JP7657248B2 - Manufacturing method of edge film - Google Patents

Description

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

Stretched films, which are widely used in various industrial products, are manufactured by stretching a resin film. For example, a method for manufacturing a stretched film has been proposed in which a long resin film is stretched in a direction intersecting the long direction while both ends in the width direction of the film are held by clips (see, for example, Patent Document 1). In such a method for manufacturing a stretched film, clip marks are left on both ends in the width direction of the stretched film. Therefore, the ends including the marks are generally cut off from the stretched film and discarded.
In recent years, from the viewpoint of reducing the environmental load, it is desired to reuse waste generated during the manufacture of various industrial products. Therefore, in the method for manufacturing a stretched film described in Patent Document 1, it has been considered to recover the end portion cut from the stretched film as an end film and to use it effectively. However, when recovering the end film, the end film may break, making it difficult to recover the end film smoothly.

Patent No. 7096940

The present invention was made to solve the above-mentioned problems of the conventional art, and its main objective is to provide a method for manufacturing end films that can smoothly produce end films that are less likely to break.

[1] A method for producing an end film according to an embodiment of the present invention includes the steps of: preparing a stretched film by stretching a long resin film in a direction intersecting the long length direction while holding each of both widthwise ends of the film with a clip; attaching a reinforcing tape extending in the long length direction of the stretched film to the inside of the clip marks in the width direction of the stretched film; and forming a cutting line extending in the long length direction of the stretched film on the inside of the reinforcing tape in the width direction of the stretched film to obtain an end film including the grip marks and the reinforcing tape.
[2] The method for producing an end film described in [1] above may further include a step of winding up the end film by a winding member.

According to an embodiment of the present invention, it is possible to smoothly manufacture end films that are less likely to break.

FIG. 1 is a schematic diagram for explaining a method for manufacturing an edge film according to one embodiment of the present invention. FIG. 2 is a plan view of the stretched film of FIG.

The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. In addition, in order to make the description clearer, the drawings may show the width, thickness, shape, etc. of each part more diagrammatically than the embodiments, but these are merely examples and do not limit the interpretation of the present invention.

(Definition of terms and symbols)
The definitions of terms and symbols used in this specification are as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular 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 phase difference (Re)
"Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Angles When angles are referred to in this specification, unless otherwise specified, the angles include angles in both clockwise and counterclockwise directions.

A. Overview of the Method for Producing an Edge Film FIG. 1 is a schematic diagram for explaining a method for producing an edge film according to one embodiment of the present invention; FIG. 2 is a plan view of the stretched film of FIG.

The manufacturing method of the end film according to the embodiment of the present invention includes a stretching step, a bonding step, and a cutting step in this order (see FIG. 1). In the stretching step, the resin film 1 is stretched in a direction intersecting the longitudinal direction while each of both ends in the width direction of the long resin film 1 is held by a clip, to prepare a stretched film 2. In the bonding step, a reinforcing tape 5 extending in the longitudinal direction of the stretched film 2 is bonded to the inside of the clip gripping mark 22 in the width direction of the stretched film 2 (see FIG. 2). In the cutting step, a cutting line 21 extending in the longitudinal direction of the stretched film 2 is formed on the inside of the reinforcing tape 5 in the width direction of the stretched film 2, to obtain an end film 3 including the clip gripping mark 22 and the reinforcing tape 5.
The inventors have found that when recovering (manufacturing) an end film, the gripping marks of the clip become the starting point of cracks, causing breakage of the end film. As a result of intensively studying the means for recovering the end film, the inventors have found that if a reinforcing tape is attached to a predetermined position of a stretched film and then the stretched film is cut to obtain an end film, breakage of the end film can be suppressed even if cracks occur in the gripping marks of the clip. Specifically, after a reinforcing tape 5 is attached to the inside of the gripping marks 22 of the clip in the width direction of the stretched film 2, a cutting line 21 is formed on the inside of the reinforcing tape 5 in the width direction of the stretched film 2 to obtain an end film 3. In such an end film 3, even if a crack occurs in the gripping marks 22 of the clip, the reinforcing tape 5 can suppress the progression of the cracks. Therefore, an end film 3 in which breakage is suppressed can be smoothly manufactured (recovered). In other words, the manufacturing method of an end film according to an embodiment of the present invention is a method for recovering an end film.

