JP4893323B2 - Method for producing a solution casting film - Google Patents

Description

  The present invention relates to a method for producing a solution film, which has few quality defects such as pinholes and can provide stable processability in, for example, a magnetic layer coating process or a vapor deposition process when a magnetic recording medium is produced.

In general, when an organic polymer that is in a molten state at a temperature higher than its melting point is discharged from a slit die as a molten film, a film is formed. However, since a polymer having a melting point close to the decomposition temperature or a melting point higher than the decomposition temperature is decomposed simultaneously with melting, the polymer is dissolved in an appropriate solvent, and the resulting polymer solution is cast on a support. Thereafter, the film is formed by a solution casting method for removing the solvent. Examples of the polymer formed by solution casting include cellulose, vinyl acetate, aromatic polyamide, aromatic polyimide, and the like. For example, para-aromatic polyamide films have been used in the field of magnetic recording, taking advantage of their heat resistance and high rigidity. However, in recent years, due to demands for higher density and miniaturization of magnetic recording media, further improvements have been made. There is a demand for higher functionality by improving surface quality.

  As a solution film forming method, a dry method, a wet method, a dry wet method, and the like are known. In the dry wet method, for example, Patent Document 1 exists as an example of an aromatic polyamide. In this document, after the solvent is removed until the polymer solution cast on the support is self-supporting, it is peeled off from the support, introduced into a wet process, and further contained in the film. It is described that an ionic inorganic compound and impurities are removed and a film is obtained through various processes. In addition, in the wet method, for example, in Patent Document 2 as an example of an aromatic polyamide, a polymer solution cast on a support is immersed in water together with the support and solidified, and then peeled off from the support and is placed in a water tank. It is described that a film is obtained through various steps after being introduced.

  However, due to the precise quality design in the magnetic recording media industry in recent years, equipment wear, which has not been taken up as a major problem in quality design, with the required reduction in film thickness and improvement in the film surface defect level. Defects in film quality due to dust in the air generated by the process, defects unique to the solution casting method, that is, films generated by dust on the support when a polymer solution that does not have self-supporting properties is discharged (cast) Although the necessity of improving the quality defect to a considerable level has arisen, the above-mentioned Patent Documents 1 and 2 do not disclose any effective means for these problems. Further, as disclosed in Patent Document 3, even though the countermeasure against the film defect on the magnetic recording surface side which is a film surface not in contact with the support as a countermeasure against dropout is mentioned, the side in contact with the support, that is, the exposed area of the support. No mention is made of the dust and foreign matter on the above developing into pinhole defects (through-holes) and having a significant effect on quality, and simply supplying clean air as described in Reference 3. It was impossible to solve these problems alone.

On the other hand, as means for supplying clean air into a sealed space and making the sealed space relatively positive with respect to its surroundings, for example, as disclosed in Patent Documents 4 and 5, etc. Although these technologies have been widely used in the past, each of these technologies has been made for the purpose of preventing dust and foreign matter from adhering to the product or a part thereof in a sealed space. There is no description or suggestion that dust, foreign matter, etc. on the exposed body area will develop into pinhole defects and have a significant impact on quality.
JP-A-4-139229 JP-A-2-28222 JP-A-8-279139 Japanese Utility Model Publication No. 6-46240 Japanese Patent Laid-Open No. 10-238833

Since the polymer solution used in the solution casting is not self-supporting when discharged (cast) onto the support, dust having a size or height greater than the thickness of the polymer solution to be cast on the support was present. In some cases, even if the polymer solution cast on the dust flows around the dust, or has a size or height less than or equal to the thickness of the cast polymer solution, the dust and the support The air sealed with the cast polymer solution expands due to the heat received from the support or others, and the polymer solution also flows to the periphery, which may lead to quality defects such as holes in the film. is there. Furthermore, as described in Patent Document 1, since the stretch ratio of solution casting is generally lower than that of melt casting, the thickness of the polymer solution cast on the support is cast on the melt casting support. Since the thickness is smaller than the thickness of the polymer, the above phenomenon appears particularly remarkably.

  In addition, with the reduction in film thickness and improvement in film surface defect level required due to precise quality design in the recent magnetic recording media industry, the size of dust causing film quality defects has decreased, and conventional solutions In the film production method, the quality defect of the film increases and the yield may be lowered.

  The object of the present invention is to solve the problems that have become apparent by improving the film surface defect level required due to precise quality design, and to provide stable workability in the subsequent magnetic layer coating and vapor deposition processes. It is providing the manufacturing method of a film forming film.

In order to achieve the above object, the present invention discharges a polymer solution containing a polymer and a solvent onto a rotating support, removes the solvent from the polymer solution until it has self-supporting property, and peels it from the support. A method for producing a solution-forming film for obtaining a film by supporting from the landing line of the polymer solution to the support to the peeling line from the support of the polymer solution toward the upstream side in the rotation direction of the support. At least a part of the region on the body (exposed region of the support) is covered with a chamber, the inside of the chamber is placed in a gas atmosphere of class 100 or less, and the space covered with this chamber is the surrounding space It is characterized by a positive pressure state.
A preferred embodiment of the present invention is characterized in that a gas of class 100 or less is obtained using a filter having a collection efficiency of 99.9% or more by a 0.3 micrometer counting method.
Furthermore, a preferred embodiment of the present invention is characterized in that dust on the support is removed using a suction means disposed on the support exposed area, and further, a cleaning means disposed on the support exposed area is used. And removing dust on the support.

