JP2022103041A - Manufacturing method of film - Google Patents

Abstract

To provide a manufacturing method of a film capable of early detecting a deformation of a width direction end leading to a breakage in a film manufacturing process.SOLUTION: A manufacturing method of a film has a process of continuously shooting an image or a video of at least one width direction end of a transportation film from a vertical direction to a surface of the transportation film peeled from a casting machine and verifying an occurrence of a deformation at the width direction end from the image or the video.SELECTED DRAWING: None

Description

The present invention relates to a film manufacturing method capable of detecting deformation of a widthwise end portion that may contribute to film tearing upstream of the manufacturing process.

The aromatic polyamide film and the aromatic polyimide film produced by the solution film forming method are used as engineering plastic films having heat resistance and high rigidity for various purposes such as magnetic recording material applications and circuit board applications.

Generally, in the solution film forming method, a polymer solution is poured from a base onto a support such as a drum, an endless belt, or a carrier film to form a film, and the solvent is dried from the film. A solvent extraction treatment device that extracts the solvent contained in the film by passing the film body (film body) through the liquid, and a film body (film body) in which the solvent is completely removed or the solvent concentration is reduced by this solvent extraction treatment device. ) Is spread in the width direction, and a winder that winds the film as a product obtained by this transverse stretching machine (tenter) into a roll shape is used.

In such a solution film forming method, if the end portion in the width direction of the conveyed film is deformed, the polymer solution is cast on the support to peel off the obtained film-like material, or in the stretching step. The problem is that the film breaks from the deformation. As a means for solving the problem, for example, a method for evaluating the deformation of the film edge after processing as a final product (Patent Document 1), and a method for evaluating the deformation of the film edge after stretching with a tenter (Patent Document 2). )It has been known.

Japanese Unexamined Patent Publication No. 2001-39623 Japanese Unexamined Patent Publication No. 2016-68310

However, in the methods described in Patent Documents 1 and 2, since the deformation of the widthwise end portion is detected at a relatively downstream stage in the film manufacturing process, it is difficult to detect the deformation of the film end portion at an early stage. In view of the above problems, it is an object of the present invention to provide a film manufacturing method capable of detecting deformation of the widthwise end portion leading to tearing at an early stage in the film manufacturing process.

In order to solve the above problems, the present invention has the following configuration.
(1) An image or a moving image of at least one widthwise end of the conveyed film is continuously photographed from a direction perpendicular to the surface of the conveyed film peeled off from the casting machine, and the image or the moving image is used to obtain the said image or moving image. A method for producing a film, which comprises a step of confirming the occurrence of deformation at an end portion in the width direction.
(2) The method for producing a film according to (1), which comprises evaluating the periodicity of the occurrence frequency of the deformation.
(3) The description according to (1) or (2), wherein the deformation is the deformation A when the deformation of 0.5 mm or more inward from the widthwise end of the transport film is defined as the deformation A. Film manufacturing method.
(4) The film manufacturing method according to claim 3, wherein the modification A comprises the following features 1 and 2.
Feature 1: The transport film is bent inward at the end in the width direction, so that the transport films are overlapped.
Feature 2: Deformation of 0.5 mm or more inward from the end in the width direction extends over 5 mm or more in the longitudinal direction of the transport film.
(5) The film manufacturing method according to (3) or (4), wherein an alarm is displayed at the timing when the occurrence of the deformation A is confirmed.
(6) The method for producing a film according to any one of (1) to (5), wherein the film is an aramid film.

According to the present invention, it is possible to detect deformation of the end portion in the width direction which causes tearing of the film in the film forming upstream process, and it is possible to provide a method for producing a film having excellent production efficiency.

Hereinafter, the method for producing the film of the present invention will be specifically described. In the method for producing a film of the present invention, an image or a moving image of at least one widthwise end of the conveyed film is continuously photographed from a direction perpendicular to the surface of the conveyed film peeled from the casting machine, and the image is described. Alternatively, it is characterized by having a step of confirming the occurrence of deformation at the widthwise end portion from the moving image.

