Manufacturing method for wound stretched film

Abstract

To provide a manufacturing method of wound stretched film with reduced occurrence of gauge band and transverse dun defects with high yield.SOLUTION: A manufacturing method of a wound body of a stretched film comprises: a feeding process for supplying a long pre-stretched film; a first stretching process for stretching the long pre-stretched film to form a long intermediate film; an oscillation process for oscillating the long intermediate film; a first trimming process for trimming both ends of the long intermediate film being oscillated; a second stretching process for stretching the trimmed long intermediate film to form a long stretched film; and the winding process for winding the long stretched film into a roll to obtain a rolled long stretched film.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a wound body of a stretched film.

Background Art

[0002] Films such as optical films are usually manufactured as long films for improving production efficiency. Such long optical films are continuously manufactured by methods such as a melt extrusion molding method and a solution casting method, and further, are subjected to treatments such as stretching as necessary, and then are wound into a roll shape to form a wound body, and are generally stored and transported in the state of this wound body. In the manufacturing process of such a wound body, a method is known in which both end portions in the width direction are trimmed while oscillating the film in the width direction, and then, after performing a stretching step, the stretched film is wound into a roll shape to form a wound body (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a long optical film is manufactured by a method such as a melt extrusion molding method or a solution casting method, continuous thickness unevenness may be formed in the obtained film. For example, a relatively thick portion may be continuously formed in a certain position in the width direction of the film in the longitudinal direction of the film, and a relatively thin portion may be continuously formed in another certain position in the width direction of the film in the longitudinal direction of the film. When a film with such continuous thickness unevenness is used as a wound body, by winding in a state where the thick portions overlap, a thick portion corresponding to the thick portion may generate a thick portion in a belt-like shape called a gauge band. On the other hand, since the winding is crushed at the position corresponding to the thin portion, streaks that appear in a direction substantially parallel to the axial direction of the wound body, called horizontal streaks, may occur on the surface of the wound body. If the wound body is stored with the gauge band and horizontal streaks present, it may cause deformation of the film and reduce the quality as an optical film. Therefore, it is required to reduce such problems.

[0005] On the other hand, when the film is stretched at a high magnification, in order to reduce the occurrence of defects such as film breakage, the stretching may be performed in two steps. For example, the pre-stretched film may be longitudinally uniaxially stretched and then transversely uniaxially stretched. When the stretching is performed in two steps in this way, the film may meander during the first-stage stretching, and both ends of the obtained film may be deformed. Therefore, in the second-stage stretching, problems such as the inability to grip both ends of the film may occur. In order to reduce the occurrence of problems in the second-stage stretching, usually, after the first-stage stretching, a step of trimming both ends of the film is performed. However, in the manufacturing process of the wound body, the higher the number of trimming times, the lower the film yield.

[0006] Therefore, there is a need for a method for manufacturing a wound body of a stretched film that can manufacture a wound body of a stretched film with reduced occurrence of gauge band and horizontal streak defects with good yield.

Means for Solving the Problem

[0007] As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the present invention provides the following.

[0008] <1> A method for manufacturing a wound body of a stretched film, comprising: a supply step of supplying a long unstretched film; a first stretching step of stretching the long unstretched film to form a long intermediate film; an oscillation step of oscillating the long intermediate film; a first trimming step of trimming both ends of the oscillating long intermediate film; a second stretching step of stretching the trimmed long intermediate film to form a long stretched film; a winding step of winding the long stretched film into a roll to obtain a wound body of the long stretched film; and a method for manufacturing a wound body of a stretched film including the above steps. <2> The manufacturing method according to <1>, further including a second trimming step of trimming both ends of the long stretched film after the second stretching step and before the winding step. <3> The manufacturing method according to <1> or <2>, wherein a stretching ratio E2 in the second stretching step is larger than a stretching ratio E1 in the first stretching step. <4> The manufacturing method according to any one of <1> to <3>, further including a step of forming concavo-convex portions at both ends of the long stretched film after the second stretching step and before the winding step. <5> The manufacturing method according to <4>, wherein the concavo-convex portions are formed by irradiating laser light. <6> The manufacturing method according to any one of <1> to <5>, wherein the long unstretched film supplied in the supply step is a film formed by a melt extrusion molding method. <7> After the first trimming step and before the second stretching step, the method further includes a preliminary winding step of winding the trimmed long intermediate film into a roll to obtain a preliminary wound body. The manufacturing method according to any one of <1> to <6>, wherein the trimmed long intermediate film is drawn from the preliminarily wound body obtained in the preliminary winding step and supplied to the second stretching step. <8> The manufacturing method according to any one of <1> to <7>, wherein the oscillating amplitude of the long intermediate film in the first trimming step is 20 mm or more and 200 mm or less. <9> The manufacturing method according to any one of <1> to <8>, wherein the surface roughness Ra of at least one surface of the long stretched film is 5 nm or more and 50 nm or less. <10> The manufacturing method according to any one of <1> to <9>, wherein the long stretched film includes a base material layer containing an alicyclic structure-containing polymer and a resin layer made of a urethane resin containing silica particles, and the resin layer is a layer on at least one surface side of the long stretched film.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a method for manufacturing a wound body of a stretched film, which can produce a wound body of a stretched film with a reduced occurrence of defects in the gauge band and the horizontal dam with good yield.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments and examples of the present invention will be described in detail. However, the present invention is not limited to the embodiments and examples shown below, and can be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and its equivalent scope. The components of the embodiments shown below can be combined as appropriate. In the drawings, the same components may be denoted by the same reference numerals, and the description thereof may be omitted.

[0012] In the following description, the "long" film refers to a film having a length that is 5 times or more the width, preferably 10 times or more the length, and specifically refers to a film having a length such that it can be wound up and stored or transported in a roll shape. The upper limit of the length of the film is not particularly limited, and can be, for example, 100,000 times or less the width.

[0013] In the following description, when the context is clear, the long pre-stretched film, the long intermediate film, and the long stretched film may be simply referred to as the pre-stretched film, the intermediate film, and the stretched film, respectively.

