Method for manufacturing end film

Abstract

To provide a method for manufacturing an end film which can smoothly manufacture an end film that can suppress breakage.SOLUTION: A method for manufacturing an end film includes: a stretching step of stretching a long resin film in a direction crossing a long direction, in a state in which both ends in a width direction of the resin film are gripped by a clip, and preparing a stretched film; and a cutting step of cutting each of both ends including a gripping mark of the clip from the stretched film, and separating it into an end film including the gripping mark and a product film. In the resin film subjected to the stretching step, each of both of the ends in the width direction is composed as a thick part, and a part positioned between the two thick parts is composed as a thin part. In the stretching step, the thick parts are gripped by the clip.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an end film.

Background Art

[0002] The stretched film widely used in various industrial products is manufactured by stretching a resin film. For example, a method for manufacturing a stretched film has been proposed in which both end portions in the width direction of a long resin film are gripped by clips and the resin film is stretched in a direction intersecting the long direction (see, for example, Patent Document 1). In such a method for manufacturing a stretched film, gripping marks of the clips are generated at both end portions in the width direction of the stretched film. Therefore, generally, the end portions including the gripping marks are cut off from the stretched film and discarded. In recent years, from the viewpoint of reducing the environmental load, reuse of waste generated during the manufacture of various industrial products has been desired. Therefore, in the method for manufacturing a stretched film described in Patent Document 1, it has been studied to collect the end portions cut from the stretched film as end films and effectively use them. However, when collecting the end film, the end film may break and the end film may not be smoothly collected.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made to solve the above conventional problems, and its main object is to provide a method for manufacturing an end film capable of smoothly manufacturing an end film capable of suppressing breakage.

Means for Solving the Problems

[0005] [1] The method for manufacturing an end film according to an embodiment of the present invention includes a stretching step of stretching a resin film in a direction intersecting the longitudinal direction while gripping both end portions in the width direction of the long resin film with clips to prepare a stretched film; and a cutting step of cutting both end portions including the gripping marks of the clips from the stretched film to separate the end film including the gripping marks and a product film. In the resin film used in the stretching step, both end portions in the width direction are each configured as a thick portion, and a portion located between the two thick portions is configured as a thin portion. In the stretching step, the thick portion is gripped by the clip. [2] In the method for manufacturing an end film according to [1] above, the difference between the thickness of the thick portion and the thickness of the thin portion may be 20 μm or more. [3] In the method for manufacturing an end film according to [1] or [2] above, the difference between the thickness of the thick portion and the thickness of the thin portion may be 30 μm or less. [4] In the method for manufacturing an end film according to any one of [1] to [3] above, the thickness of the thick portion may be 90 μm or more. [5] The method for manufacturing an end film according to any one of [1] to [4] above may further include a step of winding the end film by a winding member. [6] In the method for manufacturing an end film according to any one of [1] to [5] above, the resin film used in the stretching step may be a formed film in which the thick portion and the thin portion are integrally formed. [7] In the method for manufacturing an end film according to any one of [1] to [5] above, the resin film may have a substantially uniform thickness. In this case, the thick portion is formed by folding back the end portion in the width direction of the resin film. [8] In the method for manufacturing an end film according to any one of [1] to [5] above, the resin film may include a film body having a substantially uniform thickness and an adhesive film attached to an end portion in the width direction of the film body. The adhesive film is made of the same material as the film body. In this case, the thick portion includes the film body and the adhesive film.

Effect of the Invention

[0006] According to an embodiment of the present invention, an end film capable of suppressing breakage can be smoothly manufactured.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. Also, for the purpose of making the description clearer, the drawings may schematically show the width, thickness, shape, etc. of each part as compared with the embodiments, but this is merely an example and does not limit the interpretation of the present invention.

[0009] (Definition of Terms and Symbols) The definitions of the terms and symbols in this specification are as follows. (1) Refractive index (nx, ny, nz) “nx” is the refractive index in the direction where the in-plane refractive index is maximum (i.e., the slow axis direction), “ny” is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and “nz” is the refractive index in the thickness direction. (2) In-plane retardation (Re) “Re(λ)” is the in-plane retardation measured with light of wavelength λ nm at 23°C. For example, “Re(550)” is the in-plane retardation measured with light of wavelength 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). (3) Angle When referring to an angle in this specification, unless otherwise specified, the angle includes angles in both clockwise and counterclockwise directions.

