JPH11106493A - Liquid crystal polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject compound having high birefringence, enabling the fixation of liquid crystal phase by cooling and useful as a high-birefringence optical film by using a specific structural unit as the constituent unit and restricting the logarithmic viscosity within a specific range. SOLUTION: This liquid crystal polyester has a logarithmic viscosity of 0.05-1.0 measured in a phenol/tetrachloroethane solvent mixture (60/40 wt. ratio) at a concentration of 0.5 g/dL at 30 deg.C and is composed of (A) 20-80 mol.% of a structural unit of formula I (R is H, OCH3 or OC2 H5 ; (n) is 1 or 2), (B) 10-40 mol.% of a structural unit of formula II [X is 1,4-phenylene (W1 ), naphthalene-2,6-diyl (W2 ), etc.], (C) 10-40 mol.% of a structural unit of the formula III, (D) 0-1.0 mol.% of a structural unit of formula IV (Y is W1 , W2 , toluene-2,5-diyl, etc.), and (E) 0-20 mol.% of a structural unit of formula V (Z is W1 , W2 or biphenyl-4,4'-diyl).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel liquid crystalline polyester and a novel optical film comprising the polyester having a high birefringence and suitable for application to the field of optoelectronics.

[0002]

2. Description of the Related Art It is known that liquid crystals have a specific order of molecular orientation depending on the type of liquid crystal. Therefore, liquid crystals are applied to various fields by utilizing or controlling the molecular orientation, and form a large industrial field. As for the low-molecular liquid crystal, as is well known, a nematic type liquid crystal is widely used as a display element of a clock, a calculator, a television, or the like. In the field of electronic displays, it has already established a solid position. As described above, in the low-molecular liquid crystal, applications based on the electro-optical effect occupy most of the applications.

On the other hand, polymer liquid crystals exhibit the same electro-optical effect or thermo-optical effect as low-molecular liquid crystals, depending on the type of nematic, smectic and cholesteric liquid crystals, in addition to their mechanical properties. Is well known. Polymer liquid crystals cannot be used for the same applications as low molecular liquid crystals because response to external forces such as electric fields and heat is slower than low molecular liquid crystals. However, the polymer liquid crystal has a great feature that an alignment structure specific to each type of liquid crystal can be fixed. A polymer liquid crystal in which an alignment structure specific to the liquid crystal is fixed depending on the type of the liquid crystal is used as a display material and a recording material. In addition, polymer liquid crystals can be easily formed into films and thin films which are advantageous for optical materials, and the polymer liquid crystals formed into films and thin films can be applied to various fields.

On the other hand, birefringence (Δn) can be cited as a characteristic property value of liquid crystal irrespective of low molecular weight or high molecular weight. The Δn value of a low-molecular nematic liquid crystal depends on the molecular structure, and is based on a tolan (（0.28), azo, or azoxy (0.
25 to 0.30), Schiff bases (〜0.24), and pyrimidines (〜0.23) show relatively large Δn values. In addition, cyclohexylcyclohexane (~ 0.0
6), cyclohexylcarboxylic acid ester type (<0.
1), phenylcyclohexane (0.08 to 0.1)
9) shows a small Δn value. The Δn value is one of the important parameters in the electronic display field,
Due to the characteristics of the physical properties, a highly functional display can be developed. For example, in order to reduce the cell thickness of a display device and increase the response speed, a low molecular nematic liquid crystal has been designed to have a high Δn. Further, in the dual-STN, it is desired to increase the liquid crystal Δn in order to increase the display contrast. Thus, in the electronic display field, although the Δn value is an important parameter,
The Δn value of the nematic liquid crystal is usually about 0.1 to 0.3, and the application to a further electronic display has been stopped.

In order to increase the Δn value, it is necessary to increase the value by a unique molecular structure. Since the Δn value depends on the polarizability of the molecule and the orientation order parameter,
Molecules with high polarizability that cause optical anisotropy, benzene rings and polycyclic aromatics that are conjugated molecules with high electron density,
It is known that the compound is improved by a compound such as an ethylene-acetylene chain group or a terminal cyano group. Based on this,
M. Hird et al. Report a low molecular weight liquid crystal having a Δn: 〜0.43 from a polycyclic aromatic tolan-based liquid crystal having a high polarizability (M. Hird et. Al, Liquid Crys).
tals, 1993, 15, 123)

However, there is usually no polymer liquid crystal having a Δn value exceeding 0.3, and Δn is slightly increased by a mechanical stretching treatment of an aromatic polyamide.
Only examples raised to 65 have been reported (H.H.
G. FIG. Rogers et. al, Macromolec
ules, 1985, 18, 1058). In order to apply polymer liquid crystals to the field of optoelectronics such as recording media and memory devices, development of polymer liquid crystals that have both self-alignment properties above the glass transition temperature (Tg) and self-memory properties below the Tg is required. Obviously, the necessity of such a liquid crystalline polymer has not been reported. As described above, in order to develop new applications and applications of polymer liquid crystals, it is essential to develop polymer liquid crystals having a high Δn value due to the self-alignment of the liquid crystals themselves. Development was desired.

