JP2014015319A - Method for transporting film and method for manufacturing optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for transporting a film nipping a film with a touch roll, and not causing creases on the film on a tension roll for transporting the film in a tense state, and provide a method for manufacturing an optical film.SOLUTION: In a method for transporting a film, while a film 1 is tensed by a tension roll 2, the vicinity of a contact start position of the film 1 with the tension roll 2 is nipped by a touch roll 3 and the tension roll 2 to transport the film 1. The transport tension of the film 1 satisfies an expression [1]170≤X≤400 and a variation of transport tension, which is a difference between the maximum value and a preset value of transport tension after the film 1 is nipped by the touch roll 3, satisfies an expression [2]Y<50. In the expression [1], X is the transport tension of the film (N/m). In the expression [2], Y is the variation of the transport tension (N/m), which is a difference between the maximum value and the preset value of the transport tension after the film is nipped by the touch roll.

Description

  The present invention relates to a method for transporting a film and a method for manufacturing an optical film for preventing wrinkles generated on a film stretched on a roll in the manufacture of an optical film or the like.

  Conventionally, corona discharge treatment has been used as a film surface modification technology for the purpose of activating the film surface, improving surface properties such as adhesion and coatability (wetting), and effectively performing secondary processing. Widely known.

  The corona discharge treatment is performed by passing a film between a corona discharge electrode and a corona discharge treatment roll serving as a counter electrode, and contacting the corona discharge generated by applying a high-frequency high voltage to the electrode on the film surface. In this method, surface modification is performed by generating polar groups on the film surface. And, since such corona discharge treatment is intended to effectively perform the subsequent secondary processing by the corona discharge treatment, for example, in the production of an optical film, the following film is applied to the film subjected to the corona discharge treatment. It arrange | positions in a production line so that a process can be performed continuously.

  However, in the corona discharge treatment, the treatment effect of the corona discharge is applied only to the treated surface of the treated film. (1) The adhesion between the film and the treatment roll of the corona discharge is low. Air is interposed between the film and the corona discharge treatment roll due to the small angle of the corona discharge treatment roll and (3) the presence of wrinkles before the film is introduced into the corona discharge treatment roll. In addition, not only the treated surface but also the back surface (non-treated surface) of the film undergoes corona treatment. This penetrated film causes unevenness in wetting of the non-treated surface, processing failure due to slip performance deterioration, inhibition of releasability of the non-treated surface, and the like. Therefore, as an effective method for improving the adhesion between the film and the corona discharge treatment roll and suppressing the back-through of the film, a method in which the point where the upstream film contacts the corona discharge treatment roll is nipped by a touch roll. It has been known. (See Patent Document 1)

JP2007-314707A

  However, when the film conveyed by the touch roll is nipped when the film is subjected to the corona discharge treatment by nip the film using the touch roll to improve the adhesion between the film and the corona discharge treatment roll, There was a problem that the film on the processing roll was wrinkled.

  The present invention has been made in view of such problems, and in a film transport method in which a film is nipped by a touch roll, a film on which the film on the stretch roll that stretches and transports the film does not wrinkle. It aims at providing the manufacturing method of the conveyance method of this, and an optical film.

  As a result of studying the cause of wrinkles on a film on a stretch roll that stretches and transports the film immediately after the film nip in the film transport method using the touch roll, (1) It has been found that the phenomenon occurs when the adhesion force of the film to the stretching roll is weak, and (2) the phenomenon occurs due to a change in the conveyance tension when the touch roll nips the film. That is, the present inventors prevent the film from wrinkling by bringing the film and the stretch roll into close contact with each other under an appropriate transport tension and suppressing fluctuations in the transport tension when the touch roll nips the film. The present invention has been found and the present invention has been achieved.

According to the present invention,
(1) A film transport method in which the film is transported by niping the vicinity of the contact start position of the film with the stretch roll while the film is stretched with a stretch roll. And
The transport tension of the film satisfies the following formula [1], and the variation value of the transport tension, which is the difference between the maximum value of the transport tension after the film is nipped by the touch roll and the set value of the transport tension, is as follows. A film transport method is provided, wherein the film is transported so as to satisfy Formula [2],
170 ≦ X ≦ 400 [1]
Y <50 [2]
[In Formula [1], X represents the conveyance tension (N / m) of the film. ]
[In Formula [2], Y represents the fluctuation value (N / m) of the transport tension, which is the difference between the maximum value of the transport tension after the film is nipped by the touch roll and the set value of the transport tension. ]
(2) The method for transporting a film according to (1), wherein the touch roll is nipped while transport of the film is stopped,
(3) The stretch roll is a corona discharge treatment roll, and the film transport method according to (1) or (2) is provided,
(4) There is provided a method for producing an optical film comprising the film transport method according to any one of (1) to (3).