[0014] In the following description, the directions of the elements being "parallel", "perpendicular", and "orthogonal" may include errors within a range that does not impair the effects of the present invention, for example, within a range of ±3°, ±2°, or ±1°, unless otherwise specified.

[0015] In the following description, the direction in which the film is conveyed may be simply referred to as the MD direction. When conveying a long film, the longitudinal direction of the conveyed film usually coincides with the MD direction. Also, in the apparatus, the direction orthogonal to the MD direction and parallel to the conveyed film surface may be referred to as the TD direction. When conveying a long film, the TD direction usually coincides with the width direction of the film.

[0016] In the following description, unless otherwise specified, the slow axis of the film or layer refers to the slow axis in the plane of the film or layer.

[0017] In the following description, unless otherwise specified, the orientation angle of a film or layer refers to the angle formed by the slow axis of the film or layer with respect to the longitudinal direction of the film or layer.

[0018] In the following description, unless otherwise specified, the in-plane retardation Re of a layer is a value represented by Re = (nx - ny) × d. Here, nx represents the refractive index in the direction (in-plane direction) perpendicular to the layer thickness direction and giving the maximum refractive index. ny represents the refractive index in the in-plane direction of the layer and perpendicular to the direction of nx. nz represents the refractive index in the layer thickness direction. d represents the thickness of the layer. Unless otherwise specified, the measurement wavelength is 590 nm.

[0019] <1. Outline of the manufacturing method of the wound body of the stretched film> The manufacturing method of the wound body of the stretched film according to the present invention includes a supply step of supplying a long pre-stretched film, a first stretching step of stretching the long pre-stretched film to form a long intermediate film, an oscillation step of oscillating the long intermediate film, a first trimming step of trimming both ends of the oscillating long intermediate film, a second stretching step of stretching the trimmed long intermediate film to form a long stretched film, and a winding step of winding the long stretched film into a roll to obtain a wound body of the long stretched film. It includes these steps.

[0020] According to the manufacturing method of the wound body of the stretched film according to the present invention, a wound body of the stretched film with reduced occurrence of gauge band and lateral stripe defects can be manufactured with good yield.

[0021] The first stretching process is performed after the normal supply process. The oscillation process is usually performed after the first stretching process. The first trimming process is usually performed simultaneously with the oscillation process. The second stretching process is usually performed after the first trimming process. The winding process is usually performed after the second stretching process. The method for manufacturing a wound body of a stretched film according to the present invention may include an optional process in addition to the supply process, the first stretching process, the oscillation process, the first trimming process, the second stretching process, and the winding process. For example, the method for manufacturing a wound body of a stretched film according to the present invention may further include a preliminary winding process of winding the trimmed long intermediate film into a roll shape to obtain a preliminary wound body after the first trimming process and before the second stretching process, and may include a process of feeding out the trimmed long intermediate film from the preliminary wound body obtained in the preliminary winding process and supplying it to the second stretching process. For example, the method for manufacturing a wound body of a stretched film according to the present invention may further include a second trimming process of trimming both ends of the long stretched film after the second stretching process and before the winding process. For example, the method for manufacturing a wound body of a stretched film according to the present invention may further include a process of forming uneven portions on both ends of the long stretched film after the second stretching process and before the winding process.

[0022] <2. Embodiment of the method for manufacturing a wound body of a stretched film> Hereinafter, a method for manufacturing a wound body of a stretched film according to an embodiment of the present invention will be described. FIG. 1 is a schematic diagram showing an example of a manufacturing apparatus capable of performing the method for manufacturing a wound body according to the present embodiment. The manufacturing apparatus 1000 includes, in order from the upstream of the manufacturing line, a first feeding device 110, a first stretching device 120, an oscillation device 130, a first trimming device 140, a second stretching device 150, a second trimming device 160, laser light irradiation devices 170, 170, and a winding device 180.

[0023] The first stretching device 120 is, for example, a longitudinal uniaxial stretching device, and includes a stretching roll 121 and a stretching roll 122 in order from the upstream of the production line. The oscillation device 130 includes, in order from the upstream of the production line, a conveying roll 133, a steering roll 131, a steering roll 132, and a conveying roll 134. The steering rolls 131 and 132 are cylindrical and configured to be rotatable about an axis. The steering rolls 131 and 132 are each configured to be able to periodically swing around the center point of their axis. The periodic swinging of the steering rolls 131 and 132 can be performed in a plane parallel to the plane of the intermediate film conveyed between the steering roll 131 and the steering roll 132. Since the steering rolls 131 and 132 are configured to be able to periodically swing in this way, the oscillation device 130 can periodically move the intermediate film in the TD direction. The conveying roll 133 guides the intermediate film to the steering roll 131, and the conveying roll 134 is configured to guide the intermediate film from the steering roll 132 to a device downstream of the production line.

[0024] In the method for manufacturing a wound body of a stretched film using the manufacturing apparatus 1000, the first feeding device 110 performs a feeding step of feeding the pre-stretched film 1 in the direction of arrow A1. The stretching roll 121 and the stretching roll 122 included in the first stretching device 120 perform a first stretching step of longitudinally uniaxially stretching the fed pre-stretched film 1 while conveying it by rotating about their axes. The peripheral speed of the stretching roll 122 is rotationally driven to be greater than the peripheral speed of the stretching roll 121, and due to the difference in peripheral speed between the stretching roll 121 and the stretching roll 122, the pre-stretched film 1 is longitudinally uniaxially stretched to produce an intermediate film 2.

[0025] The oscillation device 130 performs an oscillation step of oscillating the intermediate film 2.

[0026] The first trimming device 140 performs a first trimming process of trimming both ends of the intermediate film 2 that is oscillated by the oscillation device 130. The second stretching device 150 is, for example, a horizontal uniaxial stretching device, and manufactures a stretched film 4 by stretching the trimmed intermediate film 3 in the width direction of the intermediate film 3. The second trimming device 160 performs a second trimming process of trimming both ends of the conveyed stretched film 4, and manufactures a trimmed stretched film 5. Next, the laser light irradiation devices 170, 170 form uneven portions at both ends of the trimmed stretched film 5 to manufacture a stretched film 6 having uneven portions formed thereon. Next, the winding device 180 performs a winding process of winding the stretched film 6 having uneven portions formed thereon in a roll shape to manufacture a wound body 7 of the stretched film.

