JP7230571B2 - film roll - Google Patents

Description

The present invention relates to a film roll with less defects caused by entrained foreign matter.

Films (especially polyester films) are suitable for various industrial material applications, packaging material applications, magnetic material applications, etc., due to their excellent mechanical properties, electrical properties, dimensional stability, heat resistance, transparency, and chemical resistance. used for Especially in recent years, the market for polyester film has been increasing due to the expansion of surface protective films and reflective films for flat panel displays such as liquid crystal displays and plasma displays, touch screen panels, display plates, nameplates, window stickers, and surface decoration materials. It has grown significantly and is expected to continue to grow significantly in the future. On the other hand, in these applications, display screens are becoming higher definition and design is becoming more precise, and there is a demand for improvements in the appearance of the final product, such as very fine scratches on the polyester film and flatness. It's getting stronger.

In recent years, transparent conductive laminates typified by touch panels and the like mainly consist of a substrate layer made of polymer resin, an adhesive layer for enhancing adhesion with other members, and an adhesive layer for suppressing interference with other members. is provided, a cured resin layer called a hard coat layer is provided thereon, and a conductive layer is provided on the surface (Patent Document 1). The adhesive layer, the high refractive index layer, the hard coat layer, and the conductive layer described above are becoming thinner from the viewpoint of interference suppression and visibility, and the physical properties of the base material layer determine the final configuration of the transparent conductive laminate. may affect Therefore, the uniformity of the physical properties of the substrate is required (Patent Document 2). In particular, defects such as scratches on the film surface that have local height differences in the substrate layer cause loss of conductivity in the vapor deposition when the transparent conductive laminate is formed, which induces disconnection and defective products. can be

In order to prevent defects such as scratches on the film surface, it is important to reduce foreign matter in the film manufacturing process. There is known a method of reducing defects that occur when a film is wound around a core by specifying the pressure and tension for winding (Patent Document 3).

JP 2015-61745 A JP 2012-91496 A JP-A-2001-39590

However, in continuing operations related to film production, rust due to aged deterioration of production equipment, precipitates from the film itself, etc. may scatter, and minute foreign matter may increase in the production process. In such a case, foreign matter is involved when the film is wound around the core to form a film roll, so that the resulting film roll has a problem that defects having local height differences such as scratches due to the foreign matter. was there.

As a method for reducing defects caused by such entrapped foreign matter, a method for winding a polyester film is proposed in Patent Document 3. However, in recent years, since optical members such as displays exhibit finer performance, it is required to suppress even finer defects. However, the effect was not sufficient for suppressing defects such as scratches in the film and for suppressing finer defects.

An object of the present invention is to provide a film roll having fewer defects caused by entrained foreign matter in view of the problems in the prior art.

The present invention employs the following means in order to solve such problems. i.e.
(1) Decrease in hardness when H _A is the hardness at a point 5 mm away from the surface of the core, _HB is the hardness of the surface of the film roll, and D _B (mm) is the distance from the surface of the core to the surface of the film roll. ratio ((H _A −H _B )/(D _B −5)) is 0.00/mm or more and 0.70/mm or less, H _A is 900 or less, and H _B is 700 or more. A film roll characterized by:
(2) The film roll according to (1), wherein the _HA is 800 or more.
(3) The film roll according to (1) or (2), wherein the D _B is 150 mm or more and 350 mm or less.
(4) The film roll according to any one of (1) to (3), wherein the film has a thickness of 50 μm or more and 500 μm or less.
(5) The film roll according to any one of (1) to (4), wherein the film is used for optical purposes.

According to the present invention, it is possible to provide a film roll with few defects caused by entrained foreign matter.

It is sectional drawing when cutting a film roll in a width direction and a perpendicular|vertical plane.

In the film roll of the present invention, the hardness at a point 5 mm away from the surface of the core is _HA , the hardness of the surface of the film roll is _HB , and the distance from the surface of the core to the film roll surface is _DB (mm). Furthermore, the hardness reduction rate ((H _A −H _B )/(D _B −5)) is 0.00/mm or more and 0.70/mm or less, H _A is 900 or less, and H _B is 700. It is characterized by the above. Preferred embodiments for carrying out the present invention will be specifically described below.

