Method for removing coating layer

Abstract

A method for removing a coating layer is provided, the method comprising: a step for preparing a release film (50) comprising, for example, a substrate film and a coating layer; a step for introducing the release film (50) into a pressure vessel (400) (one example of a treatment vessel); a step for exposing the release film (50) to water vapor (V2, V3) inside the pressure vessel (400); and a step for removing the coating layer from the release film (50). The coating layer includes an interlayer and a releasant layer, the interlayer being interposed between the substate film and the releasant layer.

Description

Coating layer removal method

[0001] The present invention relates to a method for removing a coating layer.

[0002] In recent years, from the viewpoint of global resource conservation, environmental protection, etc., there has been an active movement in various fields to build a recycling-oriented society through efforts to reduce waste generation, reuse, recycle, etc. For example, Patent Document 1 discloses a method for removing a coating on a resin substrate, which comprises a coating removal step of placing a resin substrate having a coating on its surface in a cleaning container, and stirring the resin substrate together with an alkaline aqueous solution in an amount such that the liquid level is higher than the top of the resin substrate deposited in the cleaning container at 80 to 180°C and at a rotation speed of the tip of a stirring blade of 2 to 100 m / sec.

[0003] Japanese Patent Application Laid-Open No. 2004-027072

[0004] The method described in Patent Document 1 is a technique for removing a coating from a substrate by immersing the resin substrate coating in an alkaline aqueous solution. Therefore, the used alkaline aqueous solution contains components of the coating (e.g., a release agent), and reuse of the alkaline aqueous solution results in a reduced cleaning ability. Purifying the alkaline aqueous solution also requires a lot of effort. In a technique for removing a coating from a substrate using a solvent, a solvent that is less susceptible to contamination and easier to reuse is desirable. Furthermore, release films consisting of a substrate film and a coating (coating layer) require different levels of adhesion between the substrate film and the coating layer. Therefore, depending on the release film, it may be difficult to maintain the adhesion between the substrate film and the coating layer, which is required for product quality.

[0005] An object of the present invention is to provide a method for removing a coating layer, which allows the coating layer to be easily removed from a release film.

[0006] [1] A method for removing a coating layer, comprising the steps of: preparing a release film having a base film and a coating layer; placing the release film in a treatment container; exposing the release film to water vapor in the treatment container; and removing the coating layer from the release film, wherein the coating layer includes an intermediate layer and a release agent layer, and the intermediate layer is disposed between the base film and the release agent layer.

[0007] [2] The method for removing a coating layer according to [1], wherein the preparing step is a step of preparing a laminate in which one release film is stacked alone or a laminate in which multiple release films are stacked; the storing step is a step of storing the release film in the state of the laminate in the processing vessel; the exposing step is a step of exposing the release film in the state of the laminate to water vapor; and the removing step is a step of releasing the release film from the state of the laminate and then removing the coating layer from the released release film.

[0008] [3] The method for removing a coating layer according to [1] or [2], wherein the storing step is a step of storing the release film and water vapor in the processing container, and the water vapor is either water vapor generated outside the processing container and introduced into the processing container, or water vapor generated from water introduced into the processing container.

[0009] [4] The method for removing a coating layer according to [1] or [2], wherein the storing step is a step of storing the release film and water vapor in a pressure vessel as the processing vessel, and the water vapor is either water vapor generated outside the pressure vessel and introduced into the pressure vessel, or water vapor generated from water introduced into the pressure vessel.

[0010] [5] The method for removing a coating layer according to any one of [1] to [4], wherein the step of exposing the release film to water vapor is carried out without immersing the release film in liquid water.

[0011] [6] The method for removing a coating layer according to any one of [2] to [5], wherein the laminate in which one release film is stacked alone is a roll in which the long release film is wound up, and the removing step is performed by roll-to-roll.

[0012] [7] The method for removing a coating layer according to [6], further comprising the steps of: after the step of exposing to water vapor, making the release film ready to be unwound from the roll; and unwounding the release film from the roll, wherein the removing step is a step of immersing the release film unwound from the roll in cleaning water and then scraping the coating layer off the base film.

[0013] [8] The method for removing a coating layer according to any one of [1] to [7], wherein the release film is a release film with a ceramic green sheet attached, and a ceramic green sheet is attached to the opposite side of the coating layer from the base film.

[0014] According to one aspect of the present invention, a method for removing a coating layer can be provided that allows the coating layer to be easily removed from a release film.

[0015] FIG. 1 is a cross-sectional view of a release film used in the removal method according to the present embodiment. FIG. 2 is a view showing an example of a roll-shaped laminate used in the removal method according to the present embodiment. FIG. 3 is a view showing an example of a folded laminate used in the removal method according to the present embodiment. FIG. 4 is a view showing an example of a sheet-like laminate used in the removal method according to the present embodiment. FIG. 5 is a view showing an example of a storage step and a step of exposing to water vapor according to the present embodiment. FIG. 6 is a view showing another example of a storage step and a step of exposing to water vapor according to the present embodiment. FIG. 7 is a view showing an example of a removal device used in the removal step according to the present embodiment. FIG. 8 is a view showing another example of a removal device used in the removal step according to the present embodiment.

[0016] [First embodiment] (Method for removing a coating layer) The method for removing a coating layer according to this embodiment (hereinafter also referred to as the removal method according to this embodiment) includes the steps of preparing a release film having a base film and a coating layer, placing the release film in a treatment container, exposing the release film to water vapor in the treatment container, and removing the coating layer from the release film. The coating layer includes an intermediate layer and a release agent layer, and the intermediate layer is disposed between the base film and the release agent layer. Hereinafter, the preparing step, the placing step, and the removing step may be referred to as the preparing step, the placing step, and the removing step, respectively.

[0017] The inventors have discovered that exposing a release film to water vapor before the removal step allows water vapor to penetrate the interface between the base film and the intermediate layer, regardless of the form of the release film (e.g., a sheet or a stack), thereby weakening the adhesion between the base film and the coating layer. According to the removal method of this embodiment, the adhesion between the base film and the coating layer is weakened in advance in the water vapor exposure step, and then the coating layer is removed from the release film in the removal step, thereby facilitating the removal of the coating layer. Furthermore, in the water vapor exposure step, the release film does not need to be immersed in liquid water before the removal step; simply placing the release film in a container filled with water vapor allows the coating layer to be removed in the subsequent removal step. This enables mass processing of release films. Furthermore, since the water vapor exposure step does not require the release film to be immersed in liquid water, the amount of water used can be reduced. Furthermore, when a laminate of release films is exposed to water vapor in the step of exposing to water vapor, the energy consumption of the heat source can be reduced compared to when a single release film with its surface exposed (open state) is exposed to water vapor. A laminate of release films refers to a laminate of a single release film or a laminate of multiple release films. Details will be described later.

[0018] (Water for Steam Source) In the present embodiment, the water vapor used in the step of exposing to water vapor is obtained by evaporating water for generating water vapor (hereinafter, sometimes referred to as "water for steam source"). The water for steam source is preferably ordinary water, i.e., industrial water, and may be purified water or distilled water. It may also be water obtained by recycling wastewater used in various industrial production processes, or water obtained by recycling wastewater after use in carrying out the present embodiment. When recycling wastewater, the water may be recycled as appropriate. From the viewpoint of improving work efficiency, the water for steam source may contain, but is preferably free of, additives that impart functionality. Examples of additives include surfactants and water-soluble organic solvents. When the water for steam source contains an additive, the concentration of the active ingredient of the additive in the water for steam source is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, relative to the total amount of the water for steam source. Furthermore, it is preferable that the water for steam source is not water to which an additive has been intentionally added. Furthermore, the water for the steam source is preferably not an alkaline aqueous solution prepared by intentionally adding a basic substance, nor is it preferably an acidic aqueous solution prepared by intentionally adding an acidic substance. Since wastewater may be able to be recycled simply, the water for the steam source may contain a basic substance and an acidic substance as additives. In this case, the pH of the water for the steam source is preferably 5.8 or more and 8.6 or less so as to comply with the uniform effluent standards (other items) based on the Water Pollution Control Act.

[0019] (Release Film) FIG. 1 is a cross-sectional view of a release film used in the removal method of this embodiment. The release film 50 has a base film 51 and a coating layer 52. The coating layer 52 includes an intermediate layer 521 and a release agent layer 522, with the intermediate layer 521 being disposed between the base film 51 and the release agent layer 522. In FIG. 1, a indicates the surface of the intermediate layer 521 facing the base film, b indicates the surface of the intermediate layer 521 facing the release agent layer, d indicates the surface of the release agent layer, and c indicates the surface of the release agent layer 522 facing the intermediate layer. e indicates the surface of the base film. In the release film according to this embodiment, it is preferable that the base film and the intermediate layer are in direct contact. In the case of FIG. 1, the base film 51 and the intermediate layer 521 are in direct contact, and the intermediate layer 521 and the release agent layer 522 are in direct contact.