[0027] <2.1. Feeding process> In the feeding process, a long pre-stretched film is fed. In the present embodiment, a wound body of a long pre-stretched film is manufactured in advance, and the first pay-out device 110 pays out the pre-stretched film from the wound body of the pre-stretched film and supplies it to the first stretching device 120. In another embodiment, the feeding process may be performed by supplying a long pre-stretched film continuously manufactured by a method such as a melt extrusion molding method or a solution casting method directly to the next process without winding it once. By performing such a feeding process, the process can be omitted and efficient production can be performed. In addition, it is possible to prevent the generation of a gauge band or the like when preparing a wound body from the pre-stretched film in advance. From the viewpoint of simplifying the manufacturing apparatus, it is preferable to supply the manufactured pre-stretched film directly to the first stretching device 120 without using it as a wound body.

[0028] As the pre-stretched film supplied in the supply process, those continuously formed by methods such as the melt extrusion molding method and the solution casting method can be used. As the pre-stretched film, it is preferable to use one formed by a method including the melt extrusion molding method, and it is particularly preferable to use one formed by the melt extrusion molding method. In the melt extrusion molding method, the film can be efficiently manufactured, but continuous thickness unevenness may be formed in the film. Therefore, by performing the manufacturing method of the present invention using a long pre-stretched film formed by a method including the melt extrusion molding method, the occurrence of defects caused by continuous thickness unevenness can be suppressed, and as a result, a high-quality wound body can be efficiently manufactured.

[0029] Specific examples of the pre-stretched film will be described later.

[0030] <2.2. First stretching step> In the first stretching step, the supplied long pre-stretched film is stretched to form a long intermediate film. By performing the first stretching step in addition to the second stretching step, high-magnification stretching from the pre-stretched film to the stretched film can be achieved while suppressing film breakage.

[0031] Examples of the stretching mode include longitudinal stretching (stretching in the film longitudinal direction), transverse stretching (stretching in the film width direction), diagonal stretching (stretching in a direction that is neither the film longitudinal direction nor the film width direction), and stretching performed sequentially or simultaneously by combining these. Specific examples of the stretching device include a single-axis longitudinal stretching machine, a tenter stretching machine, a bubble stretching machine, a roller stretching machine, etc. In one embodiment, it is preferable to perform uniaxial stretching in the first stretching step, and it is more preferable to perform longitudinal uniaxial stretching. If longitudinal uniaxial stretching is performed in the first stretching step, as described below, the manufacturing process of the pre-stretched film and the longitudinal uniaxial stretching process of the pre-stretched film can be performed as continuous processes, so the manufacturing equipment can be simplified. In general, in the production of a long film by a melt extrusion molding method, a resin film extruded in a film shape from a die is conveyed while being cooled by a rotating cast roll and, if necessary, further by a rotating cooling roll. If longitudinal uniaxial stretching is to be performed in the first stretching step, longitudinal uniaxial stretching can be performed by providing a difference in the peripheral speed of the roll that conveys the film before stretching in the cooling conveyance path of the film before stretching. Therefore, a part of the production apparatus for the film before stretching and a part of the longitudinal uniaxial stretching apparatus can be made common. Accordingly, the production apparatus for the wound body of the stretched film can be simplified.

[0032] The stretching temperature can be, for example, Tg or higher and Tg + 20°C or lower, where Tg is the glass transition temperature of the resin contained in the film before stretching.

[0033] The stretching ratio E1 in the first stretching step is preferably smaller than the stretching ratio in the second stretching step described later. That is, it is preferable that E1 / E2 is less than 1. When E1 / E2 is less than 1, the variation in the orientation angle that may occur in the intermediate film due to the oscillation step after the first stretching step can be effectively relaxed by stretching with the stretching ratio E2 in the second stretching step, which is higher than the stretching ratio E1, and the variation in the orientation angle of the obtained stretched film can be effectively reduced. In this specification, the stretching ratio in uniaxial stretching refers to the ratio of the film dimension after stretching in the stretching direction with the film dimension before stretching taken as 1, and in biaxial stretching, it means the area magnification (area ratio) of the film after stretching with the area of the film before stretching taken as 1.

[0034] E1 / E2 is, for example, 0.9 or less, for example, 0.8 or less, and is usually greater than 0.

[0035] From the viewpoint of achieving high magnification stretching by combining the first stretching step and the second stretching step, the stretching ratio E1 in the first stretching step is relatively high. The stretching ratio E1 is, for example, 1.05 times or more, for example, 1.10 times or more, and is, for example, 2.50 times or less, for example, 2.00 times or less.

[0036] <2.3. Oscillation Process> In the oscillation process, the long intermediate film is oscillated. In the oscillation process, the position of the center in the width direction of the intermediate film before trimming is relatively and periodically moved with respect to the cutting position of the intermediate film in the first trimming process.

[0037] Since the manufacturing method of the present embodiment includes the oscillation process, the thickness unevenness in the width direction that the pre-stretched film and the intermediate film may have can be dispersed. As a result, it is possible to reduce the occurrence of defects in the gauge band and lateral stripe in the wound body to be manufactured.

[0038] When the intermediate film is periodically moved, the oscillation direction can be any direction that periodically moves the intermediate film in the TD direction.

[0039] As the oscillation device capable of performing the oscillation process, a conventionally known device can be used.

[0040] The operation of the oscillation process of the intermediate film can be performed, for example, by periodically moving all or part of the members of the supply device or the conveyance device of the intermediate film at an arbitrary position upstream of the first trimming device 140. In the example shown in FIG. 1, the oscillation process can be performed by periodically moving the steering rolls 131 and 132 provided in the oscillation device 130.

[0041] The amplitude for oscillating the intermediate film in the oscillation process is not particularly limited and can be appropriately adjusted so as to obtain a preferable oscillation amplitude required in the first trimming process. Usually, the amplitude in the first trimming process can be smaller than the amplitude of the intermediate film in the oscillation device.