  According to the film transport method of the present invention, the film stretched on the stretch roll that stretches and transports the film is brought into close contact with the stretch roll under an appropriate transport tension, and the touch roll nips the film. Since it is possible to suppress fluctuations in the transport tension during the process, wrinkles can be prevented from occurring on the film on the stretch roll. That is, the present invention can be applied when the film is nipped and conveyed by a touch roll, and therefore, when applied to a corona discharge treatment roll, the film can be prevented from being exposed through corona discharge treatment. Can do. And since the processing defect by the back-through of corona discharge processing does not occur in the subsequent secondary processing, a high-quality optical film can be manufactured with high production efficiency.

It is a schematic diagram of the corona discharge processing apparatus which shows embodiment which concerns on the film conveyance method of this invention. It is a graph which shows the fluctuation | variation of the conveyance tension of the film at the time of implementing the film conveyance method of this invention.

  The present invention relates to a method for transporting a film and a method for manufacturing an optical film in which wrinkles are not generated on a film on a stretch roll that stretches and transports a film in a film transport method using a touch roll. is there. Details of the present invention will be described below.

  The case where the film transport method according to one embodiment of the present invention is applied to corona discharge treatment will be described with reference to the drawings. As shown in FIG. 1, the corona discharge treatment apparatus includes a plurality of corona discharge electrodes 5 each having an electrode portion 6 disposed on a corona discharge surface, and a corona discharge treatment roll 2 that serves as a counter electrode of the corona discharge electrode 5. . The film 1 is transported while being stretched by a corona discharge treatment roll 2, and the corona discharge generated from the corona discharge electrode 5 is brought into contact with the treatment surface of the film 1 to perform a corona discharge treatment. Here, when air is interposed between the film 1 and the treatment roll 2 for corona discharge, not only the treatment surface of the film 1 but also the non-treatment surface of the film 1 is corona-treated, so that the film 1 The vicinity of the contact start position with the corona discharge treatment roll 2 is nipped between the touch roll 3 and the corona discharge treatment roll 2 to improve the adhesion between the film 1 and the corona discharge treatment roll 2, and the film 1 is subjected to the corona discharge treatment. It has a structure that prevents the occurrence of show-through.

  However, when the film conveyed by the touch roll is nipped when the film is subjected to the corona discharge treatment by nip the film using the touch roll to improve the adhesion between the film and the corona discharge treatment roll, (1) There is a problem that the adhesion force of the film to the stretching roll is weak, and (2) wrinkles are generated on the film on the corona discharge treatment roll due to fluctuations in the transport tension when the touch roll nips the film.

Therefore, in order to prevent the film from being wrinkled due to the low film transport tension and the poor adhesion between the film and the corona discharge treatment roll, the present invention satisfies the following formula [1]. ) Is set, and the adhesion between the film and the corona discharge treatment roll is made appropriate.
170 ≦ X ≦ 400 [1]
[In Formula [1], X represents the conveyance tension (N / m) of the film. ]

  The film transport tension (X) in the present invention is in the range of 170 N / m or more and 400 N / m or less. If the conveyance tension (X) of the film is 170 N / m or more, the adhesion between the film and the corona discharge treatment roll can be improved, and the fluctuation of the conveyance tension when the touch roll nips the film causes the on-roll. Wrinkles can be prevented from occurring on the film. Moreover, when the conveyance tension (X) of a film exceeds 400 N / m, there exists a possibility that a film may extend in MD direction. In addition, what is necessary is just to measure the conveyance tension of a film by a well-known method with the roll provided with tension detectors, such as a tension pick-up roll.