[0020] The release film 50 may be used in the production of a ceramic green sheet and may be the release film remaining after the ceramic green sheet has been peeled off. Residue from the ceramic green sheet may be attached to the release film. The ceramic green sheet is preferably used in the production of a multilayer ceramic capacitor (MLCC). The release film 50 is a release film with a ceramic green sheet attached, and a ceramic green sheet may be attached to the surface of the coating layer 52 opposite the substrate film 51 (reference symbol d in FIG. 1). FIG. 2A is a diagram of a roll in which a release film 50G with a ceramic green sheet is wound around a winding core 1G. FIG. 2A shows the state in which the release film 50G with a ceramic green sheet has been unwound from the roll. The roll shown in FIG. 2A is an example of a laminate in which a single release film is stacked, and may be referred to as a roll-shaped laminate 504. The roll-shaped laminate 504 will be described in the preparation process section. In FIG. 2A, residue 920 from the ceramic green sheet is attached to the surface of the coating layer 52. After the ceramic green sheet is peeled off, recesses 910 are formed, and the coating layer 52 is exposed from the recesses 910.

[0021] In the release film used in the removal method of this embodiment, the intermediate layer is preferably hydrophilic and water-insoluble. When the intermediate layer is hydrophilic, the coating layer can be more easily removed from the release film. The reason for this is explained with reference to FIG. 1 . The intermediate layer 521 in the release film 50 adheres to the base film 51 mainly through hydrogen bonding and the anchoring effect ( FIG. 1 ). In the water vapor exposure step, if the intermediate layer 521 is hydrophilic, water vapor can more easily penetrate the interface between the base film 51 and the intermediate layer 521, weakening the hydrogen bonding and anchoring effect between the intermediate layer 521 and the base film 51. As a result, when removing the coating layer 52 from the release film 50 in the removal step, the intermediate layer 521, together with the release agent layer 522, is more easily peeled from the base film 51. Furthermore, if the intermediate layer is water-insoluble, dissolution of components of the intermediate layer 521 into cleaning water is suppressed in the coating layer removal step. Therefore, since the intermediate layer 521 is water-insoluble, contamination of the cleaning water can be prevented, making it easier to reuse the water after use. Furthermore, in the removal step of this embodiment, it is preferable to rinse the release film with cleaning water while physically removing the coating layer. Rinsing the release film with cleaning water prevents the removed coating layer from reattaching to the substrate film. The cleaning water used in the removal step of this embodiment is preferably ordinary water, i.e., industrial water, and is preferably water of the same quality as the water used as the steam source described above.

[0022] In the steam exposure step and the removal step of this embodiment, alkaline aqueous solutions with high concentrations of alkaline components are not used as the steam source water and the cleaning water, so there is no need to purify the wastewater used in each step, unlike Patent Document 1. Furthermore, there are few problems when the wastewater is reused as the steam source water and the cleaning water. Moreover, whether the wastewater is discarded or reused, the amount of foreign matter in the wastewater after filtering out the components of the base film and the coating layer is extremely small, which simplifies the purification process and reduces the environmental load.

[0023] In this specification, whether an intermediate layer is "hydrophilic" or not is determined to be hydrophilic if the water contact angle of the surface of the intermediate layer facing the substrate film is 55 degrees or less. In the case of the release film 50 shown in FIG. 1 , if the water contact angle of the surface of the intermediate layer 521 facing the substrate film (symbol a in FIG. 1 ) is 55 degrees or less, the intermediate layer 521 is hydrophilic. From the viewpoint of promoting the separability of the substrate film, the contact angle is preferably 50 degrees or less, more preferably 45 degrees or less. The contact angle is a value obtained by measuring the water contact angle of the surface of the intermediate layer that was in contact with the substrate film (the peeled surface) after separating the substrate film from the release film, i.e., after contacting the intermediate layer with water and peeling the interface between the intermediate layer and the substrate film. Purified water is used as the water that comes into contact with the intermediate layer when measuring the water contact angle.

[0024] Specifically, the intermediate layer is separated from the substrate film by the following method, and the water contact angle of the surface of the intermediate layer facing the substrate film is measured. The obtained value is the water contact angle of the surface of the intermediate layer facing the substrate film. A 50 mm wide adhesive tape (manufactured by Nitto Denko Corporation, product name "Polyester Adhesive Tape No. 31B") is attached to the release agent layer surface of the release film, and then cut to a size of 50 mm x 50 mm to prepare a test piece. 2 L of purified water is placed in a 5 L pressure vessel, and the purified water is boiled to 100 °C using a heater. The test piece (cut to a size of 50 mm x 50 mm) is then immersed in boiling water (purified water) at 100 °C. The lid of the pressure vessel is then closed, and heating is resumed until the pressure inside the pressure vessel reaches 2 atmospheres. Boiling (fume) is confirmed to confirm that the pressure inside the pressure vessel has reached 2 atmospheres, and after 15 minutes have passed (held) in this state, the pressure vessel is returned to normal pressure. Thereafter, it is confirmed that the test piece has been separated into a laminate in which the release agent layer and the intermediate layer are integrally supported on the pressure-sensitive adhesive tape, and the base film in the pressure vessel, and the pressure-sensitive adhesive tape supporting the release agent layer and the intermediate layer is removed from the purified water and dried at room temperature for 24 hours. Thereafter, the water contact angle is measured for the surface of the intermediate layer supported on the pressure-sensitive adhesive tape (the surface of the intermediate layer that was in contact with the surface of the base film).

[0025] In this specification, whether an intermediate layer is "water-insoluble" or not is determined when the difference between the water contact angle of the release agent layer surface (symbol d in Figure 1 ) and the water contact angle of the intermediate layer on the substrate film side (symbol a in Figure 1 ), measured using the following method, is 30 degrees or more. The difference in contact angles is preferably 40 degrees or more, more preferably 50 degrees or more. A small difference indicates that the components constituting the intermediate layer have dissolved in water, resulting in the measurement of a release agent layer that is partially exposed. The water contact angle of the release agent layer surface is not particularly limited, but is usually 80 degrees or more, preferably 85 degrees or more, and more preferably 90 degrees or more. The upper limit of the water contact angle of the release agent layer surface is usually 150 degrees, preferably 140 degrees, and more preferably 130 degrees. The water contact angle of the release agent layer surface is measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DM-701") by the sessile drop method in accordance with JIS R3257: 1999. Distilled water is used as the droplet.

[0026] The water contact angle may be measured by the following method as a simpler method. The test piece (cut into a size of 50 mm x 50 mm) is prepared. Next, 300 mL of purified water is filled into a 500 mL glass beaker, and the entire test piece is immersed in purified water heated to 90°C and left for 3 hours. Thereafter, it is confirmed that the test piece has been separated into a laminate in which the release agent layer and the intermediate layer are integrally supported on the adhesive tape, and the substrate film. The adhesive tape carrying the release agent layer and the intermediate layer is removed from the heated purified water and dried at room temperature for 24 hours. The water contact angle is then measured for the surface of the intermediate layer supported on the adhesive tape (the surface of the intermediate layer that was in contact with the surface of the substrate film). The contact angle is measured by the sessile drop method in accordance with JIS R3257:1999 using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DM-701"). Distilled water is used for the droplet.

[0027] Each step of the removal method according to this embodiment will be described.

[0028] <Preparation Step> The preparation step is a step of preparing a release film having a base film and a coating layer. The preparation step may be a step of simply preparing a plurality of release films, a step of preparing a laminate in which a single release film is laminated, or a step of preparing a laminate in which a plurality of release films are laminated.

[0029] (Roll-shaped laminate, folded laminate) In the preparation step, examples of the laminate in which a single release film is laminated include a roll-shaped product in which a single long release film is wound into a roll and laminated (hereinafter, this may be referred to as a roll-shaped laminate), and a laminate in which a single sheet-shaped release film is folded and laminated (hereinafter, this may be referred to as a folded laminate).

[0030] The roll-shaped laminate is, for example, a roll-shaped product in which a release film is wound around a winding core. The winding core of the roll-shaped laminate is preferably made of a water-resistant material, considering that it will be exposed to water vapor in the water vapor exposure step. The release film constituting the roll-shaped laminate is preferably wound so that a first surface of the coating layer opposite the substrate film (in the case of FIG. 1, the release agent layer surface (symbol d)) and a second surface of the substrate film opposite the coating layer (in the case of FIG. 1, the substrate film surface (symbol e)) face each other directly or indirectly. "Directly facing" means that the first surface of the coating layer faces the second surface of the substrate film without any other material interposed between them. "Indirectly facing" means that the first surface of the coating layer faces the second surface of the substrate film with another material (e.g., a ceramic green sheet) interposed between them (see FIG. 2A).

[0031] FIG. 2A is a diagram showing an example of a roll-shaped laminate. In the roll-shaped laminate 504 shown in FIG. 2A, a ceramic green sheet-attached release film 50G is wound around a winding core 1G. An insertion hole 2G is formed in the center of the winding core 1G. The dimensions of the roll-shaped laminate are, for example, a width (dimension perpendicular to the winding direction) of 100 mm or more and 1000 mm or less, preferably 200 mm or more and 600 mm or less. The winding diameter of the roll-shaped laminate (the diameter of the roll including the winding core) is, for example, 100 mm or more and 1500 mm or less, preferably 150 mm or more and 1000 mm or less.