The film manufacturing method of the present invention continuously captures an image or moving image of at least one widthwise end of the transport film from a direction perpendicular to the surface of the transport film peeled from the casting machine. Here, the casting machine refers to a device for casting a polymer solution from a base onto a support such as a drum, an endless belt, or a carrier film to form a film. "Peeling from the spreading machine" means that the film-like material is peeled off from the support such as the drum, the endless belt, and the carrier film of the spreading machine. The transport film refers to a film or film from the time it is peeled off from the casting machine until it is wound up as a final product, that is, a film in the manufacturing process after being peeled off from the casting machine. Here, the width direction means a direction orthogonal to the traveling direction (longitudinal direction) of the conveyed film in the film plane. Further, the "direction perpendicular to the surface of the transport film" means a case where the angle formed by the surface of the transport film is 80 ° to 90 °.

At the timing of continuously shooting an image or a moving image at at least one widthwise end of the transport film from a direction perpendicular to the surface of the transport film, the film-like material was peeled off from the casting machine to form a transport film. Although it is not particularly limited as long as it is downstream from the point, deformation of the widthwise end portion of the conveyed film may cause film tear in the downstream process, and therefore it is desirable to detect it at an early stage. From this point of view, it is desirable that it is performed immediately after being peeled off from the casting machine. Immediately after being peeled from the casting machine, it means the timing from the point of peeling from the casting machine to the step of stretching or drying the conveyed film. In addition, "continuously shooting an image or a moving image" means taking a real-time moving image or taking an image or a moving image at regular intervals while the production line is in operation.

In the method for producing a film of the present invention, an image or a moving image of at least one widthwise end of the transport film may be taken, but by detecting deformation at both widthwise ends at an early stage, the transport film may be captured. Deformation of the widthwise end can be detected throughout. Therefore, it is preferable to take an image or a moving image of both widthwise ends.

As a means for capturing an image or a moving image at the end in the width direction, for example, a camera or a video camera can be used. The camera and the video camera are not particularly limited as long as they can receive the light after the light of the illumination has passed through the end in the width direction, and the imaging may be monochrome or color.

In the method for producing a film of the present invention, in order to predict the occurrence of film tear, the occurrence of deformation at the end in the width direction is confirmed from an image or moving image. As a method of confirming the occurrence of deformation at the end in the width direction, a method of visually confirming from the obtained image or moving image, or a known image processing method (software), for example, confirmation by "AviUtl" which is a moving image editing software. Can be used. Further, CAE (Convolutional Auto Encoder), which is an unsupervised AI method, may be used.

In the film manufacturing method of the present invention, it is desirable to evaluate the periodicity of the occurrence frequency of deformation at the end in the width direction. This is because it may be possible to determine the source of the deformation at an early stage by evaluating the periodicity of the frequency of occurrence of deformation. For example, if it is known that the deformation occurs in the period of one circumference of the drum or the endless belt, it is possible to presume that the deformation is due to these abnormalities.

As a method for evaluating the periodicity of the occurrence frequency, for example, in the case of taking an image, a method of confirming the images obtained by taking pictures at regular time intervals and evaluating the presence or absence of periodicity is used. Can be done. When shooting a moving image, a method of evaluating the presence or absence of periodicity can be used by playing back the moving image and recording the time when the deformation occurs.

In the film manufacturing method of the present invention, it is preferable to confirm the occurrence of the deformation A when the deformation of 0.5 mm or more inward from the widthwise end of the conveyed film is regarded as the deformation A. Deformation of 0.5 mm or more inward from the widthwise end of the transport film means deformation with a dent of 0.5 mm or more from the widthwise end to the center side in the width direction. Since a deformation having a smaller dent than the deformation A is less likely to cause tearing of the transport film, it is possible to detect only the deformation that can be directly linked to the tearing of the transport film at an early stage by detecting only the deformation A. The larger the dent of the deformation A, the more easily it is directly linked to the tearing of the transport film, so the upper limit is not particularly specified, but it is about 3.5 mm from the viewpoint of the possibility of occurrence.

Whether or not the deformation generated at the widthwise end of the conveyed film corresponds to the deformation A can be evaluated by visual inspection of the obtained image or moving image or by analyzing these with a known image processing system.

Further, in the method for producing a film of the present invention, it is preferable that the modification A has the following features 1 and 2. Feature 1: The transport film is bent inward at the end in the width direction, so that the transport films are overlapped. Feature 2: Deformation of 0.5 mm or more inward from the end in the width direction extends over 5 mm or more in the longitudinal direction of the transport film. Here, the "overlap of the transport films" means a place where the transport films are bent upward or downward at the end in the width direction, and the transport films are doubled. Further, "a deformation of 0.5 mm or more inward from the widthwise end portion extends over 5 mm or more in the longitudinal direction of the conveyed film" means that the deformation of the film from the widthwise end portion to the inside is 0.5 mm or more (in other words). And, the section where the distance from the position of the end in the width direction where the deformation should have occurred to the end in the width direction where the deformation actually occurs is 0.5 mm or more) is continuously 5 mm in the longitudinal direction. It means that the deformation itself from the end portion in the width direction of the film to the inside is 5 mm or more in the longitudinal direction, but the section where the deformation to the inside reaches 0.5 mm or more is less than 5 mm is not applicable.