In one embodiment, the method for manufacturing the end film further includes a first winding step in which the first winding member 7 winds up the end film 3. As described above, the end film 3 is reinforced by the reinforcing tape 5, so that the end film 3 can be wound up without breaking. This allows the end film 3 to be smoothly collected in a roll, and the end film roll 100 in which the end film 3 is wound in a roll can be smoothly manufactured. In the end film roll 100, the end film 3 is layered in the radial direction of the first winding member 7.

The recovered end films are independently distributable products that can be used industrially, and are typically used as recycled resin raw materials.
The recycled resin raw material can be used to manufacture any suitable resin product. Examples of the resin product include optical films such as retardation films; packaging materials made of thermoplastic resins such as polyethylene terephthalate (PET) and nylon; and the like. Among these resin products, optical films are preferred, and retardation films are more preferred. In other words, the recovered end film can be suitably used as a raw material for optical films (typically retardation films).
The end film may be used as a recycled resin raw material with the reinforcing tape attached thereto, or may be used as a recycled resin raw material after the reinforcing tape has been peeled off.

Below, we will explain each step of the end film manufacturing method in detail.

B. Stretching Step As shown in FIG. 1, in the stretching step, a long resin film 1 is stretched, typically by a stretching device 9.

B-1. Resin film to be stretched In this specification, the resin film 1 refers to a film before the stretching process. Any appropriate film may be adopted as the resin film 1. As described above, the resin film 1 has a long shape. Any appropriate value may be adopted as the dimension in each direction of the resin film 1. The width of the resin film 1 (the dimension in the direction perpendicular 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. The thickness of the resin film 1 is, for example, 40 μm or more, preferably 60 μm or more, and, for example, 200 μm or less, preferably 180 μm or less.

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

Among the resin materials constituting the resin film 1, polycarbonate (PC)-based resins, cycloolefin (COP)-based resins, (meth)acrylic-based resins, and polyester-based resins (typically polyethylene terephthalate (PET)) are preferred, and PC-based resins are more preferred. When such resin materials are used, the end film can be more stably recovered in the first winding process.

Examples of PC-based resins include PC-based resins that contain structural units derived from dihydroxy compounds. 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, and 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-cyclohexyl phenyl)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 units derived from the dihydroxy compounds, the PC resin may contain structural units derived from dihydroxy compounds such as isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexane dimethanol (CHDM), tricyclodecane dimethanol (TCDDM), and bisphenols.

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

B-2. Stretching Device In one embodiment, the resin film 1 is transported in the longitudinal direction so as to pass through a stretching device 9. Therefore, the resin film 1 can be stretched while being transported, and the stretched film 2 can be continuously prepared.

Although not shown, the stretching device 9 is equipped with clips capable of gripping the widthwise ends of the resin film 1. The stretching device 9 is typically a tenter stretching device. The stretching device 9 stretches the resin film 1 in a direction intersecting with the longitudinal direction while each of the widthwise ends of the resin film 1 is gripped (typically clamped) by a clip. The stretching direction may be a direction substantially perpendicular 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.

Details of the stretching process are described, for example, in Japanese Patent No. 7096940, Japanese Unexamined Patent Publication No. 2004-226686, and International Publication No. 2007/111313. The descriptions in these patent documents are incorporated herein by reference.

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

Clip marks 22 are formed on both ends of the stretched film 2 in the width direction. The clip marks 22 are harder and more brittle than the rest of the stretched film 2.