  As will be described below, the present invention regulates the atmospheric environment around the support in order to suppress the adhesion of dust to the support, which can cause film quality defects, and thereby the dust adhesion speed on the support. Polyamide that solves the problems manifested by improving the film surface defect level required due to precise quality design, and provides stable workability in the subsequent magnetic layer coating and vapor deposition processes A method for producing a solution film-forming film such as a film can be provided.

  The polymer solution referred to in the present invention is a solution containing a polymer as a film raw material and a solvent, and the type of the solvent is not particularly limited as long as it dissolves the polymer. The concentration of the polymer in the polymer solution is generally 2 to 40 wt%, although it depends on the type of polymer. When the polymer concentration exceeds 40 wt%, the efficiency of removing the solvent is improved and the productivity is improved, but the film forming property may be lowered because the viscosity is increased. Further, when the polymer concentration is less than 2 wt%, the efficiency of removing the solvent may be lowered, and the viscosity may be further lowered, so that the polymer solution may not be held on the support. In addition to the polymer and solvent, the polymer solution may contain a lubricant, conductive particles, a plasticizer, an antioxidant, other additives, and the like depending on the purpose.

The polymer to which the method for producing the solution film-forming film of the present invention is applied is not particularly limited, but preferably, aromatic polyamide, aromatic polyimide, polyarylate, polycarbonate, cellulose polymer such as cellulose diacetate or cellulose triacetate, acetic acid Examples thereof include vinyl and polyvinyl alcohol, and aromatic polyamide is particularly preferable. Additives to be added other than the polymer and the solvent are not particularly limited. For example, particles may be present in the film for the purpose of imparting an appropriate roughness to the film surface. Examples of the types of particles include inorganic particles such as SiO ₂ , TiO ₂ , Al ₂ O ₃ , CaSO ₄ , BaSO ₄ , and CaCO ₃ , such as organic particles such as silicone particles, polyimide particles, and cross-linked co-polymers. Organic polymers such as polymer particles, crosslinked polyester particles, crosslinked polystyrene particles, and Teflon (registered trademark) particles, for example, conductive particles include inorganic particles such as carbon black, zeolite and other metal fine powders. From the viewpoint of utilizing the heat resistance of the group polyamide film, inorganic particles having excellent heat resistance are more preferable.

  The method for producing the solution film-forming film of the present invention will be described taking an aromatic polyamide film as an example. For example, if it is a polymer solution containing a polymer such as aromatic polyimide, polyarylate, polycarbonate, cellulose polymer such as cellulose diacetate and cellulose triacetate, vinyl acetate, polyvinyl alcohol and the like and a solvent for dissolving them, A film can be formed according to the production method described. For example, in the production of a cellulose acylate film that is useful as a polarizing plate protective film for use in liquid crystal display devices, etc., the cellulose acylate is dissolved in a solvent such as methyl acetate to form a casting dope, and then an endless band as a support. A method of casting the film on the film is known, and since it is an optical application, it is required to reduce film surface defects caused by foreign matter and dust.

  When the aromatic polyamide polymer is obtained from an acid chloride and a diamine, solution polymerization is performed in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), It can be synthesized by interfacial polymerization using an aqueous medium. When acid chloride and diamine are used as monomers in the polymer solution, hydrogen chloride is by-produced, so inorganic neutralizers such as calcium hydroxide, calcium carbonate, lithium carbonate, ethylene oxide, propylene oxide, ammonia, triethylamine Organic neutralizers such as triethanolamine and diethanolamine may be used. Moreover, when manufacturing an aromatic polyamide polymer by reaction of isocyanate and carboxylic acid, it is good to carry out in presence of a catalyst in an aprotic organic polar solvent.

  These polymer solutions may be used as a film-forming stock solution as they are, or the polymer may be once isolated and then redissolved in the above organic solvent or an inorganic solvent such as sulfuric acid to prepare a film-forming stock solution.

  Further, it is preferable to add particles in order to make fine irregularities on the surface of the film. Methods for adding the particles include, but are not limited to, a method in which the particles are sufficiently slurried in advance in a solvent and then added as a polymerization solvent or a dilution solvent, or a method in which the polymer solution is directly added after preparation.

  An inorganic salt such as calcium chloride, magnesium chloride, lithium chloride, or lithium nitrate may be added to the polymer solution as a dissolution aid.

  Prior to molding and coagulation, the polymer solution prepared as described above removes insoluble dust, foreign matters, etc. as much as possible by filtration, or removes gas such as air generated or entrained during dissolution. It is preferable to keep it. Degassing can be performed after adjusting the polymer solution once, or can be performed in several steps at the raw material preparation stage for adjustment, or the process can be kept under reduced pressure consistently. Can be achieved.

