Biaxially oriented polyester film roll and manufacturing method thereof

Abstract

To provide a biaxially oriented polyester film roll and a manufacturing method thereof, capable of uniformly providing a thin resin layer on a film by reducing unevenness in the outer diameter of the film roll while the wound film is thin and highly smooth.SOLUTION: The present invention provides a film roll with a film wound around a cylindrical core, wherein a parameter A (A: the maximal value of a vertical distance between convex and concave portions adjacent to each other within a distance of half the film roll width in an outer diameter change curve of the film roll) is 320 μm or under, the parameter A being obtained from an outer diameter change curve obtained by measuring a width direction outer diameter change of the film roll at a winding lapsed day of 30 days, by setting the width direction as the lateral axis and the outer diameter as the longitudinal axis; a winding length of the film is 5,000 m or over; a film thickness is 1 μm or over and 30 μm or under; and a surface roughness SRa of at least one side of the film is 0.1 nm or over and 10 nm or under.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a biaxially oriented polyester film roll obtained by winding up a biaxially oriented polyester film, and a method for producing the same. [Background technology]

[0002] Biaxially oriented polyester film is used as a transfer material for ceramic slurries in ceramic capacitor manufacturing and photoresists for forming printed wiring board circuits due to its moderate toughness, thermal stability, smoothness, transparency, and economical efficiency. It is usually wound up in a roll shape around a hollow core made of plastic or paper to prevent wrinkles and foreign matter from being caught in it. It is unwound, coated with the transfer material, and wound up again to become the transfer material. When used, the transfer material is transferred to the target object by heat, pressure, etc.

[0003] For example, dry film photoresist is used for forming printed wiring board circuits, in which a photosensitive resin layer (photoresist layer) is laminated on a polyester film as a support, and then sandwiched between protective films (cover films) made of low-density polyethylene film, polypropylene film, polyester film, etc. In recent years, this technology has been used to apply protective film transfer materials with protective films that have anti-rust properties and high refractive index even though they are thin. In addition to the transfer of copper and ITO (indium tin oxide), the protective film is added to give the metal wiring of the frame of the touch panel concealment properties, and to prevent oxidation and glare of the ITO film. The copper and ITO layers are removed by exposure and etching except for the masked parts, but the protective film remains as the touch panel material. The transfer target is an ultra-thin resin layer of nano-order, and the transfer surface must be smooth in order to apply and transfer uniformly.

[0004] On the other hand, when a highly smooth film is wound into a roll, wrinkles are likely to occur due to unevenness in the outer diameter in the width direction of the film roll, and the air trapped between the film layers during the winding process is difficult to escape, so that unevenness in the outer diameter of the film roll cannot be detected immediately after winding without being affected by unevenness in the film thickness, and unevenness in the outer diameter occurs due to the escape of the trapped air during storage as a film roll, which causes wrinkles when used by the user, and the problem of being unable to provide a uniform resin layer on the film as the transfer target. Furthermore, this problem becomes even more pronounced when the film roll is made wider and longer in order to improve productivity.

[0005] Furthermore, when a resin layer to be transferred is applied to a film unwound from a film roll in which unevenness in the outer diameter has occurred due to the accumulation of unevenness in the film thickness and the film is then rewound, the problem of the uniformity of the applied resin layer being lost due to the influence of the accumulation of unevenness in the film thickness occurs. Moreover, this problem becomes even more pronounced when the film roll is made wider and longer in order to improve productivity.