Next, according to the present invention, the variation value (Y) of the transport tension, which is the difference between the maximum value of the transport tension after the film is nipped by the touch roll and the set value of the transport tension, satisfies the following formula [2]. It is a feature.
Y <50 [2]
[In Formula [2], Y represents a fluctuation value (N / m) of the transport tension, which is a difference between the maximum value of the transport tension after the film is nipped by the touch roll and the set value of the transport tension. ]
Here, the fluctuation value (Y) of the film transport tension represents the value of the transport tension, which is the difference between the maximum value of the transport tension after the film is nipped by the touch roll and the set value of the film transport line. FIG. 2 is a graph showing fluctuations in the conveyance tension of the film conveyance line of Example 3 in Table 1. As shown in FIG. 2, the conveyance tension of the film increases when the conveyance of the film is started after nipping with the touch roll, and the conveyance tension becomes maximum immediately after the nip of the touch roll. In addition, as shown in FIG. 2, it is preferable to control the transport tension to such an extent that the film does not wrinkle even when the film transport is stopped.

  When the fluctuation value (Y) of the conveyance tension of Examples 1 to 5 and Comparative Examples 1 to 3 in Table 1 is compared, in Examples 1 to 5, no wrinkles are generated on the film on the corona discharge treatment roll, and conveyance is performed. The fluctuation value (Y) of the tension is 14 N / m at the maximum. In Comparative Examples 1 to 3, the film wrinkles immediately after the nip of the touch roll, and the fluctuation value (Y) of the transport tension is 50 N / m or more. From these results, it is considered that wrinkles are generated on the film on the corona discharge treatment roll because Comparative Examples 1 to 3 have a large variation in conveyance tension when the touch roll nips the film. As can be seen from this result, wrinkles are generated on the film on the corona discharge treatment roll by suppressing the fluctuation of the conveyance tension so that the fluctuation value (Y) of the conveyance tension of the film satisfies the formula [2]. Can be prevented in advance.

  And in order to suppress the fluctuation | variation of the conveyance tension of a film, when this invention nips a film, it is especially preferable to carry out in the state which the conveyance of a film has stopped. Comparing Examples 3 to 5 with Comparative Examples 2 and 3 in Table 1, Comparative Examples 2 and 3 in which the film nip by the touch roll was performed while the film was being transported were stopped while the film nip was stopped by the touch roll. As a result, the variation value (Y) of the transport tension is larger than those in Examples 3 to 5 performed in the above. As can be seen from this result, the film nip by the touch roll is performed while the film transport is stopped, so that fluctuations in the film transport tension are suppressed and wrinkles are generated on the film on the corona discharge treatment roll. It can be surely prevented. Further, in Comparative Example 4 in which the film nip by the touch roll was performed while the film conveyance was stopped, the wrinkle of the film was generated although the fluctuation value of the conveyance tension was as small as 8 N / m. This result is considered that wrinkles were generated in the film due to smaller fluctuations in the conveyance tension because the conveyance tension of the film was low and the adhesion between the film and the corona discharge treatment roll was weak. As can be seen from this result, the film and the corona discharge treatment roll are brought into close contact with each other under an appropriate transport tension so that the transport tension (X) of the film satisfies the formula [1], and further, the fluctuation value of the transport tension of the film. By suppressing the fluctuation of the conveyance tension so that (Y) satisfies the formula [2], wrinkles can be prevented from occurring on the film on the corona discharge treatment roll.

  Here, the implementation method which performs the nip of the film by the touch roll which concerns on the film conveyance method of this invention in the state which the film conveyance has stopped is illustrated. In the production of an optical film, when production is started, first, the film is passed through the entire pass line, and the film is stretched on a treatment roll for corona discharge. Next, tension is applied to the film so as not to cause wrinkles on the film, and the film and the corona discharge treatment roll are brought into close contact with each other. Then, in order to improve the adhesion between the film and the corona discharge treatment roll and prevent the film from coming out of the corona discharge treatment, the film is nipped by the touch roll while the film transport is stopped. The film conveyance is started so that the film conveyance tension satisfies the formula [1]. By setting it as such a film conveyance method, the fluctuation | variation of the film conveyance tension | tensile_strength can be suppressed and it can prevent beforehand that wrinkles generate | occur | produce in the film on the processing roll of a corona discharge.

  The material of the corona discharge treatment roll used in the present invention is a roll made of metal such as iron, aluminum, and stainless steel, and the surface may be subjected to hard chrome plating or nickel plating. Furthermore, it is particularly preferable that thermal spraying of tungsten carbide or the like is performed so that the releasability is good and the mirror surface can be polished. Moreover, the surface may be coat | covered with the insulator, for example, ceramic, glass, a synthetic resin, a synthetic rubber, etc. are mentioned. The coating method includes, but is not limited to, plating, thermal spraying, vapor deposition, and coating.