[0042] Here, the oscillating amplitude of the film "in the trimming process" refers to the amplitude at which the film oscillates at the position where the ears are cut in the film conveyance line. Here, the "ears" of the film refer to the portions at both ends of the long film to be removed in the trimming process. Furthermore, the amplitude is the maximum value of the distance at which the center in the width direction of the continuously passing film periodically moves in the TD direction when observing the center in the width direction of the film continuously passing at the position where the ears are cut in the conveyance line.

[0043] Figure 2 is an explanatory diagram for explaining an example of the oscillation process. In Figure 2, the oscillation device 130 and the first trimming device 140 shown in Figure 1 are enlarged and shown. In actual operation, both ends of the film are trimmed, but for the sake of illustration, only the trimming of the front-end portion is shown in Figure 2.

[0044] In Figure 2, the steering rolls 131 and 132 provided in the oscillation device 130 periodically swing in a plane parallel to the plane of the intermediate film conveyed across the steering roll 131 and the steering roll 132 around the center point of their axes, thereby periodically moving the intermediate film 2 in the TD direction of the intermediate film 2 before trimming and oscillating the intermediate film 2.

[0045] In Figure 2, the first trimming device 140 includes a cutter (not shown) provided at the cutting position indicated by the arrow A41, a support roller 141 that supports the film at the cutting position by the cutter, and a winding roller 142 that winds up and collects the ear 41 cut by the cutter. In the operation of the first trimming using the first trimming device 140, the intermediate film 2 conveyed in the direction of the arrow A2 is cut by the cutter and divided into an intermediate film 3 with both ends in the width direction trimmed and an ear 41. The ear 41 is conveyed in the direction of the arrow A42 and wound up and collected by the winding roller 142.

[0046] FIG. 3 is a top view showing an enlarged view of the oscillation device 130 and the first trimming device 140 shown in FIG. 1. In FIG. 3, for the sake of illustration, the ratio of the amplitude to the width of the film is made larger than the actual aspect, and the amplitude is emphasized and shown.

[0047] The intermediate film 2 is conveyed in the direction indicated by the arrow A2 while oscillating. When the intermediate film 2 reaches the cutting position indicated by the arrow A41, the center in the width direction of the intermediate film 2 is conceptually indicated by the wavy broken line 2C. The amplitude of such a broken line 2C becomes the length indicated by the arrow A21 in FIG. 3, and this becomes the amplitude at which the intermediate film oscillates in the first trimming step. When such an amplitude is, for example, 20 mm, the center in the width direction of the intermediate film 11 moves within a range of ±10 mm from the center of oscillation.

[0048] Also, the period of oscillation is indicated by the period of the wave drawn by the broken line 2C, and the length of the period of oscillation is shown as the length of the intermediate film in which one period of such a wave is drawn. The period of such a broken line 2C becomes the length indicated by the arrow A22 in FIG. 3. The length of the period of oscillation is preferably 50 m or more, more preferably 100 m or more, while preferably 500 m or less, more preferably 300 m or less. By setting the period of oscillation within this range, in the production of a long drawn film for general optical applications, the generation of gauge bands and transverse streaks can be reduced particularly well.

[0049] In another example, a step of winding the intermediate film after the first stretching step into a roll to form a wound body after the first stretching step and before the oscillation step, and a feeding device for feeding the intermediate film from the wound body of the intermediate film can be performed by periodically moving it with respect to the first trimming device.

[0050] In yet another example, the oscillation step may be performed by periodically moving the first trimming device 140. For example, the oscillation step may be performed by periodically moving the first trimming device 140 in the TD direction of the intermediate film 2.

[0051] <2.4. First Trimming Step> In the first trimming step, both ends of the oscillating long intermediate film are trimmed. The end of the film refers to the end in the width direction of the film, and trimming the end means cutting and removing the end in the width direction of the film. Here, the "oscillating intermediate film" means an intermediate film that moves periodically relative to the cutting position by the first trimming device. Therefore, in the first trimming step, the intermediate film 2 that moves periodically in the TD direction may be trimmed with the first trimming device 140 fixed. Alternatively, with the position of the intermediate film 2 in the TD direction fixed, the first trimming device 140 may trim the intermediate film 2 while moving periodically in the TD direction. In the example of FIG. 1, the first trimming device 140 trims the intermediate film 2 that moves periodically relative to the first trimming device 140. In another example, the first trimming device 140 may trim the intermediate film 2 while moving periodically relative to the intermediate film 2.

[0052] In the first trimming step, the oscillation amplitude of the long intermediate film is preferably 20 mm or more, more preferably 30 mm or more, while preferably 200 mm or less, more preferably 60 mm or less. By setting the amplitude to be equal to or greater than the lower limit, in the production of a long stretched film for general optical applications, the generation of gauge bands and transverse bands can be particularly well reduced. Also, by setting the amplitude to be equal to or less than the upper limit, a winding body of a stretched film with a high yield can be manufactured.

[0053] The first trimming step can usually be performed without causing the film to expand or contract in the width direction. Therefore, the center in the width direction of the intermediate film and the end portion of the intermediate film can oscillate substantially parallel to each other. Therefore, by observing the width of the ear instead of observing the center in the width direction of the intermediate film, it is also possible to measure the amplitude and the length of the period of the oscillation.

[0054] By performing the first trimming step, a trimmed intermediate film is obtained, which is further conveyed and supplied to the second stretching step. Referring to the example of FIG. 3, the trimmed intermediate film 3 is conveyed in the MD direction with its ends being linear and seemingly not oscillating. That is, the center of the trimmed intermediate film 3 becomes a straight line substantially parallel to the MD direction as indicated by the broken line 3C. However, in the trimmed intermediate film 3, thickness unevenness exists in an oscillating state. For example, in the trimmed intermediate film 3, relatively thick portions that cause gauge bands exist in a wavy shape. As a result, it becomes possible to easily obtain a wound body with few gauge bands and transverse streaks without further oscillation in the following steps.

[0055] The intermediate film after the first stretching step may have irregular portions of unevenness and / or stretching ratio at both of its ends. Therefore, by performing the first trimming step, portions where such irregular portions of unevenness and / or stretching ratio exist can be removed, and the subsequent steps can be performed smoothly.