  The prepared polymer solution is formed into a film by a so-called solution casting method. In the solution casting method, the casting solution is cast on a support such as an endless belt or drum, and then dried, peeled off, and heat treated. There are a wet method in which post-heat treatment is performed, a dry wet method in which drying is performed on the support, and a wet process after peeling, and a semi-dry semi-wet method in which the support is dried and then introduced into the wet process. In order to obtain this film, a wet method, a dry wet method in which a polymer solution is cast on a support, or a semi-dry semi-wet method is preferable.

  Moreover, it is preferable that the rotating support body used for this invention has shapes, such as an endless belt and a drum. The material of the support is not particularly limited as long as it has acid resistance at least on the surface in contact with the polymer solution. For example, glass, hastelloy, tantalum, stainless steel subjected to chemical treatment such as plating treatment or hardening treatment, gold / platinum -A metal fluororesin plated with titanium nitride or the like is preferably used. Preferably, these materials are mirror-finished, and in that case, the flatness and surface properties of the film obtained by the method of the present invention are further improved.

  FIG. 1 is a partial schematic sectional view of a solution casting apparatus for realizing one embodiment of the present invention. In FIG. 1, a solution casting apparatus 20 is separated into a drying chamber 21 and a casting chamber 22 by a partition wall 23, and has a structure in which both chambers are isolated from each other as described later. The partition wall 23 is provided with an introduction slit 30 and a discharge slit 31 for entering and exiting the endless belt (support) 3. The casting chamber 22 includes a slit die 1 for supplying a polymer solution containing a polymer such as polyamide and a solvent, and a gas supply means 40 for supplying clean gas of class 100 or less into the chamber and the chamber 9. Is provided. The gas supply means 40 includes a filter 6, a gas supply pipe 12, and a chamber 9, and has a function of placing the inside of the cast chamber 22 and the chamber 9 in a clean gas atmosphere of class 100 or less. Support means 41 is provided across the drying chamber 21 and the casting chamber 22. The support means 41 includes an endless belt (support body) 3, a drive roll 4 connected thereby, and a support roll (not shown), and the endless belt (support body) 3 can move continuously. . In the casting chamber 22, a peeling roll 10 for peeling the polymer solution having self-supporting property from the endless belt (support) 3 is disposed adjacent to the drive roll 4.

  In the apparatus shown in FIG. 1, a polymer solution 2 containing a polymer such as polyamide and a solvent is discharged from a slit die 1 onto an endless belt (support) 3, and the introduction slit is moved along with the movement of the endless belt (support) 3. 30 is introduced into the drying chamber 21. In the drying chamber 21, the solvent is gradually removed from the polymer solution by heating means (not shown), and the polymer solution gradually acquires self-supporting properties and returns to the casting chamber 22 through the discharge slit 31. Thereafter, the polymer solution having self-supporting properties is peeled off by the peeling roll 10 to become a polymerized film, exits from the solution film forming apparatus 20, and is carried to a wet process which is the next process.

  Although not shown after the wet process, the solvent and impurities contained in the polymerization film are removed in each bath during the wet process. At this time, the polymerization film is conveyed through a nip roll at the bath entrance / exit and a roll in the bath. The film after the wet process is further dried and heat-treated to form a film. The film thus obtained is wound up to obtain an aromatic polyamide film (solution film forming film).

  In the above, an example using the gas supply means 40 (air used is air) is shown. However, if the inside of the cast chamber 22 and the chamber 9 is in a clean gas atmosphere of class 100 or less, the gas supply means 40 is used. May not be used. Further, even when the gas supply means 40 is used, an example in which the filter 6 is used as the gas supply means has been described. However, if a clean gas of class 100 or less can be obtained, the filter is not necessarily used. For example, an adsorbent bed such as a cooled zeolite column can be used. Moreover, when using a filter, it is preferable to use the filter which has the collection efficiency of 99.9% or more by the 0.3 micrometer counting method. For example, high-precision filtration filters such as a HEPA filter, a ULPA filter, and a PTFE filter can be used, but the present invention is not limited to these.

Here, class 100 is a standard indicating the cleanliness defined by FED-STD-209D, which is a US federal standard, and the number of particles in cubic feet represents a class with reference to particles of 0.5 μm or more. Class 100 represents the number of particles in a cubic meter with 10 X power / m ^{3 based} on particles of 0.5 μm or more, as defined in US Federal Standard FED-STD-209E. And When FED-STD-209D is converted to FED-STD-209E,
Class 100 = Class M3.5
It corresponds to. In the present invention, “a gas of class 100 or lower” refers to a gas that satisfies the standard of class 100 and a gas having a higher cleanliness (cleaner) than that.
Further, class 100 corresponds to cleanliness class 5 defined in JIS B9920: 2002.

  In addition, as an example of gas supply means into the cast chamber 22 and the chamber 9, the example in which gas is supplied from the gas supply pipe 12 is shown above. However, in order to supply rectified gas, a punching nozzle, slit-like nozzle, You may install the said filter in gas supply piping 12 exit location. Preferably, a punching type nozzle having an opening efficiency of 1% to 50%, more preferably 2% to 25% is used because the rectifying effect is high.

  Further, the direction of the gas to be supplied is not particularly limited, but is preferably a certain direction, and more preferably vertically downward, in order not to generate turbulent flow.