[0006] To address the above-mentioned problems, Patent Documents 1 and 2 disclose techniques for regulating the outer diameter unevenness in the width direction of a film roll. Patent Documents 3 and 4 disclose techniques for regulating the outer diameter unevenness in the width direction of a film roll that has changed over time. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication WO01 / 048061 [Patent Document 2] JP 2001-76337 A [Patent Document 3] JP 2003-266525 A [Patent Document 4] JP 2023-92628 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the techniques described in Patent Documents 1 and 2 do not take into consideration the change in outer diameter unevenness that occurs when the air wound in the film roll escapes during storage. Even when the techniques described in Patent Documents 3 and 4 are used, it is not possible to sufficiently suppress the poor uniformity of the resin layer applied in an ultra-thin film. The present invention aims to solve the above problems and provide a biaxially oriented polyester film roll in which the wound film is thin and highly smooth, but does not cause poor uniformity of the resin layer due to the influence of wrinkles caused by uneven outer diameter of the film roll or lamination of uneven thickness, and a method for producing the same. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention comprises the following configuration. (1) A film roll having a film wound around a cylindrical core, the film roll being characterized in that, after 30 days have passed since winding, a parameter A (A: the maximum value of the difference (vertical distance) between the maximum outer diameter at a convex portion and the minimum outer diameter at a concave portion between adjacent convex portions and concave portions at an interval of up to half the film roll width in the outer diameter change curve of the film roll) obtained by measuring the change in the outer diameter in the width direction of the film roll on the horizontal axis and the outer diameter on the vertical axis is 320 μm or less, the winding length of the film is 5,000 m or more, the thickness of the film is 1 μm or more and 30 μm or less, and the surface roughness SRa of at least one side of the film is 0.1 nm or more and 10 nm or less. (2) A method for producing a film roll, comprising a film roll evaluation step of evaluating a parameter A obtained from an outer diameter change curve obtained by measuring the change in outer diameter in the width direction immediately after winding of an evaluation film roll wound with a surface hardness of 98° or more. (3) A method for producing a film roll, comprising a film roll evaluation step of evaluating a parameter B (B: difference (vertical distance) between the maximum outer diameter at a convex portion and the minimum outer diameter at a concave portion between adjacent convex and concave portions in the outer diameter change prediction curve of the film roll, obtained from data on thickness change in the width direction of the stretched film measured in the film formation step). Effect of the Invention

[0010] According to the present invention, it is possible to provide a biaxially oriented polyester film roll and a manufacturing method thereof, in which the wound film is thin and highly smooth, while the outer diameter unevenness of the film roll is reduced, thereby enabling a thin film resin layer to be uniformly provided on the film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The film roll of the present invention is a film roll having a film wound around a cylindrical core, and is characterized in that, 30 days after winding, a parameter A (A: the maximum vertical distance between adjacent convex and concave portions spaced apart by up to half the film roll width in the outer diameter change curve of the film roll, obtained by measuring the change in outer diameter in the width direction of the film roll and plotting the width direction on the horizontal axis and the outer diameter on the vertical axis) is 320 μm or less, the length of the film is 5,000 m or more, the thickness of the film is 1 μm or more and 30 μm or less, and the surface roughness SRa of at least one side of the film is 0.1 nm or more and 10 nm or less. The film roll of the present invention will be specifically described below.

[0012] In the present invention, the film roll refers to a film wound around a cylindrical core of any material, and the film refers to a molded product obtained by molding a thermoplastic resin or a composition mainly composed of a thermoplastic resin into a sheet shape. The resin constituting the film is not particularly limited as long as it does not impair the effects of the present invention, and examples thereof include polyester resins such as polyethylene terephthalate (PET), polyethylene isophthalate (PEI), and polybutylene terephthalate (PBT), polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon 6, nylon 66, nylon 12, aromatic nylon, and aramid, polyimide resins, polysulfone resins, polyvinyl resins, polyester ether resins, polycarbonate resins, polyphenylene sulfide resins, polylactic acid resins, cellulose resins, and acrylic resins, etc., which can be used alone or in combination. Among them, it is preferable to use polyethylene terephthalate, polypropylene, aramid, and polyimide resins. In addition, the various resins may contain copolymer components in the molecular chain, and may contain additives such as antistatic agents, weather resistance agents, inorganic or organic particles, lubricants such as wax, pigments, etc., within the scope of not impairing the effects of the present invention. In addition, the film may have a single layer structure or a laminated structure of two or more layers.

