JPH08253680A - Aromatic polyether sulfone solution composition and method for producing film - Google Patents

Abstract

(57) [Summary] [Purpose] When an aromatic polyether sulfone film is produced by a solution casting method, it improves the releasability of the casting film from the supporting substrate, and it has excellent optical isotropy and homogeneity. Provided is a method for producing a family polyethersulfone film. [Structure] A small amount of water and / or lower aliphatic alcohol is contained in an aromatic polyether sulfone solution composition containing a solvent mainly composed of 1,3-dioxolane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solution composition of an aromatic polyether sulfone film and a method for producing an aromatic polyether sulfone film obtained from the solution composition. More specifically, a casting film in a semi-dried state when continuously casting an aromatic polyether sulfone film useful for optical applications such as display elements or electric / electronic equipment applications by a solution casting method (casting method) Excellent peelability when peeling from the support substrate, surface properties, transparency,
The present invention relates to a stable solution composition which gives an aromatic polyether sulfone film having good optical homogeneity, and a method for producing the film using the same.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been attracting attention because of their low power consumption and excellent image quality, and are being put into practical use. In these liquid crystal display devices,
Polymer films are used for polarizing plates, protective layers, retardation plates, electrode substrates and the like. Among them, the polymer electrode substrate, that is, the plastic substrate is used instead of the conventional glass substrate for making the liquid crystal display lighter and thinner, and has extremely high optical isotropy in order to accurately transmit the transmitted polarized light to the liquid crystal layer. And homogeneity is required. Furthermore, heat resistance is required to withstand heat applied during processing such as film formation of the transparent electrode and formation of an alignment film. For that purpose, unstretched polycarbonate film, polyarylate film, etc. are used, and from the viewpoint of heat resistance, a film made of aromatic polyether sulfone is also promising because it shows extremely excellent properties [Junji Takase, “Electrode Recent Development Trends of Substrate Films ", Proc. Of the Society of Polymer Electronics, Polymer Electronics Society, p20 (November 11, 1993; at Sophia University)]. However, the aromatic polyether sulfone has a high polarizability because it contains an aromatic group in the molecule, and therefore has a drawback that even a slight molecular orientation causes optical anisotropy in the aromatic polyether sulfone film. . From this point of view, the development of a technique for forming a film of an aromatic polyether sulfone film having excellent optical isotropy by suppressing the molecular orientation as much as possible is an important issue.

On the other hand, the retardation film is used for improving the visibility of images in STN type liquid crystal display elements and TN type liquid crystal display elements, and converts elliptically polarized light transmitted through the liquid crystal layer into linearly polarized light. Play a role. As these materials, a uniaxially stretched polycarbonate film or a polyvinyl alcohol film is mainly used. Due to the recent demand for improving the image visibility of high-speed response liquid crystal displays, a retardation film having a wavelength dispersion property of a retardation that matches the high-speed liquid crystal layer has been demanded, and an aromatic polyether sulfone film is promising. [Akio Murayama, Masato Shoko, Susumu Kondo, Makoto Hasegawa,
"Optical Design of Simple Matrix STN-LCD", Society of Polymer Science, 2nd Polymer Materials Forum, p267 (19)
December 1, 1993, Tokyo, National Education Center)]. As described above, the aromatic polyether sulfone has a high polarizability because it contains an aromatic group in the molecule, and optical anisotropy is easily obtained by uniaxially stretching the film for molecular orientation. Therefore, it is advantageous that the retardation required for the retardation film can be obtained by a slight stretching, but on the other hand,
It is difficult to obtain an optically uniform oriented film. In order to obtain such an oriented film, it is necessary to use a film which is optically highly isotropic at the stage of an unstretched film (raw film).

Generally, an aromatic polyether sulfone film is formed by a melt extrusion method, particularly a T-die method. The T-die method is widely used as a method for forming a plastic film. However, since a high-viscosity melt is extruded, polymer chains are easily oriented and stress strain is likely to remain in the film. Quality and homogeneity are difficult to obtain. In order to lower the melt viscosity, it is necessary to lower the molecular weight of the plastic or raise the film-forming temperature, but lowering the molecular weight lowers the mechanical properties of the film, and raising the film-forming temperature causes thermal deterioration and coloring. It is easy to induce. Further, since the melt extruded from the T-die is directly and rapidly cooled, streaks due to the T-die, so-called die lines, tend to be generated, and it is difficult to obtain a film having a high surface property [Junji Takase, “Recent Development Trend of Electrode Substrate Film” , Society of Polymer Science, Polymer Electronics Society, p20 (November 11, 1993)
Sun; at Sophia University)]. The surface properties and optical homogeneity required for films used in liquid crystal display devices are quite severe. For example, for plastic substrates, surface thickness variation ± 5μ
m or less, a phase difference of 10 nm or less, and an optical axis alignment of ± 10 # or less are required, and the original film for a phase difference film has a surface thickness unevenness of 2 μm or less, a phase difference of 30 nm or less, an optical axis alignment of ±.
1 ° or less is required. Here, the optical axis orientation refers to the direction in which the refractive index is maximum in the film plane, that is, the direction of the slow axis. In reality, it is difficult to meet such strict requirements by the melt extrusion method.

