Method for manufacturing a laminated film containing a solvent-free adhesive layer

Abstract

To provide a method for manufacturing a laminated film containing a solvent-free adhesive layer. [Solution] A method for producing a laminated film comprising a solvent-free adhesive layer cured by active energy rays on a base film, the method comprising: (A) applying an active energy ray-curable solvent-free adhesive main component composition onto a release film to form an adhesive main component composition layer; (B) simultaneously or immediately thereafter applying a solvent-free isocyanate composition onto the surface of the adhesive main component composition layer opposite to the release film to form a solvent-free laminate including the adhesive main component composition layer and the isocyanate composition layer; (C) irradiating the surface of the solvent-free laminate on the isocyanate composition layer side with active energy rays to cure and form an adhesive layer; and (D) applying a base film onto the surface of the adhesive layer on the isocyanate composition layer side to obtain a laminated film in which the adhesive layer and the base film are laminated on a release film.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a laminated film containing a solvent-free adhesive layer. In particular, the present invention relates to a method for manufacturing a laminated film with enhanced adhesion, comprising a solvent-free adhesive layer cured by active energy rays on a base film such as a polyvinyl chloride resin film. [Background technology]

[0002] Conventionally, solvent-based adhesives have been used to form an adhesive layer on a base film such as a polyvinyl chloride resin film. Typically, such a solvent-based adhesive layer can be formed by coating a release film (also called a separator) with the solvent-based adhesive, drying it, and then laminating it with the base film. At the point when the solvent-based adhesive layer coated and dried on the release film is laminated with the base film, the solvent-based adhesive has essentially lost its fluidity but is not completely cured. The curing reaction of the solvent-based adhesive is completed after the solvent-based adhesive layer and the base film are laminated and brought into full contact. This is thought to result in adhesion between the solvent-based adhesive layer and the base film due to intermolecular reactions within the adhesive, including reactions caused by curing agents such as isocyanates contained in the adhesive, as well as bonding reactions and anchoring effects between the adhesive and the base film.

[0003] Recently, the development of solvent-free active energy ray-curable adhesives has been progressing due to several advantages, including their ability to be cured with low integrated light intensity using active energy rays such as ultraviolet light, resulting in high energy efficiency; their ability to not become cloudy even in high-temperature and high-humidity environments, making them suitable for applications requiring high transparency; and their low environmental impact. Conventional technologies related to such solvent-free active energy ray-curable adhesives include, for example, Patent Document 1 and Patent Document 2. Patent Document 1 discloses a method for manufacturing an optical member, which includes the steps of forming a printed layer on one side of a substrate and applying an active energy ray-curable adhesive to the side of the substrate having the printed layer to form an adhesive layer. Patent Document 2 discloses a solvent-free adhesive composition containing an acrylic resin having a specific structure and a specific range of glass transition temperatures. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2014-214280 [Patent Document 2] Japanese Patent Publication No. 2020-076097 [Overview of the project] [Problems that the invention aims to solve]

[0005] Industrially, active energy curable solvent-free adhesives are primarily used in the processing of OCAs (optical clear adhesives), often as non-carrier (substrate-less) films. The materials to which such OCAs are laminated are generally thin, rigid sheets such as optical glass, and depending on the application, processing in an autoclave (pressure degassing device) is performed for lamination. For this reason, there has been little active research to improve the adhesion of such active energy curable solvent-free adhesives to film substrates, such as relatively flexible polyvinyl chloride (PVC) resin films.

[0006] To form an active energy curable solvent-free adhesive on a substrate, one possible method involves first coating the active energy curable solvent-free adhesive onto a release film (separator), then completely curing it with active energy rays such as ultraviolet light to form an adhesive layer, and finally laminating the cured adhesive layer onto a substrate film such as a polyvinyl chloride resin film. However, this method has the disadvantage that, because the adhesive layer hardly deforms upon contact, the adhesive layer and the substrate film do not adhere well, and the bonding reaction and anchoring effect between the adhesive and the substrate film do not develop sufficiently, resulting in insufficient adhesion between the adhesive layer and the substrate film.

[0007] Therefore, in view of the shortcomings of the conventional technology, the first object of the present invention is to provide a novel method for manufacturing a laminated film having a solvent-free adhesive layer on a base film. Furthermore, a further object of the present invention is to provide a method for manufacturing a laminated film with enhanced adhesion, comprising a solvent-free adhesive layer cured by active energy rays on a base film such as a polyvinyl chloride resin film. [Means for solving the problem]

[0008] As a result of diligent research, the inventors have developed a novel manufacturing method in which a layer of solvent-free active energy ray-curable adhesive main component composition is first applied to a release film, and simultaneously or immediately thereafter, a solvent-free isocyanate composition is applied to the adhesive main component composition layer, and then the mixture is irradiated with active energy rays to cure it and form an adhesive layer, after which a base film is applied to obtain a laminated film. Furthermore, the inventors have found that this novel manufacturing method for laminated films can improve the adhesion between the adhesive layer and the base film, thus completing the present invention.