In the film roll of the present invention, the type of resin constituting the film is not limited as long as the effects of the present invention are not impaired. Examples of resins constituting the film include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyamides, polycarbonates, polystyrene, polyvinyl alcohol, saponified ethylene-vinyl acetate copolymers, and polyacrylonitrile. , and resins such as polyacetal. Among them, from the viewpoint of transparency, dimensional stability, mechanical properties, heat resistance, and electrical properties, it is preferable that the resin constituting the film contains a polyester resin as a main component. A film containing a polyester resin as a main component is excellent in the above properties, and therefore can be preferably used, for example, as a surface protection film for a conductive film or a transparent conductive substrate film. In the present invention, "to be the main component" means to contain 50% by mass or more when the total resin component constituting the film is taken as 100% by mass.

In the film roll of the present invention, _HA is the hardness at a point 5 mm away from the surface of the core, _HB is the hardness of the surface of the film roll, and _DB is the distance from the surface of the core of the film roll to the surface of the film roll (mm). It is important that the hardness reduction rate ((H _A −H _B )/(D _B −5)) is 0.00/mm or more and 0.70/mm or less.

The hardness (H _A , _HB ) of the film roll of the present invention was measured using a paper/film roll hardness tester PAROtester (manufactured by Proceq, Switzerland) and an attached D It can be measured using a mold impact device.

FIG. 1 is a cross-sectional view of the film roll cut along a plane perpendicular to the width direction. A film roll 1 is a roll in which a film 3 is wound on a core 2 . The measurement position of H _A is a point 6 (hereinafter referred to as measurement position A ). The measurement position of _HB is point 7 (hereinafter referred to as measurement position B) on the surface of the film roll on the straight line. At each of the above measurement points, 10 measurement points are provided at equal intervals in the width direction of the film roll, the hardness is measured at each measurement point, and the average values obtained are defined as _HA and _HB , respectively. In the actual measurement, measurement is first performed at the measurement position B, and then measurement is performed at the measurement position A after cutting the film on the core. D _B is the distance between point 5 on the surface of the core and point 7 on the surface of the film roll.

A hardness reduction rate exceeding 0.70/mm means that the closer to the surface layer of the film roll, the greater the air content between the films. If the film roll is in such a state, the film may slightly move when the air is released due to the surface pressure, and the number of scratches caused by foreign matter caught in the film may increase. On the other hand, a hardness reduction rate of less than 0.00/mm means that H _A is smaller than H _B , but such a state cannot normally be realized. When the film is wound around the core, the film is wound while tension is applied. When a film roll is formed, the internal stress due to this tension is applied in the direction of the winding core of the roll, and the inner layer is inevitably hard-wound. Even if a film roll with a hardness reduction rate of less than 0.00 / mm can be realized, the inner layer has a higher air content between the films, and when the air in the inner layer is released due to tight winding due to the tension of the film. It is considered that the films are rubbed against each other, and the scratches are generated starting from foreign matter caught in the films. That is, the hardness reduction rate ((H _A −H _B )/(D _B −5)) is 0.00/mm or more and 0.70/mm or less, so that scratches caused by foreign matter caught in the film roll etc. can be reduced. From the above viewpoint, the hardness reduction rate is preferably 0.00/mm or more and 0.60/mm or less, more preferably 0.00/mm or more and 0.50/mm or less, and 0.00/mm or more and 0.30/mm More preferred are:

It is important that the film roll of the present invention has a surface hardness _HB of 700 or more. An _HB less than 700 means excessive air content in the film roll. If the film roll is in such a state, the film may slightly move when the air is released due to the surface pressure, and the number of scratches caused by foreign matter caught in the film may increase. Also, _HB is preferably 850 or less. When _HB exceeds 850, the contact pressure between the film and the foreign matter caught in the film is high, so that the foreign matter caught in the film may be easily transferred.

It is important that the film roll of the present invention has an _HA of 900 or less. _HA exceeding 900 means excessive internal stress applied to the film roll. When the film roll is in such a state, the contact pressure between the films is high, so that foreign matter caught in the film, a step at the beginning of the film winding, etc. may be easily transferred. On the other hand, the lower limit of _HA is not particularly limited as long as it does not impair the effects of the present invention. However, from the viewpoint of reducing the occurrence of scratches and the like, _HA is preferably 800 or more. By setting _HA to 800 or more, entrainment of air is reduced, so that friction between films due to tight winding and scratches due to entrained foreign matter are suppressed.