Under these circumstances, a solution casting method (casting method) is used as a method for forming an aromatic polyether sulfone film satisfying high surface properties, optical isotropy and homogeneity.
Is regarded as influential. The solution casting method is a method in which a solution composition (dope) is cast on a supporting substrate and then heated to remove most of the solvent to form a self-supporting film, which is then peeled off from the supporting substrate and further dried by heating. Then, the remaining solvent is removed to form a film. This solution casting method is currently used as a method for forming a polycarbonate film used in a liquid crystal display device. We previously reported that an aromatic polyether sulfone solution composition consisting of 1,3-dioxolane
It was found to be extremely effective in the production of an aromatic polyether sulfone film by the solution casting method, and proposed.
In the process of this study, aromatic polyether sulfone has high adhesion when peeling a semi-dried film that is heated to remove most of the solvent after dope casting and peeled from a metal plate that is usually used as a supporting substrate. Often bad Due to the high peeling strength, peeling streaks and peeling scratches are contained in the film, or the film is stretched and whitened at a part of the film. It is extremely difficult to obtain a film having good surface properties. An easily conceivable means for solving this problem is to add a release agent such as a fluorine-based, silicon-based, or stearic acid-based release agent to the dope.
However, since these release agents remain in the film even after the film is formed, it is unavoidable that the glass transition point of the film is lowered. Further, the film may be whitened due to the deposition of the release agent. Furthermore, when a film containing a release agent is used for a liquid crystal display device, it is not preferable because the adhesiveness to other members in the post-processing step may decrease. From the above, regarding the solution casting method of the aromatic polyether sulfone film, a method for improving the peelability of the cast film from the supporting substrate without impairing the physical properties of the film has been demanded.

[0006]

The object of the present invention is to provide a solution casting method of an aromatic polyether sulfone film, which has a good releasability of the casting film from a supporting substrate, and therefore has excellent surface properties, transparency and optical properties. An object of the present invention is to provide a method for producing an aromatic polyether sulfone film having excellent homogeneity.

[0007]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that a solvent mainly containing 1,3-dioxolane contains a small amount of water and / or a lower aliphatic alcohol. When the aromatic polyether sulfone solution composition is used, the peelability of the cast film from the supporting substrate is good, and therefore, an aromatic polyether sulfone film having excellent surface properties, transparency and optical homogeneity can be obtained. They have found the present invention and reached the present invention.

That is, the present invention is based on water and 1 to 6 carbon atoms.
1 to 10% by weight of at least one straight or branched chain aliphatic alcohol and 99 to 90% by weight of a solvent mainly comprising 1,3-dioxolane.
It is an aromatic polyether sulfone solution composition containing 90 parts by weight and 10 parts by weight of aromatic polyether sulfone.

The present invention will be described in detail below.

The aromatic polyether sulfone used in the present invention is a generic term for those having an aromatic group bonded to the skeleton by a sulfone group and an ether group. For example, the following general formulas (1) to (3)

[0011]

Embedded image (—Ar ¹ —SO ₂ —Ar ² —O—) (1) (—Ar ³ —X—Ar ⁴ —O—Ar ⁵ —SO ₂ —Ar ⁶ —O—) (2) (− _{^{Ar 7 -SO 2 -Ar 8 -O-}} Ar 9 -O-) (3) [ in the formula (1), Ar ¹ and Ar ² are the same or different aromatic hydrocarbon group having 6 to 12 carbon atoms. In formula (2),
Ar ^{3 to} Ar ⁶ are the same or different aromatic hydrocarbon groups having 6 to 12 carbon atoms, and X is a divalent hydrocarbon group having 1 to 15 carbon atoms. In the formula (3), Ar ^{7 to} Ar ⁹ are the same or different aromatic hydrocarbon groups having 6 to 12 carbon atoms. ] An aromatic polyether sulfone comprising at least one repeating unit selected from the group consisting of

Here, Ar ¹ and A which are preferable in the formula (1)
r ² is an arylene group having 6 to 12 carbon atoms, and an arylene group having 6 to 10 carbon atoms is more preferable. Specific examples include an m-phenylene group, a p-phenylene group, a dimethyl-p-phenylene group, a tetramethyl-p-phenylene group, a naphthylene group, and a biphenylene group.
A case where both Ar ¹ and Ar ² are p-phenylene groups is advantageous in terms of production and is particularly preferably used.

Suitable Ar ^{3 to} Ar ⁶ in the formula (2) is an arylene group having 6 to 12 carbon atoms and 6 carbon atoms.
More preferred are arylene groups of -10. Specifically, m
-Phenylene group, p-phenylene group, dimethyl-p-phenylene group, tetramethyl-p-phenylene group, naphthylene group, biphenylene group and the like. Preferable examples of all of Ar ^{3 to} Ar ⁶ are p-phenylene groups. X is a divalent hydrocarbon group having 1 to 15 carbon atoms, and is selected from a divalent aliphatic hydrocarbon group having 1 to 15 carbon atoms, an alicyclic hydrocarbon group, and an alkylene group. It is preferably a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group, or an alkylene group. Specifically, methylene group, 1,1-ethylene group, 2,2-propylene group, 2,2-butylene group, 4-methyl-2,2-
Aliphatic hydrocarbon group such as pentylene group, 1,1-cyclohexylene group, alicyclic hydrocarbon group such as 3,3,5-trimethyl-1,1-cyclohexylene group, 1-phenyl-1,1- Examples include alkylene groups such as ethylene group and diphenylmethylene group. Of these, the 2,2-propylene group is even more preferably used. In the formula (2), it is particularly preferable that Ar ^{3 to} Ar ⁶ are all p-
It is a phenylene group, and X is a 2,2-propylene group. Further, in the formula (3), preferable Ar ⁷ , Ar ⁸
Is an arylene group having 6 to 12 carbon atoms, and an arylene group having 6 to 10 carbon atoms is more preferable. Specifically, m-phenylene group, p-phenylene group, dimethyl-p-
Examples thereof include a phenylene group, a tetramethyl-p-phenylene group, a naphthylene group, and a biphenylene group. Of these, a p-phenylene group is more preferably used for both Ar ⁷ and Ar ⁸ . Also, preferred Ar ⁹ has 6 carbon atoms.
To 12 arylene groups, and more preferably 6 to 10 carbon arylene groups. Specific examples include an m-phenylene group, a p-phenylene group, a naphthylene group, a biphenylene group, and the like. Among these, a p-phenylene group and a biphenylene group are even more preferable. In the formula (3), it is particularly preferable that Ar ⁷ , Ar ⁸ and Ar ⁹ are all p
A phenylene group.

