JP3125169B2 - Liquid crystalline polyester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystalline polyester which can easily fix liquid crystal alignment to glass and is suitable for application to optical elements.

[0002]

2. Description of the Related Art In recent years, polymer liquid crystals have been used in the field of high-performance materials utilizing high heat resistance and moldability, and functional materials utilizing the change of the liquid crystal phase structure due to an external field such as heat or an electric field and the immobilization of phases. It has been actively researched and developed in the field, and has already been commercialized in the field of high performance materials. On the other hand, in the field of functional materials, active research is being conducted for the application to optical recording, nonlinear optical materials, liquid crystal alignment films, optical fibers, optical elements for liquid crystal display elements, etc., but none has been commercialized yet. When a polymer liquid crystal is applied to a functional material, most of them use a phase structure obtained in a liquid crystal state with being fixed. This is where polymer liquid crystals can be immobilized, which is a great attraction.However, in order to be able to immobilize and the immobilized liquid crystal structure to be stable at the operating temperature, the polymer liquid crystal used must be glassy at a temperature lower than the liquid crystal transition point. It is essential to have a phase. When a polymer having a crystalline phase at a temperature lower than the liquid crystal transition point is used, the liquid crystal cannot be fixed or the liquid crystal structure once fixed is relaxed with time. The types of the polymer liquid crystal can be roughly classified into a main-chain polymer liquid crystal and a side-chain polymer liquid crystal. From an industrial point of view, the main-chain liquid crystal is preferred from the viewpoint of cost or ease of production. Is preferred.

However, many polyesters generally have high crystallinity and are difficult to immobilize, and at present the application to functional materials has not progressed much.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystalline polyester having a glass phase at a temperature lower than the liquid crystal transition point and capable of easily fixing an alignment structure in a liquid crystal state. It is an object of the present invention to provide a novel polyester suitable for the application of the present invention.

[0005]

That is, the present invention relates to a nematic liquid crystalline polyester comprising the following structural units.

[0006]

Embedded image

(Where R is

Embedded image Represents a divalent hydrocarbon group selected from, X and Y represents a hydrogen atom, Cl, Br or an alkyl group having 1 to 4 carbon atoms, the composition in terms of molar ratio of (A + B) / (C + D)
Is in the range of 45/55 to 55/45, and A / B is 2
In the range of 5/25 to 48/2, with a C / D of 10/4
0 to 45/5).

The polymer of the present invention comprises a terephthalic acid unit,
Consists of linear or branched aliphatic dicarboxylic acid units, hydroquinone or substituted hydroquinone units and catechol or substituted catechol units. Although a large number of liquid crystalline polyesters comprising an aromatic compound are known, a polymer containing an aliphatic dicarboxylic acid unit and a catechol unit in the same polymer is not known. Generally, in order to exhibit good liquid crystallinity, a rigid and highly linear molecule is preferable, but a catechol unit and an aliphatic dicarboxylic acid unit act in a direction that disrupts the linearity of the molecule.

The present inventors aimed at synthesizing a polyester suitable for a functional material, and aggressively introduced a combination of these units which is usually avoided, so that the polymer of the present invention impaired the liquid crystallinity. Without this, the present inventors have found that a glass phase is formed at a temperature lower than the liquid crystal transition point (that is, the glass transition point Tg) and the liquid crystal structure can be fixed, and the present invention has been completed.

The A unit is a unit derived from a polyester-forming functional derivative such as terephthalic acid or dimethyl terephthalate, and the B unit has the following structural portion and corresponds to
That derived from polyester-forming functions derivatives such as linear or branched aliphatic dicarboxylic acids or their diacetate
Is done.

[0011]

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[0012]

[0013]

[0014]

The C unit is a unit based on a polyester-forming functional derivative such as hydroquinone or substituted hydroquinone or a diacetate thereof, and X is a hydrogen atom, Cl, Br or an alkyl group having 1 to 4 carbon atoms. As the alkyl group, a methyl group, an ethyl group, i-
Examples thereof include a propyl group, a butyl group and a t-butyl group, and among them, a methyl group, an ethyl group and a t-butyl group are particularly preferable. The D unit is a unit based on a polyester-forming functional derivative such as catechol or substituted catechol or a diacetate thereof, and Y is a hydrogen atom, Cl, Br or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, an i-propyl group, a butyl group and a t-butyl group,
Among them, a methyl group, an ethyl group and a t-butyl group are particularly preferred.

