JP3443202B2 - Polyarylate-based resin solution composition and method for producing film - Google Patents

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 a polyarylate resin and a method for producing a polyarylate film obtained therefrom. More specifically, it is a solution composition (dope) composed of a non-halogen solvent that does not cause environmental pollution, and has a surface property, transparency, and optical homogeneity that are useful for optical applications such as display elements or electrical / electronic equipment applications. The present invention relates to a stable solution composition that gives an excellent polyarylate-based film with less residual solvent, 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 attracted attention because of their low power consumption and excellent image quality, and have made remarkable progress. In these liquid crystal display devices, polarizing plate, a protective layer, such as a phase difference plate and the electrode board is a polymer film is used. 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 device lighter and thinner.
In order to accurately transmit the transmitted polarized light to the liquid crystal layer, extremely high optical isotropy and homogeneity are required. Further, heat resistance is required to withstand heat applied during processing such as film formation of the transparent electrode and formation of an alignment film, and it is required that the glass transition point is 150 ° C. or higher. From this point of view, unstretched polycarbonate film, polyarylate film and the like are used, and particularly from the viewpoint of heat resistance, a film made of polyarylate is preferably used.

[0003] On the other hand, the phase difference film is intended to be used for Ru improve the visibility of an image in the STN type liquid crystal display device or a TN type liquid crystal display device, converts elliptically polarized light transmitted through the liquid crystal layer into a linearly polarized light Have a role to play. As these materials, uniaxially stretched polycarbonate films and polyvinyl alcohol films are mainly used. Recently, in order to further improve the image visibility, a retardation film having a wavelength dispersion of retardation matching that of a liquid crystal layer has been demanded, and a polyarylate film is mentioned as one candidate. This polyarylate 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 homogeneous oriented film. In order to obtain such an oriented film, it is necessary to use a film having a high optical isotropy at the stage of an unstretched film (raw film), and thus a high film forming technique is required.

Generally, a plastic film such as a polyarylate 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 tends 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 Trends of Electrode Substrate Film”] , Japan Society of Polymer Science, Polymer Electronics Workshop, p20
(November 11, 1993; at Sophia University)]. The surface properties and optical homogeneity required for films used in liquid crystal display devices are quite severe. For example, for a plastic substrate, a surface thickness unevenness of ± 5 μm or less, a phase difference of 10 nm or less, and an optical axis alignment of ± 10 ° or less are required. For a retardation film original film, a surface thickness unevenness of 2 μm or less, A phase difference of 30 nm or less and an optical axis alignment of ± 1 ° or less are required. Here, the optical axis orientation represents the direction in which the refractive index in the film plane is maximum, that is, the direction of the slow axis. In reality, it is difficult to meet such strict requirements by the melt extrusion method.

From this point of view, a solution casting method (casting method) has been conventionally used as a method for forming a polyarylate film. A high concentration solution (dope) is required to obtain a thick film having a thickness of about 100 μm by the solution casting method, but the solvent that can dissolve the polyarylate resin in a high concentration and can be applied to the film formation is limited. For example, polar solvents such as dimethylacetamide, dimethylformamide, pyridine, and N-methylpyrrolidone are good solvents, but have high boiling points or have strong interaction with polyarylate, and it is not easy to reduce the amount of residual solvent in the formed film. Therefore, it is not practical as a solvent for film formation. Halogen-based solvents such as dichloromethane and chloroform are also good solvents, and dichloromethane is actually put to practical use as a solvent for film formation.
However, since these halogen-based solvents are regarded as problematic in terms of their influence on environmental pollution and are suspected to be carcinogenic, there is a trend to suppress their use worldwide. Further, the halogen-based solvent has a problem that it reacts with moisture in the air to generate a corrosive gas represented by hydrogen chloride and corrodes the film forming apparatus. Furthermore, even if a trace amount remains in the film, an undesired corrosive compound is generated in the process of long-term use, so that there is a limitation in application to a display device or electric / electronic equipment field using a fine element. From these viewpoints, in recent years, development of a film forming technique using a non-halogen solvent has been desired.

[0006]

The object of the present invention is to obtain excellent surface properties, transparency and optical homogeneity by a solution casting method using a solvent other than a halogen-based solvent which may cause environmental pollution or corrosion. It is an object of the present invention to provide a solution composition which gives a polyarylate-based film and a method for producing a polyarylate-based film using the same.

[0007]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that (a) 1,3-dioxolane dissolves a polyarylate resin in a high concentration and meets a specific condition. Under the stability of the solution is excellent,
(A) The inventors have found that a transparent film having a high viscosity and a high optical homogeneity can be formed from the solution having a specific viscosity without causing cloudiness, and thus the present invention has been accomplished.

That is, according to the present invention, 15 to 90 parts by weight of a solvent containing 60% by weight or more of 1,3-dioxolane and capable of dissolving a polyarylate resin, and polyarylate resin 1
It is a polyarylate resin solution composition consisting of 0 parts by weight. Further, we have found that when a small amount of water and / or a lower aliphatic alcohol is added to the solution composition, the releasability of the cast film from the supporting substrate is remarkably improved during film formation. The present invention includes the above solution composition containing a small amount of this water and / or lower aliphatic alcohol.

In the present invention, (1) these solution compositions (dope) are cast on a supporting substrate, and (2) a cast film containing a solvent is heated to evaporate the solvent to produce a film. This is a method for producing a polyarylate-based film.
In such a manufacturing method, the semi-dried film in which the solvent is partially dried is peeled from the supporting substrate, and in a state capable of contracting in the width direction, the polyarylate-based film containing the solvent is adjusted to the transition of the glass transition point (Tg ′). It has also been found that heat treatment at a specific temperature produces a film that is optically highly isotropic and homogeneous. This heat treatment method is also included in the manufacturing method of the present invention.

The 1,3-dioxolane found in the present invention is a very excellent solvent for forming a polyarylate film, but it is a flammable solvent and has a possibility of producing peroxide by air oxidation. There is also. Therefore, it is preferable from the viewpoint of safety to perform the drying in an atmosphere of an inert gas such as nitrogen gas. The present invention also includes a method of drying in this inert gas atmosphere.

The means for drying in the drying step is as follows:
There are hot air heating, electric heating, infrared heating, etc., but microwave heating has also been found. Microwave heating is based on shaking a dipole contained in a body to be heated by microwaves, and is a so-called microwave oven. This is not necessarily effective for general organic substances other than water, but the present inventors have focused on the property unique to 1,3-dioxolane that it is structurally asymmetric and applied to film drying in the present invention. As a result, they have surprisingly found that they can be dried very efficiently, and that a homogeneous film having no foaming or citron skin can be obtained. The microwave heating drying method based on this finding is also included in the drying means of the drying step in the present invention.

The present invention will be described in detail below.

The polyarylate resin used in the present invention is a polymer mainly composed of a polyester of a bisphenol component and an aromatic dicarboxylic acid component.
As such a polyarylate-based resin, a resin containing a repeating unit represented by the following formula (II) in an amount of 50 mol% or more, preferably 75 mol% or more, and particularly preferably 100 mol% based on the whole is a transparent film of the obtained film. It has good properties and is preferable.

[0014]

[Chemical 1]

[In the formula (II), Ar represents an aromatic hydrocarbon group having 6 to 12 carbon atoms, and X represents a divalent hydrocarbon group having 1 to 15 carbon atoms, a sulfone group or a sulfide group. It is at least one group selected. R ^{1 to} R ⁴ are the same or different and each is hydrogen, halogen, or a hydrocarbon group having 1 to 5 carbon atoms. ]

In the above formula (II), Ar is preferably an aromatic hydrocarbon group having 6 to 10 carbon atoms, specifically m-.
Examples thereof include a phenylene group, a p-phenylene group and a naphthylene group, and particularly preferred are an m-phenylene group and a p-phenylene group.