As the aromatic polyether sulfone used in the present invention, a composition or a copolymer composed of one or more repeating units represented by the above formulas (1) to (3) can also be preferably used. . For example, in the case of a copolymer, an aromatic polyether sulfone including a repeating unit of the formula (1) and a repeating unit of the formula (2), an aromatic polyether sulfone including a repeating unit of the formula (1) and a repeating unit of the formula (3). Ether sulfone is preferably used. In that case,
The ratio of the repeating unit of the formula (1) and the repeating unit of the formula (2), or the ratio of the repeating unit of the formula (1) and the repeating unit of the formula (3), that is, the copolymerization composition ratio (1) / (2),
(1) / (3) may be determined in view of the solubility, heat resistance, and physical properties of the formed film of the aromatic polyether sulfone to be obtained and is not particularly limited, but the repeating unit of the formula (1) is Aromatic polyether sulfones containing 0.1 to 99.9 mol%, preferably 1 to 99 mol% are preferred.

Among the above-mentioned aromatic polyether sulfones, in terms of availability, heat resistance and solubility,
The following types are more preferable. That is, (i) A
The repeating unit of the formula (1) in which both r ¹ and Ar ² are p-phenylene groups is 70 to 90 mol%, and Ar is
^A copolymer in which ^{7 to} Ar ⁹ are all p-phenylene groups and the repeating unit of the formula (3) is 30 to 10 mol%,
(Ii) Ar ^{3 to} Ar ⁶ are all p-phenylene groups,
A polymer essentially consisting of a repeating unit of the formula (2), wherein X is an isopropylidene group ((CH ₃ ) ₂ <C), and (i
ii) The repeating unit of the formula (2) in which Ar ^{3 to} Ar ⁶ are all p-phenylene groups and X is an isopropylidene group is 70 mol% or more, and both Ar ¹ and Ar ² are p.
-A copolymer in which the repeating unit of the formula (1) which is a phenylene group is 30 mol% or less.

The above-mentioned aromatic polyether sulfone can be polymerized by a known method. For example, it can be obtained by polycondensing a monomer having a hydroxyl group and a halogen group at the terminals in the presence of an alkali metal carbonate in an aprotic polar solvent.

The molecular weight of the aromatic polyether sulfone used in the present invention is 0.1-10 dL / g, preferably 0.3-5.
It is in the range of 0 dL / g. However, these viscosities are values measured at 30 ° C. in a 0.5 g / dL dioxolane solution. If it is less than 0.1 dL / g, a durable film cannot be obtained, and if it exceeds 10 dL / g, the polymer is difficult to obtain and the solubility is lowered, which is not preferable.

The solvent system in the present invention comprises a solvent mainly containing 1,3-dioxolane, water and / or a carbon number of 1.
~ 6 aliphatic alcohols. According to the present invention,
As a solvent constituting the aromatic polyether sulfone solution composition, aromatic polyether sulfone is dissolved in a high concentration, and is compatible with water or an aliphatic alcohol having 1 to 6 carbon atoms described later, and Is a low boiling point solvent,
It was previously found that 1,3-dioxolane is excellent from the viewpoint of solubility, solution stability, and film-forming property. In the present invention, the solvent containing 1,3-dioxolane as a main component is 1,
It is preferable that 3-dioxolane is contained in an amount of 60% by weight or more, preferably 70% by weight or more based on the whole solvent.
More preferably, it is 100% by weight of dioxolane.
When other solvent is used, it is not particularly limited and may be used in consideration of the effect. The effects here include mixing the solvent in a range that does not sacrifice solubility or stability, for example, improving the surface property of the film formed by the solution casting method (leveling effect), evaporation rate or system It has the effects of adjusting viscosity and suppressing crystallization. The kind and the addition amount of the solvent to be mixed may be determined depending on the degree of these effects, and one kind or two or more kinds may be used as the solvent to be mixed.
Other solvents preferably used include 1,4-dioxane, cyclic ether solvents such as tetrahydrofuran, hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone and cyclohexanone, ethyl acetate, butyl acetate and the like. And an ester solvent such as ethylene glycol dimethyl ether and methoxyethyl acetate, and a halogen solvent such as methylene chloride, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane and chlorobenzene.

The amount of solvent is 99 to 90 of the total amount of the above solvent system.
%, Preferably 99 to 92% by weight, more preferably 98.5 to 95% by weight.

According to the present invention, when a solution composition in which an aromatic polyether sulfone is dissolved contains a small amount of water and / or an aliphatic alcohol having 1 to 6 carbon atoms, surprisingly, peeling from the supporting substrate occurs. It has been found that the sex is significantly improved.

