Method for producing thin film stripped pieces

Abstract

This method for producing thin film stripped pieces comprises: a step (1) for preparing a first intermediate multilayer body which comprises a first base material layer and a thin film that is provided so as to be in contact with the first base material layer; a step (2) for preparing a second intermediate multilayer body which comprises a second base material layer and a water-soluble adhesive layer that is provided so as to be in contact with the second base material layer; a step (3) for obtaining a third intermediate multilayer body by bonding the first intermediate multilayer body and the second intermediate multilayer body in such a manner that the thin film and the water-soluble adhesive layer face each other; a step (4) in which the first base material layer is separated from the third intermediate multilayer body, thereby obtaining a multilayer film which comprises the second base material layer, the water-soluble adhesive layer that is provided so as to be in contact with the second base material layer, and the thin film that is provided so as to be in contact with the water-soluble adhesive layer; a step (5) in which a member having a relief structure is pressed against the thin film side of the multilayer film, thereby forming cracks for dividing the thin film into small pieces; and a step (6) in which the multilayer film that has been provided with the cracks is brought into contact with water, thereby removing the water-soluble adhesive layer from the multilayer film and obtaining thin film stripped pieces. With respect to this method for producing thin film stripped pieces, the water-soluble adhesive layer is formed of a water-soluble adhesive that is mainly composed of a polyvinyl alcohol.

Description

Method for manufacturing peeled pieces of thin film

[0001] The present invention relates to a method for producing a thin film peel piece.

[0002] A known method for producing peeled pieces of a thin film of a cholesteric liquid crystal compound or the like used in ink applications is to form a thin film on a belt and peel the thin film from the belt using an air jet (see Patent Document 1). Another known method involves pressing a member having a concave-convex shape against a multilayer film containing a thin film from the thin film side to divide the thin film into small pieces, and then peeling off the small pieces of the thin film to obtain peeled pieces of the thin film (see Patent Document 2).

[0003] Furthermore, compositions containing specific water-soluble polymers are known as coating compositions for producing various optical films (see Patent Document 3).It is also known that polyvinyl alcohol can be added as a dispersion stabilizer to emulsion compositions containing liquid crystal compounds (see Patent Document 4).

[0004] US Patent No. 5,364,557 JP 2021-133441 A International Publication No. 2018 / 230564 (Corresponding Foreign Publication: US Patent Application Publication No. 2021 / 0079252) JP 2020-126091 A

[0005] In the technology of Patent Document 1, the resulting peeled pieces of thin film are irregular in shape. On the other hand, in the technology of Patent Document 2, the resulting peeled pieces of thin film can be made to have a fixed shape. However, in the technology of Patent Document 2, when a member having a concave-convex shape is pressed against a multilayer film to form cracks in the thin film and divide the thin film into small pieces, the divided small pieces of thin film may peel off and adhere to the member having a concave-convex shape. If the small pieces of thin film adhere to the member having a concave-convex shape, cleaning of the member having a concave-convex shape may be required, which may require the production line to be stopped. Especially when the process of dividing the thin film into small pieces is performed continuously, stopping the production line may result in a decrease in the production efficiency of the peeled pieces of thin film.

[0006] Therefore, when cracks are formed in a thin film using a member having a concave-convex shape, it is required to minimize the number of small pieces of the thin film that adhere to the member having a concave-convex shape.Furthermore, an efficient method for producing peeled pieces of the thin film is required.

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems, and have found that the above-mentioned problems can be solved by obtaining a predetermined multilayer film through a predetermined process and subjecting the multilayer film to a predetermined process, thereby completing the present invention.

[0008] [1] The method includes the steps of: (1) preparing a first intermediate laminate including a first base material layer and a thin film provided in contact with the first base material layer; (2) preparing a second intermediate laminate including a second base material layer and a water-soluble adhesive layer provided in contact with the second base material layer; (3) bonding the first intermediate laminate and the second intermediate laminate together so that the thin film and the water-soluble adhesive layer face each other to obtain a third intermediate laminate; (4) peeling the first base material layer from the third intermediate laminate to obtain a multilayer film including the second base material layer, the water-soluble adhesive layer provided in contact with the second base material layer, and the thin film provided in contact with the water-soluble adhesive layer; (5) pressing a member having an uneven shape against the thin film side of the multilayer film to form cracks that divide the thin film into small pieces; and (6) bringing the multilayer film with the cracks formed into water into contact with water to remove the water-soluble adhesive layer from the multilayer film to obtain peeled pieces of the thin film.

[0014]

[0015] A method for producing a peeled piece of a thin film, wherein the water-soluble adhesive layer is a layer formed from a water-soluble adhesive containing polyvinyl alcohol as a main component. [2] A method for producing a peeled piece of a thin film according to [1], wherein the saponification degree of the polyvinyl alcohol contained in the water-soluble adhesive is 82 mol% or more and 93 mol% or less. [3] A method for producing a peeled piece of a thin film according to [1] or [2], wherein in step (6), the contact of the multilayer film with water is carried out by immersing the multilayer film in water. [4] A method for producing a peeled piece of a thin film according to any one of [1] to [3], wherein the formation of the cracks in step (5) is carried out by forming cracks that divide the thin film into small pieces of the same shape when viewed in the thickness direction.

[0009] According to the present invention, an efficient method for producing a peeled piece of a thin film can be provided.

[0010] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents. The components of the embodiments shown below can be combined as appropriate.

[0011] In the following description, a "long" film refers to a film having a length that is 5 times or more its width, preferably 10 times or more its width, and specifically refers to a film having a length that can be wound into a roll for storage or transportation. There is no particular upper limit to the length of the film, and it can be, for example, 100,000 times or less its width.

[0012] In the following description, unless otherwise specified, the directions of elements as "parallel," "vertical," and "orthogonal" may include an error within a range that does not impair the effects of the present invention, for example, within a range of ±3°, ±2°, or ±1°.

[0013] [1. Overview of the method for manufacturing a peeled piece of a thin film] A method for manufacturing a peeled piece of a thin film according to one embodiment of the present invention includes the steps of: (1) preparing a first intermediate laminate including a first base material layer and a thin film provided in contact with the first base material layer; (2) preparing a second intermediate laminate including a second base material layer and a water-soluble adhesive layer provided in contact with the second base material layer; (3) bonding the first intermediate laminate and the second intermediate laminate together so that the thin film and the water-soluble adhesive layer face each other to obtain a third intermediate laminate; (4) peeling the first base material layer from the third intermediate laminate to obtain a multilayer film including the second base material layer, the water-soluble adhesive layer provided in contact with the second base material layer, and the thin film provided in contact with the water-soluble adhesive layer; and (5) pressing a member having an uneven shape against the thin film side of the multilayer film to form cracks that divide the thin film into small pieces. and step (6) of contacting the cracked multilayer film with water to remove the water-soluble adhesive layer from the multilayer film to obtain a peeled piece of thin film, wherein the water-soluble adhesive layer is a layer formed from a water-soluble adhesive whose main component is polyvinyl alcohol.

