JPH11140446A - Production of azine-based mixed liquid crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply produce the subject mixed liquid crystal having a low melting point and a wide temperature range and useful as a nematic liquid crystal material for an electrooptical liquid crystal display by reacting plural kinds of specific benzaldehydes with hydrazine. SOLUTION: (A) A mixture of two or more benzaldehydes selected from compounds represented by formula I [R<1> is a 1-10C alkyl, a 3-10C alkenyl(oxy), a 1-10C alkoxyl, F, Cl, di- or trifluoromethoxy or cyano] is reacted with (B) hydrazine to provide an azine-based mixed liquid crystal composed of three or more compounds represented by formula II (R<5> and R<6> are each R<1> ). The reaction is preferably carried out in the presence of a dehydrating agent or an acid in a solvent such as halogen-based hydrocarbons at ambient temperature by using the component B in an amount of 0.45-0.55 mol based on 1 mol component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an azine-based mixed liquid crystal as an organic electronic material or a medical or agricultural chemical, particularly a nematic liquid crystal material for electrooptical liquid crystal display.

[0002]

2. Description of the Related Art Liquid crystal display elements have been used in various measuring instruments, such as watches and calculators, automobile panels, word processors, electronic organizers, printers, computers, televisions, and the like. Typical liquid crystal display methods are TN (twisted nematic) type and S type.
TN (super twisted nematic) type, DS (dynamic light scattering) type,
There are GH (guest / host) type or FLC (ferroelectric liquid crystal), etc., and the driving method is generally multiplex driving instead of conventional static driving, and moreover, simple matrix method, recently active matrix method is practical. Has been According to these display methods and driving methods, various characteristics are required as a liquid crystal material, and therefore, a large number of liquid crystal compounds have been synthesized.

[0003] Among such liquid crystal compounds, the general formula (A)

[0004]

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The azine derivative represented by the formula (where ^Ra represents an alkyl group or an alkoxyl group) has been known for a relatively long time, and (i) has a high liquid crystal phase maximum temperature. (ii) High-speed response is possible. (iii) It is easy and inexpensive to manufacture. It is an excellent liquid crystal material having such properties. However, this compound (A) has a problem that its melting point is high and its compatibility with other liquid crystal compounds is poor.

As a compound which has solved this problem, JP-A-54-87688 discloses a compound represented by the general formula (B):

[0007]

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Wherein R ^a and R ^b are different from each other;
Alkyl group, alkoxyl group, fluorine atom, chlorine atom,
Represents a bromine atom or a cyano group. Asymmetric azines represented by) have been reported.

The compound (B) has a lower melting point than the compound (A), and has improved compatibility with other liquid crystal compounds. Further, the upper limit temperature of the liquid crystal phase is about the same as (A). Further, since a polar group such as a cyano group or a halogen atom can be introduced as ^Ra or ^Rb , a so-called P-type liquid crystal compound can be obtained, which is effective even when a low threshold voltage is required. Has excellent properties such as

However, the melting point of the compound (B) and the compatibility with other liquid crystal compounds are never satisfactory, and when the amount added to the liquid crystal composition as a single compound increases, precipitation tends to occur. There was a point. Therefore, when it is desired to add a large amount of an azine compound to the liquid crystal composition, it is necessary to mix various kinds of azine compounds.

The compound (A) is relatively easy to produce because of its symmetrical chemical structure.
It is not always easy to prepare the compound of formula (1).
That is, in the above-mentioned Japanese Patent Application Laid-Open No. 54-87688,
Only the general method for producing the compound (B) is described, and no specific production examples are described. The present inventors have previously selected the asymmetric azines containing the compound of the formula (B). However, even if this method is used, it is troublesome as compared with the production of the compound (A). Therefore, it was not industrially advantageous to prepare a large number of azine compounds in order to prepare a liquid crystal composition containing a large amount of the azine compound. Therefore, a method of obtaining a mixture composed of other azine-based compounds more simply is desired.

[0012]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problem by preparing a plurality of benzaldehydes having a low melting point and a low temperature using the same production method as in the case of symmetric azines. An object of the present invention is to provide a method for easily producing an azine-based liquid crystal mixture having a wide range.

