Method for producing optical film

Abstract

To provide a method for producing an optical film which reduces the amount of water consumption in a cleaning step.SOLUTION: A method for producing an optical film including a plastic film includes a cleaning step (B) of cleaning the long plastic film, where the cleaning step (B) includes a step (B1) of attaching water to the surface of a part in a width direction of the plastic film to be conveyed, a step (B2) of expanding the water attached to the surface of the part of the plastic film to the outside in the width direction of the plastic film, and a step (B3) of removing the water on the surface of the plastic film, in this order, and the expansion of the water in the step (B2) includes a step (B21) of rotating a roll arranged so as to face the surface of the plastic film or a step (B22) of spraying gas to the water attached to the surface of the part of the plastic film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing an optical film. [Background technology]

[0002] Optical films used in the optical field are sometimes subjected to a water washing process during their manufacturing process to remove contaminants such as dust, fibers, film fragments, etc. For example, Patent Document 1 describes that a plastic film, which is the material for optical films, is washed in multiple stages with pure water to remove such contaminants. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-105662 Summary of the Invention [Problem to be solved by the invention]

[0004] Optical films are required to have fewer defects such as optical defects and physical defects than general films, and therefore, in order to remove the above-mentioned dust and water-soluble dirt, it is preferable to provide a water washing step in the manufacturing process of the optical film. On the other hand, from the viewpoint of resource conservation and cost reduction, it is required to reduce the amount of water used in the washing process. Therefore, there is a need for a method for producing an optical film that reduces the amount of water used in the cleaning process. [Means for solving the problem]

[0005] As a result of intensive research to solve the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by making the cleaning process for the plastic film contained in the optical film a process including specific steps, and have completed the present invention. That is, the present invention provides the following.

[0006] <1> A method for producing an optical film, comprising: the optical film comprises a plastic film; The manufacturing method includes a cleaning step (B) of cleaning the long plastic film, The washing step (B) A step (B1) of applying water to the surface of a portion of the plastic film in the width direction as it is conveyed; A step (B2) of spreading the water attached to the surface of the portion of the plastic film outward in the width direction of the plastic film; and Step (B3) of removing water on the surface of the plastic film; in this order, A method for manufacturing an optical film, wherein spreading the water in step (B2) includes step (B21) of rotating a roll arranged opposite the surface of the plastic film, or step (B22) of blowing gas onto the water adhered to the surface of the portion of the plastic film. <2> The width W of the portion to which the water is applied C The width W of the plastic film T Ratio to (W C / W T ) is between 0.10 and 0.50, <1> 10. A method for producing the optical film according to claim 9. <3> the washing step (B) comprises the step (B21) and a step (B23) of blocking water spreading outward in the width direction of the plastic film, and the blocking of water in the step (B23) is carried out by rotating auxiliary rolls arranged at both ends of the roll in the direction of the rotation axis in a state of contact with the surface of the plastic film. <1> or <2> 10. A method for producing the optical film according to claim 9. <4> The removal of water in step (B3) includes blowing gas onto the surface of the plastic film. <1> ~ <3> 10. The method for producing the optical film according to any one of claims 1 to 9. <5> The removal of water in the step (B3) includes contacting the peripheral surface of a suction roll with the surface of the plastic film, The suction roll has a peripheral surface with a plurality of pores, and water adhering to the surface of the plastic film is sucked through the plurality of pores. <1> ~ <4> 10. The method for producing the optical film according to any one of claims 1 to 9. <6> The removal of water in the step (B3) comprises blowing gas onto the surface of the plastic film and then heating the plastic film. <1> ~ <5> 10. The method for producing the optical film according to any one of claims 1 to 9. <7> The removal of water in the step (B3) includes contacting the peripheral surface of a suction roll with the surface of the plastic film, and then heating the plastic film; The suction roll has a peripheral surface with a plurality of pores, and water adhering to the surface of the plastic film is sucked through the plurality of pores. <1> ~ <6> 10. The method for producing the optical film according to any one of claims 1 to 9. <8> The method includes a step (A) of surface treating the plastic film before the cleaning step (B), <1> ~ <7> 10. The method for producing the optical film according to any one of claims 1 to 9. <9> After the cleaning step (B), a step (C) of applying a liquid composition onto the surface of the plastic film is included. <1> ~ <8> 10. The method for producing the optical film according to any one of claims 1 to 9. <10> After the washing step (B), a step (D) of stretching the plastic film is included. <1> ~ <9> 10. The method for producing the optical film according to any one of claims 1 to 9. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a method for producing an optical film in which the amount of water used in the washing step is reduced. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an example of a manufacturing apparatus that can be used to carry out the method for manufacturing an optical film according to the first embodiment. [Figure 2] FIG. 2 is a schematic view showing an example of the cleaning device according to the first embodiment. [Figure 3] FIG. 3 is a partial view schematically showing a part of the cleaning device according to the first embodiment. [Figure 4] FIG. 4 is a schematic diagram illustrating an example of the blower according to the first embodiment. [Figure 5] FIG. 5 is a schematic diagram showing an example of a manufacturing apparatus capable of carrying out the method for manufacturing an optical film according to the second embodiment. [Figure 6] FIG. 6 is a cross-sectional view schematically illustrating an example of a suction roller according to the second embodiment. [Figure 7] FIG. 7 is another cross-sectional view schematically illustrating an example of the suction roller according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be modified and implemented as desired without departing from the scope of the claims of the present invention and their equivalents. The components of the embodiments shown below can be combined as appropriate. In addition, in the drawings, the same components are designated by the same reference numerals, and their description may be omitted.

[0010] In the following description, a "long" film refers to a film having a length that is 5 times or more its width, preferably 10 times or more its width, and specifically refers to a film having a length that can be wound into a roll for storage or transportation. There is no particular upper limit to the length of the film, and it can be, for example, 100,000 times or less its width.

[0011] In the following description, unless otherwise specified, the term "plate" is not limited to a rigid member, but also includes a flexible member such as a resin film.

[0012] In the following description, the term "(meth)acrylic acid" includes "acrylic acid," "methacrylic acid," and combinations thereof, and the term "(meth)acrylate" includes "acrylate," "methacrylate," and combinations thereof.

[0013] In the following description, unless otherwise specified, the directions of elements as "horizontal," "parallel," "vertical," and "orthogonal" may include an error within a range that does not impair the effects of the present invention, for example, within a range of ±3°, ±2°, or ±1°.

[0014] In the following description, unless otherwise specified, the term "adhesive" refers not only to adhesives in the narrow sense (adhesives having a shear storage modulus of 1 MPa to 500 MPa at 23°C after irradiation with energy rays or after heat treatment), but also to pressure-sensitive adhesives having a shear storage modulus of less than 1 MPa at 23°C. Therefore, the term "adhesive layer" encompasses not only a layer of an adhesive in the narrow sense, but also a layer of a pressure-sensitive adhesive.

