JP2003033932A - Solution film-forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film-forming method which optimizes a film surface shape in a solution film-forming, and obtains the film or a sheet-shaped molding efficiently and at high productivity. SOLUTION: In the film-forming method for forming the film or the sheet- shaped molding by casting an organic macromolecular solution on a supporting body and by removing a solvent, the film is formed by controlling a shape of the supporting body face of the film by making the supporting body have controlled wettability and surface roughness on which the organic macromolecular solution is to be cast.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solution casting method for an organic polymer such as aromatic polyamide or aromatic polyimide. More specifically, the present invention relates to an efficient solution casting method for a thin film or sheet whose surface shape is controlled, which is used as a base film of a magnetic tape.

[0002]

2. Description of the Related Art While a recording medium such as a magnetic tape has been miniaturized, a thin film has been demanded due to a demand for a longer recording time. In addition, in order to support longer recording times, the base film is required to have highly controlled surface smoothness in order to maintain the electromagnetic conversion characteristics of the ultra-thin magnetic layer such as the vapor deposition type magnetic material. Came to be.
On the other hand, in order for the tape to run stably and smoothly in a magnetic recording device, or to run smoothly and smoothly in the line for producing a base film, a base film is obtained. The slipperiness of is essential.

Therefore, generally, inorganic particles such as silica and calcium carbonate are added to the base film raw material polymer, but an extremely smooth magnetic layer surface and appropriate irregularities for ensuring good slipperiness are provided. In order to produce a base film having a back surface, a high-level technique has been tried in which the base material is a two-layer film, and the magnetic layer and the support layer are formed with different surface morphologies by different additive particles. However, in order to have a two-layer film structure, it is necessary to prepare a stock solution for each layer, send the solution on separate lines, and stack and extrude them in the thickness direction, which makes the manufacturing apparatus extremely complicated. Therefore, there has been a demand for a method that is inefficient and can be manufactured more simply and efficiently.

In addition, a polyethylene terephthalate film has been conventionally used as a base film for a magnetic recording medium, but in order to make the base film for a magnetic recording medium thinner, an aromatic polyamide or aromatic having a high rigidity is used. Materials such as group polyimide are being studied. However, a film of aromatic polyamide or aromatic polyimide having high rigidity can be produced only by solution casting, and a solution casting method for stably producing a highly controlled surface thin film for a long time is required. ing.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and is a method for forming a film or sheet-like molded article from an organic polymer solution, which cannot be achieved by a conventional film forming method. With a simple and easy method, one surface of the obtained film or sheet-shaped molded product is smooth and gives good magnetic characteristics, and the other surface has a surface property that optimizes the uneven shape and gives good running performance. The purpose is to provide a method.

[0006]

[Means for Solving the Problems] In the film forming method, whether a solution film formation or a melt film formation, when a liquid organic polymer is cast on a support to form a film, the film obtained is One side is greatly affected by the shape of the support surface. In order to control the surface shape of the film by transferring the surface state of the support, the solution film-forming method of the present invention requires stable and good wetting of the liquid polymer and the support. It is based on the finding that it is necessary to control the wettability between a metal support and a polymer.

That is, the present invention provides [1] a method of casting a solution of an organic polymer on a support and removing the solvent in the solution to obtain a film or sheet-like molded article, wherein the wetting index is 50 dyne / cm or more, surface roughness (R
a) is a film forming method characterized by casting a solution of an organic polymer on the surface of a metal support, wherein 0 <Ra ≦ 0.1 μm, [2] a solution of an organic polymer A film-forming method according to [1], characterized in that a metal support having an underlying metal oxide film formed on the surface of the metal support to be cast is used. [3] The metal support is an oxide film 20% of the surface of the oxide film containing fine particles
The above is the metal support occupied by the fine particles exposed from the oxide film, [4] the film formation method according to [2], and [4] the metal support is made of stainless steel, carbon steel or tantalum. [1], [2] or [3], wherein the organic polymer is at least one selected from the group consisting of aromatic polyamides and aromatic polyimides. There are [1], [2],
The film forming method according to [3] or [4].

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The organic polymer used in the present invention is not particularly limited as long as it can be dissolved in one or more appropriate organic or inorganic solvents and the solution can be used for film formation. . Examples of such organic polymers include:
Polyamide resin such as aromatic polyamide, aromatic polyimide, cellulose polymer, polyacrylic acid resin, polymethacrylic acid resin, polycarbonate, polyurethane, polyvinyl alcohol resin, polyacrylonitrile, polyesteramide, polyamideimide, polyester resin, silicone resin , Fluororesins and the like.