The method of adjusting the hardness reduction rate to 0.00/mm or more and 0.70/mm or less, _HB to 700 or more, and _HA to 900 or less is not particularly limited as long as it does not impair the effects of the present invention. A method of adjusting the winding conditions described below using a contact roll system in which the contact roll is wound while being pressed against the film roll being taken may be used. More specifically, by reducing the winding speed, increasing the surface pressure and winding tension in the winding process, etc., within the preferable range described later, the hardness decrease rate is reduced and _HA and _HB are increased. can do.

The winding speed in the winding process when manufacturing the film roll of the present invention is preferably 50 m/min or more and 150 m/min or less, more preferably 60 m/min or more and 120 m/min or less. _By setting the winding speed _to 150 m/min or less, excessive entrainment of air into the film roll is reduced. The occurrence of scratches and the like caused by foreign matter that is involved is reduced. On the other hand, by setting the winding speed to 50 m/min or more, the time required for winding does not excessively increase, and the product production efficiency per hour is maintained.

Further, the surface pressure (contact pressure by the contact roll) in the winding step is preferably 100 N/m or more and 500 N/m or less, more preferably 170 N/min or more and 440 N/min or less. By setting the surface pressure in the winding process to 100 N / m or more, the entrainment of air is reduced, so it becomes easy to reduce the hardness reduction rate and increase H _A and H _B , and the entrained foreign matter Occurrence of scratches and the like caused by is reduced. On the other hand, by setting the surface pressure in the winding process to 500 N/min or less, it is possible to reduce the transfer to the film of scratches caused by the foreign matter that has been wound in, steps at the start of film winding, and the like.

The winding tension in the winding step is preferably 200 N/m or more and 400 N/m or less, more preferably 200 N/m or more and 250 N/m or less. By setting the winding tension to 200 N/m or more, even when winding a relatively thick film having a thickness of 50 μm or more, the effect of bending rigidity is reduced, and the film being wound can easily follow the roll shape. Therefore, minute slackness and slight movements of the film due to insufficient follow-up are reduced, and the occurrence of scratches and the like caused by foreign matter caught in is reduced. On the other hand, by setting the winding tension to 400 N/m or less, the internal stress of the film roll can be suppressed, and the transfer to the film of scratches caused by foreign matter that has been rolled up and steps at the start of film winding can be reduced.

Also, the winding speed, the surface pressure in the winding process, and the winding tension may be gradually decreased or increased while winding the film as long as the effects of the present invention are not impaired.

The film roll of the present invention preferably has a D _B of 150 mm or more and 350 mm or less. By setting the D _B to 150 mm or more, the length of the film per film roll is sufficiently maintained, so the increase in the number of times the film roll is replaced during manufacturing is suppressed, and production efficiency can be kept good. can. On the other hand, by setting the D _B to 350 _mm or less, the increase in the outer diameter and weight of the product is reduced, and the handling property such as transportation of the film roll is improved. Furthermore, it is possible to reduce the transfer to the film of scratches caused by foreign matter that is caught in the film, and steps at the beginning of the film winding.

Means for setting D _B to 150 mm or more and 350 mm or less are not particularly limited as long as the effects of the present invention are not impaired, but examples thereof include a method of adjusting the length of the film wound on one film roll. More specifically, _DB can be increased by lengthening the film wound on one film roll.

The film roll of the present invention preferably has a film thickness of 50 μm or more and 500 μm or less. By setting the thickness of the film to 50 μm or more, it is possible to reduce the transfer of foreign matter caught in the film to the film. On the other hand, by setting the thickness of the film to 500 μm or less, it becomes easy to reduce the transfer of the steps to the film at the start of winding.

The film roll of the present invention is a film roll with few defects caused by entrained foreign matter. Therefore, the film in the film roll of the present invention can be preferably used for optical applications, surface protection applications for conductive films, transparent conductive substrate applications, and the like, and can be particularly suitably used for optical applications.

Hereinafter, the method for producing a film roll of the present invention will be specifically described by taking a roll of polyethylene terephthalate (hereinafter sometimes referred to as PET) film as an example. However, the present invention is not limited to the embodiments described below.

First, PET chips are put into a melt extruder and melted. Thereafter, the extruded amount is made uniform by a gear pump or the like, and the heat-melted PET is extruded, and foreign substances and gelled substances are removed by a filter. At this time, one extruder or a plurality of extruders may be used. When a plurality of extruders are used, the PET that has passed through the filter is fed into the lamination device. As a lamination device, a multi-manifold die, a feed block, a static mixer, or the like can be used, and these may be combined arbitrarily.