[0010] A. Outline of the method for manufacturing the end film FIG. 1 is a schematic configuration diagram for explaining the method for manufacturing the end film according to one embodiment of the present invention; FIG. 2 is a plan view of the resin film of FIG. 1; FIG. 3 is a schematic cross-sectional view of the resin film of FIG. 2; FIG. 4 is a schematic cross-sectional view of the resin film according to another embodiment of the present invention; FIG. 5 is a schematic cross-sectional view of the resin film according to still another embodiment of the present invention; FIG. 6 is a schematic plan view of the stretched film of FIG. 1.

[0011] The method for manufacturing an end film according to an embodiment of the present invention includes a stretching step and a cutting step in this order (see FIG. 1). In the stretching step, while gripping both end portions in the width direction of the long resin film 1 with clips, the resin film 1 is stretched in a direction intersecting the long direction to prepare a stretched film 2. In the cutting step, both end portions including the gripping marks 22 of the clips are cut from the stretched film 2 to separate it into an end film 3 including the gripping marks 22 and a product film 4. In the resin film 1 provided in the stretching step, both end portions in the width direction are each configured as a thick portion 11, and a portion located between the two thick portions 11 is configured as a thin portion 12 (see FIGS. 2 to 5). In the stretching step, the thick portion 11 is gripped by a clip. The inventors have discovered that when recovering (manufacturing) the end film, the gripping mark of the clip becomes the starting point of a crack and causes the end film to break. Therefore, as a result of intensive studies on the recovery means of the end film, it has been found that the occurrence of cracks can be suppressed by adjusting the thickness of the portion where the gripping mark of the clip is formed. Specifically, both end portions in the width direction of the resin film 1 provided in the stretching step are configured as thick portions 11, and the thick portions 11 are gripped by clips to stretch the resin film 1. In the stretched film 2 thus obtained, the gripping marks 22 of the clips are formed in relatively thick portions. Then, in the cutting step, since the stretched film 2 is separated into an end film 3 including the gripping marks 22 of the clips and a product film 4, the gripping marks 22 can be arranged in a portion of the end film 3 that is thicker than the product film 4, and the product film 4 can be thinned. Therefore, the end film 3 that can suppress breakage can be smoothly manufactured (recovered). In other words, the method for manufacturing an end film according to an embodiment of the present invention is a method for recovering an end film. Also, in one embodiment, the thinned product film 4 can be smoothly manufactured together with the end film 3.

[0012] As shown in FIG. 3, the thick portion 11 is thicker than the thin portion 12. The difference D between the thickness T1 of the thick portion 11 and the thickness T2 of the thin portion 12 is, for example, 3 μm or more, preferably 5 μm or more, more preferably 10 μm or more, still more preferably 15 μm or more, and particularly preferably 20 μm or more. If the thickness difference between the thick portion and the thin portion is equal to or greater than the above lower limit, the thickness of the portion where the gripping mark of the clip is formed in the end film can be sufficiently ensured, and the breakage of the end film can be stably suppressed. Further, when the clip grips the thick portion in the stretching process, it is possible to suppress the clip from coming into contact with the thin portion.

[0013] The difference D between the thickness T1 of the thick portion 11 and the thickness T2 of the thin portion 12 is, for example, 60 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, and particularly preferably 30 μm or less. If the thickness difference between the thick portion and the thin portion is equal to or less than the above upper limit, a product film having excellent appearance (that is, a product film with reduced thickness unevenness in the width direction) can be stably manufactured, and the yield of the product film can be improved.

[0014] The thickness T1 of the thick portion 11 can adopt any appropriate value so as to obtain the above-described thickness difference D. The thickness T1 of the thick portion 11 is, for example, 80 μm or more, preferably 90 μm or more, more preferably 100 μm or more, still more preferably 110 μm or more, and particularly preferably 120 μm or more, and is, for example, 160 μm or less, preferably 150 μm or less, more preferably 140 μm or less, still more preferably 130 μm or less. If the thickness of the thick portion is equal to or greater than the above lower limit, the breakage of the end film can be more stably suppressed. If the thickness of the thick portion is equal to or less than the above upper limit, the clip can stably grip the thick portion in the stretching process, and the resin film can be stretched accurately.