[0032] The folded laminate is, for example, a laminate in which a single sheet-like release film is folded by any folding method. The folding method is not particularly limited, but examples include a method of folding the folded laminate in a zigzag manner so that the edges of the folded portions are aligned (overlapping at the top and bottom) when viewed in a plane (see FIG. 2B ), and a method of folding in a zigzag manner so that the edges of the folded portions do not overlap at the top and bottom. FIG. 2B is a diagram showing an example of a folded laminate. In the folded laminate 502 shown in FIG. 2B , a single sheet-like release film 50 is folded in a zigzag manner so that the edges of the folded portions are aligned when viewed in a plane.

[0033] For example, when a release film unwound from a normal roll is folded to form a folded laminate, the size of the folded laminate (width x length x thickness (height)) is preferably within the following range. By folding the release film, the folded laminate can be formed into a rectangular parallelepiped block, making it easier to load and transport than a roll-shaped laminate. The width of the folded laminate depends on the width of the roll before unwound, but is usually 100 mm or more and 1000 mm or less, and preferably 200 mm or more and 600 mm or less. The length of the folded laminate is preferably 100 mm or more and 1000 mm or less, and more preferably 200 mm or more and 600 mm or less. The thickness (height) of the folded laminate is preferably 100 mm or more and 1000 mm or less, and more preferably 200 mm or more and 600 mm or less.

[0034] (Layered Sheet) In the preparation process, a layered structure (hereinafter sometimes referred to as a layered sheet) in which multiple release films are stacked in the thickness direction can be exemplified by a layered structure in which multiple release films are stacked in the thickness direction. The shape of the release films is not particularly limited, but examples include rectangular and polygonal shapes. The shape of the release films may also be irregular. The multiple release films may be stacked in the same direction, or the release films may be stacked so that the base films and coating layers face each other between each release film. The release films may be stacked in any direction. "Stacked in the same direction" refers to stacking the release films so that the base films and coating layers face each other between each release film. Figure 2C is a diagram showing an example of a layered sheet. The layered sheet 503 shown in Figure 2C has multiple rectangular release films 50 stacked in the same direction.

[0035] When the release film constituting the sheet stack is rectangular, the dimensions of the release film are, for example, 100 mm or more and 1000 mm or less, preferably 200 mm or more and 600 mm or less, and the thickness (height) of the sheet stack is preferably 100 mm or more and 1000 mm or less, more preferably 200 mm or more and 600 mm or less.

[0036] Hereinafter, the term "layer" will be used to collectively refer to the roll layer, the folded layer, and the sheet layer.

[0037] <Accommodating Step> The accommodating step is a step of accommodating the release film in a container. When the release film is a laminate, the accommodating step is a step of accommodating the release film in the laminated state in a treatment container. The treatment container preferably has a structure that can supply water vapor into the treatment container or a structure that generates water vapor in the treatment container while the release film is accommodated. Examples of the treatment container include a container with a lid and a pressure vessel.

[0038] In this embodiment, the containing step is a step of containing a release film and water vapor in a treatment vessel. The water vapor contained in the treatment vessel is preferably either water vapor generated outside the treatment vessel and introduced into the treatment vessel, or water vapor generated from water (water for water vapor source) introduced into the treatment vessel. From the viewpoint of reducing energy consumption, the water vapor contained in the treatment vessel is preferably water vapor generated from water (water for water vapor source) introduced into the treatment vessel. In this embodiment, the containing step is a step of containing a release film and water vapor in a pressure vessel serving as a treatment vessel. The water vapor contained in the pressure vessel is preferably either water vapor generated outside the pressure vessel and introduced into the pressure vessel, or water vapor generated from water for water vapor source introduced into the pressure vessel. From the viewpoint of reducing energy consumption, the water vapor contained in the pressure vessel is preferably water vapor generated from water for water vapor source introduced into the pressure vessel. The water vapor source contained in the treatment vessel is preferably heated in the containing step to change its state from liquid to water vapor. Examples of means for containing water vapor in the treatment vessel include (1) a means for introducing water vapor generated externally into the treatment vessel, and (2) a means for introducing water vapor source water into the treatment vessel and heating the water vapor source water to generate water vapor in the treatment vessel. Examples of the means (1) include a known water vapor generator (e.g., a boiler) and a water vapor inlet for introducing the water vapor generated by the water vapor generator into the treatment vessel. Examples of the means (2) include water vapor source water introduced into the treatment vessel and known heating means (e.g., a heater) for heating the water vapor source water.

[0039] <Step of Exposing to Water Vapor> The step of exposing to water vapor is a step of exposing the release film to water vapor in a treatment container. When the release film is a laminate, the step of exposing to water vapor is a step of exposing the release film in the laminate state to water vapor.

[0040] Methods for exposing the release film to water vapor include placing the release film in a treatment container filled with water vapor, supplying water vapor into the treatment container while the release film is contained in the treatment container, and heating the water for the water vapor source after containing the release film and water for the water vapor source in the treatment container.

[0041] In the step of exposing the release film to water vapor, from the viewpoint of facilitating penetration of water vapor into the interface between the base film and the intermediate layer and from the viewpoint of suppressing melting of the resin component contained in the release film, the air pressure and temperature within the treatment container in the step of exposing to water vapor are preferably within the following ranges. When the release film is housed in a pressure container, the air pressure within the treatment container in the step of exposing to water vapor is preferably 1.2 atmospheres or more, more preferably 1.4 atmospheres or more. The air pressure within the treatment container is preferably 9.9 atmospheres or less, more preferably 4.7 atmospheres or less. When the release film is housed in a pressure container, the temperature within the treatment container in the step of exposing to water vapor is preferably 105°C or more, more preferably 110°C or more. The temperature within the treatment container is preferably 180°C or less, more preferably 150°C or less.

[0042] In the step of exposing the release film to water vapor, the time for exposing the release film to water vapor is, for example, 5 minutes or more and 60 minutes or less, and preferably 10 minutes or more and 40 minutes or less.

[0043] In the step of exposing the release film to water vapor, the release film may be in its original state (single-leaf release film, roll-like laminate, folded laminate, or single-leaf laminate) (e.g., FIGS. 2A to 2C ), may be housed in a holding container, or may be fixed (held) using a jig. Examples of holding containers include containers with multiple holes and containers with water vapor flow paths. The method of holding the release film using a jig is not particularly limited. For example, in the case of a roll-like laminate, a jig (e.g., adhesive tape or a rubber band) may be used to secure the end of the roll so that it does not unwind; in the case of a folded laminate, a jig may be used to secure the end of the fold; and in the case of a single-leaf laminate, a jig (e.g., clips) may be used to press the laminate from both sides in the stacking direction of the release film.

[0044] In this embodiment, the step of exposing to water vapor is carried out without immersing the release film in liquid water.

[0045] The storing step and the step of exposing to water vapor will be described with reference to specific examples 1 to 3. Note that the storing step and the step of exposing to water vapor are not limited to specific examples 1 to 3.

[0046] Specific Example 1 The accommodation step and the steam exposure step according to Specific Example 1 are carried out using a treatment vessel 60 shown in FIG. 3A. FIG. 3A shows a roll-shaped stack 501 accommodated in the treatment vessel 60 as is. The roll-shaped stack 501 is a roll-shaped object in which a release film 50 is wound around a winding core 5A. An insertion hole 5B is formed in the center of the winding core 5A. The treatment vessel 60 includes a vessel body 62 and a lid 61. A steam inlet 63 for introducing steam V1 and a pressure relief pipe 64 are formed in the upper part of the lid 61. A pressure relief valve 73 for controlling the pressure inside the treatment vessel 60 is disposed in the pressure relief pipe 64. The lid 61 also has a rim 601 formed along the outer periphery.

[0047] The accommodation step and the steam exposure step are performed as follows. First, the rolled laminate 501 is accommodated in the treatment vessel 60. Steam V1 generated by a steam generator (not shown) is introduced into the treatment vessel 60 through the steam inlet 63. This allows the rolled laminate 501 and the steam V1 to be accommodated in the treatment vessel 60 (accommodation step). The rolled laminate 501 is exposed to the steam V1 introduced into the treatment vessel 60 through the steam inlet 63 (steam exposure step). By exposing the rolled laminate 501 to the steam V1, the steam V1 penetrates into the interface between the base film and the intermediate layer from the end of the release film 50 in the surface direction (the position on the side of the roll indicated by reference symbol E4 in FIG. 3A ). This allows the coating layer to be easily removed from the release film in the subsequent removal step. It should be noted that the "end in the surface direction of the release film 50" refers to the position of the roll side indicated by the symbol E1 in the case of the roll-shaped stack 504 in Figure 2A, the position of the side indicated by the symbol E2 in the case of the folded stack 502 in Figure 2B, and the position of the side indicated by the symbol E3 in the case of the sheet stack 503 in Figure 2C.

[0048] The accommodation step and the exposure step to water vapor according to specific examples 2 and 3 are performed using a pressure vessel 400 (an example of a processing vessel) shown in FIG. 3B.