[0015] <1. Overview of optical film manufacturing methods> A manufacturing method according to one embodiment of the present invention includes the steps of: A method for producing an optical film, comprising: the optical film comprises a plastic film; The manufacturing method includes a cleaning step (B) of cleaning the long plastic film, The washing step (B) A step (B1) of applying water to the surface of a portion of the plastic film in the width direction as it is conveyed; A step (B2) of spreading the water attached to the surface of the portion of the plastic film outward in the width direction of the plastic film; and Step (B3) of removing water on the surface of the plastic film; in this order, The spreading of water in step (B2) includes step (B21) of rotating a roll placed opposite the surface of the plastic film, or step (B22) of blowing gas onto the water adhered to the surface of the portion of the plastic film.

[0016] The method for producing an optical film according to this embodiment can reduce the amount of washing water used in the production process, thereby enabling the scale of utility facilities for supplying and discharging washing water to be reduced, thereby lowering production costs.

[0017] <2. First embodiment of manufacturing method> The method for producing an optical film according to embodiment 1 will be described below. The method for producing an optical film according to embodiment 1 includes a cleaning step (B), which includes steps (B1), (B2), and (B3) in this order. Step (B2) includes step (B21). Removal of water in step (B3) includes blowing gas onto the surface of the plastic film. The method for producing an optical film may include any other steps in addition to the above steps. Fig. 1 is a schematic diagram showing an example of a manufacturing apparatus capable of carrying out the method for manufacturing an optical film according to embodiment 1. As shown in Fig. 1, the manufacturing apparatus 1000 includes a surface treatment device 110 that performs surface treatment on a plastic film 1, a cleaning device 120 that causes water to adhere to the surface-treated plastic film 1, a blower 130 as a water removal device, a floating oven 140 as a water removal device, a coating device 150, and a stretching device 160. Fig. 2 is a schematic diagram showing an example of the cleaning device according to embodiment 1. Fig. 3 is a partial view that schematically shows a portion of the cleaning device according to embodiment 1.

[0018] <2.1. Cleaning process (B)> The washing step (B) is a step of washing a long plastic film. By performing the cleaning step (B), highly water-compatible dirt adhering to the surface of the plastic film can be reduced, and the quality of the optical film obtained through the step performed after the cleaning step (B) (e.g., step (C) of applying a liquid composition) can be improved.

[0019] <Process (B1)> The step (B1) included in the washing step (B) is a step of applying water to the surface of a portion of the plastic film in the width direction as it is transported. Here, the width direction of the plastic film is the direction perpendicular to the longitudinal direction and thickness direction of the long plastic film. Usually, the longitudinal direction of the plastic film coincides with the direction in which the plastic film is transported. The surface of a portion in the width direction of a plastic film refers to a surface region of a portion having a width smaller than the width of the plastic film. The portion may be a single portion that is continuous in the width direction, or multiple portions (e.g., two or three portions) that are discontinuous in the width direction. The surface of the portion is preferably a surface of a single portion that is continuous in the width direction, and more preferably a surface region of the central portion including the center in the width direction of the plastic film. The surface of the width direction portion of the plastic film to which water is applied may be only one of the two main surfaces of the plastic film, or may be both main surfaces. When the manufacturing method for an optical film includes a surface treatment step (A) as described below, contamination may occur on the surface of the surface-treated plastic film, so it is preferable to apply water to the surface of the surface-treated plastic film. Furthermore, when the manufacturing method for an optical film includes a coating step (C) as described below, it is preferable to apply water to the surface of the plastic film to which the liquid composition is applied, so that the adhesion of the coating layer can be improved.

[0020] In step (B1), the width W of the portion to which water is applied is C The width W of the plastic film T Ratio to (WC / W T ) is usually smaller than 1. Here, when the portion to which water is applied is composed of multiple portions, the width Wc is the sum of the width dimensions of each of the multiple portions to which water is applied. C / W T ) is smaller than 1, the amount of water to be applied to the plastic film for washing can be reduced. The amount of water for washing can be further reduced, so the ratio (W C / W T ) is more preferably 0.90 or less, even more preferably 0.70 or less, and even more preferably 0.5 or less, and is usually greater than 0, preferably 0.10 or more, in order to widen the area of ​​the plastic film to be washed. Furthermore, in the production of a long optical film, portions with inferior optical properties usually occur at both ends in the width direction, and therefore, these ends are often trimmed and removed to form the final product. Since the portions that are finally removed are less likely to be washed with water, it is preferable to provide regions to which water does not adhere on both outer sides in the width direction of the portions to which water is adhered.

[0021] The water used in step (B1) and applied to the surface of the plastic film is preferably water that has been treated to reduce impurities in order to thoroughly clean the plastic film, and pure water is more preferred. Examples of treatments for reducing impurities include filtration using a filter such as a reverse osmosis membrane (RO membrane), adsorption using activated carbon, ion exchange using an ion exchange membrane, and sterilization using ultraviolet light. For example, water that has been treated in the following order may be used: removal of coarse foreign matter using a filter, activated carbon filtration, RO membrane permeation, ion exchange membrane permeation, and ultraviolet light irradiation.

[0022] The wastewater from the cleaning process (B) may be recycled and used as the water to be attached to the surface of the plastic film. Recycling the wastewater can reduce wastewater in the optical film manufacturing process. When recycling the wastewater, it is preferable to perform a treatment to reduce impurities in the wastewater. Alternatively, only a portion of the wastewater may be returned to the cleaning process (B), and the other portion may be discarded without being returned to the cleaning process (B). By returning only a portion of the wastewater to the cleaning process (B), the impurities in the recycled water can be reduced compared to when all of the wastewater is returned to the cleaning process (B).

[0023] The temperature of the water to be applied is not particularly limited and may be any temperature depending on the heat resistance of the plastic film to be cleaned, for example, 80°C or less, for example, 60°C or less, for example, 40°C or less, and is preferably 10°C or more, more preferably 15°C or more, and even more preferably 20°C or more, as this improves the cleaning ability.

[0024] The method for depositing water on the surface of a portion of the plastic film in the width direction is not particularly limited and may be any method, for example, a method of spraying water from a spray nozzle toward the surface of the plastic film. The shape of the trajectory of the water sprayed from the spray nozzle is not particularly limited and examples include a fan shape with its apex at the tip of the spray nozzle and a cone shape with its apex at the tip of the spray nozzle, with the fan shape with its apex at the tip of the spray nozzle being preferred because it allows for a reduction in the amount of water used.

[0025] An example of step (B1) will be described using Figure 2. Figure 2 shows an example in which the portion in the width direction of the plastic film to which water is to be attached is one portion, which is the central portion. As shown in Figure 2, the cleaning device 120 is equipped with a spray nozzle 121. The spray nozzle 121 sprays water toward the surface 1U of the plastic film 1. The nozzle shape of the spray nozzle 121 and the position of the spray nozzle 121 relative to the plastic film 1 are adjusted so that the sprayed water adheres to the surface of the portion 1c of the plastic film 1. In this example, the spray nozzle 121 is configured so that the trajectory W1 of the water sprayed from the spray nozzle 121 is fan-shaped. The width W of the portion 1c in the width direction of the plastic film 1 is C In this example, the width W of plastic film 1 T narrower than the above ratio (W C / W T ) is smaller than 1 and equal to or smaller than 0.5. The spray nozzle 121 is configured so as not to apply water to the outer regions 1a, 1a on both outer sides in the width direction of the portion 1c. In this example, a plurality of spray nozzles 121 are provided, but the number of spray nozzles 121 to be provided is not particularly limited, and may be increased or decreased depending on the width of the plastic film 1, for example.