The solution film-forming method of the present invention is preferably used for an organic polymer having a high melting point exceeding 300 ° C. or having a thermal decomposition temperature lower than the melting point. In particular, aromatic polyamide and aromatic polyimide, which have high rigidity and strength and are strongly required as thin films for applications such as magnetic tape substrates, are preferably used. The aromatic polyamide referred to in the present invention is substantially composed of a unit selected from the group consisting of the following structural units. —NH—Ar ¹ —NH— (1) —CO—Ar ² —CO— (2) —NH—Ar ³ —CO— (3) where Ar ¹ , Ar ² and Ar ³ are at least one aromatic ring. It is a divalent aromatic residue containing. These may be the same or different, and typical examples thereof include the following formulas.

[0010]

[Chemical 1]

(In the formula, X is --O--, --CH _2- , --SO ₂
-, -S-, -CO-, etc. are shown. ) Further, a part of hydrogen atoms on these aromatic rings may be substituted with a halogen group, a nitro group, an alkyl group, an alkoxy group or the like.
In particular, an aromatic polyamide in which 80 mol% or more of all aromatic rings are bound in the para position has preferable properties such as high strength and high elastic modulus, and thus, as an organic polymer used in the present invention. preferable. Among them, polyparaphenylene terephthalamide (hereinafter referred to as PPTA) is the most preferable in that a film or sheet-shaped molded product having small thermal dimensional change and high rigidity and strength can be obtained.

A method for obtaining such an aromatic polyamide includes
For example, there are a low temperature solution polymerization method, an interfacial polymerization method, a method of reacting an isocyanate with a carboxylic acid, and a method of directly polycondensing using a dehydration catalyst, but the low temperature solution polymerization method is suitable because a polymer having a high degree of polymerization is easily obtained. There is. That is, from acid chloride and diamine, N-methylpyrrolidone (hereinafter, referred to as NMP), dimethylacetamide (hereinafter, referred to as NMP).
It is called DMAc. ), Dimethylformamide (hereinafter,
It is called DMF. Polymerization in an aprotic organic polar solvent such as).

When an acid chloride and a diamine are used as monomers in the organic polymer solution, hydrogen chloride is produced as a by-product. When neutralizing this, an inorganic medium such as calcium hydroxide, calcium carbonate or lithium carbonate is used. A solvating agent or an organic neutralizing agent such as ethylene oxide, propylene oxide, ammonia, triethylamine, triethanolamine or diethanolamine is used.

These organic polymer solutions may be used as they are as a stock solution for film formation, or the organic polymer may be isolated once and then redissolved in the above aprotic organic polar solvent or inorganic solvent such as sulfuric acid. A film-forming stock solution may be prepared by Also, the intrinsic viscosity of the organic polymer (value measured at 30 ° C. with 0.5 g of the organic polymer as a 100 ml solution in sulfuric acid)
Is preferably in the range of 2 to 8. Inorganic salts such as calcium chloride, magnesium chloride, lithium chloride and lithium nitrate may be added to the organic polymer solution as a dissolution aid. The organic polymer concentration in the organic polymer solution is preferably about 2-40 wt%.

The aromatic polyimide used in the present invention is one having at least one aromatic ring and at least one imide group in the repeating unit of the organic polymer, and has the general formula shown in Chemical formula 2 or 3 below. It is what is represented.

[0016]

[Chemical 2]

[0017]

[Chemical 3]

Here, Ar ₄ and Ar ₆ each include at least one aromatic ring, and two carbonyl groups forming an imide ring are bonded to adjacent carbon atoms on the aromatic ring. This Ar ₄ is derived from an aromatic tetracarboxylic acid or its anhydride. The following formula is a typical example.

[0019]

[Chemical 4]

(Wherein Y is --O--, --CO--, --CH)
_{2 -, - S -, -} SO 2 - shows the like. Further, Ar ₆ is derived from tricarboxylic acid anhydride or its halide. The following formula is a typical example.

[0021]

[Chemical 5]

Ar ₅ and Ar ₇ contain at least one aromatic ring and are derived from aromatic diamines and aromatic isocyanates. The following are typical examples of Ar ₅ or Ar ₇ .