[0009] A key aspect of the present invention for achieving the above objectives, and preferred embodiments relating thereto, are summarized below. [1]. A method for producing a laminated film comprising a solvent-free adhesive layer cured by active energy rays on a base film, (A) A step of forming an adhesive main composition layer by applying an active energy ray curable adhesive main composition containing an acrylic resin binder and free of solvents onto a release film. (B) Simultaneously with or immediately after step (A), an isocyanate composition containing an isocyanate but free of solvents is applied to the surface of the adhesive main component composition layer obtained in step (A) opposite to the release film, thereby forming a solvent-free laminate comprising an adhesive main component composition layer and an isocyanate composition layer. (C) A step of forming an adhesive layer, which is a cured product of the solvent-free laminate, by irradiating the surface of the isocyanate composition layer side of the solvent-free laminate obtained in step (B) with active energy rays and curing it, and (D) A process to obtain a laminated film in which the adhesive layer, which is the cured product of the solvent-free laminate obtained in step (C), and the substrate film are laminated in this order on a release film by applying the substrate film to the surface of the adhesive layer, which is the cured product of the solvent-free laminate, on the isocyanate composition layer side. A method that includes this. [2]. The method according to item [1] above, wherein the base film is a polyvinyl chloride resin film. [3]. The method according to item [1] or [2] above, wherein the thickness of the isocyanate composition layer of the solvent-free laminate formed in step (B) is 20% or less of the thickness of the adhesive main component composition layer. [4]. The thickness of the adhesive main composition layer formed in step (A) is 20 μm or more and 100 μm or less. The thickness of the isocyanate composition layer formed in step (B) is 0.5 μm or more and 15 μm or less. The method described in any one of the above items [1] to [3]. [5]. Using a two-layer die, simultaneously performing steps (A) and (B), and forming a solventless laminate by laminating an adhesive base composition layer and an isocyanate composition layer together on a release film, the method according to any one of the above items [1] to [4]. [6]. The method according to any one of the above items [1] to [5], wherein the active energy ray-curable adhesive composition contains a (meth)acrylate having an alkyl ester group with 1 to 12 carbon atoms as an acrylic resin binder and further contains a polymerization initiator. [7]. The method according to any one of the above items [1] to [6], wherein the isocyanate composition contains a (meth)acryloyl group-containing isocyanate compound as an isocyanate and a (meth)acrylate having an alkyl ester group with 1 to 12 carbon atoms as an acrylic resin binder. [Advantages of the Invention]

[0010] According to the above aspect of the present invention, a novel method not found in the prior art for manufacturing a laminated film provided with a solventless adhesive layer is provided. By the above manufacturing method, since it is solventless, the environmental load is small, and furthermore, the adhesion between the adhesive layer and the base film can be sufficiently enhanced. [Brief Description of the Drawings]

[0011] [Figure 1] FIG. 1 is a drawing illustrating an outline of each step in a method for manufacturing a laminated film according to an embodiment of the present invention. [Embodiments for Carrying Out the Invention]

[0012] The method for manufacturing a laminated film according to a main aspect of the present invention includes the following steps: (A) A step of forming an adhesive base composition layer by applying an active energy ray-curable adhesive base composition containing an acrylic resin binder and not containing a solvent on a release film. (B) Simultaneously with or immediately after step (A), an isocyanate composition containing an isocyanate but free of solvents is applied to the surface of the adhesive main component composition layer obtained in step (A) opposite to the release film, thereby forming a solvent-free laminate comprising an adhesive main component composition layer and an isocyanate composition layer. (C) A step of forming an adhesive layer, which is a cured product of the solvent-free laminate, by irradiating the surface of the isocyanate composition layer side of the solvent-free laminate obtained in step (B) with active energy rays and curing it, and (D) A step in which a base film is applied to the surface on the isocyanate composition layer side of the adhesive layer, which is the cured product of the solvent-free laminate obtained in step (C), thereby obtaining a laminated film in which the adhesive layer, which is the cured product of the solvent-free laminate, and the base film are laminated in this order on a release film. The following sections will explain each step.

[0013] <Process (A)> The acrylic resin in the acrylic resin binder contained in the active energy ray curable adhesive main composition used in step (A) may be any known acrylic resin. In this specification, the term "acrylic" is intended to encompass both acrylic and methacrylic.

[0014] Examples of acrylic resins constituting the acrylic resin binder are not particularly limited, but include (meth)acryloyl group-containing prepolymers or oligomers such as polyurethane (meth)acrylate, polyester (meth)acrylate, polyacrylic (meth)acrylate, epoxy (meth)acrylate, polyalkylene glycol poly(meth)acrylate, and polyether (meth)acrylate; methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, hexyl (meth)acrylate t, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, phenyl (meth)acrylate, phenyl cellosolve (meth)acrylate, 2-methoxyethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-acryloyloxyethyl hydrogen phthalate, dimethylaminoethyl (meth)acrylate, (Meth)acryloyl group-containing monofunctional reactive monomers such as trifluoroethyl (meth)acrylate and trimethylsiloxyethyl methacrylate; diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 2,2'-bis(4-(meth)acryloyloxypolyethyleneoxyphenyl)propane, and 2,2'-bis(4-(meth)acryloyloxypolypropyleneoxyphenyl) Examples of resins include those comprising one or more monomers selected from the following: (meth)acryloyl group-containing bifunctional reactive monomers such as (nyl)propane; (meth)acryloyl group-containing trifunctional reactive monomers such as trimethylolpropane tri(meth)acrylate and trimethylolethane tri(meth)acrylate; (meth)acryloyl group-containing tetrafunctional reactive monomers such as pentaerythritol tetra(meth)acrylate; and (meth)acryloyl group-containing hexafunctional reactive monomers such as dipentaerythritol hexaacrylate.As for the acrylic resin, one of these resins can be used alone or in the form of a mixture of two or more.

[0015] Among these, a preferred example of an acrylic resin constituting an acrylic resin binder is a resin whose constituent monomer is one or more (meth)acrylic acid esters having alkyl ester groups having 1 to 12 carbon atoms. The (meth)acrylic acid ester may more preferably be a (meth)acrylic acid ester having alkyl ester groups having 1 to 10 carbon atoms, a (meth)acrylic acid ester having alkyl ester groups having 1 to 8 carbon atoms, a (meth)acrylic acid ester having alkyl ester groups having 1 to 6 carbon atoms, or a (meth)acrylic acid ester having alkyl ester groups having 1 to 4 carbon atoms. The (meth)acrylic acid ester may preferably contain methyl (meth)acrylate or ethyl (meth)acrylate.