[0013] In the film roll of the present invention, from the viewpoint of reducing the poor uniformity of the applied resin layer affected by the lamination of wrinkles and thickness unevenness due to the unevenness of the outer diameter of the film roll, it is important that the parameter A (A: the maximum value of the vertical distance between adjacent convex and concave portions spaced apart within half the width of the film roll in the curve of the outer diameter change of the film roll) obtained by measuring the change in the outer diameter in the width direction of the film roll 30 days after winding, with the horizontal axis representing the width direction and the vertical axis representing the outer diameter, is 320 μm or less, and more preferably 280 μm or less. The width direction refers to the direction parallel to the central axis of the cylindrical core of the film roll. The change in the outer diameter in the width direction of the film roll is measured with an external shape measuring device using a displacement sensor or the like slidably installed on the film roll in parallel to the width direction, and the change in the external shape is graphed as the change in the outer diameter of the film roll, to obtain the curve of the change in the outer diameter. When measuring the change in the outer diameter of a film roll that has been wound up for 29 days or less, the parameter A obtained from the outer diameter change curve is smaller than when measuring the change in the outer diameter of a film roll that has been wound up for 30 days, because air trapped between the film layers during the winding process remains. However, as time passes, the air trapped between the film layers is discharged, so the parameter A increases, and there is a problem of wrinkles due to the unevenness of the outer diameter of the film roll and poor uniformity of the coated resin layer due to the influence of the lamination of uneven thickness. In addition, if the parameter A obtained from the outer diameter change curve of a film roll that has been wound up for 30 days is large, wrinkles due to the unevenness of the outer diameter of the film roll and poor uniformity of the coated resin layer due to the influence of the lamination of uneven thickness are likely to occur, so the occurrence of wrinkles can be reduced by setting the parameter A obtained from the outer diameter change curve of a film roll that has been wound up for 30 days to 320 μm or less. From the above viewpoint, the parameter A is more preferably 280 μm or less.

[0014] The method for making the parameter A obtained from the outer diameter change curve obtained by measuring the outer diameter change in the width direction of the film roll 30 days after winding the film roll to 320 μm or less is not particularly limited as long as it does not impair the effects of the present invention, and examples of the method include a method of adjusting the slit width of the die for extruding the molten resin. Also, a method of winding the film while dispersing thickness unevenness by performing an oscillation operation in which the transport film is oscillated in the width direction and wound can be used.

[0015] In the film roll of the present invention, it is important that the thickness of the film is 1.0 μm or more and 30 μm or less. A film with a thickness of less than 1.0 μm has an extremely low rigidity and is therefore poor in winding properties, whereas a film with a thickness of more than 30 μm has a high rigidity and is unlikely to exhibit the effects of the present invention. The thickness of the film can be measured with a known digital micrometer, and for example, a digital micrometer MDC-25MJ (manufactured by Mitutoyo Corporation) can be suitably used for the measurement.

[0016] The method for making the film thickness 1.0 μm or more and 30 μm or less is not particularly limited as long as it does not impair the effects of the present invention, and examples thereof include a method for adjusting the amount of molten resin extruded per unit time, a method for adjusting the slit width of a die for extruding the molten resin, a method for adjusting the stretch ratio, etc. More specifically, the thickness of the film can be reduced by reducing the amount of molten resin extruded per unit time, narrowing the slit width of the die, increasing the stretch ratio, etc.

[0017] In the film roll of the present invention, it is important that the surface roughness SRa of at least one side of the film is 0.1 nm or more and 10 nm or less. In general, the smoother the film surface, the more likely wrinkles are to occur due to the unevenness of the outer diameter of the film roll. If the SRa exceeds 10 nm, the film may not be usable for applications requiring smoothness. In addition, the lower limit of the surface roughness SRa is 0.1 nm from the viewpoint of feasibility. In the film roll of the present invention, as long as the surface roughness SRa of one side of the film is 0.1 nm or more and 10 nm or less, the surface roughness of the other side is not particularly limited, and can be arbitrarily determined according to the intended application of the film, etc.

[0018] The surface roughness SRa of the film can be measured by determining the arithmetic mean roughness (center line roughness) SRa (nm) from the surface profile curve obtained by a three-dimensional micro surface profiler in accordance with JIS B0601 (1994). The three-dimensional micro surface profiler is not particularly limited as long as it is capable of measurement, and known ones (e.g., ET-350K (manufactured by Kosaka Manufacturing Co., Ltd.) can be suitably used.