[0023]

[Chemical 6]

(In the formula, Z is --O--, --CH _2- , --S
_{-, - SO 2 -, -} CO- shows the like. ) Further, a part of hydrogen atoms on these aromatic rings may be substituted with a halogen group, a nitro group, an alkyl group, an alkoxy group or the like. In particular, an aromatic polyimide in which 80% or more of Ar ₅ and Ar ₇ are aromatic rings bonded in the para position is
It is preferable as the organic polymer used in the present invention because it can be formed into a film or sheet having high mechanical properties.

A solution of such an aromatic polyimide is obtained as follows. That is, the polyamic acid used as the raw material is N
It can be prepared by reacting a tetracarboxylic acid dihydrate with an aromatic diamine in an aprotic organic polar solvent such as MP, DMAc or DMF. Then, the aromatic polyimide can be prepared by heating the solution containing the polyamic acid or adding an imidizing agent such as pyridine to obtain a polyimide powder, which is dissolved again in a solvent. The concentration of the organic polymer in the stock solution for film formation is preferably about 5 to 40 wt%.

Next, the solvent for preparing the organic polymer solution is not particularly limited as long as it can dissolve the above organic polymer, and even if it is a mixed solvent, it contains an inorganic salt such as a dissolution aid. However, after preparing the solution,
There should be no change in appearance or precipitation of organic polymers. The means for forming a solution is not particularly limited, and well-known dissolution means and a method for directly obtaining an organic polymer solution by polymerizing in a solvent as described above are also included.

In addition, a soluble organic substance or inorganic salt may be dissolved in the organic polymer solution as long as the solution state can be stably maintained. Further, a lubricant, an antioxidant and other additives may be added within a range that does not impair the physical properties, and insoluble components such as organic or inorganic particles may be dispersed. The organic polymer solution can be formed into a film or sheet-shaped molded product by a dry method or a wet method. As a means for casting into a film or sheet-shaped molded product, conventionally known means can be adopted, and a method using T-die, L-die or the like is practical.

In the present invention, the support on which the organic polymer solution is cast is one whose surface wettability is controlled. The support used in the present invention is a metal support having a surface having a wetting index of 50 dyne / cm or more. The wettability index is used as a scale for quantitatively expressing the degree of hydrophilicity, and the method disclosed in JIS K6768 can be conveniently used as a method for evaluating the wettability of the surface of a metal support in the present invention. .

In solution casting of a film or sheet-shaped molded product, in order to stably realize the required shape of the surface of the film or sheet-shaped molded product by transfer from the support, a web of cast organic polymer solution is used. The affinity with the support is a major factor, and it is important to improve this affinity and increase the adhesion. The wetting index of the surface of the support, which is a substitute property of the affinity between the web of the organic polymer solution and the support, is a very important factor.
In a region smaller than yne / cm, the affinity of the web of the organic polymer solution with the support is low, the transferability is unstable, and the surface property of the obtained film or sheet-shaped molded product becomes uneven, which is not preferable.

From the viewpoint that stable transferability can be obtained and the surface shape of the film or sheet-like molded article can be made uniform, the wetting index is preferably 60 dyne / cm or more, and 70 dy
It is more preferable that it is ne / cm or more. Incidentally, the surface of cleaned smooth chrome plating, nickel plating, stainless steel, etc. generally has a wetting index of 34 to 35d.
Only yne / cm. The upper limit is 80 dyne / cm. It is extremely difficult to realize wettability of more than 80 dyne / cm.

From the viewpoint of enhancing the affinity between the web of the organic polymer solution and the support, the surface of the support is preferably covered with an oxide film of the underlying metal. In particular, poly, p-phenylene terephthalamide (hereinafter PPTA
Abbreviated. In the case of a sparingly soluble aromatic polyamide such as), since sulfuric acid or the like is used as a solvent, the affinity is enhanced and the effect of forming a film at high speed becomes remarkable.

