced by about 5%.
Therefore, the purification method of the present invention is effective in improving the reliability of the liquid crystal compound and the reliability in the panel.

[0032]

According to the method for purifying a liquid crystal compound of the present invention,
Reliability of liquid crystal compounds, which was difficult with conventional purification methods
(Specific resistance etc.) and reliability in the panel can be improved easily and easily. A liquid crystal composition containing a liquid crystal compound purified by the method of the present invention has high reliability and is useful as a constituent material of a TN type, STN type, or TFT type liquid crystal display device.

[0033]

[Brief description of drawings]

[Figure 1] Current value measurement circuit

[Fig.2] Observation waveform in current measurement circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09K 19/20 C09K 19/20 19/30 19/30 19/32 19/32 G02F 1/13 500 G02F 1 / 13 500

Claims (15)

[Claims] 1. A liquid crystal compound is dissolved in an organic solvent and treated with 1,8-diazabicyclo [5.4.0] -7-undecene and / or 1,5-diazabicyclo [4.3.0] -5-nonene, 1,8-
A method for purifying a liquid crystal compound, which comprises removing diazabicyclo [5.4.0] -7-undecene and 1,5-diazabicyclo [4.3.0] -5-nonene. 2. The step of removing 1,8-diazabicyclo [5.4.0] -7-undecene and 1,5-diazabicyclo [4.3.0] -5-nonene comprises 1. Water washing step, 2. Acid washing step and water washing step,
3. 2. The purification method according to claim 1, which is one of an acid washing step, an alkali washing step and a water washing step. 3. The purification method according to claim 1, wherein a hydrocarbon solvent is used as the organic solvent. 4. The addition ratio of 1,8-diazabicyclo [5.4.0] -7-undecene and / or 1,5-diazabicyclo [4.3.0] -5-nonene is from 0.001% by mass to 20% based on the liquid crystal compound. The purification method according to claim 1, which is% by mass. 5. The treatment step with 1,8-diazabicyclo [5.4.0] -7-undecene and / or 1,5-diazabicyclo [4.3.0] -5-nonene is 1,8-diazabicyclo [5.4.0]. ] -7-Undecene and / or 1,5-diazabicyclo [4.3.0] -5-nonene are added and stirred for 10 minutes or more and within 24 hours to obtain 1,8-diazabicyclo [5.4.0] -7-undecene and / Or the temperature of 1,5-diazabicyclo [4.3.0] -5-nonene added and stirred
The purification method according to claim 1, which is 0 ° C to 30 ° C. 6. The step of removing 1,8-diazabicyclo [5.4.0] -7-undecene and 1,5-diazabicyclo [4.3.0] -5-nonene comprises 1. Water washing step, 2. Acid washing step and water washing step,
3. 2. The refining method according to claim 1, which is one of an acid washing step, an alkali washing step, and a water washing step, wherein a hydrocarbon solvent is used as the organic solvent. 7. The addition rate of 1,8-diazabicyclo [5.4.0] -7-undecene and / or 1,5-diazabicyclo [4.3.0] -5-nonene is from 0.001% by mass to 20% with respect to the liquid crystal compound. %, 1,8-diazabicyclo [5.4.0] -7-undecene and / or
Alternatively, as a treatment step with 1,5-diazabicyclo [4.3.0] -5-nonene, 1,8-diazabicyclo [5.4.0] -7-undecene and / or 1,5-diazabicyclo [4.3.0] -5- Add nonene and stir for 10 minutes to 24 hours, and then add 1,8-diazabicyclo [5.4.0] -7-undecene and / or 1,5-diazabicyclo [4.3.0] -5-nonene and stir Temperature of 0 ℃ to 3
The purification method according to claim 1, which is 0 ° C. 8. The step of removing 1,8-diazabicyclo [5.4.0] -7-undecene and 1,5-diazabicyclo [4.3.0] -5-nonene comprises 1. Water washing step, 2. Acid washing step and water washing step,