[0056] In the process of manufacturing a wound body of a stretched film of a product from a pre-stretched film, generally, the higher the number of trimming operations, the lower the yield of the stretched film of the product. Also, after the oscillation process, generally, a trimming process for trimming both ends (ears) of the long film is required. Further, when a second stretching process is performed after the first stretching process, in order to perform the second stretching process smoothly, it is preferable to perform a trimming process for trimming both ends of the long film that has passed through the first stretching process before the second stretching process. In particular, when a transverse uniaxial stretching process using a tenter stretching machine is performed as the second stretching process, it is preferable to perform a trimming process to reduce poor gripping of the film by the tenter stretching machine. Therefore, conventionally, when the oscillation process, the first stretching process, and the second stretching process are performed in this order, at least a total of two trimming processes, after the oscillation process and before performing the second stretching process, have been required, so the yield tended to be low. On the other hand, in the manufacturing method of the present embodiment in which the first stretching process is performed before the oscillation process and the second stretching process is performed after the oscillation process, in the oscillation process, even if there are irregularities and / or irregular stretching ratio portions at both ends of the intermediate film, since it is difficult to affect the oscillation operation, it is possible not to perform a trimming process immediately after the first stretching process. As a result, in the manufacturing method of the present embodiment, compared with the case of performing a two-stage stretching process including the first and second stretching processes after the oscillation process, the number of trimming operations can be reduced, the yield is good, and a wound body of a stretched film can be manufactured.

[0057] <2.5. Second Stretching Process> In the second stretching process, the trimmed long intermediate film is stretched to form a long stretched film. The second stretching process is usually performed after the oscillation process. By performing the second stretching process after the oscillation process, it is possible to correct the change in the orientation angle that may occur due to the oscillation process and suppress a decrease in the accuracy of the orientation angle.

[0058] Examples of stretching modes include longitudinal stretching, lateral stretching, diagonal stretching, and stretching performed sequentially or simultaneously by combining these. In one embodiment, it is preferable to perform stretching in a direction different from the stretching direction in the first stretching step, more preferably to perform uniaxial stretching in a direction different from the stretching direction in the first stretching step, still more preferably to perform longitudinal uniaxial stretching in the first stretching step and lateral uniaxial stretching in the second stretching step.

[0059] According to lateral uniaxial stretching using a lateral stretching machine such as a tenter stretching machine, it is easy to control the stretching ratio of the film and the orientation angle of the film. Therefore, by performing longitudinal uniaxial stretching in the first stretching step and lateral uniaxial stretching in the second stretching step, while achieving a high total stretching ratio by longitudinal stretching and lateral stretching, it is possible to facilitate the control of the orientation angle of the stretched film and improve the accuracy of the orientation angle.

[0060] The stretching temperature can be, for example, Tg or higher and Tg + 20°C or lower, where Tg is the glass transition temperature of the resin contained in the film before stretching.

[0061] The stretching ratio E2 in the second stretching step is, for example, 1.30 times or more, for example, 1.20 times or more, and for example, 3.00 times or less, for example, 2.50 times or less.

[0062] <2.6. Winding Step> In the winding step, a long stretched film is wound into a roll to obtain a wound body of the long stretched film.

[0063] In the manufacturing method of the present embodiment, before the winding step, a step of overlapping a masking film on the stretched film may be performed. That is, a masking film is overlapped on the stretched film, and these are wound in the winding step while being overlapped, whereby a wound body in which the stretched film and the masking film are alternately positioned in the radial direction can be obtained.

[0064] By performing the step of laminating the masking film, the thickness unevenness present in the stretched film is absorbed by the deformation of the masking film, and defects caused by continuous thickness unevenness such as gauge bands and horizontal bands can be further reduced. Further, by laminating the masking film, even if the stretched film is a film with low slipperiness, the occurrence of scratches in the wound body can be suppressed.

[0065] However, according to the manufacturing method of the present application, the occurrence of defects caused by continuous thickness unevenness can be reduced by the oscillation step. Therefore, even if the step of laminating the masking film is not performed, a wound body with a reduced occurrence of these defects can be obtained. Further, by means such as appropriately selecting the material of the pre-stretched film to be supplied, the surface roughness Ra of at least one surface of the long stretched film obtained by the second stretching step is preferably in the range of 5 to 50 nm, more preferably 10 to 30 nm. By doing so, the slipperiness of the stretched film can be improved, and the occurrence of scratches can also be reduced. Therefore, by these means, even if the masking film is omitted, a wound body of the stretched film having the same quality as that when the masking film is provided can be obtained. In the manufacture of the wound body, the cost of the masking film can account for a large proportion of the manufacturing cost. Therefore, the fact that the same quality can be obtained even if the masking film is omitted is a significantly advantageous effect.

[0066] <2.7. Optional Step: Second Trimming Step> The manufacturing method of the present embodiment may further include a second trimming step of trimming both ends of the long stretched film after the second stretching step and before the winding step.

[0067] Similar to the intermediate film after the first stretching process, the stretched film after the second stretching process may have irregularities and / or irregular portions of the stretching ratio at both ends thereof. This tendency is particularly prominent when a specific stretching machine such as a tenter stretching machine is used in the second stretching process. Therefore, by performing the second trimming process, portions where such irregularities and / or irregular portions of the stretching ratio exist can be removed, and a higher-quality wound body can be manufactured.

[0068] The second trimming process can be performed in the same manner as the first trimming process. For example, as shown in FIG. 1, the stretched film 4 is supplied to the second trimming device 160 in the second trimming process, and here, trimming similar to the first trimming device 140 can be performed by a cutter, a support roller 161, and a winding roller 162. Thereby, a trimmed stretched film 5 is obtained, and one ear 61 can be cut and recovered.

[0069] <2.8. Optional Process: Process of Forming Concavo-Convex Portions> The manufacturing method of the present embodiment may further include a process of forming concavo-convex portions at both ends of the long stretched film after the second stretching process and before the winding process. By performing a process of forming concavo-convex portions (concave portions and convex portions) at both ends of the stretched film, an air layer is formed between the wound stretched films in the wound body of the stretched film, and the adhesion of the wound stretched films can be reduced.