Increasing the wettability of the surface of the support means increasing the surface free energy, but adjusting the surface roughness to an appropriate level improves the adhesion between the support and the polymer solution. It is important both in terms of achieving highly stable shape transfer and controlling the surface condition of the obtained film or sheet-shaped molded product. The surface roughness Ra of the support is preferably in the range of 0 <Ra ≦ 0.1 μm. When the surface is smooth like a mirror surface and Ra is 0, the slipperiness of the obtained film is poor, the line cannot be stably run, and the winding shape is poor. On the other hand, when Ra is 0.1 μm or less, the smoothness of the film surface required for a thin and high-rigidity film for a magnetic recording medium is satisfied, and the obtained film has good slipperiness to stabilize the line. Can run. 0.001 ≦ Ra ≦
The range of 0.07 μm is preferable, and 0.0 is more preferable.
03 ≦ Ra ≦ 0.05 μm.

With regard to the irregularities on the surface of the support, more specifically, the number of protrusions of more than 5 nm and less than 100 nm per 1 mm ² is N ₁ , and the number of protrusions of more than 100 nm is N ₁ .
_{When 2} is set, 5 × 10 ⁶ pieces / mm ² ≦ N ₁ ≦ 5 × 10
⁷ pieces / mm ² , and N ₂ ≦ 2.5 × 10 ⁶ pieces / mm ²
It helps stabilize the slipperiness of the surface of the resulting film. For obtaining these controlled surfaces of the support, the following methods can be used, for example.

The base metal of the support is rolled, welded, ground, and polished to form the base surface. It is possible to form appropriate irregularities by gradually reducing the size of the abrasive particles, finally selecting ultrafine particles of # 10000 or more, and polishing for a long time in the presence of water. As the polishing particles, inorganic particles such as silica, white alundum, green carborundum and diamond are preferably used. The size of the ultrafine particles is preferably 10 μm or less. It is more preferably 5 μm or less, and further preferably 1 μm or less. The shape of the ultrafine particles is not particularly limited, but a spherical shape is preferable because uniform unevenness is not formed and no deep deep recesses are formed.

The unevenness can also be formed by etching the surface of the base metal with a solvent such as an acid or alkali that corrodes the base metal. As the corrosive solvent, an aqueous solution of sulfuric acid, hydrochloric acid, sodium chlorate, sodium hypochlorite, caustic soda, or the like can be used. At this time, it is also possible to disperse ultrafine abrasive particles in a solvent and simultaneously utilize etching and polishing to form irregularities on the surface of the support. After the unevenness is controlled and formed, it is preferable to further oxidize the surface of the support. The oxidation treatment can be performed by, for example, an anodic oxidation method. When a voltage is applied using a metal serving as a support as an anode (+ pole) and a stable electrode such as carbon as a cathode (-pole), hydrogen is generated from the cathode, whereas an anode is used. No oxygen is seen to be generated, and an oxide film is formed on the metal surface.

As the electrolytic solution for the anodization, sulfuric acid, phosphoric acid, nitric acid, sodium hydroxide, water or the like, which can be generally used for the anodization, can be used within a range not causing a problem. It is also possible to coexist with an organic solvent or the like, and the inorganic salt which is the electrolyte is phosphoric acid in advance,
It is also possible to dissolve it in a solvent such as nitric acid, sodium hydroxide or water. Anodization is performed in the bath at a constant current density of several milliamperes to several hundred milliamperes, and when a predetermined voltage is reached, the voltage is switched to a constant voltage until an oxide layer is formed on the metal surface and the current substantially stops flowing. Be seen.
When the voltage is switched to a constant voltage, a phenomenon in which the current density drops sharply is recognized, and it can be seen that the denseness of the formed film increases. The film thickness of this optical interference thin film is determined by the final voltage during anodic oxidation. For example, tantalum forms an oxide film of about 1.6 nm per 1 V, but this value changes depending on the metal material.

The thickness of the final anodic oxide coating is not particularly limited, but as the thickness increases, the surface gradually changes in a direction of smoothing, so that a surface exhibiting effective wettability is required. It is important to control the thickness so that the uneven shape formed on the cast surface of the support metal is retained and finally the wettability and affinity with the organic polymer solution targeted by the present invention are achieved. The film thickness can be determined by the color that appears on the surface due to optical interference, and it is generally good to set it to about 100 nm.

In the anodic oxidation treatment, fine particles are allowed to be present in the electrolytic solution in the process of forming the oxide film, so that the fine particles are taken into the oxide film and positively form irregularities on the surface of the oxide film. Is also a preferred embodiment. The fine particles may be those that are negatively charged in the electrolytic solution. For example, colloidal silica, silica such as fumed silica, tantalum oxide, titanium oxide, zeolite,
Alumina, aluminum hydroxide, aluminum silicate, iron oxide, aluminum and the like can be mentioned, and among them, colloidal silica, titanium oxide and alumina are preferably used.

