JP2722252B2 - Manufacturing method of liquid crystalline polyester - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an optically active liquid crystalline polyester, and more particularly to a method for producing a liquid crystalline polyester excellent in orientation and easy to fix, and excellent in optical characteristics.

[Prior Art] In recent years, polymer liquid crystals have taken advantage of their advanced molecular orientation and optical properties based on them to provide retardation plates, polarizing plates,
Applications to various fields of optoelectronics, such as various optical filters, optical recording materials, and nonlinear optical materials, are being actively studied. In particular, a polymer liquid crystal having an optically active group in a molecule can have a helical structure such as a cholesteric alignment (twisted nemantic alignment) or a chiral smectic C alignment. It can be applied to various uses utilizing the properties as an optical waveguide. In order to use these optical characteristics stably, it is generally necessary to semipermanently fix an alignment structure in a liquid crystal state which is developed at a temperature higher than room temperature. In other words, when producing an optical waveguide device using the helical orientation of an optically active liquid crystal polymer, it is essential that the liquid crystal polymer used not only has good alignment properties but also that the alignment structure can be easily fixed. is there.

Known types of optically active polymer liquid crystals include side-chain polymer liquid crystals such as polypeptides, polysiloxanes, polyacrylates, and polymethacrylates, and main-chain polymer liquid crystals such as polyesters. As a prior art, for example, an example in which a cholesteric structure of a polypeptide is immobilized and used for a notch filter is disclosed in JP-A-60-19.
1203. However, this method dissolves polyglutamic acid ester in a polymerizable solvent, forms a lyotropic liquid crystal, and then fixes the cholesteric structure by photopolymerizing the solvent, which requires time, cost, and complicated operations. It is extremely disadvantageous industrially.

In the case of other types of optically active polymer liquid crystals, there have been few reports of attempts to apply helical structures to industrial applications, but polysiloxane type polymer liquid crystals are generally difficult to manufacture due to the complicated manufacturing process. In addition, the glass transition point (Tg) is lower than room temperature, which makes it difficult to fix, and even if it can be fixed once, the structure is relaxed due to the low Tg, which eventually destroys the orientation structure. There is. In the case of polyacrylate type and polymethacrylate type, introduction of an optically active group into a side chain does not always result in cholesteric liquid crystal, but often results in smectic liquid crystal. In order to obtain a cholesteric phase, precise control of the structure (length of the spacer, composition, etc.) is required, and furthermore, there is a disadvantage that the synthesis of the polymer is complicated, the cost is high, and industrial production is difficult.

On the other hand, polyesters are industrially easily available from monomers that are easily available industrially, and are industrially advantageous, such as having excellent mechanical and physical strengths.However, since the rigidity of molecules is higher than other types, However, in most cases, since a crystal phase is present in a lower temperature portion than a liquid crystal phase rather than a glass phase, crystallization occurs at the time of immobilization, and the orientation of the liquid crystal is disturbed, so that the helical structure in the liquid crystal state cannot be fixed.

[Problems to be Solved by the Invention] The present inventors have solved the above-mentioned drawbacks of the polyester-based polymer liquid crystal, and in order to obtain a good helical orientation in the liquid crystal state and to easily fix the orientation, a liquid crystal was used. As a result of studying to produce a polymer in which the phase at a lower temperature than the phase is a glass phase, the present invention has been finally reached.

[Means for Solving the Problems] That is, the present invention provides a method for producing a polyester by subjecting a substantially equimolar amount of a dicarboxylic acid compound and a diol compound to a condensation reaction in the absence of an oxycarboxylic acid compound. An aromatic diol having two hydroxyl groups at the ortho position (provided that the aromatic group is a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms or a hydrogen atom thereof is a halogen atom and a carbon atom of 1 to 4 5 mol% or more based on the total monomer compound polymerizing the above-mentioned aromatic hydrocarbon group substituted with an alkyl group or an alkoxy group or a phenyl group) or its ester-forming derivative (I), and an optically active carbon in the main chain. Aliphatic diol having an atom (however, the aliphatic group is a divalent saturated aliphatic hydrocarbon group having 3 to 20 carbon atoms or a hydrogen atom thereof) The above-mentioned aliphatic hydrocarbon group substituted by a halogen atom, a halogen-containing alkyl group or an alkoxy group having 1 to 4 carbon atoms or a phenyl group) or an ester-forming derivative thereof (II). This is a method for producing an optically active liquid crystalline polyester having a glass phase in a phase lower than the liquid crystal phase characterized by using at least mol%.