The alcohol has 1 to 1 carbon atoms.
6, preferably 1 to 4, more preferably 2 to 4 linear or branched aliphatic alcohols are preferred. Specifically, methanol, ethanol, isopropanol,
Examples include tertiary butanol. Of these, ethanol, isopropanol, and tert-butanol are preferable because they have substantially the same effects as water. Although the reason is not clear, it is presumed that it is related to the boiling point of the solvent, that is, the ease of flight during drying. Further, higher alcohols having more than 6 carbon atoms are not preferable because they have a high boiling point and tend to remain after the film formation.

Water or an aliphatic alcohol having 1 to 6 carbon atoms may be added alone, or two or more kinds may be used in combination without any problem.

The content of water and alcohol must be carefully selected. These have poor solubility in aromatic polyether sulfones and are poor solvents. Therefore, it cannot be used in a large amount, and should be the minimum amount that gives a satisfactory peeling property. Generally, 1 to 10 based on the total amount of the solvent system, that is, the total amount of the solvent mainly containing 1,3-dioxolane and water and / or the alcohol.
%, Preferably 1 to 8% by weight, more preferably 1.5 to 5% by weight. If the content exceeds 10% by weight, the solubility of the solvent in the polymer and the stability of the dope are deteriorated, and if it is less than 1% by weight, the effect of improving the peelability becomes poor.

By adding a small amount of water and / or alcohol, another preferable effect other than the effect of improving the peelability of the cast film can be obtained. It has the effect of promoting the precipitation of cyclic oligomers of aromatic polyether sulfone from the solution composition.

Some of the aromatic polyether sulfones used in the present invention contain a small amount of a crystalline cyclic oligomer which is an impurity generated during polymerization. Examples of the cyclic oligomer include the following compounds (abbreviated as cyclic oligomer A).

[0026]

Embedded image

Such a compound gradually precipitates from the dope after dissolving the polymer. Of course, there is basically no problem because it is used after being filtered by a filter during the liquid transfer from the dope storage tank to the film-forming head, as is usually adopted industrially. However, after filtration, crystals often precipitate in the portion where the dope is likely to stay, impairing the transparency of the film. As a countermeasure against this, it has been proposed that the storage stability of the dope can be increased by sufficiently precipitating and crystallizing the cyclic oligomer in the dope over a long period of time, and then filtering the dope (Japanese Patent Application Laid-Open No. 05-329857). ). Therefore, it is important industrially to precipitate most of the cyclic oligomer as soon as possible after the dope preparation. The solution composition containing a small amount of water and / or alcohol according to the present invention has a higher precipitation rate of the cyclic oligomer than the solution composition containing no solution. As a result, after dissolution of the polymer, as compared with a dope obtained by filtering out crystals precipitated after a certain period of time, the solution composition of the present invention has a slower clouding rate due to crystal precipitation of oligomers, and a dope with higher storage stability. Become.

The solution composition of the present invention may be prepared by any method that results in a clear solution with low haze. A predetermined amount of water and / or the alcohol may be added to an aromatic polyether sulfone solution previously dissolved in a solvent, or the aromatic polyether sulfone may be dissolved in a solvent containing water and / or the alcohol. Good. However, as mentioned above, since water and alcohol are poor solvents for aromatic polyether sulfone,
The former method may cause clouding of the dope due to polymer precipitation, and the latter method is preferable.

The solution concentration of the aromatic polyether sulfone in the present invention depends on the molecular weight of the aromatic polyether sulfone, but the total amount of the solvent system is 15 to 90 parts by weight with respect to 10 parts by weight of the aromatic polyether sulfone, It is preferably 20 to 50 parts by weight. If the total amount of the solvent system exceeds 90 parts by weight, the stability of the solution will not be a problem, but it is not preferable because the effective concentration of the aromatic polyether sulfone is low, and the solution composition is used to form a film by the solution casting method. if you did this,
Since the solution viscosity is low, external disturbance is likely to occur and surface smoothness cannot be obtained, which is not preferable. Conversely, if the total amount of the solvent system is less than 15 parts by weight, it is difficult to obtain a stable dope. These concentrations are determined mainly by considering the stability of the dope and the solution viscosity.

In the present invention, the above-mentioned aromatic polyether sulfone solution composition (dope) is cast on a supporting substrate and then heated to evaporate the solvent to obtain a film. The industrial continuous film forming step generally comprises three steps of a casting step, a pre-drying step and a post-drying step. The casting step is a step of smoothly casting the dope, the pre-drying step is a step of evaporating and removing most of the solvent from the cast dope, and the post-drying step is a step of removing the remaining solvent.

In the casting process, a method of extruding from a die, a method of using a doctor blade, a method of using a reverse roll coater, etc. are used. Industrially, the most common method is to continuously extrude the dope from a die onto a belt-shaped or drum-shaped supporting substrate. Examples of the supporting substrate used include a glass substrate, a metal substrate such as stainless steel or a ferro type, and a plastic substrate such as polyethylene terephthalate. The material and surface condition of the supporting substrate also greatly affect the releasability of the cast film. For example, a substrate coated with Teflon or the like having an extremely low surface tension has good releasability. However, in order to industrially continuously form a film having a highly surface property and excellent optical homogeneity, a metal substrate having a mirror-finished surface is most commonly used, and the present invention is such a metal substrate. The effect is recognized.