[0014] According to the manufacturing method of this embodiment, when cracks are formed in the thin film using a member having a textured surface in step (5), few small pieces adhere to the member having a textured surface and are peeled off, and step (5) can be performed continuously using the same member having a textured surface. Therefore, cracks can be efficiently formed in the thin film. Ultimately, peeled pieces of the thin film can be efficiently produced.

[0015] Furthermore, in step (6), small pieces of the thin film can be easily peeled off from the multilayer film, and therefore peeled pieces of the thin film can be efficiently obtained from the multilayer film.

[0016] The manufacturing method according to this embodiment includes steps (1) to (4), and therefore in step (1), a first substrate layer suitable for forming a thin film can be selected regardless of its adhesiveness to the water-soluble adhesive layer.

[0017] [2. Embodiment of Method for Producing Peel Piece] Hereinafter, a method for producing a peel piece according to one embodiment of the present invention will be described. The production method according to this embodiment includes steps (3), (4), (5), and (6) in this order. The production method according to this embodiment includes steps (1) and (2) before step (3). Steps (1) and (2) may be performed in this order, or may be performed simultaneously, or may be performed in the order of step (2) and step (1).

[0018] [2.1. Step (1)] In step (1), a first intermediate laminate is prepared, which includes a first substrate layer and a thin film provided in contact with the first substrate layer. The first intermediate laminate is preferably long in order to efficiently produce a multilayer film. The thin film may be provided directly on the first substrate layer, or may be provided indirectly on the first substrate layer via an optional layer. Preferably, the thin film is provided directly on the first substrate layer, and no optional layer is present between the thin film and the first substrate layer.

[0019] The thin film is usually disposed on the outermost side in the thickness direction of the first intermediate laminate.

[0020] [First intermediate laminate] (First base layer) The first base layer is preferably long. Examples of materials for forming the first base layer are not particularly limited, and include polymer-containing resins, paper, and metals. Polymer-containing resins are preferred because of their excellent flexibility and mechanical strength. Examples of polymers contained in resins that can form the first base layer include cellulose-based polymers (e.g., triacetyl cellulose); polymers containing alicyclic structures (e.g., cyclic olefin polymers); polyesters (e.g., polyethylene terephthalate); acrylic polymers (e.g., poly(meth)acrylic acid, poly(meth)acrylic acid esters, polyacrylonitrile); and polycarbonates. The resin that can form the first base layer may contain one type of polymer alone or a combination of two or more types. The polymer may be a homopolymer or a copolymer. The resin may contain any additive in addition to the polymer.

[0021] Examples of polymers containing an alicyclic structure include polymers containing structural units having a structure obtained by polymerizing a cyclic olefin and hydrogenated products thereof, and further include (1) norbornene-based polymers, (2) monocyclic olefin polymers, (3) cyclic conjugated diene polymers, (4) vinyl alicyclic hydrocarbon polymers, and hydrogenated products thereof. Among these, norbornene-based polymers and hydrogenated products thereof are preferred from the viewpoints of transparency and moldability.

[0022] Examples of norbornene-based polymers include ring-opening polymers of monomers having a norbornene structure and their hydrogenated products; and addition polymers of monomers having a norbornene structure and their hydrogenated products. Examples of ring-opening polymers of monomers having a norbornene structure include ring-opening homopolymers of one type of monomer having a norbornene structure, ring-opening copolymers of two or more types of monomers having a norbornene structure, and ring-opening copolymers of a monomer having a norbornene structure and any monomer copolymerizable therewith. Examples of addition polymers of monomers having a norbornene structure include addition homopolymers of one type of monomer having a norbornene structure, addition copolymers of two or more types of monomers having a norbornene structure, and addition copolymers of a monomer having a norbornene structure and any monomer copolymerizable therewith. Examples of these polymers include the polymers disclosed in, for example, JP 2002-321302 A.

[0023] Specific examples of suitable norbornene polymers and hydrogenated products thereof include "ZEONOR" manufactured by Nippon Zeon Co., Ltd.; "ARTON" manufactured by JSR Corporation; and "TOPAS" manufactured by TOPAS ADVANCED POLYMERS.

[0024] The thickness of the first substrate layer is preferably 12 μm or more, more preferably 25 μm or more, even more preferably 50 μm or more, and preferably 250 μm or less, more preferably 200 μm or less, even more preferably 188 μm or less. When the thickness of the first substrate layer is equal to or greater than the lower limit, the mechanical strength of the first substrate layer can be made superior. When the thickness of the first substrate layer is equal to or less than the upper limit, the flexibility of the first substrate layer can be improved, making handling during production easier.

[0025] The first substrate layer may have a single-layer structure or a multi-layer structure.

[0026] When the first base layer has a multilayer structure, the layers included in the first base layer preferably have a peel strength sufficient to prevent peeling from each other in steps (3) and (4). The first base layer preferably has a single-layer structure.

[0027] The surface of the first substrate layer may be subjected to a treatment such as rubbing treatment, corona treatment, etc. The first substrate layer may be an unstretched layer or a stretched layer.

[0028] As described above, the first intermediate laminate may be a laminate consisting only of a first substrate layer and a thin film, or may include any layer in addition to the first substrate layer and the thin film. For example, when a liquid crystal composition is used as the composition for forming the thin film, the first intermediate laminate may have an alignment film between the first substrate layer and the thin film in order to favorably align the liquid crystal composition. The alignment film may be formed from a resin containing a polymer such as polyimide, polyvinyl alcohol, polyester, polyarylate, polyamideimide, polyetherimide, or polyamide. These polymers may be used alone or in combination of two or more types in any ratio. The alignment film may be produced by applying a solution containing the polymer, drying it, and then rubbing it.

[0029] (Thin Film) The thin film may have either a single layer structure or a multilayer structure. The thin film may be either a conductor or a dielectric. The thin film may be either an inorganic film or an organic film. Examples of thin films include metal films such as aluminum and silver; dielectric multilayer films formed of dielectric materials such as titanium oxide, silicon oxide, niobium oxide, tantalum oxide, and magnesium fluoride; and resin films.

[0030] Examples of resin materials for forming the resin film include photocurable liquid crystal compositions, acrylic resins, polystyrene, polyesters, polyamides, polyvinyl chloride, polyvinyl acetate, cellulose-based polymers (e.g., triacetyl cellulose), polycarbonates, polyurethanes, polyolefins, polymers containing alicyclic structures, epoxy resins, melamine resins, phenolic resins, and combinations thereof. The polymers that can be contained in the resin material may be homopolymers or copolymers. In addition to the polymer, the resin material may contain optional additives such as a curing agent and an antioxidant.