[0049] Specific Example 2 FIG. 3B shows a state in which the roll-shaped stack 501 is held in a basket 407 (an example of a holding container) and housed in a pressure vessel 400. Wheels 407A are provided at the bottom of the basket 407. The pressure vessel 400 comprises an outer casing 402, a pressure vessel body 401 installed in the outer casing 402, and a lid 403 that seals the pressure vessel body 401 and the outer casing 402. A steam inlet pipe 404 and a steam outlet pipe 405 are provided at the top of the pressure vessel 400, and the steam inlet pipe 404 is connected to a boiler 420. Steam adjustment valves 404A and 405A are provided at the steam inlet pipe 404 and the steam outlet pipe 405, respectively. A drain pipe 406 is provided at the bottom of the pressure vessel 400. The drain pipe 406 is configured so that water W3 introduced into the pressure vessel body 401 is discharged from a drain outlet 406B. A drain adjustment valve 406A is disposed in the drain pipe 406. A heater 411 is disposed in the bottom of the pressure vessel 400 to heat the water W3 introduced into the pressure vessel body 401. The location of the heater 411 is not limited to that shown in FIG. 3B . For example, the heater 411 may be disposed inside the outer casing 402 and outside the pressure vessel body 401. The pressure vessel body 401 includes a water stop wall 410 at its bottom and a reservoir 409 for storing the water W3, and a mounting table 408 located higher than the reservoir 409. A basket 407 holding the rolled stack 501 is disposed on the mounting table 408. The mounting table 408 has multiple openings 408A, through which water vapor generated from the water W3 in the reservoir 409 diffuses into the pressure vessel body 401.

[0050] The storing step and the exposing step to water vapor according to Example 2 are carried out as follows. Example 2 describes a case where only water vapor generated from water W3 (water for water vapor source) introduced into the interior of the pressure vessel 400 (storage section 409 in the case of FIG. 3B ) is used as the water vapor used in the storing step and the exposing step to water vapor. First, the roll-shaped stack 501 held in the basket 407 and water W3 are stored in the storage section 409 of the pressure vessel body 401. The water W3 is heated by the heater 411 to generate water vapor V3. The generated water vapor V3 diffuses into the pressure vessel body 401 through the opening 408A of the mounting table 408. As a result, the pressure vessel body 401 is filled with water vapor V3, and the water vapor V3 generated from the water W3 is stored in the pressure vessel body 401 together with the roll-shaped stack 501 (storage step). The rolled laminate 501 is exposed to water vapor V3 without being immersed in water W3 (water vapor exposure step). By exposing the rolled laminate 501 to water vapor V3, the water vapor V3 penetrates into the interface between the base film and the intermediate layer from the end of the release film 50 in the planar direction (position on the side of the roll), and therefore the coating layer can be easily removed from the release film in the subsequent removal step.

[0051] (Specific Example 3) The storing step and the steam exposure step according to Specific Example 3 are carried out as follows. Specific Example 3 describes a case where only steam generated outside the pressure vessel 400 (steam V2 generated in the boiler 420 in the case of FIG. 3B ) is used as the steam used in the storing step and the steam exposure step. While FIG. 3B shows a state in which water W3 capable of generating steam has been introduced into the reservoir 409 of the pressure vessel body 401, in Specific Example 3, water W3 does not need to be introduced. First, the rolled stack 501 held in the basket 407 is stored in the pressure vessel body 401. Steam V2 generated in the boiler 420 is introduced into the pressure vessel body 401 through the steam inlet 404B of the steam inlet pipe 404. As a result, the rolled stack 501 and the steam V2 generated in the boiler 420 are stored in the pressure vessel body 401 (storing step). The roll-shaped laminate 501 is exposed to water vapor V2 (water vapor exposure step). By exposing the roll-shaped laminate 501 to water vapor V2, the water vapor V2 penetrates into the interface between the base film and the intermediate layer from the end of the release film 50 in the planar direction (position on the side surface of the roll), and therefore, in the subsequent removal step, the coating layer can be easily removed from the release film.

[0052] <Releasing Step> When the release film is a laminate, the removal method according to this embodiment includes a releasing step after the step of exposing to water vapor and before the removal step. The releasing step is a step of releasing the release film from the laminate after exposing the laminate to water vapor for a predetermined time. Releasing the release film from the laminate refers to, for example, exposing the coating layer of the release film or the surface of the ceramic green sheet so that it faces the removal means described below (wire brush 34 in the cases of Figures 4 to 6). When the laminate is a roll-shaped laminate, releasing the release film from the laminate is performed by unwinding the release film from the roll-shaped laminate. When the laminate is a folded laminate, releasing the release film from the laminate refers to unfolding the folded laminate to return it to a single sheet-like release film. When the laminate is a sheet-like laminate, releasing the release film from the laminate refers to unfolding the sheet-like laminate to return it to individual individual release films. When the stack is a sheet-like stack and the subsequent removal step involves removing the coating layer with cleaning water contained in a cleaning container, the release step may include cutting the release film of each stack to a predetermined size before placing it in the cleaning container so that it can be easily stirred in the cleaning container. A size that is easy to stir is preferably, for example, a side length of 5 mm or more and 150 mm or less, and more preferably 10 mm or more and 100 mm or less. It is preferable that the surface exposed when the stack is released is not dry. In other words, when the stack is released, it is preferably performed while the stack is maintained in a wet state. This makes it easier to remove the coating layer from the release film.

[0053] Hereinafter, the container used in the removal step may be referred to as a cleaning container.

[0054] <Removing Step> The removing step is a step of removing the coating layer from the release film. When the release film is a laminate, the removing step is a step of releasing the release film from the laminate (releasing step) and then removing the coating layer from the released release film. The removing step is preferably carried out while immersing the release film in washing water. This allows the removed coating layer to be washed off so that it does not re-adhere to the substrate film.

[0055] When the release film is a roll-like laminate (a roll-like material in which a long release film is wound), the removing step is preferably performed by roll-to-roll. When the release film is a roll-like laminate, the removing method according to this embodiment preferably includes, after the step of exposing to water vapor, a step of making the release film ready to be unwound from the roll-like material, and a step of unwounding the release film from the roll-like material. In this case, the removing step is preferably a step of immersing the release film unwound from the roll-like material in cleaning water, and then scraping the coating layer off the substrate film.

[0056] Examples of scraping means include blades and wire brushes. Known components can be used for the blades and wire brushes. The number and location of the scraping means are not particularly limited. Another scraping means includes a high-pressure water stream. The removal step is preferably performed by immersing the release film unwound from the roll-shaped laminate in cleaning water contained in a cleaning container and passing it through a guide roller. The cleaning container is preferably a water tank. The temperature of the cleaning water used in the removal step can be any temperature. Room-temperature cleaning water reduces energy consumption. Furthermore, high-temperature cleaning water can weaken the interfacial bond between the substrate film and the coating layer in the removal step, even if the steam exposure step does not sufficiently weaken the bond, thereby ensuring the removal of the coating layer. When high-temperature cleaning water is used, the temperature of the cleaning water is preferably 40°C or higher, more preferably 60°C or higher. Furthermore, it is preferably less than 100°C, more preferably 98°C or lower. The purpose of the removal step of this embodiment is to prevent the removed coating layer from re-adhering to the substrate film, and therefore the purpose can be achieved with a short immersion time. The immersion time in the cleaning water is usually from 0.01 seconds to 10 minutes, preferably from 0.1 seconds to 5 minutes.

[0057] When the release film is a folded laminate, the removal method according to the present embodiment preferably includes a step of exposing the release film to water vapor and then unwinding the release film from the folded laminate. In this case, the removal step is preferably a step of immersing the release film unwound from the folded laminate in cleaning water and then scraping the coating layer off the base film.

[0058] When the release film is a laminate of individual sheets, the removal method according to this embodiment includes a step of exposing the laminate to water vapor, followed by a step of releasing the laminate of individual sheets and returning them to individual sheets (a release step). In this case, the removal step is preferably a step of stirring the multiple release films together with cleaning water. When the release film is a laminate of multiple release films, the removal step is preferably a step of stirring the multiple release films together with cleaning water. When the release film is a laminate of individual sheets or multiple release films, the removal step may be a step of barrel polishing the released release film together with cleaning water and media (abrasives). By barrel polishing the release film, the coating layer can be efficiently removed from the release film. The removal step is preferably a step of submerging the substrate film separated from the release film in cleaning water and floating the removed coating layer on the cleaning water. After the removal step, the substrate film separated from the coating layer is removed from the cleaning water in the cleaning container and recovered.

[0059] The removal step will be described with reference to specific examples 4 and 5. Note that the removal step is not limited to specific examples 4 and 5.

