Method for producing film

Abstract

[Problem] To provide a method for producing a film such that during the production of the film, no breakage, tearing or anomalies in external appearance are caused to the film not only at the central part of the film but also at both fixed edges of the film or the vicinity thereof. [Solution] This method for producing a film comprises: a step A in which fixtures are set at both edges in the width direction of one surface of a not-yet-heat-treated film, and the not-yet-heat-treated film is fixed in place using the fixtures; a step B in which hot air is blown onto both surfaces of the not-yet-heat-treated film; and a step C in which the not-yet-heat-treated film is conveyed. In the step B, the speed of the hot air blown onto the surface where the fixtures are not set is greater than or equal to the speed of the hot air blown onto the surface where the fixtures are set.

Description

Film manufacturing method

[0001] The present invention relates to a method for producing a film.

[0002] Conventionally, in a film manufacturing process, a tenter-type conveying device is known in which, when the film is conveyed, dried, heat-treated, etc., both ends of the film in the width direction are gripped with a number of pins or clips, thereby applying tension to the film in the width direction while the film is conveyed (see, for example, Patent Document 1).

[0003] There are several types of tenter conveying devices. Among these, pin tenter conveying devices grip the film by piercing both ends of the film with multiple pins along the machine direction. The pins are arranged on a pin seat that is held by a pair of moving chains arranged parallel to each other. The film is gripped and conveyed by these pins, but if the film has low tear strength, it may break during conveyance.

[0004] To solve this problem, it has been proposed to overlap a film with high tear strength as a reinforcing film on the gripping portion (edge) of a film with low tear strength (see, for example, Patent Document 2).

[0005] Japanese Patent Publication No. 39-29211 Publication No. 11-254521

[0006] However, the method of Patent Document 2 involves overlapping a film with low tear strength with a film with high tear strength, resulting in a significant waste of raw materials. Furthermore, when using such a conveying device to apply hot air to a film to promote a chemical reaction or volatilize a solvent, the hot air reaches both ends of the film held by the pins less easily than the central portion because the pin sheet blocks the hot air. Therefore, even when a film with high tear strength is overlapped at both ends, the chemical reaction may remain incomplete or the film may remain undried near the ends, resulting in breaks, tears, and abnormal appearance at or near the gripped portions. If breaks or tears occur at both ends of the film, the film may detach from the pin gripping portion during conveyance, resulting in the film becoming stuck in the conveying device and preventing the desired film from being obtained. Even if such sticking in the conveying device does not occur, tears or tears at both ends of the film make it difficult to maintain the film in an appropriately tensioned state, resulting in wrinkles throughout the film and other degradation of quality beyond the ends. Furthermore, if tears or abnormal appearance occur near both ends of the film, it becomes necessary to cut further to the center when cutting the gripping portion, which causes production loss.

[0007] This problem is likely to occur in systems where chemical reactions and solvent evaporation occur simultaneously during transport, such as polyimide films obtained by heat-treating a polyimide precursor film containing a certain amount of solvent while transporting it. In particular, for transparent, highly heat-resistant films, it may be necessary to select a molecular structure that is brittle and prone to tearing in order to ensure the required physical properties, creating a bottleneck in solving the problem.

[0008] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a film manufacturing method that can more effectively suppress breakage, tearing, and abnormal appearance at and near both ends of a film when the film is fixed at both ends and transported using a tenter-type transport device.

[0009] The present inventors have conducted extensive research to solve the above problems and have completed the present invention, which provides the following preferred embodiments.

[0010] [1] A method for producing a film, comprising: Step A: installing fasteners at both widthwise ends of one side of a pre-heat-treatment film and fastening the heat-treated film with the fasteners; Step B: blowing hot air onto both sides of the pre-heat-treatment film; and Step C: transporting the pre-heat-treatment film, wherein in Step B, the air speed of the hot air blown onto the side not equipped with fasteners is equal to or greater than the air speed of the hot air blown onto the side equipped with fasteners. [2] The method for producing a film according to [1], wherein in Step B, the air speed of the side not equipped with fasteners is 1.1 times or more the air speed of the side equipped with fasteners. [3] The method for producing a film according to [1] or [2], wherein the fasteners are pin sheets. [4] The method for producing a film according to any one of [1] to [3], wherein the film is a polyimide film. [5] The method for producing a film according to [4], wherein the polyimide film is a transparent polyimide film. [6] A film manufacturing apparatus comprising: a fixing mechanism A that installs fixing devices at both widthwise ends of one side of a pre-heat-treated film and fixes the heat-treated film with the fixing devices; an air blowing mechanism B that blows hot air to both sides of the pre-heat-treated film; and a transport mechanism C that transports the pre-heat-treated film, wherein the air blowing mechanism B blows the hot air at a speed equal to or faster than the speed of the hot air blown to a side where the fixing devices are not installed. [7] The film manufacturing apparatus according to [6], wherein the air blowing mechanism B blows the air at a speed 1.1 times or more on a side where the fixing devices are not installed than the speed of the air blowing on a side where the fixing devices are installed. [8] The film manufacturing apparatus according to [6] or [7], wherein the fixing devices are pin sheets. [9] The film manufacturing apparatus according to any of [6] to [8], wherein the film is a polyimide film.

[10] The film manufacturing apparatus according to [9], wherein the polyimide film is a transparent polyimide film.

[0011] According to the present invention, a method for producing a film can be provided that prevents breakage, tearing, and abnormal appearance not only in the center of the film but also in both fixed ends and their vicinity.