In general, the solution viscosity is a very important factor in forming a transparent and smooth film from a dope. Although the solution viscosity depends on the concentration of the polymer, the molecular weight and the kind of the solvent, the viscosity of the solution composition of the present invention is 500
~ 50,000 cps, preferably 700 to 30,000
It is 0 cps. If it exceeds this range, the fluidity of the solution is lowered and a smooth film may not be obtained, which is not preferable. On the other hand, if it is less than that, the fluidity is too high, the dope cannot be uniformly discharged from the T die used for normal casting, and the surface may be disturbed due to external disturbance, so that a uniform and smooth film may not be obtained. . The effect of adding water or alcohol on the viscosity of the solution is slight because the amount added may be minute.

The temperature at the time of casting the above solution composition depends on the solvent used, but is in the range of 10 to 60 ° C, preferably 15 to 40 ° C. In order to obtain a film having excellent smoothness, the solution extruded from the die needs to be cast and smoothed on the supporting substrate. At this time, if the casting temperature is too high, the surface may be dried and solidified before it becomes smooth, which is not preferable. On the other hand, if the temperature is too low, the casting solution is cooled to increase the viscosity, which may cause difficulty in obtaining smoothness and may cause dew condensation, which is not preferable.

Before transferring from the casting process to the drying process, it is possible to highly smooth the surface properties of the film (leveling effect) by suppressing the drying for a certain period of time and ensuring the fluidity of the dope. .

In the pre-drying step, it is necessary to evaporate and remove most of the solvent from the dope cast on the supporting substrate in the shortest possible time. However, the drying conditions should be chosen carefully, as they undergo deformation due to foaming when rapid evaporation occurs. In the present invention, it is preferable to start the drying from the lowest boiling point of the solvents used, preferably from the range having the (boiling point-5 ° C) as the upper limit. After that, the temperature should be raised sequentially or continuously to improve the drying efficiency. The upper limit of the temperature at the final stage of this process is 1
20 ° C., preferably 100 ° C. is adopted. In this step, when the amount of residual solvent is large, 25% by weight is contained, and further higher temperature causes foaming, which is not preferable. Moreover, you may blow air as needed. In that case, the wind speed is generally 20 m / sec or less, preferably 15 m / sec.
A range of seconds or less is used. If it exceeds this, a smooth surface cannot be obtained due to wind disturbance, which is not preferable. The wind speed may be increased stepwise or continuously and is rather preferable. In the early stages, there may be no wind to avoid wind turbulence.

In this pre-drying step, the film is on the substrate and is peeled off from the substrate at the end of the step. At that time, deformation occurs because the film is soft when the amount of residual solvent is large, and when the residual solvent is small, even the cast film cast from the solution composition of the present invention has high adhesion to the supporting substrate and releasability. Deteriorates, resulting in stress strain, peeling streaks, and peeling scratches. Therefore, the residual solvent amount is an important factor, and the range of the residual solvent amount is preferably 5 to 25% by weight, and more preferably 7 to 20% by weight. In the solution casting method using a metal substrate, generally, the peelability is good at the beginning of film formation, but the peelability often decreases as the peeling is repeated. The cause of this is not clear, but gradually many metal atoms with high surface tension are exposed on the surface of the substrate, or a trace amount of polymer adheres to the surface, and it begins to act like an adhesive layer. Is estimated. As a countermeasure for this, the peelability can be recovered by periodically cleaning the substrate surface, for example, by wiping the substrate surface with water.
In an industrial continuous film forming process, it is extremely troublesome work and is not efficient. According to the present invention, the releasability of the cast film from the supporting substrate can be favorably maintained without performing such an operation.

In the post-drying step, the film peeled from the substrate is further dried so that the residual solvent amount is 3% by weight or less,
It should be preferably 1% by weight or less, more preferably 0.5% by weight or less. If there is a lot of residual solvent, deformation occurs over time, and if heat is applied in the post-processing step, dimensional change
This is because so-called heat shrinkage occurs. Generally, in the post-drying step, industrially, a method of drying while transporting the film by a pin tenter method, a roll suspension method, or the like is adopted, but in these methods, various forces are applied to the film during the drying. Therefore, it is desirable to select the drying temperature from the range in which the film is not deformed in the production of a film which is required to have a high optical homogeneity such as a liquid crystal display device.
Generally, when the glass transition temperature of the aromatic polyether sulfone used is Tg (° C), (Tg-120 ° C)
To Tg, preferably (Tg-100 ° C) to (Tg
The range of −10 ° C.) is selected. If Tg is exceeded, thermal deformation of the film may occur, which is not preferable, and (Tg-1
If it is lower than 20 ° C., the drying speed will be remarkably slow, which is not preferable. Thermal deformation becomes less likely to occur as the residual solvent decreases. Therefore, it is preferable to adopt a method in which the temperature is initially low within the range, and then the temperature is raised stepwise or continuously. In this post-drying step, air may be blown as in the pre-drying step. The film transport speed is not particularly limited, but generally 0.5 to 15 m / min, preferably 1 to 1
It is performed in the range of 0 m / min.

In the present invention, the aromatic polyether sulfone film may be produced in an air atmosphere or may be dried in an atmosphere of an inert gas such as nitrogen gas or carbon dioxide gas. Good. When a flammable solvent such as 1,3-dioxolane is used, since the solvent gas concentration is high due to evaporation, a drying method in an inert gas atmosphere is recommended from the viewpoint of safety considering the explosion limit of the solvent. preferable. In this case, the gas concentration of the solvent is preferably 3 vol% or more. The oxygen concentration in the inert gas atmosphere is 10 vol.
% Or less is desirable.

The thickness of the film obtained according to the present invention is in the range of 10 to 300 μm, preferably 50 to 200 μm. In particular, the plastic substrate constituting the liquid crystal display device and the original film for the retardation film have a film thickness of 50 to 200.
The thickness of μm is preferably used. If it is thicker than this, it is difficult to remove the residual solvent, and if it is thinner than this, it is difficult to suppress thickness unevenness.