[0007]

The present inventors have conducted intensive studies to solve the above-mentioned problems. As a result, they show a liquid crystal phase at the time of melting, and can fix the liquid crystal phase by cooling to a liquid crystal transition temperature or lower. The above problem was solved by developing a new liquid crystalline polyester.

[0008]

Means for Solving the Problems In the main chain type liquid crystalline polyester, the present inventors have developed a liquid crystal polyester having a high polarizability specific monomer unit having a conjugated system extended in the main chain direction and a catechol unit. The present invention has led to the invention of a new optical film having a high birefringence by using the polyester. That is, the first of the present invention
Is composed of the following structural units (A), (B), (C) and, if necessary, (D) and / or (E), and has a concentration of 0 in a phenol / tetrachloroethane (60/40 by weight) mixed solvent. A liquid crystalline polyester having a logarithmic viscosity measured at 0.5 g / dl and a temperature of 30 ° C. of 0.05 to 1.0.

[0009]

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[0010]

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[0011]

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[0012]

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[0013]

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A second aspect of the present invention is that the first liquid crystalline polyester is characterized in that it exhibits a liquid crystal phase when melted and that the liquid crystal phase can be fixed by cooling to a liquid crystal transition temperature or lower. About. A third aspect of the present invention relates to an optical film formed from the liquid crystalline polyester according to the first or second aspect of the present invention. Here, the meaning that the liquid crystal phase can be fixed by cooling to the liquid crystal transition temperature or lower in the second aspect of the present invention means that the nematic liquid crystalline polyester composition in a liquid crystal state was cooled at an arbitrary cooling rate. In this case, substantially no phase transition to the crystal phase occurs, and the molecular orientation state in the liquid crystal state can be maintained as it is below the liquid crystal transition temperature (glass transition temperature). Further, that substantially no phase transition to the crystal phase occurs means that the existence of the crystal phase is not recognized at least by the optical measurement method.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystalline polyester of the present invention comprises
Structural units (A), (B) and (C) are essential structural units,
It is a polyester having units (D) and / or (E) as required.

The structural unit (A) is an essential component for expressing a high birefringence, and is derived from 4'-hydroxy-4-stilbenecarboxylic acid (substituted with alkoxy) or a functional derivative of the carboxylic acid. Unit. Here, the alkoxy-substituted carboxylic acid means 4′-hydroxy-2′-methoxy-4-stilbene carboxylic acid,
4'-hydroxy-3'-methoxy-4-stilbenecarboxylic acid, 4'-hydroxy-2 ', 3'-dimethoxy-4-stilbenecarboxylic acid, 4'-hydroxy-
2 ′, 5′-dimethoxy-4-stilbenecarboxylic acid,
4'-hydroxy-2 ', 6'-dimethoxy-4-stilbenecarboxylic acid, 4'-hydroxy-2'-ethoxy-4-stilbenecarboxylic acid, 4'-hydroxy-3'
-Ethoxy-4-stilbenecarboxylic acid, 4'-hydroxy-2 ', 3'-diethoxy-4-stilbenecarboxylic acid, 4'-hydroxy-2', 5'-diethoxy-4
-Stilbenecarboxylic acid, 4'-hydroxy-2 ',
6'-diethoxy-4-stilbenecarboxylic acid, 4'-
Hydroxy-2'-methoxy-3'-ethoxy-4-stilbenecarboxylic acid, 4'-hydroxy-2'-methoxy-5'-ethoxy-4-stilbenecarboxylic acid, 4 '
-Hydroxy-2'-methoxy-6'-ethoxy-4-
Stilbenecarboxylic acid, 4′-hydroxy-3′-methoxy-2′-ethoxy-4-stilbenecarboxylic acid,
4'-hydroxy-3'-methoxy-5'-ethoxy-
4-stilbenecarboxylic acid, 4′-hydroxy-3′-
And methoxy-6'-ethoxy-4-stilbenecarboxylic acid.