[0012] If breaks or tears occur at both ends of the film, the film will come off the film fixing structure (e.g., pins) during transport, causing the film to become stuck in the transport device and making it impossible to obtain the desired film. Even if such sticking in the transport device does not occur, tears or breaks at both ends of the film make it difficult to maintain the film in an appropriately tensioned state, resulting in wrinkles throughout the film and other factors that can reduce quality beyond the ends. Furthermore, if tears or abnormal appearance occur near both ends of the film, cutting the fixing portion (gripping portion) requires cutting further toward the center, resulting in production losses.

[0013] In contrast, according to the present invention, film transport problems caused by breakage and tearing at both ends of the film can be suppressed. Furthermore, wrinkles in the central portion caused by abnormalities at both ends can also be suppressed, allowing for the provision of a film of stable quality. Furthermore, since breakage, tearing, and abnormal appearance near both ends of the film can also be suppressed, the area of ​​both ends to be cut can be reduced, thereby reducing production loss. Furthermore, by using the method of the present invention, excessive heat is not applied to the central portion of the film, so no abnormalities occur in the central portion of the film, allowing for the provision of a film of stable quality.

[0014] 1 and 2, the hot air is not blown out from three points above and below, but is blown out evenly across the entire width of the air outlet. In addition, multiple air outlets are arranged in the film transport direction.

[0015] Hereinafter, embodiments of the present invention will be described. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made within the scope that does not depart from the spirit of the present invention.

[0016] In the production of a film, a film before heat treatment may be passed through a heating furnace to volatilize the organic solvent, cause a chemical reaction, or improve various physical properties. Here, the film used to volatilize the organic solvent is a film before drying, and the film used to cause a chemical reaction is a precursor film (green film). In this specification, these are collectively referred to as the film before heat treatment.

[0017] When passing the pre-heat-treatment film through a heating furnace in this manner, it is necessary to install fixtures at both widthwise ends of one side of the pre-heat-treatment film and fix the heat-treated film with the fixtures (Step A). ​​The fixing method is not particularly limited. When heat-treating during transport, a tenter-type transport device is generally used. When using a tenter-type transport device, it is preferable to fix both ends of the pre-heat-treatment film by piercing them into multiple pins of a pin tenter-type transport device. It is preferable to fix the pre-heat-treatment film only at both ends. Fixing only at both ends prevents air from being blocked from being blown to areas other than both ends of the pre-heat-treatment film (e.g., the center). When heating the pre-heat-treatment film in the tenter-type transport device, a hot air generating mechanism is often used as a heat source. The hot air generating mechanism blows hot air onto the side of the pre-heat-treatment film where the fixtures are not installed (e.g., the upper surface of the pre-heat-treatment film) and the side of the pre-heat-treatment film where the fixtures are installed (e.g., the lower surface of the pre-heat-treatment film), thereby heating the film (Step B). Heat treatment can volatilize the organic solvent in the pre-heat treatment film, cause chemical reactions, and improve various physical properties. It is necessary to make the speed of the hot air on the non-fixing device side of the pre-heat treatment film the same as or faster than the speed of the hot air on the fixing device side. Here, blowing hot air onto the pre-heat treatment film is also referred to as heat treatment.

[0018] Next, the pre-heat-treated film is transported while the heat treatment is being carried out (step C).

[0019] FIG. 1 is an explanatory diagram schematically illustrating the state of a pre-heat-treatment film during transport in the present invention. The pre-heat-treatment film is transported from the back side of the page to the front side (or from the front side to the back side). A pin sheet 11 (film fixing device) is placed on the fixing device installation surface (lower surface) of the pre-heat-treatment film 1, and both ends of the pre-heat-treatment film 1 are fixed (gripped) by being pierced by pins 11a (film fixing structure) provided on the upper surface of the pin sheet 11. The pre-heat-treatment film 1 is then heat-treated in this state. The heat treatment is performed by simultaneously blowing hot air 31 generated from a hot air outlet 21 provided on the non-fixing device installation side (upper surface) of the pre-heat-treatment film 1 and hot air 32 generated from a hot air outlet 22 provided on the opposite fixing device installation side (lower surface) onto both the upper and lower sides of the pre-heat-treatment film 1. At this time, the hot air 31 is blown onto the pre-heat treatment film 1 without being blocked by the pin sheet 11, but part of the hot air 32 is blocked by the pin sheet 11 and does not reach the pre-heat treatment film end 1b. Like the hot air 31, the hot air 32 is blown onto the pre-heat treatment film central portion 1a without being blocked. Normally, this would cause the pre-heat treatment film end 1b to be in an incomplete chemical reaction or an incompletely dried solvent state. Furthermore, if the total volume of the hot air 31 and the hot air 32 is increased in an attempt to increase the amount of hot air 31 (hot air not blocked by the pin sheet 11) blown onto the pre-heat treatment film end 1b, excessive heat will be applied to the film central portion 1a, which will become the final product, causing abnormalities such as cloudiness, yellowing, and breakage due to over-drying. However, according to the present invention, by making the speed of hot air 31 the same as or greater than the speed of hot air 32 without changing the total air volume of hot air 31 and hot air 32, the proportion of hot air 32 (hot air blocked by pin sheet 11) is reduced and the proportion of hot air 31 (hot air not blocked by pin sheet 11) is increased, so that hot air can be applied to film end 1b more efficiently, and the above-mentioned condition at pre-heat treatment film end 1b can be avoided without causing the above-mentioned abnormality in film center 1a that will become the product. In Figure 1, the side of pre-heat treatment film 1 facing hot air outlet 21 is the surface where the fixture is not installed, and the side facing hot air outlet 22 is the surface where the fixture is installed.