[0015] The thickness T2 of the thin portion 12 is arbitrarily and appropriately adjusted according to the thickness T1 of the thick portion 11 so as to be the above-described thickness difference D. The thickness T2 of the thin portion 12 is, for example, 70 μm or more, preferably 80 μm or more, more preferably 90 μm or more, and even more preferably 100 μm or more, and is, for example, less than the lower limit of the thickness T1 of the thick portion 11 described above. The thin portion 12 typically has a substantially uniform thickness. The difference between the maximum value and the minimum value of the thickness in the thin portion 12 is, for example, less than 3 μm, preferably 1 μm or less. The lower limit of the difference between the maximum value and the minimum value of the thickness in the thin portion 12 is typically 0 μm.

[0016] In one embodiment, the resin film 1 to be subjected to the stretching process is a formed film 1a in which the thick portion 11 and the thin portion 12 are integrally formed. When the resin film is a formed film having a thick portion and a thin portion integrally, the formed film can be smoothly stretched in the stretching process. The formed film 1a is manufactured by any appropriate resin molding method, typically extrusion molding using a die.

[0017] Also, as shown in FIG. 4, the resin film 1 may have a substantially uniform thickness. In this case, when the resin film 1 is subjected to the stretching process, the end portions in the width direction of the resin film 1 are folded back to form the thick portion 11. Also by this, the resin film can be smoothly stretched in the stretching process. In the present embodiment, the range of the thickness of the resin film 1 before folding back is, for example, the same as the range of the thickness of the thin portion described above. Also, the range of the difference between the maximum value and the minimum value of the thickness of the resin film 1 before folding back is, for example, the same as the range of the difference between the maximum value and the minimum value of the thickness of the thin portion described above.

[0018] Furthermore, as shown in FIG. 5, the resin film 1 may include a film body 13 and an adhesive film 14. The film body 13 has a substantially uniform thickness. The thickness range of the film body 13 is, for example, the same as the thickness range of the above-mentioned thin portion. Also, the range of the difference between the maximum value and the minimum value of the thickness of the film body 13 is, for example, the same as the range of the difference between the maximum value and the minimum value of the thickness of the above-mentioned thin portion. The attachment film 14 is attached to the end portion in the width direction of the film body 13 via an arbitrary appropriate adhesive layer (adhesive layer or pressure-sensitive adhesive layer). Thereby, the thick portion 11 is formed. That is, the thick portion 11 includes the end portion in the width direction of the film body 13 and the attachment film 14 laminated thereon. More specifically, the thick portion 11 is composed of the end portion in the width direction of the film body 13, an adhesive layer (not shown), and the attachment film 14. The attachment film 14 is composed of the same material as the film body 13. The thickness of the attachment film 14 is arbitrarily and appropriately adjusted so as to be the above-mentioned thickness difference D. Even if the resin film has such a configuration, the resin film can be smoothly stretched in the stretching process.

[0019] As shown in FIG. 6, in the cutting process, the above-mentioned resin film 1 is separated into an end film 3 including the gripping mark 22 of the clip and a product film 4. Thereafter, the end film 3 can be recovered by any appropriate means.

[0020] As shown in FIG. 1, in one embodiment, the method for manufacturing the end film further includes a first winding step in which the first winding member 6 winds up the end film 3. In the end film 3, the gripping mark 22 of the clip is formed in a portion derived from the thick portion 11 of the resin film 1. Therefore, flexibility that can be wound around the end film 3 can be imparted. As a result, in the first winding step, even if the end film 3 is wound up, breakage of the end film 3 can be suppressed. Thereby, the end film 3 can be smoothly recovered in a roll shape, and the end film roll 100 in which the end film 3 is wound in a roll shape can be smoothly manufactured. In the end film roll 100, the end film 3 is laminated in the radial direction of the first winding member 6.

[0021] The recovered end film is an article that can be circulated independently, is industrially applicable, and is typically used as a recycled resin raw material. The recycled resin raw material can be used in the production of any suitable resin product. Examples of resin products include optical films such as retardation films; packaging materials composed of thermoplastic resins such as polyethylene terephthalate (PET) and nylon. Among these resin products, optical films are preferably mentioned, and retardation films are more preferably mentioned. That is, the recovered end film can be suitably used as a raw material for optical films (typically retardation films).

[0022] Hereinafter, the details of each step of the method for manufacturing the end film will be described.

[0023] B. Stretching step In the stretching step, the long resin film 1 is typically stretched by a stretching device 8.