[0016] The mass-average molecular weight of the acrylic resin constituting the acrylic resin binder is usually 10,000 or more, preferably 20,000 or more, 30,000 or more, or 60,000 or more, from the viewpoint of imparting appropriate hardness to the adhesive and preventing peeling and gaps. On the other hand, the mass-average molecular weight of the acrylic resin is usually 2 million or less, preferably 1.5 million or less, or 1 million or less, from the viewpoint of coating properties. In this specification, the mass-average molecular weight is determined using gel permeation chromatography (GPC). GPC measurement is performed using Showa Denko Corporation's high-performance liquid chromatography system "SHODEX GPC-101" (product name) and a styrene-divinylbenzene copolymer column (exclusion limit 2 × 10⁻⁶). 8 The column and exclusion limit are 2 × 10 4 Each column is connected to the other. The measurement can be performed using the following conditions: measurement temperature 40°C, flow rate 1 mL / min, mobile phase: tetrahydrofuran (THF) for high-performance liquid chromatography, and sample concentration 1 mg / mL. A molecular weight calibration curve can be prepared using standard polystyrene.

[0017] The active energy ray-curable adhesive main component composition used in process (A) may contain other resin binders in addition to the acrylic resin binder. Examples of resin binders that can be used in combination with the acrylic resin binder are, but are not limited to, rubber-based adhesives such as natural rubber and butyl isoprene rubber; polyurethane-based adhesives other than acrylic resins; polyester-based adhesives other than acrylic resins; polystyrene-based adhesives; and mixtures of one or more types of silicone-based adhesives. When the adhesive main component composition contains other resin binders in addition to the acrylic resin binder, the mass ratio of the acrylic resin binder based on the total mass of the acrylic resin binder and the other resin binders may be 50% by mass or more, preferably 60% by mass or more, 70% by mass or more, or 80% by mass or more.

[0018] The active energy ray-curable adhesive main component composition used in step (A) is solvent-free. In this specification, "solvent-free" means that the mass percentage of solvent relative to the total amount of the substance is less than 1% by mass, preferably 0.5% by mass or less, more preferably 0.1% by mass or less, and may be substantially 0% by mass. Furthermore, the term "solvent" here includes any known solvent. Examples of solvents, though not particularly limited, include 1-methoxy-2-propanol, ethyl acetate, n-butyl acetate, toluene, methyl ethyl ketone, methyl isobutyl ketone, diacetone alcohol, and acetone. In other words, the active energy ray-curable adhesive main component composition used in step (A) does not contain any of these known solvents.

[0019] The active energy ray-curable adhesive main composition used in step (A) may further contain optional components other than the resin binder, as desired, to the extent that they do not contradict the objectives of the present invention. Examples of such optional components include flame retardants, photopolymerization initiators, antistatic agents, surfactants, leveling agents, thixotropic agents, anti-fouling agents, printability improvers, antioxidants, weather-resistant stabilizers, light-resistant stabilizers, ultraviolet absorbers, heat stabilizers, pigments, and fillers. The amount of the optional components (if used) is not particularly limited, but is usually about 0.01 to 10 parts by mass per 100 parts by mass of the total adhesive main composition.

[0020] Any known release film can be used to which the adhesive main component composition is applied in step (A). Examples of release films, though not particularly limited, include films formed from one or more polyester resins such as polyethylene terephthalate resin (PET), glycol-modified polyethylene terephthalate resin (PETG), polybutylene terephthalate resin (PBT), polytrimethylene terephthalate resin (PTT), polyhexamethylene terephthalate resin (PHT), copolymer polyethylene terephthalate / isophthalate resin (PET / PEI); films formed from one or more polyolefin resins such as polyethylene and polypropylene; films formed from silicone resins; fluororesin films; paper films; and others. The release film may also be a laminate of two or more of these resin films.

[0021] The thickness of the release film is not particularly limited, but from the viewpoint of balancing the workability of laminated film formation and manufacturing costs, it may, for example, be typically 10 μm to 500 μm. Preferably, the thickness of the release film may be 15 μm to 300 μm, or 20 μm to 200 μm.

[0022] In step (A), the thickness of the adhesive main component composition layer formed by application to the release film is not particularly limited, but from the viewpoint of providing sufficient adhesion between the laminated film with the adhesive layer and the object to be adhered, and the handling of the article after bonding by the adhesive layer, it may usually be 20 μm to 100 μm. The thickness of the adhesive main component composition layer is preferably 25 μm to 95 μm, more preferably 30 μm to 90 μm, 35 μm to 85 μm, or 40 μm to 80 μm.

[0023] The conditions under which the adhesive main component composition is applied in step (A) are not particularly limited. The adhesive main component composition can usually be applied at room temperature and atmospheric pressure. The temperature at which the adhesive main component composition is applied may be, for example, 5°C to 50°C, 10°C to 45°C, or 15°C to 40°C. The pressure at which the adhesive main component composition is applied is usually normal pressure, i.e., atmospheric pressure, but application under a predetermined reduced pressure or predetermined pressurized pressure may also be employed.

[0024] In step (A), the method for applying the adhesive main component composition onto the release film is not particularly limited and may be any known method. Examples of application methods for the adhesive main component composition are not limited to roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, and die coating.

[0025] <Process (B)> Any known isocyanate may be used in the isocyanate composition used in step (B). The isocyanate may be a compound having one isocyanate group (-N=C=O) per molecule, or a compound having two or more isocyanate groups (-N=C=O) per molecule.

[0026] Examples of compounds having one isocyanate group (-N=C=O) in one molecule include 2-(acryloyloxy)ethyl isocyanate and 2-(methacryloyloxy)ethyl isocyanate. Examples of compounds having two or more isocyanate groups (-N=C=O) in one molecule include methylenebis-4-cyclohexyl isocyanate; polyisocyanates such as trimethylolpropane adduct of tolylene diisocyanate, trimethylolpropane adduct of hexamethylene diisocyanate, trimethylolpropane adduct of isophorone diisocyanate, isocyanurate of tolylene diisocyanate, isocyanurate of hexamethylene diisocyanate, isocyanurate of isophorone diisocyanate, biuret of hexamethylene diisocyanate, and urethane crosslinking agents such as blocked isocyanates of the above polyisocyanates. A suitable example of an isocyanate is hexamethylene diisocyanate. As the isocyanate, one or a mixture of two or more of these can be used.