[0019] The method for making the surface roughness SRa of the film 0.1 nm or more and 10 nm or less is not particularly limited as long as it does not impair the effects of the present invention, and examples thereof include a method of adjusting the surface roughness of a rotating cooling drum that cools and solidifies a molten resin extruded into a sheet, a method of making the film (the outermost layer in the case of a laminated structure) contain particles, and a method of forming a layer by applying a coating liquid containing particles to the film surface, etc. More specifically, the surface roughness SRa of the film can be increased by increasing the surface roughness of the rotating cooling drum, increasing the particle size of the particles contained in the film or the coating liquid applied to the film, and increasing the amount of particles.

[0020] In addition, the present invention is preferably a film roll with a winding length of 5,000 m or more. A longer winding length of the film is preferable from the viewpoint of industrial-scale productivity, but the number of times the film is laminated to cause thickness unevenness in the film when it is made into a film roll increases, so that the unevenness in the outer diameter of the film roll becomes more pronounced and wrinkles are likely to occur. Furthermore, when a user applies a resin layer to the film unrolled from the film roll and rewinds it, the problem of the uniformity of the applied resin layer being impaired due to the influence of the lamination of thickness unevenness of the film becomes prominent. However, by applying the present invention, even if the winding length of the film is 5,000 m or more, a film roll can be obtained that can reduce the occurrence of poor uniformity of the resin layer when used by the user. The upper limit of the winding length of the film is generally about 30,000 m.

[0021] The method for producing a film roll of the present invention has an evaluation step in which, in order to confirm a state of unevenness in film thickness such that parameter A obtained from a width direction outer diameter change curve of a film roll 30 days after winding is 320 μm or less, a change in width direction outer diameter of an evaluation film roll that has been wound up with a surface layer hardness of 98 degrees or more is measured immediately after winding, and parameter A obtained from the obtained outer diameter change curve is evaluated.

[0022] By evaluating parameter A, which is the vertical distance between adjacent convex and concave portions spaced at an interval of less than half the film roll width in the width direction outer diameter change curve immediately after winding of a film roll wound with a surface hardness of 98 degrees or more, it becomes possible to predict parameter A of a film roll 30 days after winding immediately after winding, and to clarify the locations where control of film thickness unevenness, which is the cause of unevenness in the outer diameter in the width direction of the film roll, is required. Therefore, by providing such an evaluation process, it becomes possible to adjust thickness unevenness based on accurate film thickness unevenness evaluation results without a time delay between the production and evaluation of the film roll, and the occurrence of poor uniformity of the resin layer during use by users can be reduced.

[0023] The surface hardness of the film roll can be measured using an Asker rubber hardness tester type C in accordance with JIS-K7312.

[0024] According to another method of the present invention, the method for producing a film roll includes an evaluation step of evaluating parameter B (B: difference (vertical distance) between the maximum outer diameter at a convex portion and the minimum outer diameter at a concave portion between adjacent convex and concave portions in the predicted outer diameter change curve of the film roll) in a predicted outer diameter change curve of the film roll obtained from width direction thickness change data of the biaxially oriented film after stretching measured in the film production step, in order to confirm a thickness unevenness state of the film in which parameter A obtained from a width direction outer diameter change curve of the film roll 30 days after winding is 320 μm or less.

[0025] By evaluating parameter B obtained from the predicted curve of the outer diameter change of the film roll obtained from the data of the thickness change in the width direction of the biaxially oriented film after stretching measured in the film production process, it becomes possible to predict parameter A of the film roll 30 days after winding during film production, and to clarify the areas where control of the film thickness unevenness, which is the cause of the outer diameter unevenness in the width direction of the film roll, is required. By providing such an evaluation process, it becomes possible to adjust the thickness unevenness based on the accurate film thickness unevenness evaluation results without a time lag between film production and evaluation, and the occurrence of poor uniformity of the resin layer during use by users can be reduced.

[0026] The predicted curve of the outer diameter change of the film roll can be obtained by averaging the data of the thickness change in the width direction of the film after multiple stretching, calculating the moving average in the width direction of the oscillation operation amount performed during winding of the film roll, and multiplying it by the number of film laminations from the cylindrical core to the surface layer of the film roll when the film roll is made. The measurement of the data of the thickness change in the width direction of the film after stretching is not particularly limited as long as it is possible to measure it, and a known device (for example, WEBFREX NV (manufactured by Yokogawa Electric Corporation) can be suitably used.