That is, in order to solve the above problems, General formula (Ia)

[0014]

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(Wherein R ¹ represents an alkyl group having 1 to 10 carbon atoms) and a compound represented by the general formula (Ib):

[0016]

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(Wherein R ² represents an alkenyl group having 3 to 10 carbon atoms) and a compound represented by the general formula (Ic):

[0018]

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(Wherein, R ³ represents an alkoxyl group having 1 to 10 carbon atoms or an alkenyloxy group having 3 to 10 carbon atoms) and the general formula (Id)

[0020]

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(Wherein R ⁴ represents a fluorine atom, a chlorine atom, a trifluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group or a cyano group), at least two compounds selected from benzaldehydes represented by the following formulas: Is reacted with hydrazine, and is represented by the general formula (II):

[0022]

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(Wherein R ⁵ and R ⁶ are each independently an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 3 to 10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms, and 3 to 1 carbon atoms)
And an alkenyloxy group of 0 represents a fluorine atom, a chlorine atom, a trifluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group or a cyano group. ) A method for producing an azine-based mixed liquid crystal comprising at least three kinds of compounds represented by the formula: 2. 2. The production method according to the above 1, wherein the benzaldehyde is selected from the general formulas (Ia) and (Ib). 3. 3. The method according to the above 1 or 2, wherein at least three kinds of benzaldehydes are used. 4. The benzaldehyde is a compound represented by the general formula (Ia)
¹ is characterized in that it is selected from compounds wherein R ² is represented by a 3-butenyl group in the compound represented by the linear alkyl group of 1 to 5 carbon atoms and the general formula (Ib), the 2 or 3 The manufacturing method as described. As the above-mentioned solution.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of a method for producing an azine-based mixed liquid crystal of the present invention will be described. The method for producing an azine-based liquid crystal mixture provided by the present invention is as follows.

The present invention is characterized in that a mixture of a plurality of benzaldehydes is reacted with hydrazine in a solvent,
Further, benzaldehydes are represented by the following (Ia) to (Id)
It is characterized by being selected from.

Formula (Ia)

[0027]

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In the formula, R ¹ represents an alkyl group having 1 to 10 carbon atoms, preferably a linear alkyl group having 1 to 5 carbon atoms. Further, the methyl group having 1 carbon atom is preferably 30% or less in the whole benzaldehyde mixture,
More preferably, it is 20% or less. This (Ia)
It is preferable to use two or more compounds, particularly three or more compounds, together with 50% in the whole benzaldehyde mixture.
It is preferably contained, and more preferably 60% or more.

Formula (Ib)

[0030]

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In the formula, R ² represents an alkenyl group having 3 to 10 carbon atoms, preferably a 3-alkenyl group or a terminal alkenyl group, in the case where a trans (E) or cis (Z) configuration is present due to a double bond. Is preferably a trans (E) configuration, and particularly preferably a 3-butenyl group.

Formula (Ic)

[0033]

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In the formula, R ³ represents an alkoxyl group having 1 to 10 carbon atoms or an alkenyloxy group having 3 to 10 carbon atoms, but an alkoxyl group having 1 to 4 carbon atoms, or an alkoxyl group having 3 or 4 carbon atoms, -Alkenyloxy groups are preferred, and methoxy groups are particularly preferred. The content of the compound (Ic) is preferably 20% or less, more preferably 10% or less in the whole benzaldehyde mixture.

Formula (Id)

[0036]

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In the formula, R ⁴ represents a fluorine atom, a chlorine atom,
It represents a trifluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group or a cyano group, preferably a fluorine atom or a trifluoromethoxy group, particularly preferably a fluorine atom. The content of the compound (Ic) is preferably 20% or less, more preferably 10% or less in the whole benzaldehyde mixture.

The azine-based liquid crystal mixture obtained in the present invention has the general formula (II)

[0039]

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And a compound represented by the formula: In the formula, R ⁵ and R ⁶ are each independently an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 3 to 10 carbon atoms,
10, an alkoxyl group, an alkenyloxy group having 3 to 10 carbon atoms, a fluorine atom, a chlorine atom, a trifluoromethyl group,
Represents a trifluoromethoxy group, a difluoromethoxy group or a cyano group.