[0026] <Process (B2)> The step (B2) included in the washing step (B) is a step of spreading the water attached to the surface of the part of the plastic film outward in the width direction of the plastic film. By using the step (B2), a wide area of ​​the plastic film can be washed with a small amount of water.

[0027] <Process (B21)> In one embodiment, spreading water in step (B2) includes step (B21) of rotating a roll disposed opposite the surface of the plastic film. The roll is disposed so that its peripheral surface faces the surface of the plastic film. The roll is disposed so that the distance between the peripheral surface of the roll and the surface of the plastic film facing it is close enough to allow contact with the water applied to the surface of the plastic film in step (B1). The roll is disposed so that a gap is formed between the peripheral surface of the roll and the surface of the plastic film that allows water to enter.

[0028] When the roll arranged in this manner is rotated, the water adhered to the surface of the widthwise portion of the plastic film in step (B2) comes into contact with the roll, and as the roll rotates, it enters the gap between the circumferential surface of the roll and the surface of the plastic film and is spread outward in the widthwise direction of the plastic film. Therefore, on the plastic film downstream in the conveying direction from the position of the roll, water can be spread from the surface of the water-adhered portion to part or all of the outer region located outward in the widthwise direction of the plastic film.

[0029] The arrangement of the rolls may be determined depending on the transport direction of the plastic film. For example, when the transport direction of the plastic film is horizontal, the rotation axis of the roll may be horizontal. In addition, the rolls are placed on the surface (main surface) side of the plastic film to which water was applied in step (B2). For example, when the transport direction of the plastic film is not perpendicular to the horizontal direction, i.e., horizontal or oblique to the horizontal direction, and water is applied to the surface of the plastic film on the opposite side of the direction of gravity, the rolls are placed on the surface of the plastic film on the opposite side of the direction of gravity. When water is applied to both of the two main surfaces of the plastic film in step (B2), one of the two rolls may be placed on one main surface side of the plastic film, and the other of the two rolls may be placed on the other main surface side of the plastic film. When the water used for washing falls from the rolls, a water receiving member may be provided to receive the water falling from the rolls.

[0030] The angle formed between the transport direction of the plastic film and the direction of the rotation axis of the roll is greater than 0°, preferably 45° or more, and usually 90° or less, and may be 90°.

[0031] <Process (B23)> In one embodiment, the cleaning step (B) preferably includes, in addition to step (B21), step (B23) of blocking water spreading outward in the width direction of the plastic film. The blocking of water in step (B23) is preferably performed by rotating auxiliary rolls arranged at both ends of the roll in the direction of the rotation axis while in contact with the surface of the plastic film. By including step (B23) in the cleaning step (B), it is possible to prevent water adhered to one of the two surfaces (main surfaces) of the plastic film from flowing around and adhering to the other surface. In this case, the amount of water used can be reduced, and the water removal step can be performed on only one surface of the plastic film. Furthermore, in an optional step that may be performed after the cleaning step (B), it is possible to prevent unintended water wetting of the device (for example, wetting of the gripping clips in a stretching device).

[0032] An example of step (B21) and step (B23) will be described with reference to Figures 2 and 3. As shown in Figures 2 and 3, the cleaning device 120 includes a roll 122 and auxiliary rolls 123. The auxiliary rolls 123 are disposed at both ends 122E in the direction of the rotation axis 122A of the roll 122, more specifically, adjacent to both ends 122E in the direction of the rotation axis 122A. The rotation axis 123R of the auxiliary rolls 123 is disposed in the same direction as the rotation axis 122R of the roll 122. The roll 122 is disposed so that a gap S122 large enough to allow water to enter is present between the peripheral surface 122U of the roll 122 and the surface 1U of the plastic film 1. On the other hand, there is no gap between the peripheral surfaces of the auxiliary rolls 123 and the surface 1U of the plastic film 1, and the auxiliary rolls 123 are arranged so that their peripheral surfaces contact the surface 1U of the plastic film 1. A roll 122 is fixed to a shaft 124, and by driving the shaft 124 to rotate by a motor (not shown), the roll 122 rotates about a rotation axis 122R. The direction in which the roll 122 rotates may be either a direction in which the plastic film 1 is fed in the conveyance direction or a direction in which the plastic film 1 is returned in the opposite direction to the conveyance direction. On the other hand, the auxiliary rolls 123 are attached to the shaft 124 shared with the roll 122 via, for example, a bearing so that they can freely rotate about the rotation axis 123R. Because the auxiliary rolls 123 are arranged so as to contact the surface 1U of the plastic film 1, they rotate in a direction in which the plastic film 1 is fed in the conveyance direction as the plastic film 1 is conveyed. The support roll 125 is provided so that its peripheral surface faces the peripheral surface of the roll 122 and the peripheral surfaces of the auxiliary rolls 123, 123, and is configured to be able to support the plastic film 1 being transported.

[0033] The water adhered to the surface of the widthwise portion of the plastic film 1 is carried downstream in the conveying direction D1 as the plastic film 1 is conveyed, and passes through the gap S122 between the surface 1U and the circumferential surface of the rotating roll 122. As the water passes through the gap S122, the water is spread outward in the widthwise direction of the plastic film 1 (arrow A1 in Figure 3).

[0034] The water spread outward in the width direction of the plastic film is blocked by auxiliary rolls 123, 123 arranged so as to be in contact with the surface 1U of the plastic film 1.

[0035] The material forming the peripheral surfaces of the roll 122 and the auxiliary rolls 123, 123 is preferably a metal such as stainless steel, in view of chemical stability, mechanical strength, ability to follow the film being transported, and durability to water.

[0036] <Process (B3)> Step (B3) is a step of removing water from the surface of the plastic film. In the first embodiment, the removal of water in step (B3) is performed after the water is attached to the plastic film 1 by the cleaning device 120. In this embodiment, the removal of water in step (B3) includes blowing a gas onto the surface of the plastic film. By blowing the gas onto the surface of the plastic film, water adhering to the surface of the plastic film can be blown off and removed. Examples of gases to be blown onto the surface of the plastic film include inert gases such as nitrogen gas and air, with air being preferred because it can reduce production costs. The wind speed when blowing the gas is preferably as high as possible from the viewpoint of efficiently removing water, and is preferably 50 m / s or more, more preferably 100 m / s or more, at the gas outlet of the gas blowing device, with the upper limit being, for example, 500 m / s or less.