X is a divalent hydrocarbon group having 1 to 15 carbon atoms,
It is at least one group selected from the group consisting of a sulfone group and a sulfide group, and more specifically, a divalent aliphatic hydrocarbon group having 1 to 15 carbon atoms, an alicyclic hydrocarbon group, an alkylene group, a sulfone group, and It is selected from the group consisting of sulfide groups. A divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group, and an alkylene group are preferred. Specifically, methylene group, 1,1-ethylene group, 2,2-propylene group, 2,2-butylene group, 4-
Aliphatic hydrocarbon group such as methyl-2,2-pentylene group, 1,1-cyclohexylene group, alicyclic hydrocarbon group such as 3,3,5-trimethyl-1,1-cyclohexylene group, 1- Examples thereof include an alkylene group such as a phenyl-1,1-ethylene group, a diphenylmethylene group, and a 1,1-fluorene group.

R ^{1 to} R ⁴ are the same or different and each is hydrogen, halogen, or a hydrocarbon group having 1 to 5 carbon atoms. Specific examples thereof include hydrogen, bromine, and methyl group.

Among these polyarylate resins, solubility in 1,3-dioxolane which is the main solvent of the present invention, stability of dope, availability of raw materials, physical properties of the obtained polymer, etc. Therefore, R ^{1 to} R ⁴ are the same or different and each is hydrogen or a methyl group, and X is a carbon number of 1 to 1.
It is a 0-valent divalent aliphatic hydrocarbon group or alicyclic hydrocarbon group, and Ar is preferably a combination of an m-phenylene group and a p-phenylene group. For example, ^one of R ¹ and R ² in the above formula (II) is a methyl group, and R ³
And one of R ⁴ is a methyl group and Ar is m
Examples thereof include a repeating unit represented by the following formula (III), which is a -phenylene group and / or a p-phenylene group. (R ² , R ⁴ , and X are the same as those listed above)

[0020]

[Chemical 2]

X in the above formula (II) is 1,1-
Cyclohexylene group, 3,3,5-trimethyl-1,1
An alicyclic hydrocarbon group such as a cyclohexylene group,
Preferable examples are also those in which R ^{1 to} R ⁴ are all hydrogen, and Ar is an m-phenylene group and / or p-phenylene group, for example, a repeating unit represented by the following formula (IV).

[0022]

[Chemical 3]

Of course, the polyarylate resin in the present invention may be a copolymer or mixture of one or two or more repeating units represented by the above formula (II). Specifically, for example, it may be a copolymer containing two or more different bisphenol components. In particular, the use of the copolymer often improves the solubility of the polymer in the solvent or the stability of the dope, and is suitable for use in the solution casting method of the present invention. In this case, the content of either one of the two types of repeating units represented by the above formulas (III) and (IV) as a preferable structure is preferably 10 to 99 mol%, more preferably 30 to 99 mol%. Examples of the copolymer include mol%. In this case, as the remaining components constituting the copolymer, R ^{1 to} R ⁴ are all hydrogen, X is a 2,2-propylene group, and Ar is an m-phenylene group and / or p-phenylene group. A repeating unit which is a group is preferred.

Further, the above polyarylate resin contains 50 mol% or less of a repeating unit represented by the following formula (V),
The polyester carbonate may preferably be contained in an amount of 25 mol% or less.

[0025]

[Chemical 4]

[In the formula (V), Y has the same meaning as X in the formula (II). R ^{5 to} R ⁸ are the same or different and each is hydrogen, halogen, or a hydrocarbon group having 1 to 5 carbon atoms. ]

In the above formula (V), Y is the above formula (II).
It has the same meaning as X in the above, and is preferably selected from the group consisting of a divalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group, and an alkylene group. Specifically, methylene group, 1,1-ethylene group, 2,2-propylene group, 2,
2-butylene group, aliphatic hydrocarbon group such as 4-methyl-2,2-pentylene group, 1,1-cyclohexylene group,
Alicyclic hydrocarbon groups such as 3,3,5-trimethyl-1,1-cyclohexylene group, alalkylene groups such as 1-phenyl-1,1-ethylene group, diphenylmethylene group and 1,1-fluorenylene group Can be illustrated.

R ^{5 to} R ⁸ are the same or different and are hydrogen, halogen or a hydrocarbon group having 1 to 5 carbon atoms, preferably hydrogen, bromine or methyl group.

The polyarylate resin used in the present invention is
It may be a copolymer composed of repeating units represented by the formula (II) and the formula (V), or may be a mixture.

The above polyarylate resin is usually synthesized by a known method such as interfacial polycondensation, melt polycondensation or solution polycondensation, but the above polyarylate resin in which an aromatic group of the main chain is bound by an ester bond. Is preferably one obtained by interfacial polycondensation in that the obtained polymer is less colored. For example, bisphenols dissolved in an alkaline aqueous solution and aromatic dicarboxylic acid dichlorides dissolved in methylene chloride can be contacted in the presence of an interfacial transfer catalyst to perform polymerization. Also, the above formula (II)
A copolymer comprising the repeating units represented by and (V) can be obtained by this interfacial polycondensation method, and each polymer comprising the repeating units represented by the formulas (II) and (V) It is also possible to obtain a desired polyarylate-based resin by melt-kneading.

The molecular weight of the polyarylate resin used in the present invention is 10,000 or more and 100,000 or less, preferably 15,000 or more and 70,000 or less in terms of polystyrene equivalent number average molecular weight measured by GPC. When the molecular weight is less than 10,000, a strong film cannot be obtained, and when it exceeds 100,000, it is not preferable because it is difficult to obtain a polymer and the solubility is lowered.

By the way, 1,3-dioxolane, which is a cyclic ether-based solvent, has high concentration solubility, dope stability,
From the viewpoint of boiling point (76 ° C.) and film forming property, it is a very excellent solvent for use in the solution casting method of polyarylate resin. Tetrahydrafuran, which is the same cyclic ether solvent,
1,4-dioxane is also a good solvent from the viewpoint of solubility, but tetrahydrofuran is 1,3 from the viewpoint of solution stability.
-It is inferior to dioxolane, and since 1,4-dioxane has a high boiling point (100 ° C), it is difficult to remove the solvent from the film, and since it has carcinogenicity, it is not suitable for industrial use.

According to the present invention, the above polyarylate resin is cast by a casting method using a polyarylate resin solution composition prepared by dissolving the polyarylate resin in a solvent mainly containing 1,3-dioxolane.

The solvent used in the present invention includes
A solvent containing 1,3-dioxolane in an amount of 60% by weight or more, preferably 70% by weight or more based on the total amount of solvent, and a single solvent, that is, 100% by weight of 1,3-dioxolane is more preferable. The other solvent that can be used at 40% by weight or less 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 of the solvent to be mixed and the amount to be added may be determined according to the degree of these effects.
One kind or two or more kinds may be used. Suitable solvents 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, esters such as ethyl acetate and butyl acetate. Examples of the solvent include ether solvents such as ethylene glycol dimethyl ether and methoxyethyl acetate.

According to the present invention, by adding a small amount of water and / or an aliphatic alcohol having 1 to 6 carbon atoms to the above solution composition, the releasability from the supporting substrate is remarkably improved. I understood it.

That is, the present invention also comprises a solvent (a) containing 60% by weight or more of 1,3-dioxolane and capable of dissolving a polyarylate resin, water or a linear or branched chain having 1 to 6 carbon atoms. A polyarylate-based resin solution composition comprising at least one type of aliphatic alcohol (b) and a polyarylate-based resin, wherein the polyarylate-based resin is 15 to 90 parts by weight of the solvent (a). A solvent containing 10 parts by weight of water and at least one kind (b) of a straight chain or branched chain aliphatic alcohol having 1 to 6 carbon atoms, the solvent consisting of the above solvents (a) and (b). The polyarylate resin solution composition is characterized by being 1 to 10% by weight of the whole system.