[0020] In the present invention, as shown in Fig. 2, a pin tenter 11 may be placed on the upper surface of the pre-heat treatment film, and both ends of the pre-heat treatment film 1 may be fixed by piercing them into pins 11a provided on the lower surface of the pin sheet 11. In this case, the wind speed of the hot air 31 on the non-fixing device installed side (lower surface) of the pre-heat treatment film 1 is set to be the same as or faster than the wind speed of the hot air 32 on the fixing device installed side (upper surface) of the pre-heat treatment film 1. In Fig. 2, the side of the hot air outlet 22 of the pre-heat treatment film 1 is the fixing device installed side, and the side of the hot air outlet 21 is the non-fixing device installed side.

[0021] The pin tenter conveying device generally has a large number of pins arranged on a pin seat fixed (held) by a pair of moving chains arranged parallel to each other. The pins arranged on this pin seat may be on the upper or lower surface of the pin seat. The arrangement of the pins is not particularly limited, and conventionally known arrangements can be used.

[0022] The temperature of the hot air blown onto the non-fixing device installation surface and the fixing device installation surface of the pre-heat-treatment film is preferably 80°C or higher and 500°C or lower to promote solvent evaporation and chemical reaction. It is more preferable that the temperature be 120°C or higher, even more preferably 150°C or higher, and particularly preferably 200°C or higher, because this facilitates removal of the solvent contained in the pre-heat-treatment film and, if the pre-heat-treatment film is a polyimide precursor (polyamic acid), facilitates imidization (thermal imidization). Furthermore, it is more preferable that the temperature be 450°C or lower, even more preferably 400°C or lower, and particularly preferably 380°C or lower, because this minimizes thermal damage to the film. Within the above range, film breakage and tearing during transport are minimized, resulting in improved film quality. The hot air temperatures of the non-fixing device installation surface and the fixing device installation surface may be the same or different, but it is preferable that they be the same temperature to simplify the device. The change in the temperature of the hot air during film transport is not particularly limited, and may be designed so that multiple heating furnaces are connected to change the temperature of the hot air in stages, or so that the temperature of the hot air gradually increases or decreases in the transport direction. When heat treatment is performed in multiple heating furnaces, the number of heating furnaces is preferably 2 to 10, more preferably 3 to 8, and even more preferably 4 to 6. By performing heat treatment in multiple heating furnaces, the film before heat treatment can be dried or thermally imidized in stages, thereby improving the quality of the film.

[0023] The wind speed of the hot air blown onto the non-fixing device surface of the pre-heat-treatment film is preferably 0.5 m / s or more and 15 m / s or less. The hot air reaches the pre-heat-treatment film sufficiently, making it easier to remove the solvent contained in the pre-heat-treatment film, and, if the pre-heat-treatment film is a polyimide precursor (polyamic acid), making it easier to imidize (thermo-imidize). Therefore, the wind speed is more preferably 1 m / s or more, even more preferably 1.5 m / s or more, even more preferably 2 m / s or more, and particularly preferably 3 m / s or more. Furthermore, the wind speed is preferably 13 m / s or less, more preferably 12 m / s or less, and even more preferably 10 m / s or less, because this prevents breakage, tearing, pin removal, etc., due to flapping of the pre-heat-treatment film.

[0024] The speed of the hot air blown onto the fixing device installation surface of the pre-heat-treatment film is preferably 0.4 m / s or more and 14 m / s or less. This facilitates removal of the solvent contained in the pre-heat-treatment film, and, if the pre-heat-treatment film is a polyimide precursor (polyamic acid), facilitates imidization (thermal imidization). Therefore, the speed is more preferably 0.9 m / s or more, even more preferably 1.4 m / s or more, and even more preferably 1.9 m / s or more. Furthermore, the speed is preferably 12 m / s or less, more preferably 11 m / s or less, and even more preferably 9 m / s or less, in order to prevent breakage, tearing, pin removal, etc., due to flapping of the pre-heat-treatment film.

[0025] The velocity of the hot air blown onto the non-fixing device-installed surface of the pre-heat treatment film must be equal to or greater than the velocity of the hot air blown onto the fixing device-installed surface. The ratio of the velocity of the non-fixing device-installed surface to the fixing device-installed surface (fixing device-installed surface / fixing device-installed surface) is preferably greater than 1.0. This ratio is preferably 1.05 or greater, more preferably 1.1 or greater, because it reduces the proportion of hot air blocked by the fixing device (pin sheet 11), ensures that the hot air reaches both ends of the pre-heat treatment film sufficiently, and facilitates drying of both ends of the pre-heat treatment film and completion of the chemical reaction. Furthermore, this ratio is preferably 10 or less, more preferably 5 or less, and even more preferably 3 or less, because it suppresses the temperature drop in the space on the fixing device-installed surface side and the temperature drop of the film itself due to the temperature drop, and facilitates drying of the entire pre-heat treatment film and completion of the chemical reaction.

[0026] If the velocity of the hot air blown onto the non-fixing surface of the pre-heat-treatment film is lower than the velocity of the hot air blown onto the fixing surface, the proportion of hot air blocked by the film fixing device increases, resulting in a decrease in the amount of hot air hitting the pre-heat-treatment film edges. As a result, the pre-heat-treatment film edges require more time to dry and complete the chemical reaction than the pre-heat-treatment film center. When only the film edges are incompletely dried or undergoes chemical reactions, the film edges lack sufficient strength, potentially causing appearance defects such as tears and stretching originating from the film fixing structure (pin 11a). If this abnormality becomes significant, the broken film may become stuck at the oven exit or other locations, making film transport itself difficult. Furthermore, such appearance defects originating from the film edges may extend beyond the edges and extend to the film center, resulting in quality degradation and production losses.