In the structural unit (A), a hydroxycarboxylic acid component other than the unit, specifically, the structural unit (E)
4- (4'-hydroxyphenyl) benzoic acid, 6
A unit derived from -hydroxy-2-naphthalenecarboxylic acid, 4-hydroxybenzoic acid, or a functional derivative thereof (eg, an acetoxy compound, an alkyl ester such as a methyl ester) can be included as necessary. The structural unit (A) is usually 2 units in the liquid crystalline polyester.
It is present in a proportion of 0 to 80 mol%, preferably 25 to 75 mol%, more preferably 30 to 70 mol%. When the structural unit (E) is contained, the composition ratio (molar ratio) of the structural units (A) and (E) is usually 1/19 as (A) / (E).
It is determined in the range of from 79/1, preferably from 10/20 to 69/1, but it is desirable in the present invention that the polyester contains at least 20 mol% or more of the structural unit (A).

The structural unit (B) is a component which plays a role as a mesogen for exhibiting liquid crystallinity. Specifically, 4,4'-stilbene dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid, , 6-naphthalenedicarboxylic acid, 4,4'-dicarboxydiphenyl ether, terephthalic acid, bromoterephthalic acid or functional derivatives of these dicarboxylic acids (for example, dialkyl esters such as dimethyl ester and acid chlorides such as dichloride). Is a unit. The structural unit (B) is usually 10 to 40 mol%, preferably 15 to 3 mol% in the liquid crystalline polyester.
It is present in a proportion of 5 mol%, more preferably 20 to 35 mol%.

Next, the structural unit (C) is a component that plays a role in fixing the liquid crystal phase under cooling, and specifically, is derived from catechol or a functional derivative of catechol (for example, a derivative such as a diacetoxy compound). Unit. In addition, a diol component other than the unit, specifically, 4,4′-dihydroxystilbene, 4,4′-biphenol, 2,6-dihydroxynaphthalene, hydroquinone, methylhydroquinone or a functional derivative thereof as the structural unit (D) (For example, a derivative derived from a diacetoxy compound or the like), if necessary. The structural unit (C) is
Usually 10 to 40 mol%, preferably 15 to 35 mol%,
More preferably, it is present in a proportion of 20 to 35 mol%.
When the structural unit (D) is included, the structural unit (C),
The composition ratio (molar ratio) of (D) is usually determined as (C) / (D) in the range of 1/9 to 39/1, preferably 5/10 to 34/1. It is desirable in the present invention that the structural unit (C) contains at least 10 mol% or more.

The composition ratio (molar ratio) when the structural units (B) and (C) and, if necessary, the structural unit (D) is included, is based on the stoichiometric amount of the dicarboxylic acid component and the diol component in the production reaction of the polyester. Because it needs to be
It is approximately 1 as (B) / (C) or (B) / (C) + (D), and is usually in the range of 45/55 to 55/45, preferably 48/52 to 52/48. Specific examples of the liquid crystalline polyester of the present invention,

[0021]

Embedded image a: 20 to 80 mol%, preferably 30 to 70 mol
% B or c: 10 to 40 mol%, preferably 15 to 3
5mol%

[0022]

Embedded image a: 20 to 80 mol%, preferably 30 to 70 mol
% B or c: 10 to 40 mol%, preferably 15 to 3
5mol%

[0023]

Embedded image a: 20 to 80 mol%, preferably 30 to 70 mol
% B or c: 10 to 40 mol%, preferably 15 to 3
5mol%

[0024]

Embedded image a: 20 to 80 mol%, preferably 30 to 70 mol
% B or c: 10 to 40 mol%, preferably 15 to 3
5mol%

[0025]

Embedded image a: 20 to 80 mol%, preferably 30 to 70 mol
% B or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/1.
0-34 / 1

[0026]

Embedded image a: 20 to 80 mol%, preferably 30 to 70 mol
% B or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/1.
0-34 / 1

[0027]

Embedded image a: 20 to 80 mol%, preferably 30 to 70 mol
% B or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/1.
0-34 / 1

[0028]

Embedded image a: 20 to 80 mol%, preferably 30 to 70 mol
% B or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/1.
0-34 / 1

[0029]

Embedded image a: 20 to 80 mol%, preferably 30 to 70 mol
% B or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/1.
0-34 / 1

[0030]

Embedded image a + d: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / d is 1/19 to 79/1, preferably 10
/ 20-69 / 1 b or c: 10-40 mol%, preferably 15-3
5mol%

[0031]

Embedded image a + d: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / d is 1/19 to 79/1, preferably 10
/ 20-69 / 1 b or c: 10-40 mol%, preferably 15-3
5mol%

[0032]