[0037] The direction in which the gas is blown onto the surface of the plastic film may be perpendicular to the surface of the plastic film, or may be an oblique direction that is neither perpendicular nor perpendicular to the surface of the plastic film, and from the viewpoint of efficiently removing water, an oblique direction is preferred.

[0038] FIG. 4 is a schematic diagram showing an example of an air blower according to embodiment 1. The air blower 130 can perform step (B3). The air blower 130, which serves as a water removal device, includes an air nozzle 131. A compressed air device (not shown) is connected to the air nozzle 131, and gas is ejected from a slit 132 provided at the tip of the air nozzle 131. The slit 132 is a rectangular opening, and the air nozzle 131 is positioned so that the longitudinal direction of the slit 132 is parallel to the width direction of the plastic film 1. From the viewpoint of blowing gas at a high air velocity to improve water removal efficiency, the dimension T1 of the slit 132 in the short side direction is preferably narrow, for example, 5 mm or less, for example, 3 mm or less, or for example, 0.1 mm or more. By forming the slit 132 into a rectangular opening, air can be blown from the slit 132 at a speed that is nearly uniform or uniform across the width direction of the plastic film 1. The air nozzle 131 is arranged so that the gas ejected from the slit 132 is directed in the conveying direction D1 of the plastic film 1 and hits the surface 1U of the plastic film 1 from an oblique direction. Specifically, the air nozzle 131 is arranged so that it is tilted at an angle θ1 in the direction opposite to the conveying direction D1 of the plastic film 1, with the longitudinal direction of the slit 132 as its axis, with respect to the direction D2 perpendicular to the surface 1U of the plastic film 1. The angle θ1 may be, for example, 1° or more, for example, 2° or more, for example, 3° or more, or for example, 4° or more, and may be, for example, 20° or less, for example, 15° or less, or for example, 10° or less.

[0039] The air volume of the blower 130 is preferably 1 m 3 / min or more, e.g. 10m 3 / min or less is acceptable.

[0040] In another embodiment, step (B3) may be performed using a blower equipped with multiple air nozzles, with the gas outlets of the multiple air nozzles arranged in a line along the width direction of the plastic film. When the blower is equipped with multiple air nozzles, it is preferable that the total air volume blown from the multiple air nozzles is within the range indicated above as the range of air volume blown by the blower 130. It is also preferable that each of the multiple air nozzles is arranged at an angle θ1 in the direction opposite to the transport direction of the plastic film, with the direction in which the multiple gas outlets are arranged as an axis. The range of angle θ1 may be the same as the range exemplified above for angle θ1.

[0041] Step (B3) may include blowing gas onto the surface of the plastic film and then heating the plastic film. By further heating the plastic film after blowing gas onto the surface of the plastic film, if water remains on the surface of the plastic film and / or if the plastic film contains water, the water can be further removed, thereby reducing the effect of the water in the next step.

[0042] The plastic film may be heated, for example, by passing the plastic film through an oven whose internal atmosphere is heated, by supporting and transporting the plastic film with heated rolls, or by a combination of these. Heating of the plastic film can be carried out, for example, as shown in FIG. 1, by removing water from the plastic film 1 using a blower 130, and then passing the plastic film 1 through a floating oven 140 to heat it. When heating the plastic film, the plastic film may be transported while floating as in the floating oven 140, or the plastic film may be supported by rolls and transported.

[0043] When the plastic film 1 is heated, the temperature can be any temperature depending on the heat resistance of the plastic film 1, for example, 60°C or higher, for example, 80°C or higher, or 120°C or lower, for example, 110°C or lower. When the plastic film is heated by hot air, the air speed may be, for example, 5 m / sec or more, for example, 8 m / sec or more, and may be, for example, 20 m / sec or less, for example, 17 m / sec or less.

[0044] <Plastic film> The long plastic film to be washed in the washing step (B) usually contains a plastic and is made of a plastic, which usually contains a polymer. Examples of polymers contained in the material forming the plastic film are not particularly limited, and include cellulose-based polymers such as triacetyl cellulose, polyesters such as polyethylene terephthalate, cycloolefin-based polymers such as norbornene-based polymers, polycarbonates, and acrylic polymers which are polymers of (meth)acrylic acid or its derivatives.

[0045] Among these, norbornene-based polymers are preferred because of their excellent transparency and moldability. Examples of norbornene-based polymers include ring-opening polymers of monomers having a norbornene structure and hydrogenated products thereof; and addition polymers of monomers having a norbornene structure and hydrogenated products thereof. Examples of ring-opening polymers of monomers having a norbornene structure include ring-opening homopolymers of one type of monomer having a norbornene structure, ring-opening copolymers of two or more types of monomers having a norbornene structure, and ring-opening copolymers of a monomer having a norbornene structure and any monomer copolymerizable therewith. Examples of addition polymers of monomers having a norbornene structure include addition homopolymers of one type of monomer having a norbornene structure, addition copolymers of two or more types of monomers having a norbornene structure, and addition copolymers of a monomer having a norbornene structure and any monomer copolymerizable therewith. Among these, hydrogenated products of ring-opening polymers of monomers having a norbornene structure are particularly suitable from the viewpoints of transparency, moldability, heat resistance, low moisture absorption, dimensional stability, and light weight.

[0046] The monomer having a norbornene structure may have a substituent such as an alkyl group, an alkylene group, or a polar group. These substituents may be the same or different, and a plurality of them may be bonded to the ring. The monomer having a norbornene structure may be used alone or in combination of two or more types in any ratio.

[0047] The proportion of polymer in the plastic contained in the plastic film is, for example, 50% to 100%, for example, 70% to 100%, preferably 80% to 100%, and more preferably 90% to 100%.

[0048] The plastic contained in the plastic film may contain optional components other than the polymer, as long as the effects of the present invention are not significantly impaired. Examples of optional components include additives such as colorants such as pigments and dyes; plasticizers; fluorescent brighteners; dispersants; heat stabilizers; light stabilizers; UV absorbers; antistatic agents; antioxidants; lubricants; and surfactants. These components may be used alone or in combination of two or more in any ratio. The amount of optional components contained in the plastic contained in the plastic film can be set arbitrarily within a range that allows the optical film containing the plastic film to exhibit desired properties.

[0049] The plastic film may be a film having a single layer structure including only one layer, or a film having a multi-layer structure including two or more layers.

[0050] The width of the plastic film is preferably 1000 mm or more, more preferably 1500 mm or more. There is no particular upper limit to the width of the plastic film, and it can be, for example, 4000 mm or less.

[0051] The thickness of the plastic film is preferably 10 μm or more, more preferably 20 μm or more, particularly preferably 30 μm or more, and preferably 200 μm or less, more preferably 150 μm or less, particularly preferably 100 μm or less. By making the thickness of the plastic film equal to or greater than the lower limit of the above range, the film can be stably transported. On the other hand, by making the thickness of the plastic film equal to or less than the upper limit of the above range, the film can be stably transported, and when a stretching step is included in the manufacturing method of the optical film, the film can be stretched uniformly.