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. Typically, the axis misalignment is not substantially manifested in the width direction center of the stretched film 2, and becomes larger as it approaches the width direction ends. In the stretched film 2 shown in the figure, the slow axis is substantially parallel to the stretching direction described above at the width direction center (for example, the axis misalignment is less than 0°±1°). In addition, at the width direction ends of the stretched film 2, the slow axis may cross the stretching direction described above (for example, the axis misalignment is 1° to 3°).

C. Bonding Step As shown in FIG. 1, in one embodiment, a long reinforcing tape 5 is continuously bonded to a stretched film 2 transported in the longitudinal direction. In the illustrated example, the long reinforcing tape 5 is configured as a reinforcing film roll 102 wound in a roll shape, and is pulled out from the reinforcing film roll 102 and bonded to the stretched film 2. The stretched film 2 is preferably subjected to the bonding step after the stretching step (typically immediately after the stretching step) without being subjected to other steps. More specifically, the stretched film 2 is subjected to the bonding step without coming into contact with a roller member such as a transport roller.

Although not shown, the reinforcing tape 5 includes a base material and an adhesive layer.
The material constituting the substrate may be any suitable resin material. For example, the resin material may be the same as the resin material constituting the resin film 1 described above, preferably a polyester resin, more preferably PET. The resin material of the substrate may be used alone or in combination. The substrate of the reinforcing tape 5 may be made of the same resin material as the resin film 1, or may be made of a different resin material from the resin film 1.
The thickness of the substrate is, for example, 20 μm or more, preferably 30 μm or more, more preferably 50 μm or more, and is, for example, 150 μm or less, preferably 100 μm or less.

The reinforcing tape 5 is attached to the stretched film 2 by an adhesive layer. The adhesive layer may be an adhesive layer or a pressure-sensitive adhesive layer. In one embodiment, the adhesive layer is a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is composed of a pressure-sensitive adhesive. Any appropriate pressure-sensitive adhesive may be adopted. Examples of pressure-sensitive adhesives include acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, urethane pressure-sensitive adhesives, epoxy pressure-sensitive adhesives, and polyether pressure-sensitive adhesives. The pressure-sensitive adhesives may be used alone or in combination.
The adhesive layer has a thickness of, for example, 5 μm or more, preferably 10 μm or more, and for example, 40 μm or less, preferably 30 μm or less.

The peel strength of the reinforcing tape 5 (peel angle 90°) is, for example, 2.4 mN/mm or more, preferably 20 mN/mm or more, and for example, 320 mN/mm or less, preferably 250 mN/mm. The peel strength of the reinforcing tape can be measured by peel strength measurement using an autograph. If the peel strength of the reinforcing tape is equal to or greater than the lower limit, peeling of the reinforcing tape from the stretched film can be suppressed in the cutting step and/or the first winding step. If the peel strength of the reinforcing tape is equal to or less than the upper limit, the reinforcing tape can be peeled from the recovered end film as necessary.

As shown in FIG. 2, when the width of the stretched film 2 is taken as 100%, the width of the reinforcing tape 5 is, for example, 0.5% or more, preferably 1.5% or more, and, for example, 5.0% or less, preferably 3.0% or less. The width of the reinforcing tape 5 is, for example, 15 mm or more, preferably 30 mm or more, and, for example, 100 mm or less, preferably 60 mm or less. If the width of the reinforcing tape is within the above range, breakage of the end film can be more stably suppressed.

As described above, the reinforcing tape 5 is attached to the inside of the gripping mark 22 of the clip in the width direction of the stretched film 2. Typically, each of the two reinforcing tapes 5 is attached to the stretched film 2 so as to be adjacent to the gripping mark 22 of the corresponding clip, and extends over the entire longitudinal direction of the stretched film 2. The reinforcing tape 5 may be adjacent to the gripping mark 22 of the clip in the width direction of the stretched film 2, or may be positioned at a distance from the gripping mark 22 of the clip.
The distance between the reinforcing tape 5 and the gripping mark 22 of the clip in the width direction of the stretched film 2 is, for example, 0 mm or more, preferably 20 mm or more, and for example, 100 mm or less, preferably 80 mm or less. If the distance between the reinforcing tape and the gripping mark of the clip is equal to or more than the above-mentioned lower limit, the reinforcing tape can be smoothly applied without overlapping with the gripping mark of the clip, and breakage of the end film can be stably suppressed. If the distance between the reinforcing tape and the gripping mark of the clip is equal to or less than the above-mentioned upper limit, the yield of the product film described later can be improved.