In an industrial continuous film forming process, a metal plate having a mirror-finished surface is generally used as a supporting substrate. When a film in a semi-dried state dried on the substrate after dope casting is peeled from the substrate, the film is formed. At the beginning, the peelability is good, but as the peeling is repeated, the adhesiveness between the film and the metal substrate gradually increases and the peelability often deteriorates.
Since the peel strength is high, peel streaks and peel scratches may be formed on the film, or the film may be stretched and whitened at a part thereof. The cause is not clear, but gradually many metal atoms with high surface tension are exposed on the substrate surface.
Alternatively, it is presumed that a very small amount of polymer adheres to the surface and begins to work like an adhesive layer. As a countermeasure against this, if the substrate surface is regularly washed, for example, by wiping the substrate surface with water, the releasability can be recovered, but this is a very troublesome work in an industrial continuous film forming process and is not efficient. According to the present invention, the film can be repeatedly peeled from the substrate, and the productivity is remarkably improved.

As the solvent (a) and the polyarylate resin in the present invention, the same ones as described above can be used.

The alcohol (b) used in the present invention is preferably a chain or branched aliphatic alcohol having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, more preferably 2 to 4 carbon atoms. Specific examples include methanol, ethanol, isopropanol, tertiary butanol and the like.
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 are likely to remain after film formation.

Water or the above aliphatic alcohols having 1 to 6 carbon atoms may be used alone or in combination of two or more kinds without any problem.

The content of water and alcohol must be carefully selected. These are completely poor solvents for polyarylate resins and are completely poor solvents. Therefore, it cannot be contained in a large amount, and should be the minimum amount that can provide a satisfactory peeling property. Generally the total amount of solvent,
That is, 1 to 10% by weight, preferably 1 to 10% by weight, based on the total amount of the solvent system composed of the solvent (a) mainly containing 1,3-dioxolane and water or the aliphatic alcohol (b) having 1 to 6 carbon atoms. 1 to 8% by weight, more preferably 1.5
~ 5% by weight. If the content exceeds 10% by weight, the solubility in the polymer of the solvent system and the stability of the dope are deteriorated, so that it is not preferable.

When water or alcohol is contained in the solution composition, the molecular weight may be lowered due to the decomposition of the polymer, so that the type of polyarylate resin used is limited.
The water or lower aliphatic alcohol present in the 1,3-dioxolane solution does not affect the ester bond at all, but the carbonate bond may be gradually hydrolyzed or subjected to alcoholysis to lower the molecular weight of the polymer. .
Therefore, from the viewpoint of storage stability of such a solution composition, when water or the above alcohol is contained in the solution composition, 100 moles of the repeating unit represented by the formula (II) is formed only by the ester bond. %, Or a polyarylate-based resin having a bonding group having no hydrolyzability such as an ether bond other than an ester bond is preferably used.

The solution composition of the present invention containing 1,3-dioxolane as a main solvent may be prepared by any method as long as a transparent solution having a low haze can be obtained as a result. Generally, a method of dissolving the resin while heating the solvent is preferable because the solubility is high and a solution can be obtained in a short time. In this case, the temperature of the solvent is suitably 40 to 60 ° C.

To obtain a solution composition containing a small amount of water and / or alcohol, a predetermined amount of water and / or alcohol may be added to a solution prepared by previously dissolving a polyarylate resin in a solvent, The polyarylate resin may be dissolved in a solvent system containing a predetermined amount of water and / or alcohol. However, as described above, since water and alcohol are poor solvents, the former method may cause dope cloudiness due to the precipitation of the polymer.
The method of dissolving the polymer in the solvent system is preferred.

According to the present invention, the concentration of the solution composition (dope) is 15 to 90 parts by weight, preferably 20 to 50 parts by weight, based on 10 parts by weight of the polyarylate resin. When the amount of the solvent exceeds 90 parts by weight, the stability of the solution is not a problem, but it is not preferable because the effective concentration of the polyarylate resin is low, and a film is formed by a solution casting method using this solution composition. In this case, since the solution viscosity is low, external disturbance easily occurs and the surface smoothness is impaired, which is not preferable. Conversely, if the amount of solvent is less than 15 parts by weight, it is difficult to obtain a stable dope. These concentrations are mainly due to the stability of the dope,
It is determined in consideration of the solution viscosity.

If impurities, insoluble matter such as microcrystals, or suspended matter are present in the prepared dope, or if haze is observed in the dope, these must be removed by a treatment such as filtration. If such treatment is not carried out, the optical properties of the formed film may be deteriorated, and the storage stability of the prepared dope itself may be deteriorated. Generally, in the solution casting method, the dope filtration step is essential, and one of the advantages over the melt extrusion method is that minute impurities can be removed at this point.

The dope of the present invention is preferably stored in a heated state from the viewpoint of solution stability. Preferably 30 to 7
6 degreeC, More preferably, it is 40-70 degreeC. If the storage temperature is lower than 30 ° C, whitening of the dope may occur earlier due to precipitation of the polymer, and if higher than 76 ° C, 1,3-dioxolane as a solvent may boil.

In the present invention, a solution composition (dope) obtained by dissolving a polyarylate resin in a solvent mainly containing 1,3-dioxolane 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 step (1), a doctor blade method, a reverse roll coater method, a die extrusion method, or the like is used. Industrially, the most common method is to continuously extrude a dope from a die onto a belt-shaped or drum-shaped supporting substrate. The supporting substrate used is not particularly limited, but a glass substrate, a metal substrate such as stainless steel or a ferro type, a plastic film such as polyethylene terephthalate, or the like is used. However, a metal substrate having a mirror-finished surface is most commonly used in order to industrially obtain a homogeneous film having a high optical isotropy, which is the main object of the present invention. The improvement of the peelability of the cast film by adding water and / or lower aliphatic alcohol in the present invention is recognized to be effective in such a metal substrate.

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 resin, the molecular weight and the type of the solvent, the viscosity of the solution composition of the present invention is 300 to 5
10,000 cps, preferably 700-30,000 cs
ps. When the viscosity of the solution exceeds 50,000 cps, 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 300 cps, the fluidity is too high, it is difficult to uniformly discharge the solution from the T-die used for normal casting, or the surface is apt to be disturbed due to external disturbance, and a uniform and smooth film cannot be obtained.

The temperature at the time of casting the above solution composition depends on the solvent used, but is generally 10 to 60 ° C., preferably 15 to 5
It is carried out in the range of 0 ° 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 is 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 makes it difficult to obtain smoothness and causes dew condensation, which is not preferable.

Before transferring from the casting process to the pre-drying process, the surface property of the film can be highly smoothed (leveling effect) by suppressing the drying for a certain period of time and ensuring the fluidity of the dope. . At this time, in a low boiling point volatile solvent such as dichloromethane or chloroform, the solvent is significantly evaporated even at room temperature. for that reason,
Disturbance due to evaporation occurs and at the same time the surface is dried,
There is a strong tendency for the so-called Yuzu skin phenomenon to occur. On the other hand,
Since 1,3-dioxolane used in the present invention has an appropriate boiling point and volatility, such a phenomenon is unlikely to occur, and it is preferable for film formation which requires a high degree of smoothness.

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 desirable to start the drying from the lowest boiling point of the solvents used, preferably from the range having its (boiling point −5) ° C. as the upper limit. After that, it is advantageous to increase the drying efficiency by raising the temperature. 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 can be increased stepwise or continuously and is rather preferred. 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 this step. At that time, if the residual solvent amount is large, the film is deformed because it is soft, and if the residual solvent amount is small, even the film cast from the dope containing water or alcohol has high adhesion to the supporting substrate and peeling property. Stress deterioration, peeling scratches, and peeling streaks occur. Therefore the amount of residual solvent is an important factor,
The residual solvent amount is preferably 5 to 25% by weight, more preferably 7
A range of up to 20% by weight is selected.