[0027] From the viewpoint of imparting appropriate hardness to the adhesive layer and preventing peeling and gaps, compounds having two or more isocyanate groups (-N=C=O) in one molecule can be preferably used. Furthermore, when applying and crosslinking the isocyanate composition, catalysts such as dibutyltin dilaurate and dibutyltin diethylhexoate may be added to the isocyanate composition as needed.

[0028] The isocyanate composition used in process (B) is solvent-free. The definition of "solvent-free" is as described above. According to this manufacturing method, since neither the active energy ray-curable adhesive main component composition in step (A) nor the isocyanate composition in step (B) contains solvents, the environmental impact is low, and the adhesion between the adhesive layer and the substrate film can be sufficiently enhanced. In addition, it can be cured with low integrated light intensity using active energy rays such as ultraviolet light, resulting in high energy efficiency, and it does not become cloudy even in high temperature and high humidity environments, making it suitable for applications requiring high transparency.

[0029] The isocyanate composition used in step (B) may partially contain an acrylic resin binder or another resin binder. The resin constituting the acrylic resin binder or the other resin binder is not particularly limited, but resins similar to those exemplified above for step (A) can be used. When the isocyanate composition contains an acrylic resin binder or another resin binder, the mass ratio of resin binder to isocyanate in the entire isocyanate composition may be typically 99.9:0.1 to 90:10, preferably 99.5:0.5 to 95:5, or 99:1 to 97:3, from the viewpoint of balancing improved curability with ease of storage and handling.

[0030] The isocyanate composition used in step (B) may further contain optional components other than isocyanate, as desired, to the extent that it does not contradict the objectives of the present invention. Examples of such optional components include flame retardants, photopolymerization initiators, antistatic agents, surfactants, leveling agents, thixotropic agents, anti-fouling agents, printability improvers, antioxidants, weather-resistant stabilizers, light-resistant stabilizers, ultraviolet absorbers, heat stabilizers, pigments, and fillers. The amount of the optional components (if used) is not particularly limited, but is usually about 0.01 to 10 parts by mass, based on 100 parts by mass of the total isocyanate composition.

[0031] In step (B), the timing of applying the isocyanate composition to the surface of the adhesive main component layer obtained in step (A) opposite to the release film may be either simultaneously with step (A) or immediately afterward. If the isocyanate composition is applied immediately after step (A), it must be before the intermolecular reaction of the adhesive main component composition begins or progresses. Depending on the components and amounts used for each composition, if the isocyanate composition is applied immediately after step (A), it is preferable to complete the application of the isocyanate composition within, for example, 1 minute, 3 minutes, 5 minutes, or 10 minutes after the formation of the adhesive main component layer by the application of the adhesive main component composition in step (A) is completed.

[0032] The conditions under which the isocyanate composition is applied in step (B) are not particularly limited. The isocyanate composition can usually be applied at room temperature and atmospheric pressure. The temperature at which the isocyanate composition is applied may be, for example, 5°C to 50°C, 10°C to 45°C, or 15°C to 40°C. The pressure at which the isocyanate composition is applied is usually normal pressure, i.e., atmospheric pressure, but application under a predetermined reduced pressure or predetermined pressurized pressure may also be employed.

[0033] The method for applying the isocyanate composition in step (B) is not particularly limited and may be any known method. Examples of application methods for isocyanate compositions are not limited to those described above, but include roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, and die coating.

[0034] When performing steps (A) and (B) simultaneously to form a solvent-free laminate by laminating an adhesive main composition layer and an isocyanate composition layer together on a release film, a preferred embodiment is the use of a two-layer die (two-layer die coater). The two-layer die is not particularly limited, and any known die can be used. A two-layer die typically comprises an upper and a lower fitting, each having a corresponding manifold and die slit. The material extruded from each of the two die slits of the two-layer die can form two layers (in the present invention, a tack main composition layer and an isocyanate composition layer).

[0035] In step (B), the thickness of the isocyanate composition layer formed by applying it to the surface of the adhesive main component composition layer opposite to the release film is not particularly limited, but from the viewpoint of sufficiently improving the adhesion between the adhesive layer, which is the cured product of the solvent-free laminate comprising the adhesive main component composition layer and the isocyanate composition layer, and the substrate film, and preventing delamination between these layers, it is preferably 0.5 μm to 15 μm. The thickness of the isocyanate composition layer here is substantially equal to the thickness of the layer included in the laminated film when the laminated film is completed by the execution of step (D). The thickness of the isocyanate composition layer is more preferably 0.55 μm to 14 μm, 0.6 μm to 13 μm, 0.65 μm to 12 μm, 0.7 μm to 11 μm, or 0.8 μm to 10 μm.

[0036] Furthermore, similarly to the above, in order to sufficiently improve the adhesion between the adhesive layer, which is a cured product of a solvent-free laminate comprising an adhesive main composition layer and an isocyanate composition layer, and the substrate film, and to prevent delamination between these layers, the thickness of the isocyanate composition layer of the solvent-free laminate formed in step (B) may preferably be 20% or less of the thickness of the adhesive main composition layer. More preferably, the thickness of the isocyanate composition layer of the solvent-free laminate may be 18% or less, 16% or less, 14% or less, 12% or less, or 10% or less of the thickness of the adhesive main composition layer.

[0037] <Process (C)> In step (C), the active energy rays irradiated onto the isocyanate composition layer side of the solvent-free laminate obtained in step (B) are not particularly limited, as long as it is possible to cure the solvent-free laminate and form the adhesive layer which is the cured product. The active energy rays may be, for example, light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, and infrared rays, electromagnetic waves such as X-rays and gamma rays, as well as electron beams, proton beams, neutron beams, etc. In this context, "curing" refers to a state in which the intermolecular reactions of resin binders, such as acrylic resin binders, that constitute the adhesive main component composition layer in the solvent-free laminate, and the reactions between the resin binders, such as acrylic resin binders, that constitute the adhesive main component composition layer and the isocyanates that constitute the isocyanate composition layer, have substantially all proceeded or been completed.