[0052] There are no limitations on the method for producing a plastic film. A plastic film can be obtained, for example, by molding a material for forming the plastic film using any film molding method. Examples of film molding methods include cast molding, extrusion molding, and inflation molding. Among these, melt extrusion methods that do not use solvents are preferred because they can efficiently reduce the amount of residual volatile components and are therefore environmentally friendly, work environment friendly, and have excellent production efficiency. Examples of melt extrusion methods include inflation methods that use a die, and among these, methods that use a T-die are preferred because of their excellent productivity and thickness accuracy.

[0053] When the plastic film is a multilayer film, the plastic film can be produced using, for example, a coextrusion molding method such as a coextrusion T-die method, a coextrusion inflation method, or a coextrusion lamination method; or a film lamination molding method such as dry lamination. Among these, the coextrusion molding method is preferred from the viewpoint of production efficiency and from the viewpoint of not leaving volatile components such as solvents remaining in the plastic film. Among coextrusion molding methods, the coextrusion T-die method is particularly preferred.

[0054] The plastic film may be an unstretched film that has not been subjected to a stretching treatment, or may be a stretched film that has been subjected to a stretching treatment.

[0055] <2.2. Optional Step: Step (A)> Before the cleaning step (B), a step (A) of surface treating the plastic film may be included as an optional step. For example, as shown in FIG. 1, the step (A) may be performed by a surface treatment device 110 before water is applied to the plastic film 1 by a cleaning device 120. Examples of surface treatments include hydrophilization treatments and cleaning treatments, and specific examples include corona discharge treatments and energy ray irradiation treatments. Examples of energy ray irradiation treatments include plasma treatments, electron beam irradiation treatments, and ultraviolet ray irradiation treatments. Corona discharge treatments and plasma treatments are preferred, with corona discharge treatment being more preferred, from the standpoint of treatment efficiency. The corona discharge treatment may be performed in an atmosphere of nitrogen gas with an oxygen concentration of 0.1% by volume or less. As the plasma treatment, atmospheric pressure plasma treatment is preferred.

[0056] Surface treatment of a plastic film, such as corona discharge treatment, can impart hydrophilicity to the surface of the plastic film, thereby improving the adhesiveness of the plastic film. Therefore, after step (A), step (C) is performed in which a liquid composition such as an adhesive or primer is applied to the surface of the plastic film, thereby improving the adhesiveness between the plastic film and the liquid composition layer and its cured layer.

[0057] <2.3. Optional Step: Step (C)> After the washing step (B), a step (C) of applying a liquid composition to the surface of the plastic film may be included as an optional step. For example, as shown in Fig. 1, the step (C) may be performed by a coating device 150 after water is applied to the plastic film 1 by a washing device 120 and the water is removed by a blower 130 and a floating oven 140.

[0058] Examples of coating methods include roll coating, gravure coating, wire bar coating, dipping, spraying, die coating, air knife coating, curtain coating, slide coating, and extrusion coating, and among these, roll coating and die coating are preferred.

[0059] The liquid composition to be applied is not particularly limited, and any liquid composition may be applied. Examples of liquid compositions include adhesives and primers, and specific examples include acrylic adhesives, urethane adhesives, polyester adhesives, polyvinyl alcohol adhesives, polyolefin adhesives, modified polyolefin adhesives, polyvinyl alkyl ether adhesives, rubber adhesives, ethylene-vinyl acetate adhesives, vinyl chloride-vinyl acetate adhesives, SEBS (styrene-ethylene-butylene-styrene copolymer) adhesives, SIS (styrene-isoprene-styrene block copolymer) adhesives, ethylene adhesives such as ethylene-styrene copolymers, and acrylic ester adhesives such as ethylene-methyl(meth)acrylate copolymers and ethylene-ethyl(meth)acrylate copolymers. One type of adhesive may be used alone, or two or more types may be used in combination in any ratio.

[0060] The liquid composition is preferably a liquid composition containing polyurethane. A layer of the liquid composition containing polyurethane can function as a primer layer that improves adhesion to other layers. A commercially available water-based urethane resin may be used as the polyurethane. A water-based urethane resin is a composition containing polyurethane and water, and is typically a composition in which polyurethane and optional components as needed are dispersed in water. One type of polyurethane may be used alone, or two or more types may be used in combination at any ratio. In addition to polyurethane, the liquid composition may contain additives such as a solvent, a crosslinking agent, a curing accelerator, a curing aid, a non-volatile base, particles, a wetting agent, etc. One type of these may be used alone, or two or more types may be used in combination at any ratio.

[0061] A layer of the liquid composition can be formed on the surface of the plastic film by step (C). After step (C), an optional step such as a step of drying the layer of the liquid composition or a step of curing the layer of the liquid composition may be performed.

[0062] <2.4. Optional Step: Step (D)> The washing step (B) may be followed by a step (D) of stretching the plastic film. For example, as shown in FIG. 1, the step (D) may be carried out by a stretching device 160 after the liquid composition is applied by a coating device 150. The stretching method in step (D) is not particularly limited and may be any method. Examples of stretching modes include longitudinal stretching (stretching in the longitudinal direction of the film), transverse stretching (stretching in the width direction of the film), oblique stretching (stretching in a direction other than the longitudinal direction or width direction of the film), and combinations of these, performed sequentially or simultaneously. Specific examples of the stretching device 160 include a longitudinal uniaxial stretching machine, a tenter stretching machine, a bubble stretching machine, a roller stretching machine, etc.

[0063] <2.5. Other optional steps> The method for producing an optical film may further include optional steps in addition to the steps described above. Examples of the optional steps include forming an optional layer on the plastic film, laminating an optional layer on the plastic film, and trimming the optical film into a desired shape.

[0064] 3. Modification of the First Embodiment A modified example of embodiment 1 will be described below. In the cleaning step (B) of embodiment 1, step (B22) may be performed instead of step (B21). Step (B22) is a step of blowing gas onto the water attached to the surface of the portion of the plastic film. By blowing gas onto the water attached to the surface of the portion, the attached water can be spread outward in the width direction of the plastic film. The direction of blowing the gas can be adjusted so that the water attached to the surface of the portion spreads outward in the width direction of the plastic film. For example, the direction of blowing the gas may be toward the outside in the width direction of the plastic film.

[0065] The gas blowing in step (B22) is not particularly limited and can be carried out using any device. For example, step (B22) may be carried out using a blower equipped with an air nozzle and an air compressor. In step (B22), gas may be blown so that the water adhered to the surface of the widthwise portion of the plastic film spreads outward in the widthwise direction of the plastic film and is further removed from the plastic film, thereby allowing steps (B22) and (B3) to be performed using the same air blower.