Embedded image a + d: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / d is 1/19 to 79/1, preferably 10
/ 20-69 / 1 b or c: 10-40 mol%, preferably 15-3
5mol%

[0033]

Embedded image a + e: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / e is 1/19 to 79/1, preferably 10 /
20 to 69/1 b or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/10.
~ 34/1

[0034]

Embedded image a + e: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / e is 1/19 to 79/1, preferably 10 /
20 to 69/1 b or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/10.
~ 34/1

[0035]

Embedded image a + e: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / e is 1/19 to 79/1, preferably 10 /
20 to 69/1 b or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/10.
~ 34/1

[0036]

Embedded image a + e: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / e is 1/19 to 79/1, preferably 10 /
20 to 69/1 b or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/10.
~ 34/1

[0037]

Embedded image a + e: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / e is 1/19 to 79/1, preferably 10 /
20 to 69/1 b or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/10.
~ 34/1

[0038]

Embedded image a + e: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / e is 1/19 to 79/1, preferably 10 /
20 to 69/1 b or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/10.
~ 34/1

[0039]

Embedded image a + e: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / e is 1/19 to 79/1, preferably 10 /
20 to 69/1 b or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/10.
~ 34/1

[0040]

Embedded image a + e: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / e is 1/19 to 79/1, preferably 10 /
20 to 69/1 b or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/10.
~ 34/1

[0041]

Embedded image a + e: 20 to 80 mol%, preferably 30 to 70 m
ol% where a / e is 1/19 to 79/1, preferably 10 /
20 to 69/1 b or c + d: 10 to 40 mol%, preferably 15
However, c / d is 1/9 to 39/1, preferably 5/10.
To 34/1.

Here, the molecular weight of the liquid crystalline polyester of the present invention is determined based on the phenol / tetrachloroethane mixed solvent (60
/ 40 weight ratio), the value of ηinh measured at 30 ° C.
Usually 0.05 to 1.0, preferably 0.07 to 0.5,
More preferably, it is 0.1 to 0.3. When the value of ηinh is higher than 1.0, the fluidity in the liquid crystal state may be reduced, and it may be difficult to obtain uniform alignment. If ηinh is lower than 0.05, the strength may be weakened, which may cause a practical problem.

The molecular weight of the liquid crystalline polyester can be easily adjusted by controlling the polymerization time or the like as in the ordinary condensation reaction.

The liquid crystalline polyester of the present invention can be obtained by copolymerizing monomer components corresponding to the above structural units. The polymerization method is not particularly limited, and can be synthesized by applying a polymerization method known in the art, for example, a melt polymerization method or a solution polymerization method.

The charge ratios of the structural units (A), (B) and (C) constituting the polyester and, if necessary, the monomer components constituting the (D) and / or (E) are as follows:
The content of each structural unit described above, specifically, the structural unit (A): 20 to 80 mol%, the structural unit (B): 10 to 40 mol%, and the structural unit (C): 1 in the polyester.
0 to 40 mol%, and if necessary, structural unit (D): 0
-20 mol%, and / or structural unit (E): 0-2
The content is 0 mol%, and the dicarboxylic acid component (B) and the diol components (C) and (D) are set to have a substantial stoichiometric amount.

When the liquid crystalline polyester of the present invention is synthesized by a melt polymerization method, for example, a predetermined amount of 4'-acetoxy-3'-methoxy-stilbenecarboxylic acid (monomer forming the structural unit (A)) 4,4'-stilbene The desired polyester can be easily obtained by polymerizing dicarboxylic acid (monomer forming the structural unit (B)) and catechol diacetate (monomer forming the structural unit (C)) under high temperature, normal pressure or reduced pressure.

The polymerization conditions are not particularly limited, but are usually 150 to 350 ° C., preferably 200 to 300 ° C., and the reaction time is 30 minutes or more, preferably about 1 to 20 hours. It is desirable to carry out the polymerization reaction under reduced pressure. In order to promote the polymerization reaction, 1-methylimidazole, amines such as 4-dimethylaminopyridine,
Alkali metal salt, Fe, Mn, Ti, Co, Sb, Sn
Such metal salts may be used alone or in combination.

When the liquid crystalline polyester of the present invention is produced by a solution polymerization method, for example, a predetermined amount of 4′-hydroxy-3′-methoxy-4-stilbenecarboxylic acid (monomer forming the structural unit (A)), 4'-Stilbene dicarboxylic acid (structural unit (B) forming monomer) and catechol (structural unit (C) forming monomer) are dissolved in a solvent and heated, or dissolved in pyridine or the like, and arylsulfonyl chloride / dimethylformamide or chlorophosphoric acid is dissolved. By heating in the presence of diphenyl / dimethylformamide, the desired polyester can be easily obtained.