In the polyester obtained by the present invention, a structural unit derived from the above monomer compound plays a characteristic role. Aromatic diol compounds (I) having two hydroxyl groups in the ortho position form the corresponding ortho bonded dioxy aromatic repeat units in the main chain in the resulting polyester, which results in a glass phase. Specific examples in the form of the structural unit provided by (I) are as follows.

(Wherein X represents a substituent, k represents an integer of 0 to 2) The substituent X is, for example, a halogen atom such as fluorine, chlorine, bromine, etc., a methyl group, an ethyl group, a propyl group, an isopropyl group, and n Examples thereof include an alkyl group such as -butyl group and t-butyl group, an alkoxy group such as methoxy group, ethoxy group, propyloxy group, isopropyloxy group, butyloxy group and t-butyloxy group, and a phenyl group. Specific examples of preferred structural units include the following structural units. (In the formula, Me represents a methyl group and Bu represents a butyl group.) The amount of the aromatic diol compound (I) is at least 5 mol%, preferably at least 7 mol%, particularly preferably at least 10 mol%, based on all monomer compounds to be polymerized. If it is less than 5 mol%, a crystal phase appears in a lower temperature portion than the liquid crystal phase, and it is difficult to fix the crystal phase. The upper limit is up to 50 mol% in total with the optically active aliphatic diol compound (II) due to the characteristics of the condensation reaction. Examples of the ester-forming derivative include an acetylated product.

Optically active aliphatic diol (or its derivative) (II)
Is an essential component for the polyester to exhibit optical activity and exhibit a helical alignment such as a cholesteric alignment in a liquid crystal state. Specific examples of the structural units obtained from this are as follows. (In the formula, * indicates optically active carbon.) Among others Etc. are particularly preferred.

The optically active aliphatic diol compound is used in an amount of at least 0.01 mol%, preferably at least 0.05 mol%, particularly preferably at least 0.1 mol%, based on all monomers to be polymerized. If the amount is less than 0.01 mol%, the helical pitch becomes too long, and there is a practical problem. These compounds may be either R-form or S-form, or may be a mixture of R-form and S-form. In this case, the difference between the two needs to be 1% or more, preferably 10% or more, and particularly preferably 20% or more. If it is less than 1%, it is difficult to obtain a necessary spiral structure.

In the present invention, the ortho-aromatic diol compound (I) and the optically active aliphatic diol compound (II) are converted into a polyester by a condensation reaction with a dicarboxylic acid compound. The type of the dicarboxylic acid compound in this case is not particularly limited, but an aromatic dicarboxylic acid compound, particularly an aromatic or alicyclic dicarboxylic acid compound having no carboxyl group (or a derivative thereof) at the ortho position is preferable.
The aromatic dicarboxylic acid compound having a carboxyl group at the ortho position (that is, the compound having a structure other than the ester-forming group corresponding to (I)) should be 70 mol% or less based on the total monomers with (I). is there.

Specific examples of the dicarboxylic acid compound in the form of a structural unit are as follows.

(Z represents hydrogen, a halogen such as Cl or Br, an alkyl group or an alkoxy group having 1 to 4 carbon atoms, or a phenyl group. M is 0 to 2.) Above all, Are preferred. These dicarboxylic acid compounds and the above-mentioned diol compounds are subjected to a condensation reaction in substantially equimolar relation as in the production of ordinary polyesters. The molecular weight of these polyesters is preferably such that the logarithmic viscosity measured at 30 ° C. in various solvents such as a phenol / tetrachloroethane (60/40 weight ratio) mixed solvent is in the range of 0.05 to 5.0, and more preferably in the range of 0.1 to 3.0. Logarithmic viscosity is 0.05
If it is smaller than this, the mechanical and physical strength is remarkably reduced, and if it is more than 5.0, the viscosity is too high and the orientation in the liquid crystal state is unpreferably reduced.