[0040]

According to the present invention, a small amount of water and / or lower aliphatic alcohol is contained in an aromatic polyether sulfone solution composition containing a solvent mainly composed of 1,3-dioxolane, to thereby form a solution. In the casting method, the peelability of the casting film from the supporting substrate can be improved. Therefore, it is very advantageous for continuously producing a transparent and smooth aromatic polyether sulfone film.

Further, by containing a small amount of water and / or the above alcohol, the cyclic oligomer, which is an impurity in such a solution composition, can be precipitated in a short time and removed by filtration, so that the stability for long-term storage is improved. A high dope can be obtained.

The obtained film has good surface properties without peeling scratches and peeling streaks, has a small retardation, has optical isotropy and homogeneity with little variation in retardation and slow axis, and has a liquid crystal display. It is useful as an optical film used for the above, especially a retardation film, a plastic substrate and the like.

[0043]

EXAMPLES The present invention will be described in detail below with reference to examples. However, the present invention is not limited to this. The measurement items performed in the examples were measured by the following methods.

Solution viscosity: B type viscometer B manufactured by Tokyo Keiki Co., Ltd.
It was measured at 30 ° C. using a H type. Glass transition temperature: 29 manufactured by TA Instruments
The temperature rising rate was measured at 20 ° C./min using a 20 type DSC. Film thickness: A stylus type film thickness meter manufactured by Anritsu Corporation was used. Light transmittance: Shimadzu Corporation UV-visible spectroscope (UV
-240) was used. Haze value: An automatic digital haze meter-UDH-20D manufactured by Nippon Denshoku Industries Co., Ltd. was used. Phase difference and slow axis: Automatic birefringence meter KOBURA-21
ADH (made by KS Systems Co., Ltd.) was used. Quantification of residual solvent: The solvent was heated at 200 ° C. for 16 hours in a nitrogen atmosphere, and the weight was measured before and after the heating.

Example 1 With respect to 30 parts by weight of a 1,3-dioxolane solvent containing 2% by weight of water, Ar ^{3 to} Ar ⁶ in the above formula (2) are all p-phenylene groups, and X
Aromatic polyether sulfone [ηsp / c = 0.50] which is mainly composed of repeating units in which is a 2,2-propylene group.
dL / g (0.5 g / dL in dioxolane, 30 ° C.),
10 parts by weight of glass transition point = 193 ° C.] were dissolved with stirring at 50 ° C. to obtain a transparent and viscous dope. The solution viscosity of this dope at 30 ° C. is 3.5 × 10 ³ cp
It was s. When this dope was left in a closed container at 50 ° C. overnight, the dope became cloudy due to precipitation of cyclic oligomer A. The crystals were filtered using a filter having a pore size of 5 μm, and the dope was cast on a ferrotype substrate using a doctor blade. This substrate is a new ferrotype plate thoroughly washed and dried. 10 at 65 ° C
Min, the film was peeled off from the substrate after heating and drying at 90 ° C. for 10 minutes. The peelability was extremely good, and peeling scratches and peeling streaks were not found on the film surface. The residual solvent amount in the film at the time of peeling was 15.9% and the film thickness was 110.
μm. Repeat the film formation by the same operation using the same substrate, to evaluate the peelability by examining the number of peelable without peeling scratches, peeling streaks, etc. on the surface of each film obtained, in this case Subsequently, the film formation was repeated 5 times, and the releasability of each film from the substrate was unchanged and was good.

Example 2 Example 1 was applied to 30 parts by weight of a 1,3-dioxolane solvent containing 3% by weight of ethanol.
50 parts by weight of the aromatic polyether sulfone used in
It melt | dissolved, stirring at 0 degreeC, and the transparent and viscous dope was obtained. The solution viscosity of this dope at 30 ° C. is 2.7 ×
It was 10 ³ cps. The film was formed after filtration in the same manner as in Example 1, and the peelability was examined. The film formation was repeated 6 times, and the peelability of the film was good in all cases.

Example 3 2% by weight of isopropanol
10 parts by weight of the aromatic polyether sulfone used in Example 1 was dissolved in 30 parts by weight of a mixed solvent of 1,3-dioxolane and isopropanol containing 50 parts by stirring to obtain a transparent and viscous dope. It was 30 of this dope
The solution viscosity at 0 ° C. was 3.0 × 10 ³ cps.
Similar to Example 1, the film was formed after filtration and the peelability was examined.
The film was repeatedly peeled repeatedly, and the peelability of the film was good.

Comparative Example 1 10 parts by weight of the aromatic polyether sulfone used in Example 1 was dissolved in 30 parts by weight of 1,3-dioxolane while stirring at 50 ° C. to give a transparent, viscous dope. Got The solution viscosity of this dope at 30 ° C. was 3.2 × 10 ³ cps. Example 1
When the film was formed after filtration in the same manner as described above and the peeling property of the film was examined, the peeling property was good up to the second time, but the peeling strength increased from the third time, and many peeling lines were found on the film surface. It was

[Comparative Example 2] 1,3 containing 0.5% by weight of water
10 parts by weight of the aromatic polyether sulfone used in Example 1 was dissolved in 30 parts by weight of the dioxolane solvent while stirring at 50 ° C. to obtain a transparent and viscous dope.
The solution viscosity of this dope at 30 ° C. was 3.1 × 10 ^3.
It was cps. When the film was formed after filtration in the same manner as in Example 1 and the peelability was examined, the peelability was good up to the second time, but the peel strength increased from the third time, and a large number of peeling lines were observed on the film surface. Was given.