[0027] The residual solvent content of the heat-treated and dried film is preferably 500 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less. The lower the residual solvent content, the better, but from an industrial standpoint, it may be 1 ppm or more, or even 10 ppm or more.

[0028] The film of the present invention is preferably produced by a method in which the film is wound up as a long film having a width of 300 mm or more and a length of 10 m or more. The method for fixing both ends in the width direction of one side of the film before heat treatment is not particularly limited, and the film may be held by being pierced by pins of a pin tenter-type conveying device or by being clamped by clips of a clip tenter-type conveying device.

[0029] The width of both ends (the width of each end) is not particularly limited as long as it is a width that can be fixed by a conventionally known tenter-type conveying device. Specifically, the lower limit is preferably 5 mm or more, more preferably 10 mm or more. Alternatively, the sum of the widths of both ends is preferably 0.1% or more of the total width of the film before heat treatment, more preferably 0.5% or more, and even more preferably 1% or more. Furthermore, the upper limit of the width of both ends (the width of each end) is preferably 100 mm or less, more preferably 50 mm or less. Alternatively, the sum of the widths of both ends is preferably 50% or less of the total width of the film, more preferably 30% or less, and even more preferably 10% or less.

[0030] The central part in the width direction of the film before heat treatment is preferably located at a position that is 30 to 70% from one end, more preferably 40 to 60%, and even more preferably 45 to 55%, when the total width of the film before heat treatment is 100%.

[0031] The transport speed of the film before heat treatment can be appropriately set depending on the heat treatment conditions (such as the temperature and speed of the hot air). The appropriate transport speed is difficult to determine precisely because it depends on the length of the heat treatment furnace, but a slow speed may result in a decrease in productivity. The transport speed is preferably 0.05 m / min or more, more preferably 0.1 m / min or more.

[0032] <Film> Examples of the film (heat-treated film) of the present invention include films of polyimide resins such as polyimide, polyamideimide, polyetherimide, and fluorinated polyimide (e.g., aromatic polyimide resins, alicyclic polyimide resins); polyolefin resins such as polyethylene and polypropylene; copolymer polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate (e.g., wholly aromatic polyesters, semi-aromatic polyesters); copolymer (meth)acrylates typified by polymethyl methacrylate; polycarbonate; polyamide; polysulfone; polyethersulfone; polyether ketone; cellulose acetate; cellulose nitrate; aromatic polyamide; polyvinyl chloride; polyphenol; polyarylate; polyphenylene sulfide; polyphenylene oxide; and polystyrene.

[0033] Since the film is intended to be suitable for use in processes involving heat treatment at 250°C or higher, only a limited number of the polymer films listed are actually applicable. Among the films, films using so-called super engineering plastics are preferred, and more specifically, polyimide resins, polyamide resins, polyamideimide resins, and azole resins are mentioned. Particularly preferred examples include aromatic polyimide films, aromatic amide films, aromatic amideimide films, aromatic benzoxazole films, aromatic benzothiazole films, and aromatic benzimidazole films.

[0034] Examples of the pre-heat treatment film of the present invention include a film containing an organic solvent (pre-dried film), a film before a chemical reaction (precursor film), or a precursor film containing an organic solvent (pre-dried precursor film). The organic solvent content of the pre-heat treatment film is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less, so that the pre-heat treatment film can be transported while being fixed (held) at both ends. Furthermore, from the viewpoints of production efficiency and cost, the organic solvent content is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more.

[0035] A polyimide-based resin film (sometimes referred to as a polyimide film), which is an example of such a film, will be described in detail below. Generally, a polyimide-based resin film is obtained by applying a polyamic acid (polyimide precursor) solution obtained by reacting diamines and tetracarboxylic acids in a solvent to a support for polyimide film production, drying the solution, and forming a green film (hereinafter also referred to as a "polyamic acid film"), which is then subjected to high-temperature heat treatment on the support for polyimide film production or after being peeled off the support to cause a dehydration ring-closing reaction. This polyamic acid film is a polyimide precursor film.

[0036] The polyamic acid (a polyimide precursor, hereinafter also referred to as polyamic acid) solution can be applied by any of conventionally known solution application methods, such as spin coating, doctor blade, applicator, comma coater, screen printing, slit coating, reverse coating, dip coating, curtain coating, and slit die coating.

[0037] The diamines constituting the polyamic acid are not particularly limited, and aromatic diamines, aliphatic diamines, alicyclic diamines, etc., which are commonly used in polyimide synthesis, can be used. From the viewpoint of heat resistance, aromatic diamines are preferred. The diamines can be used alone or in combination of two or more.

[0038] The diamines are not particularly limited, and examples thereof include oxydianiline (bis(4-aminophenyl)ether), paraphenylenediamine (1,4-phenylenediamine), and the like.

[0039] As the tetracarboxylic acids constituting the polyamic acid, aromatic tetracarboxylic acids (including their acid anhydrides), aliphatic tetracarboxylic acids (including their acid anhydrides), and alicyclic tetracarboxylic acids (including their acid anhydrides) commonly used in polyimide synthesis can be used. When these are acid anhydrides, the anhydride structure may be one or two in the molecule, but preferably two anhydride structures (dianhydrides) are preferred. The tetracarboxylic acids may be used alone or in combination of two or more.

[0040] The tetracarboxylic acid is not particularly limited, and examples thereof include pyrrolimetic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0041] The polyimide film may be a transparent polyimide film.