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 large amount of residual solvent, deformation occurs over time, or 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, in forming a film which is required to have a high degree of optical homogeneity such as for use in a liquid crystal display device, the drying temperature must be selected from the range in which the film is not deformed.
Generally, when the glass transition temperature of the polyarylate resin used is Tg (° C), (Tg-100 ° C) to Tg
Range, preferably (Tg-80 ° C) to (Tg-10
(° C) range is selected. If it exceeds Tg, thermal deformation of the film is apt to occur, and if it is lower than (Tg-100 ° C), the drying rate becomes remarkably slow, which is not preferable. Thermal deformation becomes less likely to occur as the residual solvent decreases. Therefore,
It is preferable to employ a method in which the temperature is initially low and the temperature is raised stepwise or continuously within this range.

We have found a method in which the post-drying step is more strictly controlled than the above to continuously obtain a film having extremely high optical isotropy. As will be demonstrated in a reference example (FIG. 1) to be described later, the glass transition point of the polyarylate-based film largely depends on the amount of residual solvent, and significantly decreases as the amount of residual solvent increases. At a temperature above the glass transition point, the elastic modulus of the film is drastically reduced, and the film is apt to be significantly deformed. From such a viewpoint, the drying temperature in this step needs to be controlled particularly strictly in consideration of the glass transition point of the film containing the solvent.

In the present invention, drying is carried out by the following formula (I) in a state in which the film can shrink in the width direction, that is, in a tensionless state.

[0058]

## EQU2 ## Tg'-50 <T <Tg '... (I) [where Tg' (° C) is the glass transition point of the polyarylate film containing the residual solvent, and this temperature increases as the drying progresses. It rises with a decrease in the amount of residual solvent. ] In the range of the drying temperature (T), and the drying is carried out by raising the temperature continuously or stepwise according to the transition of Tg '. Here, T is a dry atmosphere temperature.

Tg 'here is DSC (Diffe
rental Scanning Calorimet
It is defined as the falling temperature when the sample is enclosed in a closed cell by the ry) method and measured at a temperature rising rate of 20 ° C./min.

In the post-drying step, the residual solvent decreases as the film is conveyed, and Tg '
Goes up. Therefore, in order to efficiently dry the film without causing distortion in this step, it is advantageous to raise the temperature according to Tg '. If the temperature is lower than Tg'-50 ° C, it cannot be dried efficiently, which is not preferable. On the other hand, if it exceeds Tg ', distortion occurs, which is not preferable. The temperature may be raised continuously, but in terms of equipment, it is divided into 3 to 10 stages, preferably 4 to 7 stages, and the T
A method of stepwise heating according to g'is preferably adopted.

More preferably, the drying temperature is

[0062]

## EQU3 ## Tg'-30 <T <Tg ' Is.

In this post-drying step, air may be blown as in the pre-drying step. The film transport speed is not particularly limited, but is generally 0.5 to 15 m / min, preferably 1 to 10 m / min.

Next, the film drying method in an inert gas atmosphere will be described.

As described above, the drying step includes the pre-drying step and the post-drying step, both of which are usually performed in the air atmosphere. At least in the pre-drying step, the solvent used for preparing the dope does not contain a high concentration. Drying in an active gas is preferable from the viewpoint of safety.

As the inert gas forming the inert gas atmosphere, nitrogen gas, argon gas, helium gas,
A non-oxidizing non-combustible gas such as carbon dioxide may be mentioned. Of these, nitrogen gas and carbon dioxide gas are most preferably used in consideration of economy.

The oxygen concentration contained in the inert gas is preferably 10% by volume or less, more preferably 8% by volume or less,
It is more preferably 5% by volume or less. Oxygen concentration is 10
If the content is higher than the capacity%, the possibility of explosion increases, which is not preferable. The oxygen concentration has only to satisfy the above conditions, has no technical lower limit, and is appropriately determined in consideration of economic efficiency.

The inert gas atmosphere preferably contains the vapor concentration of the solvent containing 1,3-dioxolane as a main component contained in the dope in an amount of preferably 3% by volume or more, more preferably 5% by volume or more. However, it is preferable in consideration of the recovery efficiency of the solvent. The upper limit concentration is not particularly limited, but is preferably 50% by volume or less of the saturated vapor concentration at the drying temperature.
If it is higher than this, the drying speed is lowered, which is not preferable.

By introducing an inert gas containing such a solvent vapor into a cooled condenser and recovering the solvent in an inert gas atmosphere, 1,3-dioxolane, which is easily oxidized, is stably recovered. You can

In carrying out the present invention, a high-concentration product is obtained by connecting an inert gas source such as nitrogen equipped with a flow rate controller to the air introduction part of an ordinary dryer and connecting a cooling condenser to the exhaust port. It is possible to recover the solvent from the atmosphere. Such a device has already been technically developed (see Japanese Patent Publication No. 55-36389 and Japanese Patent Publication No. 59-21656).

Since most of the solvent is removed in the pre-drying step, the post-drying step does not necessarily have to be performed in an inert gas atmosphere, but may be performed in air. However, it is self-evident that the post-drying step should be carried out in an inert gas atmosphere even if the solvent concentration in the atmosphere is low.

As described above, when drying in an inert gas atmosphere, there is no concern about the explosion limit, so it is possible to dry in an atmosphere containing a high concentration of solvent, and the solvent can be recovered by a simple condensation method. On the other hand, in an air atmosphere, it is necessary to dry in a low-concentration solvent atmosphere below the explosion limit, and only methods such as adsorption method and gas absorption method can be applied, so it is economical from the viewpoint of solvent recovery and purification. There are unavoidable disadvantages. Also,
For drying in an inert gas atmosphere, 1,3-solvent is used.
Since air oxidation of dioxolane does not occur, purification of peroxide is suppressed, which is preferable. Further, it was generally believed that the lower the concentration of the solvent vapor, the more efficiently the drying proceeded, but surprisingly, the drying proceeded smoothly even in the high solvent concentration atmosphere of the present invention, and the post-drying step It was found that if the total drying including the above is also included, the drying can be performed at a speed comparable to that in the low solvent concentration atmosphere in the air. This is because surface drying is suppressed in the initial stage in a high solvent concentration inert gas atmosphere, and a film layer (skin layer) is not formed on the film surface, so that the diffusion of the solvent in the film proceeds smoothly in the subsequent drying process. It is presumed to do so.

The means for drying in the drying step is as follows:
Hot air heating, electric heating, infrared heating and the like are used.
Other than that, microwave heating has been found. The principle of microwave heating is based on that the dipole contained in the object to be heated is shaken by the microwave. Therefore, the microwave absorption efficiency depends on the magnitude of the dipole moment and the ease with which the molecule moves following the period of the microwave. Water is a typical substance satisfying both of them, and it has been put into practical use as a so-called microwave oven and is industrially used for drying products containing water. However, it is not always effective for general organic substances. For example, as the dry ice, which is carbon dioxide, cannot be heated at all in the microwave oven, the dipole moment is canceled out in the molecule having the symmetrical structure, and the effect of microwaves is poor. What is effective in the present invention is that the solvent 1,3-dioxolane has two oxygen atoms which are negative atoms in the molecule, and the two oxygen atoms are asymmetric because the molecular structure is asymmetric. This is because the dipoles involved do not cancel each other out. Incidentally, 1,4-dioxane, which is the same cyclic ether solvent, has two oxygen atoms, but it is not suitable for microwave heating due to the symmetry of its structure.

Ideally, the frequency of the microwave heating device used in the present invention should be selected so that the molecules of both 1,3-dioxolane and polyarylate resin can move easily. However, in general, due to the restrictions of the Radio Law and microwave electron tubes, 2,450MHz
A heating device having a frequency of is common. However, 915 MHz can also be used as long as it does not interfere with other communications. In the present invention, the frequencies of 2,450 MHz and 915 MHz are preferably used because of such circumstances. In the present invention, microwave heating may be used in all of the pre-drying and post-drying steps, or may be used in part thereof. It may also be used in combination with hot air heating, electric heating, infrared heating and the like. Further, it may be dried by a continuous method (conveyor oven method) or a batch method. The microwave intensity is selected in consideration of foaming of the film, citron skin, waviness and the like.