An electrolytic solution used for anodic oxidation is one in which these fine particles are dispersed in a solvent such as phosphoric acid, nitric acid, sodium hydroxide or water. The concentration of the fine particles contained in the electrolytic solution is not particularly limited, but is generally 0.001 wt% or more, preferably 0.01 wt% or more, and more preferably 0.1 w in order to obtain good wettability.
It is t% or more. The upper limit of the concentration is not particularly limited, but is substantially about 70 wt%.

The average particle size of the fine particles is 1 nm or more and 1 μm.
The following is preferable, and more preferably 5 nm or more and 800 nm
The thickness is more preferably 20 nm or more and 500 nm or less. If it is less than 1 nm, it will be completely taken into the oxide film, or if it is partially exposed, the contact area with the oxide film is extremely small and it will easily fall off.
On the other hand, when it is larger than 1 μm, it is not suitable because it precipitates in the anodizing process, the dispersion and migration during the anodizing cannot be performed, and when it is used as a metal support, irregularities become too large. These fine particles may have a uniform particle size or may have a plurality of particle size distributions as long as the average particle size is in the range of 1 nm to 1 μm.

When the fine particles are incorporated into the oxide film to positively form irregularities on the surface of the oxide film, the surface of the exposed fine particles with respect to the surface of the oxide film formed on the metal surface greatly affects the wetting index. It is necessary that 20% or more of the surface of the metal molded body be occupied by the fine particles exposed from the oxide film, more preferably 30% or more, further preferably 35% or more. 20% of surface
Since the above is occupied by the fine particles, the wetting index is 5
0 dyne / cm or more is achieved. The ratio of the surface of the exposed fine particles to the oxide film depends on SE of the oxide film surface.
It is easily obtained by observing M, and for example, the ratio of exposed particles per 1 square micrometer is calculated.

As the material of the metal support used in the present invention, SUS, carbon steel or the like is preferably used in view of availability, surface workability, durability, corrosion resistance and the like. PPTA
Ta is a particularly preferable material because of its high corrosion resistance against a strongly corrosive solvent such as sulfuric acid used for. In the wet film forming method of an organic polymer solution, an organic polymer solution cast from a die onto a support such as a metal drum or an endless belt is
A part of the solvent is evaporated by heating the web of the organic polymer solution on the support, if necessary, and then introduced into a coagulation bath to coagulate.

The film or sheet-shaped molded product that has undergone the coagulation process is peeled from the support and introduced into a process in which desalting and solvent removal are carried out with an extraction medium in a bath of water or the like, and then stretching, drying and heat treatment. The product is then processed. There is no particular limitation on the thickness of the film or sheet-shaped molded product obtained in the present invention, but as described above, the conventional technique has a large technical limitation in molding a thin product, and therefore the present invention is a film or sheet-shaped molded product. The final thickness of the body is 1 μm or more and 10 μm or less, preferably 1 μm
m or more and 7 μm or less, more preferably 1 μm or more and 5 μm
m or less, particularly preferably 1 μm or more and 4 μm or less, is very preferably adopted.

Further, according to the present invention, since the obtained film or sheet-shaped molded product is excellent in surface property and flatness, it is required to have a higher capacity, and a base material for a magnetic recording medium, which is also strict with such a requirement. It is preferably used in the production of flexible printed circuit boards, TAB carrier tapes, solar cell substrates and other insulating wiring members for electric and electronic devices, capacitors and base materials for heat-sensitive recording transfer materials, which are becoming smaller and lighter. Further, the present invention is of course used for molding a single-layer film or sheet-shaped molded product, but is also preferably used for molding a laminated molded product. The components forming each layer during lamination may be the same or different. In addition, at least one layer forming each layer may contain an additive such as particles within a range that does not impair the object of the present invention, and the type, content, and particle size of these additives may be the same. It can be different.