  The gas to be supplied is not limited as long as it is chemically stable with air, nitrogen, argon or the like, but it is preferable to use air in consideration of the running cost of the equipment.

  The temperature of the gas to be supplied from the gas supply pipe 12 into the casting chamber 22 and the chamber 9 is preferably in the range of 20 ° C. to the boiling point of the solvent + 20 ° C., more preferably 30 ° C. to the solvent. It is preferably in the range of the boiling point, and more preferably in the range of 50 ° C. to the boiling point of the solvent.

  Further, the endless belt of the polymer solution 2 from the landing line where the polymer solution 2 discharged from the slit die 1 lands on the endless belt (support) 3 toward the upstream side in the rotation direction of the endless belt (support) 3. The region on the endless belt (support) 3 from the (support) 3 to the peeling line to be peeled is always present in a state exposed to a gas of class 100 or less. In the present invention, this region is referred to as a support exposed region.

  Moreover, it is preferable to install the chamber 9 which can supply the gas below class 100 on the endless belt (support body) 3 in this support body exposure area | region. At this time, the chamber 9 only needs to cover at least a part of the support exposed region. Of course, it is not limited to the region described in FIG. 1, and it is also preferable that the size covers the entire support exposed region.

  Further, covering the exposed region of the support with the chamber 9 and making the space covered with the chamber 9 more positive than the surrounding space can suppress the entry of dust such as foreign matter and dust. Is preferable. At this time, the space covered with the chamber 9 is preferably higher than the surrounding space by 0.5 Pa or more, more preferably 2 Pa or more.

Further, it is preferable that the flow rate of the gas supplied from the chamber 9 is small in the range in which the above positive pressure state is maintained. When the gas flow rate is high, the speed of the gas supplied from the gas supply pipe 12 into the chamber 9 is increased. For example, dust that has not moved when the gas speed is low is generated at other locations. In some cases, the belt is moved on the endless belt (support) 3. From the above, in order not to move the dust generated in the chamber 9 with the supply gas, when the internal volume of the chamber 9 is V _C0 m ³ and the gas flow rate is V _C m ³ / min, V _C / V _C0 is preferably 100 or less, more preferably 60 or less, and even more preferably 25 or less.

The width of the chamber 9 preferably covers not only the width of the support exposed area but also the width of the endless belt (support) 3. Specifically, when the width of the chamber 9 is W [cm] and the width of the endless belt (support) 3 is W ₀ [cm], preferably W ₀ ≦ W ≦ W ₀ +100 cm, more preferably W _0. It is preferable to install the chamber 9 in a range of +5 cm ≦ W ≦ W ₀ +50 cm so as to cover the endless belt (support) 3.

  Further, in the present invention, dust refers to foreign matters, dust, and the like that are floating in the gas or are attached to the floor surface so as to be easily movable as the gas moves.

  Moreover, it is preferable that the pressure in the cast chamber 22 for supplying the gas is in a positive pressure state as compared with the pressure outside the solution casting apparatus 20. This is preferable because it can suppress the entry of foreign matter, dust and other dust into the cast chamber 22, and at this time, the pressure in the cast chamber 22 is 0.5 Pa or more higher than the pressure outside the solution casting apparatus 20. Is preferable, and 2 Pa or more is more preferable.

  In addition, it is preferable that the flow rate of the gas to be supplied be small in the range in which the positive pressure state is maintained. When the gas flow rate is high, the speed of the gas supplied from the gas supply pipe 12 into the cast chamber 22 is increased. For example, dust that has not moved when the gas speed is low, for example, generated elsewhere. May be moved onto the endless belt (support) 3.

From the above, in order not to move the dust generated in the cast chamber 22 onto the support with the supply gas, when the volume of the cast chamber 22 is V ₀ m ³ and the flow rate of air is Vm ³ / min, V / V ₀ is preferably 15 or less, more preferably 11 or less, and even more preferably 9 or less.

  In order to prevent the atmosphere in the drying chamber 21 from entering the cast chamber 22, the pressure in the drying chamber 21 is preferably equal to or lower than the pressure in the cast chamber 22. At this time, the pressure in the drying chamber 21 is preferably lower in the range of 0 to 2 Pa than the pressure in the cast chamber 22, and more preferably in the range of 0.1 to 1 Pa.

In order to forcibly remove the dust on the endless belt (support) 3 in the support exposed area, it is preferable to provide a forced exhaust duct 13 (suction means). At this time, the forced exhaust duct 13 is not limited to the region shown in FIG. 1, and may be disposed on the support exposed region. However, the dust is more likely to be disposed near the slit die 1. It is preferable in order to prevent adhesion on the support. In the support exposed region, when the suction port width L [cm] of the forced exhaust duct 13 is the support width W ₀ [cm], and the film width on the support is W _F [cm], It is preferable to install the suction port of the exhaust duct 13 so as to be further covered by the support so that W _F <L ≦ W ₀ . The amount of exhaust to the forced exhaust duct 13 is preferably 60 Nm ³ / min or less, and more preferably 20 Nm ³ / min or less, from the viewpoint of improving the film forming property. As further positive pressure condition described above holds, the difference between the exhaust amount air air charge ^is, it is preferable that more than 5 Nm 3 / min, and more preferably 20 Nm ³ / min or more.