When two kinds of benzaldehydes are used, the liquid crystal mixture consists of three kinds of compounds of the formula (II),
In general, when n kinds of benzaldehydes are mixed and used, the liquid crystal mixture contains {n (n + 1) / 2} kinds of (II). Here, benzaldehydes are usually 2-
It is preferable to mix about seven types, but when only two types are used, the melting point of the liquid crystal mixture often does not drop sufficiently. Therefore, in order to obtain a liquid crystal state mixture at room temperature, three or more types of benzaldehydes are used. It is desirable to use.

The reaction is carried out in a solvent. Examples of the solvent include alcohols such as ethanol and methanol, hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as dichloromethane and trichloroethane, tetrahydrofuran (THF), diisopropyl Ether (IPE),
Although ethers such as ethylene glycol dimethyl ether (DME) can be used, halogenated hydrocarbons such as dichloromethane are usually preferable.

The hydrazine may be an anhydride, a hydrate, or a salt such as sulfuric acid or P-toluenesulfonic acid, but monohydrate or dihydrate is easy to use. preferable. The hydrazine is used in an amount of about 1/2 mol based on the benzaldehyde, but if the amount is small, unreacted benzaldehyde remains, and if the amount is large, the intermediate hydrazone remains. It is preferred to use 0.55 mol, especially preferred to use 0.48-0.52 mol.

The reaction can be carried out in a wide temperature range from under cooling to the boiling point of the solvent, but it is usually preferred to carry out the reaction at room temperature. When the reaction progresses slowly, it is effective to coexist a dehydrating agent such as alumina or silica gel or an acid such as hydrochloric acid.

After completion of the reaction, when a halogenated hydrocarbon such as dichloromethane or a hydrocarbon such as toluene is used as a solvent, the reaction solution is passed through a column filled with alumina or silica gel or the like directly or after washing. This makes it possible to remove unreacted hydrazine, benzaldehyde or an intermediate hydrazone, and to obtain a purified azine mixture by concentrating the distillate. When an alcohol-based solvent or the like is used, the solvent may be distilled off, then dissolved in a solvent such as dichloromethane, and the same operation may be performed. Further, when the melting point of the azine mixture is around room temperature (about 5 ° C. or higher), recrystallization from ethanol, methanol, or the like is also effective and can be used together.

Examples of azine mixtures actually produced based on the production method of the present invention are shown below. An azine mixture (M-1) produced by reacting an equimolar mixture of 4-ethylbenzaldehyde (Ia-2) and 4-propylbenzaldehyde (Ia-3), which are benzaldehydes represented by the general formula (Ia), with hydrazine. The composition after purification was as follows. (The composition represents a weight ratio.)

[0047]

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The melting point of the mixed liquid crystal (M-1) was 58 ° C., and showed a nematic phase in a wide temperature range up to 95.5 ° C. On the other hand, the phase transition temperatures of the individual compounds constituting (M-1) are as follows. Here, Cr represents a crystal phase, N represents a nematic phase, and I represents an isotropic liquid phase.

[0049]

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Accordingly, it can be seen that the mixture (M-1) has a lower melting point than the lowest melting point (II-32) among the constituents, and the temperature range is expanded. Next, 4-methylbenzaldehyde (Ia-1), which is a benzaldehyde represented by the general formula (Ia), and the above-mentioned (Ia-
2) An azine mixture (M-2) was similarly prepared from a 1/2/3/1 mixture (weight ratio) of the above (Ia-3) and 4-butylbenzaldehyde (Ia-4). This (M
-2) is a mixture consisting of 10 components (II) and showed a nematic phase from room temperature to 89 ° C. Further, this composition does not crystallize even when left at room temperature for one month or longer,
The crystal was left to crystallize at a low temperature of ℃, and its melting point was measured. Therefore, a liquid crystal composition having a temperature range substantially close to the practical range was obtained in only one step.