[0038] The active energy ray may preferably be ultraviolet light, from the viewpoint of curing speed, availability of irradiation equipment, and cost. When irradiating with ultraviolet light as the active energy ray, high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, metal halide lamps, xenon lamps, chemical lamps, electrodeless discharge lamps, LED lamps, etc., which emit ultraviolet light in the wavelength range of 150 to 450 nm can be used.

[0039] In a preferred embodiment, when ultraviolet light is used as the active energy ray, a nitrogen gas purge may be performed prior to and / or during ultraviolet irradiation to prevent the curing reaction caused by ultraviolet irradiation from being inhibited (so-called oxygen inhibition) by the reaction of radicals generated in the binder resin by ultraviolet irradiation with oxygen molecules in the atmosphere. Nitrogen gas can be substituted with other inert gases. The means for introducing nitrogen gas may be integrated with the ultraviolet irradiation means or provided separately.

[0040] The integrated amount of active energy radiation irradiated in process (C) is not particularly limited, but from the viewpoint of sufficiently curing the solvent-free laminate and reliably forming the adhesive layer, as well as from the viewpoint of preventing yellowing and suppressing manufacturing costs, it is usually 100 mJ / cm². 220000 mJ / cm or less 2 It may be the following. The integrated light quantity of the active energy rays is preferably 200 mJ / cm 2 or more and 15000 mJ / cm 2 or less, 300 mJ / cm 2 or more and 10000 mJ / cm 2 or less, 400 mJ / cm 2 or more and 7000 mJ / cm 2 or less, or 500 mJ / cm 2 or more and 5000 mJ / cm 2 It may be the following.

[0041] <Step (D)> In step (D), by applying a base film onto the surface on the isocyanate composition layer side of the adhesive layer, which is a cured product of the solvent-free laminate obtained in step (C), a laminated film in which the adhesive layer, which is a cured product of the solvent-free laminate, and the base film are laminated in this order is obtained on the release film.

[0042] After the laminated film is obtained in step (D), pressure can be applied from both sides of the laminated film. Pressurization to such an extent that it does not substantially affect the thickness of the cured adhesive main agent layer is acceptable. For example, the range of the pressure when pressurization is performed may be 0.05 MPa or more and 5 MPa or less, preferably 0.05 MPa or more and 3 MPa or less or 0.05 MPa or more and 1 MPa or less.

[0043] After applying the base film onto the surface of the adhesive layer, an aging treatment may be performed. The characteristics of the laminated film can be stabilized by the aging treatment. The conditions of the aging treatment are not particularly limited. The temperature of the above aging treatment is usually about 15 to 100 °C, preferably 20 to 80 °C. Typically, the above aging treatment may be performed at room temperature (usually about 15 °C to 35 °C). The time of the above aging treatment may be, for example, about 3 minutes to 1 week, or about 5 minutes to 3 days.

[0044] The base film that can be used in process (D) is not particularly limited, but examples include polyvinyl chloride resins; polyester resins such as aromatic polyesters and aliphatic polyesters; acrylic resins; polycarbonate resins; poly(meth)acrylimide resins; polyolefin resins such as polyethylene, polypropylene, and poly-4-methylpentene-1; cellulose resins such as cellophane, triacetylcellulose, diacetylcellulose, and acetylcellulose butyrate; styrene resins such as polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS resin), styrene-ethylene-butadiene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, and styrene-ethylene-ethylene-propylene-styrene copolymer; polyvinylidene chloride resins; fluorine-containing resins such as polyvinylidene fluoride; and other resin films such as polyvinyl alcohol, ethylene vinyl alcohol, polyetheretherketone, nylon, polyamide, polyimide, polyurethane, polyetherimide, polysulfone, and polyethersulfone. These films include unoriented films, uniaxially oriented films, and biaxially oriented films. They also include laminated films obtained by laminating two or more layers of one or more of these types. Furthermore, these films may be transparent, opaque, opaque, colored, or have a specific color. In another embodiment, the base film may be a film formed from cellophane film, silicone rubber film, fabric-containing film, glass film, wood powder-containing film, etc., instead of the resin film described above.

[0045] In one preferred embodiment, the base film used for step (D) may be a polyvinyl chloride resin film. Examples of polyvinyl chloride resins used as materials for polyvinyl chloride resin films include polyvinyl chloride (polyvinyl chloride homopolymer); vinyl chloride-vinyl acetate copolymer, vinyl chloride-(meth)acrylic acid copolymer, vinyl chloride-methyl (meth)acrylate copolymer, vinyl chloride-(meth)acrylate copolymer, vinyl chloride-ethyl (meth)acrylate copolymer, vinyl chloride-maleic acid ester copolymer, vinyl chloride-ethylene copolymer, vinyl chloride-propylene copolymer, vinyl chloride-styrene copolymer, vinyl chloride-isobutylene copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-styrene-maleic anhydride terpolymer, vinyl chloride-styrene-acrylonitrile terpolymer, vinyl chloride-butadiene copolymer, vinyl chloride-isoprene copolymer, vinyl chloride-chlorinated propylene copolymer, vinyl chloride-vinylidene chloride-vinyl acetate terpolymer, vinyl chloride-acrylonitrile copolymer, vinyl chloride-various vinyl ether copolymers, and other vinyl chloride copolymers of vinyl chloride and other monomers copolymerizable with vinyl chloride; and modified (chlorinated, etc.) polyvinyl chloride or vinyl chloride copolymers such as post-chlorinated vinyl copolymers. Furthermore, chlorinated polyolefins, such as chlorinated polyethylene, which have a chemical structure similar to that of polyvinyl chloride, may also be used. Such chlorinated polyolefins with a chemical structure similar to that of polyvinyl chloride are also considered to fall under the category of "polyvinyl chloride resins" that constitute the layers of the polyvinyl chloride resin film. One or more of these can be used as the polyvinyl chloride resin.

[0046] The polyvinyl chloride resin used as a material for the polyvinyl chloride resin film may further contain other resins commonly used in polyvinyl chloride resin compositions. The proportion of the other resins is not particularly limited as long as it does not contradict the objectives of the present invention, but the total of the polyvinyl chloride resin and the other resins is typically 0 to 40% by mass, preferably 0 to 30% by mass, and more preferably 5 to 25% by mass.