The film or sheet-shaped molded product thus obtained is a magnetic recording medium, an insulating wiring member for electric equipment, an optical recording medium, an optical material such as a display substrate, a condenser, an ink ribbon substrate, a plate-making plate. It can be suitably used for various applications such as printing members such as materials.
The method of measuring the characteristic value of the present invention is as follows. (1) Wetting Index of Support Surface As a process for rolling, welding, grinding, polishing the base metal of the support, and further obtaining a controlled surface which is a requirement of the present invention, chemical treatment is carried out if necessary. Processing such as etching and anodization is performed to form a controlled surface of the support. A part of the support finally obtained is taken as a sample for measurement by cutting, etc., and the surface on which the polymer solution is cast is measured by the method specified in JIS-K6768. To do. The unit is dyn
e / cm.

(2) Surface Roughness of Support and Film Product (Ra) The surface roughness of the support and film in the present invention can be determined as follows. Measuring device: Kosaka Laboratory's three-dimensional fine shape measuring instrument ET-30K Using a 0.5 μm stylus, a load of 0.05 mN or less, a cutoff of 0.025 mm, an X measuring length of 100 μm, and a Y feed pitch of 0.2 μm, 100 μm × 50 μm (X axis XY axis)
The surface of was measured 10 times at a magnification of 200,000 and the average value was used. Further, the standard deviation was obtained and used as an index of uniformity. (3) Film thickness The film thickness is measured with a digital micrometer (K351C type manufactured by Anritsu Co., Ltd.) having a measurement surface with a diameter of 2 mm at 20 arbitrary points on a 1 m-long sample, and the average value is obtained. It was (4) Thickness variation digital micrometer (K351 manufactured by Anritsu Corporation
C type), the thickness of the film in the width direction is measured at 20 points, and the difference between the maximum value and the minimum value is divided by the average thickness to be 1
The value was obtained by multiplying by 00.

(5) Strength, Elongation and Elastic Modulus Measuring Method The strength, elongation and Young's modulus were measured using a constant velocity elongation type strong elongation measuring machine (DSS500 type manufactured by Shimadzu Corporation), measuring length 100 mm, pulling speed. It is measured at 50 mm / min. (6) A small piece of the support, on which the number of projections on the surface of the support is processed, is fixed, and an atomic force microscope (At
omic Force Microscopy) (TMX2010 Discoverer type manufactured by Topometrix) is used to observe the range of 30 μm × 30 μm in the non-contact mode at a scanning speed of 2 Hz, and the number of protrusions is calculated as the average value of the measured values of 10 fields of view. It was (7) Calculation of the ratio of the particle surface to the surface of the oxide film of the support A small piece of the anodized support is cut out, platinum palladium is vapor-deposited to a thickness of 2 nm, and a Hitachi S-4700 electron microscope is used to The surface was observed at a magnification of 10,000 to 60,000 times. The measurement was performed 5 times while changing the visual field, and the average ratio of the exposed fine particles per 1 μm ² was calculated.

[0048]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to such descriptions.
The following was used as the organic polymer solution. Silica particles having an average primary particle diameter of 15 nm are added to 0.05 w per PPTA.
Concentration 9 dispersed by ultrasonic stirrer to be t%
Intrinsic viscosity (PPT
A 0.5 g as a 100 ml solution in sulfuric acid at 30 ° C
PPTA having a value (measured by 1.) of 4.2 was dissolved so that the organic polymer concentration was 12 wt% to obtain a PPTA / concentrated sulfuric acid solution.

[0049]

[Example 1] A 300 mm wide I (eye) die placed 5 mm above the cast support and connected to a gear pump as a means for extruding a PPTA / sulfuric acid solution. A tantalum belt that has been etched in a 5N caustic soda solution,
A support consisting of a cast roll for driving the belt,
A suction nozzle with a slit clearance of 2 mm is arranged on the upstream side of the I (eye) die as a contact means, and the PPTA / concentrated sulfuric acid solution prepared as described above is fed from a hopper to a gear pump.
I kept at 60 ° C through a filter of μm cut
(Eye) Film thickness of 40 from tantalum belt at 80 ℃
It was cast at a thickness of μm. During film formation, the film thickness of the PPTA / concentrated sulfuric acid solution cast was kept at 40 μm by rotating the gear pump in response to the belt speed.

Moisture absorption treatment is performed on the belt simultaneously with heating, and P
After the PTA / concentrated sulfuric acid solution was phase-converted from the liquid crystal phase to the isotropic phase, the self-supporting film solidified in 25% sulfuric acid at 0 ° C. was continuously peeled from the belt. Then, the film was introduced into the tank, neutralized, washed with water, stretched 1.05 times in the length direction by changing the roll peripheral speed, and then horizontally stretched 1.05 times by a clip tenter. While maintaining a constant length, hot-air drying at 150 ° C, tension heat treatment at 450 ° C, free heat treatment at 300 ° C, and high tension while applying 50mm oscillation at 200m pitch.
It was rolled up on a resin bobbin under high pressure roll pressure.