[0024] B-1. Resin film to be stretched The resin film 1 refers to the film before the stretching step in this specification. As described above, the resin film 1 has a long shape. The width of the resin film 1 (the dimension in the direction orthogonal to the long direction) is, for example, 500 mm or more, preferably 700 mm or more, and for example, 2500 mm or less, preferably 2000 mm or less.

[0025] Examples of the resin material constituting the resin film 1 include polycarbonate resins, polyvinyl acetal resins, cycloolefin resins, (meth)acrylic resins, cellulose ester resins, cellulose resins, polyester resins, polyester carbonate resins, olefin resins, and polyurethane resins. Note that the (meth)acrylic resin refers to an acrylic resin and / or a methacrylic resin. These resin materials can be used alone or in combination.

[0026] Among the resin materials constituting the resin film 1, preferably, polycarbonate (PC)-based resins, cycloolefin (COP)-based resins, (meth)acrylic-based resins, and polyester-based resins (typically, polyethylene terephthalate (PET)) are mentioned, and more preferably, PC-based resins are mentioned. When such resin materials are used, breakage of the end film can be suppressed more stably.

[0027] Examples of the PC resin include a PC resin containing a structural unit derived from a dihydroxy compound. Specific examples of the dihydroxy compound include 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-hydroxy-3-ethylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-propylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-sec-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-tert-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-cyclohexylphenyl)fluorene, 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene.In addition to the structural unit derived from the above dihydroxy compound, the PC-based resin may contain a structural unit derived from a dihydroxy compound such as isosorbide, isomannide, isoidide, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecanedimethanol (TCDDM), bisphenols, etc.

[0028] Details of the above-mentioned PC-based resin are described, for example, in JP-A-2012-67300 and Japanese Patent No. 3325560. The descriptions of the patent documents are incorporated herein by reference.

[0029] As shown in FIG. 2, when the resin film 1 is subjected to a stretching process, both end portions in the width direction are configured as thick portions 11, and the portion between the two thick portions 11 is configured as a thin portion 12. The thick portion 11 typically extends in the longitudinal direction of the resin film 1 and is provided over the entire width direction end portion. The width of the thick portion 11 is not particularly limited as long as the clip of the stretching device can grip the thick portion. When the width of the resin film 1 is taken as 100%, the width of the thick portion 11 is, for example, 0.5% or more, preferably 1.0% or more, and for example, 2.5% or less, preferably 5.0% or less. The width of the thick portion 11 is, for example, 10 mm or more, preferably 20 mm or more, and for example, 100 mm or less, preferably 50 mm or less. When the width of the thick portion is within the above range, when the clip of the stretching device grips the thick portion, it is possible to stably suppress the clip from contacting the thin portion.

[0030] B-2. Stretching Device As shown in FIG. 1, in one embodiment, the resin film 1 is conveyed in the longitudinal direction so as to pass through the stretching device 8. Therefore, the resin film 1 can be stretched while being conveyed, and the stretched film 2 can be continuously prepared.

[0031] The stretching device 8, although not shown in the figures, is provided with clips that can grip the thick portions described above. The stretching device 8 is typically a tenter stretching device. The stretching device 8 stretches the resin film 1 in a direction intersecting the longitudinal direction while gripping (typically clamping) each of the two thick portions in the resin film 1 with clips. The stretching direction may be a direction substantially orthogonal to the longitudinal direction of the resin film 1 (for example, 90° ± 1° with respect to the longitudinal direction), or may be a direction intersecting both the longitudinal direction and the width direction of the resin film 1.

[0032] Details of the stretching process are described, for example, in Japanese Patent No. 7096940, Japanese Patent Application Laid-Open No. 2004-226686, and International Publication No. 2007 / 111313. The descriptions in the said patent documents are incorporated herein by reference.

[0033] As a result, a long stretched film 2 is prepared (see FIG. 6). The stretching ratio in the width direction in the stretching process (width of the stretched film / width of the resin film) is, for example, 1.1 or more, preferably 1.5 or more, and is, for example, 6.0 or less, preferably 4.0 or less.

[0034] The gripping marks 22 of the clips are formed in the stretched film 2 at portions derived from the thick portions 11 of the resin film 1 and are located at both ends in the width direction. In the stretched film 2, the thickness of the portion where the gripping marks 22 of the clips are formed is thicker than that of the other portions.