[0047] Other resins such as core-shell rubbers include, for example, ethylene-vinyl acetate copolymer; ethylene-(meth)acrylic acid copolymer; ethylene-methyl (meth)acrylate copolymer; ethylene-ethyl (meth)acrylate copolymer; (meth)acrylic acid ester-alkyl acrylate copolymer; methacrylic acid ester-styrene / butadiene rubber graft copolymer; acrylonitrile-styrene / butadiene rubber graft copolymer; acrylonitrile-styrene / ethylene-propylene rubber graft copolymer; acrylonitrile-styrene / acrylic acid ester graft copolymer; methacrylic acid ester / acrylic acid ester rubber graft copolymer; and methacrylic acid ester-acrylonitrile / acrylic acid ester rubber graft copolymer. Other resins that can be used include one or more of these mixtures.

[0048] Furthermore, the polyvinyl chloride resin used as a material for the polyvinyl chloride resin film may further contain plasticizers commonly used in polyvinyl chloride resin compositions. The amount of plasticizer added is usually 100 parts by mass or less, preferably 10 to 30 parts by mass, and more preferably 15 to 25 parts by mass, based on a total of 100 parts by mass of the polyvinyl chloride resin and the other resins mentioned above.

[0049] Examples of plasticizers include phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid ester plasticizers, adipic acid ester plasticizers, itaconic acid ester plasticizers, citrate ester plasticizers, cyclohexane dicarboxylate plasticizers, and epoxy plasticizers. One or more of these plasticizers can be used.

[0050] Examples of plasticizers include polyester-based plasticizers that use polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-hexanediol, 1,6-hexanediol, and neopentyl glycol, and polyhydric carboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, trimellitic acid, pimelic acid, suberic acid, maleic acid, azelaic acid, sebacic acid, fumaric acid, phthalic acid, isophthalic acid, and terephthalic acid, and optionally monohydric alcohols and monocarboxylic acids as stoppers.

[0051] Examples of phthalate ester plasticizers include dibutyl phthalate, butylhexyl phthalate, diheptyl phthalate, di(2-ethylhexyl) phthalate, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, ditridecyl phthalate, dilauryl phthalate, dicyclohexyl phthalate, and dioctyl terephthalate.

[0052] Examples of trimellitic acid ester plasticizers include tri(2-ethylhexyl) trimellitate, tri(n-octyl) trimellitate, and tri(isononyl) trimellitate.

[0053] Examples of adipic acid ester plasticizers include bis(2-ethylhexyl) adipate, dioctyl adipate, diisononyl adipate, and diisodecyl adipate.

[0054] Examples of epoxy plasticizers include epoxidized soybean oil, epoxidized linseed oil, epoxidized fatty acid octyl esters, and epoxidized fatty acid alkyl esters.

[0055] Other examples of plasticizers include tetrahydrophthalate diester plasticizers, glycerin ester plasticizers, epoxyhexahydrophthalate diester plasticizers, isosorbide diester plasticizers, phosphate plasticizers, azelaic acid plasticizers, sebaciate plasticizers, stearic acid plasticizers, biphenyltetracarboxylic acid ester plasticizers, polyester plasticizers, and chlorine-based plasticizers.

[0056] Furthermore, the polyvinyl chloride resin used as the material for the polyvinyl chloride resin film may contain other substances commonly used in polyvinyl chloride resin compositions, to the extent that they do not contradict the objectives of the present invention. Optional components that may be included include pigments, inorganic fillers, organic fillers, resin fillers; lubricants, antioxidants, weather stabilizers, heat stabilizers, processing aids, reinforcing agents, nucleating agents, mold release agents, antistatic agents, urea-formaldehyde wax, and surfactants. The amount of these optional components is typically about 0.01 to 50 parts by mass when the total amount of the polyvinyl chloride resin and the other resins is 100 parts by mass.

[0057] The thickness of the base film, such as a polyvinyl chloride resin film, is not particularly limited, but from the viewpoint of workability in forming the laminated film and the application of the final product, it may, for example, be typically 20 μm to 3000 μm. Preferably, the thickness of the base film may be 40 μm to 2000 μm, 60 μm to 1000 μm, 70 μm to 800 μm, 80 μm to 700 μm, 90 μm to 600 μm, or 100 μm to 500 μm.

[0058] On the side of the base film, such as a polyvinyl chloride resin film, opposite to the adhesive layer-forming side (the side that is visible after the laminated film is applied to the substrate via the adhesive layer), any additional layer, such as a printed layer, may be provided as desired. Alternatively, any additional layer, such as a transparent resin film layer and a protective coating layer, may be provided on top of or in place of the printed layer. When such additional layers are provided, the normal and preferred range of the total thickness of the base film and the additional layer can be determined by the same method described above for the thickness of the base film.

[0059] <Explanation using Figure 1> By referring to Figure 1, which illustrates the outline of each step in the method for manufacturing a laminated film according to one embodiment of the present invention, the method can be understood more easily and visually. This illustration is merely illustrative of a typical form and is not intended to limit the present invention.

[0060] In Figures 1(a) to 1(b), an active energy ray-curable adhesive main component composition 1 containing an acrylic resin binder and no solvent, and an isocyanate composition 2 containing an isocyanate and no solvent, are pressure-fed through the two slits of a two-layer die 3 in the same direction as indicated by the dotted arrows, and are simultaneously extruded. By simultaneously extruding these two compositions onto the surface of the release film 4, a solvent-free laminate of the adhesive main component layer 1x and the isocyanate composition layer 2x is formed. The isocyanate composition layer 2x side of this solvent-free laminate 5 is irradiated with ultraviolet (UV) light, which is an active energy ray, to perform a curing reaction. Then, in Figure 1(c), the base film 6 is applied to the surface of the isocyanate composition layer 2y side of the adhesive layer 5y, which is the cured product of the solvent-free laminate, thereby obtaining the cured product of the solvent-free laminate on the release film 4. As a result, a laminated film is obtained in which the adhesive layer 5y, which is the cured product of the solvent-free laminate, and the base film 6 are laminated in this order on the release film 4. Although not intended to be constrained by theory, in this laminated film 10, the reaction between the resin binder and the isocyanate proceeds reliably near the interface between the adhesive main composition layer 1y and the isocyanate composition layer 2y in the adhesive layer 5y, and substantially throughout the isocyanate composition layer 2y, which is sufficiently thinner than the adhesive main composition layer 1y. Furthermore, it is believed that high adhesion is obtained by combining these reactions with the interlayer reaction between these and the substrate film surface.