The solvent used in the solution polymerization is not particularly limited. For example, halogen solvents such as o-dichlorobenzene, dichloroethane and tetrachloroethane, dimethylsulfoxide (DMSO), dimethylformamide (DMF), N-methylpyrrolidone (NMP ), Polar solvents such as pyridine, and ether solvents such as tetrahydrofuran (THF) and dioxane. The reaction conditions for the solution polymerization are not particularly limited, but are usually at a temperature of 5
The reaction time is usually 1 hour or more, preferably 2 hours to 10 hours.

The liquid crystalline polyester of the present invention, which can be produced as described above, depends on the composition ratio and the like, and cannot be said unconditionally, but can usually form a nematic phase and a smectic phase in a liquid crystal state. Further, when the liquid crystalline polyester in a liquid crystal state is cooled at an arbitrary cooling rate, substantially no phase transition to a crystal phase occurs. When the temperature is equal to or lower than the liquid crystal transition temperature (glass transition temperature), it is characterized in that the molecular alignment state in a liquid crystal state, specifically, the alignment state in a nematic phase and a smectic phase can be maintained as it is.

The liquid crystalline polyester of the present invention may be used as a composition by mixing with other liquid crystalline polymers, non-liquid crystalline polymers and the like. Further, by blending the polyester with an optically active low molecular weight compound or high molecular weight compound to form a composition, a liquid crystal composition having a cholesteric phase or a twisted nematic phase as a liquid crystal phase can be obtained.

The liquid crystalline polyester of the present invention can produce an optical film having a fixed nematic or smectic orientation by utilizing the property of maintaining the molecular orientation state in the liquid crystal state as it is.

In the present invention, it is preferable that the optical film is manufactured by following an alignment substrate and each step described below.

Specific examples of the alignment substrate include polyimide, polyimide amide, polyamide, polyether imide, polyether ketone, polyketone sulfide, polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polyethylene naphthalate, and the like. Plastic film substrates such as polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, and phenol resin, the above-mentioned plastic film substrates whose surfaces have been rubbed, and alkali glass, borosilicate glass, and flint glass whose surfaces are etched into slits A substrate having in-plane anisotropy such as a glass substrate is preferably used.

The optical film of the present invention can be obtained by uniformly coating a liquid crystalline polyester on the above-mentioned alignment substrate, then performing a uniform alignment process and a process of fixing the alignment form. The application of the polyester to the oriented substrate can be usually performed in a solution state in which the polyester is dissolved in various solvents or in a molten state in which the polyester is melted. From the viewpoint of the production process, it is preferable to apply the solution by applying the solution in which the liquid crystalline polyester is dissolved in a solvent.

The solution application will be described. The liquid crystalline polyester of the present invention is dissolved in a solvent to prepare a solution having a predetermined concentration. Since the thickness of the film (the thickness of the layer formed of the liquid crystalline polyester) is determined at the stage of applying the polyester to the substrate, it is necessary to precisely control the concentration, the thickness of the coating film, and the like.

The above-mentioned solvent cannot be said unconditionally because it varies depending on the composition ratio of the liquid crystalline polyester of the present invention, etc., but it is usually chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, orthodichloromethane. Halogenated hydrocarbons such as chlorobenzene, phenols such as phenol and parachlorophenol,
Benzene, toluene, xylene, methoxybenzene,
Aromatic hydrocarbons such as 1,2-dimethoxybenzene, acetone, ethyl acetate, tert-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, ethyl cellosolve, butyl cellosolve, 2-pyrrolidone, N-methyl-2-pyrrolidone, pyridine, triethylamine, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethylsulfoxide, acetonitrile, butyronitrile, carbon disulfide and the like, and a mixed solvent thereof such as halogenated hydrocarbons and phenol And the like.

The concentration of the solution cannot be determined unconditionally because it depends on the solubility of the liquid crystalline polyester to be used and the thickness of the optical film finally intended, but it is usually used in the range of 3 to 50% by weight. Preferably it is in the range of 7 to 30% by weight. By adjusting to the above concentration, usually 0.1 μm
20 μm or less, preferably 0.2 μm or more and 10 μm or less
Hereinafter, an optical film having a film thickness of preferably 0.3 μm or more and 5 μm or less can be obtained.

A solution of a liquid crystalline polyester adjusted to a desired concentration using the above-mentioned solvent is then applied onto the above-described alignment substrate. As a coating method, a spin coating method, a roll coating method, a die coating method, a printing method, an immersion pulling method, a curtain coating method, or the like can be adopted.