[0031] The thickness of the thin film can be appropriately set depending on the material of the thin film, the purpose of use of the peeled piece of the thin film, etc., but from the viewpoint of ensuring the reflectivity of the thin film, it is preferably 0.1 μm or more, more preferably 0.3 μm or more, 0.5 μm or more, or 1 μm or more, and preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. By setting the thickness of the thin film to the above upper limit value or less, the obtained peeled piece can be suitably used for inks that are compatible with printing layers of various thicknesses.

[0032] The thin film may be, for example, a film made of a cured product obtained by curing a photocurable liquid crystal composition as a resin-containing composition. That is, the resin for forming the thin film may be, for example, a cured product of a photocurable liquid crystal composition. Here, for convenience, the material referred to as a "liquid crystal composition" includes not only a mixture of two or more substances but also a material made of a single substance.

[0033] Furthermore, a cholesteric resin layer may be used as the thin film. A cholesteric resin layer refers to a resin layer having cholesteric regularity. The cholesteric regularity of a resin layer having cholesteric regularity is a structure in which the molecular axes are aligned in a fixed direction on one plane, but the direction of the molecular axes is slightly shifted at an angle on the next overlapping plane, and then shifted even further on the next plane, so that the angle of the molecular axes in the plane shifts (twists) as the molecules pass through the overlapping planes one after another. That is, when the molecules in a layer have cholesteric regularity, the molecules are aligned in the resin layer in a manner forming a layer of multiple molecules. In a layer A among such multiple molecular layers, the molecules are aligned so that the molecular axes are aligned in a fixed direction, and in an adjacent layer B, the molecules are aligned in a direction shifted at an angle from the direction in layer A, and in an adjacent layer C, the molecules are aligned in a direction further shifted at an angle from the direction in layer B. In this way, in a layer of many molecules, the angles of the molecular axes are continuously shifted, forming a twisted molecular structure. This twisted molecular axis structure is optically chiral.

[0034] The cholesteric resin layer usually has a circularly polarized light separation function. That is, it has the property of transmitting one of right-handed and left-handed circularly polarized light and reflecting part or all of the other circularly polarized light. Furthermore, the cholesteric resin layer reflects circularly polarized light while maintaining its chirality.

[0035] When a cholesteric resin layer such as the one described above is used as the thin film, the manufacturing method of this embodiment can produce a peeled piece consisting of small pieces of resin film that utilize the circularly polarized light separation function. Furthermore, by using a member having an uneven shape that can form cracks that divide the thin film into small pieces of the same shape when viewed from the thickness direction, a peeled piece with a high proportion of small pieces having a uniform shape can be produced.

[0036] The thin film can be formed by any method depending on the material of the thin film, etc. For example, the thin film can be formed by a vapor deposition method, a sputtering method, a coating method, etc. Examples of the coating method include die coating, curtain coating, extrusion coating, roll coating, spin coating, dip coating, bar coating, spray coating, slide coating, print coating, gravure coating, and gap coating.

[0037] [2.2. Step (2)] In step (2), a second intermediate laminate is prepared, including a second substrate layer and a water-soluble adhesive layer provided in contact with the second substrate layer. The second intermediate laminate is preferably long in order to efficiently produce a multilayer film. Preferably, the water-soluble adhesive layer is provided directly on the second substrate layer, and no other layer is present between the water-soluble adhesive layer and the second substrate layer. The water-soluble adhesive layer is usually positioned on the outermost side in the thickness direction of the second intermediate laminate.

[0038] [Second Intermediate Laminate] (Second Base Layer) The second base layer is preferably long. Examples of the second base layer include the same examples as those of the first base layer described above. The thickness of the second base layer can be in the same range as the preferred range of the first base layer described above. The second base layer may have a single-layer structure or a multi-layer structure. Preferably, the second base layer has a single-layer structure. The second base layer may be an unstretched layer or a stretched layer. Preferably, the second base layer is an unstretched layer. The second base layer may be subjected to a surface treatment such as an easy-adhesion treatment. From the viewpoint of adhesion to a water-soluble adhesive, the second base layer is preferably a layer containing polyethylene terephthalate (PET) (e.g., "Cosmoshine (registered trademark) A4100" manufactured by Toyobo Co., Ltd.).

[0039] (Water-soluble adhesive layer) The water-soluble adhesive layer is a layer formed from a water-soluble adhesive. The water-soluble adhesive can be mixed with water in any ratio. From the viewpoint of good adhesion and water solubility and easy removal of the water-soluble adhesive layer in step (6) described below, the water-soluble adhesive layer is a layer formed from a water-soluble adhesive containing polyvinyl alcohol as a main component. Here, a water-soluble adhesive containing polyvinyl alcohol as a main component refers to a water-soluble adhesive in which the weight proportion of polyvinyl alcohol is usually 50 wt% or more, preferably 65 wt%, and usually 100 wt% or less, based on 100 wt% of the solid content excluding the solvent in the water-soluble adhesive.

[0040] Here, the term "polyvinyl alcohol" includes fully saponified polymers, partially saponified polymers, modified products, and combinations thereof.

[0041] The water-soluble adhesive may contain one type of polyvinyl alcohol alone or two or more types in any combination in any ratio.

[0042] The water-soluble adhesive may or may not contain optional components in addition to polyvinyl alcohol. Examples of optional components include polymers other than polyvinyl alcohol. Examples of polymers other than polyvinyl alcohol include, but are not limited to, polyacrylamide, polyvinylpyrrolidone, polyvinylamide, carboxymethylcellulose (CMC) (e.g., "Sunrose" (registered trademark) (manufactured by Nippon Paper Industries Co., Ltd.)), polyethylene oxide, starch, and protein. These may be used alone or in combination of two or more in any ratio.

[0043] The water-soluble adhesive may or may not contain a solvent such as water. The water-soluble adhesive layer may have some or all of the solvent such as water removed.

[0044] The weight proportion of polyvinyl alcohol in the water-soluble adhesive is, for example, 0.1 wt % or more, for example, 0.5 wt % or more, for example, 1 wt % or more, and is usually 100 wt % or less, and may be 100 wt %.

[0045] The saponification degree of the polyvinyl alcohol contained in the water-soluble adhesive (polyvinyl alcohol adhesive) is preferably 82 mol% or more, more preferably 83 mol% or more, and even more preferably 85 mol% or more, from the viewpoint of facilitating the handling of the multilayer film and improving the peeling efficiency of the thin film, and is preferably 93 mol% or less, more preferably 92 mol% or less, and even more preferably 90 mol% or less, from the viewpoint of making the water-soluble adhesive layer more soluble in water and improving the peeling efficiency of the thin film. The saponification degree of polyvinyl alcohol can be measured in accordance with JIS K6726 (Polyvinyl Alcohol Testing Method).