When the composition of these units in the polymer is represented by a molar ratio, (A + B) / (C + D) is 45/55.
To 55/45, preferably 48/52 to 52
/ 48, particularly preferably 50/50. A / B is preferably in the range of 25/25 to 48/2, and particularly preferably in the range of 30/20 to 45/5. When this value is smaller than 25/25, that is, when the amount of the aliphatic dicarboxylic acid unit is too large, the expression of liquid crystallinity is undesirably inhibited. Conversely, when the ratio is larger than 48/2, that is, when the amount of terephthalic acid is too large, depending on the balance with the amount of the catechol unit, the polymer tends to crystallize or the solubility of the polymer in a solvent decreases. It is not preferable because it causes adverse effects.

The value of C / D is from 10/40 to 45/5.
Is particularly preferable, and the range of 15/35 to 40/10 is particularly preferable. When this value is smaller than 10/40, that is, when the amount of catechol units is too large, the expression of liquid crystallinity is unfavorably inhibited, and when this value is larger than 45/5, that is, when the amount of hydroquinone units is too large, the polymer becomes It is not preferable because it has a crystal layer.

The polymer has a molecular weight of 30 ° C. in a phenol / tetrachloroethane mixed solvent (60/40 weight ratio).
The value of ηinh measured in the above is preferably from 0.05 to 3.0, particularly preferably from 0.07 to 2.0. ηin
If the value of h is less than 0.05, the strength may be weak. If the value of h is more than 3.0, the melt viscosity may be too high and the orientation of the liquid crystal may be reduced.

The Tg of these polymers is preferably 0 ° C. or higher, more preferably 20 ° C. or higher, and the upper limit is not particularly limited, but is preferably about 300 ° C. Tg is 0
When the temperature is lower than ℃, even if the liquid crystal alignment is fixed once, the alignment is gradually relaxed thereafter, resulting in disorder of the structure, which may make it difficult to use the material stably as an industrial material.

The method for synthesizing the polymer of the present invention is not particularly limited, and is synthesized by a polymerization method known in the art, for example, a melt polymerization method or a solution polymerization method using a corresponding acid chloride of dicarboxylic acid.

The molten When synthesizing in polycondensation of terephthalic acid (A ¹ component) One example, the aliphatic dicarboxylic acids (B ¹ component) having a R moiety, hydroquinone represented by the general formula (1) di Acetates (X is C ¹ as described above)
Hydroquinone diacetates represented by the components) and the general formula (2) (Y is similar to the above, the D ¹ component), high temperature, can be prepared by polymerizing under high vacuum.

[0022]

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Examples of the hydroquinone diacetates include hydroquinone diacetate, methyl hydroquinone diacetate, ethyl hydroquinone diacetate, t-butyl hydroquinone diacetate, chlorohydroquinone diacetate, and bromohydroquinone diacetate. Examples of the catechol diacetates include catechol diacetate, methyl catechol diacetate, ethyl catechol diacetate, propyl catechol diacetate, t-butyl catechol diacetate, bromocatechol diacetate, and chlorocatechol diacetate.

The molecular weight can be easily controlled by controlling the polymerization time or the charge composition. The polymerization conditions in that case are not particularly limited, but usually at a temperature of 150 ° C.
To 350 ° C., preferably 200 ° C. to 300 ° C., and the reaction time is 30 minutes or more, preferably about 1 hour to 20 hours, and the reaction can be performed under normal pressure or reduced pressure. The charged composition (molar ratio) of each of the raw material components A ^{1 to} D ¹ is (A ¹ + B ¹ )
The value of / (C ¹ + D ¹ ) is usually 40/60 to 60/4
0, preferably 45/55 to 55/45, more preferably 48/52 to 52/48, particularly preferably 50/45.
/ 50.