The method for synthesizing these polymers is not particularly limited, and is synthesized by a polymerization method known in the art, for example, a melt polymerization method or an acid chloride method using a corresponding acid chloride of dicarboxylic acid. When synthesizing by the melt polycondensation method,
For example, it can be produced by polymerizing an acetylated product of a corresponding dicarboxylic acid and a corresponding diol under high temperature and high vacuum, and the molecular weight can be easily controlled by controlling the polymerization time or controlling the charged composition. In order to accelerate the polymerization reaction, a conventionally known metal salt such as sodium acetate can be used. When a solution polymerization method is used, a desired polyether can be easily obtained by dissolving a predetermined amount of dicarboxylic acid dichloride and diol in a solvent and heating in the presence of an acid acceptor such as pyridine.

Since the polyester of the present invention has a structural unit containing an optically active group in the molecule, the polyester has a helical alignment such as a cholesteric alignment in a liquid crystal state. In addition, since it contains as its structural unit an aromatic component that is ortho-positioned according to the main-chain bond in the molecule, it has a glass phase at a lower temperature than the liquid crystal phase and easily breaks the helical alignment in the liquid crystal state. Can be fixed. Therefore, those obtained by fixing the helical orientation can not only be used semi-permanently and stably in the vicinity of a greenhouse, but also have excellent properties as an optical waveguide due to high transparency, and various optical filters and retardation plates And a polarizing plate.

[Examples] Examples will be described below, but the present invention is not limited thereto. In addition, each analysis method used in the Example is as follows.

(1) Determination of polymer composition The polymer was dissolved in deuterated chloroform or deuterated trifluoroacetic acid and subjected to 400 MHz ¹ H-NMR (JEOL J
NM-GX400).

(2) Measurement of logarithmic viscosity The viscosity was measured at 30 ° C. in a phenol / tetrachloroethane (60/40 weight ratio) mixed solvent using an Ubbelohde viscometer.

(3) Measurement of DSC It was measured using DuPont990 Thermal Analizer.

(4) Optical Microscope Observation Observation was performed using an hB2 polarizing microscope manufactured by Olympus Optical Co., Ltd.

Example 1 Terephthalic acid dichloride 34 mmol, methylhydroquinone 17 mmol, catechol 17 mmol, (S) -2-methyl-1,
A solution of 1.0 mmol of 4-butanediol and 16 ml of pyridine in 50 ml of orthodichlorobezen was polymerized at 70 ° C. for 3 hours under a nitrogen stream. Next, after passing the reaction solution, it was poured into methanol to precipitate a polymer, and then dried under reduced pressure to synthesize a polyester having the properties shown in Table 1. The yield was 8.2 g. The ¹ H-NMR spectrum of this polymer is shown in FIG. When the texture of the polymer in a liquid crystal state was observed under crossed Nicols using a polarizing microscope, a very clean fingerprint-like structure, which is a typical cholesteric texture, was observed, and a texture of about 10 μm was observed.
It was found to have a pitch length of m. Cholesteric phase → glass phase (Tg = 90 ° C) by DSC measurement (falling temperature)
Was found to change phase.

A tetrachloroethane solution of this polymer is applied on a slide glass, dried, and then placed on a hot plate for 180 minutes.
The film obtained by cooling the product that had been heat-treated at 5 ° C for 5 minutes was transparent, and the structure similar to that observed in the liquid crystal state was observed by observation with a polarizing microscope, and the alignment structure in the liquid crystal state was clearly fixed. I knew it was.