After the application, the solvent is removed, and a layer of the composition having a uniform thickness is formed on the alignment substrate. The solvent removal conditions are:
There is no particular limitation, as long as the solvent can be substantially removed and the liquid crystalline polyester layer does not flow or run off. Usually, the solvent is removed by drying at room temperature, drying in a drying furnace, or blowing hot or hot air.

After drying, a heat treatment is carried out usually at 50 ° C. to 300 ° C., preferably at 100 ° C. to 260 ° C. to orient the liquid crystalline polyester in a liquid crystal state. The heat treatment time varies depending on, for example, the composition ratio of the liquid crystalline polyester to be used, and cannot be unconditionally determined, but is usually in the range of 10 seconds to 120 minutes, preferably 30 seconds to 60 minutes. If the time is shorter than 10 seconds, there is a possibility that uniform alignment in the liquid crystal state becomes insufficient. If the time is longer than 120 minutes, productivity may decrease, which is not desirable.

As described above, the liquid crystalline polyester of the present invention can be uniformly aligned in the liquid crystal state over the entire surface of the alignment substrate. In the present invention, in the heat treatment step, a magnetic field or an electric field may be used to uniformly align the liquid crystalline polyester.

The uniform alignment formed by the heat treatment is then cooled to a temperature below the liquid crystal transition point of the polyester, whereby the uniformity of the alignment can be fixed without any loss.

The cooling temperature is not particularly limited as long as it is lower than the liquid crystal transition point. For example, 10 ° C from the liquid crystal transition point
By cooling at a low temperature, uniform orientation can be fixed. There is no particular limitation on the cooling means, and the cooling is carried out by simply taking out from the heating atmosphere in the heat treatment step to an atmosphere below the liquid crystal transition point, for example, at room temperature. In order to increase production efficiency, forced cooling such as air cooling or water cooling or cooling may be performed. Through the above steps, the optical film of the present invention can be obtained.

The optical film may be used in such a manner that the above-mentioned oriented substrate is peeled off from the film and used as a single optical film, used as it is formed on the oriented substrate, or another substrate different from the oriented substrate. And laminating optical films.

When used as a film alone, a method of mechanically peeling the oriented substrate at the interface with the optical film using a roll or the like, a method of mechanically peeling after dipping in a poor solvent for all structural materials, A method of peeling by applying ultrasonic waves in a poor solvent, a method of peeling by giving a temperature change using a difference in thermal expansion coefficient between the oriented substrate and the film, the oriented substrate itself, or the oriented film on the oriented substrate. A film alone is obtained by a method of dissolving and removing. Since the releasability differs depending on the composition ratio of the liquid crystalline polyester to be used and the adhesion to the alignment substrate, a method most suitable for the system should be adopted. When the optical film alone is used as an optical element, depending on the film thickness, there may be no self-supporting property, but in that case, a substrate preferable in optical properties, for example, polymethacrylate, polycarbonate, polyvinyl alcohol, polyether sulfone, polysulfone It is more desirable to use the optical film fixed on a plastic substrate such as polyarylate, polyimide, amorphous polyolefin, triacetylcellulose and the like via an adhesive or a pressure-sensitive adhesive for the strength and reliability of the optical film.

Next, a case where an optical film is used while being formed on an alignment substrate will be described. When the alignment substrate is transparent and optically isotropic, or when used as an optical element, the alignment substrate is a necessary member for the element, it can be used as it is as a target optical element.

Further, the optical film of the present invention obtained by fixing the liquid crystalline polyester on the alignment substrate may be peeled off from the substrate and laminated on another substrate more suitable for optical use. it can. That is, a laminate composed of at least the film and another substrate different from the alignment substrate can be incorporated into a TN-LCD or the like as, for example, an optical element. Specifically, the following method can be adopted.

A substrate suitable for a target optical element (hereinafter, referred to as a substrate)
The second substrate) and the optical film on the alignment substrate,
For example, it is pasted using an adhesive or an adhesive. Next, the alignment substrate is peeled off at the interface with the optical film of the present invention, and the film is transferred to a second substrate side suitable for an optical element to obtain an optical element.

The second substrate used for the transfer is not particularly limited as long as it has an appropriate flatness.
A glass substrate or a transparent plastic film having optical isotropy is preferably used. Examples of such a plastic film include polymethyl methacrylate, polystyrene, polycarbonate, polyether sulfone, polyphenylene sulfide, polyarylate, amorphous polyolefin, triacetyl cellulose, and epoxy resin. Among them, polymethyl methacrylate, polycarbonate, polyarylate, polyether sulfone, triacetyl cellulose and the like are preferably used. Even if it is optically anisotropic, an optically anisotropic film can be used if it is a necessary member for an optical element. Examples of such a film include a retardation film and a polarizing film obtained by stretching a plastic film such as polycarbonate or polystyrene.