[0042] A colorless and transparent polyimide, which is an example of the film, will be described below. Hereinafter, to avoid complication, it will also be referred to simply as transparent polyimide. The transparency of the transparent polyimide is preferably such that the total light transmittance is 75% or more. More preferably, it is 80% or more, even more preferably 83% or more, even more preferably 84% or more, and particularly preferably 85% or more. There is no particular upper limit for the total light transmittance of the transparent polyimide, but for use as a flexible electronic device, it is preferably 98% or less, more preferably 97% or less. The colorless and transparent polyimide of the present invention is preferably a polyimide with a total light transmittance of 75% or more.

[0043] Examples of aromatic tetracarboxylic acids for obtaining colorless and highly transparent polyimides include 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid, 4,4'-oxydiphthalic acid, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylic acid)1,4-phenylene, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-yl)benzene-1,4-dicarboxylate, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(benzene-1,4-diyloxy)] ]dibenzene-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(4 -isopropyl-toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(benzene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3H-2,1-benzo 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(4-isopropyl-toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4,4'-diphenylsulfonetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, pyromellitic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]diphthalic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]diphthalic acid, and tetracarboxylic acids such as these acid anhydrides. Among these, dianhydrides having two acid anhydride structures are preferred, and 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride and 4,4'-oxydiphthalic dianhydride are particularly preferred. The aromatic tetracarboxylic acids may be used alone or in combination of two or more. When heat resistance is important, the copolymerization amount of the aromatic tetracarboxylic acids is, for example, preferably 50% by mass or more of the total tetracarboxylic acids, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more, and may even be 100% by mass.

[0044] Examples of alicyclic tetracarboxylic acids include 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 1,2,3,4-cyclohexanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 3,3',4,4'-bicyclohexyltetracarboxylic acid, bicyclo[2,2,1]heptane-2,3,5,6-tetracarboxylic acid, bicyclo[2,2,2]octane-2,3,5,6-tetracarboxylic acid, and bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic acid. carboxylic acid, tetrahydroanthracene-2,3,6,7-tetracarboxylic acid, tetradecahydro-1,4:5,8:9,10-trimethanoanthracene-2,3,6,7-tetracarboxylic acid, decahydronaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4:5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4-ethano-5,8-methanonaphthalene-2,3,6,7-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane -5,5'',6,6''-tetracarboxylic acid (also known as "norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid"), methylnorbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid (also known as "norbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid pyro-2'-cyclohexanone-6'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid), methylnorbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclopropanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclobutanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cycloheptanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclooctanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclononanone-α'-spiro-2''-norbornane-5,5'',6 ,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclodecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cycloundecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclododecanone-α'-spiro-2''-norbornane-5,5'', ,6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclotridecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclotetradecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentadecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-(methylcyclopentanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, and norbornane-2-spiro-α-(methylcyclohexanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, and tetracarboxylic acids such as these acid anhydrides. Among these, dianhydrides having two acid anhydride structures are preferred, and in particular, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, and 1,2,4,5-cyclohexanetetracarboxylic dianhydride are preferred, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,4,5-cyclohexanetetracarboxylic dianhydride are more preferred, and 1,2,3,4-Cyclobutanetetracarboxylic dianhydride is more preferred. These may be used alone or in combination of two or more. When transparency is important, the copolymerization amount of the alicyclic tetracarboxylic acids is, for example, preferably 50% by mass or more of the total tetracarboxylic acids, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more, and may even be 100% by mass.

[0045] Examples of tricarboxylic acids include aromatic tricarboxylic acids such as trimellitic acid, 1,2,5-naphthalenetricarboxylic acid, diphenylether-3,3',4'-tricarboxylic acid, and diphenylsulfone-3,3',4'-tricarboxylic acid, as well as hydrogenated products of the above aromatic tricarboxylic acids such as hexahydrotrimellitic acid, alkylene glycol bistrimellitates such as ethylene glycol bistrimellitate, propylene glycol bistrimellitate, 1,4-butanediol bistrimellitate, and polyethylene glycol bistrimellitate, and monoanhydrides and esterified products thereof. Among these, monoanhydrides having one acid anhydride structure are preferred, with trimellitic anhydride and hexahydrotrimellitic anhydride being particularly preferred. These may be used alone or in combination.

[0046] Examples of dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid, as well as hydrogenated versions of these aromatic dicarboxylic acids such as 1,6-cyclohexanedicarboxylic acid, oxalic acid, succinic acid, glutaric acid, adipic acid, heptanedioic acid, octanedioic acid, azelaic acid, sebacic acid, undecadioic acid, dodecanedioic acid, and 2-methylsuccinic acid, as well as acid chlorides and esters thereof. Among these, aromatic dicarboxylic acids and hydrogenated versions thereof are preferred, with terephthalic acid, 1,6-cyclohexanedicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid being particularly preferred. The dicarboxylic acids may be used alone or in combination.

[0047] The diamines or isocyanates used to obtain colorless and highly transparent polyimides are not particularly limited, and aromatic diamines, aliphatic diamines, alicyclic diamines, aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and the like, which are commonly used in polyimide synthesis, polyamideimide synthesis, and polyamide synthesis, can be used. From the viewpoint of heat resistance, aromatic diamines are preferred, and from the viewpoint of transparency, alicyclic diamines are preferred. Furthermore, the use of aromatic diamines having a benzoxazole structure makes it possible to achieve high heat resistance, as well as a high elastic modulus, low heat shrinkage, and a low coefficient of linear expansion. Diamines and isocyanates can be used alone or in combination of two or more.