[0070] There is no limitation on the method of forming the concave and convex portions. The concave and convex portions may be formed, for example, by embossing. When forming the concave and convex portions by embossing, for example, a roll-shaped or ring-shaped mold (e.g., a knurl, etc.) having a concavo-convex pattern corresponding to the shape of the concave and convex portions on the side surface is prepared, and while heating the stretched film or the mold as necessary, the stretched film is pressed with the mold. At this time, pressing may be performed with a single mold, or the stretched film may be sandwiched between two opposing molds and pressed. Thereby, the concavo-convex pattern of the mold is transferred to the stretched film, and the concavo-convex portions are formed.

[0071] Further, for example, recesses and protrusions may be formed by irradiating a laser beam. When a laser beam is irradiated onto the stretched film, local heat melting or ablation occurs in the stretched film at the point where the laser beam is irradiated. At this time, part or all of the material of the stretched film heat-melted by the irradiation of the laser beam becomes fluidized, so that a depression is formed at the point where the laser beam is irradiated, and a protrusion is formed around it, thereby forming the recess and the protrusion. By forming the recess and the protrusion with the laser beam in this way, even in a thin stretched film, breakage of the stretched film during the formation of the recess and the protrusion can be prevented. Further, even when the stretched film is bent, breakage hardly occurs at the uneven portions. This is presumably because, when forming the recess and the protrusion with the laser beam as compared with, for example, an embossing process, no unnecessary pressing is applied to the stretched film, and residual stress hardly remains in the stretched film.

[0072] <2.9. Optional process: Preliminary winding process> The manufacturing method of the present embodiment further includes a preliminary winding step of winding the trimmed long intermediate film into a roll shape to obtain a preliminary wound body after the first trimming step and before the second stretching step, and feeding the trimmed long intermediate film from the preliminary wound body obtained in the preliminary winding step to the second stretching step. When such a preliminary winding step is performed, the number of steps increases. However, by performing the preliminary winding step, it becomes possible to perform highly flexible manufacturing such as performing up to the preliminary winding step on one production line and then performing subsequent steps in parallel on a plurality of production lines. Therefore, it is possible to reduce the cost in equipment investment for the oscillation step and the like, and perform manufacturing at a lower cost.

[0073] FIG. 4 is a schematic diagram showing an example of a manufacturing apparatus capable of performing a method for manufacturing a wound body including a preliminary winding step. The manufacturing apparatus 2000 includes, in order from the upstream of the manufacturing line, a first pay-out device 110, a first stretching device 120, an oscillation device 130, a first trimming device 140, a winding device 280, a second pay-out device 210, a second stretching device 150, a second trimming device 160, laser light irradiation devices 170, 170, and a winding device 180. The winding device 280 performs a preliminary winding process of winding the intermediate film 3 trimmed in the first trimming process into a roll shape to manufacture a preliminary wound body 331. The second pay-out device 210 including the preliminary wound body 331 pays out the trimmed intermediate film 3 and supplies the trimmed intermediate film 3 to the second stretching device 150.

[0074] <2.10. Optional process: Process of forming a resin layer> The manufacturing method of the present embodiment may include a process of forming a resin layer made of a resin containing particles on the intermediate film or the stretched film after the supply process and before the winding process. By including the process of forming a resin layer in the manufacturing method of the present embodiment, a wound body of a stretched film including a resin layer made of a resin containing particles can be obtained.

[0075] Examples of the particles contained in the resin for forming the resin layer include inorganic particles such as silica particles and organic particles such as rubber particles, and among them, silica particles are preferable. By the resin for forming the resin layer containing particles, a desired surface roughness is imparted to the surface of the obtained stretched film, and the slipperiness of the stretched film can be improved.

[0076] The content ratio of the particles in the resin for forming the resin layer can be, for example, 1% by weight or more and, for example, 60% by weight or less. The number average particle diameter of the particles can be, for example, 50 nm or more and, for example, 800 nm or less.

[0077] Examples of the material for forming the resin layer are not particularly limited, and include urethane resin and acrylic resin, and preferably urethane resin. The urethane resin is a resin containing polyurethane. Examples of the polyurethane that can be contained in the urethane resin include, for example, (i) a polyurethane obtained by reacting a component containing an average of two or more active hydrogens in one molecule with (ii) a polyvalent isocyanate component; or a polyurethane produced by subjecting the above components (i) and (ii) to a urethanization reaction in an organic solvent that is inert to the reaction and has a high affinity for water under conditions of an excess of isocyanate groups to obtain an isocyanate group-containing prepolymer, then neutralizing the prepolymer, chain-extending it using a chain extender, and adding water to form a dispersion. These polyurethanes may contain an acid structure (acid residue). The number average molecular weight of the polyurethane is preferably 1,000 or more, more preferably 20,000 or more, preferably 1,000,000 or less, and more preferably 200,000 or less.

[0078] In addition to the polyurethane, the urethane resin may contain any components such as a heat stabilizer, a weather stabilizer, a leveling agent, an antistatic agent, a slip agent, an antiblocking agent, an antifogging agent, a lubricant, a dye, a pigment, a natural oil, a synthetic oil, and a wax, in combination with the particles. The optional components may be used alone or in combination of two or more in any ratio.

[0079] The thickness of the resin layer is preferably 0.01 μm or more, more preferably 0.02 μm or more, particularly preferably 0.03 μm or more, and preferably 5 μm or less, more preferably 2 μm or less, and particularly preferably 1 μm or less. When within the above range, sufficient slipperiness can be imparted to the stretched film, and the warping of the stretched film can be suppressed.

[0080] For example, the resin layer may contain silica particles as particles and may contain a urethane resin as the resin.

[0081] Examples of methods for forming the resin layer are not particularly limited, and for example, it may be formed by a coating method. In the coating method, a coating solution containing components that may be included in the resin layer, or components that can generate components that may be included in the resin layer (for example, monomers that can generate polymers, etc.) is prepared. Then, this coating solution is applied to the intermediate film that has undergone the first stretching process or the stretched film that has undergone the second stretching process as the base material layer to form a film of the coating solution, and if necessary, this film is cured to produce the resin layer.