[0060] (Specific Example 4) The removing step according to specific example 4 is carried out using a roll-to-roll type removing device 100 shown in FIG. 4. The roll-shaped laminate 501 shown in FIG. 3A or 3B is used as the release film. The removing device 100 shown in FIG. 4 includes a feeding means 10, a removing means 30, a winding means 40, and a plurality of guide rollers GR1, GR2, and GR3. The feeding means 10 is a means for feeding out the release film 50 from the roll-shaped laminate 501, and includes a support member 10A that rotatably supports the winding core 5A of the roll-shaped laminate 501. The removing means 30 includes a guide roller GR2 and a wire brush 34 (an example of a scraping means) that scrapes off the coating layer 52 from the base film 51. In the case of FIG. 4, the removing means 30 includes a cleaning container 32. The cleaning container 32 contains cleaning water W2. The wire brush 34 is disposed opposite the guide roller GR2 and is disposed so as to abut against the surface of the release film 50 facing the coating layer 52. The winding means 40 is a means for winding up the base film 51 into a roll after the coating layer 52 has been removed, and includes a support member 40A that engages and supports a winding core 6A for the base film 51. The support member 40A is connected to a drive device (not shown), which rotates the winding core 6A together with the support member 40A, allowing the release film 50 and base film 51 to travel from the feeding means 10 to the winding means 40.

[0061] The accommodation step and the steam exposure step before the removal step may be performed, for example, using a treatment vessel 60 shown in FIG. 3A as in Specific Example 1, or may be performed using a pressure vessel 400 shown in FIG. 3B as in Specific Example 2 or Specific Example 3. After the steam exposure step, the roll-shaped laminate 501 is removed from the treatment vessel 60 or the pressure vessel 400, and the winding core 5A of the roll-shaped laminate 501 is attached to a support member 10A of the unwinding means 10, thereby enabling the release film 50 to be unwound from the roll-shaped laminate 501. The release film 50 unwound from the roll-shaped laminate 501 by the unwinding means 10 is wound around a guide roller GR1 and then immersed in cleaning water W2 in a cleaning vessel 32. Thereafter, when the release film 50 is wound around a guide roller GR2 provided in the cleaning water W2, the coating layer 52 is scraped off from the substrate film 51 by a wire brush 34 provided opposite the guide roller GR2 (scraping step). This removes the coating layer 52 from the release film 50. After the removal step, the substrate film 51 separated from the coating layer is taken out of the cleaning container 32 and separated from the removed coating layer in cleaning water W2. The substrate film 51 is then wound around a guide roller GR3 and wound into a roll by winding means 40 for recovery.

[0062] [Specific Example 5] The removal step according to specific example 5 is carried out using a removal device 100B shown in Figure 5. Instead of the roll-shaped laminate 501 used in specific example 4, a folded laminate 502A shown in Figure 5 is used as the release film. The removal device 100B shown in Figure 5 includes a folded laminate payout means 11A, a removal means 30A, a folding and collecting means 41A, and a plurality of guide rollers GR2, GR4, and GR5. The folded laminate payout means 11A pays out the release film 50 from the end of the folded laminate 502A (the end or beginning of the folding of the release film 50). The folding and collecting means 41A automatically folds the base film 51 from which the coating layer has been removed along the folds of the original folded laminate 502A. The folded stack feeding means 11A and the folding and collecting means 41A can both be publicly known means.

[0063] The storing step and the exposing step to water vapor before the removing step may be performed using the treatment vessel 60 shown in FIG. 3A as in Example 1, or may be performed using the pressure vessel 400 shown in FIG. 3B as in Example 2 or Example 3, except that the folded laminate 502A is used instead of the roll-shaped laminate 501. After the exposing step to water vapor, the folded laminate 502A is removed from the treatment vessel 60 or the pressure vessel 400 and loaded into the folded laminate payout means 11A. The release film 50 constituting the folded laminate 502A is paid out by the folded laminate payout means 11A, passes through a plurality of guide rollers GR4 and GR5, and is then immersed in cleaning water W2 as in Example 4. Thereafter, as the substrate film 51 is wound around a guide roller GR2 provided in the cleaning water W2, the coating layer 52 is scraped off from the substrate film 51 by a wire brush 34 provided opposite the guide roller GR2 (scraping step). After the coating layer has been removed, the substrate film 51 is wound around a plurality of guide rollers GR4 and GR5, and then folded and collected by folding and collecting means 41A. The substrate film 51 may be wound and collected by a known winding means instead of the folding and collecting means 41A.

[0064] [Modifications of the Embodiments] The present invention is not limited to the above-described embodiments, and can include modifications and improvements within the scope of achieving the object of the present invention.

[0065] [Variation 1] Instead of the pressure vessel 400 shown in FIG. 3B, the containing step and the steam exposure step may be performed using a pressure vessel 60A shown in FIG. 3C. FIG. 3C shows a state in which a rolled stack 501 is contained in the pressure vessel 60A together with water W1 (water for steam source). A mounting table 66, which is higher than the depth of the water W1, is installed inside the pressure vessel 60A, and the rolled stack 501 is placed on the mounting table 66. The pressure vessel 60A includes a pressure vessel body 62A and a pressure lid 61A. The pressure lid 61A has a rim 601A formed along its outer periphery. A pressure control unit 70 is disposed above the pressure lid 61A. The pressure control unit 70 controls the air pressure inside the pressure vessel 60A to a first air pressure higher than 1 atmosphere. The pressure control unit 70 may be, for example, a pressure control valve (e.g., a safety valve), a pressure control valve (e.g., a relief valve), or a pressure regulating valve (e.g., a weight-type or spring-type) used in a typical pressure cooker. In the example shown in FIG. 3C , the pressure control unit 70 includes a relief valve 71 and a pressure sensor 72. The relief valve 71 adjusts the internal pressure of the pressure vessel 60A to a predetermined pressure by controlling the opening area of ​​a steam outlet 71A formed in the pressure lid 61A. The opening area of ​​the steam outlet 71A is controlled by a computer control unit in accordance with the pressure value acquired by the pressure sensor 72. Control of the internal pressure of the pressure vessel 60A is not limited to this. A heater 68 for heating the water W1 is disposed below the pressure vessel body 62A. When the pressure vessel 60A is used, the containing process and the steam exposure process are performed as follows. First, the roll-shaped stack 501 is placed on the mounting table 66 installed in the pressure vessel 60A, and water W1 is placed in the bottom of the pressure vessel 60A. The water W1 in the pressure vessel 60A is heated by the heater 68, and the pressure inside the pressure vessel 60A is increased to a pressure higher than 1 atmosphere, thereby generating water vapor inside the pressure vessel 60A and filling the pressure vessel 60A with water vapor (placing step). The roll-shaped stack 501 placed on the mounting table 66 is exposed to water vapor (not shown) without being immersed in the water W1 (exposing to water vapor step).When the rolled laminate 501 is exposed to water vapor, water vapor penetrates into the interface between the base film and the intermediate layer from the end of the release film 50 in the planar direction (the position on the side of the roll indicated by symbol E4 in Figure 3C), making it possible to easily remove the coating layer from the release film in the subsequent removal process.

[0066] (Variation 2) The removal step may be performed using a removal device 100A shown in Figure 6 instead of the removal device 100 shown in Figure 4. The removal device 100A shown in Figure 6 has the same configuration as the removal device 100 shown in Figure 4, except that it includes a circulation means 300. The circulation means 300 is a means for returning cleaning water W2 to the cleaning container 32 after filtering it with a filter 35. The circulation means 300 includes a drain outlet 32A provided in the cleaning container 32, a filter 35 that filters the cleaning water W2, a storage section 36 that stores the filtered cleaning water W2, an inlet 38 provided at the opening of the cleaning container 32, and a circulation path 37 that connects the bottom drain outlet 36A of the storage section 36 and the inlet 38.

[0067] 6 , the coating layer (residue of the coating layer) removed from the release film 50 is discharged together with cleaning water W2 from drain outlet 32A of cleaning container 32 and filtered by filter 35. Cleaning water W2 filtered by filter 35 is stored in storage section 36, then discharged from drain outlet 36A at the bottom of storage section 36, circulates through circulation path 37, and is supplied again into cleaning container 32 from inlet 38.

[0068] [Other Modifications] In the removal devices described in Figures 4 to 6, the number of guide rollers is not particularly limited. In the removal devices described in Figures 4 and 6, a foreign matter removal means may be provided at any location between the downstream side of the cleaning container 32 (the location where the base film 51 is removed from the cleaning water W2 after the removal step) and the winding means 40. In the case of Figure 5, the foreign matter removal means may be provided at any location between the downstream side of the cleaning container 32 and the folding and collecting means 41A. The foreign matter removal means is a means for removing foreign matter adhering to the base film 51. Examples of foreign matter include a coating layer remaining on the base film 51 and water droplets adhering to the base film 51. The foreign matter removal means is not particularly limited, and examples thereof include an air knife and a dryer.

[0069] The configuration of the release film used in the above embodiment and modified examples will be described.