  The diameter of the corona discharge treatment roll used in the present invention can be appropriately selected according to the specifications of the corona discharge treatment apparatus. In the present invention, the diameter is preferably from 150 mm to 600 mm, more preferably from 400 mm. 600 mm. If the diameter of the treatment roll is large, the contact area between the film and the treatment roll becomes large, so that a plurality of corona discharge electrodes can be installed, and the film can be subjected to corona discharge treatment in multiple stages. However, the larger the roll diameter, the lower the adhesion between the treatment roll and the film.

  The holding angle of the treatment roll by the film in the present invention can be appropriately selected according to the specifications of the corona discharge treatment apparatus, but in the present invention, it is preferably 90 ° or more and 270 ° or less. Moreover, as shown in FIG. 1, the holding angle of the processing roll by the film here refers to the center point of the processing roll when viewed from a cross section perpendicular to the processing roll axial direction, the film on the film feeding side, and the processing roll. Is an angle α formed by a straight line connecting the contact start points of the film and a straight line connecting the center point of the processing roll and the contact end point of the film on the film winding side and the processing roll. When the holding angle of the treatment roll by the film is 90 degrees or more and 270 degrees or less, the film can be subjected to uniform corona discharge treatment.

  The purpose of the touch roll used in the present invention is to nip a film between the touch roll and the processing roll to improve the adhesion between the film and the processing roll. The touch roll preferably nips the vicinity of the contact start position between the upstream film and the corona discharge treatment roll. As used herein, the vicinity of the contact start position between the film and the processing roll refers to the center point of the processing roll and the contact start point between the film on the film feeding side and the processing roll when viewed from a cross section perpendicular to the processing roll axial direction. Is an angle formed by a straight line connecting the center point of the processing roll and the straight line connecting the nip point of the touch roll is 30 degrees or less.

  As the material of the touch roll used in the present invention, at least the surface is a roll made of an elastic layer, and the metal roll is covered with a rubber-based material as long as it has a buffering effect when the film is nipped. It may be configured. As a material for the elastic layer, for example, chloroprene rubber, silicon rubber, fluorine rubber, EPDM, NBR, or the like can be suitably used. The elastic layer may be mixed with conductive carbon black, a metal filler, or a conductive resin for the purpose of preventing charging. By imparting electrical conductivity to the surface of the touch roll, it is possible to prevent the surface of the touch roll from being charged, and to reduce the adhesion of foreign matters such as dust and dust.

  The diameter of the touch roll used in the present invention is not particularly limited as long as it does not impair the adhesion between the film and the roll, and is, for example, 50 mm to 300 mm.

  The touch roll used in the present invention may take any driving method as long as it does not impair the adhesion between the film and the roll, and the touch roll follows the film without having a driving source. In the form of driving, the touch roll may have a driving source and may be driven in synchronization with the film conveyance line speed.

  The nip pressure of the touch roll used in the present invention is not particularly limited. For example, a method in which the nip pressure is adjusted using the pressure of compressed air may be used. In addition, as the nip pressure of the touch roll used in the present invention, the film does not deform, the adhesiveness between the film and the treatment roll can be sufficiently secured, and no air is interposed between the film and the treatment roll. Any pressure can be used. For example, the linear pressure is 0.1 kg / cm to 10 kg / cm. Note that the nip pressure of the touch roll may be measured using a known method such as a pressure measurement film, and “Prescale” (registered trademark, manufactured by FUJIFILM Corporation) is well known as the pressure measurement film. ing.