The adhesive or pressure-sensitive adhesive for adhering the second substrate used for transfer and the optical film of the present invention is preferably of optical grade, and is preferably of acrylic, epoxy or ethylene-vinyl acetate copolymer type. , Rubber, urethane, and mixtures thereof. As the adhesive, any adhesive such as a thermosetting type, a photocuring type, and an electron beam curing type can be used without any problem as long as it has optical isotropy.

The transfer of the optical film of the present invention to a second substrate suitable for an optical element can be performed by bonding the second substrate to the optical film and then peeling the oriented substrate at the interface with the film. Although the peeling method has been described above, a method of mechanically peeling using a roll or the like, a method of peeling by applying ultrasonic waves in a poor solvent, utilizing a difference in thermal expansion coefficient between the oriented substrate and the film. And a method of dissolving and removing the alignment substrate itself or the alignment film on the alignment substrate. Since the releasability depends on the composition ratio of the liquid crystalline polyester to be used and the adhesion to the alignment substrate, a method most suitable for the system should be adopted. The optical film of the present invention may be provided with a protective layer such as a transparent plastic film for the purpose of protecting the surface, increasing the strength, and improving environmental reliability.

The optical film of the present invention obtained as described above has a birefringence of 0.1 at a wavelength of 590 nm, which cannot be unconditionally determined by the composition ratio of the liquid crystalline polyester.
It has physical properties of 3 or more. The birefringence can be measured by the known technique. Specifically, it is determined by the interferometry of an Abbe refractometer or an ultraviolet-visible spectrometer.

As described above, the liquid crystalline polyester of the present invention is suitable as an optical material because it can fix liquid crystal alignment and has a uniform film forming ability. Further, the optical film made of the liquid crystalline polyester has a high birefringence which has been difficult to obtain with a self-aligned polymer liquid crystal film, and can be expected to be applied to new optical applications. Further, the birefringence can be adjusted to a desired value by changing the composition ratio of the liquid crystalline polyester.

As described above, the liquid crystalline polyester of the present invention and the optical film made of the polyester are optically
The application to the optoelectronics field can be greatly expected, and the industrial value is extremely high.

[0076]

EXAMPLES Examples will be described below, but the present invention is not limited to these examples. In addition, each analytical method used in the Example is as follows. 1. Logarithmic viscosity Phenol / 1,1,2,2 using Ubbelohde viscometer
The measurement was carried out at a polymer concentration of 0.5 g / dl and 30 ° C. using tetrachloroethane = 60/40 (weight ratio) as a solvent. 2. Glass transition temperature Dupont 990 Thermal Analiz
20 ° C./min. At a heating rate of 3. Optical Structure Observation Observation was performed using a hot stage FP80 / 82 manufactured by Mettler and a BH-2 polarizing microscope manufactured by Olympus Optical.

4. Measurement of birefringence (Δn) A 15 wt% NMP solution of liquid crystalline polyester was prepared,
After applying the solution using a spin coater on a substrate that has been subjected to an alignment treatment (rubbing treatment), the substrate is dried on a hot plate and subjected to heat treatment using an oven. Then, the film is allowed to cool to obtain a film fixed in a uniform orientation state. The extinction axis of the obtained film is checked under crossed Nicols with a polarizing microscope equipped with a rotating stage, and the refractive index of the extinction axis along the rubbing direction is defined as ne, and the refractive index of the perpendicular extinction axis is defined as no.

In the case of ne <1.8, no <1.8 Using an Abbe refractometer, and using an NaD line (590 nm), n
e and no were measured, and the birefringence Δn (590 nm) = ne
(590 nm) -no (590 nm). In case of ne ≧ 1.8, no <1.8 No is measured by NaD line (590 nm) using an Abbe refractometer.
Was measured. Next, ne × d (590 nm) and no × d (590 nm) at 590 nm orthogonal to each other were measured using polarized light along the film extinction axis by an interference film thickness meter. Here, d is the film thickness. Film thickness d from no (590 nm) obtained from Abbe refractometer
Was calculated as d = no × d (590 nm) / no (590 nm). Using the obtained film thickness d, ne = ne × d (590 nm) / d was calculated to obtain a birefringence index Δn (590 nm) = ne−no.