[0070] [Release Film] The release film used in the above embodiment has a base film and a coating layer. The coating layer includes an intermediate layer and a release agent layer. The intermediate layer is disposed between the base film and the release agent layer. The intermediate layer may be a single layer, or a multi-layer consisting of two or more intermediate layers of the same or different types. The release agent layer may be a single layer, or a multi-layer consisting of two or more release agent layers of the same or different types. From the viewpoint of facilitating removal of the coating layer from the release film and recovery of the remaining base film, the release film preferably has a configuration in which the base film and the intermediate layer are directly laminated. Here, "direct lamination" refers to, for example, a configuration in which the respective layers are in direct contact with each other without any other layer between the base film and the intermediate layer. Furthermore, in one embodiment of the release film, the base film, the intermediate layer, and the release agent layer may be directly laminated in this order. That is, the respective layers may be in direct contact with each other without any other layer between the base film, the intermediate layer, and the release agent layer.

[0071] <Base film> The base film is a resin film formed from a resin component to be recovered. Examples of resin films that can be used include polyester films such as polyethylene terephthalate film, polybutylene terephthalate, and polyethylene naphthalate; polyolefin films such as polyethylene film and polypropylene film; polyimide film; polyamide film; polycarbonate film; polyacetate film; ethylene-vinyl acetate copolymer (EVA) film; ethylene-(meth)acrylic acid copolymer film; ethylene-(meth)acrylic acid ester copolymer film; cycloolefin polymer film; polyurethane film; polyphenylene sulfide film; and cellophane. The density of the base film is preferably greater than the density of water at 40°C, and is 1.0 g / cm. ３ or more is more preferable. This makes it easier for the base film to sink in the cleaning water, and therefore, for example, when a removal process is carried out while stirring the release film released from the sheet stack in the cleaning water, the base film can be easily recovered from the bottom side of the cleaning container. Among base films, polyester film is preferred because it has a density greater than that of water at 40°C and has excellent heat resistance and strength. As the polyester film, polyester films whose main component is polyethylene terephthalate, polybutylene terephthalate, or polyethylene naphthalate are preferred from the viewpoint of easy resin recovery and recycling. In this specification, the term "main component" or "principal component" means that the proportion of the main component to the total mass of the material is 50% by mass or more. The resin film may also contain known fillers, colorants, antistatic agents, antioxidants, organic lubricants, catalysts, etc. The resin film may be transparent or may be colored as desired. Furthermore, at least one surface of the substrate film may be subjected in advance to a surface treatment such as sputtering, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, or etching such as oxidation, as required.

[0072] The thickness of the substrate film is not particularly limited, but from the viewpoint of strength, rigidity, etc., it is preferably 10 μm or more and 500 μm or less, more preferably 15 μm or more and 300 μm or less, and even more preferably 20 μm or more and 200 μm or less.

[0073] <Release Agent Layer> The release agent layer is preferably a layer formed from a release agent composition. The release agent composition used to form the release agent layer is not particularly limited as long as it has releasability, and for example, a release agent composition containing as a main component a silicone-based compound; a fluorine compound; a long-chain alkyl group-containing compound; or a thermoplastic resin material such as an olefin-based resin or a diene-based resin; or the like can be used. It is also preferable to use a release agent composition containing as a main component an energy ray-curable or thermosetting resin. These release agent compositions may be used alone or in combination of two or more.

[0074] In the release agent composition containing a silicone compound as a main component, examples of the silicone compound include silicone compounds having an organopolysiloxane as a basic skeleton. Examples of the silicone compound include heat-curable silicone compounds such as addition reaction type and condensation reaction type; and energy beam-curable silicone compounds such as ultraviolet-curable and electron beam-curable types.

[0075] In the release agent composition containing a fluorine compound as a main component, examples of the fluorine compound include fluorine silicone compounds, fluorine boron compounds, and poly(perfluoroalkylene ether) chain-containing compounds.

[0076] In the release agent composition containing a long-chain alkyl group-containing compound as a main component, examples of the long-chain alkyl group-containing compound include polyvinyl carbamate obtained by reacting a polyvinyl alcohol polymer with a long-chain alkyl isocyanate, alkyl urea derivatives obtained by reacting a polyethyleneimine with a long-chain alkyl isocyanate, and copolymers of long-chain alkyl (meth)acrylates. Furthermore, a long-chain alkyl-modified alkyd resin may be used, which is an alkyd resin obtained by the condensation reaction of a polyhydric alcohol and a polybasic acid and which is modified with a long-chain fatty acid as a modifier.

[0077] As a release agent composition mainly composed of an energy ray-curable resin, for example, one containing an energy ray-curable compound having a reactive functional group selected from a (meth)acryloyl group, an alkenyl group, and a maleimide group, and a polyorganosiloxane is preferred. In the release agent layer formed from this release agent composition, an energy ray-curable compound and a polyorganosiloxane having different molecular structures, polarities, and molecular weights are used, so that before curing, components derived from the polyorganosiloxane are segregated near the outer surface of the release agent layer, and then cured by energy rays, and the segregation is fixed. This improves the releasability of the release agent layer. The release agent composition mainly composed of an energy ray-curable resin may further contain a photopolymerization initiator.

[0078] Examples of release agent compositions containing a thermosetting resin as a primary component include release agent compositions containing a melamine resin as a primary component and release agent compositions containing an epoxy resin as a primary component. Release agent compositions containing a melamine resin as a primary component include compositions containing a melamine resin as a primary component, an acid catalyst for thermally curing the melamine resin, and a polyorganosiloxane that imparts release properties to the release agent layer. Furthermore, release agent compositions containing an epoxy resin as a primary component include compositions containing an epoxy resin as a primary component, an acid or basic thermosetting catalyst for thermally curing the epoxy resin, and a polyorganosiloxane that imparts release properties to the release agent layer. Before curing, components derived from the polyorganosiloxane segregate near the outer surface of the release agent layer, and then cure to solidify the segregation. This improves the release properties of the release agent layer.

[0079] The release agent layer may contain other additives in addition to the resin component, such as an antioxidant, a light stabilizer, a flame retardant, a conductive agent, an antistatic agent, and a plasticizer.

[0080] The thickness of the release agent layer can be appropriately selected and is not particularly limited, but is, for example, preferably 0.02 μm or more and 5 μm or less, more preferably 0.03 μm or more and 2 μm or less, and even more preferably 0.05 μm or more and 1.5 μm or less.

[0081] <Intermediate Layer> The intermediate layer is preferably a layer made of a silane-based compound that is hydrophilic and water-insoluble and exhibits polycondensability upon hydrolysis, from the viewpoint of easier removal of the coating layer from the surface of the intermediate layer facing the substrate film.

[0082] The silane-based compound preferably contains, as a main component, at least one selected from tetrafunctional silane-based compounds represented by the following general formula (a) and oligomers thereof: Si(OR) ｐ (X) ４－ｐ(a) [In general formula (a), R represents an alkyl group, and X represents a halogen atom. When multiple Rs are present, the multiple Rs may be the same or different. When multiple Xs are present, the multiple Xs may be the same or different. p represents an integer of 0 to 4.] The number of carbon atoms in the alkyl group is preferably 1 to 4. The silane-based compounds represented by general formula (a) may be used alone or in combination of two or more.

[0083] Furthermore, the silane compound represented by the general formula (a) preferably includes a silane compound in which p in the general formula (a) is 4. The silane compound in which p in the general formula (a) is 4 (i.e., a tetrafunctional silane compound) is preferably a tetraalkoxysilane. More preferred examples of the tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane. Among these, from the viewpoints of ease of availability and reactivity in the hydrolysis reaction, at least one of tetramethoxysilane and tetraethoxysilane, or a mixture of tetramethoxysilane and tetraethoxysilane, is preferred.

[0084] Commercially available products can also be used as the hydrolysis polycondensate of the silane compound, and suitable examples of such commercially available products include "Colcoat (registered trademark) N-103X," "Colcoat (registered trademark) PX," "Methyl silicate 51" which is an average tetramer oligomer of tetramethoxysilane, "Methyl silicate 53A" which is an average heptamer oligomer of tetramethoxysilane, "Ethyl silicate 40" which is an average pentamer oligomer of tetraethoxysilane, "Ethyl silicate 48" which is an average decamer oligomer of tetraethoxysilane, and "EMS-485" which is a mixture of an average decamer oligomer of tetramethoxysilane and an average decamer oligomer of tetraethoxysilane (all manufactured by Colcoat Co., Ltd.).

[0085] The release film used in each embodiment is preferably a release film after use for a specific application. The release film used for a specific application (in practical use) may have a configuration in which a water-insoluble resin component is blended into the intermediate layer together with the silane compound to improve adhesion between the substrate film and the coating layer (intermediate layer and release agent layer) during use, within a range that does not impair the effects of this embodiment. The intermediate layer may be configured by applying and curing a composition containing a water-insoluble resin component. Examples of water-insoluble resin components include energy ray-curable resins, epoxy resins, and melamine resins. It is preferable that the water-insoluble resin component maintains its water-insolubility even after curing.