The PET melt thus obtained is extruded into a sheet form from a die, and cooled and solidified on a cooling body such as a cast drum to obtain a non-oriented sheet. As a specific method for obtaining a non-oriented sheet from a sheet-like melted PET, a wire-shaped, tape-shaped, needle-shaped or knife-shaped electrode is used to cast the sheet-shaped melt by electrostatic force onto a cooling body such as a casting drum. A preferred method is to bring it into close contact with and rapidly solidify it. Other methods include blowing air from a slit-shaped, spot-shaped, or planar device to bring the sheet-shaped melt into close contact with a cooling body such as a casting drum to rapidly cool and solidify the sheet-shaped melt, or cooling the sheet-shaped melt with a nip roll. A method of contacting the body and rapidly cooling and solidifying is also preferred.

Next, the non-oriented sheet thus obtained is stretched in the longitudinal direction (longitudinal stretching) to obtain a uniaxially oriented sheet. The longitudinal stretching can be carried out in one stage using one or a plurality of stretching rolls with the same peripheral speed, or in multiple stages using a plurality of stretching rolls with different peripheral speeds. The temperature is preferably 70 to 100° C., and the magnification is preferably 3.0 to 5.0 times. The longitudinal direction means the running direction of a sheet or film in the manufacturing process of a film roll, and the winding direction of the film in the film roll.

Further, after the longitudinal stretching, a step of applying a coating agent for forming a functional layer such as an easy-adhesion layer on both or one side of the obtained uniaxially oriented sheet can be provided. The method of applying the coating agent is not particularly limited, and for example, a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a wire bar coating method, a die coating method, a spray coating method, or the like can be used.

After that, both ends of the uniaxially oriented sheet in the width direction are held with a plurality of clips and guided to a tenter device, preheated and the coating agent are dried, and the width of the clips is widened to stretch in the width direction (horizontal stretching). An axially oriented film is obtained. The temperature at this time is preferably 90 to 115° C., and the magnification is preferably 3.0 to 5.0 times. Further, as long as the effects of the present invention are not impaired, the stretched biaxially oriented film may be heat-treated at 200 to 250° C. in a tenter device and then cooled to impart dimensional stability. Also, a relaxation treatment of 3 to 12% in the width direction may be applied during the heat treatment. The width direction refers to a direction perpendicular to the longitudinal direction in the plane of the sheet or film in the manufacturing process of the film roll, and refers to a direction parallel to the central axis of the core in the case of the film roll.

The biaxially oriented film thus obtained is cooled in the subsequent transporting step, the width direction both ends are removed by a slitter, and the film is cut to a desired width as necessary. The film roll of the present invention can be obtained by winding the cut biaxially oriented film around a core. From the viewpoint of adjusting the hardness reduction rate to 0.00/mm or more and 0.70/mm or less, _HA to 900 or less, and _HB to 700 or more, the winding speed in the winding process is 50 m/min or more and 150 m/mm. min or less, more preferably 60 m/min or more and 120 m/min or less. The surface pressure is preferably 100 N/m or more and 500 N/m or less, more preferably 170 N/min or more and 440 N/min or less. The winding tension is preferably 200 N/m or more and 400 N/m or less, more preferably 200 N/m or more and 250 N/m or less.

The film roll of the present invention thus obtained is a film roll with few defects caused by entrained foreign matter. Therefore, the film in the film roll of the present invention can be preferably used for optical applications, surface protection applications for conductive films, transparent conductive substrate applications, and the like, and can be particularly suitably used for optical applications.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Various properties were measured by the following methods.

(1) Film thickness Cut the film into A4 size, measure any 20 points using a dial gauge ("No2110S-10" manufactured by Mitutoyo), and calculate the first decimal place of the average value obtained. The rounded value was taken as the film thickness (μm).

(2) Roll radius, D _B
From the core radius, the film roll length, and the film thickness measured by the method (1), the roll radius (mm) was calculated by the following formula 1 (rounded off to the first decimal place). Furthermore, _DB was obtained by subtracting the core radius from the obtained value of the roll radius and rounding off. The core radius is 83.5 mm in all examples and all comparative examples.
Formula 1:
Roll radius [mm] = ((winding length [m] x film thickness [μm]) / π + (core radius [mm]) ² ) ^0.5
(3) Hardness, hardness reduction rate As explained using FIG. was used to measure the hardness. At each measurement point, 10 points are measured at equal intervals in the width direction of the film roll, 10 measured values (integers) are averaged, and the values obtained by rounding off to the first decimal place are _HA and _HB , respectively. bottom. Furthermore, from H _A , H _B , and D _B measured by the method of (2), ((H _A −H _B )/(D _B −5)) is calculated, and the obtained value is placed to the third decimal place. The value obtained by rounding off was taken as the hardness reduction rate (/mm). Regarding the measurement of H _A and H _B , H _B was measured first, then the film roll on the core was cut up to the measurement position A and H _A was measured.