[0046] The viscosity of polyvinyl alcohol is preferably 4.8 mPa·s or more, and from the viewpoint of further improving the coatability of the water-soluble adhesive and the solubility of the water-soluble adhesive layer in water, it is preferably 60 mPa·s or less, more preferably 55 mPa·s or less, and even more preferably 50 mPa·s or less. In this specification, the viscosity of polyvinyl alcohol refers to the viscosity of a 4% aqueous solution at 20°C, measured in accordance with JIS K6726 (Polyvinyl Alcohol Testing Method). Specifically, polyvinyl alcohol is dissolved in water to prepare a 4% aqueous solution, and the viscosity at 20°C is measured using an "EMS-1000" (manufactured by KYOTO ELECTORONICS) with a spherical probe diameter of 2 mm at 1000 rpm. The same applies to the examples.

[0047] Commercially available polyvinyl alcohols can be used. Examples of commercially available polyvinyl alcohols include the "GOHSENOL (registered trademark) series" manufactured by Mitsubishi Chemical Corporation (e.g., GL-03, GL-05, GM-14L, GM14, GH-17, GH-20, GH-23, AL-06, P-610, and C-500), and the "Kuraray Poval (registered trademark) series" manufactured by Kuraray Co., Ltd. (e.g., 25-88KL, 32-97KL, and 3-86SD). , 105-88KX, 200-88KX, SD-1000), Kuraray's "EXCEVAL (registered trademark) series" (e.g., AQ-41-4, HR-3010, RS-2117, RS-1717), and Denka Company Limited's "DENKA POVAL (registered trademark) series" (e.g., H-12, H-17, H-24, B-05, B-17, B-20, B-24, B-33).

[0048] From the viewpoint of balancing the strength of the water-soluble adhesive layer with ease of removal, the thickness of the water-soluble adhesive layer is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more, and is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

[0049] The water-soluble adhesive layer can be formed by any method. For example, the water-soluble adhesive layer can be obtained by applying a water-soluble adhesive to the surface of the second substrate layer to obtain a coating layer, and then drying the coating layer as needed. When drying the coating layer to obtain a water-soluble adhesive layer, examples of the drying method include, but are not limited to, heat drying, vacuum drying, and heat vacuum drying. When heating the coating layer to obtain a water-soluble adhesive layer, the heating time is, but is not limited to, for example, 1 minute or more, for example, 5 minutes or more, and for example, 120 minutes or less, for example, 60 minutes or less. The heating temperature depends on the glass transition temperature of the second substrate layer and the type of water-soluble adhesive layer, but is, for example, 30°C or more, for example, 60°C or more, and for example, 100°C or less, for example, 90°C or less.

[0050] When applying the water-soluble adhesive to the surface of the second substrate layer, the water-soluble adhesive may be heated to a molten state. The application method is not particularly limited, and examples thereof include the same examples as those of the application method exemplified above as the method for forming a thin film. Alternatively, a film of the water-soluble adhesive may be obtained by a molding method such as melt extrusion or solution casting, separately from the second substrate layer, and this film of the water-soluble adhesive may be attached to the surface of the second substrate layer as a water-soluble adhesive layer.

[0051] [2.3. Step (3)] In step (3), the first intermediate laminate and the second intermediate laminate are bonded together so that the thin film and the water-soluble adhesive layer face each other to obtain a third intermediate laminate. The third intermediate laminate is preferably long in order to efficiently produce a multilayer film. The third intermediate laminate includes a first base layer, a thin film, a water-soluble adhesive layer, and a second base layer in this order in the thickness direction. The thin film and the water-soluble adhesive layer are usually in direct contact with each other.

[0052] [2.4. Step (4)] In step (4), the first base layer is peeled off from the third intermediate laminate to obtain a multilayer film. The multilayer film is preferably long because it can continuously form cracks that divide the thin film into small pieces. The multilayer film includes a second base layer, a water-soluble adhesive layer provided in contact with the second base layer, and a thin film provided in contact with the water-soluble adhesive layer in this order in the thickness direction. The thickness of the multilayer film is not particularly limited, but may be, for example, 30 μm or more and 500 μm or less.

[0053] [2.5. Step (5)] In step (5), a member having an uneven shape is pressed against the thin film side of the multilayer film to form cracks that divide the thin film into small pieces.

[0054] In step (5), if a multilayer film having the above layer configuration including a water-soluble adhesive layer is used, it is possible to reduce the number of small pieces of thin film that adhere to the member having an uneven shape when cracks are formed in the multilayer film.

[0055] The formation of cracks in step (5) is preferably carried out by forming cracks that divide the thin film into small pieces of the same shape when viewed in the thickness direction of the thin film, and preferably the cracks are formed so as to reach a position deeper than the surface of the thin film side of the base layer across the entire surface of the multilayer film.

[0056] The shape of the flakes as viewed in the thickness direction of the thin film is not particularly limited, and examples include polygons such as triangles, squares, and hexagons, crosses, and circles, with triangles, squares, and hexagons being preferred.

[0057] The major axis of the flakes as viewed in the thickness direction of the thin film is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 175 μm or less, and even more preferably 150 μm or less, from the viewpoint of suppressing clogging of the printing plate with ink when the peeled off piece is used in ink, and is usually greater than 0 μm, preferably 10 μm or more, from the viewpoint of improving the visibility of the printing layer formed by the ink when the peeled off piece is used in ink. Here, the major axis refers to the longest distance between multiple parallel lines drawn tangent to the outline of the flakes.

[0058] (Method of forming cracks) Cracks can be formed by pressing a member having a concave-convex shape against the thin film side of the multilayer film. More specifically, in a state where the multilayer film is supported by a support member, the multilayer film is sandwiched between the support member and the member having a concave-convex shape, and the member having a concave-convex shape is pressed to form cracks.

[0059] As a member having a concave-convex shape, a member having convex portions on its surface corresponding to the shape of the cracks as viewed from the thickness direction of the multilayer film can be used. For example, if the shape of the cracks as viewed from the thickness direction of the multilayer film is lattice-shaped, a member having lattice-shaped convex portions on its surface can be used. Also, if the shape of the cracks as viewed from the thickness direction of the multilayer film is honeycomb-shaped, a member having honeycomb-shaped convex portions on its surface can be used.

[0060] In addition, multiple members may be used as the member having a concave-convex shape. For example, a member having a convex portion on its surface corresponding to one part of the crack and a member having a convex portion on its surface corresponding to another part of the crack may be used. For example, if the crack is lattice-shaped and divides the thin film into squares when viewed in the thickness direction, the crack may be formed by pressing a first member having a concave-convex shape on its surface that corresponds to the indentations in one direction that make up the crack, and a second member having a concave-convex shape on its surface that corresponds to the indentations in another direction that make up the crack, against the multilayer film.

[0061] Alternatively, the same member having a concave-convex shape may be pressed against the multilayer film multiple times in different positions to form cracks.