3. Any one of the acid cleaning step, the alkali cleaning step and the water cleaning step, using a hydrocarbon solvent as the organic solvent,
8-diazabicyclo [5.4.0] -7-undecene and / or 1,
The addition ratio of 5-diazabicyclo [4.3.0] -5-nonene is 0.001 to 20 mass% with respect to the liquid crystal compound, and 1,8-diazabicyclo [5.4.0] -7-undecene and / or 1, As a treatment step with 5-diazabicyclo [4.3.0] -5-nonene, 1,8-
Diazabicyclo [5.4.0] -7-undecene and / or 1,5-
Add diazabicyclo [4.3.0] -5-nonene and stir for 10 minutes or more and within 24 hours to give 1,8-diazabicyclo [5.4.0] -7-undecene and / or 1,5-diazabicyclo [4.3.0]. The temperature during addition of -5-nonene and stirring is 0 to 30 ° C.
The described purification method. 9. The conductivity in the water washing step is 1.0 μS / c.
9. The purification method according to claim 2, wherein the ion-exchanged water of m or less is used. 10. The purification method according to claim 1, wherein one or more purification steps selected from recrystallization, column chromatography and adsorbent treatment are performed. 11. A liquid crystal compound represented by the general formula (I) [Chemical 1] (In the formula, R is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms,
Alkoxyl group, alkoxyl alkyl group, alkenyl
Represents a group or alkenyloxy group, which has 1 carbon atom
Substituted with an alkoxyl group or an alkenyloxy group of
Any one or more hydrogen atoms in the chain
It may be substituted with a nitrogen atom. A, B, C and D are
Independently trans-1,4-cyclohexylene groups, 1 or more
1,4-phenylene optionally substituted with the above fluorine atoms
Group, naphth optionally substituted with one or more fluorine atoms
Talen-2,6-diyl group, substituted with one or more fluorine atoms
An optionally tetrahydronaphthalene-2,6-diyl group,
Decahydronaphthalene-2,6-diyl group, one or more fluorine
Phenanthrene-3,8-di, optionally substituted with atoms
Group, a group which may be substituted with one or more fluorine atoms.
Trahydrophenanthrene-3,8-diyl group, 1 or more
Octahydrophenane optionally substituted with a fluorine atom
Tren-3,8-diyl group, perhydrophenanthrene-3,8-
Diyl group, pyridine-2,5-diyl group, pyrimidine-2,5-di
Yl group, pyrazine-2,5-diyl group, pyridazine-3,6-diyl group
Group or trans-1,3-dioxane-2,5-diyl group
Then L¹~ L^FourAre independently -COO-, -OCO-, -CH₂CH
₂-, -CH₂CH (CH₃)-,-CH (CH₃) CH₂-, -CH₂O-, -OCH₂-, -C
F₂O-, -OCF₂-, -CH₂CH₂CH₂CH₂-, -CH = CHCH₂CH₂-, -CH₂C
H = CHCH ₂-, -CH₂CH₂CH = CH-, -OCH₂CH₂CH₂-, -CH₂OCH₂CH₂
-, -CH₂CH₂OCH₂-, -CH₂CH₂CH₂O-, -CF₂OCH₂CH₂-, -CH₂C
H₂OCF₂-, -CF = CF-, -CH = CH-, -C≡C- or single bond
You a, b, c and d each independently represent 0 or 1,
At least one represents 1. Z is a cyano group, a fluorine atom,
Chlorine atom, trifluoromethyl group, trifluoromethoxy
Si group, difluoromethoxy group, fluorine having 2 to 3 carbon atoms
Substituted alkoxyl group, straight-chain alkenyl group having 2 to 7 carbon atoms
It represents a alkyl group or an alkenyl group. ) Claim 1 represented by
11. The purification method according to any one of to 10. 12. In the general formula (I), Z is a cyano group, a fluorine atom, a chlorine atom, a trifluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group or the number of carbon atoms.
A fluorine-substituted alkoxyl group of 2 to 3, wherein L ^{1 to} L ⁴ present represent -COO-, -OCO-, -CF ₂ O-, -OCF _2-, or -C≡C-. The described purification method. 13. A liquid crystal compound purified by the method according to claim 1. 14. A liquid crystal composition containing the liquid crystal compound according to claim 13. 15. A liquid crystal display device comprising the liquid crystal composition according to claim 14 as a constituent element.