(4) Dust content A hand-held airborne particle counter (MET ONE, HHPC3+, manufactured by Beckman Coulter, USA) was used to measure the content of dust of 2 µm or more in the atmosphere during the winding process.

(5) Transfer trace A film was sampled from measurement positions A and B of the film roll wound around the core so that the area was 1 m ² . After that, each sample was held in an oven set at a temperature of 150° C. for 10 minutes without tension, and then cooled at room temperature for 10 minutes. The obtained sample was irradiated with light from a fluorescent lamp, and the state of the reflected image of the fluorescent lamp projected on the film surface by the reflected light was visually confirmed and evaluated according to the following criteria. In addition, when the measurement results differed between the measurement positions A and B, the worse result was adopted.
◯: No distortion was observed in the reflected image of the fluorescent lamp.
Δ: Distortion was observed in the image reflected by the fluorescent lamp, but when the film was placed in an oven set at 150° C. for 10 minutes without tension, no distortion was observed in the image reflected by the fluorescent lamp.
x: Distortion was observed in the reflected image of the fluorescent lamp even after being kept in an oven set at 150°C for 10 minutes without tension.

(6) Number of Scratches Sampling Sampling was performed from measurement positions A and B of the film before winding the film around the core and the film roll wound around the core so as to have an area of 1 m ² . In a darkroom, one side of the film sample was observed from the light irradiation side while changing the incident angle from 30° to 150° horizontally with respect to the film sample with a 2000 lx LED light (EB-10KM manufactured by OHM). , Sampling of scratches that can be confirmed visually. The sampled scratches were observed with a laser microscope, and scratches having a depth of 0.3 μm or more and a length of 0.3 mm or more were counted. Five film samples were tested, and the average value was defined as the number of scratches increased before and after the film was wound around the core, and evaluated according to the following criteria. In addition, when the measurement results differed between the measurement positions A and B, the worse result was adopted.
◎: Increased number of scratches ≤ 0 / m ²
○: 0/m ² <Number of scratches increased ≤ 1/m ²
△: 1/m ² < number of scratches increased ≤ 5/m ²
×: 5/m ² <Number of scratches increased.

(Resins, etc. used for manufacturing films)
Preparation methods of resins and the like used in Examples and Comparative Examples are shown as Reference Examples.

[Reference Example 1] Preparation of polyethylene terephthalate (PET) Using terephthalic acid as an acid component and ethylene glycol as a glycol component, antimony atom conversion of 300 ppm is applied to polyester pellets to obtain antimony trioxide (polymerization catalyst). to carry out a polycondensation reaction to obtain a particle-free PET having an intrinsic viscosity of 0.63 dl/g, a carboxyl terminal group content of 40 equivalents/ton and a glass transition temperature (Tg) of 74°C. The intrinsic viscosity is a value measured in o-chlorophenol at 25° C. according to JIS K 7367 (2000), and the carboxyl terminal group content is a value measured by the procedure described below according to Maulice's method. (Reference: MJ Maulice, F. Huizinga, Anal. Chim. Acta, 22, 363 (1960)). Further, Tg is a value measured by increasing the temperature from 25° C. to 300° C. at a rate of 20° C./min according to JIS K 7121 (1987). A thermal differential scanner was used, and data analysis was performed using a Disk Session SSC/5200 manufactured by the same company.

The procedure for measuring the amount of carboxyl terminal groups will be specifically described below. First, 2 g of a measurement sample was dissolved in 50 mL of o-cresol/chloroform (mass ratio 7/3) at a temperature of 80°C. After that, titration was performed with a 0.05N KOH/methanol solution to measure the terminal carboxyl group concentration, which was expressed as the equivalent weight/1t of polyester. At this time, phenol red was used as an indicator during the titration, and the end point of the titration was determined when the color changed from yellowish green to light red. If the solution in which the measurement sample is dissolved contains insoluble matter such as inorganic particles, the solution is filtered to measure the mass of the insoluble matter. was corrected to be the mass of