[0062] The member having the irregular shape may be cylindrical, and continuous cracks may be formed in the multilayer film.

[0063] As the member having a concave-convex shape, a material that has enough strength to prevent breakage even when the multilayer film is pressed and that can form a concave-convex structure can be used. Examples of such materials include carbon steel and stainless steel. Furthermore, the member having a concave-convex shape may have one or more multilayer coatings on its surface for the purpose of improving corrosion resistance, strength, thermal conductivity, etc. Examples of such coatings include, but are not limited to, plating films of nickel, nickel phosphorus, silicon, copper, etc., and coatings formed by ceramic spraying. The member having a concave-convex shape may be equipped with a heating means using, for example, a heater, a heat medium, induction heating, etc., a static eliminator for static electricity prevention, a ground, etc.

[0064] A member having a concave-convex shape can be manufactured by any conventionally known method. For example, a member having a desired concave-convex shape can be formed by cutting a member such as a cylindrical metal roll using a cutting tool such as a diamond turning tool or by processing the member using a laser processing device.

[0065] The pressure when pressing the member having a concave-convex shape against the thin film side of the multilayer film is preferably 0.5 MPa or more, more preferably 1 MPa or more, even more preferably 5 MPa or more, and preferably 100 MPa or less, more preferably 75 MPa or less. By setting the pressure to the lower limit or more, cracks of sufficient depth can be formed in the multilayer film, and by setting the pressure to the upper limit or less, damage to the multilayer film can be suppressed. When one or more members having a concave-convex shape are pressed against the multilayer film multiple times to form cracks in the multilayer film, the multiple pressings may be the same or different. Preferably, the multiple pressings are performed at the same pressure.

[0066] The support member typically has a support surface that supports the surface opposite the thin film contained in the multilayer film. The hardness of the support surface that supports the multilayer film surface is preferably D40 or more, more preferably D60 or more, even more preferably D70 or more, and preferably D99 or less, more preferably D97 or less, and even more preferably D95 or less. Here, the hardness is a value measured using a durometer (type D) in accordance with JIS K-6253. By setting the hardness of the support surface of the support member within the above range, cracks of an appropriate depth can be easily formed in the multilayer film. As the support member, a material having a strength that does not cause damage even when the multilayer film is pressed by a member having an uneven shape can be used. Examples of materials for the surface of the support member include metal, rubber (e.g., silicone rubber), and resin (e.g., acrylic resin).

[0067] The shape of the support member can be any shape (for example, a roll shape or a flat plate shape) depending on, for example, the method of transporting the multilayer film and the method of pressing the member having the uneven shape against the multilayer film. Since cracks can be continuously formed in the multilayer film using a long multilayer film, the support member is preferably in a roll shape.

[0068] [2.6. Step (6)] In step (6), the cracked multilayer film is brought into contact with water to remove the water-soluble adhesive layer from the multilayer film, thereby obtaining a peeled piece of thin film. By removing the water-soluble adhesive layer from the cracked multilayer film, small pieces of thin film are peeled off from the second substrate layer, and a peeled piece can be obtained.

[0069] In step (6), by using a multilayer film containing a water-soluble adhesive layer formed from the water-soluble adhesive whose main component is polyvinyl alcohol, small pieces of thin film can be efficiently peeled off from the multilayer film in which cracks have formed.

[0070] Examples of methods for contacting the multilayer film with water to remove the water-soluble adhesive layer include, but are not limited to, spraying water onto the multilayer film and immersing the multilayer film in water, with the method of immersing the multilayer film in water being preferred.

[0071] When spraying water onto the multilayer film to remove the water-soluble adhesive layer, a known fluid ejection device can be used as the spraying device. The pressure of the water ejected from the fluid ejection device can be appropriately adjusted depending on the peel strength between the second base layer and the thin film, etc. The ejection pressure is not particularly limited, but is preferably 5 MPa or more, more preferably 10 MPa or more, and preferably 50 MPa or less, more preferably 35 MPa or less.

[0072] When the water-soluble adhesive layer is removed from the multilayer film by immersing the multilayer film in water, the multilayer film may be exposed to a water flow in the water, or the multilayer film may be immersed in still water without being exposed to a water flow. From the viewpoint of obtaining a peeled piece having a higher proportion of small pieces having a regular shape, it is preferable to remove the water-soluble adhesive layer by immersing the multilayer film in still water.

[0073] When the water-soluble adhesive layer is removed by contacting the multilayer film with water, the temperature of the water can be adjusted appropriately depending on the solubility of the water-soluble adhesive used in water, the thickness of the water-soluble adhesive layer, etc. The temperature of the water brought into contact with the multilayer film is not particularly limited, but is preferably 10°C or higher, more preferably 15°C or higher, and even more preferably 20°C or higher, for example, 100°C or lower.

[0074] When the multilayer film having cracks formed therein is long, peel pieces can be efficiently produced by continuously contacting the film with water.

[0075] [2.7. Optional Steps Other Than the Above Steps] The manufacturing method of this embodiment may include optional steps other than the above steps. For example, it may include a step of passing the peeled pieces through a sieve. Specifically, for example, the peeled pieces may be passed through a filter with a predetermined mesh size. It may also include a step of recovering the peeled pieces. Specifically, for example, after contacting the multilayer film with water to obtain the peeled pieces, the peeled pieces may be guided together with the water into a recovery path and recovered by a recovery device. As the recovery device, for example, a cyclone-type separator and various filters can be used.

[0076] [3. Properties of the Peel Pieces] When the crack formation in step (5) is performed by forming cracks that divide the thin film into small pieces of the same shape when viewed in the thickness direction, a large proportion of the resulting thin film peel pieces have a regular shape along the cracks. This proportion can be evaluated, for example, by the following method. The peel pieces are prepared as a 10 wt % aqueous dispersion. The aqueous dispersion is dropped onto a preparation, and the water is evaporated to allow the peel pieces to adhere to the preparation. The area on the preparation where the peel pieces adhere is observed under a microscope. Within a 1 mm square area, the number (A) of regular-shaped peel pieces and the number (B) of irregular-shaped peel pieces are counted, and the percentage X of the number (B) to the number (A) is calculated according to the following formula: X = B / A × 100 (%). The smaller the percentage X, the higher the proportion of peel pieces with a regular shape along the cracks among all the peel pieces.

[0077] The percentage X of the peeled pieces is preferably 5% or less, more preferably less than 5%, even more preferably 4% or less, even more preferably 3% or less, even more preferably less than 3%, and is preferably 0%, but may be 0% or more or 1% or more.

[0078] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below, and can be practiced with any modifications within the scope of the claims of the present invention and their equivalents.

[0079] In the following description, the "%" and "parts" that represent amounts are by weight unless otherwise specified. Furthermore, the operations described below were carried out at room temperature (20°C ± 15°C) and atmospheric pressure (1 atm) unless otherwise specified.