The value of A ¹ / B ¹ is from 25/25 to 48/2.
Is particularly preferable, and the range of 30/20 to 45/5 is particularly preferable. The value of C ¹ / D ¹ is 10/40 to 45/45.
/ 5 is preferred, especially from 15/35 to 40/10
Is preferable.

In order to accelerate the polymerization reaction, conventionally known metal salts such as sodium acetate and zinc acetate can also be used.

When the liquid crystalline polyester of the present invention is produced by a solution polymerization method, terephthalic acid dihalide (A ²
Component), dihalides of aliphatic dicarboxylic acids having the R moiety (B component ² ), hydroquinones (C component ² ) represented by the general formula (3), and catechols (D ² ) is dissolved in a solvent and heated in the presence of an acid acceptor such as pyridine to easily obtain the desired polyester.

[0028]

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Examples of the terephthalic acid dihalide include terephthalic acid dichloride and terephthalic acid dibromide. The hydroquinones include hydroquinone, methylhydroquinone, ethylhydroquinone, t-
Butylhydroquinone, chlorohydroquinone, bromohydroquinone, and the like. Examples of the catechols include:
Catechol, methyl catechol, ethyl catechol, propyl catechol, t-butyl catechol, chlorocatechol, bromocatechol and the like.

The solvent to be used is not particularly limited. For example, halogen solvents such as o-dichlorobenzene, dichloroethane and tetrachloroethane, DMSO, DMF, N
Examples thereof include polar solvents such as MP, and ether solvents such as THF and dioxane. Examples of the acid acceptor include, but are not particularly limited to, pyridine, triethylamine, and tripropylamine.

The conditions for the solution polymerization are not particularly limited, but the temperature is usually 50 ° C. to 200 ° C., preferably 60 ° C. to 150 ° C., and the reaction time is 1 hour to 10 hours, preferably 2 hours to 7 hours. The charged composition (molar ratio) of each of the raw material components A ^{2 to} D ² is (A ² + B ² ) / (C ² + D ² ).
Is usually 40/60 to 60/40, preferably 4
5/55 to 55/45, more preferably 48/52
To 52/48, particularly preferably 50/50. A
² / the value of ^{B 2} is preferably in the range of 48/2 from 25/25, preferably ranging especially from 30/20 to 45/5. Further, the value of C ² / D ² is preferably in the range of 10/40 to 45/5, particularly preferably in the range of 15/45 to 40/10.

[0032]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. 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 measured and determined by 400 MHz ¹ H-NMR (JNM-GX400 manufactured by JEOL Ltd.).

(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 DuPont 990 Thermal AnaliZe
It was measured using r.

(4) Observation with Optical Microscope Observation was performed using a BH2 polarizing microscope manufactured by Olympus Optical Co., Ltd.

Example 1 Terephthalic acid dichloride 9
0 mmol, glutaric acid dichloride 10 mmol, hydroquinone 35 mmol and catechol 70 mmol
Was dissolved in 500 ml of o-dichlorobenzene, 50 ml of pyridine was added as an acid acceptor, and the mixture was heated and stirred at 70 ° C. for 4 hours under a nitrogen stream to synthesize a polymer. The reaction solution was poured into a large amount of methanol, and the precipitated polymer was recovered. Table 1 shows the composition and ηinh of the obtained polymer. According to DSC measurement and observation with a polarizing microscope, Tg had a glass phase at 93 ° C., and showed a nematic liquid crystal phase at a higher temperature. A small amount of the polymer was placed on a slide glass, a cover glass was placed on it, and the sample was heated on a hot plate at 180 ° C. for 15 minutes, then cooled down from the hot plate and cooled. It was completely immobilized.

[Examples 2 to 5 (However, Example 5 is outside the scope of the present invention.)
The polymers of Examples 2 to 5 were synthesized according to Example 1. The properties of the obtained polymer are shown in Table 1. All of the polymers had a nematic liquid crystal phase at Tg or higher and had no crystal phase. In the same manner as in Example 1, the Tg was changed from the liquid crystal state.
By cooling to the following temperature, a highly transparent film in which the nematic alignment state in the liquid crystal was fixed was obtained.