[0027] The film manufacturing method of the present invention will be specifically described below using a biaxially stretched polyethylene terephthalate (hereinafter, sometimes referred to as PET) film produced by a sequential stretching method as an example. However, the present invention is not limited to the following embodiment.

[0028] First, PET pellets are melt-kneaded at a temperature equal to or higher than the melting point using an extruder, extruded from a die into a sheet, and solidified by contacting it with a rotating cooling drum having a surface temperature of 15° C. to 25° C. In this process, the surface roughness SRa of the finally obtained biaxially oriented film can be adjusted by adding particles to the PET pellets or adjusting the surface roughness of the rotating cooling drum, and the thickness of the finally obtained biaxially oriented film can be adjusted by adjusting the amount of resin extruded, the slit width of the die, and the stretching ratio described below.

[0029] The non-oriented film thus obtained is then stretched in the conveying direction at a temperature of 80°C to 130°C and a stretch ratio of 2 to 8 times to obtain a uniaxially oriented film. At this time, a known method (for example, a method using the difference in peripheral speed of rolls, etc.) can be suitably used for stretching in the conveying direction. Thereafter, both ends of the obtained uniaxially oriented film are held with clips and introduced into a tenter oven, preheated at a temperature of 80°C to 130°C, stretched in the width direction at a stretch ratio of 2 to 5 times, and heat-treated at a temperature of 180°C to 250°C. At this time, after the heat treatment, a relaxation treatment of more than 0% and 8% or less in the width direction may be performed as necessary. Furthermore, the film subjected to the heat treatment (or the heat treatment and the relaxation treatment) is cooled to room temperature to obtain a biaxially oriented film having a thickness of 1.0 μm to 30 μm and a surface roughness SRa of at least one side of 0.1 nm to 10 nm.

[0030] Next, the obtained biaxially oriented film is transported, the data of the change in the width direction thickness of the biaxially oriented film during transport is measured, and the edge portions on both sides in the width direction are cut and removed and wound around a cylindrical core to obtain an intermediate roll. The film is then unwound from the intermediate roll, transported, slit into a length of 5,000 m to 30,000 m, and wound around a cylindrical core again to obtain a film roll. At this time, in order to make the parameter A obtained from the outer diameter change curve obtained by measuring the outer diameter change in the width direction of the film roll 30 days after winding 320 μm or less, the following film roll evaluation process is provided, and the die slit width is adjusted based on the obtained parameter.

[0031] A. An evaluation film roll is prepared by winding it up with a surface hardness of 98 degrees or more, and parameter A, which is the difference (vertical distance) between the maximum outer diameter at the convex part and the minimum outer diameter at the concave part between adjacent convex and concave parts spaced at an interval of up to half the film roll width, is evaluated in the width direction outer diameter change curve of the evaluation film roll immediately after winding. When a film roll with parameter A exceeding 320 μm is observed in this inspection process, the mouthpiece slit width of the relevant part is adjusted, so that parameter A obtained from the outer diameter change curve obtained by measuring the change in the width direction outer diameter of the film roll 30 days after winding can be made 320 μm or less.

[0032] B. Parameter B obtained from a predicted curve of change in outer diameter of a film roll obtained from data on change in widthwise thickness of the biaxially oriented film after stretching measured in the film production process is evaluated. When a film roll with parameter B exceeding 320 μm is observed in this inspection process, the mouthpiece slit width of the relevant portion can be adjusted to make parameter A obtained from the curve of change in outer diameter obtained by measuring the change in widthwise outer diameter of the film roll 30 days after winding 320 μm or less. EXAMPLES

[0033] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. For each example and comparative example, measurements and evaluations of each item were carried out by the methods shown below.

[0034] [Measurement method] A. Film thickness The film was unwound from the film roll, and the thickness was measured at 10 points on a line drawn parallel to the width of the film using a digital micrometer MDC-25MJ (manufactured by Mitutoyo Corporation), and the average value was taken as the film thickness (μm).