[0080] (Measurement of Layer Thickness) The layer thickness was measured by cutting the multilayer film along the thickness direction using an ultramicrotome "Leica Ultracut-UCT" (manufactured by Leica Biosystems) to prepare a cross section, and observing the cross section with a digital microscope "VHX8000" (manufactured by KEYENCE).

[0081] (Evaluation of Shape Conformity of Peel Pieces) The peel pieces obtained in each example were made into a 10 wt % aqueous dispersion. Next, the aqueous dispersion was dropped onto a preparation, and the water was evaporated to allow the peel pieces to adhere to the preparation. The area on the preparation where the peel pieces adhered was observed under an optical microscope. Within a 1 mm square area, the number (A) of regular peel pieces and the number (B) of irregular peel pieces corresponding to the irregularities of the member having an irregular shape in each example were counted, and the percentage X of the number (B) to the number (A) was calculated according to the following formula: X = B / A x 100 (%) The smaller the percentage X, the higher the proportion of peel pieces having a regular shape along the crack. In other words, the shape conformity was higher. The shape conformity of the peel pieces was evaluated according to the following criteria: A: X<3%, B: 3%≦X<5% C: 5%≦X<10%, D: 10%≦X, or A=0.

[0082] (Efficiency in forming cracks in thin film) After forming cracks in the multilayer film, the total area (C) of the multilayer film in which the cracks were formed and the area (D) of the thin film peeled off from the multilayer film were measured, and the percentage Y of the area (D) to the total area (C) was calculated according to the following formula: Y = D / C x 100 (%) The smaller the percentage Y, the fewer small pieces that adhere to the member having a concave-convex shape and peel off when cracks are formed in the thin film using a member having a concave-convex shape, and the thin film can be continuously divided into small pieces. In other words, cracks can be formed in the thin film more efficiently. The efficiency in forming cracks in the thin film was evaluated according to the following criteria: A: Y<5% B: 5%≦Y<10% C: 10%≦Y

[0083] (Thin film peeling efficiency) In each example and comparative example except for Example 6, a cracked multilayer film sample (10 cm x 10 cm) was gently immersed in 1 L of water (20 ° C.) placed in a cylindrical container with a diameter of 20 cm. After 30 seconds of immersion, the sample was gently pulled out of the water. In Example 6, water was sprayed onto the cracked multilayer film sample (10 cm x 10 cm) from the thin film side at a discharge pressure of 60 MPa. Next, the sample was examined under a microscope at 200x magnification, and the number (E) of thin film squares that did not peel off within a 1 mm square area was confirmed. From the total number (100) of thin film small pieces before the peeling operation in a 1 mm square and the number (E) of thin film small pieces that did not peel off, the percentage Z of the number (E) of thin film small pieces that did not peel off relative to the total number of 100 thin film small pieces was calculated according to the following formula. Z = E / 100 x 100 (%) The percentage Z was calculated in the same way at five randomly selected locations on one sample, and the average value was used as the sample value Zav. The larger the average percentage Zav, the more small pieces that did not peel off, i.e., the poorer the peeling efficiency. If the water-soluble adhesive layer is not easily dissolved when immersed in water, the peeling efficiency tends to be poor. The peeling efficiency was evaluated according to the following criteria: A: Zav<5% B: 5%≦Zav<10% C: 10%≦Zav

[0084] Example 1 (1-1. Step (1): Preparation of first intermediate laminate) (1-1-1. Preparation of photocurable liquid crystal composition) A photocurable liquid crystal composition was prepared by mixing 18.1 parts of a photopolymerizable liquid crystal compound "Paliocolor LC242" manufactured by BASF, 1.3 parts of "LC756" manufactured by BASF as a chiral agent, 0.6 parts of "Irgacure OXEO2" manufactured by Ciba Japan as a photopolymerization initiator, 0.02 parts of "Ftergent 209F" manufactured by Neos Corporation as a surfactant, and 80 parts of cyclopentanone.

[0085] (1-1-2. Production of Long First Intermediate Laminate) A long cycloolefin polymer (COP) film (ZF16-100 manufactured by Zeon Corporation; thickness 100 μm, hereinafter also referred to as COP film) was prepared as a first substrate layer. This COP film was attached to the unwinding section of a film transport device, and the following operations were performed while transporting the COP film in the longitudinal direction. First, a rubbing treatment was performed in the longitudinal direction parallel to the transport direction. Next, the liquid crystal composition prepared in (1-1-1) was applied to the rubbed surface using a die coater. This formed a film of the uncured liquid crystal composition on one side of the COP film as the first substrate layer.

[0086] The resulting film of the liquid crystal composition was subjected to an alignment treatment at 100°C for 5 minutes, and then the film of the liquid crystal composition was subjected to an irradiation of 800 mJ / cm2 under a nitrogen atmosphere. ２ The liquid crystal composition film was completely cured by irradiating it with ultraviolet light of 1000 kJ / cm. This resulted in a first intermediate laminate having a 5 μm-thick thin film made of resin on one side of a long COP film serving as a first substrate layer. The first intermediate laminate had a layer structure of (COP film serving as a first substrate layer) / (thin film made of resin). The thin film made of resin functioned as a cholesteric resin layer.

[0087] (1-2. Step (2): Preparation of second intermediate laminate) (1-2-1. Preparation of water-soluble adhesive) Polyvinyl alcohol (PVA) (Gohsenol (registered trademark) GL-05 manufactured by Mitsubishi Chemical Corporation, saponification degree 87 mol%, viscosity of 4% aqueous solution (20°C) 4.8 mPa s) was dissolved in water to prepare a 10 wt% aqueous solution of PVA as a water-soluble adhesive. During preparation, stirring and heating were performed so that the PVA would dissolve in water.

[0088] (1-2-2. Production of Long Second Intermediate Laminate) A long polyester (polyethylene terephthalate) film (Cosmoshine (registered trademark) A4100 manufactured by Toyobo Co., Ltd.) was prepared as the second base layer. The water-soluble adhesive prepared in (1-2-1) above was applied to this polyester film using a wire bar (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) to form a coating layer. The thickness of the coating layer was adjusted so that the water-soluble adhesive layer in the multilayer film after drying would be 5 μm. This resulted in a second intermediate laminate including a polyester film as the second base layer and a water-soluble adhesive layer (coating layer) provided in contact with one side of the polyester film.

[0089] (1-3. Step (3): Production of third intermediate laminate) Next, the first intermediate laminate was placed on top of the second intermediate laminate so that the coating layer (water-soluble adhesive layer) of the second intermediate laminate faced the thin film of the first intermediate laminate and so that no air bubbles were trapped between the coating layer and the thin film, and the second intermediate laminate and the first intermediate laminate were bonded together. The resulting laminate was placed in a drying oven at 100°C for 5 minutes to dry the coating layer and produce a third intermediate laminate.