Example 2 4,4'-biphenyldicarboxylic acid dichloride 24 mmo
l, methylhydroquinone 18 mmol, catechol mmol,
A solution of 0.43 mmol of (S) -2-methyl-1,4-butanediol and 13 ml of pyridine in 50 ml of orthodichlorobenzene was polymerized at 70 ° C. for 2 hours under a nitrogen stream.
Next, after passing the reaction solution, it was poured into methanol to precipitate a polymer, and then dried under reduced pressure to synthesize a polyester having the properties shown in Table 1. The yield was 10.8 g. The ¹ H-NMR spectrum of this polymer is shown in FIG. In addition, DSC measurement (temperature decrease) revealed that the phase changed from a cholesteric phase to a glass phase (Tg = 98 ° C.).

Observation of this polymer under a polarizing microscope in the same manner as in Example 1 revealed that a clear fingerprint-like structure was observed and that the polymer had a cholesteric orientation. Pitch length is about
It was 20 μm. Further, it was found that the film obtained by heat treatment and cooling in the same manner as in Example 1 was transparent and maintained the cholesteric orientation as it was, and the orientation structure in the liquid crystal state was fixed.

Examples 3 to 11 (where 10 is a reference example) Various polyesters shown in Table 1 were synthesized in the same manner as in Example 1. Each of the obtained polymers had a glass phase below a liquid crystal phase. In addition, by performing heat treatment and fixing in the same manner as in Example 1, the alignment structure in the liquid crystal state could be fixed, and the obtained film was transparent.

Comparative Examples 1-2 The polymers shown in Table 1 were synthesized in the same manner as in Example 1.
Comparative Example 1 has a crystal phase below the liquid crystal phase because the polymer does not include a structural unit in which the bond forming the main chain is at the ortho position, and the same heat treatment and cooling operation as in Example 1 were performed. However, the orientation in the liquid crystal state could not be fixed, and the resulting film was cloudy and had low transparency.
In Comparative Example 2, the structural unit having a main chain bond at the ortho position (in this case, a catechol unit) was too small at 3%, and thus had a crystalline phase, and only a film which could not be fixed and was cloudy was obtained. I couldn't.

〔The invention's effect〕

The optically active liquid crystal polyester of the present invention is not only industrially easy to produce, but also has good alignment in the liquid crystal state and can fix its alignment structure by cooling,
Since the immobilized product is completely transparent, it can be applied to various uses utilizing its optical characteristics as an optical waveguide, and is of extremely high industrial value.

[Brief description of the drawings]

1 and 2 show ¹ H-NMR spectra of the polyesters synthesized in Examples 1 and 2, respectively.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hajime Hara 4-5-11-1 Kugenuma Fujigaya, Fujisawa City, Kanagawa Prefecture (56) References JP-A-64-90219 (JP, A)

Claims (1)

(57) [Claims] 1. A process for producing a polyester by subjecting a substantially equimolar amount of a dicarboxylic acid compound and a diol compound to a condensation reaction in the absence of an oxycarboxylic acid compound.
As a diol compound, an aromatic diol having two hydroxyl groups at the ortho position (however, the aromatic group has a carbon number of 6 to
A divalent aromatic hydrocarbon group of 20 or the above-mentioned aromatic hydrocarbon group in which the hydrogen atom is substituted with a halogen atom, an alkyl group or an alkoxy group having 1 to 4 carbon atoms or a phenyl group) or An aliphatic diol having an optically active carbon atom in the main chain of at least 5 mol% based on all monomer compounds polymerizing the ester-forming derivative (where the aliphatic group is a divalent saturated aliphatic hydrocarbon group having 3 to 20 carbon atoms) Or a hydrogen atom thereof is a halogen atom and has 1 carbon atom
Or the above-mentioned aliphatic hydrocarbon group substituted with a halogen-containing alkyl group or alkoxy group or phenyl group from 1 to 4) or an ester-forming derivative thereof is used in an amount of 0.01 mol% or more based on all monomer compounds to be polymerized. A method for producing an optically active liquid crystalline polyester having a glass phase in a phase lower than the liquid crystal phase.