Deformation A that satisfies both of the above features 1 and 2 is more likely to lead to breakage of the conveyed film than other deformations. Therefore, by adopting such an embodiment, it is possible to detect the tearing of the conveyed film in the upstream direction, and it is possible to take necessary measures at an early stage. The method of narrowing down the form is not particularly limited, but for example, in addition to the method of detecting the above-mentioned deformation A, a supervised AI method CNN (Convolutional Neural Network) is used in combination to automatically discriminate and identify the form of the deformation. The method can be mentioned.

Further, in the film manufacturing method of the present invention, it is preferable that an alarm is displayed at the timing when the occurrence of deformation A is confirmed. With such an aspect, it is possible to confirm the deformation of the widthwise end portion leading to the tearing of the conveyed film at an early stage. The method of displaying the alarm is not particularly limited as long as the effect of the present invention is not impaired, and can be appropriately selected from means that can be visually or audibly recognized by humans. Specific examples include a method of displaying that an abnormal peak has occurred on a monitoring monitor, a method of sounding an alarm when the occurrence of an abnormal peak is confirmed, and the like. These methods may be used alone or in combination of two or more.

In the method for producing a film of the present invention, the film is not particularly limited as long as it is produced by solution film formation, and for example, an aramid film, an aromatic polyimide film, or the like can be used. Above all, from the viewpoint of tear propagation, it is preferable to use it in the production of an aramid film. Here, the aramid film refers to an aromatic polyamide film, and more specifically, a film containing an aromatic polyamide in an amount of more than 50% by mass and 100% by mass or less in all the components constituting the film.

Hereinafter, the method for producing a film of the present invention will be specifically described by taking an aromatic polyamide film produced by a solution film forming method as an example, but the method for producing a film of the present invention is limited thereto. is not.

Aromatic polyamides can be obtained, for example, from acid chlorides and diamines. In this case, it is aromatic by solution polymerization in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), or interfacial polymerization using an aqueous medium. Group polyamide can be synthesized. At this time, the polymer solution produces hydrogen chloride as a by-product, and in order to neutralize this, inorganic neutralizers such as calcium hydroxide, calcium carbonate, and lithium carbonate, as well as ethylene oxide, propylene oxide, ammonia, triethylamine, and triethanol. Organic neutralizers such as amine and diethanolamine can be used. Aromatic polyamides can also be obtained from the reaction of isocyanates with carboxylic acids, in which case the synthesis reaction is carried out in an aprotic organic polar solvent in the presence of a catalyst. These polymer solutions may be used as they are as a film-forming stock solution, or the polymer may be isolated once and then redissolved in the above-mentioned organic solvent or an inorganic solvent such as sulfuric acid to prepare a film-forming stock solution. good.

In order to obtain the aromatic polyamide film of the present invention, the intrinsic viscosity ηinh of the polymer (value measured at 30 ° C. with 0.5 g of the polymer as a 100 ml solution in 98% sulfuric acid) is 0.5 (dl / g). The above is preferable. In addition, when adding particles, there are methods such as a method in which the particles are sufficiently slurryed in a solvent and then used as a solvent for polymerization or a solvent for dilution, or a method in which the particles are directly added after preparing the membrane-forming stock solution. be.

Inorganic salts such as calcium chloride, magnesium chloride, lithium chloride, and lithium nitrate may be added to the film-forming stock solution as a solubilizing agent. Further, as the membrane-forming stock solution, the neutralized polymer solution may be used as it is, or the polymer may be isolated and then redissolved in a solvent. As the solvent, an organic polar solvent such as N-methyl-2-pyrrolidone, dimethylacetamide, or dimethylformamide is preferable because it is easy to handle, but a strongly acidic solvent such as concentrated sulfuric acid, concentrated nitrate, or polyphosphate may be used. The polymer concentration in the film-forming stock solution is preferably about 2 to 40% by mass.