[0090] (1-4. Step (4): Production of multilayer film) The COP film as the first base layer was then peeled off from the third intermediate laminate to obtain a multilayer film. The multilayer film had, in this order, a polyester film as the second base layer, a water-soluble adhesive layer, and a thin film (resin thin film).

[0091] (1-5. Step (5)) (1-5-1. Preparation of member (roll) having uneven shape) A metal roll made of stainless steel with electroless nickel plating (NiP plating) applied to its surface was prepared. The plated surface of the roll was cut with a diamond turning tool (vertex angle 60°) to obtain roll A and roll B having multiple protrusions. For roll A, the multiple protrusions were formed so that the protrusions extended in a direction that formed an angle of 45° upward to the right with respect to a straight line on the circumferential surface of the roll that was parallel to the roll axis, so that the pitch of the protrusions was 100 μm, and so that the angle of the apex of the protrusions was 60° in a cross section perpendicular to the direction in which the protrusions extended. In roll B, the multiple convex portions were formed so that the convex portions extended in a direction that formed an angle of 45° upward to the left with respect to a straight line on the circumferential surface of the roll that was parallel to the roll axis, so that the pitch of the convex portions was 100 μm, and so that the angle of the apex of the convex portions was 60° in a cross section perpendicular to the direction in which the convex portions extended.

[0092] (1-5-2. Crack formation) The multilayer film produced in (1-4) above was pressed with the roll A produced in (1-5-1) from the resin thin film side (press pressure 10 MPa), and then the roll B was pressed (press pressure 10 MPa) to form cracks in the multilayer film. At that time, the side opposite the resin thin film of the multilayer film (the second base layer side) was supported with a backup roll. The backup roll used was a roll with a surface hardness of D70. Here, the hardness is a value measured using a durometer (type D) in accordance with JIS K-6253. As a result, the resin thin film of the multilayer film was divided into square pieces with sides of 100 μm when viewed from the thickness direction of the resin thin film.

[0093] The cracked multilayer films were evaluated for their efficiency in forming cracks in the thin film by the method described above.

[0094] (1-6. Step (6): Production of peeled piece) A multilayer film (10 cm × 10 cm) on which a crack had formed was gently immersed in 1 L of water (20°C) contained in a cylindrical container with a diameter of 20 cm. 30 seconds after immersion, the multilayer film was gently pulled out of the water. The multilayer film pulled out of the water was evaluated for thin film peeling efficiency using the method described above.

[0095] After gently lifting the multilayer film from the cylindrical container, the remaining 1 L of water in the cylindrical container and the peeled pieces in the water were passed through a filter with a mesh size of 53 μm, and then dried together with the filter to recover the peeled pieces in the water.

[0096] The shape conformity of the obtained peeled pieces was evaluated by the method described above.

[0097] Example 2 In the above (1-2-1), polyvinyl alcohol ("EXCEVAL (registered trademark) RS-1717" manufactured by Kuraray Co., Ltd., saponification degree 93 mol%) was used instead of polyvinyl alcohol ("GOHSENOL (registered trademark) GL-05" manufactured by Mitsubishi Chemical Corporation). Except for the above, the same procedures as in Example 1 were carried out to evaluate the efficiency of forming cracks in the thin film, the peeling efficiency of the thin film, and the shape conformity of the peeled piece.

[0098] Example 3 In the above (1-2-1), polyvinyl alcohol (Kuraray Poval (registered trademark) SD-1000, saponification degree 83 mol%) manufactured by Kuraray Co., Ltd. was used instead of polyvinyl alcohol (Gohsenol (registered trademark) GL-05 manufactured by Mitsubishi Chemical Corporation). Except for the above, the same procedures as in Example 1 were carried out to evaluate the efficiency of forming cracks in the thin film, the peeling efficiency of the thin film, and the shape conformity of the peeled piece.

[0099] Example 4 The following (4-1) was carried out instead of (1-1). (4-1. Step (1): Preparation of First Intermediate Laminate) A long cycloolefin polymer (COP) film (ZF16-100 manufactured by Zeon Corporation; thickness 100 μm, hereinafter also referred to as COP film) was prepared as a first substrate layer. Metallic aluminum was vapor-deposited onto this COP film to a thickness of 300 nm using a vapor deposition device, to obtain a first intermediate laminate comprising a thin film of aluminum with a thickness of 300 nm on one side of the COP film as the first substrate layer. The first intermediate laminate had a layer structure of (COP film as first substrate layer) / (thin film of metallic aluminum).

[0100] Other than the above, the same procedures as in Example 1 were carried out to evaluate the efficiency of forming cracks in the thin film, the efficiency of peeling the thin film, and the shape conformity of the peeled pieces.

[0101] [Example 5] Instead of (1-5), the following (5-5) was carried out. (5-5. Step (5)) A cylindrical Thomson blade having a lattice-shaped blade with a side length of 100 μm was prepared. The cylindrical Thomson blade was pressed against the multilayer film produced in (1-4) above from the resin thin film side to form cracks in the multilayer film. At this time, the side of the resin film opposite the resin thin film (the second base layer side) was supported by a backup roll. The backup roll used was a roll with a surface hardness of D70. Here, the hardness is a value measured using a durometer (type D) in accordance with JIS K-6253. As a result, the resin thin film of the multilayer film was divided into square pieces with a side length of 100 μm when viewed from the thickness direction of the resin thin film.

[0102] The cracked multilayer films were evaluated for their efficiency in forming cracks in the thin film by the method described above.

[0103] Other than the above, the same procedures as in Example 1 were carried out to evaluate the efficiency of forming cracks in the thin film, the efficiency of peeling the thin film, and the shape conformity of the peeled pieces.

[0104] [Example 6] Instead of (1-6), the following (6-6) was carried out. (6-6. Step (6): Production of peeled piece) Water was sprayed onto the cracked multilayer film from the thin film side at a discharge pressure of 60 MPa to peel off a small piece of the thin film from the multilayer film.

[0105] The water and the peeled pieces in the water were passed through a filter with a mesh size of 53 μm, and then dried together with the filter to recover the peeled pieces in the water.

[0106] Other than the above, the same procedures as in Example 1 were carried out to evaluate the efficiency of forming cracks in the thin film, the efficiency of peeling the thin film, and the shape conformity of the peeled pieces.

[0107] Example 7 In the above (1-2-1), polyvinyl alcohol (Kuraray Poval (registered trademark) MP-203, saponification degree 88 mol%) manufactured by Kuraray Co., Ltd. was used instead of polyvinyl alcohol (Gohsenol (registered trademark) GL-05 manufactured by Mitsubishi Chemical Corporation). Except for the above, the same procedures as in Example 1 were carried out to evaluate the efficiency of forming cracks in the thin film, the peeling efficiency of the thin film, and the shape conformity of the peeled piece.