[0066] <4. Second Embodiment of Manufacturing Method> The manufacturing method according to embodiment 2 will be described below. The manufacturing method according to embodiment 2 includes a cleaning step (B), which includes steps (B1), (B2), and (B3) in this order. Removing water in step (B3) includes contacting the peripheral surface of a suction roll with the surface of the plastic film. The manufacturing method for an optical film may include any other steps in addition to the above steps. The manufacturing method according to embodiment 2 is similar to the manufacturing method according to embodiment 1, except for the manner of water removal in step (B3). In embodiment 2, the removal of water in step (B3) is also performed after the water adheres to the plastic film 1 by the cleaning device 120. In embodiment 2, the removal of water in step (B3) includes contacting the circumferential surface of a suction roll with the surface of the plastic film, and then heating the plastic film. The circumferential surface of the suction roll has a plurality of pores, and water adhering to the surface of the plastic film is sucked through the pores.

[0067] FIG. 5 is a schematic diagram showing an example of a manufacturing apparatus capable of carrying out the optical film manufacturing method according to embodiment 2. As shown in FIG. 5, the manufacturing apparatus 2000 includes a surface treatment apparatus 110 that performs surface treatment on the plastic film 1, a cleaning apparatus 120 that applies water to the surface-treated plastic film 1, a suction roll 230 as a water removal apparatus, a floating oven 140 as a water removal apparatus, a coating apparatus 150, and a stretching apparatus 160. FIG. 6 is a cross-sectional view schematically showing an example of the suction roll according to embodiment 2. FIG. 7 is another cross-sectional view schematically showing an example of the suction roll according to embodiment 2. FIG. 6 shows a cross-section of a cylindrical suction roll taken along a plane including the axis. FIG. 7 shows a cross-section of a cylindrical suction roll taken along a plane perpendicular to the axis. FIG. 7 also shows the plastic film 1 being conveyed.

[0068] Step (B3) in embodiment 2 will be described with reference to Figures 6 and 7. As shown in Figures 6 and 7, suction roll 230 includes a hollow cylindrical shaft 231, a nonwoven fabric layer 232 arranged on the circumferential surface of shaft 231, and a connection portion 233 provided at one longitudinal end of shaft 231 to which a suction device is connected. Shaft 231 includes a cylindrical portion 2311, and a plurality of openings 2312 are provided on the circumferential surface of cylindrical portion 2311 so that the inside of shaft 231 communicates with the outside of shaft 231. Because nonwoven fabric layer 232 is made of nonwoven fabric, the outer peripheral surface of nonwoven fabric layer 232 has a plurality of pores. The outer peripheral surface of nonwoven fabric layer 232 constitutes circumferential surface 2301 of suction roll 230. Therefore, circumferential surface 2301 of suction roll 230 has a plurality of pores. Nonwoven fabric layer 232 is disposed on the circumferential surface of cylindrical portion 2311, which has a plurality of openings 2312. When a suction device is connected to connecting portion 233 to reduce the pressure inside shaft 231, air is sucked from the outer peripheral surface of nonwoven fabric layer 232, i.e., circumferential surface 2301 of suction roll 230, into the inside of shaft 231 through the plurality of openings 2312, which are provided so that the inside and outside of shaft 231 communicate with each other. If water droplets are present on the circumferential surface 2301 of the suction roll 230, the water droplets are sucked from the circumferential surface 2301 into the inside of the shaft 231 and removed from the circumferential surface 2301. By bringing the circumferential surface 2301 of the suction roll 230 into contact with the surface of the plastic film to which water is attached, at least a portion of the water on the surface of the plastic film can be sucked up and removed.

[0069] In the manufacturing apparatus 2000, the suction roll 230 may be configured to be freely rotatable or to be configured to be rotationally driven. Preferably, the suction roll 230 is configured to be rotationally driven. In the second embodiment, the suction roll 230 is preferably rotated at the same speed as the conveying speed of the plastic film 1. By rotating the suction roll 230 at the same speed as the conveying speed of the plastic film 1, scratches on the surface of the plastic film 1 caused by the suction roll 230 can be reduced.

[0070] In the second embodiment, the water is removed using a suction roll, so the water removal capacity can be easily adjusted compared to the first embodiment, in which the water is removed by blowing gas. For example, the water removal capacity of the suction roll can be improved by increasing the rotation speed of the suction roll in accordance with an increase in the transport speed of the plastic film.

[0071] The wrap angle of the plastic film 1 with respect to the suction roll 230 is preferably greater than 0°, and more preferably equal to or greater than 90°. By making the wrap angle preferably greater than 0°, and more preferably equal to or greater than 90°, the surface of the plastic film 1 to which water has adhered comes into good contact with the peripheral surface of the suction roll 230, thereby improving the effectiveness of the suction removal of water by the suction roll 230.

[0072] The wrap angle of the suction roll is the angle formed by a line connecting the start point where the plastic film begins to contact the suction roll to the axial center of the suction roll and a line connecting the end point where the plastic film separates from the suction roll to the axial center of the suction roll in the plastic film transport path along the peripheral surface of the suction roll when the transported plastic film and the suction roll are viewed from the axial direction of the suction roll. In the cross-sectional view of the suction roll shown in Figure 7, the arc between the start point P1 and the end point P2 is the transport path of the plastic film 1 along the peripheral surface of the suction roll 230, and the wrap angle is the angle θ2 formed by the line L1 connecting the start point P1 to the axial center 231c and the line L2 connecting the end point P2 to the axial center 231c.

[0073] A nip roll may be provided to press the surface of the plastic film 1 against the circumferential surface of the suction roll 230, and it is preferable to provide the nip roll, particularly when the embrace angle θ2 of the plastic film 1 with respect to the suction roll 230 is set to 0°. By providing the nip roll, the surface of the plastic film 1 with water adhering thereto comes into good contact with the circumferential surface of the suction roll 230, thereby enhancing the effectiveness of the suction removal of water by the suction roll 230. The direction of the rotation axis of the suction roll 230 and the axis of the nip roll may be parallel to each other.

[0074] The second embodiment may be modified in the same manner as the first embodiment. That is, in the cleaning step (B) of the second embodiment, step (B22) may be performed instead of step (B21).

[0075] <5. Optical Film> The optical film that can be produced by the production method of the present invention includes the above-mentioned plastic film that has been subjected to the cleaning step (B) and other optional steps. The optical film may include only the plastic film, or may include, in addition to the plastic film, a functional layer such as an adhesive layer, a primer layer, a polarizer layer, or another plastic layer. [Example]

[0076] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below, and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents.

[0077] In the following description, the units "%" and "parts" that represent amounts are by weight unless otherwise specified. Furthermore, the operations described below were carried out at room temperature (20°C ± 15°C) and atmospheric pressure (1 atm) unless otherwise specified.

[0078] Example 1 (1-1. Plastic film manufacturing) Pellets of a cycloolefin resin containing a norbornene polymer ("ZEONOR" manufactured by Zeon Corporation; glass transition temperature 126°C) were dried at 100°C for 5 hours. The pellets were fed into an extruder, melted in the extruder, passed through a polymer pipe and a polymer filter, and extruded into a sheet form from a T-die onto a casting drum. The extruded sheet was cooled to obtain a long plastic film 1 having a thickness of 80 μm and a width of 2000 mm. The obtained plastic film 1 was loaded into the manufacturing apparatus 1000. The following steps were carried out while the plastic film 1 was conveyed in the longitudinal direction by the manufacturing apparatus 1000 at a speed of 30 m / min.