D. Cutting Step As shown in Fig. 1, in the cutting step, both ends including the reinforcing tape 5 and the grip marks 22 of the clip are cut from the stretched film 2 to which the reinforcing tape 5 has been attached, typically by a cutting device 6. In one embodiment, the stretched film 2 is transported in the longitudinal direction so as to pass through the cutting device 6. This allows the stretched film 2 to be cut continuously.

The cutting device 6 may have any suitable configuration. In the illustrated example, the cutting device 6 includes a gear cutter 61 and an opposing roller 62. The gear cutter 61 and the opposing roller 62 face each other. Each of the gear cutter 61 and the opposing roller 62 is rotatable. The gear cutter 61 can form a cutting line 21 in the stretched film 2 passing between the gear cutter 61 and the opposing roller 62 (see FIG. 2).

As shown in FIG. 2, the cutting device 6 typically forms two cutting lines 21 in 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 distance from each other in the width direction of the stretched film 2.

As described above, each of the two cutting lines 21 is formed on the inside of the reinforcing tape 5 in the width direction of the stretched film 2. In other words, the cutting line 21 is located on the opposite side of the clip gripping mark 22 from the reinforcing tape 5 in the width direction of the stretched film 2. The cutting line 21 may be adjacent to the reinforcing tape 5 in the width direction of the stretched film 2, or may be located at a distance from the reinforcing tape 5.

The distance between the cutting line 21 and the reinforcing tape 5 in the width direction of the stretched film 2 is, for example, 0 mm or more, preferably 50 mm or more, more preferably 100 mm or more, and even more preferably 200 mm or more, and is, for example, 500 mm or less, preferably 400 mm or less, and even more preferably 300 mm or less. If the distance between the cutting line and the reinforcing tape is equal to or greater than the above-mentioned lower limit, the cutting line can be formed smoothly. If the distance between the cutting line and the reinforcing tape is equal to or less than the above-mentioned upper limit, the part of the stretched film where the axial misalignment is relatively large as described above can be included in the end film.

In one embodiment, in the width direction of the stretched film 2, the distance between the cutting line 21 and the reinforcing tape 5 is larger than the distance between the reinforcing tape 5 and the grip mark 22 of the clip. In the width direction of the stretched film 2, the distance between the cutting line 21 and the reinforcing tape 5 is, for example, 1 time or more, preferably 5 times or more, more preferably 8 times or more, and is, for example, 20 times or less, preferably 15 times or less, the distance between the reinforcing tape 5 and the grip mark 22 of the clip.
If the distance between the cutting line and the reinforcing tape is equal to or greater than the lower limit of the distance between the reinforcing tape and the gripping mark, the portion of the stretched film having the relatively large axial misalignment can be stably included in the end film. If the distance between the cutting line and the reinforcing tape is equal to or less than the upper limit of the distance between the reinforcing tape and the gripping mark, the yield of the product film can be stably improved.

Through the above steps, two end films 3 corresponding to both ends in the width direction of the stretched film 2 are obtained from the stretched film 2. Each of the two end films 3 is a film body originating from the end in the width direction of the stretched film 2, and includes a film body including a gripping mark 22 of the clip; and a reinforcing tape 5 attached to the film body. Furthermore, the stretched film 2 from which the two end films 3 have been cut is configured as a product film 4. That is, in the cutting process, the stretched film 2 is typically separated into two end films 3 and the product film 4. Each of the two end films 3 and the product film 4 has an elongated shape.