[0061] <Laminated film> The preferred range of adhesive strength of the adhesive layer of the laminated film obtained by the manufacturing method of each embodiment described above can be appropriately determined depending on the material of the adherend. For example, when the adhesive layer is attached to a resin-based substrate such as a glass substrate, a metal substrate such as SUS, a polycarbonate plate, a polymethyl methacrylate plate, or a PET sheet with an ITO layer deposited on it, the adhesive strength may preferably be 8 to 100 N / 25 mm, and more preferably 15 to 80 N / 25 mm, 20 to 70 N / 25 mm, 25 to 60 N / 25 mm, or 30 to 50 N / 25 mm. As a method for measuring adhesive strength, for example, at a temperature of 23°C, after applying an adhesive layer to a 3mm thick glass plate and waiting for 24 hours or more, the 180° peel-off adhesive strength (unit: N / 25mm) can be measured according to JIS A5759:2016, 6.9 Adhesion Test.

[0062] The laminated films (with the release film removed) obtained by the manufacturing methods of each of the above embodiments may preferably have a haze of 3% or less, more preferably 2.5% or less, 2% or less, 1.5% or less, or 1% or less, when applied to substrates where high transparency and colorlessness are required. The haze here can be measured using the NDH4000 turbidimeter (product name) manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with JIS K7136:2000.

[0063] The laminated films (with the release film removed) obtained by the manufacturing methods of each of the above embodiments may preferably have a yellowness index (YI) of 5 or less, more preferably 4 or less, 3 or less, 2 to -2, or 1 to -1, when used for applications where high transparency and colorlessness are required. The yellowness index here can be measured according to JIS K7105:1981. As a colorimeter, for example, the "SolidSpec-3700" (product name) colorimeter from Shimadzu Corporation can be used.

[0064] The laminated film (with the release film removed) obtained by the manufacturing method of each of the above embodiments may preferably have a total light transmittance of 85% or more, more preferably 88% or more, 90% or more, or 92% or more, when used for applications where high transparency and colorlessness are required. The total light transmittance here can be measured in accordance with JIS K7361-1:1997. As a turbidimeter, for example, the "NDH4000" (product name) turbidimeter from Nippon Denshoku Industries Co., Ltd. can be used.

[0065] The laminated films obtained by the manufacturing methods of each embodiment described above are not particularly limited, but can be used in a wide range of applications, such as labels for various substrates such as plastic, glass, cardboard, and metal; outer packaging materials for filling food, detergents, pharmaceuticals, etc.; decorative members for signs and window glass; wrapping members for vehicles such as cars and buses; advertising members for floors and walls; and protective films for touch panels and image display devices of smartphones and tablet devices. In particular, laminated films with polyvinyl chloride resin film as the base film, when attached to a steel plate, are used for building exteriors such as entrance doors and shutter cases, building interiors such as building interior wall materials and elevator interiors, electrical equipment components such as refrigerators and lighting fixtures, vehicle components such as trucks and ships, and daily necessities and office equipment such as bathroom scales and vending machines. Furthermore, laminated films with polyvinyl chloride resin film as the base film are used for decorative purposes such as wallpaper and decorative films, stationery decoration such as desk mats and notebook covers, furniture decoration such as tablecloths and shower curtains, industrial applications such as partitions and waterproof sheets, decorative purposes for miscellaneous goods such as furoshiki (wrapping cloths), car seat decoration, reception sofa decoration, and vinyl leather decoration for office and lobby chairs. [Examples]

[0066] The present invention will be described in more detail below with reference to examples. These embodiments should be understood as merely illustrative examples and not as limiting the present invention in any way.

[0067] Methods for measuring and evaluating physical properties (i) Adhesion As described below, the obtained laminated film was cut to a length of 200 mm and a width of 25 mm. After removing the release paper, a test piece was prepared by folding back 1 mm from both ends in the longitudinal direction. This test piece was folded back approximately in the center in the longitudinal direction, and the adhesive layers were bonded together. The two adhesive surfaces were firmly pressed together three times with a plastic squeegee to ensure sufficient adhesion. After 5 minutes, the folded ends in the longitudinal direction were held, and the two adhesive surfaces were quickly separated. The adhesion between the adhesive layer and the base film was evaluated from the state of the adhesive surface after this separation. ○: No peeling of the adhesive layer from the base film was observed. △: When peeled off, one adhesive layer peeled off from the base film over an area of ​​less than 20% and migrated to the other adhesive layer. ×: When peeled off, one adhesive layer peeled off from the base film over an area of ​​more than 20% and migrated to the other adhesive layer.

[0068] (b) Adhesion As described below, the obtained laminated film was cut to a length of 250 mm and a width of 25 mm, and the 180° peel-off adhesion strength to a 3 mm thick glass plate was measured according to JIS A5759:2016 6.9 Adhesion Test under standard conditions (temperature 23℃±1℃, humidity 50%±5%).

[0069] Raw materials used (α) Substrate film (α-1)TM3436A: Polyvinyl chloride resin film manufactured by Riken Technos Co., Ltd., corona treated on one side, 160 μm thick. (β) Release film (β-1) MRF38: Biaxially oriented polyethylene terephthalate resin film with easy peel treatment on one side, manufactured by Mitsubishi Chemical Corporation, with a thickness of 38 μm.