[0035] B. Surface roughness of the film SRa Both sides of the film were measured using a three-dimensional micro surface profiler (ET-350K manufactured by Kosaka Manufacturing Co., Ltd.), and the arithmetic mean roughness (center line roughness) SRa (nm) of each surface was calculated from the profile curves of each surface according to JIS B0601 (1994). The measurement conditions were as follows, with the X direction being the width direction of the sample and the Y direction being the length direction of the sample. X-direction measurement length: 0.5mm X-direction feed rate: 0.1mm / sec Y-direction feed pitch: 5μm Number of lines in Y direction: 40 Cutoff: 0.25mm Stylus pressure: 0.02mN Height (Z direction) magnification: 50,000 times

[0036] C. Parameter A obtained from the outer diameter change curve of the film roll Using a bulk shape measuring instrument manufactured by Hamano Seiki Co., Ltd., continuous outer diameter data was measured in the width direction from the measurement starting point 5 mm inside the end of the film roll to the measurement ending point 5 mm inside the end of the film roll opposite the measurement starting point. In the outer diameter change curve obtained by plotting the width direction on the x-axis and the outer diameter on the y-axis, for two adjacent convex and concave portions spaced apart by less than half the film roll width, the difference between the maximum outer diameter at the convex portion and the minimum outer diameter at the concave portion was defined as parameter A.

[0037] D. Parameter B obtained from the film roll outer diameter change prediction curve Using a Yokogawa Electric WEBFREX NV (online thickness meter), continuous thickness data was measured every minute from one end in the width direction of a biaxially oriented film that had been biaxially stretched and heat-treated (or heat-treated and relaxed), and cooled to room temperature during transport, to the other end. The width direction was plotted on the x-axis and the thickness on the y-axis to obtain multiple thickness change curves. For the obtained thickness change curves, n pieces of thickness data obtained during the transport time of the film being wound onto the film roll for n minutes were averaged to obtain an average thickness change curve, and then the average thickness curve was moved in the width direction over an oscillation width of 100 mm performed during the film roll winding to obtain a predicted curve of the outer diameter change of the film roll. In the predicted curve of the outer diameter change of the film roll, the difference between the maximum outer diameter of the convex part and the minimum outer diameter of the concave part was defined as parameter B for two adjacent convex parts and concave parts spaced within a distance of 2 / 2 of the film roll width.

[0038] E. Wrinkle defect on film roll The film rolls six months after winding were visually observed and rated according to the following criteria. The evaluation results were ◯ and △, which were considered to be acceptable. ○: No wrinkles were observed. △: Wrinkles were generated that could not be seen by the naked eye when pulled with fingers. ×: Visible wrinkles were generated even when pulled with fingers.

[0039] F. Evaluation of uniformity of resin layer applied to film When a resin layer to be transferred was applied to a film unwound from a film roll and then rewound, the uniformity of the resin layer, which was affected by the lamination of uneven thickness of the film, was evaluated as follows.

[0040] Photoclear (siloxane resin) manufactured by Toray Industries, Inc. was applied to the film unwound from the film roll so that the thickness after drying was 1 μm with a die coater, and after drying in an oven at 120 ° C, the coated side was covered with a film unwound from another film roll, and with the coated resin sandwiched between the films, a roll length of 400 m was wound up on a cylindrical core with a surface hardness of 96 degrees to create a roll for evaluating resin uniformity. After one month, the resin sandwiched between the films was unwound from the resin uniformity evaluation roll, and projected onto a screen with a backlight of 1500 lux to observe the roll length where a shadow was generated due to resin deformation, and evaluated according to the following criteria. The evaluation was deemed to be acceptable if it was ◯ or △. ○: Shadows caused by resin deformation only occur within 10 m of the cylindrical core. △: Shadows caused by resin deformation only occur within 50 m of the cylindrical core. ×: Shadows caused by resin deformation occurred more than 50 m away from the cylindrical core.