The film used in the present invention is a film made of a polymer having an optical element that can be suitably used as an optical film, or a film made of a polymer that can be used as a base material for providing an optical functional layer having an optical element. is there. Moreover, the film does not need to be a single layer, and may be a multilayer composed of the same polymer or different polymers, and further a protective film may be laminated on one side or both sides of the film. Examples of the polymer herein include cellulose ester resins such as cellulose diacetate, cellulose triacetate, and cellulose acetate butyrate, polyesters such as polycarbonate, polyarylate, polysulfone, polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polyethylene , Polyolefins such as polypropylene and polymethylpentene, polyvinylidene chloride, polyvinyl alcohol, ethylene vinyl alcohol resins, cycloolefin resins such as cycloolefin polymers and cycloolefin copolymers, amide resins such as polyether ketone, polyimide and nylon, Examples thereof include acrylic resins such as fluorine resins and polymethyl methacrylate. Among these materials, a film made of a cycloolefin resin as an optical film is preferably used because it is excellent in moisture resistance, heat resistance and transparency and has a small photoelastic coefficient.
Among these materials, a film made of polyolefin such as polyethylene or polypropylene or a film made of polyester such as polyethylene terephthalate is preferably used as the protective film because it has good scratch resistance and cost merit.
In addition, a well-known additive may be mix | blended with said film according to the objective. Examples of the additive include an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a nucleating agent, an antifogging agent, an antiblocking agent, and a retardation developing agent. The said additive can use 1 type (s) or 2 or more types.

Hereinafter, the film conveyance method of the present invention will be described in more detail with reference to examples. In addition, the measuring method and evaluation method of the physical property performed in the Example are as follows.
(1) Set value of transport tension (X)
It is a set value of the conveyance tension when the film conveyance line is driven. The unit was expressed as (N / m).
(2) Fluctuation value of transport tension (Y)
The transport tension was measured using a tension detector equipped with a tension pickup roll, and the difference between the maximum value of the transport tension of the film and the set value of the transport tension was calculated. The unit was expressed as (N / m).
(3) Touch roll nip Film nip performed by a touch roll was performed while the film was being conveyed (during conveyance), and was performed while conveyance of the film was stopped (during stop).
(4) Generation of wrinkles The film is conveyed in a state where the film is nipped by the touch roll, and it is visually confirmed whether or not wrinkles are generated on the film on the corona discharge treatment roll. Those that did not occur were marked with (O), and those that wrinkled on the film on the corona discharge treatment roll were marked with (x).
(5) Uniformity of surface modification Uniformity of surface modification in the width direction of the film subjected to corona discharge treatment, in accordance with JIS K6768, a wet tension test mixed solution [manufactured by Wako Pure Chemical Industries, Ltd., surface tension : 50 mN / m]. A film having the same wettability in the entire width direction of the film was indicated by (◯), and a film having a variation in wettability in the film width direction was indicated by (X).

<Film>
◇ Film (A): Cycloolefin resin film (50 μm) / polypropylene film (a) (30 μm) laminated film [total thickness: 80 μm, substrate width: 1450 mm]
◇ Film (B): Laminated film of cycloolefin resin film (100 μm) / polypropylene film (a) (30 μm) [total thickness: 130 μm, substrate width: 1450 mm]
◇ Film (C): Cycloolefin resin film (100 μm) / polypropylene film (a) (30 μm) laminated film [total thickness: 130 μm, substrate width: 1400 mm]
◇ Film (D): Laminated film of cycloolefin resin film (100 μm) / polypropylene film (b) (30 μm) [total thickness: 130 μm, substrate width: 1400 mm]

[Example 1]
A corona discharge treatment apparatus having a corona discharge treatment roll having a diameter of 500 mm and a touch roll having a nip pressure of 8 kg / cm and a diameter of 150 mm as shown in FIG. The film (A) was subjected to corona discharge treatment at 172 N / m. In addition, the film nip by a touch roll nipped the film with the touch roll during conveyance of a film, and performed the corona discharge process to the film.
[Example 2]
The film (A) was subjected to corona discharge treatment by the same method as in Example 1 except that the film (B) was used and the film transport tension was changed to 207 N / m.
[Example 3]
The film (C) was subjected to corona discharge treatment by the same method as in Example 1 except that the film (C) was used and the film transport tension was changed to 214 N / m. In addition, the film nip by a touch roll nipped the film with the touch roll while the conveyance of the film was stopped, and subjected the corona discharge treatment to the film.
[Example 4]
The film (C) was subjected to corona discharge treatment in the same manner as in Example 3 except that the film (C) was used and the film transport tension was changed to 286 N / m.
[Example 5]
The film (D) was subjected to corona discharge treatment by the same method as in Example 3 except that the film (D) was used and the film transport tension was changed to 286 N / m.