[0070] (γ) Acrylic resin binder (γ-1)NTZ-3104: A composite one-pack adhesive manufactured by Arakawa Chemical Industries, Ltd., containing a (meth)acrylic acid ester with alkyl ester groups having 1 to 12 carbon atoms, to which a photopolymerization initiator has been added. Solvent-free, mass-average molecular weight 67,000. (δ) Isocyanate (δ-1) Coronate HX: Hexamethylene diisocyanate manufactured by Tosoh Corporation, solvent-free, 100% solids.

[0071] Example 1 Preparation of adhesive main component composition Acrylic resin binder (γ-1) NTZ-3104 was used alone as the main adhesive component. Preparation of isocyanate compositions An isocyanate composition was obtained by adding 1 part by mass of isocyanate (δ-1) Coronate HX to 100 parts by mass of acrylic resin binder (γ-1) NTZ-3104, thoroughly mixing and degassing the mixture.

[0072] Process (A) and Process (B) A release film (β-1) MRF38 was coated with an adhesive main component composition, followed by an isocyanate composition, using a two-layer die coater at a line speed of 10 m / min. The thickness of each coated layer was adjusted so that the adhesive main component layer was 40 μm and the isocyanate composition layer was 4 μm. Process (C) The surface of the isocyanate composition layer of the solvent-free laminate obtained in step (B) was exposed to an active energy ray (ultraviolet light) at a rate of 1000 mJ / cm². 2 The material was irradiated and cured. During the irradiation with the active energy rays, a nitrogen gas purge was performed. Process (D) The corona-treated surface of the base film (α-1) TM3436A was applied to the isocyanate composition layer side of the adhesive layer, which is the cured product of the solvent-free laminate obtained in process (C), and the two layers were bonded at a line speed of 2 m / min to obtain a laminated film in which the adhesive layer, which is the cured product of the solvent-free laminate, and the base film were laminated in that order on a release film. The (a) adhesion and (b) tackiness of the laminated film obtained above were measured and evaluated, and the results are shown in Table 1.

[0073] Examples 2-6 Each laminated film was obtained in the same manner as in Example 1, except that the thicknesses of the adhesive main composition layer and the isocyanate composition layer were adjusted to the thicknesses shown in Table 1. The (a) adhesion and (b) tackiness of each laminated film obtained here were measured and evaluated, and the results are shown in Table 1.

[0074] Comparative Example 1 Process (A) An adhesive main component composition was applied to the easily peelable surface of the release film (β-1) MRF38 using a die coater at a line speed of 10 m / min. The thickness of the applied adhesive main component layer was adjusted to 40 μm. Process (C) The surface of the adhesive main component layer obtained in step (A) is exposed to an active energy ray (ultraviolet light) at a rate of 1000 mJ / cm².2 The material was irradiated and cured. During the irradiation with the active energy rays, a nitrogen gas purge was performed. Process (D) The corona-treated surface of the base film (α-1) TM3436A was applied to the surface of the cured layer of the adhesive main component composition obtained in step (C), and the two layers were bonded at a line speed of 2 m / min to obtain a laminated film without an isocyanate layer, in which the cured layer of the adhesive main component composition and the base film were laminated in that order on a release film. The (a) adhesion and (b) tackiness of the laminated film obtained above were measured and evaluated, and the results are shown in Table 1.

[0075] [Table 1]

[0076] It was found that a laminated film obtained by the manufacturing method according to the present invention, which comprises a solvent-free adhesive layer containing an isocyanate composition layer and a base film, exhibits superior adhesion between the adhesive layer and the base film compared to a laminated film that does not contain such an isocyanate composition layer. [Explanation of Symbols]

[0077] 1. Adhesive main composition 1x Adhesive main composition layer in solvent-free laminate 1y Adhesive main composition layer in the adhesive layer 2. Isocyanate composition Isocyanate composition layer in 2x solvent-free laminate 2y Isocyanate composition layer in adhesive layer 3 2-layer die 4. Release film 5 Solvent-free laminate 5y adhesive layer 6. Base film 10-layer film

Claims

1. A method for producing a laminated film comprising a solvent-free adhesive layer cured by active energy rays on a base film, (A) A step of forming an adhesive main composition layer by applying an active energy ray curable adhesive main composition containing an acrylic resin binder and free of solvents onto a release film. (B) Simultaneously with or immediately after step (A), an isocyanate composition containing an isocyanate but free of solvents is applied to the surface of the adhesive main component composition layer obtained in step (A) opposite to the release film, thereby forming a solvent-free laminate comprising an adhesive main component composition layer and an isocyanate composition layer. (C) A step of forming an adhesive layer, which is a cured product of the solvent-free laminate, by irradiating the surface of the isocyanate composition layer side of the solvent-free laminate obtained in step (B) with active energy rays and curing it, and (D) A process to obtain a laminated film in which the adhesive layer, which is the cured product of the solvent-free laminate obtained in step (C), and the base film are laminated in this order on a release film by applying a base film to the surface of the adhesive layer, which is the cured product of the solvent-free laminate, and the base film. A method that includes this.

2. The method according to claim 1, wherein the base film is a polyvinyl chloride resin film.

3. The method according to claim 1 or claim 2, wherein the thickness of the isocyanate composition layer of the solvent-free laminate formed in step (B) is 20% or less of the thickness of the adhesive main component composition layer.

4. The thickness of the adhesive main composition layer formed in step (A) is 20 μm or more and 100 μm or less. The thickness of the isocyanate composition layer formed in step (B) is 0.5 μm or more and 15 μm or less. The method according to claim 3.

5. The method according to claim 1 or 2, wherein a solvent-free laminate is formed by using a two-layer die and performing steps (A) and (B) simultaneously to laminate together an adhesive main component layer and an isocyanate composition layer on a release film.

6. The method according to claim 1 or claim 2, wherein the active energy ray-curable adhesive composition comprises a (meth)acrylic acid ester having an alkyl ester group having 1 to 12 carbon atoms as an acrylic resin binder, and further comprises a polymerization initiator.

7. The method according to claim 1 or claim 2, wherein the isocyanate composition comprises a (meth)acryloyl group-containing isocyanate compound as the isocyanate and a (meth)acrylic acid ester having an alkyl ester group having 1 to 12 carbon atoms as the acrylic resin binder.

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