Comparative Example 3 Example 1 was applied to 30 parts by weight of a 1,3-dioxolane solvent containing 12% by weight of ethanol.
50 parts by weight of the aromatic polyether sulfone used in
It was dissolved with stirring at ℃, but the solubility was poor and only a cloudy dope was obtained.

Example 4 With respect to 25 parts by weight of a 1,3-dioxolane solvent containing 3% by weight of water, a repeating unit in which both Ar ¹ and Ar ² in the above formula (1) are p-phenylene groups was used. 24 mol%, Ar ^{3 to} Ar ⁶ in the above formula (2)
Are both p-phenylene groups and X is a 2,2-propylene group, and the aromatic polyether sulfone [ηsp / c = 0.42 dL / g] is composed of 76 mol% of repeating units.
(0.5 g / dL dioxolane, 30 ° C.), glass transition point = 196 ° C.] 10 parts by weight were dissolved with stirring at 50 ° C. to obtain a transparent and viscous dope. The solution viscosity of this dope at 30 ° C. was 3.4 × 10 ³ cps. When this dope was allowed to stand overnight at 50 ° C. in a closed container, the dope became cloudy due to the precipitation of cyclic oligomer A, but the amount of the precipitate was not so large as in Example 1. The crystals were filtered using a filter having a pore size of 5 μm, and the dope was cast on a ferrotype substrate using a doctor blade. This substrate is a new ferrotype plate thoroughly washed and dried.
Subsequently, the film was peeled from the substrate by heating and drying at 65 ° C. for 10 minutes and 90 ° C. for 10 minutes. The peelability was extremely good, and peeling scratches and peeling streaks were not found on the film surface. The amount of residual solvent in the film at the time of peeling was 1
The film thickness was 5.5% and the film thickness was 108 μm. The same operation was performed using the same substrate, and film formation was repeated 5 times, but the peelability of the film from the substrate did not change and was good.

Comparative Example 4 10 parts by weight of the aromatic polyether sulfone used in Example 4 was dissolved in 25 parts by weight of 1,3-dioxolane while stirring at 50 ° C. to give a transparent, viscous dope. Got The solution viscosity of this dope at 30 ° C. was 3.3 × 10 ³ cps. Example 4
When the film was formed after filtration in the same manner as described above and the peeling property of the film was examined, the peeling property was good up to the second time, but the peeling strength increased from the third time, and many peeling lines were observed on the film surface. .

Example 5 With respect to 23 parts by weight of a 1,3-dioxolane solvent containing 3% by weight of water, a repeating unit in which both Ar ¹ and Ar ² in the above formula (1) are p-phenylene groups was used. Aromatic polyether sulfone [η] having 78 mol% and 22 mol% of repeating units in which Ar ⁷ Ar ⁸ and Ar ⁹ in the formula (3) are all p-phenylene groups.
10 parts by weight of sp / c = 033 dL / g (in 0.5 g / dL dioxolane, 30 ° C., glass transition point = 223 ° C.) were dissolved with stirring at 50 ° C. to obtain a transparent and viscous dope. . The solution viscosity of this dope at 30 ° C. is 2.
It was 9 × 10 ³ cps. No change was observed in this dope even if it was left in a sealed state at room temperature for 1 week. Pore diameter 5μ
After filtering with a m filter, the dope was cast on a ferrotype substrate using a doctor blade. This substrate is a new ferrotype plate thoroughly washed and dried. Subsequently, the film was peeled from the substrate by heating and drying at 65 ° C. for 10 minutes and 90 ° C. for 10 minutes. The peelability was extremely good, and peeling scratches and peeling streaks were not found on the film surface. The amount of residual solvent in the film at the time of peeling was 15.4%, and the film thickness was 108 μm. The same operation was performed using the same substrate, and the film formation was repeated 5 more times. The peelability did not change and all were good.

COMPARATIVE EXAMPLE 5 10 parts by weight of the aromatic polyether sulfone used in Example 5 was dissolved in 23 parts by weight of 1,3-dioxolane while stirring at 50 ° C. to give a transparent and viscous dope. Got The solution viscosity of this dope at 30 ° C. was 2.8 × 10 ³ cps.

When the film was formed after filtration in the same manner as in Example 5 and the releasability was examined, the releasability was good at the first time, but the peel strength increased from the second time, and a large number of peeling lines were formed on the film surface. I was seen.

The results of Examples 1 to 5 and Comparative Examples 1 to 5 are summarized in Table 1. Here, the number of times of peeling refers to the upper limit of the number of times that the film can be smoothly peeled without peeling scratches or peeling streaks on the film surface. As is clear from Table 1, when appropriate amounts of water, ethanol and isopropanol were added, the releasability from the substrate was remarkably improved.