Any appropriate value may be adopted for the width of the end film 3. When the width of the stretched film 2 is taken as 100%, the width of the end film 3 is, for example, 3.0% or more, preferably 5.0% or more, 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 3 is, for example, 60 mm or more, preferably 100 mm or more, 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 lower limit, the end film can more stably contain the portion of the stretched film having the relatively large axial misalignment, thereby reducing the axial misalignment in the product film. When the width of the end film is equal to or less than the upper limit, the yield of the product film can be further improved.

When the width of the end film 3 is 100%, the width of the reinforcing tape 5 is, for example, 1.0% or more, preferably 5.0% or more, more preferably 10% or more, and for example, 50% or less, preferably 30% or less.
The area ratio of the grip marks 22 of the clips in the end film 3 is, for example, 0.5% or more, preferably 1.0% or more, and, for example, 10% or less, preferably 8% or less.
When the width of the reinforcing tape and/or the area proportion occupied by the gripping mark are within the above range, even if a crack occurs at the gripping mark of the clip, the crack can be prevented from progressing further than the reinforcing tape, and the end film can be stably prevented from breaking.

E. First Winding Step As shown in FIG. 1, in the first winding step, the first winding member 7 winds up the end film 3 cut from the stretched film 2 by the cutting device 6. This allows the end film 3 to be continuously collected, and the end film roll 100 can be manufactured. The first winding member 7 is typically rotatable about an axis line substantially parallel to the width direction of the end film 3. Note that, for convenience, one first winding member 7 is illustrated in FIG. 1, but in reality, the same number of first winding members 7 (i.e., two) as the number of end films 3 are provided. The first winding member 7 may have any appropriate configuration. The first winding member 7 typically has a cylindrical shape.

The conveying speed (line speed) of the end film 3 from the cutting device 6 toward the first winding member 7 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 in 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.

F. Second Winding Step The product film 4 obtained in the cutting step is collected by any suitable means. In one embodiment, the end film manufacturing method further includes a second winding step in which the second winding member 8 winds up the product film 4. In the second winding step, the product film 4 is wound around the second winding member 8 and collected. This makes it possible to manufacture a product film roll 101 in which the product film 4 is wound in a roll shape. In the product film roll 101, the product film 4 is layered in the radial direction of the second winding member 8. The second winding member 8 can be described in the same manner as the first winding member 7.

The product film 4 is typically configured as a retardation film having a slow axis. The refractive index of the product film 4 satisfies the relationship 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.

The wavelength dependence of the product film 4 is not particularly limited. The product film 4 preferably exhibits wavelength dependence of reverse dispersion. The 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. The 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.

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) to 50×10 ⁻¹² (m ² /N).

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows. Note that "parts" and "%" in the examples and comparative examples are based on mass unless otherwise specified.

<<Preparation of Stretched Film>>
<Preparation Example 1>
In the same manner as in Production Example 9 of JP 2022-150732 A, a resin film made of a PC resin was prepared, and the resin film was stretched to prepare a stretched film made of a PC resin. The width of the stretched film was 2000 mm. The thickness of the stretched film was 48 μm. A clip grip mark was formed on each of both ends in the width direction of the stretched film.

<Preparation Example 2>
A stretched film made of PET was prepared in the same manner as in Production Example 9 of JP-A-2022-150732, except that the resin film made of PC resin was changed to a resin film made of PET (manufactured by Toray Industries, Inc., product number "50U48"). The width of the stretched film was 2000 mm. The thickness of the stretched film was 50 μm. A clip grip mark was formed on each of both ends in the width direction of the stretched film.

<Preparation Example 3>
A stretched film made of an acrylic resin was prepared in the same manner as in Production Example 9 of JP-A-2022-150732, except that the resin film made of a PC resin was changed to a resin film made of an acrylic resin (manufactured by Kaneka Corporation, product name "HTX-Z"). The width of the stretched film was 2000 mm. The thickness of the stretched film was 40 μm. A clip grip mark was formed on each of both ends in the width direction of the stretched film.