Example 6 80 mmol of terephthalic acid,
20 mmol of pimelic acid, 50 mmol of methylhydroquinone diacetate and 50 m of catechol diacetate
was heated and stirred at 270 ° C. for 8 hours under a nitrogen stream to synthesize a polymer. The polymer was purified by dissolving the obtained polymer in tetrachloroethane and throwing it into a large amount of methanol. Table 1 shows the composition and ηinh of the obtained polymer. According to DSC measurement and observation with a polarizing microscope, Tg had a glass phase at 78 ° C., and showed a nematic liquid crystal phase at a higher temperature. A small amount of the polymer was placed on a slide glass, placed on a cover glass, heated on a hot plate at 220 ° C. for 10 minutes, and then cooled and cooled from the hot plate. The nematic liquid crystal phase was found to be transparent by polarization microscopy. It was completely immobilized.

Examples 7 and 8 The polymers of Examples 7 and 8 were synthesized according to Example 6. The properties of the obtained polymer are shown in Table 1. In each case, the nematic alignment state in the liquid crystal was fixed by cooling from the liquid crystal state to a temperature of Tg or less in the same manner as in Example 6. Was obtained.

Comparative Example 1 Terephthalic acid 20 mmol,
Adipic acid 80 mmol, hydroquinone diacetate 5
0 mmol and catechol diacetate 50 mmol
And heated and stirred at 270 ° C. for 8 hours under a nitrogen stream to synthesize a polymer. The polymer was purified by dissolving the obtained polymer in tetrachloroethane and throwing it into a large amount of methanol. Table 1 shows the composition and ηinh of the obtained polymer. This polymer had a Tg of 45 ° C. as a result of DSC measurement and observation with a polarizing microscope,
It had no liquid crystal phase and had a glass phase at a temperature lower than Tg, and an isotropic phase at a temperature higher than Tg.

Comparative Example 2 Terephthalic acid 70 mmol,
Suberic acid 30 mmol, hydroquinone diacetate 9
5 mmol and catechol diacetate 5 mmol
Was heated and stirred at 270 ° C. for 8 hours under a nitrogen stream to synthesize a polymer. By dissolving the obtained polymer in tetrachloroethane and throwing it into a large amount of methanol,
The polymer was purified. Composition of the obtained polymer and η
The inh is shown in Table 1. This polymer showed a nematic liquid crystal phase, but had a clear crystallization peak in DSC measurement and no Tg. An attempt was made to fix the liquid crystal structure in the same manner as in Example 1. However, the fixation was not possible due to the presence of the crystalline phase, and the film obtained after cooling was a cloudy crystalline polymer.

[0042]

[Table 1]

[0043]

Since the liquid crystalline polyester of the present invention has a glass phase at a temperature lower than the liquid crystal transition point, the liquid crystal polyester is cooled from the temperature at which the liquid crystal state is exhibited to a temperature lower than the liquid crystal transition point (glass transition point). The orientation structure in the state can be fixed. The thus obtained transparent material having a liquid crystal alignment structure can be suitably used for various functional materials, particularly for optical elements, and is extremely valuable industrially.

[Brief description of the drawings]

[1] ¹ of polyester obtained in Example 3 of the present invention
1 shows an H-NMR spectrum.

FIG. 2 shows ^{1 of} the polyester obtained in Example 6 of the present invention.
1 shows an H-NMR spectrum.

FIG. 3 shows ^{1 of} the polyester obtained in Example 7 of the present invention.
1 shows an H-NMR spectrum.

FIG. 4 shows the D of the polyester obtained in Example 2 of the present invention.
3 shows an SC thermogram.

FIG. 5 shows a DSC thermogram of the polyester obtained in Example 5 (Reference Example) of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 63/00-63/91 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A nematic liquid crystalline polyester comprising the following structural units: (Wherein R is ## STR2 ## Represents a divalent hydrocarbon group selected from, X and Y represents a hydrogen atom, Cl, Br or an alkyl group having 1 to 4 carbon atoms, the composition in terms of molar ratio of (A + B) / (C + D)
Is in the range of 45/55 to 55/45, and A / B is 2
In the range of 5/25 to 48/2, with a C / D of 10/4
0 to 45/5).