[0057]

[Table 1]

A: Aromatic polyether sulfone used in Example 1 (formula (2)) B: Aromatic polyether sulfone used in Example 4 (formula (1) / (2) = 24/76) ) C: Aromatic polyether sulfone used in Example 5 (the above formula (1) / (3) = 78/22))

Example 6, Comparative Example 6 Polymer, dope of Example 1 with the same concentration (containing 1% by weight of water
The crystal precipitation rate and the dope stability after filtration were compared between the 3-dioxolane solution (abbreviated as D below) and the dope of Comparative Example 1 (1,3-dioxolane solution, abbreviated as E below). Haze values measured by putting both dopes immediately after dissolution in a cell having an optical path length of 1 cm are 0.5% (D) and 0.3%.
It was (E). When this dope was stored at 50 ° C. for 18 hours, a white precipitate was deposited in both, but from the appearance, D was clearly larger in precipitation amount. These have a pore size of 0.
As a result of filtration using a 5 μm filter, the haze value of each filtrate was 0.1%. However, as a result of further leaving the filtrate at room temperature for 2 days, the haze value of the filtrate starting from the dope (E) was 34%, while the haze value of the filtrate starting from the dope (D) was 0. 1
%, And no change was observed.

[Example 7] The aromatic polyether sulfone solution used in Example 1 was used to carry out continuous film formation. The casting apparatus used was a system in which the dope was extruded from the die to the belt through a filtration process, and the belt was connected to a pre-drying furnace divided into four stages. The belt is made of a metal substrate whose surface is mirror-finished and has a length of 18 m. As the post-drying furnace, a roll-suspended furnace having 6 compartments was adopted. This length is 120 m. The belt conveyance speed was set to 1 m / min and the cast film width was set to 50 cm. After casting using this device, the temperature of the pre-drying furnace is gradually changed to 45 ° C. (no wind), 65 ° C. (wind speed 1 m / sec),
The temperature was raised to 90 ° C. (air velocity 5 m / sec), and finally 40 ° C. and cooled. Then, a self-supporting film having a residual solvent amount of 12% by weight was formed. At this stage, the film was peeled from the belt and then sent to a drying oven. At this time, the peelability of the cast film (a self-supporting film having a residual solvent amount of 12% by weight) from the belt was good.

In the post-drying furnace, 70 ° C., 110 ° C., 145
C., 165.degree. C., 175.degree. C., and 183.degree. The obtained film was excellent in surface property without peeling scratches and peeling streaks. The thickness was 100 ± 1.1 μm, which was extremely uniform. The amount of residual solvent in the film was extremely small at 0.3% by weight, and almost no added water remained. The glass transition point of this film was 185 ° C. Also 550n
The light transmittance at the wavelength of m was 89.2%, and the haze value was 0.3%, which was optically transparent. Wavelength 590nm
The retardation was less than 10 nm, and the variation within the film was small. Further, the variation of the slow axis (direction in which the refractive index becomes maximum in the film plane) was ± 10 ° or less, and the film was optically uniform. This continuous film forming test was conducted continuously for 16 hours, during which the peelability of the film from the belt remained good.

Comparative Example 7 A continuous film forming test was conducted using the aromatic polyether sulfone solution used in Comparative Example 1.
Film formation was carried out using the same equipment as in Example 7 under the same conditions, but the peel strength from the belt of the cast film increased from the time 1 hour after the start of casting the dope, and the peelability deteriorated. It was. Peeling scratches gradually on the finally dried film,
Peeling muscles became prominent.

Example 8 Continuous film formation was carried out using the aromatic polyether sulfone solution used in Example 5. The same film forming apparatus as in Example 9 was used. The belt conveyance speed was set to 1 m / min and the cast film width was set to 50 cm.
After casting using this device, the temperature of the pre-drying furnace is gradually changed to 45 ° C (no wind), 65 ° C (wind speed 1 m / sec), 90 ° C.
The temperature was raised to (wind speed of 5 m / sec), and finally 40 ° C. and cooled. Then, a self-supporting film having a residual solvent amount of 13% by weight was formed. At this stage, the film was peeled from the belt and then sent to a drying oven. At this time, the peelability of the cast film (the film having self-supporting property) from the belt is good, and the peelability is good. In the post-drying oven, 75 ° C, 110 ° C,
The temperature was raised stepwise at 140 ° C, 175 ° C, 190 ° C and 200 ° C to obtain a dry film. The obtained film was excellent in surface property without peeling scratches and peeling streaks. The thickness was 100 ± 1.4 μm, which was extremely uniform. The amount of residual solvent in the film was extremely small at 0.3% by weight, and almost no added water remained.
The glass transition point of this film was 216 ° C. The light transmittance at a wavelength of 550 nm was 88.2% and the haze value was 0.3%, which was optically transparent. Wavelength 5
The retardation at 90 nm was 10 nm or less, and the variation within the film was small. Also, the variation of the slow axis (direction in which the refractive index is maximum in the film plane) is ± 1.
The film was 0 ° or less and was an optically homogeneous film. This continuous film forming test was conducted continuously for 16 hours, during which the peelability of the film from the belt remained good.

[Comparative Example 8] A continuous film-forming test was conducted using the aromatic polyether sulfone solution used in Comparative Example 5.
Film formation was carried out using the same equipment as in Example 8 under the same conditions, but the peeling strength from the belt of the cast film increased from the time when 40 minutes had elapsed after starting the casting of the dope, and the peelability deteriorated. It was. Peeling scratches gradually on the finally dried film,
Peeling muscles became prominent.

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Claims (2)

[Claims] 1. Water and at least one linear or branched aliphatic alcohol having 1 to 6 carbon atoms in an amount of 1 to 10
%, And solvent 99 mainly composed of 1,3-dioxolane 99
An aromatic polyether sulfone solution composition comprising 15 to 90 parts by weight of a solvent system consisting of ˜90% by weight, and 10 parts by weight of aromatic polyether sulfone. 2. A method for producing an aromatic polyether sulfone film, which comprises casting the solution composition according to claim 1 on a supporting substrate and heating a casting film containing a solvent to evaporate the solvent. Method.