The thickness of the film obtained in the present invention is 10
To 300 μm, preferably 50 to 200 μm. In particular, the thickness of 50 to 200 μm is preferably used for the plastic substrate and the original film for retardation film which constitute the liquid crystal display device. 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.

Thickness unevenness significantly affects optical characteristics.
The thickness unevenness in this case corresponds to fine unevenness due to surface roughness, and is defined here as the difference between the highest peak and the lowest valley bottom when the film is traversed by 1 cm at any place. The measuring method is not particularly limited, but a stylus method is generally used.
The thickness variation of the film obtained in the present invention is 0.1 to 1.0% of the average film thickness, preferably 0.2 to 0.8.
%.

Thus, according to the present invention, an optically transparent film having an excellent visible light transmittance at a wavelength of 550 nm and a small haze value can be obtained. Further, the film has good surface properties, small thickness unevenness, and an extremely small amount of residual solvent. Furthermore, it is possible to produce an optically highly homogeneous isotropic film with small variations in retardation and slow axis in the film plane (direction in which the refractive index becomes maximum in the film plane).

The optically isotropic film obtained by the present invention can be used after being uniaxially stretched.

[0079]

According to the present invention, the use of 1,3-dioxolane, which is a non-halogen-based solvent, which has no risk of environmental pollution, as the main solvent allows the solution casting method to improve surface properties,
A polyarylate-based film having excellent transparency and optical homogeneity and having a small amount of residual solvent can be obtained. Further, by containing a small amount of water or a lower alcohol in the solvent, the releasability from the supporting substrate is improved, which is effective for continuous film formation. Such a film is effective as an optical film used in a liquid crystal display device or the like, particularly as a retardation film, a plastic substrate or the like.

[0080]

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. Peroxide determination: Peroxide determination was carried out by titration method. Molecular weight: GPC manufactured by Tosoh Corp., HLC8020 type was used to determine the polystyrene-equivalent number average molecular weight.

[Example 1] X in the above formula (II) is 2,2
A propylene group, R ^{1 to} R ⁴ are methyl groups, and Ar is p
-A polyarylate resin [number average molecular weight = 37,000 (in terms of polystyrene), glass transition point = 245 ° C] consisting of a repeating unit which is a phenylene group is dissolved in 1,3-dioxolane at 50 ° C with stirring to obtain a concentration. 20% by weight
A clear solution of was prepared. The solution viscosity of this solution at 30 ° C. was 4.5 × 10 ³ cps. The solution had good stability without any change in viscosity or white turbidity.
This solution was filtered using a filter having a pore size of 5 μm, and then cast on a ferrotype substrate using a doctor blade. After casting, 40 ° C for 3 minutes, 65 ° C for 7 minutes, 10
After heating and drying at 0 ° C. for 7 minutes, the film was peeled from the substrate. The residual solvent amount of the film in this state was 14.7% by weight. Both ends of the film were loosely fixed and further dried in a dryer at 140 ° C. for 10 minutes and 180 ° C. for 60 minutes to obtain a dried film. The obtained film was excellent in surface property without any foaming, citron skin, or waviness. Thickness is 100 μm, thickness unevenness is 0.76 μ
m, and the film was highly uniform. The residual solvent amount was 0.2% by weight, which was an extremely small amount. Again 550
The light transmittance at a wavelength of nm was 90.2%, and the haze value was 0.3%, which was optically transparent. Furthermore, since little force is applied to the film in the drying after peeling the film from the substrate, the optical isotropy and homogeneity are high,
The phase difference at a wavelength of 590 nm is 10 nm or less,
There was little variation within the film. Also, the dispersion of the slow axis (direction in which the refractive index is maximum in the film plane) is ±
It was 10 ° C or lower.

Example 2 As a polyarylate resin, X in the above formula (II) is 2,2-propylene group, Ar
Is a p-phenylene group and an m-phenylene group (molar ratio 1: 1), R ^{1 to} R ⁴ are hydrogen groups, and Y in the formula (V) is 2,2-propylene group, R ^{5 to} R ⁸ Is a hydrogen-containing repeating unit and the ratio of the repeating units represented by the formulas (II) and (V) is 64/36 [number average molecular weight = 26,000 (polystyrene conversion), glass transition Point = 184 ° C.],
It was dissolved in 3-dioxolane at 50 ° C. with stirring to prepare a transparent solution having a concentration of 23% by weight. 30 ℃ of this solution
The solution viscosity at was 4.0 × 10 ³ cps. No change in viscosity or cloudiness was observed in this solution, and the stability was good. This solution was filtered using a filter having a pore size of 5 μm, and then cast on a ferrotype substrate using a doctor blade. After casting, the film was heat dried at 40 ° C. for 3 minutes, 65 ° C. for 7 minutes, and 100 ° C. for 7 minutes, and then the film was peeled from the substrate. The residual solvent amount of the film in this state is 1
It was 4.2% by weight. Loosely fix both ends of such a film, and further in a dryer at 130 ° C. for 10 minutes for 16 minutes.
Drying was performed at 0 ° C. for 60 minutes to obtain a dry film. The surface of the obtained film was good without any foaming, citron skin, or waviness. The thickness was 103 μm and the thickness unevenness was 0.68 μm, and the film was highly uniform.
The residual solvent amount was 0.3% by weight, which was an extremely small amount.
The light transmittance at a wavelength of 550 nm is 90.7.
%, The haze value was 0.4%, and it was optically transparent.
Furthermore, since almost no force is applied to the film by drying after peeling the film from the substrate, the optical isotropy and homogeneity are high, and the phase difference at a wavelength of 590 nm is 10 nm.
It was below, and there were few variations in the film. The variation of the slow axis was ± 10 ° C or less.

[Comparative Example 1] In Example 2, 1,3-
Tetrahydrofuran was used in place of dioxolane to prepare a solution, which was a slightly cloudy dope with poor transparency. The dope was completely whitened after a day of storage at 30 ° C. in a sealed container.

Example 3 As bisphenol, bis (4-hydroxy-3-methylphenyl) sulfide,
And 1,1-bis (4-hydroxyphenyl) cyclohexane (molar ratio 8: 2), terephthalic acid chloride and isophthalic acid chloride (molar ratio 5: 5) as dicarboxylic acid components, and polymerized by an interfacial polycondensation method. Polymerized [number average molecular weight = 51,000 (in terms of polystyrene), glass transition point = 166 ° C.]. This is 1,3-
Dissolve in dioxolane with stirring at 50 ° C,
A weight% clear solution was obtained. The solution viscosity of this solution at 30 ° C. was 3.5 × 10 ³ cps. No change in viscosity or cloudiness was observed in this solution, and the stability was good. This solution was filtered using a filter having a pore size of 5 μm, and then cast on a ferrotype substrate using a doctor blade. After casting, 3 minutes at 40 ℃, 7 minutes at 65 ℃, 1
The film was peeled off from the substrate by heating and drying at 00 ° C. for 7 minutes. The residual solvent amount of the film in this state is 14.1
% By weight. Both ends of the film were loosely fixed and further dried in a dryer at 120 ° C. for 10 minutes and at 155 ° C. for 60 minutes to obtain a dried film. The surface of the obtained film was good without any foaming, citron skin, or waviness. Thickness is 100 μm, thickness variation is 0.53
The thickness was μm, and the film was highly uniform. The residual solvent amount was 0.3% by weight, which was an extremely small amount. Again 55
The light transmittance at a wavelength of 0 nm was 90.0%, and the haze value was 1.5%, which was optically transparent. Furthermore, since little force is applied to the film in the drying after peeling the film from the substrate, the optical isotropy and homogeneity are high, the phase difference at a wavelength of 590 nm is 10 nm or less, and the variation in the film is small. . The variation of the slow axis was ± 10 ° C or less.