<Preparation Example 4>
A stretched film made of a COP resin was prepared in the same manner as in Production Example 9 of JP-A-2022-150732, except that the resin film made of a PC resin was changed to a resin film made of a COP resin (manufactured by Zeon Corporation, product number "ZF16"). The width of the stretched film was 2000 mm. The thickness of the stretched film was 40 μm. A clip grip mark was formed on each of both ends in the width direction of the stretched film.

[Example 1]
A long reinforcing tape was attached to the inside of the gripping mark of the clip in the width direction of the stretched film made of PC resin obtained in Preparation Example 1. The reinforcing film had a base material made of PET and an adhesive layer made of an acrylic monomer. The thickness of the base material was 38 μm, and the thickness of the adhesive layer was 15 μm. The width of the reinforcing tape was 50 mm (2.5% when the width of the stretched film is 100%). In addition, the distance between the gripping mark of the clip and the reinforcing tape in the width direction of the stretched film was 20 mm.

Next, a cut line was formed on the inside of the stretched film with the reinforcing tape attached using a slitter (cutting device). The distance between the cut line and the reinforcing tape in the width direction of the stretched film was 220 mm (11 times the distance between the reinforcing tape and the gripping mark of the clip). This separated the stretched film into two end films and a product film. The width of each of the two end films was 250 mm (12.5% when the width of the stretched film is taken as 100%). The width of the product film was 1500 mm.

The end film was then wound up by a cylindrical winding member. The line speed of the end film was 350 mm/s. The number of windings (number of layers in the end film roll) was 7,000. In this way, the end film was collected. When the collected end film was visually observed, it was found that the end film was not broken.

[Example 2]
The end film was recovered in the same manner as in Example 1, except that the stretched film made of the PC resin obtained in Preparation Example 1 was changed to the stretched film made of the PET obtained in Preparation Example 2. When the recovered end film was visually observed, the end film was not broken.

[Example 3]
An end film was recovered in the same manner as in Example 1, except that the stretched film made of the PC resin obtained in Preparation Example 1 was changed to the stretched film made of the acrylic resin obtained in Preparation Example 3. When the recovered end film was visually observed, the end film was not broken.

[Example 4]
An end film was recovered in the same manner as in Example 1, except that the stretched film made of the PC resin obtained in Preparation Example 1 was changed to a stretched film made of the COP resin obtained in Preparation Example 4. When the recovered end film was visually observed, the end film was not broken.

[Comparative Example 1]
The stretched film made of the PC resin obtained in Preparation Example 1 was cut by a slitter (cutting device) without attaching a reinforcing tape to separate it 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.

Next, an attempt was made to wind up the end film using a cylindrical winding member. However, the end film broke, making winding difficult. The line speed for the end film was 350 mm/s.

[evaluation]
It is found that when a reinforcing tape is attached to a stretched film and then a cutting line is formed to obtain an end film, breakage of the end film can be suppressed. In particular, it is confirmed that the end film can be wound up without breaking.

The end film manufacturing method of the present invention can produce end film rolls that can be reused as raw materials for various industrial products. The end film recovered as end film rolls is particularly suitable for use as recycled resin raw materials for optical films.

REFERENCE SIGNS LIST 1 resin film 2 stretched film 21 cutting line 22 clip grip mark 3 end film 5 reinforcing tape 7 winding member

Claims (2)

a stretching step of stretching a long resin film in a direction intersecting with a longitudinal direction while holding both ends of the long resin film in a width direction with clips to prepare a stretched film;
a sticking step of sticking a reinforcing tape extending in a longitudinal direction of the stretched film to an inner side of a gripping mark of the clip in a width direction of the stretched film;
A cutting process for forming a cutting line extending in the longitudinal direction of the stretched film on the inner side of the reinforcement tape in the width direction of the stretched film to obtain an end film including the gripping mark and the reinforcement tape ,
A method for manufacturing an end film , wherein in the cutting step, a distance between the cutting line and the reinforcing tape is 50 mm or more . The method for manufacturing an edge film according to claim 1 , further comprising the step of winding up the edge film with a winding member.

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