5. Determination of composition The obtained polyester is dissolved in deuterated dimethyl sulfoxide or deuterated trifluoroacetic acid,
z was measured by ¹ H-NMR (JNM-GX400 manufactured by JEOL) and determined.

Example 1 14.06 g (45 mmol) of 4'-acetoxy-3'-methoxy-4-stilbenecarboxylic acid and 6-acetoxy-2 were placed in a polymerization reactor equipped with a stirrer, a nitrogen inlet tube and a liquid trap. 3.45 g of naphthoic acid (15 mmo
l), 6.12 g (31.5 m) of catechol diacetate
mol) and 4.98 g (30 mmol) of terephthalic acid
l) was charged and the inside of the reactor was replaced with nitrogen. Under nitrogen atmosphere,
260 ° C. for 2 hours at 240 ° C.
After reacting at 270 ° C for 2 hours and 270 ° C for 12 hours,
10 ml / min. From the nitrogen inlet tube. The reaction was further carried out at 270 ° C. for 1 hour while introducing nitrogen. The logarithmic viscosity of the obtained polyester is 0.19 and the glass transition temperature is 1
It was 10 ° C. As a result of observation by a polarizing microscope, this polyester showed a nematic liquid crystal phase at a temperature higher than the glass transition temperature, and even when cooled down to a temperature lower than the glass transition temperature, no transition to a crystal phase was observed and the nematic liquid crystal state could be fixed. .

Next, 15 wt% of the obtained polyester
A tetrachloroethane solution was prepared. The solution was applied on a rubbing polyimide alignment film by a spin coating method.
Next, after drying and removing, heat treatment was performed at 210 ° C. for 10 minutes. As a result, a film composed of a liquid crystalline polyester was obtained on the rubbing polyimide alignment film. The obtained film was transparent and free of alignment defects, and had a uniform film thickness (2.1 μm).
m). As a result of measuring the birefringence using this film, the birefringence (Δn) at a wavelength of 590 nm was 0.393 (ne: 1.973, no: 1.580).

[0082]

Embedded image

Examples 2 to 13 The reaction was carried out in the same manner as in Example 1 except that the monomer charging ratio was changed. The results are shown in Tables 1 and 2.
In addition, all the obtained polyesters showed a nematic liquid crystal phase above the glass transition temperature as a result of observation with a polarizing microscope, and even when cooled below the glass transition temperature, no transition to the crystal phase was observed and the nematic liquid crystal state was fixed. It was possible. Further, for all the obtained polyesters, films were prepared in the same manner as in Example 1, and the birefringence at a wavelength of 590 nm was measured.

Comparative Example 1 7.28 g (35 mm) of methylhydroquinone diacetate
ol), catechol diacetate 12.62 g (65 m
mol) and 16.61 g of terephthalic acid (100 mm
ol), but the reaction was carried out in the same manner as in Synthesis Example 1. The logarithmic viscosity of the obtained polyester is 0.1
5. The glass transition temperature was 108 ° C.

As a result of observation by a polarizing microscope, this polyester showed a nematic liquid crystal phase at a temperature equal to or higher than the glass transition temperature.
Further, even when cooled to a temperature below the glass transition temperature, no transition to a crystal phase was observed, and the nematic liquid crystal state could be fixed.
As a result of preparing a film and measuring the birefringence, the birefringence of the polyester in the liquid crystal fixed state was 0.20 (n
_e : 1.750, n _O : 1.550).

[0086]

[Table 1]

[0087]

[Table 2]

[Brief description of the drawings]

1 shows an NMR spectrum of the liquid crystalline polyester of Example 1. FIG.

FIG. 2 shows an NMR spectrum of the liquid crystalline polyester of Example 2.

FIG. 3 shows an NMR spectrum of the liquid crystalline polyester of Example 10.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shinichiro Suzuki 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Japan Nippon Oil & Oil Co., Ltd.

Claims (3)

[Claims] 1. A composition comprising the following structural units (A), (B), (C) and, if necessary, (D) and / or (E), wherein phenol / tetrachloroethane (weight ratio: 60/4)
0) A liquid crystalline polyester having a logarithmic viscosity of 0.05 to 1.0 measured at a concentration of 0.5 g / dl and a temperature of 30 ° C. in a mixed solvent. Embedded image Embedded image Embedded image Embedded image Embedded image 2. The liquid crystalline polyester according to claim 1, wherein the liquid crystalline polyester exhibits a liquid crystal phase upon melting and can be fixed by cooling to a liquid crystal transition temperature or lower. 3. An optical film formed from the liquid crystalline polyester according to claim 1.