Incidentally, the above (M-1) or (M-
2) is a so-called n-type liquid crystal in which all the constituent components have an absolute value of dielectric anisotropy (Δε) close to 0, and cannot be driven by a normal display method such as TN or STN by itself. Therefore, it is necessary to contain a p-type liquid crystal compound having a large dielectric anisotropy in order to actually use it for display. The p-type liquid crystal compound may be an azine-based liquid crystal, a non-azine-based liquid crystal, or a mixture thereof. In the case of an azine-based liquid crystal, an n-type mixed liquid crystal may be added after the preparation, but the p-type azine-based liquid crystal is contained by using the compound (Id) as the benzaldehyde at the time of preparing the mixed liquid crystal. It is also possible to obtain a mixed liquid crystal. However, in this case, when a symmetric azine compound formed as a by-product (for example, 4-fluorobenzaldehyde is used, bis (4-fluorophenylbenzylidene) hydrazine is used.

[0052]

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Is generated. Since the solubility of ()) is extremely low, it is necessary to reduce the amount of (Id) added as described above to reduce the proportion of the symmetric azine compound in the mixed liquid crystal.

By using the production method of the present invention as described above, a multi-component azine-based mixed liquid crystal can be obtained very simply and easily. The obtained mixed liquid crystal has a low melting point and a wide temperature range, and can be easily used as a practical liquid crystal. Therefore, the production method of the present invention is very practical.

[0055]

EXAMPLES Examples of the present invention are shown below to further explain the present invention. However, the present invention is not limited to these examples.

The composition ratio and purity of the mixed liquid crystal were measured by a capillary gas chromatograph. Also,
The composition ratio is represented by% by weight. (Example 1) Synthesis of ternary mixed liquid crystal

[0057]

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In 30 g of hydrazine monohydrate, 54.3 g of 4-ethylbenzaldehyde and 60 g of 4-propylbenzaldehyde were dissolved in 400 mL of dichloromethane, and added dropwise under cooling with water for about 30 minutes. 200 mL of 10% hydrochloric acid
Was dropped at an internal temperature of 35 ° C. or lower over 1 hour. After stirring at room temperature for another 30 minutes, the aqueous layer was removed and the organic layer was washed with water and then with a saturated aqueous solution of sodium bicarbonate. The solution dried over anhydrous sodium sulfate was mixed with basic alumina 20
The mixture was passed through a column packed with 0 g, and the distillates were combined and concentrated. The obtained mixed liquid crystal (112 g) was recrystallized twice from ethanol to obtain a light yellow mixed liquid crystal (M-1) (88 g). This mixed liquid crystal showed a nematic phase at a melting point of 58 ° C. up to 95.5 ° C. This (M-1) is a screw (4
-Ethylphenylbenzylidene) hydrazine (II-2)
2), 1- (4-propylphenyl) -2- (4-ethylphenyl) hydrazine (II-32) and bis (4-
Propylphenylbenzylidene) hydrazine (II-3)
3) A composition comprising three components, the ratio of which is 19.
0 / 52.5 / 28.5 (weight ratio). Example 2 Synthesis of Three-Component Mixed Liquid Crystal (2)

[0059]

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16.9 g of hydrazine monohydrate was dissolved in 200 mL of dichloromethane, and 10 g of silica gel was added and stirred. To this, 54.0 g of 4- (3-butenyl) benzaldehyde and 50 g of 4-propylbenzaldehyde were dissolved in 200 mL of dichloromethane, and added dropwise in about 30 minutes while cooling with water. After stirring at room temperature for another 30 minutes, the reaction solution was
Passed through a column packed with 00 g silica gel. The mixed liquid crystal (118 g) obtained by combining and concentrating the distillates was recrystallized twice from ethanol to obtain a light yellow mixed liquid crystal (M
-3) 83 g was obtained. This mixed liquid crystal has a melting point of 48.5 ° C.
Showed a nematic phase up to 112.5 ° C. This (M-
3) is bis (4-propylbenzylidene) hydrazine (II-33), 1- (4-propylbenzylidene)-
A composition comprising three components of 2- [4- (3-butenyl) benzylidene] hydrazine (II-3B) and bis [4- (3-butenyl) benzylidene] hydrazine (II-BB), the ratio of which is 26. / 50/24 (weight ratio).