[Reference Example 2] Preparation of acrylic resin paint In 300 parts of water serving as a solvent under a nitrogen gas atmosphere, 1 part by weight of Na p-dodecylbenzenesulfonate as an emulsifier, 65 parts by weight of methyl methacrylate (MMA) as a monomer, 30 parts by mass of ethyl acrylate (EMA), 3 parts by mass of N-methylolacrylamide (N-MAM), and 2 parts by mass of acrylic acid (AA) were charged into an emulsion polymerization reactor, and sodium persulfate (initiator) was added thereto. After adding 100 parts by mass to 1,000,000 parts by mass of the monomer component and reacting at 30 to 80° C. for 10 hours, the pH was adjusted to 7.0 to 9.0 with an aqueous ammonia solution (alkali). . After that, unreacted monomers were removed under reduced pressure at 70° C. and concentrated to obtain an acrylic emulsion with a concentration of 35% by mass. A mixed aqueous solution in which 1 part by mass of colloidal silica having a particle size of 80 nm was added to 100 parts by mass of the obtained acrylic resin was used as a paint.

(Example 1)
The PET chips of Reference Example 1 were dried at a temperature of 180° C. for 5 hours under a reduced pressure of 3 torr, put into a melt extruder, melted at a temperature of 280° C., filtered through a filter with a filtration accuracy of 8 μm, and A sheet was extruded from a letter-shaped die. The extruded sheet material was cooled and solidified on a mirror surface casting drum having a surface temperature of 20° C. by an electrostatic casting method to obtain a non-oriented sheet. This non-oriented sheet is first preheated to 75° C. with a roll group arranged continuously, then heated with rolls at 95° C., and heated 3.5 times in the longitudinal direction while heating the sheet surface with a radiation heater. to obtain a uniaxially oriented sheet. Using a bar coater, the paint of Reference Example 2 was applied to both surfaces of the uniaxially oriented sheet so that the coating layer thickness after drying was 60 nm. A metering wire bar having a diameter of 13 mm and a wire diameter of 0.1 mm (#4) was used. Both ends of the uniaxially oriented sheet in the width direction were held with clips and led to an oven, where they were dried by heating with hot air at a temperature of 120° C. and a wind speed of 20 m/min. Subsequently, the film was continuously led to a stretching step, and stretched 3.7 times in the width direction while being heated with hot air at a temperature of 100° C. and a wind speed of 15 m/min. The resulting biaxially oriented film was continuously heat treated with hot air at a temperature of 230°C and a wind speed of 20 m/min for 15 seconds, and then cooled from 230°C to 120°C while being subjected to a relaxation treatment of 5% in the film width direction. application followed by cooling to 50°C. Subsequently, after removing both ends in the width direction, the film was wound up to obtain a polyester film having a thickness of 188 μm. The resulting film was slit to a predetermined width and wound around a plastic core (FWP core, manufactured by Tenryu Composite Co., Ltd.) having an outer diameter of 167 mm under the winding conditions and roll radius shown in Table 1 to obtain a film roll. Each item was evaluated for the obtained film roll. Table 1 shows the evaluation results for each item. The dust level of 2 μm or larger during the process of winding the film onto the core was 8,000 particles/cubic foot.

(Examples 2-8, Comparative Examples 1-5)
Film formation was performed in the same manner as in Example 1 except that the film thickness was changed as shown in Table 1, and a polyester film was obtained. A film roll was obtained by winding under the winding conditions and roll radius. Table 1 shows the evaluation results for each item.

According to the present invention, it is possible to provide a film roll with few defects caused by entrained foreign matter. The film constituting the film roll of the present invention can be preferably used for optical applications, surface protection applications for conductive films, transparent conductive substrate applications, and the like.

1: film roll 2: core 3: film 4: center point of core 5: point on surface of core 6: point 5 mm away from surface of core (measurement position A)
7: Points on the surface of the film roll (measurement position B)

Claims (5)

_The hardness reduction _{rate (} ( H _A −H _B )/(D _B −5)) is 0.00/mm or more and 0.70/mm or less, H _A is 900 or less, and H _B is 700 or more. Yes, film roll. 2. The film roll of claim 1, wherein the _HA is 800 or more. 3. The film roll according to claim 1, wherein the D _B is 150 mm or more and 350 mm or less. 4. The film roll according to any one of claims 1 to 3, wherein the thickness of the film is 50 µm or more and 500 µm or less. 5. The film roll according to claim 1, wherein the film is used for optical purposes.

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