Using the film-forming stock solution prepared in this way, film formation is performed by the so-called solution film-forming method. The solution film forming method includes a dry-wet method, a dry method, a wet method, and the like. When an inorganic salt is contained in the polymer solution, a wet step is required to extract the inorganic salt, and the dry-wet method is used. When forming a film by a dry-wet method, the undiluted solution is extruded from a base onto a support (for example, an endless belt) to form a film, and then the solvent is scattered from the sheet so that the film has a self-supporting polymer concentration (for example, an endless belt). PC) Dry to 35-60% by mass (dry step).

After the film after the dry step is cooled, it is peeled off from the support and introduced into a casting machine (wet bath) in the next wet step, where desalting and solvent removal are performed. The solvent composition of the wet bath is not particularly limited as long as it is a poor solvent for the polymer, but water or an organic solvent / water mixed system can be used. At this time, in order to reduce impurities in the film, the composition ratio of the organic solvent / water mixture system (the following numerical values are based on mass) is organic solvent / water = 70/30 to 0/100, preferably 60. It is / 40 to 30/70. Further, the bath temperature is preferably 40 ° C. or higher. Although the wet bath may contain an inorganic salt, it is preferable to finally extract the solvent and the inorganic salt contained in the film with a large amount of water.

The film that has passed through the wet process is peeled off from the casting machine and conveyed. Images or moving images of at least one widthwise end of the conveying film are continuously photographed from a direction perpendicular to the surface of the conveying film, and the occurrence of deformation at the widthwise end is confirmed from the images or moving images. At this time, it is preferable to evaluate the periodicity of the occurrence frequency of the deformation, and it is preferable that the deformation to be confirmed is the above-mentioned deformation A.

Subsequently, the transport film is dried and heat-treated in the tenter, and it is preferable to dry the transport film until the solvent content in the transport film is less than 5% by mass by the time the heat treatment is performed in the tenter. If the heat treatment step is started with the solvent content of 5% by mass or more, uneven heat treatment is likely to occur, unevenness may occur in the physical properties in the width direction of the film, and the film may be easily broken during the stretching step described later. be. It is more preferable that the solvent content is low, and it is desirable that the solvent is completely dried to around 0% by mass.

The film formed as described above is stretched in order to improve mechanical properties and dimensional stability. For stretching, a sequential biaxial stretching method in which the sheet is first stretched in the longitudinal direction and then in the width direction, or first in the width direction and then in the longitudinal direction, or a simultaneous biaxial stretching method in which the longitudinal and width directions are simultaneously stretched is used. be able to. These stretching methods are well known as stretching methods in melt film formation performed by film formation of polyethylene, polypropylene, polyester, etc., but in the case of a film obtained by solution film formation as in the present invention, Since the sheet contains a solvent and a wet bath component, and since they are a process including movement to the outside of the sheet, it is preferable to adopt the method described later in order to obtain the target film.

As the stretching method, the sequential biaxial stretching method is preferable from the viewpoint of equipment and operability. As the stretching conditions, it is necessary to select appropriate conditions depending on the polymer composition and the like, but the stretching ratio in the longitudinal direction of the sheet is 1.0 to 1.5 times, and the stretching ratio in the width direction is 1.2 to 2. It is preferable that the value is 0.0 times in order to obtain the desired dimensional stability. The stretching temperature and time are preferably 270 ° C. or higher and 3 seconds or longer, and more preferably 270 to 320 ° C. and 3 seconds or longer. If the stretching temperature is less than 270 ° C., crystallization may be insufficient and dimensional characteristics such as sufficient hygroscopicity and tensile strength may not be obtained. If the stretching temperature exceeds 320 ° C., the crystallinity increases too much, so that the film becomes brittle and the film may be easily torn. Further, the solvent content in the sheet at the time of stretching is preferably less than 5% by mass. It is also preferable to slowly cool the film after stretching or heat treatment, and cooling at a rate of 50 ° C./sec or less is effective in reducing the heat shrinkage rate.

The aromatic polyamide film in the method for producing a film of the present invention may be a single-layer film or a laminated film. For example, in the case of a two-layer structure, one example is a method in which a polymerized aromatic polyamide solution is divided into two, different particles are added to each, and then the layers are laminated. The same applies to the case of three or more layers. Examples of these laminating methods include laminating in a base, laminating in a composite pipe, and once forming one layer and then forming another layer on it. Further, the aromatic polyamide film obtained as described above may be subjected to various treatments such as corona discharge treatment, plasma treatment, dust removal treatment, and reheat treatment.