When the casting was started at a belt speed of 8 m / min, and then the speed was gradually increased while adjusting the discharge rate and the speed of the cast belt so that the final film thickness became constant, a belt of 45 m / min was obtained. I was able to cast very stably even at speed. The film ran in the manufacturing line extremely stably, and the winding shape of the roll was good.
The Ra of the surface on the support side of the obtained film was 3 nm, the Ra of the surface on the air side was 1 nm, and there was almost no variation at 10 measurement points, and it was suitable as a magnetic tape base film. Young's modulus is 14 in both longitudinal and width directions
GPa, 14 GPa, and elongation 19%. Further, there was no problem in surface property, and the thickness unevenness was 4%, which was extremely excellent in practical use. The results are shown in Table 1.

[0052]

[Table 1]

[0053]

Example 2 A film was formed from a PPTA / concentrated sulfuric acid solution in the same manner as in Example 1 except that a tantalum belt etched in a 2N caustic soda aqueous solution was used as a support. Casting could be carried out extremely stably even at a belt speed of 40 m / min. The film ran in the manufacturing line extremely stably, and the winding shape of the roll was good.
The Ra of the surface on the support side of the obtained film was 4 nm, the Ra of the surface on the air side was 1 nm, and there was almost no variation at 10 measurement points, and it was suitable as a magnetic tape base film. Young's modulus is 14 in both longitudinal and width directions
It was GPa, 13 GPa, and the elongation was 17%. Thickness variation is 4
%Met. The results are shown in Table 2.

[0054]

[Table 2]

[0055]

Example 3 Etching in a 0.5N caustic soda aqueous solution, further using 1N sulfuric acid as an electrolytic solution, under a constant current of 10 mA, variable voltage, and performing initial oxidation at 25 ° C. When the voltage reached 100V A PPTA / concentrated sulfuric acid solution was prepared in the same manner as in Example 1 except that a tantalum belt subjected to anodization was used as a support while switching to a constant voltage control with a voltage of 100 V and maintaining the current until it reached 0 mA. The membrane was carried out. The surface of the belt after anodizing exhibited a light blue color.

Casting could be carried out very stably at a belt speed of 50 m / min. The film ran in the manufacturing line extremely stably, and the winding shape of the roll was good. Ra on the support side surface of the obtained film was 2 nm,
Ra on the air surface side was 1 nm, and there was almost no variation at 10 measurement points, which was suitable as a magnetic tape base film. Young's modulus was 14 GPa and 14 GPa in the longitudinal direction and the width direction, respectively, and the elongation was 20%. The thickness variation was 4%. The results are shown in Table 3.

[0057]

[Table 3]

[0058]

[Embodiment 4] After the cast surface is mirror-finished, Embodiment 3
P was prepared in the same manner as in Example 1 except that a tantalum belt anodized under the same conditions as in Example 1 was used as the support.
Film formation was carried out from a PTA / concentrated sulfuric acid solution. The surface of the belt after the anodizing treatment was yellow. Casting could be carried out extremely stably at a belt speed of 35 m / min.
Occurrence of vertical wrinkles was occasionally observed on the free roll just before the winding in the production line, but the roll was running without running fixed wrinkles, and the winding appearance of the roll was good. The film obtained at a belt speed of 35 m / min had a Ra on the support side surface of 2 nm and an Ra on the air side surface of 1 nm, and there was almost no variation at 10 measurement points, and it is suitable as a magnetic tape base film. It was Young's modulus is 14 in both longitudinal and width directions
GPa, 14 GPa, and elongation 19%. Thickness variation is 4
%Met. The results are shown in Table 4.

[0059]

[Table 4]

[0060]

[Example 5] A tantalum belt whose cast surface is once mirror-finished is anodized under the same conditions as in Example 3 using an electrolytic solution containing 10 wt% of colloidal silica having an average particle diameter of 180 nm. A film was formed from a PPTA / concentrated sulfuric acid solution in the same manner as in Example 1 except that it was used as a body. The surface of the tantalum belt had a golden color. The ratio of the exposed colloidal silica particles to the surface of the oxide film formed on the tantalum belt was 30%.