[0041] [Raw resin composition] The following materials were used in producing the films of the Examples and Comparative Examples. PET1: Polyethylene terephthalate (manufactured by Toray Industries, Inc.) PET2: PET1 to which 0.1% by mass of synthetic colloidal silica particles with a volume average particle size of 0.06 μm and 0.71% by mass of alumina particles with a volume average particle size of 0.015 μm have been added. PET3: PET1 to which 0.06% by mass of highly cross-linked polystyrene particles with a volume average particle size of 0.3 μm, 0.04% by mass of highly cross-linked polystyrene particles with a volume average particle size of 0.80 μm, and 0.71% by mass of alumina particles with a volume average particle size of 0.015 μm have been added. PET4: PET1 to which 0.10% by mass of highly cross-linked polystyrene particles with a volume average particle size of 0.3 μm and 0.10% by mass of calcium carbonate particles with a volume average particle size of 1.05 μm have been added.

[0042] [Example 1] PET1, PET2, and PET3 were melted and extruded at a temperature of 285°C in separate extruders, and the three types were laminated in three layers in the order of PET2 / PET1 / PET3, and then extruded into a sheet from a die and solidified by adhering it to a rotating cooling drum at 25°C to obtain a non-oriented film. Next, the obtained non-oriented film was stretched in the longitudinal direction using the peripheral speed difference of the roll under conditions of a temperature of 120°C and a stretching ratio of 5.0 times to obtain a uniaxially oriented film. Next, both ends of this uniaxially oriented film were held with clips and introduced into a tenter oven, preheated at 105°C, and then stretched 4.0 times in the width direction. Then, it was further heat-treated at 230°C and relaxed 3.0% in the width direction at 150°C, and then cooled to obtain a biaxially oriented film. The biaxially stretched film thus obtained was conveyed, and the width direction thickness change data of the biaxially oriented film during conveyance was measured, and the slit width of the die was adjusted so that the parameter B of the outer diameter change prediction curve of the film roll obtained from the width direction thickness change data was 250 μm. After adjusting the slit width of the die, the edge portions on both sides of the conveying film in the width direction were cut and removed, and the film was wound around a cylindrical core to obtain an intermediate roll with a width of 5,000 mm and a wound length of 30,000 m. Next, the film was unwound from the obtained intermediate roll at a conveying speed of 400 m / min, slit to a film width of 1,600 mm, and wound around a cylindrical core again to obtain a film roll with a width of 1,600 mm and a wound length of 15,000 m. The obtained film roll was evaluated for parameter A obtained from the outer diameter change curve of the film roll 1 day, 30 days, and 6 months after winding, as well as for wrinkle evaluation and evaluation of the uniformity of the resin layer applied to the film. Furthermore, a film roll of the same width and length was obtained from the same intermediate roll by adjusting the winding tension to obtain a film roll for evaluation with a surface layer hardness of 98 degrees, and the parameter A obtained from the outer diameter change curve of the film roll immediately after winding was evaluated. In addition, the parameter B obtained from the outer diameter change prediction curve of the film roll was evaluated using the width direction thickness change data of the biaxially stretched film during conveyance. The evaluation results for each item are shown in Table 1.

[0043] [Example 2] A film roll was obtained in the same manner as in Example 1, except that the winding length of the film roll was 5,000 m and parameter B was 300 μm. Parameter B was changed by adjusting the slit width of the die. The obtained film roll was evaluated for parameter A obtained from the outer diameter change curve of the film roll 5 days, 30 days, and 6 months after winding, as well as for wrinkles and the uniformity of the resin layer applied to the film. The evaluation results for each item are shown in Table 1.

[0044] [Example 3] A film roll was obtained in the same manner as in Example 1, except that parameter B was set to 310 μm. The obtained film roll was evaluated for parameter A obtained from the outer diameter change curve of the film roll 5 days, 30 days, and 6 months after winding, as well as for wrinkles and the uniformity of the resin layer applied to the film. The evaluation results for each item are shown in Table 1.

[0045] [Example 4] A film roll was obtained in the same manner as in Example 1, except that the film thickness was set to 25 μm and parameter B was set to 315 μm. The obtained film roll was evaluated for parameter A obtained from the outer diameter change curve of the film roll 10 days, 30 days, and 6 months after winding, as well as for wrinkles and the uniformity of the resin layer applied to the film. The evaluation results for each item are shown in Table 1.