[0079] (1-2. Surface treatment process (A)) The plastic film 1 was transported in the longitudinal direction and then conveyed to a corona discharge treatment device (manufactured by Kasuga Electric Co., Ltd.) serving as a surface treatment device 110. In the surface treatment device 110, one surface of the plastic film 1 was subjected to a corona discharge treatment as a surface treatment under conditions of an output of 450 W, an electrode length of 2200 mm, and a transport speed of 30 m / min.

[0080] (1-3. Cleaning process (B): Process (B1)) Thereafter, the surface-treated plastic film 1 was transported to the cleaning device 120 and subjected to the step (B1). A spray nozzle manufactured by Ikeuchi was used as the spray nozzle 121, and water was applied to a width direction portion (specifically, the center portion) of the plastic film 1. The width W of the portion (center portion) to which water was applied was C The width W of the plastic film 1 T Ratio to (W C / W T ) was set to 0.5. That is, the width W of the central part where water is applied C was set to 1000 mm.

[0081] (1-4. Cleaning process (B): process (B21)) Then, step (B2) was performed to spread the water adhered to the central portion of the width direction of the plastic film 1 outward in the width direction of the plastic film 1. For step (B2), a cleaning device was used that was equipped with the roll 122 of the cleaning device 120 but did not have the auxiliary rolls 123, 123. The roll 122 was positioned so that its peripheral surface faced the surface of the plastic film 1 and so that the rotational axis of the roll 122 was perpendicular to the conveying direction of the plastic film. The roll 122 (roll diameter: 50 mm, length: 2200 mm) was rotated in the direction opposite to the direction in which the plastic film 1 was fed in the conveying direction, thereby spreading the water adhered to the central portion of the plastic film 1 outward in the width direction of the plastic film 1, thereby performing step (B21). The cleaning device 120 was adjusted so that the rotation speed of the roll 122 was 10 rpm.

[0082] (1-5. Cleaning process (B): process (B3)) Thereafter, a step (B3) of removing water from the surface of the plastic film 1 was carried out using an air blower 130. An air nozzle manufactured by Daikoken Netsuku Kaisha was used as the air nozzle 131. The air nozzle 131 was positioned so that the distance between the slit 132 and the surface of the plastic film 1 was 5 mm and so that the longitudinal direction of the slit 132 was parallel to the width direction of the plastic film 1, and the air nozzle 131 was tilted so that the angle θ1 was 5°, and air was blown onto the plastic film 1. The air was blown at a wind speed from the air nozzle 131 of 120 m / sec. By the above operation, most of the water attached to the surface of the plastic film 1 was removed.

[0083] Thereafter, the plastic film 1 was heated in a floating oven 140 to remove the moisture that could not be removed by the air blower 130. The floating oven 140 was set to a temperature of 100° C. and an air velocity of 15 m / sec.

[0084] (Confirming cleaning effect) The plastic film 1 subjected to step (B3) was cut into A4 size pieces to obtain sample pieces. The surface of the sample pieces was washed with water, and the washed water was analyzed by ion chromatography using an aqueous solution of sodium bicarbonate and sodium carbonate as the eluent. The analysis confirmed that acid components such as oxalic acid were below the detection limit, confirming the cleaning effect of the cleaning step (B).

[0085] <Example 2> The plastic film 1 obtained in (1-1) was carried into the manufacturing apparatus 2000 described above. In (1-5), a step (B3) of removing water from the surface of the plastic film 1 was performed using a suction roll 230 instead of the air blower 130. A "Masroll (registered trademark)" manufactured by Masroll Systems was used as the suction roll 230. The wrap angle θ2 of the plastic film 1 with respect to the suction roll 230 was set to 90°. Except for the above, the procedure was the same as in Example 1. The cleaning effect of the obtained plastic film 1 was confirmed in the same manner as in Example 1.

[0086] Example 3 In (1-5), heating by the floating oven 140 was not performed after removing water using the air blower 130. Except for the above, the procedure was the same as in Example 1. The cleaning effect of the obtained plastic film 1 was confirmed in the same manner as in Example 1.

[0087] Example 4 After removal of water using the suction roll 230, heating in the floating oven 140 was not performed. Except for the above, the same operation as in Example 2 was carried out. The cleaning effect of the obtained plastic film 1 was confirmed in the same manner as in Example 1.

[0088] <Example 5> Instead of (1-4), the following operation (5-4) was performed. (5-4. Cleaning Step (B): Step (B21) and Step (B23)) A process (B2) was performed to spread the water attached to the central portion of the width direction of the plastic film 1 outward in the width direction of the plastic film 1, followed by a process (B23) to block the water spreading outward in the width direction of the plastic film 1. A cleaning device 120 equipped with a roll 122 and auxiliary rolls 123, 123 was used for processes (B2) and (B23). The roll 122 had a diameter of 50 mm and a length of 1900 mm, and the auxiliary rolls 123, 123 had a diameter of 52 mm and a length of 100 mm. The roll 122 was positioned so that its peripheral surface faced the surface of the plastic film 1 and so that the rotational axis of the roll 122 was perpendicular to the conveying direction of the plastic film. The auxiliary rolls 123, 123 were positioned so that their peripheral surfaces were in contact with the surface of the plastic film 1. Step (B21) was performed by rotating the roll 122 in the direction opposite to the direction in which the plastic film 1 was fed in the conveying direction, thereby spreading the water adhering to the center of the plastic film 1 outward in the width direction of the plastic film 1. The cleaning device 120 was adjusted so that the rotation speed of the roll 122 was 10 rpm. The auxiliary rolls 123, 123 rotated in the direction in which the plastic film 1 was fed in the conveying direction at a peripheral speed (30 m / sec) that was the same as the conveying speed of the plastic film 1. The auxiliary rolls 123, 123 blocked the water spreading outward in the width direction of the plastic film 1, and step (B23) was carried out. Other than the above, the operation was the same as in Example 1. The cleaning effect of the obtained plastic film 1 was confirmed in the same manner as in Example 1.

[0089] <Comparative Example 1> In (1-3), the step (B1) was not performed, and water was applied to the entire width of the plastic film 1. Therefore, the ratio (W C / W T ) was 1.0. In (1-4), the step (B2) was not performed, that is, a cleaning device not equipped with the roll 122 and the auxiliary rolls 123, 123 was used. Except for the above, the procedure was the same as in Example 1. The cleaning effect of the obtained plastic film 1 was confirmed in the same manner as in Example 1.