[0082] For example, when forming the resin layer with a urethane resin containing particles, this resin layer can be produced using a coating solution containing polyurethane, particles, a solvent, and optionally any components. As the coating solution containing polyurethane as described above, it is preferable to use a coating solution containing water as the solvent. In such a coating solution containing water as the solvent, usually, the polyurethane is dispersed in water. The coating solution containing the polyurethane and water may be called an "aqueous urethane resin".

[0083] As the aqueous urethane resin, commercially available aqueous urethane resins may be used. Examples of the aqueous urethane resin include the "Adekabontiter" series manufactured by Asahi Denka Kogyo Co., Ltd., the "Orester" series manufactured by Mitsui Toatsu Chemicals, Inc., the "Bondic" series and the "Hydran" series manufactured by Dainippon Ink and Chemicals, Inc., the "Impranil" series manufactured by Bayer AG, the "Sofuranate" series manufactured by Nippon Soflan Co., Ltd., the "Pois" series manufactured by Kao Corporation, the "Sampleen" series manufactured by Sanyo Chemical Industries, Ltd., the "Izerax" series manufactured by Hodogaya Chemical Co., Ltd., the "Superflex" series manufactured by Daiichi Kogyo Seiyaku Co., Ltd., the "Neorets" series manufactured by Zeneca, etc. These may be used alone or in combination of two or more in any ratio.

[0084] The coating method of the coating solution is not particularly limited, and for example, it can be applied using a coater such as a gravure coater, a bar coater, a reverse coater, a kiss coater, a spray coater, etc.

[0085] When a resin layer is formed on a pre-stretched film (intermediate film) that has undergone the first stretching process, the intermediate film with the resin layer formed thereon is stretched in the second stretching process to become a stretched film that includes a base material layer, which is the layer where the pre-stretched film was stretched, and a stretched resin layer. The resin layer becomes a layer on at least one surface side of the normal stretched film. When a resin layer is formed on the stretched film that has undergone the second stretching process, the stretched film includes a base material layer, which is the layer where the pre-stretched film was stretched, and a resin layer. The resin layer becomes a layer on at least one surface side of the normal stretched film. Since the resin layer is a layer on at least one surface side of the stretched film, the slipperiness of the stretched film can be improved.

[0086] <2.11. Specific Examples of the Pre-Stretched Film> As the material of the pre-stretched film, any material suitable for the use of the stretched film can be appropriately selected and used. As the material of the pre-stretched film, a thermoplastic resin is preferred. Examples of polymers that can be included in the thermoplastic resin include acrylic polymers, methacrylic polymers, polycarbonate polymers, polyester polymers, polyethersulfone polymers, polyarylate polymers, polyimide polymers, chain polyolefin polymers, polyethylene terephthalate polymers, polysulfone polymers, polyvinyl chloride polymers, diacetyl cellulose polymers, triacetyl cellulose polymers, polymers containing an alicyclic structure, etc. Among these, polymers containing an alicyclic structure are preferred. These polymers may be used alone, or two or more of them may be combined in any ratio.

[0087] The polymer containing an alicyclic structure is a thermoplastic polymer having an alicyclic structure in the main chain and / or side chain. Among the polymers containing an alicyclic structure, alicyclic olefin polymers are preferred. The alicyclic olefin polymer is a polymer containing a structural unit having a structure that can be obtained by the polymerization of an alicyclic olefin and its hydrogenated product. However, the alicyclic olefin polymer is not limited by its polymerization method.

[0088] Examples of the alicyclic structure in the alicyclic structure-containing polymer include a saturated alicyclic hydrocarbon (cycloalkane) structure, an unsaturated alicyclic hydrocarbon (cycloalkene) structure, etc. From the viewpoints of mechanical strength, heat resistance, etc., a cycloalkane structure is preferred. There is no particular limitation on the number of carbon atoms constituting the alicyclic structure, but when it is usually 4 to 30, preferably 5 to 20, more preferably 5 to 15, the characteristics of mechanical strength, heat resistance, and film formability are highly balanced and suitable.

[0089] The proportion of the repeating unit having an alicyclic structure constituting the alicyclic structure-containing polymer is preferably 55% by weight or more, more preferably 70% by weight or more, particularly preferably 90% by weight or more, and is usually 100% by weight or less, and may be 100% by weight. When the proportion of the repeating unit having an alicyclic structure in the alicyclic structure-containing polymer is within this range, it is preferable from the viewpoints of transparency and heat resistance.

[0090] Examples of the alicyclic structure-containing polymer, particularly examples of the alicyclic olefin polymer, include norbornene polymers, monocyclic cyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, and hydrides thereof. Among these, norbornene polymers can be preferably used because of their good transparency and moldability.

[0091] Examples of the norbornene polymer include, for example, a ring-opening polymer of a monomer having a norbornene structure or a ring-opening copolymer of a monomer having a norbornene structure and another monomer, or a hydride thereof; an addition polymer of a monomer having a norbornene structure or an addition copolymer of a monomer having a norbornene structure and another monomer, or a hydride thereof. Among these, the hydride of the ring-opening (co)polymer of the monomer having a norbornene structure can be particularly preferably used from the viewpoints of transparency, moldability, heat resistance, low moisture absorption, dimensional stability, light weight, etc. These polymers may be used alone or in combination of two or more in any ratio.

[0092] The molecular weight of the polymer that can be contained in the thermoplastic resin is appropriately selected according to the intended use. When cyclohexane is used as the solvent or the polymer is insoluble in cyclohexane, the weight average molecular weight (Mw) in terms of polyisoprene measured by gel permeation chromatography using toluene (in the case where the solvent is toluene, in terms of polystyrene) is, for example, 10,000 or more, preferably 15,000 or more, more preferably 20,000 or more, and for example, 100,000 or less, preferably 80,000 or less, more preferably 50,000 or less. When the weight average molecular weight is within such a range, the mechanical strength and moldability of the resulting stretched film are highly balanced.

[0093] The film before stretching may be a film having a single-layer structure or a film having a multilayer structure. For example, the film before stretching may be a multilayer film including a base material layer and the above-described resin layer made of a resin containing particles. Examples of the base material layer that can be included in the film before stretching include a layer containing an alicyclic structure-containing polymer. Examples of the resin that can form the resin layer included in the film before stretching include the above-described resins exemplified in the description of the step of forming the resin layer.