[0048] Examples of aromatic diamines include 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, and bis[4-(3-aminophenoxy)phenyl]. sulfide, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 4-amino-N-(4-aminophenyl)benzamide, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4, 4'-diaminodiphenyl ether, 2,2'-trifluoromethyl-4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzo phenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 1,1-bis[4-(4-aminophenoxy)phenyl]propane, 1,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,1-bis[4-(4-aminophenoxy)phenyl]butane, 1,3-bis[4-(4-aminophenoxy)phenyl]butane, 1,4-bis[4-(4-aminophenoxy)phenyl]butane, 2,2-bis[4-(4-aminophenoxy)phenyl]butane, 2,3-bis[4-(4-aminophenoxy)phenyl]butane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)phenyl] )-3-methylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3-methylphenyl]propane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis [4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 4,4'-bis[(3-aminophenoxy)benzoyl]benzene, 1,1-bis[4-(3-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl sulfide, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, bis[4-(3-aminophenoxy)phenyl]sulfoxide, 4,4'-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenone Nilsulfone, bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-fluorophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino -6-methylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-cyanophenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-4,4'-diphenoxybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino 3,4'-diamino-5'-phenoxybenzophenone, 3,3'-diamino-4,4'-divinylphenoxybenzophenone, 4,4'-diamino-5,5'-divinylphenoxybenzophenone, 3,4'-diamino-4,5'-divinylphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 3,4'-diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis(3-amino-4-phenoxybenzoyl)benzene, 1,4-bis(3-amino-4-phenoxybenzoyl)benzene, 1,3-bis(4-amino-5-phenoxybenzoyl)benzene, 1,4-bis(4-amino-5-phenoxybenzoyl)benzene, 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,3-bis(4-amino-5-biphenoxybenzoyl)benzene, 1,4-bis(4-amino-5-biphenoxybenzoyl)benzene, 2,6-bis[4-(4-amino-α,α-dimethyl Examples of the aromatic diamine include 4,4'-[9H-fluorene-9,9-diyl]bisaniline (also known as "9,9-bis(4-aminophenyl)fluorene"), spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]bisaniline, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]bisaniline, and 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]bisaniline. Some or all of the hydrogen atoms on the aromatic ring of the aromatic diamine may be substituted with a halogen atom, an alkyl or alkoxy group having 1 to 3 carbon atoms, or a cyano group, and further some or all of the hydrogen atoms of the alkyl or alkoxy group having 1 to 3 carbon atoms may be substituted with a halogen atom. The aromatic diamines having a benzoxazole structure are not particularly limited, and examples thereof include 5-amino-2-(p-aminophenyl)benzoxazole, 6-amino-2-(p-aminophenyl)benzoxazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzoxazole, 2,2'-p-phenylenebis(5-aminobenzoxazole), 2,2'-p-phenylenebis(6-aminobenzoxazole), 1-(5-aminobenzoxazolo)-4-(6-aminobenzoxazolo)benzene, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,Examples of aromatic diamines include 4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, and 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole. Among these, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 4-amino-N-(4-aminophenyl)benzamide, 4,4'-diaminodiphenyl sulfone, and 3,3'-diaminobenzophenone are particularly preferred. The aromatic diamines may be used alone or in combination.

[0049] Examples of alicyclic diamines include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, and 4,4'-methylenebis(2,6-dimethylcyclohexylamine). Among these, 1,4-diaminocyclohexane and 1,4-diamino-2-methylcyclohexane are particularly preferred, and 1,4-diaminocyclohexane is more preferred. The alicyclic diamines may be used alone or in combination.

[0050] Examples of diisocyanates include diphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-diethyl Diphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethoxydiphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, diphenylether-4,4' -diisocyanate, benzophenone-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-(2,2-bis(4-phenoxyphenyl)propane)diisocyanate, 3,3'- or 2,2'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'- or 2,2'-di Examples of the diisocyanate include aromatic diisocyanates such as ethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, and 3,3'-diethoxybiphenyl-4,4'-diisocyanate, and diisocyanates obtained by hydrogenating any of these (for example, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate).Among these, diphenylmethane-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and 1,4-cyclohexane diisocyanate are preferred from the viewpoints of low moisture absorption, dimensional stability, cost, and polymerizability. The diisocyanates may be used alone or in combination.

[0051] The solvent may be any solvent capable of dissolving polyimide or a polyimide precursor, and aprotic polar solvents can be suitably used. Examples of the solvent include N,N-di-lower alkylcarboxylamides such as N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, and N,N-dimethylmethoxyacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, dimethyl sulfoxide, dimethyl sulfone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, diglyme, m-cresol, hexamethylphosphoramide, N-acetyl-2-pyrrolidone, hexamethylphosphoramide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, and p-chlorophenol. The solvent may be a mixture of two or more solvents.

[0052] The thickness of the film is preferably 3 μm or more, more preferably 7 μm or more, even more preferably 14 μm or more, and even more preferably 20 μm or more. There is no particular upper limit to the thickness of the film, but for use as a flexible electronic device, it is preferably 250 μm or less, more preferably 100 μm or less, and even more preferably 50 μm or less.

[0053] When the film is a transparent polyimide film, its yellowness index (hereinafter also referred to as "yellow index" or "YI") is preferably 10 or less, more preferably 7 or less, even more preferably 5 or less, and still more preferably 3 or less. There is no particular lower limit for the yellowness index of the transparent polyimide, but for use as a flexible electronic device, it is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more.

[0054] The film is preferably obtained in the form of a long film wound up during production, having a width of 300 mm or more and a length of 10 m or more, and more preferably in the form of a roll film wound up on a winding core. When the film is wound up in a roll, it can be easily transported in the form of a roll film.