Moreover, it is preferable to arrange a cleaning means on the endless belt (support) 3 in the support exposed area. Although not limited to FIG. 1, for example, as shown in FIG. 1, it is preferable to contact cleaning means 14 that is a cloth-like material impregnated with a liquid.
By providing the cleaning means in the support exposed area, it is possible to enhance the effect of removal by the suction means by removing and peeling off dust adhering to the support.

  The liquid to be used is preferably water or an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), but is not limited thereto. Absent. The cleaning means 14 to be used is preferably a nonwoven fabric made of cellulose or the like, but if it does not have a structure that makes the support surface deficient, it is further cloth-like regardless of the type as long as it does not dissolve in these liquids. There is no need. The pressure for pressing the cleaning means 14 against the support is preferably in the range of 1 to 1,000 Pa, more preferably in the range of 1 to 600 Pa, from the viewpoint that the surface state of the support can be satisfactorily maintained. In addition, this apparatus has the characteristic that it can also be used for the maintenance of a support body by the same operating conditions.

  In the present invention, the slit die 1 is an apparatus for discharging the polymer solution 2 in a sheet shape, and the material and shape are not particularly limited.

  In the present invention, the polymer solution peeled off by the peeling roll 10 and sufficiently removed from the solvent and having self-supporting property is referred to as a polymerization film 11.

  In the drying chamber 21, although not shown, the polymer solution 2 on the endless belt (support) 3 is dried by a method such as heating with hot air, heating the endless belt (support) 3, or infrared heating. Is removed. The drying conditions are 20 ° C. to the boiling point of the solvent in the polymer solution + 20 ° C., within 60 minutes, preferably 25 ° C. to the boiling point of the solvent in the polymer solution.

  The boiling point of the solvent of the present invention is the boiling point of the solvent in the case where there is only one kind of solvent in the polymer solution, and the boiling point of the solvent having the lowest boiling point when there are two or more kinds of solvents.

  In the wet process, the solvent and impurities contained in the polymerization film are removed. This bath is generally composed of an aqueous medium, and may contain an organic solvent, an inorganic salt, or the like in addition to water. In general, the water content is 30 wt% or more, preferably 50 wt% or more, and the bath temperature is usually 0-100 ° C. In this wet process, the polymerized film is immersed in such a bath under tension, and the inorganic compound in the polymerized film is extracted until it is less than 0.1 wt%, preferably 0.05 wt% or less. In this wet process, the polymerized film is conveyed through a nip roll at the bath entrance / exit and a roll in the bath.

  Next, heat treatment is performed. The heat treatment temperature and time are preferably 200 to 450 ° C. and preferably 1 to 60 minutes in order to improve physical properties such as mechanical properties and moisture absorption properties. Examples of the heat treatment include, but are not limited to, a method performed by heating a gas such as air or nitrogen, a method using a radiation heater, a method using both of them, and the like. Further, it is preferable to gradually cool the film after the heat treatment because surface properties and dimensional change rate can be improved. It is effective to cool at a rate of 100 ° C./second or less.

  The film thus obtained is wound up to obtain an aromatic polyamide film (solution film forming film).

  In the above description, an example in which an endless belt is used as a support has been described. Alternatively, for example, a single cast roll may be used. Specifically, the support means 41 including the endless belt (support body) 3, the drive roll 4, and the support roll (not shown) shown in FIG. 1 is configured using one cast roll.

  In addition, the method for producing a solution film according to the present invention may be a laminated film. For example, in the case of two layers, the prepared polymer solution is divided into two parts, and different particles are added to each other and then laminated. The same applies to the case of three or more layers. Examples of these lamination methods include lamination in a slit die, lamination in a composite tube, and a method in which one layer is once formed and another layer is formed thereon.

  Moreover, the thickness of the solution film-forming film obtained by the present invention is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.5 to 50 μm, and still more preferably in the range of 0.5 to 20 μm. It is. Accordingly, for example, it is possible to meet demands for higher density and smaller size of magnetic recording media and electronic equipment devices.

  Further, the tensile Young's modulus in at least one direction of the solution film obtained by the present invention is preferably 5 to 30 GPa, more preferably 7 to 25 GPa, still more preferably 10 to 20 GPa, and generally stretched. It is possible to increase the tensile Young's modulus by decreasing the temperature or increasing the draw ratio, and this can be achieved by adjusting and combining these conditions in a timely manner.

  By using such a tensile Young's modulus, for example, it becomes possible to withstand the tension applied during processing such as coating layer formation or vapor deposition layer formation and backcoat layer formation of a magnetic recording medium, which is advantageous in processing. This is preferable.

  If the Young's modulus in at least one direction of the solution film obtained by the present invention is 8 GPa or more, it may be tensified in the longitudinal direction or the width direction of the solution film. The degree of tensilization is not particularly limited. However, when characteristics such as elongation and tear resistance are taken into consideration, the tensile Young's modulus Emd in the longitudinal direction and the tensile Young's modulus Etd in the width direction are 0.3 ≦ Emd / Etd ≦ 3. It is practical to be in range.