[0086] The "water-insoluble resin component" is preferably an energy ray-curable resin, and examples thereof include polyfunctional (meth)acrylates such as dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate. When the intermediate layer contains a hydrophilic and water-insoluble resin (preferably the silane-based compound), the content of the hydrophilic and water-insoluble resin is preferably 30% by mass or more and 90% by mass or less, and more preferably 40% by mass or more and 80% by mass or less, relative to the total mass of the intermediate layer. The upper limit of the content of the hydrophilic and water-insoluble resin in the intermediate layer is 100% by mass. When the intermediate layer contains a hydrophilic, water-insoluble resin (preferably the silane-based compound) and a "water-insoluble resin component," the content of the hydrophilic, water-insoluble resin is preferably 30% by mass or more and 90% by mass or less, and more preferably 40% by mass or more and 80% by mass or less, relative to the total mass of the intermediate layer. The content of the "water-insoluble resin component" is preferably 10% by mass or more and 70% by mass or less, and more preferably 20% by mass or more and 60% by mass or less, relative to the total mass of the intermediate layer. The upper limit of the total content of the hydrophilic, water-insoluble resin and the "water-insoluble resin component" in the intermediate layer is 100% by mass.

[0087] Furthermore, when an energy ray-curable resin is blended in the intermediate layer, it is preferable that the intermediate layer further contains a photopolymerization initiator. Examples of the photopolymerization initiator include 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, and 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone. When the intermediate layer contains a photopolymerization initiator, the content of the photopolymerization initiator is preferably 20 parts by mass or less, and more preferably 10% by mass or less, based on 100 parts by mass of the "water-insoluble resin component."

[0088] The thickness of the intermediate layer is preferably 0.01 μm or more and 1 μm or less, more preferably 0.03 μm or more and 0.5 μm or less, and even more preferably 0.05 μm or more and 0.3 μm or less, from the viewpoint of facilitating water penetration when the intermediate layer comes into contact with water.

[0089] Because the release film used in each embodiment of the present invention has a hydrophilic, water-insoluble intermediate layer, the removed coating layer residue has a configuration in which it has both a release agent layer surface and a hydrophilic intermediate layer surface. When this configuration of residue is immersed in cleaning water, the release agent layer surface faces the air due to surface tension, and the intermediate layer surface faces the water, resulting in stability. In other words, this configuration of residue is more likely to exist at the water-air interface than in water. Here, because the coating layer residue is an extremely thin film, even if it has a slightly higher density, the buoyancy due to surface tension is greater, and it is thought that the water-insoluble intermediate layer allows it to continue floating on the water surface.

[0090] The release film used in each embodiment is generally used for the purpose of protecting the surfaces of other functional sheets or various parts used for specific purposes during the production, transportation, storage, etc. of these functional sheets or parts. In fact, after fulfilling its role of protecting these parts, it is often peeled off from the surface and discarded. Therefore, by using the release film, the coating layer and the base film can be easily separated from the release film, which is an application that greatly contributes from the viewpoints of resource conservation and environmental protection.

[0091] The present invention is not limited to the above-described embodiment, and may include modifications and improvements within the scope of achieving the object of the present invention.

[0092] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0093] Example 1 (Preparation of Release Film) A biaxially stretched polyethylene terephthalate film (thickness: 31 μm) was prepared as a substrate film. Next, a hydrolysis polycondensation product of alkoxysilane (manufactured by Colcoat Co., Ltd., product name "Colcoat (registered trademark) N-103X") was prepared and mixed with isopropyl alcohol to obtain a composition for forming an intermediate layer with a solids concentration of 1.5 mass %. Next, the obtained composition for forming an intermediate layer was uniformly applied to one side of the substrate film using a bar coater so that the thickness of the intermediate layer after drying was 0.1 μm, thereby forming a coating layer. The coating layer was cured by heating at 130°C for 1 minute, thereby forming an intermediate layer. Next, 94 parts by weight of the polyfunctional acrylate dipentaerythritol hexaacrylate (solid content 100% by weight), 1 part by weight of an acrylic-modified polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-22-164A", solid content 100% by weight), and 5 parts by weight of a photopolymerization initiator (manufactured by IGM Resins B.V., trade name "Omnirad (registered trademark) 907" (2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one, solid content 100% by weight) were diluted with a mixed solvent of isopropyl alcohol and methyl ethyl ketone to obtain a release agent composition with a solid content concentration of 20% by weight. The mixing ratio of the mixed solvent of isopropyl alcohol and methyl ethyl ketone was isopropyl alcohol:methyl ethyl ketone = 3:1 (mass ratio).

[0094] The obtained release agent composition was applied onto the intermediate layer formed on the substrate film using a bar coater and dried at 80°C for 1 minute to obtain a coating layer. Next, the coating layer was irradiated with ultraviolet light (integrated light amount: 250 mJ / cm ２) to form a release agent layer (thickness: 1 μm), and a release film (substrate film / intermediate layer / release agent layer) was obtained in which a substrate film, an intermediate layer, and a release agent layer were laminated in this order. The layer consisting of the intermediate layer and the release agent layer (intermediate layer / release agent layer) constitutes a coating layer. In the release film (substrate film / intermediate layer / release agent layer) of Example 1, the water contact angle of the substrate film-side surface of the intermediate layer was 39 degrees. In addition, the water contact angle of the release agent layer surface was 93 degrees. From this, the difference in water contact angle between the release agent layer surface and the substrate film-side surface of the intermediate layer was calculated to be 54 degrees. Next, one sheet of the obtained release film was prepared by cutting it into a 5 cm square (preparation step). This sheet of release film was designated as evaluation sheet film (A). The evaluation sheet film (A) was placed in a basket (length 15 cm, width 15 cm, height 5 cm). A treatment container (volume 4 L) was prepared. The treatment container consisted of a container body and a lid equipped with a pressure relief valve. Purified water (water for steam source) was poured into the container body to a depth of 3 cm. A jig was then placed inside the container body to prevent the evaluation sheet film (A) in the basket from coming into contact with the purified water. A mesh-structured mounting table (10 cm long, 10 cm wide, 5 cm high) was used as the jig. Next, the purified water in the container body was heated to a boil, and the basket containing the evaluation sheet film (A) was placed on the mounting table (storage step). The lid was then closed on the container body, and the evaluation sheet film (A) was exposed to steam at normal pressure for 15 minutes (exposure to steam step). The lid was then removed, and the evaluation sheet film (A) was removed from the basket. Next, the evaluation sheet film (A) was placed in a beaker containing 100 mL of purified water (cleaning water) at room temperature (25°C), and the purified water was stirred with tweezers for 10 seconds (removal step).

[0095] [Example 2] A release film (substrate film / intermediate layer / release agent layer) was prepared in the same manner as in Example 1. Next, 20 sheets of the prepared release film were cut into 5 cm squares and prepared. 20 sheets of the release film were stacked in the same direction to prepare a laminate (preparation step). Two 75 mm square (3 mm thick) float glass sheets were placed on both end surfaces (top and bottom) of the laminate, and the laminate was sandwiched between the two float glass sheets. Next, the edges of the top and bottom float glass sheets were fastened with two clips. This resulted in an evaluation laminate in which the shape of the laminate was maintained. This was designated evaluation laminate (B). The evaluation laminate (B) was placed in a basket similar to that in Example 1. Next, a treatment container similar to that in Example 1 was prepared. Thereafter, the storage step and the step of exposing to water vapor were carried out in the same manner and under the same conditions as in Example 1, except that the "evaluation laminate (B) placed in a basket" was used instead of the "evaluation sheet film (A) placed in a basket" in Example 1. After the step of exposing to water vapor, the lid was removed, and the evaluation laminate (B) was taken out of the basket. The clips and float glass were removed from the evaluation laminate (B), and the sheet laminate was returned to the 20 release films (release step). Next, 20 release films were placed in a beaker containing 100 mL of purified water (cleaning water) at room temperature (25 ° C.), and the purified water was stirred for 10 seconds using tweezers (removal step).

[0096] Example 3: A sheet of film for evaluation (A) was prepared in the same manner as in Example 1 and placed in a basket similar to that in Example 1. Next, a pressure vessel (volume 5 L) was prepared. The pressure vessel consisted of a pressure vessel body and a pressure lid equipped with a relief valve. Purified water (water for steam source) was poured into the pressure vessel body to a depth of 3 cm, and then a jig similar to that in Example 1 was placed inside the pressure vessel body. Next, the purified water in the pressure vessel body was heated and brought to a boil, after which the basket containing the sheet of film for evaluation (A) was placed on a mounting table (storage process). The pressure lid was then closed on the pressure vessel body, the relief valve was set to 2 atmospheres, and heating was resumed. Next, boiling (fume) was confirmed, the pressure inside the pressure vessel reached 2 atmospheres, and the temperature of the superheated water was confirmed to be 120°C. In this state, the sheet of film for evaluation (A) was exposed to steam for 15 minutes (exposure to steam process). Thereafter, the pressure vessel was returned to normal pressure, the pressure lid was removed, and the evaluation sheet film (A) was removed from the basket. Next, the evaluation sheet film (A) was placed in a beaker containing 100 mL of purified water (washing water) at room temperature (25°C), and the purified water was stirred with tweezers for 10 seconds (removal step).