[0055] To ensure ease of handling and productivity, the film preferably contains approximately 0.03 to 3% by mass of lubricant (particles) with a particle size of approximately 10 to 1,000 nm, imparting fine irregularities to the film surface and ensuring slipperiness. The particle size of the lubricant is preferably 20 to 500 nm, more preferably 30 to 300 nm, and even more preferably 50 to 200 nm. By setting the lubricant particle size to 10 nm or more, sufficient slipperiness can be achieved relative to the amount added. Furthermore, by setting the lubricant particle size to 1,000 nm or less, problems such as a decrease in mechanical strength and cloudiness of the film can be reduced.

[0056] The film manufacturing apparatus of the present invention has a fixing mechanism A that installs fixing devices at both widthwise ends of one side of the pre-heat-treatment film and fixes the heat-treated film with the fixing devices, an air blowing mechanism B that blows hot air to both sides of the pre-heat-treatment film, and a transport mechanism C that transports the pre-heat-treatment film, wherein the air blowing mechanism B blows hot air at a speed equal to or faster than the speed of hot air blown to a side where no fixing devices are installed. The film and mechanisms A to C in the manufacturing apparatus are the same as those described in the film manufacturing method.

[0057] The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0058] Synthesis Example 1 (Preparation of Polyamic Acid Solution A) After the atmosphere in a reaction vessel equipped with a nitrogen inlet tube, a reflux condenser, and a stirrer was replaced with nitrogen, 33.36 parts by mass of 4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (TFMB), 270.37 parts by mass of N,N-dimethylacetamide (DMAC), and a dispersion obtained by dispersing colloidal silica in dimethylacetamide (Snowtex (registered trademark) DMAC-ST, manufactured by Nissan Chemical Industries, Ltd.) were added and completely dissolved in an amount of 0.15% by mass of silica based on the total polymer solid content in the polyamic acid solution. Subsequently, 9.81 parts by mass of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 11.34 parts by mass of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), and 4.85 parts by mass of 4,4′-oxydiphthalic acid dihydrate (ODPA) were added in portions as solids, and the mixture was stirred at room temperature for 24 hours. Thereafter, 165.7 parts by mass of DMAc was added for dilution to obtain a polyamic acid solution A (PAA-A) (molar ratio of TFMB / / CBDA / BPDA / ODPA=1.00 / / 0.48 / 0.37 / 0.15) having a solids content of 18% by mass and a reduced viscosity of 2.7 dl / g.

[0059] Synthesis Example 2 (Preparation of Polyamic Acid Solution B) While passing nitrogen into a reactor equipped with a nitrogen inlet tube and a stirring blade, 3.16 parts by mass of pyromellitic dianhydride (PMDA), 2.84 parts by mass of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), and 7.73 parts by mass of 4,4′-diamino-2,2′-bis(trifluoromethyl)biphenyl (TFMB) were placed, and N,N-dimethylacetamide (DMAc, 77.8 parts by mass) and a dispersion obtained by dispersing colloidal silica (lubricant) in dimethylacetamide ("Snowtex (registered trademark) DMAC-ST-ZL" manufactured by Nissan Chemical Industries, Ltd.) were added so that the colloidal silica (lubricant) accounted for 0.15% by mass relative to the total polymer solids content in the polyamic acid solution. The mixture was then stirred at 25° C. for 24 hours to obtain polyamic acid solution B (PAA-B) (TFMB / / PMDA / BPDA).

[0060] Example 1: The resulting polyamic acid solution A was applied to the non-slip surface of a polyethylene terephthalate film A4100 (manufactured by Toyobo Co., Ltd.) using a comma coater to a final film thickness of 20 μm. This was then dried at 90°C for 15 minutes. The self-supporting polyamic acid film obtained after drying was peeled off from the A4100 film that had been used as the support, yielding a polyamic acid film (pre-heat-treated film). Next, pin tenters 11 (film fixtures) were installed on the edge of the lower surface of the pre-heat-treated film with pins 11a (film fixing structures) facing upward, and the pre-heat-treated film edge was inserted into the pins to secure it in place. The pre-heat-treated film was then transported while adjusting the pin sheet spacing to prevent breakage. Hot air was blown from the upper air outlet onto the non-fixed surface and from the lower air outlet onto the fixed surface at 250°C for 3 minutes, 290°C for 3 minutes, 340°C for 3 minutes, and 350°C for 3 minutes, respectively, to allow the imidization reaction to proceed. In each temperature zone, hot air outlets were installed 175 mm above and below the position where the pre-heat-treatment film passed, and hot air at a speed of 3.8 m / s was supplied from the upper outlet (toward the surface of the film where the fixtures were not installed) and hot air at a speed of 3.6 m / s was supplied from the lower outlet (toward the surface of the film where the fixtures were installed). The film was then cooled to room temperature over 2 minutes, and the poorly flat portions on both ends of the film were cut off with a slitter. The film was then wound up into a roll, yielding 100 m of polyimide film with a width of 500 mm.

[0061] Examples 2 to 4 The resins and production conditions used were as shown in Table 1, and the same procedure as in Example 1 was carried out to obtain polyimide films.

[0062] Comparative Examples 1 and 2 Polyimide films were obtained in the same manner as in Example 1, using the resins and production conditions shown in Table 1.

[0063] <Measurement of Air Speed ​​at Air Outlet> A heat treatment furnace at room temperature was set to blow air at room temperature, and an anemometer (Kanomax: ANEMOMASTER: MODEL 6003) was used to measure the air speed at the hot air outlet.

[0064] <Film appearance (edges)> The state of the film before heat treatment while being transported through the furnace, and the state of the film edge (fixed part) after heat treatment were visually inspected and evaluated. Evaluation was made on the following three levels. ◯: No problem with film transport, and the film can be kept properly stretched. △: No problem with film transport, but the film cannot be kept properly stretched. ×: The film separated or sagged due to breakage or tearing, making it difficult to transport due to contact with the furnace wall.