[0035] The stretched film 2 typically has a slow axis in the stretching direction described above. The slow axis of the stretched film 2 may be misaligned in the width direction. More specifically, the direction of the slow axis of the stretched film 2 is likely to deviate from the desired angle at the width direction ends. This misalignment typically does not substantially occur at the center in the width direction of the stretched film 2 and increases as it approaches the width direction ends. In the stretched film 2 in the illustrated example, at the center in the width direction, the slow axis is substantially parallel to the stretching direction described above (for example, the misalignment is less than 0°±1°). Also, at the width direction ends of the stretched film 2, the slow axis may intersect the stretching direction described above (for example, the misalignment is 1° to 3°).

[0036] C. Cutting step As shown in FIG. 1, in the cutting step, both ends including the gripping mark 22 of the clip are typically cut from the stretched film 2 described above by a cutting device 5. In one embodiment, the stretched film 2 is conveyed in the longitudinal direction so as to pass through the cutting device 5. Thereby, the stretched film 2 can be continuously cut. The stretched film 2 is preferably subjected to the cutting step without contacting a roller member such as a conveying roller.

[0037] The cutting device 5 can have any suitable configuration. In the illustrated example, the cutting device 5 includes a gear cutter 51 and an opposing roller 52. The gear cutter 51 and the opposing roller 52 face each other. Each of the gear cutter 51 and the opposing roller 52 is rotatable. The gear cutter 51 can form a cutting line 21 on the stretched film 2 passing between the gear cutter 51 and the opposing roller 52 (see FIG. 6).

[0038] As shown in FIG. 6, the cutting device 5 typically forms two cutting lines 21 on the stretched film 2. The cutting lines 21 extend along the longitudinal direction of the stretched film 2. The two cutting lines 21 are formed at a predetermined interval from each other in the width direction of the stretched film 2, and each of the two cutting lines 21 is formed at a predetermined interval from the gripping mark 22 of the clip in the width direction of the stretched film 2.

[0039] As described above, two end films 3 corresponding to both end portions in the width direction of the stretched film 2 are obtained from the stretched film 2. Each of the two end films 3 includes the gripping marks 22 of the clips. Further, the stretched film 2 from which the two end films 3 are cut is configured as a product film 4. Each of the two end films 3 and the product film 4 has an elongated shape.

[0040] The width of the end film 3 is not particularly limited as long as the end film 3 includes the entire gripping marks 22 of the clips. When the width of the stretched film 2 is taken as 100%, the width of the end film 3 is, for example, 0.5% or more, preferably 1.0% or more, more preferably 5.0% or more, still more preferably 10.0% or more, and for example, 30% or less, preferably 25% or less, more preferably 20% or less. The width of the end film 4 is, for example, 10 mm or more, preferably 20 mm or more, more preferably 100 mm or more, still more preferably 200 mm or more, and for example, 600 mm or less, preferably 500 mm or less, more preferably 300 mm or less. When the width of the end film is equal to or greater than the above lower limit, the entire gripping marks of the clips can be stably included in the end film, and a portion of the stretched film where the above-mentioned axial deviation is relatively large can be included in the end film. As a result, it is possible to suppress the remaining of the gripping marks of the clips on the product film and reduce the axial deviation in the product film. When the width of the end film is equal to or less than the above upper limit, the yield of the product film can be improved.

[0041] The area ratio occupied by the gripping marks 22 in the end film 3 is, for example, 1.0% or more, preferably 5.0% or more, and for example, 95% or less, preferably 75% or less. When the area ratio occupied by the gripping marks is within the above range, a portion of the stretched film where the above-mentioned axial deviation is relatively large can be sufficiently included in the end film. Therefore, the axial deviation in the product film can be stably reduced.

[0042] The maximum thickness of the end film 3 (i.e., the thickness of the portion derived from the thick portion) is greater than the thickness of the product film 4. The maximum thickness of the end film 3 is, for example, 80 μm or more, preferably 90 μm or more, and, for example, 160 μm or less, preferably 150 μm or less. If the maximum thickness of the end film is within the above range, appropriate flexibility can be imparted to the end film.

[0043] D. First winding step As shown in FIG. 1, in the first winding step, the first winding member 6 winds up the end film 3 cut from the stretched film 2 by the cutting device 5. Thereby, the end film 3 can be continuously recovered, and the end film roll 100 can be manufactured. The first winding member 6 is typically rotatable about an axis substantially parallel to the width direction of the end film 3. In FIG. 1, for the sake of convenience, one first winding member 6 is illustrated, but in reality, the number of first winding members 6 provided is the same as the number of end films 3 (i.e., two). The first winding member 6 can have any suitable configuration. The first winding member 6 typically has a cylindrical shape.