Incidentally, 1- (4-propylbenzylidene)
The melting point of 2- [4- (3-butenyl) benzylidene] hydrazine (II-3B) is 56 ° C., the maximum temperature of the nematic phase (T ^NI ) is 112.5 ° C., and bis [4- (3-
[Butenyl) benzylidene] hydrazine (II-BB) has a melting point of 57 ° C. and a maximum nematic phase temperature (T ^NI ) of 11;
Since the temperature is 6 ° C., it can be seen that the melting point of (M-3) is lower than that of each component, and the temperature range is expanded. (Example 3) Synthesis of 10-component mixed liquid crystal 4-benzaldehyde represented by the general formula (Ia)
Methylbenzaldehyde (Ia-1), 4-ethylbenzaldehyde (Ia-2), 4-propylbenzaldehyde (Ia-3) and 4-butylbenzaldehyde (I
An azine mixture (M-2) was prepared in the same manner as in Example 1 from the 1/2/3/1 mixture (weight ratio) of a-4). This (M-2) was a mixture consisting of 10 components (II) and showed a nematic phase from room temperature to 89 ° C. Also,
This composition does not crystallize when left at room temperature for more than one month,
It was left at a low temperature of −50 ° C. for crystallization, and its melting point was measured. Therefore, a liquid crystal composition having a temperature range almost close to a practical range could be obtained in only one step. (Application Example) Preparation of Liquid Crystal Composition 60% of (M-2) obtained in Example 3 and a 4- (trans-4-alkylclohexyl) benzonitrile mixture consisting of the following composition:

[0062]

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A liquid crystal composition (MP) consisting of 40% was prepared. This (MP) showed a nematic phase at room temperature, and its maximum temperature was 73 ° C. This (MP) did not crystallize even when left for 1 month at room temperature and 0 ° C., and crystallized when left at a low temperature of −30 ° C. The melting point was measured.
6 ° C. Next, the dielectric anisotropy of this (M-1) (Δ
When ε) was measured, it was +7. Therefore, a liquid crystal composition almost practically used was obtained.

As described above, the azine-based liquid crystal mixture very easily obtained by the production method of the present invention has a lower melting point and a wider temperature range than individual azine-based liquid crystals. Therefore, it can be seen that it is extremely useful in preparing a liquid crystal material having a low risk of crystal precipitation and a high response speed by being mixed with a general liquid crystal composition at present.

[0065]

According to the production method of the present invention, a liquid crystal mixture containing a large number of azine-based liquid crystals can be produced very easily. The obtained liquid crystal mixture has a lower melting point than individual azine compounds, has excellent solubility when mixed with a conventional liquid crystal composition, and has a low risk of crystal precipitation. Therefore, it is very useful for a practical liquid crystal display requiring a high-speed response over a wide temperature range.

Claims (4)

[Claims] 1. A compound of the general formula (Ia) (In the formula, R ¹ represents an alkyl group having 1 to 10 carbon atoms.)
And the general formula (Ib): (Wherein, R ² represents an alkenyl group having 3 to 10 carbon atoms) and a compound represented by the general formula (Ic): (Wherein, R ³ represents an alkoxyl group having 1 to 10 carbon atoms or an alkenyloxy group having 3 to 10 carbon atoms) and a compound represented by the general formula (Id): (Wherein, R ⁴ represents a fluorine atom, a chlorine atom, a trifluoromethyl group, a trifluoromethoxy group, a difluoromethoxy group or a cyano group). At least two compounds selected from benzaldehydes represented by hydrazine Reacting a compound represented by the general formula (II): (Wherein, R ⁵ and R ⁶ each independently have 1 to 10 carbon atoms)
Alkyl group, alkenyl group having 3 to 10 carbon atoms, alkoxyl group having 1 to 10 carbon atoms, alkenyloxy group having 3 to 10 carbon atoms, fluorine atom, chlorine atom, trifluoromethyl group, trifluoromethoxy group, difluoromethoxy group Alternatively, it represents a cyano group. A) a method for producing an azine-based mixed liquid crystal comprising at least three kinds of compounds represented by 2. The method according to claim 1, wherein the benzaldehyde is selected from the general formulas (Ia) and (Ib). 3. The method according to claim 1, wherein at least three kinds of benzaldehydes are used. 4. A compound represented by the general formula (Ia):
Wherein R ¹ is selected from a compound represented by a straight-chain alkyl group having 1 to 5 carbon atoms and a compound represented by formula (Ib) wherein R ² is represented by a 3-butenyl group. 4. The production method according to 2 or 3.