  Further, the elongation in at least one direction of the solution casting film obtained by the present invention is desirably 10% to 80%, more preferably 20% to 70%, and further preferably 30% to 60%. In particular, it is possible to increase the elongation by raising the stretching temperature or lowering the stretching ratio, and this can be achieved by adjusting and combining these conditions in a timely manner. Thereby, for example, it is preferable that the tape of the magnetic recording medium can have appropriate flexibility.

  Moreover, the moisture absorption rate of the solution film-forming film obtained by the present invention is 0% to 5%, more preferably 0% to 3%, and still more preferably 0 to 2%. This can be achieved by adjusting. Accordingly, for example, a dimensional change due to a change in humidity, such as a tape of a magnetic recording medium or a flexible printed circuit, is small, and preferable electromagnetic conversion characteristics can be maintained.

  Further, the film-forming film obtained by the present invention preferably has a piece elongation of 1,000 mm width and 10 m length of ± 40 mm or less, more preferably ± 30 mm or less, still more preferably ± 20 mm or less. In addition, it is important to make the temperature condition in the film width direction uniform and to reduce the fluctuation of the temperature setting. This is preferable because, for example, good processability in the meandering prevention / magnetic layer forming step can be obtained when processing a magnetic recording medium or the like.

  Moreover, it is preferable that the strength F-5 value of the film at the time of extending | stretching 5% of the solution film-forming film obtained by this invention is 200 MPa-600 MPa. More preferably, it is 225 MPa to 580 MPa, more preferably 250 MPa to 550 MPa. Generally, it is possible to increase the strength F-5 value by decreasing the stretching temperature or increasing the stretching ratio. This can be achieved by timely adjustment and combination. By having such an F-5 value, for example, it is possible to withstand the tension applied during processing such as magnetic layer formation and backcoat layer formation step of the magnetic recording medium, which is advantageous in processing and preferable.

  Further, the heat shrinkage rate at 200 ° C. of the solution film obtained by the present invention is preferably −5% to 5%, more preferably −4% to 4%, and still more preferably −3% to 3%. Generally, it is possible to bring the thermal shrinkage rate close to zero by increasing the stretching temperature, decreasing the stretching ratio, or increasing the heat treatment temperature, and adjusting and combining these conditions in a timely manner. Can be achieved. Accordingly, for example, the bending due to the dimensional change of the film can be suppressed by the temperature at the time of forming the metal thin film of the vapor deposition type magnetic tape of the magnetic recording medium or the circuit forming temperature at the time of processing the flexible printed circuit.

  Further, the application of the solution film obtained by the present invention is not particularly limited. For example, a base film of a magnetic recording medium, a flexible printed circuit board, a base film of a printer ribbon, a dielectric of a capacitor, a solar Examples include battery separators, fuel cell separators, optical filters, and piezoelectric element supports.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, an Example shows an example of this invention and is not limited to this method.

(1) Evaluation Method for Number of Dust Captured [Pieces / Day] In Example 1, the number of dust captured by both methods (1a) and (1b) described later was measured. Further, α obtained in (1a) and β obtained in (1b)
α = 4 × 10 ² × β (A)
Since the correlation of the formula (A) is established, the number of dust supplemented in Example 1 is obtained by measuring the numerical value obtained by converting the β obtained in (1b) using the formula (A) three times, and calculating the averaged value. Described.

As for the number of dusts supplemented in Example 2 and later and in the comparative example, the numerical value obtained by converting β obtained by (1b) using the formula (A) three times and averaging the values is described.
(1a) Evaluation method of the number of dusts α [pieces / Day] on the support When the solution casting apparatus 20 is stopped and the polymer solution 2 is not present, the number of dusts in the chamber 9 is constantly settled under the solution casting conditions. After a certain period of operation (3 days in the present Example 1), the dust contained in a certain area on the support (a region surrounded by a width of 2 m and a length of 1 m in the present Example 1) is checked with the naked eye, All of the checked dust is photographed with a microscope having a constant magnification, and the total number α of dusts whose maximum diameter exceeds 20 μm is obtained.
(1b) Evaluation Method of Dust Number β [Piece / Day] on Simple Type Supporting Body A silicon wafer (diameter 1 in the vicinity of the supporting body where the solution film forming apparatus 20 operates and is exposed to the atmosphere air. / 4 inch) is installed, the captured dust is checked with the naked eye, and the total number of dusts β per day with a maximum diameter exceeding 20 μm is obtained by an optical microscope with a fixed magnification.

(2) Measurement of the number of dust in the air Measurement was performed using a dust measuring instrument having a particle diameter of 0.5 μm. A value obtained by multiplying the number of dusts per 0.1 ft ³ by 10 was taken as a measured value. In the measurement, a value obtained by multiplying a numerical value of 0.5 μm measured for 1 minute at a flow rate of 0.1 ft ³ / min three times and averaged 10 times is described. The measuring instrument used was a particle counter 227B manufactured by METONE.

(3) Film thickness After measuring and averaging the thickness of ten films stacked with a micrometer at 10 arbitrary locations, a value obtained by dividing the value by 10 was used. A Sony mate micrometer was used as a measuring instrument. Moreover, it measured in the environment of 23 +/- 2 degreeC and 65 +/- 5% RH.