[0108] Example 8 In the above (1-2-1), polyvinyl alcohol ("EXCEVAL (registered trademark) RS-2817" manufactured by Kuraray Co., Ltd., saponification degree 96 mol%) was used instead of polyvinyl alcohol ("GOHSENOL (registered trademark) GL-05" manufactured by Mitsubishi Chemical Corporation). Except for the above, the same procedures as in Example 1 were carried out to evaluate the efficiency of forming cracks in the thin film, the peeling efficiency of the thin film, and the shape conformity of the peeled piece.

[0109] Example 9 In the above (1-2-1), polyvinyl alcohol (Gohsenol (registered trademark) GL-05 manufactured by Mitsubishi Chemical Corporation) was replaced with polyvinyl alcohol (Gohsenol (registered trademark) KH-17 manufactured by Mitsubishi Chemical Corporation, saponification degree 81 mol%). Except for the above, the same procedures as in Example 1 were carried out to evaluate the efficiency of forming cracks in the thin film, the efficiency of peeling the thin film, and the shape conformity of the peeled piece.

[0110] Example 10 In the above (1-2-1), polyvinyl alcohol (Kuraray Poval (registered trademark) PVA-117, manufactured by Kuraray Co., Ltd., saponification degree 98 mol%) was used instead of polyvinyl alcohol (Gohsenol (registered trademark) GL-05, manufactured by Mitsubishi Chemical Corporation). Except for the above, the same procedures as in Example 1 were carried out to evaluate the efficiency of forming cracks in the thin film, the peeling efficiency of the thin film, and the shape conformity of the peeled piece.

[0111] [Comparative Example 1] In (1-1-2), instead of the COP film serving as the first base layer, a long PET film ("Cosmoshine (registered trademark) A4100" manufactured by Toyobo Co., Ltd.; thickness 100 μm, hereinafter also referred to as PET film) was prepared. The same operation as in (1-1-2) was performed except that a PET film was used instead of the COP film. This resulted in a laminate as a laminate film having a 5 μm-thick thin film made of resin on one side of the long PET film. This laminate had a layer structure of (PET film as second base layer) / (thin film made of resin). The thin film made of resin functioned as a cholesteric resin layer.

[0112] The same procedures as in Example 1 were repeated except that the multilayer film was obtained by the above procedure, and the efficiency of forming cracks in the thin film, the efficiency of peeling the thin film, and the shape conformity of the peeled piece were evaluated.

[0113] [Production conditions and results of Examples and Comparative Examples] The production conditions and evaluation results of the peeled pieces of thin film in Examples and Comparative Examples are shown in the table below. The abbreviations in the table have the following meanings. "PET": Polyester (polyethylene terephthalate) film ("Cosmoshine (registered trademark) A4100" manufactured by Toyobo Co., Ltd.) "GL-05": Polyvinyl alcohol (PVA) ("GOHSENOL (registered trademark) GL-05" manufactured by Mitsubishi Chemical Corporation) "CLC": Cholesteric resin layer "RS-1717": Polyvinyl alcohol ("EXCEVAL (registered trademark) RS-1717" manufactured by Kuraray Co., Ltd.) "SD-1000": Polyvinyl alcohol ("Kuraray Poval (registered trademark) SD-1000" manufactured by Kuraray Co., Ltd.) "MP-203": Polyvinyl alcohol ("Kuraray Poval (registered trademark) MP-203" manufactured by Kuraray Co., Ltd.) "RS-2817": Polyvinyl alcohol ("EXCEVAL (registered trademark) RS-2817" manufactured by Kuraray Co., Ltd.) "KH-17": Polyvinyl alcohol ("GOHSENOL (registered trademark) KH-17" manufactured by Mitsubishi Chemical Corporation) "PVA-117": Polyvinyl alcohol ("Kuraray Poval (registered trademark) PVA-117" manufactured by Kuraray Co., Ltd.) "Embossing roll": Means that cracks were formed using roll A and roll B. "Thomson blade": Means that cracks were formed using a Thomson blade. "Still water": Means that the multilayer film on which cracks were formed was gently immersed in water. "Water spray": Means that water was sprayed onto the multilayer film on which cracks were formed.

[0114]

[0115]

[0116]

[0117] In the methods according to the Examples, the crack formation efficiency was evaluated as A or B, which is good. On the other hand, in the method according to Comparative Example 1, the crack formation efficiency was evaluated as C, which is poor. In the methods according to Example 9, in which the saponification degree of the polyvinyl alcohol contained in the water-soluble adhesive is less than 82 mol%, and Examples 8 and 10, in which the saponification degree is more than 93 mol%, the thin film peeling efficiency was evaluated as C. On the other hand, in the methods according to Examples 1 to 7, in which the saponification degree of the polyvinyl alcohol contained in the water-soluble adhesive is 82 mol% or more and 93 mol% or less, the thin film peeling efficiency was evaluated as A or B, which is better than Examples 8 to 10.

Claims

1. Step (1) of preparing a first intermediate laminate including a first base material layer and a thin film provided in contact with the first base material layer; Step (2) of preparing a second intermediate laminate including a second base material layer and a water-soluble adhesive layer provided in contact with the second base material layer; Step (3) of laminating the first intermediate laminate and the second intermediate laminate so that the thin film and the water-soluble adhesive layer face each other to obtain a third intermediate laminate; Step (4) of peeling the first base material layer from the third intermediate laminate to obtain a multilayer film including the second base material layer, the water-soluble adhesive layer provided in contact with the second base material layer, and the thin film provided in contact with the water-soluble adhesive layer; Step (5) of pressing a member having an uneven shape against the thin film side of the multilayer film to form cracks for dividing the thin film into small pieces; Step (6) of bringing the multilayer film having the cracks formed thereon into contact with water to remove the water-soluble adhesive layer from the multilayer film to obtain peeled pieces of the thin film, A method for producing peeled pieces of a thin film, wherein the water-soluble adhesive layer is a layer formed from a water-soluble adhesive mainly composed of polyvinyl alcohol.

2. The method for producing peeled pieces of a thin film according to Claim 1, wherein the saponification degree of the polyvinyl alcohol contained in the water-soluble adhesive is 82 mol% or more and 93 mol% or less.

3. The method for producing peeled pieces of a thin film according to Claim 1, wherein in Step (6), the contact of the multilayer film with water is performed by immersing the multilayer film in water.

4. The method for producing peeled pieces of a thin film according to Claim 1, wherein the formation of the cracks in Step (5) is performed by forming cracks for dividing the thin film into small pieces having the same shape when viewed in the thickness direction of the thin film.

5. The method for producing peeled pieces of a thin film according to Claim 1, wherein the water-soluble adhesive further contains one or more selected from the group consisting of polyacrylamide, polyvinylpyrrolidone, polyvinylamide, carboxymethylcellulose, polyethylene oxide, starch, and protein.