The aromatic polyamide film thus obtained is wound as an intermediate product roll or a final product roll after cutting and removing the edge portions at both ends in the width direction, if necessary. When wound as an intermediate product roll, a biaxially oriented polyester film can be further unwound from the intermediate product roll and cut in parallel with the longitudinal direction to obtain a desired width to obtain a wound final product roll. .. The final product roll obtained from one intermediate product roll may be one or a plurality of rolls.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[Measurement and evaluation method]
The measurements and evaluations shown in the examples were performed under the following conditions.

(1) Imaging of film edge The edge of the transport film peeled off from the belt is irradiated with coaxial epi-illumination LED light (OPX-S50W manufactured by Optex FA), and the positively reflected light is captured by a camera (acA640-300 gm manufactured by Basler). Then, the deformation generated on the roll was detected from the change in the amount of imaging light by image processing, and the film deformation at the film edge upstream of the film formation was captured. As the image processing method, CAE (Convolutional Auto Encoder), which is an unsupervised AI method, was used. This is a method of building a restorer that learns an image of a normal edge state and restores normal data. In this method, the restoration accuracy drops for abnormal data with deformation, so it is possible to distinguish between normal and abnormal by comparing the error between the input image and the restored image, and it is possible to identify the abnormal data. .. The imaging interval was set to 20 ms, and the edge image was saved when an abnormality was detected.

(2) Relationship between the presence / absence of deformation, size, periodicity and occurrence of film tear at the end in the width direction of the film (2) Presence / absence of deformation and size (deformation from the end in the width direction) from the images captured by the method described in (1). The maximum value of the size of the film) and the periodicity were determined, and the deformation in which the film was torn was identified. It was also evaluated whether or not the following features 1 and 2 were satisfied for the deformation.
Feature 1: The transport film is bent inward at the end in the width direction, so that the transport films are overlapped.
Feature 2: Deformation of 0.5 mm or more inward from the end in the width direction extends over 5 mm or more in the longitudinal direction of the transport film.

(3) Production of film (3-1) Aromatic polyamide solution A
2-Chloroparaphenylenediamine (hereinafter CPA) and diphenyl ether (hereinafter DPE) are dissolved in N-methyl-2-pyrrolidone (hereinafter NMP) so that the molar ratio is 85:15, and this solution is filtered with an accuracy of 1. After filtering through a filter made of 0 μm polypropylene, the mixture was transferred to a polymerization tank. Chloride chloroterephthalic acid chloride (hereinafter referred to as CTPC) passed through a filter made of polypropylene having a filtration accuracy of 1.0 μm was added to this so that the total of CPA and DPE: CTPC was 100: 98.5 (molar ratio). Furthermore, before polymerization, 5.0 parts by mass of polyether salphon (Sumika Excel 5400P manufactured by Sumitomo Chemical Co., Ltd.) with respect to the aromatic diamine component, and colloidal silica having an average primary particle size of 80 nm as the aromatic diamine component. The mixture was added in an amount of 0.45 parts by mass and stirred at 30 ° C. or lower for 2 hours to obtain a polymerized polymer solution. Next, lithium carbonate was added to the polymerized polymer solution for 4 hours of neutralization. The amount of lithium carbonate added at this time was adjusted so that the ratio of hydrogen chloride to lithium carbonate in the solution was 100: 98.5 (molar ratio). Further, triethanolamine was added to the polymerized polymer solution and stirred for 1 hour to obtain an aromatic polyamide solution A having a polymerized polymer concentration of 10.8% by mass. The amount of triethanolamine added at this time was adjusted so that the ratio of hydrogen chloride to triethanolamine in the solution was 100:10 (molar ratio).

(3-2) Aromatic polyamide solution B
CPA and DPE were dissolved in NMP so as to have a molar ratio of 85:15, and this solution was filtered through a filter made of polypropylene having a filtration accuracy of 1.0 μm and then transferred to a polymerization tank. CTPC passed through a filter made of polypropylene having a filtration accuracy of 1.0 μm was added to this so that the total of CPA and DPE: CTPC was 100: 98.5 (molar ratio). Next, lithium carbonate was added to the polymerized polymer solution for 4 hours of neutralization. The amount of lithium carbonate added at this time was adjusted so that the ratio of hydrogen chloride to lithium carbonate in the solution was 100: 98.5 (molar ratio). Further, 0.3 parts by mass of silica having an average primary particle size of 16 nm (“AEROSIL” (registered trademark) R972 type manufactured by Aerosil Japan Co., Ltd.) was added to the polymer, and the mixture was stirred for 1 hour. Then, triethanolamine was added to the polymerized polymer solution and stirred for 1 hour to obtain an aromatic polyamide solution B having a polymerized polymer concentration of 10.8% by mass. The amount of triethanolamine added at this time was adjusted so that the ratio of hydrogen chloride to triethanolamine in the solution was 100:10 (molar ratio).