[0094] In one embodiment, the film before stretching includes a base material layer containing an alicyclic structure-containing polymer and a resin layer made of a urethane resin containing silica particles, and it is preferable that the resin layer is a layer on at least one surface side of the film before stretching. When the film before stretching having such a multilayer structure is used in the supply step, the resulting stretched film includes a stretched resin layer and a stretched base material layer, and since the stretched resin layer becomes a layer on at least one surface side of the stretched film, the slipperiness of the stretched film can be improved.

[0095] There are no particular restrictions on the method for manufacturing the pre-stretched film. For example, the pre-stretched film can be manufactured by a resin molding method such as a melt extrusion molding method or a casting molding method, and it is preferably a film manufactured by a melt extrusion molding method. Further, when the pre-stretched film is a multi-layer film having two or more layers, each layer constituting the multi-layer film (for example, a base material layer containing an alicyclic structure-containing polymer and a resin layer made of the resin containing the above-mentioned particles) may be simultaneously formed by a resin molding method such as a co-extrusion method or a co-casting method to manufacture the multi-layer film.

[0096] Further, when the pre-stretched film is a multi-layer film, a part of the layers constituting the multi-layer film may be formed by a coating method. For example, the resin layer may be formed by a coating method.

[0097] The pre-stretched film is usually a film that has not been subjected to a stretching treatment. The retardation in the in-plane direction of the pre-stretched film is, for example, 20 nm or less, for example, 15 nm or less, for example, 5 nm or less, and is usually 0 nm or more, and may be 5 nm.

[0098] <3. Specific Examples of the Stretched Film> In the stretched film obtained by the manufacturing method of the present embodiment, among the two surfaces of the stretched film, the surface roughness Ra of at least one of the surfaces is preferably 5 nm or more, more preferably 10 nm or more, and preferably 50 nm or less, more preferably 30 nm or less. Here, the surface roughness Ra means the arithmetic mean roughness measured in accordance with JIS B0601. When the surface roughness Ra of the stretched film is equal to or higher than the lower limit of the above range, the slipperiness of the stretched film is improved. Therefore, when the stretched film is used as a wound body, defects such as scratches caused by contact and rubbing between the wound stretched films can be reduced. When the surface roughness Ra of the stretched film is equal to or lower than the upper limit, the state of the wound body of the stretched film is stable, and deformation due to a force in a direction parallel to the axial direction of the wound body of the stretched film is less likely to occur. As a result, it is possible to reduce the occurrence of defects such as unevenness and wrinkles in the stretched film due to the deformation of the wound body.

[0099] The surface roughness Ra of the stretched film can be adjusted, for example, by incorporating particles into the film before stretching or the material for forming the stretched film and adjusting the content of the particles and / or the average particle diameter of the particles.

[0100] <4. Use of the wound body of the stretched film> The wound body of the stretched film produced by the above-described production method can be applied to films for any use, such as optical films, moisture-proof films, packaging films, conductive films, insulating films, antistatic films, barrier films, films for wiring boards, etc. Among them, from the viewpoint of effectively utilizing the advantage that defects can be reduced, the production method of the wound body of the stretched film of the present invention is preferably used for optical films. Examples of the optical film include a retardation film, a protective film for a polarizing plate, a polarizing film, a brightness enhancement film, a light diffusion film, a condenser film, a reflection film, and the like.

Explanation of symbols

[0101] 1 Film before stretching 2, 3 Intermediate film 4, 5, 6 Stretched film 7 Wound body 41 Ear 61 Ear 331 Preliminary wound body 110 First feeding device 120 First stretching device 121, 122 Stretching rolls 130 Oscillation device 131, 132 Steering rolls 133, 134 Conveying rolls 140 First trimming device 141 Support roller 142 Take-up roller 150 Second stretching device 160 Second trimming device 161 Support roller 162 Take-up roller 170 Laser light irradiation device 180 Winding device 210 Second unwinding device 280 Winding device 1000, 2000 Manufacturing device for winding body

Claims

1. A method for manufacturing a wound body of a stretched film, comprising: a supply step of supplying a long pre-stretched film; a first stretching step of stretching the long pre-stretched film to form a long intermediate film; an oscillation step of oscillating the long intermediate film; a first trimming step of trimming both ends of the oscillating long intermediate film; a second stretching step of stretching the trimmed long intermediate film to form a long stretched film; a winding step of winding the long stretched film into a roll to obtain a wound body of the long stretched film. A method for manufacturing a wound body of a stretched film, comprising the above steps.

2. The manufacturing method according to claim 1, further comprising a second trimming step of trimming both ends of the long stretched film after the second stretching step and before the winding step.

3. The manufacturing method according to claim 1, wherein the stretching ratio E2 in the second stretching step is larger than the stretching ratio E1 in the first stretching step.

4. The manufacturing method according to claim 1, further comprising a step of forming uneven portions on both ends of the long stretched film after the second stretching step and before the winding step.

5. The manufacturing method according to claim 4, wherein the uneven portions are formed by irradiating laser light.

6. The manufacturing method according to claim 1, wherein the long pre-stretched film supplied in the supply step is a film formed by a melt extrusion molding method.

7. After the first trimming step and before the second stretching step, the method further comprises a preliminary winding step of winding the trimmed long intermediate film into a roll to obtain a preliminary wound body, and feeding out the trimmed long intermediate film from the preliminary wound body obtained in the preliminary winding step and supplying it to the second stretching step.

8. The manufacturing method according to claim 1, wherein the amplitude of oscillation of the long intermediate film in the first trimming step is 20 mm or more and 200 mm or less.

9. The manufacturing method according to claim 1, wherein the surface roughness Ra of at least one surface of the long stretched film is 5 nm or more and 50 nm or less.

10. The method of manufacturing according to claim 1, wherein the long stretched film includes a base material layer containing an alicyclic structure-containing polymer and a resin layer made of a urethane resin containing silica particles, and the resin layer is a layer on at least one surface side of the long stretched film.

Images