[0090] <Comparative Example 2> The plastic film 1 obtained in (1-1) was carried into the manufacturing apparatus 2000 described above. In (1-3), the step (B1) was not performed, and water was applied to the entire width of the plastic film 1. Therefore, the ratio (W C / W T ) was 1.0. In (1-4), the step (B2) was not performed, that is, a cleaning device not equipped with the roll 122 and the auxiliary rolls 123, 123 was used. In (1-5), a step (B3) of removing the surface of the plastic film 1 was performed using a suction roll 230 instead of the air blower 130. A mass roll manufactured by Mass Roll Systems was used as the suction roll 230. The wrap angle θ2 of the plastic film 1 with respect to the suction roll 230 was set to 90°. Except for the above, the procedure was the same as in Example 1. The cleaning effect of the obtained plastic film 1 was confirmed in the same manner as in Example 1.

[0091] <Comparative Example 3> In (1-3), the step (B1) was not performed, and water was applied to the entire width of the plastic film 1. Therefore, the ratio (W C / W T ) was 1.0. In (1-4), the step (B2) was not performed, that is, a cleaning device not equipped with the roll 122 and the auxiliary rolls 123, 123 was used. In (1-5), heating by the floating oven 140 was not performed after removing water using the air blower 130. Except for the above, the procedure was the same as in Example 1. The cleaning effect of the obtained plastic film 1 was confirmed in the same manner as in Example 1.

[0092] <Comparative Example 4> The plastic film 1 obtained in (1-1) was carried into the manufacturing apparatus 2000 described above. In (1-3), the step (B1) was not performed, and water was applied to the entire width of the plastic film 1. Therefore, the ratio (W C / W T ) was 1.0. In (1-5), a step (B3) of removing the surface of the plastic film 1 was performed using a suction roll 230 instead of the air blower 130. A mass roll manufactured by Mass Roll Systems was used as the suction roll 230. The wrap angle θ2 of the plastic film 1 with respect to the suction roll 230 was set to 90°. After removal of water using the suction roll 230, heating in the floating oven 140 was not performed. Except for the above, the procedure was the same as in Example 1. The cleaning effect of the obtained plastic film 1 was confirmed in the same manner as in Example 1.

[0093] <Manufacturing conditions and results> The manufacturing conditions, the amount of water used in the cleaning step (B), and the results of checking the cleaning effect for the examples and comparative examples are shown in the table below. The item "Water adhesion" shows the equipment used in step (B1). The item "Step (B2)" shows the materials used in step (B2) and, if step (B23) was performed, the materials used in step (B23). If step (B2) was not performed, "none" is entered. The items "Water Removal 1" and "Water Removal 2" show the components or devices used in step (B3). After the component shown in item "Water Removal 1," the device shown in item "Water Removal 2" was used. In the item "amount of water used," if the amount of water used was the same as or less than the amount of water used in the cleaning step (B) of Example 1, it was recorded as "small," and if the amount of water used was greater, it was recorded as "large." In the item "cleaning effect," a result of analysis in which the acid component was below the detection limit was recorded as "good." The abbreviations in the table below have the following meanings: Ratio (WC / W T ): Width W of the width direction part (center) of the plastic film to which water is attached C , the width of the plastic film W T Percentage of Water nozzle: spray nozzle Roll + auxiliary roll: Roll 122 and auxiliary rolls 123, 123 Oven: Floating oven

[0094] [Table 1]

[0095] In Examples 1 to 5, which included steps (B1) to (B3) in this order, the amount of water used in the washing step (B) was small. Comparative Examples 1 to 4, which did not include the steps (B1) and (B2) of applying water to the surface of a portion (specifically, the center portion) in the width direction of the plastic film, used a large amount of water in the washing step (B). [Explanation of symbols]

[0096] 1 plastic film 1c part (center part) W1 locus W C Part width (centre width) W T Plastic film width 1U Plastic film surface 1a outer area 1000 manufacturing equipment 110 Surface treatment equipment 120 Cleaning equipment 121 spray nozzle 122 rolls 122A Roll rotation axis direction 122R Roll rotation axis 122E Roll end 122U circumferential surface 123 Auxiliary Roll 123R Auxiliary roll rotation axis 124 axes 125 Support Roll 130 Blower 131 Air nozzle 132 Slit 140 Floating Oven 150 Coating equipment 160 Stretching device 2000 Manufacturing equipment 230 Suction Roll 2301 Peripheral surface 231 Axis 231c axis center 2311 Cylindrical part 2312 Aperture 232 Non-woven layer 233 Connection S122 Gap D1 Conveying direction θ1 angle θ2 angle (enclosed angle) P1 Starting point P2 End point L1 line L2 line A1 Arrow

Claims

1. A method for producing an optical film, comprising: the optical film comprises a plastic film; The manufacturing method includes a cleaning step (B) of cleaning the long plastic film, The washing step (B) a step (B1) of applying water to the surface of a portion of the plastic film in the width direction as it is transported; A step (B2) of spreading the water attached to the surface of the portion of the plastic film outward in the width direction of the plastic film; and a step (B3) of removing water on the surface of the plastic film; in this order, A method for manufacturing an optical film, wherein spreading the water in step (B2) includes step (B21) of rotating a roll arranged opposite the surface of the plastic film, or step (B22) of blowing gas onto the water adhered to the surface of the portion of the plastic film.

2. The width W of the portion to which the water is applied Ｃ The width W of the plastic film Ｔ Ratio to (W Ｃ / W Ｔ 2. The method for producing an optical film according to claim 1, wherein the ratio of the refractive index to the refractive index of the optical film is 0.10 or more and 0.50 or less.

3. 2. The method for producing an optical film according to claim 1, wherein the cleaning process (B) comprises the process (B21) and a process (B23) of blocking water spreading outward in the width direction of the plastic film, and the blocking of water in the process (B23) is carried out by rotating auxiliary rolls arranged at both ends of the roll in the direction of the rotation axis while in contact with the surface of the plastic film.

4. The method for producing an optical film according to claim 1 , wherein the removal of water in the step (B3) comprises blowing a gas onto the surface of the plastic film.

5. The removal of water in the step (B3) includes contacting the peripheral surface of a suction roll with the surface of the plastic film, The method for producing an optical film according to claim 1 , wherein the circumferential surface of the suction roll has a plurality of pores, and water adhering to the surface of the plastic film is sucked through the pores.

6. 2. The method for producing an optical film according to claim 1, wherein the removal of water in the step (B3) comprises blowing a gas onto the surface of the plastic film, and then heating the plastic film.

7. The removal of water in the step (B3) includes contacting the peripheral surface of a suction roll with the surface of the plastic film, and then heating the plastic film; The method for producing an optical film according to claim 1 , wherein the circumferential surface of the suction roll has a plurality of pores, and water adhering to the surface of the plastic film is sucked through the pores.

8. The method for producing an optical film according to claim 1 , further comprising a step (A) of surface treating the plastic film before the cleaning step (B).

9. The method for producing an optical film according to claim 1 , further comprising, after the cleaning step (B), a step (C) of applying a liquid composition onto the surface of the plastic film.

10. The method for producing an optical film according to claim 1 , further comprising, after the cleaning step (B), a step (D) of stretching the plastic film.

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