(3-3) Film formation Next, the aromatic polyamide solution A is passed through a metal fiber filter made of stainless steel having a filtration accuracy of 1.2 μm, and the aromatic polyamide solution B is made of stainless steel having a filtration accuracy of 5.0 μm. After passing through a metal fiber filter, it was laminated inside the base. At this time, the lamination ratio (thickness ratio) of the aromatic polyamide solutions A and B was set to 1: 1. Next, the laminated aromatic polyamide solution was cast on a mirror-shaped stainless steel belt provided in a casting machine, and heated on a running belt with hot air at 180 ° C. for 2 minutes to evaporate the solvent. The membrane was continuously peeled off the belt. Next, a film body was introduced into the tank of the solvent extraction treatment apparatus, and while water extraction of the residual solvent and the inorganic salt generated by neutralization was performed, 1.15 times stretching (longitudinal stretching) was performed in the longitudinal direction. Then, the vertically stretched film body was gripped by a clip of a transverse stretching machine, dried and heat-treated at 245 ° C. for 1.5 minutes, and further stretched 1.43 times in the width direction (transverse stretching). .. Further, the film was slowly cooled at a rate of 20 ° C./sec, the film edge was removed, and the film was wound onto a core under the condition of an oscillation width of 60 mm to obtain an aromatic polyamide film having an average thickness of 3.6 μm.

(Example 1)
Based on the above film production, the widthwise end of the conveyed film peeled off from the belt of the casting machine was imaged by the method (1), and deformation with a deformation of 0.5 mm or more and periodicity was detected. did. Further, from the detected deformations, those satisfying both the features 1 and 2 described in "(2) Relationship between presence / absence of deformation, size, periodicity and occurrence of film tear at the end in the width direction of the film" were detected. From this deformation, film tearing occurred, and the process of film tearing could be identified.

(Examples 2 to 5)
Deformation was detected in the same manner as in Example 1 except that the deformation of the detection target was as shown in Table 1, and the presence or absence of film tear was evaluated. The evaluation results are shown in Table 1.

(Comparative Example 1)
Based on the above film production, the widthwise end portion of the conveyed film after lateral stretching was imaged by the method (1), and the presence or absence of deformation of the film widthwise end portion was evaluated. In the film after lateral stretching, the end portion in the width direction was curled inward due to the heat history, and it was not possible to accurately grasp the presence or absence of deformation. In addition, film tearing occurred in the process upstream of lateral stretching, and it was not possible to evaluate the occurrence of film tearing due to deformation (Table 1).

According to the present invention, by using the method for detecting deformation of the edge of the film of the present invention in the film manufacturing process, deformation of the film can be detected at an early stage and necessary measures can be taken, and defective products can be efficiently detected. Can be eliminated. Therefore, by using the film manufacturing method of the present invention, high quality film can be efficiently produced.

Claims (6)

An image or a moving image of at least one widthwise end of the conveying film is continuously photographed from a direction perpendicular to the surface of the conveying film peeled from the casting machine, and the widthwise end of the conveying film is taken from the image or the moving image. A method for producing a film, which comprises a step of confirming the occurrence of deformation in a portion. The method for producing a film according to claim 1, wherein the periodicity of the occurrence frequency of the deformation is evaluated. The film manufacturing method according to claim 1 or 2, wherein the deformation is deformation A when a deformation of 0.5 mm or more inward from the widthwise end of the conveyed film is defined as deformation A. .. The method for producing a film according to claim 3, wherein the modification A comprises the following features 1 and 2.
Feature 1: The transport film is bent inward at the end in the width direction, so that the transport films are overlapped.
Feature 2: Deformation of 0.5 mm or more inward from the end in the width direction extends over 5 mm or more in the longitudinal direction of the transport film. The film manufacturing method according to claim 3 or 4, wherein an alarm is displayed at the timing when the occurrence of the deformation A is confirmed. The method for producing a film according to any one of claims 1 to 5, wherein the film is an aramid film.