Example 4 In 1,3-dioxolane containing 3% by weight of water, in the bisphenol component in the above formula (II), X is 2,2-propylene group and R ^{1 to} R ⁴ are hydrogen groups. Some are 60 mol%, X is a methylene group, R ^{1 to} R ⁴ are methyl groups are 40 mol%, and Ar is a p-phenylene group and an m-phenylene group (molar ratio 7: 3). A copolymerized polyarylate resin consisting of repeating units [number average molecular weight = 36,000 (in terms of polystyrene), glass transition point = 211 ° C.] was dissolved with stirring at 50 ° C. to obtain a transparent solution having a concentration of 20% by weight. It was The solution viscosity at 30 ° C. of this solution is 5.2 × 10 ³ cps.
Met. The solution was highly stable without clouding. This solution was filtered using a filter having a pore size of 5 μm, and then cast on a ferrotype substrate using a doctor blade. This substrate is a new ferrotype plate thoroughly washed and dried. 3 minutes at 40 ° C after casting
After heat-drying at 65 ° C. for 7 minutes and 100 ° C. for 7 minutes, the film was peeled from the substrate. The peelability was extremely good, and peeling scratches and peeling streaks were not found on the film surface. No whitening of the film was observed and the transparency was high. The amount of residual solvent in the film at the time of peeling was 15.7%,
The film thickness was 108 μm. This operation was repeated using the same substrate. In this case, it was repeated 6 more times, but the peelability did not change and all were good. The results are shown in Table 1.
Shown in.

Example 5 The copolymerized polyarylate resin used in Example 4 was dissolved in 1,3-dioxolane containing 3% by weight of ethanol at 50 ° C. with stirring to give a transparent 20% by weight solution. A solution was obtained. The solution viscosity of this solution at 30 ° C. was 3.5 × 10 ³ cps. The solution was highly stable without clouding. Example 4
In the same manner as described in (1), it was cast on a ferro-type substrate and dried to examine the peelability, but the peelability was good after repeating 7 times. The results are shown in Table 1.

COMPARATIVE EXAMPLE 2 Example 4 was applied to 40 parts by weight of a 1,3-dioxolane solvent containing 12% by weight of ethanol.
10 parts by weight of the copolymerized polyarylate resin used in Step 50.
Although it was dissolved with stirring at, the solubility was poor and only a cloudy dope was obtained. The results are shown in Table 2.

[Example 6] 2% by weight of isopropanol
In the 1,3-dioxolane contained, X in the above formula (II) is 3,3,5-trimethyl-1,1-cyclohexylene group, Ar is p-phenylene group and m-phenylene group (molar ratio 7: 3 ), A polyarylate resin comprising a repeating unit in which R ^{1 to} R ⁴ are hydrogen groups [number average molecular weight = 4
2,000 (polystyrene equivalent), glass transition point = 27
8 ° C] was dissolved at 50 ° C with stirring to prepare a transparent solution having a concentration of 20% by weight. The solution viscosity of this solution at 30 ° C. was 7.5 × 10 ³ cps. The solution was highly stable without clouding. It was cast on a ferrotype substrate in the same manner as in Example 4 and dried to examine the peelability. Repeating 7 times, the peelability was good. The results are shown in Table 1.

The results of Examples 4 to 6 and Comparative Example 2 are summarized in Table 1. By adding proper amounts of water, ethanol and isopropanol, the peelability of the cast film from the supporting substrate can be kept good.

[0091]

[Table 1]

A: Copolymer polyarylate resin used in Examples 4 and 5 B: Polyarylate resin used in Example 6

Example 7 The dope used in Examples 4 and 5 was stored in a sealed container at 50 ° C., and the change in solution viscosity with time was examined. The results are shown in Table 2. As is clear from Table 2, the solution of polyarylate was stable with almost no change in solution viscosity.

[0094]

[Table 2]

A: Copolymer polyarylate resin used in Examples 4 and 5

Reference Example 1 Using the 1,3-dioxolane solution of the polyarylate resin prepared in Example 1, the drying conditions were changed to obtain different film thicknesses with different residual solvent amounts.
A film of 00 μm was produced. The glass transition point (Tg ′) of such a film is shown in FIG. As is clear from the figure, Tg 'decreased significantly as the amount of residual solvent increased.

Reference Example 2 The copolymerized polyarylate resin used in Example 4 was dissolved in 1,3-dioxolane at 50 ° C. with stirring to obtain a transparent solution having a concentration of 20% by weight. The solution viscosity at 30 ° C. of this solution is 4.8 × 1.
It was 0 ³ cps. By using this solution and changing the drying conditions, a film having a film thickness of 100 μm and different residual solvent amounts was produced. The glass transition point (Tg ′) of such a film is shown in FIG. As is clear from the figure, Tg 'decreased significantly as the amount of residual solvent increased.

Example 8 Continuous film formation was carried out using the 20% by weight 1,3-dioxolane solution of the polyarylate resin used in Reference Example 1. The casting device pushes the dope from the die to the belt through the filtration process,
The method connected to the pre-drying furnace divided into stages was adopted. 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 40 ° C (no wind),
The temperature was raised to 65 ° C. (wind speed 1 m / sec) and 90 ° C. (wind speed 5 m / sec), and finally 40 ° C. for cooling. 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. In the post-drying oven, the temperature was 95 ° C (residual solvent amount 13% by weight, Tg '= 108 ° C), 115 ° C (residual solvent amount 11% by weight) depending on the residual solvent amount, that is, Tg', in a state of being able to shrink in the width direction. %, Tg ′ = 123 ° C.), 140 ° C. (residual solvent amount 8% by weight, Tg ′ = 147 ° C.), 160 ° C. (residual solvent amount 4% by weight, Tg ′ = 188 ° C.), 185 ° C. (residual solvent amount 2 % By weight, Tg ′ = 214 ° C.), and 200 ° C. (residual solvent amount 1% by weight, Tg ′ = 229 ° C.) were gradually heated to obtain a dry film. The film thus obtained was free from foaming, citron skin and waviness and had good surface properties. Thickness is 9
The film was 9 μm and the thickness unevenness was 0.56 μm, and the film was extremely uniform. The residual solvent amount was 0.05% by weight, which was an extremely small amount. The light transmittance at a wavelength of 550 nm was 90.1% and the haze value was 0.3%, which was optically transparent. The phase difference at a wavelength of 590 nm was 10 nm or less, and the variation within the film was small. Also, the variation of the slow axis was ± 10 ° or less, and the film was optically uniform.

[Example 9] After peeling the film prepared in the same manner as in Example 8 until the film peeling step, the film was heated to 125 ° C in the first to third steps of the post-drying oven and 180 ° C in the fourth to sixth steps. It was dried. The amount of residual solvent in the obtained film was 0.1% by weight. The light transmittance at a wavelength of 550 nm was 90.2% and the haze value was 0.3%, which was optically transparent. When the phase difference at a wavelength of 590 nm was determined, it was 35 ± 10 nm, and the variation of the slow axis was ± 30 °.