[0097] [Example 4] A laminate (B) for evaluation was prepared in the same manner as in Example 2 and placed in the same basket as in Example 1. Next, a pressure vessel similar to that in Example 3 was prepared. Thereafter, the "evaluation laminate (B) placed in a basket" was used instead of the "evaluation sheet film (A) placed in a basket" in Example 3, and the storage step and the step of exposing to water vapor were carried out in sequence in the same manner and under the same conditions as in Example 3. After the step of exposing to water vapor, the pressure vessel was returned to normal pressure, the pressure lid was removed, and the evaluation laminate (B) was removed from the basket. The clips and float glass were removed from the evaluation laminate (B), and the sheet laminate was returned to 20 release films (release step). Next, 20 release films were placed in a beaker containing 100 mL of purified water (cleaning water) at room temperature (25 ° C.), and the purified water was stirred for 10 seconds using tweezers (removal step).

[0098] Comparative Example 1 A release agent layer was formed on a substrate film without forming an intermediate layer, and a comparative release film (substrate film / release agent layer) was obtained in which the substrate film and the release agent layer were laminated. The water contact angle of the release agent layer surface in the release film (substrate film / release agent layer) of Comparative Example 1 was 93 degrees. However, since the release film of Comparative Example 1 did not have an intermediate layer and the release agent layer was not separated from the substrate film, the water contact angle of the release agent layer on the substrate film side surface could not be measured using the measurement method described below. Next, one sheet of the comparative release film was cut into a 5 cm square and prepared (preparation step). Thereafter, the containing step and the water vapor exposure step were carried out in sequence using the same method and conditions as in Example 1, except that the "comparative release film placed in a basket" was used instead of the "evaluation sheet film (A) placed in a basket" in Example 1. After the water vapor exposure step, the lid was removed, and the comparative release film was taken out of the basket. Next, the comparative release film was placed in a beaker containing 100 mL of purified water (washing water) at room temperature (25° C.), and the purified water was stirred for 10 seconds using tweezers (removal step).

[0099] Reference Example 1 A sheet of film for evaluation (A) was prepared in the same manner as in Example 1. Next, the sheet of film for evaluation (A) was immersed in hot water at 100°C for 15 minutes (immersion step). After immersion for 15 minutes, the sheet of film for evaluation (A) was removed from the hot water. Next, the sheet of film for evaluation (A) was placed in a beaker containing 100 mL of purified water (washing water) at room temperature (25°C), and the purified water was stirred with tweezers for 10 seconds.

[0100] [Coating Layer Removability] The coating layer removability of the release films after the removal process in Examples 1 to 4, Comparative Example 1, and Reference Example 1 was evaluated according to the following criteria. The results are shown in Table 1. In the evaluation criteria, the "release film" refers to all 20 release films in Examples 2 and 4. (Evaluation Criteria) A: By immersing the film in a beaker and gently stirring, most of the coating layer was removed within 5 minutes. B: No coating layer removal occurred under condition A, but most of the coating layer was removed within 120 minutes. C: No coating layer removal occurred under conditions A and B, but by lightly scraping the surface of the release agent layer with steel wool before immersion in the beaker, and then immersing the film in a 500 mL beaker containing 300 mL of purified water at 30°C and gently stirring, most of the coating layer was removed within 120 minutes. D: No coating layer removal occurred under any of conditions A, B, or C.

[0101]

[0102] Using the release films (substrate film / intermediate layer / release agent layer) of Examples 1 to 4, the coating layer could be easily removed from the release films by sequentially performing the accommodation step, the exposure to water vapor step, and the removal step. Using the release film (substrate film / release agent layer) of Comparative Example 1, the coating layer could not be removed from the release film even when the accommodation step, the exposure to water vapor step, and the removal step were sequentially performed. In Reference Example 1, after the accommodation step, the release film was immersed in water (immersion step), and then the removal step was performed. According to Examples 1 to 4, by exposing the release film to water vapor without immersing it in water, the coating layer could be easily removed from the release film, as in Reference Example 1.

[0103] [Evaluation of Intermediate Layer] (Hydrophilicity of Intermediate Layer) Using the release film (substrate film / intermediate layer / release agent layer) obtained in Example 1, the water contact angle of the substrate film-side surface of the intermediate layer was measured by the following method. The results are as described above. First, a 50 mm wide adhesive tape (manufactured by Nitto Denko Corporation, product name "Polyester Adhesive Tape No. 31B") was attached to the release agent layer surface of the release film. The release film with the adhesive tape attached was then cut to a size of 50 mm x 50 mm, and this was used as a test specimen. Next, 300 mL of purified water was filled into a 500 mL glass beaker, and the entire test specimen was immersed in purified water heated to 90°C and left for 3 hours. Thereafter, it was confirmed that the test specimen was separated into a laminate in which the release agent layer and intermediate layer were integrally supported on the adhesive tape, and the substrate film. The adhesive tape carrying the release agent layer and intermediate layer was then removed from the heated purified water and dried at room temperature for 24 hours. Thereafter, the contact angle of water on the surface of the intermediate layer carried on the adhesive tape (the surface of the intermediate layer that had been in contact with the surface of the base film) was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DM-701") by the sessile drop method in accordance with JIS R3257:1999. Distilled water was used as the droplet.

[0104] (Water-insoluble nature of intermediate layer) Using the release films of Example 1 and Comparative Example 1, the water contact angle of the surface of the release agent layer was measured by the method described above. The results are as described above. For Example 1, the difference between the water contact angle of the measured release agent layer surface and the water contact angle of the surface of the intermediate layer facing the substrate film, measured by the method described above, was calculated.

[0105] The release films used in Examples 2 to 4 and Reference Example 1 have the same structure as the release film in Example 1. Therefore, the intermediate layers in Examples 2 to 4 and Reference Example 1 are hydrophilic and water-insoluble.

[0106] 5A, 1G... Winding core, 5B, 2G... Insertion hole, 10... Feeding means, 10A... Support member, 11A... Feeding means for folded stack, 30, 30A... Removal means, 32... Cleaning container, 32A... Drain outlet, 34... Wire brush, 35... Filter, 36... Storage section, 36A... Bottom drain outlet, 37... Circulation path, 38... Inlet, 40... Winding means, 40A... Support member, 41A... Folding and recovery means, 50, 50G... Release film, 51... Base film, 52... Coating layer, 60... Treatment container, 60A... Pressure container, 61... Lid, 61A... Pressure lid, 62... Container body, 62A... Pressure container body, 63... Steam introduction path, 64... Pressure relief pipe, 66... ​​Placement table, 68... Heat motor, 70...pressure control unit, 71...relief valve, 71A...steam exhaust port, 72...pressure sensor, 73...pressure relief valve, 100, 100A, 100B...removal device, 300...circulation means, 400...pressure vessel, 401...pressure vessel body, 402...external housing, 403...lid, 404...steam inlet pipe, 405...steam exhaust pipe, 406...drain pipe, 407...basket, 408...mounting table, 409...storage section, 410...water stopping wall, 411...heater, 420...boiler, 501, 504...roll-shaped stack, 502, 502A...folded stack, 503...sheet-shaped stack, 521...intermediate layer, 522...release agent layer, 601, 601A...edge, 910...recess, 920...residue.

Claims

1. A method for removing a coating layer, comprising the steps of: preparing a release film having a base film and a coating layer; placing the release film in a processing container; exposing the release film to water vapor in the processing container; and removing the coating layer from the release film, wherein the coating layer includes an intermediate layer and a release agent layer, and the intermediate layer is disposed between the base film and the release agent layer.

2. The method for removing a coating layer according to claim 1, wherein the preparing step is a step of preparing a laminate in which a single sheet of the release film is stacked on top of another sheet of the release film, the storing step is a step of storing the release film in the stacked state in the processing vessel, the exposing step is a step of exposing the release film in the stacked state to water vapor, and the removing step is a step of releasing the release film from the stack and then removing the coating layer from the released release film.

3. The method for removing a coating layer described in claim 1, wherein the storing step is a step of storing the release film and water vapor in the processing vessel, and the water vapor is either water vapor generated outside the processing vessel and introduced into the processing vessel, or water vapor generated from water introduced into the processing vessel.

4. A method for removing a coating layer as described in claim 1, wherein the storing step is a step of storing the release film and water vapor in a pressure vessel as the processing vessel, and the water vapor is either water vapor generated outside the pressure vessel and introduced into the pressure vessel, or water vapor generated from water introduced into the pressure vessel.

5. The method for removing a coating layer according to claim 3 or 4, wherein the step of exposing the release film to water vapor is carried out without immersing the release film in liquid water.

6. The method for removing a coating layer according to claim 2, wherein the laminate in which a single sheet of the release film is stacked is a roll-like product in which the long release film is wound up, and the removing step is carried out by roll-to-roll.

7. The method for removing a coating layer according to claim 6, comprising the steps of: after the step of exposing to water vapor, making the release film ready to be unwound from the roll-like material; and unwounding the release film from the roll-like material, and the removing step is a step of immersing the release film unwound from the roll-like material in cleaning water and then scraping the coating layer off from the base film.

8. The method for removing a coating layer according to claim 1 or 2, wherein the release film is a release film with a ceramic green sheet attached, and a ceramic green sheet is attached to the side of the coating layer opposite to the base film.

Images