[0065] <Film appearance (center)> After the fixing portion was cut, the remaining portion was visually inspected for any abnormalities such as breaks, tears, or wrinkles. The evaluation was conducted on the following two levels: ◯: No abnormalities such as breaks, tears, or wrinkles were observed anywhere except the film end (fixing portion). ×: Abnormalities such as breaks, tears, or wrinkles were observed anywhere except the film end (fixing portion).

[0066] <Total Light Transmittance> The total light transmittance (TT) of the film was measured using a HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). A D65 lamp was used as the light source. Five 50 mm square pieces of film were unwound from a roll of film by 2 m and measured once for each piece. The arithmetic mean value of the five measured values ​​was used.

[0067] <Film Thickness> The film thickness was measured using a film thickness measuring instrument HKT-1216 (manufactured by Mahl Co., Ltd.) 2.5 m of the film was unwound from a roll, and the entire width was measured at 2 cm intervals from any one end of the film to the inside, and the average of the measurements was taken as the film thickness.

[0068] <YI> Using a color meter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) and a C2 light source, the tristimulus values ​​X, Y, and Z of the film were measured in accordance with ASTM D1925, and the yellowness index (YI) was calculated using the following formula: 3 m of the film was unwound from a roll, five 50 mm square pieces of film were cut out, and one measurement was performed on each piece of film, resulting in a total of five measurements, for which the arithmetic mean value was used: YI = 100 × (1.28X - 1.06Z) / Y

[0069] <Tg (glass transition temperature)> The glass transition temperature was measured by cutting a piece of film measuring 5 mm x 20 mm from the widthwise center of a rolled film unwound for 3.5 m, and measuring the temperature at which the change in modulus of elasticity (mechanical tan δ) was maximized using a dynamic viscoelasticity measuring device (DMA Q800 manufactured by TA Instruments) from 30°C to 450°C at a heating rate of 5°C / min and a frequency of 10 Hz. The glass transition temperature was determined as the temperature at which the change in modulus of elasticity (mechanical tan δ) was maximized. Detailed measurement conditions are as follows: Measurement mode: DMA Multi-Frequency-strain Tension film / Rectangular strain: 0.1% Preload force: 0.02 N Force track: 125% Poisson's ratio: 0.440

[0070] <CTE (Coefficient of Linear Thermal Expansion)> One 20 mm x 2 mm piece of film with its long side in the machine direction (MD) during coating and another 20 mm x 2 mm piece of film with its long side in the width direction (TD) were cut out from the center of the width direction 4 m from a rolled-up film. The expansion / contraction rate of each piece was measured under the following conditions. The expansion / contraction rate / temperature was measured at 15°C intervals, such as from 30°C to 45°C and from 45°C to 60°C. This measurement was repeated up to 300°C, and the average of all measurements was calculated as CTE. Furthermore, the average of the calculation results for the film with its long side in the MD and the film with its long side in the TD was calculated. Instrument name: TMA4000S, manufactured by MAC Sciences; Sample length: 20 mm; Sample width: 2 mm; Heat-up start temperature: 25°C; Heat-up end temperature: 300°C; Heat-up rate: 5°C / min; Atmosphere: Argon

[0071] The films obtained in the above Examples and Comparative Examples were evaluated for film appearance (center and edge), YI, Tg, and CTE, and the results are shown in Table 1 below.

[0072]

[0073] The present invention can provide a film that is free from breakage, tearing, and appearance abnormalities not only in the center of the film but also in both fixed end portions and their vicinity during film production, and can be preferably applied to, for example, flexible electronic devices.

[0074] REFERENCE SIGNS LIST 1 Film (film before heat treatment) 1a Film center 1b Film edge 11 Pin sheet (film fixing device) 11a Pin (film fixing structure) 21 Hot air outlet on the side where the film fixing device is not installed 22 Hot air outlet on the side where the film fixing device is installed 31 Hot air blown onto the side where the film fixing device is not installed 32 Hot air blown onto the side where the film fixing device is installed

Claims

1. A method for manufacturing a film, Step A: Fixing devices are installed at both ends in the width direction of one side of the film before heat treatment, and the heat-treated film is fixed with the fixing devices. Step B involves blowing hot air onto both sides of the pre-heat-treated film. Step C of transporting the film before heat treatment. It has, In step B, the wind speed of the hot air blown onto the surface where the fixing device is not installed is the same as or greater than the wind speed of the hot air blown onto the surface where the fixing device is installed. The method for manufacturing a film, wherein step B is characterized in that the wind speed on the side where the fixing device is not installed is more than 1.0 times the wind speed on the side where the fixing device is installed.

2. The method for manufacturing a film according to claim 1, wherein the fixing device is a pin sheet.

3. The method for manufacturing a film according to claim 1, wherein the film is a polyimide film.

4. The method for manufacturing a film according to claim 3, wherein the polyimide film is a transparent polyimide film.

5. A film manufacturing apparatus, Fixing mechanism A: Fixing devices are installed at both ends in the width direction of one side of the film before heat treatment, and the heat-treated film is fixed with the fixing devices. Air blowing mechanism B blows hot air onto both sides of the film before heat treatment. Conveying mechanism C for transporting the pre-heat-treated film. It has, The blowing mechanism B is characterized in that the wind velocity of the hot air blown onto the surface where no fasteners are installed is the same as or greater than the wind velocity of the hot air blown onto the surface where fasteners are installed, and the wind velocity on the surface where no fasteners are installed is more than 1.0 times the wind velocity on the surface where fasteners are installed.