Example 10 Continuous film formation was carried out using the 20% by weight solution of the copolymerized polyarylate resin used in Reference Example 2 in 1,3-dioxolane. The same casting equipment and drying oven as used in Example 8 were 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 40 ° C (no wind), 65 ° C
(Wind speed 0.5 m / sec), the temperature was raised to 90 ° C. (wind speed 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. The temperature of the post-drying oven is set to 87 ° C depending on the amount of residual solvent and therefore Tg '.
(Residual solvent amount 12% by weight, Tg ′ = 90 ° C.), 92 ° C.
(11% by weight of residual solvent, Tg ′ = 97 ° C.), 100 ° C.
(Residual solvent amount 9% by weight, Tg ′ = 110 ° C.), 123 ° C.
(Residual solvent amount 7% by weight, Tg ′ = 128 ° C.), 160 ° C.
(3% by weight of residual solvent, Tg ′ = 170 ° C.), 185 ° C.
The temperature was raised to (residual solvent amount 1% by weight, Tg ′ = 196 ° C.) to obtain a dry film. The film thus obtained was free from foaming, citron skin and waviness and had good surface properties.
The thickness was 100 μm and the thickness unevenness was 0.72 μm, and the film was extremely uniform. The amount of residual solvent is 0.2
It was a weight% and was extremely small. The light transmittance at a wavelength of 550 nm is 90.0% and the haze value is 0.2.
%, And was optically transparent. The phase difference at a wavelength of 590 nm was 10 nm or less, and the variation within the film was small. Also, the variation of the slow axis is ± 10 °
It was the following and was an optically homogeneous film.

[Example 11] Up to the film peeling stage, after peeling the film produced in the same manner as in Example 9, 100 ° C in the 1st to 3rd stages of the post-drying furnace and 170 ° C in the 4th to 6th stages.
After that, it was dried. The amount of residual solvent in the obtained film was 0.3% by weight. The light transmittance at a wavelength of 550 nm was 89.7% and the haze value was 0.3%, which was optically transparent. When the phase difference at a wavelength of 590 nm was determined, it was 25 ± 20 nm, and the variation of the slow axis was ± 35 °.

[Embodiment 12] The water used in Embodiment 4 is 3 times.
A continuous film forming test was conducted using a 20% by weight solution of a copolymerized polyarylate resin containing 1,3-dioxolane as a solvent in an amount of 1% by weight. The same casting equipment and drying oven as used in Example 9 were used. The drying conditions were exactly the same as in Example 9. The peelability of the cast film from the belt was good, and peeling streaks and peeling scratches were not observed in the obtained film. Further, it had excellent surface properties without foaming, citron skin, or waviness.
The thickness was 102 μm and the thickness unevenness was 0.58 μm, and the film was extremely highly uniform. The amount of residual solvent is 0.3
It was a very small amount (% by weight), and almost no added water remained. The glass transition point of this film is 207 ℃
And was almost the same as the original resin. When the molecular weight of the film was measured by GPC, the number average molecular weight was 36,000, which was not changed at all. Therefore, it was confirmed that the hydrolysis of polyarylate did not occur during the film forming process. The light transmittance at a wavelength of 550 nm was 89.9% and the haze value was 0.3%, which was optically transparent. The phase difference at a wavelength of 590 nm was 10 nm or less, and the variation within the film was small. Also, the variation of the slow axis was ± 10 ° or less, and the film was optically uniform. This continuous film forming test was conducted continuously for 24 hours, during which time the peelability of the cast film from the belt remained good, and no peeling streaks or peeling scratches were observed in the obtained film.

Example 13 Using the 20% by weight solution of the copolymerized polyarylate resin used in Example 9 in 1,3-dioxolane and the continuous film forming apparatus, the film was cast on a supporting substrate and peeled off. The continuous film forming test was carried out by changing the pre-drying process up to 1 to a method of drying in a nitrogen gas atmosphere containing a high concentration of a solvent. The belt conveyance speed was set to 1 m / min and the cast film width was set to 50 cm. After casting the dope,
In a nitrogen gas atmosphere containing 12% by volume of 1,3-dioxolane and having an oxygen concentration of 2% by volume, the temperature of the pre-drying furnace was gradually changed to 40 ° C. (no wind), 65 ° C. (wind speed 0.5 m /
Second), the temperature is raised to 90 ° C (wind speed 5m / sec), and finally 40 ° C.
And cooled. As a result, the film was dried to a residual solvent amount of 13% by weight, which was almost the same as the case of Example 9 which was dried in air. At this stage, the film was peeled from the belt and then sent to a drying oven. The post-drying process is carried out in air and the temperature is adjusted to the residual solvent content, and thus Tg '.
80 ° C. (residual solvent amount 13% by weight, Tg ′ = 85
℃), 87 ℃ (residual solvent amount 12% by weight, Tg '= 90
℃), 98 ℃ (residual solvent amount 9, 5% by weight, Tg '= 10
6 ° C., 123 ° C. (residual solvent amount 7% by weight, Tg ′ = 12)
8 ° C.), 160 ° C. (residual solvent amount 3% by weight, Tg ′ = 17
0 ° C.), 185 ° C. (residual solvent amount 1% by weight, Tg ′ = 19
The temperature was raised to 6 ° C.) to obtain a dry film. The film thus obtained was excellent in surface property without foaming, citron skin, or waviness. Thickness is 100 μm, thickness unevenness is 0.63 μm
And the film was extremely uniform. The residual solvent amount was 0.2% by weight, which was the same as the residual solvent amount of the film of Example 9 performed in an air atmosphere with a low solvent concentration. The glass transition point of the film was 208 ° C. The light transmittance at a wavelength of 550 nm is 90.1%,
The haze value was 0.2% and it was optically transparent. The phase difference at a wavelength of 590 nm was 10 nm or less, and the variation within the film was small. Also, the variation of the slow axis was ± 10 ° or less, and the film was optically uniform. As described above, the physical properties of the film subjected to the pre-drying process in the nitrogen gas atmosphere were almost the same as those of the film obtained in Example 9.

Further, 1,3-dioxolane in the pre-drying furnace in a nitrogen gas atmosphere was taken out from the exhaust port and trapped at -70 ° C., and the amount of peroxide contained therein was quantified. As a result, while the amount of peroxide in 1,3-dioxolane used was 100 ppm, the amount of recovered 1,3 dioxolane was 1,3.
The amount of peroxide in dioxolane is 103 ppm,
Almost no peroxide was generated during film formation.

Example 14 As bisphenol,
1,1-bis (4-hydroxy-3-methylphenyl)
Cyclohexane, terephthalic acid chloride as a dicarboxylic acid component, and isophthalic acid chloride (molar ratio 5: 5) were used to polymerize the polymer by an interfacial polycondensation method [number average molecular weight = 34,000 (polystyrene conversion),
Glass transition point = 192 ° C.]. This polymer was dissolved in 1,3-dioxolane with stirring at 50 ° C. to give a concentration of 23
A weight% clear solution was obtained. The solution viscosity of this dope at 30 ° C. was 5.5 × 10 ³ cps. This solution was filtered using a filter having a pore size of 5 μm and then cast on a glass substrate using a doctor blade. Then, in a microwave heating device of 2,450 MHz, 100 W for 3 minutes, 200 W for 7 minutes, 300 W for 3 minutes, and 500 W for 1 minute.
Dry for 0 minutes. It was peeled from the substrate because it became a self-supporting film by drying by this microwave heating,
The amount of residual solvent at this point was 17.1% by weight. Loosely fix both ends of this film, and then
10 minutes, 150 ° C. for 10 minutes, and 180 ° C. for 60 minutes to obtain a dried film. The surface of the obtained film was good without any foaming, citron skin, or waviness. The thickness was 102 μm and the thickness unevenness was 0.46 μm, and the film was highly uniform. The residual solvent amount is 0.
It was 1% by weight, which was an extremely small amount. The glass transition point of this film was 191 ° C., which was almost the same as the original resin. The light transmittance at a wavelength of 550 nm is 8
It was 9.6% and had a haze value of 0.5% and was optically transparent. Furthermore, since little force is applied to the film in the drying after peeling the film from the substrate, optical isotropy and homogeneity are high, and a phase difference at a wavelength of 590 nm is 10 nm.
It was below, and there were few variations in the film. The variation of the slow axis was ± 10 ° C or less.