Casting could be carried out very stably at a belt speed of 40 m / min. The film ran in the manufacturing line extremely stably, and the winding shape of the roll was good. Ra on the support side surface of the obtained film was 5 nm,
Ra on the air surface side was 1 nm, and there was almost no variation at 10 measurement points, which was suitable as a magnetic tape base film. Young's modulus was 14 GPa and 14 GPa in the longitudinal direction and the width direction, respectively, and the elongation was 15%. The thickness variation was 5%. The results are shown in Table 5.

[0062]

[Table 5]

[0063]

Example 6 The same as Example 1 except that the cast surface was polished and finished with # 10000 diamond abrasive grains, and an anodized tantalum belt was used as the support under the same conditions as in Example 3. The film was formed from PPTA / concentrated sulfuric acid solution by the method. The surface of the belt after the anodizing treatment was yellow. Casting could be carried out extremely stably at a belt speed of 40 m / min. The film ran in the manufacturing line extremely stably, and the winding shape of the roll was good.
The Ra of the surface on the support side of the obtained film was 5 nm, the Ra of the surface on the air side was 1 nm, and there was almost no variation at 10 measurement points, and it was suitable as a magnetic tape base film. Young's modulus is 14 in both longitudinal and width directions
GPa, 14 GPa, and elongation 19%. Thickness unevenness is 5
%Met. The results are shown in Table 6.

[0064]

[Table 6]

[0065]

Comparative Example 1 A film was formed from a PPTA / concentrated sulfuric acid solution in the same manner as in Example 1 except that a tantalum belt having a mirror-finished cast surface was used as a support. 16m / min
It was observed that the cast occasionally became unstable. The film produced a vertical wrinkle on the free roll at the entrance of the winder, and after being wound on the roll, the vertical wrinkle caused the winding appearance to be scattered. R on the support side surface of the obtained film
The average value of a was 0.2 nm, but spots such as a part of about 1 nm were generated. Ra on the air side is 1.2
It was uniform in nm. The results are shown in Table 7.

[0066]

[Table 7]

[0067]

Comparative Example 2 A film was formed from a PPTA / concentrated sulfuric acid solution in the same manner as in Example 1 except that a tantalum belt having a cast surface polished and finished with # 3000 diamond abrasive grains was used as a support. Casting could be carried out almost stably at a belt speed of 16 m / min, but a satisfactory film could not be obtained due to poor peelability of the film from the support. The results are shown in Table 8.

[0068]

[Table 8]

[0069]

According to the present invention having the above constitution,
In the problem of controlling the surface shape on both sides of the film in the solution film formation, which has been difficult until now, stable and efficient production can be performed with high productivity, especially for a thin film. Further, in the present invention, since the surface property of the obtained film or sheet-shaped molded product is controlled, the running property in the production line is good and the roll shape can be good.

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29L 7:00 B29L 7:00 F term (reference) 4F202 AA30 AA40 AC05 AG01 AJ02 AJ11 AR13 CA07 CB02 CK11 4F205 AA30 AA40 AC05 AG01 AJ02 AJ08 AJ11 AR13 GA07 GB02 GC02 GC07 GN28 5D112 AA02 BA01 BA09

Claims (5)

[Claims] 1. A film-forming method in which a solution of an organic polymer is cast on a support and the solvent in the solution is removed to obtain a film or sheet-like molded article, wherein the wetting index is 50 dyn.
e / cm or more, surface roughness (Ra) is 0 <Ra ≦ 0.1
A method for forming a film, which comprises casting a solution of an organic polymer on the surface of a metal support having a thickness of μm. 2. The film forming method according to claim 1, wherein a metal support having an underlying metal oxide film formed on a surface of the metal support on which the organic polymer solution is cast is used. 3. The metal support, wherein the oxide support contains fine particles, and 20% or more of the surface of the oxide cover is occupied by the fine particles exposed from the oxide coating. The film forming method according to claim 2. 4. The film forming method according to claim 1, 2 or 3, wherein the material of the metal support is any one of stainless steel, carbon steel and tantalum. 5. The film forming method according to claim 1, 2, 3, or 4, wherein the organic polymer is at least one selected from the group consisting of aromatic polyamide and aromatic polyimide.