[0044] The conveyance speed (line speed) of the end film 3 from the cutting device 5 toward the first winding member 6 is, for example, 50 mm / s or more, preferably 80 mm / s or more, and, for example, 1600 mm / s or less, preferably 1150 mm / s or less. When the line speed of the end film is within the above range, the tension applied to the end film can be adjusted to a suitable range, and breakage of the end film can be further suppressed.

[0045] E. Second winding step The product film 4 obtained in the cutting step is recovered by any suitable means. In one embodiment, the method for manufacturing the end film further includes a second winding step in which the second winding member 7 winds up the product film 4. In the second winding step, the product film 4 is wound around the second winding member 7 for recovery. Therefore, a product film roll 101 in which the product film 4 is wound in a roll shape can be manufactured. In the product film roll 101, the product film 6 is laminated in the radial direction of the second winding member 7. Note that the second winding member 7 can be described in the same manner as the first winding member 6.

[0046] The product film 4 is typically configured as a retardation film having a slow axis. The refractive index of the product film 4 shows a relationship of nx > ny. In one embodiment, the product film 4 functions as a λ / 4 plate. When the product film functions as a λ / 4 plate, the in-plane retardation Re(550) of the product film 4 is, for example, 100 nm to 180 nm, preferably 135 nm to 155 nm. In another embodiment, the retardation film functions as a λ / 2 plate. When the product film functions as a λ / 2 plate, the in-plane retardation Re(550) of the product film 4 is, for example, 230 nm to 310 nm, preferably 250 nm to 290 nm.

[0047] The wavelength dependence of the product film 4 is not particularly limited. The product film 4 preferably exhibits an inverse-dispersion wavelength dependence. Re(450) / Re(550) of the product film 4 is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.95. Also, Re(550) / Re(650) of the product film 4 is preferably 0.8 or more and less than 1.0, more preferably 0.8 to 0.97.

[0048] The absolute value of the photoelastic coefficient of the product film 4 is, for example, 2 × 10 -12 (m 2 / N) to 100 × 10 -12 (m 2 / N), and preferably 5 × 10 -12 (m 2 / N)~50×10 -12 (m 2 / N).

[0049] The thickness of the product film 4 (retardation film) is, for example, 60 μm or less, preferably 50 μm or less. The lower limit of the thickness of the product film 4 (retardation film) is typically 30 μm.

[0050] The product film 4 has substantially no thickness unevenness in the width direction. In the product film 4, the thickness unevenness calculated by the following formula (I) is, for example, 8% or less, preferably 6% or less. The lower limit of the thickness unevenness of the product film is typically 0%. Thickness unevenness={(T max -T min ) / T ave )×100···(I) (In formula (I), T max represents the maximum thickness of the product film. T min represents the minimum thickness of the product film. T ave represents the average thickness of the product film.)

Examples

[0051] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on mass. Also, the evaluation methods for the examples and comparative examples are as follows.

[0052] (1) Breakage The breakage in the end films recovered in the examples and comparative examples was visually confirmed and evaluated according to the following criteria. The results are shown in Table 1. 〇 (excellent): No breakage △ (good): Partial breakage (the film is connected) × (unacceptable): Complete breakage (2) Appearance The appearance of the product films of the examples and comparative examples was confirmed with a dial gauge and evaluated according to the following criteria. The results are shown in Table 1. 〇(Excellent): There is substantially no thickness unevenness in the width direction (the thickness unevenness calculated by the above formula (I) is 8% or less). △(Good): There is thickness unevenness in the width direction (the thickness unevenness calculated by the above formula (I) exceeds 8%).

[0053] <<Preparation of Resin Film>> <Preparation Example 1> In the same manner as in Production Example 9 of JP-A-2022-150732, a resin film (molded film) composed of a PC-based resin was prepared. The resin film integrally included two thick portions and a thin portion. The respective thicknesses of the thick portion and the thin portion are shown in Table 1.

[0054] <Preparation Example 2> As a resin film composed of PET, product number "50U48" manufactured by Toray Industries, Inc. was prepared. Next, the resin film was molded so as to integrally include two thick portions and a thin portion. The respective thicknesses of the thick portion and the thin portion are shown in Table 1.