  Table 1 shows the results of evaluation of film thickness, base material width, conveyance tension setting value, conveyance tension fluctuation value, touch roll nip, wrinkle generation and surface modification uniformity in each example. . In Examples 1 to 5 in which the transport tension of the film satisfies the formula [1] and the fluctuation value of the transport tension of the film also satisfies the formula [2], the fluctuation value of the transport tension is 14 N / m at the maximum. There were no wrinkles. As can be seen from these results, the present invention is suitable for improving the adhesion between the film and the corona discharge treatment roll, and suppressing fluctuations in the film transport tension, thereby causing wrinkles on the film on the treatment roll. It can be prevented. In addition, it was confirmed that the film subjected to the corona discharge treatment by applying the film transport method of the present invention was subjected to uniform surface modification throughout the entire width direction.

[Comparative Example 1]
Using a corona discharge treatment apparatus having a corona discharge treatment roll having a diameter of 500 mm and a touch roll having a nip pressure of 8 kg / cm and a diameter of 150 mm as shown in FIG. The film (A) was subjected to corona discharge treatment at a tension of 152 N / m. In addition, the film nip by a touch roll nipped the film with the touch roll during conveyance of a film, and performed the corona discharge process to the film.
[Comparative Example 2]
The film (C) was subjected to corona discharge treatment by the same method as in Comparative Example 1 except that the film (C) was used and the film transport tension was changed to 271 N / m.
[Comparative Example 3]
The film (C) was subjected to corona discharge treatment by the same method as in Comparative Example 1 except that the film (C) was used and the film transport tension was changed to 286 N / m.
[Comparative Example 4]
The film (C) was subjected to corona discharge treatment by the same method as in Comparative Example 1 except that the film (C) was used and the film transport tension was changed to 157 N / m. In addition, the film nip by a touch roll nipped the film with the touch roll while the conveyance of the film was stopped, and subjected the corona discharge treatment to the film.

  The results of the evaluation of the film thickness, base material width, transport tension setting value, transport tension fluctuation value, touch roll nip, wrinkle generation and surface modification uniformity of each comparative example were the same as in the examples. Table 1 shows. In Comparative Examples 1 to 3 in which the film is nipped by the touch roll during the conveyance of the film, the fluctuation of the conveyance tension when the touch roll nipped is 50 N / m or more. Wrinkles occurred on the film. Further, in Comparative Example 4 in which the film nip by the touch roll was performed while the film conveyance was stopped, the fluctuation in the conveyance tension when the touch roll nipped was 8 N / m, and the fluctuation in the conveyance tension was suppressed. However, since the conveyance tension of the film was 157 N / m and did not satisfy the formula [1], wrinkles occurred on the film on the processing roll. In Comparative Examples 1 to 3 in which wrinkles were generated on the film, the back of the corona discharge treatment occurred, and the surface modification was uneven.

  As described above, according to the present invention, the film and the processing roll are brought into close contact with each other under an appropriate film transport tension, and the fluctuation of the film transport tension when the touch roll nips is suppressed, thereby treating the corona discharge. Wrinkles can be prevented from occurring on the film on the roll. In the above embodiment, the case where the film transport method of the present invention is applied to a corona discharge treatment apparatus has been described. However, the film may be stretched by a tension roll and nipped by a touch roll and a tension roll. For example, the film transport method of the present invention can be applied.

1: Film 2: Corona discharge treatment roll (stretch roll)
3: Touch roll 4: High-voltage power supply 5: Corona discharge electrode 6: Electrode portion 7: Guide roll α: Angle of obstruction

Claims (4)

A film conveying method for conveying the film by niping the vicinity of the contact start position of the film with the tension roll while touching the film with the tension roll while stretching the film with a tension roll,
The transport tension of the film satisfies the following formula [1], and the variation value of the transport tension, which is the difference between the maximum value of the transport tension after the film is nipped by the touch roll and the set value of the transport tension, is as follows. A film transport method, wherein the film is transported so as to satisfy Formula [2].
170 ≦ X ≦ 400 [1]
Y <50 [2]
[In Formula [1], X represents the conveyance tension (N / m) of the film. ]
[In Formula [2], Y represents the fluctuation value (N / m) of the transport tension, which is the difference between the maximum value of the transport tension after the film is nipped by the touch roll and the set value of the transport tension. ]   The film transport method according to claim 1, wherein the touch roll nips while transport of the film is stopped.   3. The film conveying method according to claim 1, wherein the stretching roll is a corona discharge treatment roll. A method for producing an optical film, comprising the film transport method according to claim 1.

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