(4) Tensile Young's modulus, elongation, F-5 value Measured using an Instron type tensile tester. The test piece was 10 mm wide and 100 mm long, the pulling speed was 200 mm / min, and the measured value was obtained by measuring five points and averaging them. Moreover, it measured in the environment of 23 +/- 2 degreeC and 65 +/- 5% RH. Note that the direction to be measured is the direction of 100 mm length. Tensilon UTM-4-100 manufactured by Toyo Baldwin Co. was used as a measuring instrument.

(5) Moisture absorption The weight of the film after drying at 200 ° C. for 1 hour is defined as W _0, and the weight of the film after moisture absorption at 20 ° C. and relative humidity of 75% for 48 hours is defined as W ₁ [(W ₁ − The moisture absorption rate (%) was expressed by a value obtained by multiplying W ₀ ) / W ₀ ] by 100.

(6) Heat shrinkage rate Marks are put into the film at intervals of 200 mm, and this is slit into a width of 10 mm perpendicular to the mark lines at intervals of 200 mm to obtain a measurement sample. Place the sample in a hot-air oven with a stable temperature of 150 ° C., take it out for 10 minutes and then remove it from the oven. Multiply [(Interval before heating−Interval after heating) / Interval before heating] by 100 to obtain the thermal shrinkage (% ). Three points were measured and the average value was taken as the measured value.

(7) Single elongation amount A film having a width of 1,000 mm is cut 10 m in the longitudinal direction and spread so as not to cause wrinkles on a horizontal surface. The yarn is stretched between both ends in the longitudinal direction on one end surface in the width direction, and the distance in the width direction between the film and the yarn at the 5 m point in the longitudinal direction (the midpoint in the longitudinal direction of the 10 m long film) is defined as a single elongation amount. . The case where the end face of the film bulges out from the yarn is defined as + side, and the case where the film end surface is retracted from the yarn is defined as-side.

(8) Number of pinholes For the evaluation of the number of pinholes, which is a film quality defect, the number of pinholes having a diameter of 100 μm or more was measured using a transmission type pinhole defect detector. The number of detection pinholes at 7,000 m ² (equivalent to 1,000 mm width × 7,000 m length) was used.

Example 1
In N-methyl-2-pyrrolidone (NMP), 2-chloroparaphenylenediamine corresponding to 85 mol% as an aromatic diamine component and 4,4-diaminodiphenyl ether corresponding to 15 mol% are dissolved, and the aromatic diamine is dissolved. 2-chloroterephthalic acid chloride corresponding to 99 mol% with respect to the component was added, and colloidal silica having a primary average particle size of 45 nm and an average cohesion of 10 was set to 0.2 wt% with respect to the aromatic diamine component before polymerization. And stirred for 2 hours to complete the polymerization. This was neutralized with lithium hydroxide to obtain an aromatic polyamide solution having a polymer concentration of 10 wt%, an intrinsic viscosity of 2.6, and a solution viscosity of 350 Pa · s (30 ° C.).

  This polymer solution was passed through a 1 μm cut filter, and then cast on the endless belt (support) 3 from the slit die 1 using the apparatus shown in FIG.

  The cast chamber 22 was filtered with a HEPA filter having a collection efficiency of 99.9% or more by a 0.3 micrometer counting method, and air adjusted to 35 ° C. was supplied to the cast chamber 22. The value of the air supply amount / the volume in the cast chamber 22 was 220 [1 / min], and the pressure in the cast chamber 22 to the outside of the solution film forming apparatus 20 was set to a positive pressure state of +2.5 Pa.

  The inside of the chamber 9 is filtered with a HEPA filter having a collection efficiency of 99.9% or more by a 0.3 micrometer counting method and supplied with air kept at 35 ° C., and the pressure inside the chamber 9 to the outside of the chamber 9 Was at a positive pressure of +0.1 Pa.

The forced exhaust duct 13 is set so that the exhaust flow rate is 4.8 [Nm ³ / min], the suction port width L of the forced exhaust duct 13 and the width W0 of the endless belt (support) 3 are −10 [cm]. The foreign matter, dust, dust, etc. adhering to the support were forcibly removed.

  A cellulose nonwoven fabric (cleaning means 14) impregnated with N-methylpyrrolidone (NMP) is brought into contact with the endless belt (support) 3 at a pressure of 300 Pa to force foreign matter, dust, dust, etc. adhering to the support. Removed.

  The polymer solution was heated on the endless belt (support) 3 with hot air at 140 ° C. for 2 minutes to remove the solvent, and the polymer solution having self-supporting property was continuously peeled from the endless belt (support). Next, it moved to the wet process, the polymerization film was introduce | transduced into the 50 degreeC water tank with the NMP density | concentration gradient, the remaining solvent, the inorganic salt produced | generated by neutralization, etc. were extracted. In this wet process, the film was stretched 1.15 times in the longitudinal direction. Next, moisture was dried at 245 ° C. for 30 seconds, followed by stretching 1.45 times in the width direction while applying heat at 245 ° C., and then cooled at 50 ° C./second to obtain 3.6 μm. An aromatic polyamide film was obtained.

  Table 1 shows the film forming conditions and the number of captured dust and the number of pinholes obtained by the evaluation means.