[0055] <Preparation Example 3> As a resin film composed of an acrylic resin, product name "HTX-Z" manufactured by Kaneka Corporation was prepared. Next, the resin film was molded so as to integrally include two thick portions and a thin portion. The respective thicknesses of the thick portion and the thin portion are shown in Table 1.

[0056] <Preparation Example 4> As a resin film composed of a COP-based resin, product number "ZF16" manufactured by Nippon Zeon Co., Ltd. was prepared. Next, the resin film was molded so as to integrally include two thick portions and a thin portion. The respective thicknesses of the thick portion and the thin portion are shown in Table 1.

[0057] <Preparation Example 5> In the same manner as in Production Example 9 of JP-A-2022-150732, a resin film (molded film) composed of a PC-based resin was prepared. The resin film had a substantially uniform thickness and no thick portion. The thickness of the resin film is shown in Table 1.

[0058] [Examples 1 to 4] The resin film composed of the PC-based resin obtained in Preparation Example 1 was stretched to obtain a stretched film. More specifically, a stretched film was prepared in the same manner as in Production Example 9 of JP-A-2022-150732, except that the thick portion of the resin film was sandwiched by clips. The stretching ratio in the stretching step is shown in Table 1. The width of the stretched film was 2000 mm. Gripping marks of the clips were formed at both ends in the width direction of the stretched film.

[0059] Next, the stretched film was cut by a slitter (cutting device) and separated into two end films and a product film. The width of each of the two end films was 250 mm, and the maximum thickness of the end film was 130 μm. The width of the product film was 1500 mm.

[0060] Next, the end films were wound up by a cylindrical winding member. The line speed of the end film was 350 mm / s. The number of winding times (the number of layers in the end film roll) was 7000. Thereby, the end films were recovered.

[0061] [Example 5] The end films were recovered in the same manner as in Example 1, except that the resin film composed of the PC-based resin obtained in Preparation Example 1 was changed to a resin film composed of the PET obtained in Preparation Example 2.

[0062] [Example 6] The end films were recovered in the same manner as in Example 1, except that the resin film composed of the PC-based resin obtained in Preparation Example 1 was changed to a resin film composed of the acrylic resin obtained in Preparation Example 3.

[0063] [Example 7] An end film was recovered in the same manner as in Example 1, except that the resin film composed of the PC-based resin obtained in Preparation Example 1 was changed to a resin film composed of the COP-based resin obtained in Preparation Example 4.

[0064] [Comparative Example 1] An attempt was made to recover the end film in the same manner as in Example 1, except that the resin film composed of the PC-based resin obtained in Preparation Example 1 was changed to a resin film without a thick portion obtained in Preparation Example 5. In the stretching step, the resin film was clamped with clips without folding back the end portions in the width direction of the resin film.

[0065] [Table 1]

[0066] [Evaluation] As is clear from Table 1, when the clip grips the thick portion and the resin film is stretched, and then the obtained stretched film is separated into an end film including the gripping mark of the clip and a product film, it can be seen that breakage of the end film can be suppressed. [Industrial Applicability]

[0067] The method for manufacturing an end film of the present invention can manufacture an end film that can be reused as a raw material for various industrial products. The end film is particularly preferably used as a recycled resin raw material for optical films. [Explanation of Signs]

[0068] 1 Resin film 2 Stretched film 22 Gripping mark of clip 3 End film 4 Product film 6 Take-up member

Claims

1. A stretching step of preparing a stretched film by stretching a long resin film in a direction intersecting the longitudinal direction while gripping both end portions in the width direction of the long resin film with clips; A cutting step of cutting both end portions including the gripping marks of the clips from the stretched film to separate the end film including the gripping marks and the product film; In the resin film to be subjected to the stretching step, both end portions in the width direction are each configured as a thick portion, and a portion located between the two thick portions is configured as a thin portion; In the stretching step, the thick portion is gripped by the clip; The resin film includes: A film body having a substantially uniform thickness; and An adhesive film attached to an end portion in the width direction of the film body, the adhesive film being made of the same material as the film body; The thick portion includes the film body and the adhesive film; The difference between the thickness of the thick portion and the thickness of the thin portion is 20 μm or more and 30 μm or less; A method for manufacturing an end film, wherein the width of the end film is 1.0% or more and 30% or less when the width of the stretched film is 100%.

2. The method for manufacturing an end film according to claim 1, wherein the thickness of the thick portion is 90 μm or more.

3. The method for manufacturing an end film according to claim 1 or 2, further including a step of winding the end film with a winding member.

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