[0046] [Example 5] A film roll was obtained in the same manner as in Example 1, except that the layer structure and parameter B were as shown in Table 1. The obtained film roll was evaluated for parameter A obtained from the outer diameter change curve of the film roll 15 days, 30 days, and 6 months after winding, as well as for wrinkles and the uniformity of the resin layer applied to the film. The evaluation results for each item are shown in Table 1.

[0047] [Comparative Example 1] A film roll was obtained in the same manner as in Example 1, except that parameter B was set to 340 μm. The obtained film roll was evaluated for parameter A obtained from the outer diameter change curve of the film roll 20 days, 30 days, and 6 months after winding, and was also evaluated for wrinkles and uniformity of the resin layer applied to the film. Furthermore, a film roll of the same width and length was obtained from the same intermediate roll by winding and adjusting the tension to obtain a film roll for evaluation with a surface layer hardness of 97 degrees, and parameter A obtained from the outer diameter change curve of the film roll immediately after winding was evaluated. The evaluation results for each item are shown in Table 1.

[0048] [Comparative Example 2] A film roll was obtained in the same manner as in Example 1, except that parameter B was set to 330 μm. The obtained film roll was evaluated for parameter A obtained from the outer diameter change curve of the film roll 25 days, 30 days, and 6 months after winding, and was also evaluated for wrinkles and uniformity of the resin layer applied to the film. Furthermore, a film roll of the same width and length was obtained from the same intermediate roll by winding and adjusting the tension to obtain a film roll for evaluation with a surface hardness of 96 degrees, and parameter A obtained from the outer diameter change curve of the film roll immediately after winding was evaluated. The evaluation results for each item are shown in Table 1.

[0049] [Comparative Example 3] A film roll was obtained in the same manner as in Example 1, except that the thickness of the film and parameter B were as shown in Table 1. The obtained film roll was evaluated for parameter A obtained from the outer diameter change curve of the film roll 29 days, 30 days, and 6 months after winding, and was also evaluated for wrinkles and uniformity of the resin layer applied to the film. Furthermore, a film roll of the same width and length was obtained from the same intermediate roll by winding and adjusting the tension to obtain a film roll for evaluation with a surface layer hardness of 96 degrees, and parameter A obtained from the outer diameter change curve of the film roll immediately after winding was evaluated. The evaluation results for each item are shown in Table 1.

[0050] [Table 1]

[0051] In the table, P1 to P4 represent PET1 to PET4, respectively. [Industrial Applicability]

[0052] According to the present invention, even in a film roll wound with a highly smooth and thin film, the change in the outer diameter of the film roll can be reduced, and an ultra-thin film to be transferred of nano-order can be uniformly provided and uniformly transferred. The present invention can be suitably used in the manufacture of release film rolls for circuits such as dry films, which require thin and smooth substrate films and which include a process of applying a resin layer to a polyester film and rewinding it, and biaxially oriented polyester film rolls for transfer materials.

Claims

1. a film roll having a film wound around a cylindrical core, the film roll having a parameter A (A: maximum value of the difference (vertical distance) between the maximum outer diameter of adjacent convex portions and the minimum outer diameter of adjacent concave portions spaced apart by an interval of up to half the film roll width in the outer diameter change curve of the film roll in which a change in the outer diameter in the width direction of the film roll is measured 30 days after winding, the parameter A being obtained from an outer diameter change curve with the horizontal axis being the width direction and the vertical axis being the outer diameter) of 320 μm or less, the film winding length being 5,000 m or more, the film thickness being 1 μm or more and 30 μm or less, and the surface roughness SRa of at least one surface of the film being 0.1 nm or more and 10 nm or less.

2. A method for manufacturing a film roll, comprising: a film roll evaluation step of evaluating a parameter A obtained from an outer diameter change curve obtained by measuring a change in outer diameter in the width direction of an evaluation film roll wound up with a surface hardness of 98° or more immediately after winding.

3. A method for producing a film roll, comprising: a film roll evaluation step of evaluating a parameter B (B: a difference (vertical distance) between a maximum outer diameter at a convex portion and a minimum outer diameter at a concave portion, between adjacent convex and concave portions spaced apart by an interval of up to half the film roll width, in the film roll outer diameter change prediction curve) obtained from data on thickness change in the width direction of the stretched film measured in the film formation step.

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