Example 15 Using the 20% by weight 1,3-dioxolane solution of polyarylate resin used in Example 1, casting was performed on a ferrotype substrate in the same manner as in Example 1,
It was dried and the film was peeled from the substrate. The amount of residual solvent in the film at this point is 14.7% by weight. Loosely fix both ends of the film, continue to 2,450MHz,
Drying was performed for 60 minutes in a 500 W microwave heating device. The film after microwave heating and drying had no foaming, citron skin, or waviness, and was extremely homogeneous and had high surface properties. The residual solvent amount was 4% by weight. The film was further dried at 180 ° C. for 60 minutes to obtain a dry film. The surface of the obtained film was good without any foaming, citron skin, or waviness.
The thickness was 102 μm and the thickness unevenness was 0.43 μm, and the film was highly uniform. 0.3% by weight of residual solvent
It was an extremely small amount. The glass transition point of this film was 241 ° C., which was almost the same as the original resin. The light transmittance at a wavelength of 550 nm is 89.9%,
The haze value was 0.4% and it was optically transparent. Furthermore, since little force is applied to the film in the drying after peeling the film from the substrate, the optical isotropy and homogeneity are high, the phase difference at a wavelength of 590 nm is 10 nm or less, and the variation in the film is small. . The variation of the slow axis was ± 10 ° C or less. The physical properties of the film subjected to the microwave heating and drying as described above are as follows.
It was almost the same as the film obtained in.

Comparative Example 3 The polyarylate used in Example 12 was dissolved in 1,4-dioxane with stirring at 50 ° C. to obtain a transparent solution. The solution viscosity of this solution at 30 ° C. was 3.1 × 10 ³ cps. This solution was filtered using a filter having a pore size of 5 μm and then cast on a glass substrate using a doctor blade. Example 12 was then continued in a 2,450 MHz microwave heating device.
Similarly, it was dried at 100 W for 3 minutes, 200 W for 7 minutes, 300 W for 3 minutes, and 500 W for 10 minutes, but the drying was insufficient and the amount of residual solvent was large, and a self-supporting film could not be obtained.

Example 16 The polyarylate resin used in Example 1 contains 1,4 dioxane, tetrahydrofuran or cyclohexanone in an amount of 10% by weight and 1,3.
-Dissolve in dioxolane at 50 ° C with stirring to give a concentration of 2
A 0% by weight clear solution was prepared in each case. The solution viscosity of this solution at 30 ° C. is 5.3 × 10 ³ , respectively.
4.0 × 10 ^3, was 5.5 × 10 ³ cps. These solutions had good stability without any change in viscosity or white turbidity. Using these solutions, a film was produced in the same manner as in Example 1 to obtain a film having a thickness of 100 μm. The obtained films were excellent in surface property without any foaming, citron skin, or waviness. The thickness unevenness was 0.58, 0.78, and 0.53 μm, and the film was highly uniform. The residual solvent amount was 0.2% by weight in each case, which was an extremely small amount. Also 550n
The light transmittances at the wavelength of m are 90.2 and 8 respectively.
9.9 and 90.0%, and the haze value is 0.
It was 3, 0.4, 0.3% and was optically transparent. Furthermore, since almost no force is applied to the film by drying after peeling the film from the substrate, all the films have high optical isotropy and homogeneity, and the phase difference at a wavelength of 590 nm is 10 nm or less, which is within the film. There was little variation. Also, the variation of slow axis is ± 10 ℃
It was below.

[Example 17] X in the above formula (II) is 2,
A polyarylate resin (number average molecular weight 22,000) comprising a repeating unit having 2-propylene group and Ar being p-phenylene group and m-phenylene group (molar ratio 1: 1) 2.
3 parts by weight was added to 77 parts by weight of 1,3-dioxolane at 60 ° C. with stirring in three portions. The viscosity of the obtained dope and the dope stability when stored at 60 ° C. are shown in Table 3 below. The dope did not show any viscosity change or cloudiness, and had good stability.

This dope was cast on a glass substrate using a doctor blade, then, at 30 ° C. for 5 minutes and at 40 ° C. for 20 minutes.
Min, 80 ° C. for 20 minutes, and further 100 ° C. for 20 minutes, and the film was peeled from the substrate. The residual solvent amount of the film in this state was 12% by weight.

After the film was further dried at 150 ° C. for 14 hours, the film was peeled from the glass substrate, and the film thickness, residual solvent amount, total light transmittance, haze value, phase difference and glass transition point were measured and evaluated. did. As shown in Table 4 below, the result was that the amount of residual solvent was small, and the transparency, surface property, and homogeneity were good.

Example 18 The number average molecular weight is 30,000.
The same polyarylate resin as in Example 17, which was 0, was used to form a film in the same manner as in Example 17, to obtain a film and evaluate it. The results are shown in Tables 3 and 4 below.

[0113]

[Table 3]

[0114]

[Table 4]

[Brief description of drawings]

FIG. 1 shows the relationship between the glass transition point (Tg ′) and the amount of residual solvent of the films produced in Reference Examples 1 and 2.

[Explanation of symbols]

A: A curve showing the relationship between the glass transition point (Tg ′) of the polyarylate film produced in Reference Example 1 and the amount of residual solvent when 1,3-dioxolane is used as a solvent. B: A curve showing the relationship between the glass transition point (Tg ′) of the copolymerized polyarylate film produced in Reference Example 2 and the amount of residual solvent when 1,3-dioxolane was used as a solvent.

Front Page Continuation (72) Inventor Naoshi Castle, 3-2 Asahigaoka, Hino City, Tokyo, Tokyo Research Center, Teijin Ltd. (56) Reference JP-A-4-193510 (JP, A) (58) Survey Areas (Int.Cl. ⁷ , DB name) C08J 5/18 C08L 67/03

Claims (8)

(57) [Claims] 1. A solvent containing at least 60% by weight of 1,3-dioxolane and capable of dissolving a polyarylate resin.
A polyarylate resin solution composition comprising 90 parts by weight and 10 parts by weight of a polyarylate resin. 2. A solvent (a) containing 60% by weight or more of 1,3-dioxolane and capable of dissolving a polyarylate resin, water or a linear or branched aliphatic alcohol having 1 to 6 carbon atoms. A polyarylate-based resin solution composition comprising at least any one of the above (b) and a polyarylate-based resin, wherein the solvent (a) 1
5 to 90 parts by weight of polyarylate resin, and the amount of water and at least one kind (b) of a linear or branched aliphatic alcohol having 1 to 6 carbon atoms is the above solvent. 1 of the entire solvent system consisting of (a) and (b)
A polyarylate-based resin solution composition, characterized in that it is 10 to 10% by weight. 3. (1) Casting the polyarylate resin solution composition according to claim 1 or 2 onto a supporting substrate, and (2) heating a casting film containing a solvent to evaporate the solvent. A method for producing a polyarylate-based film, comprising: 4. The pre-drying step of (2) above, which comprises (i) evaporating the solvent until the content of the solvent becomes 5 to 25% by weight to form a self-supporting pre-dried film. ) After peeling from the supporting substrate, the pre-dried film is heat-dried in a state capable of shrinking in the width direction, and the drying temperature (T ° C.) here is represented by the following formula (I): Tg′−50 < T <Tg ′ ... (I) [where Tg ′ (° C.) is the glass transition point of the polyarylate film containing the residual solvent, and this temperature increases with the decrease of the residual solvent content as the drying progresses. . ]
The method for producing a polyarylate-based film according to claim 3, wherein the drying is carried out after the temperature is raised continuously or stepwise in accordance with the transition of Tg 'so as to satisfy . 5. The method for producing a polyarylate-based film according to claim 3, wherein at least part of the step (2) is performed in an inert gas atmosphere. 6. The method for producing a polyarylate-based film according to claim 5, wherein the inert gas atmosphere contains 1,3-dioxolane in an amount of 3% by volume or more. 7. The inert gas atmosphere contains 10% by volume of oxygen.
The method for producing a polyarylate-based film according to claim 5, wherein the main component is nitrogen gas contained below. 8. The method for producing a polyarylate-based film according to claim 3, wherein drying is performed by microwave heating in at least part of the step (2).