  Furthermore, when the tensile polyamide modulus, elongation, F-5 value, moisture absorption rate, thermal shrinkage rate, and half elongation of this aromatic polyamide film were measured by the above-mentioned evaluation means, they were excellent as shown in Table 2. there were.

(Example 2)
An aromatic polyamide film was obtained in the same manner as in Example 1 except that the cleaning means 14 was not used.

  Table 1 shows the film forming conditions and the number of captured dust and the number of pinholes obtained by the evaluation means.

  Furthermore, when the tensile polyamide modulus, elongation, F-5 value, moisture absorption rate, thermal shrinkage rate, and half elongation of this aromatic polyamide film were measured by the above-mentioned evaluation means, they were excellent as shown in Table 2. there were.

(Example 3)
An aromatic polyamide film was obtained in the same manner as in Example 1 except that the cleaning means 14 and the forced exhaust duct 13 were not used.

  Table 1 shows the film forming conditions and the number of captured dust and the number of pinholes obtained by the evaluation means.

  Furthermore, when the tensile polyamide modulus, elongation, F-5 value, moisture absorption rate, thermal shrinkage rate, and half elongation of this aromatic polyamide film were measured by the above-mentioned evaluation means, they were excellent as shown in Table 2. there were.

(Comparative Example 1)
An aromatic polyamide film was obtained in the same manner as in Example 1 except that the chamber 9, the forced exhaust duct 13, and the cleaning means 14 were not used.

  Table 1 shows the film forming conditions and the number of captured dust and the number of pinholes obtained by the evaluation means.

  The aromatic polyamide film was measured for tensile Young's modulus, elongation, F-5 value, moisture absorption rate, heat shrinkage rate, and half elongation by the above-mentioned evaluation means. As shown in Table 2, except for the number of pinholes. It was excellent.

(Comparative Example 2)
The value of the amount of air supplied into the cast chamber 22 / the volume of the cast chamber 22 is set to 60 [1 / min], the pressure outside the solution film forming apparatus 20 in the cast chamber 22 is set to a negative pressure state of −0.5 Pa, An aromatic polyamide film was obtained in the same manner as in Example 1 except that the chamber 9, the forced exhaust duct 13, and the cleaning means 14 were not used.

  Table 1 shows the film forming conditions and the number of captured dust and the number of pinholes obtained by the evaluation means.

  The aromatic polyamide film was measured for tensile Young's modulus, elongation, F-5 value, moisture absorption rate, heat shrinkage rate, and half elongation by the above-mentioned evaluation means. As shown in Table 2, except for the number of pinholes. It was excellent.

(Comparative Example 3)
The air adjusted to 35 ° C. is supplied into the cast chamber 22 without being filtered by a filter, and the value of the air supply amount into the cast chamber 22 / the volume of the cast chamber 22 is set to 220 [1 / min]. The pressure in the chamber 22 to the outside of the solution casting apparatus 20 is positive pressure of +2.5 Pa, and the fragrance is the same as in Example 1 except that the chamber 9, the forced exhaust duct 13 and the cleaning means 14 are not used. A group polyamide film was obtained.

  Table 1 shows the film forming conditions and the number of captured dust and the number of pinholes obtained by the evaluation means.

  The aromatic polyamide film was measured for tensile Young's modulus, elongation, F-5 value, moisture absorption rate, heat shrinkage rate, and half elongation by the above-mentioned evaluation means. As shown in Table 2, except for the number of pinholes. It was excellent.

It is a partial schematic sectional drawing of one Embodiment of the solution casting apparatus of this invention.

Explanation of symbols

1: Slit die 2: Polymer solution 3: Endless belt (support)
4: driving roll 6: filter 9: chamber 10: peeling roll 11: polymerization film 12: gas supply pipe 13: forced exhaust duct 14: cleaning means 20: solution film forming apparatus 21: drying chamber 22: cast chamber 23: partition wall 30 : Introduction slit 31: discharge slit 40: gas supply means 41: support means A: travel direction of endless belt (support) B: roll rotation direction C: polymerization film travel direction D: gas in forced exhaust duct 13 Direction of travel

Claims (4)

This is a method for producing a solution film-forming film in which a polymer solution containing a polymer and a solvent is discharged onto a rotating support, the solvent is removed from the polymer solution until it has self-supporting properties, and the film is peeled off from the support to obtain a film. And at least a region on the support (support exposed region) from the landing line of the polymer solution to the support to the peeling line from the support of the polymer solution toward the upstream side in the rotation direction of the support. Manufacture of a solution film-forming film that covers a part with a chamber, puts the inside of the chamber in a gas atmosphere of class 100 or less, and makes the space covered with the chamber a positive pressure state than the surrounding space. Method. The method for producing a solution casting film according to claim 1, wherein a gas of class 100 or less is obtained using a filter having a collection efficiency of 99.9% or more by a 0.3 micrometer counting method. The manufacturing method of the solution film-forming film of Claim 1 or 2 which removes the dust on a support body using the suction means distribute | arranged on the support body exposure area | region. The manufacturing method of the solution film-forming film in any one of Claims 1-3 which removes the dust on a support body using the cleaning means distribute | arranged on the support body exposure area | region.

Images