Multilayer film and method for manufacturing same

Abstract

The present invention pertains to a multilayer film having a base film, a highly adhesive layer provided in direct contact with one surface of the base film, a bonding layer provided in direct contact with the surface of the highly adhesive layer, and a top layer provided in direct contact with the surface of the bonding layer, the total thickness (T1 + T2) of the thickness (T1) of the easily adhesive layer and the thickness (T2) of the bonding layer is 150 nm or more, and the easily adhesive layer contains organic particles (NP) having an average particle diameter (T3) equal to or greater than the thickness (T1) of the easily adhesive layer.

Description

Technical Field

[0001] The present invention relates to a multilayer film and a method for manufacturing the same. Background Art

[0002] Multilayer films having a base film and a resin layer containing particles are known (see Patent Documents 1 to 3).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-023170;

[0006] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2018-118438;

[0007] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2020-023171. Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] Regarding a multilayer body of a base film and other functional layers such as a retardation layer having an optical function in addition to the base film, the adhesion between the base film and the functional layer such as the optical function layer may be insufficient. In such a case, an easy-adhesion layer for improving the adhesion to the functional layer is sometimes provided on the base film. Further, in order to improve the slidability of the base film, the easy-adhesion layer sometimes contains particles.

[0010] However, when there is an easy-adhesion layer containing particles, the adhesion between the base film and the functional layer may be insufficient.

[0011] Therefore, there is a need for a multilayer film having good adhesion between the base film and other functional layers, and a method for manufacturing such a multilayer film with good adhesion.

[0012] Solutions to the Problems

[0013] The inventors of the present invention conducted in-depth research to solve the above problems. As a result, it was found that the above problems can be solved by a multilayer film, and thus the present invention was completed. The multilayer film has a base film, a specific easy-adhesion layer, a bonding layer, and a top layer, and the total thickness (T1 + T2) of the thickness T1 of the easy-adhesion layer and the thickness T2 of the bonding layer is a specified value or more.

[0014] That is, the present invention provides the following.

[0015] [1] A multilayer film having a base film, an easy-adhesion layer provided in direct contact with one surface of the base film, a bonding layer provided in direct contact with the surface of the easy-adhesion layer, and a top layer provided in direct contact with the surface of the bonding layer,

[0016] The total thickness (T1 + T2) of the above-mentioned easy-adhesion layer and the thickness T2 of the above-mentioned bonding layer is 150 nm or more.

[0017] The above-mentioned easy-adhesion layer contains organic particles (NP) with an average particle diameter T3 that is equal to or greater than the thickness T1 of the easy-adhesion layer.

[0018] [2] According to the multilayer film described in [1], wherein the ratio (T1 / T3) of the thickness T1 of the above-mentioned easy-adhesion layer to the average particle diameter T3 of the above-mentioned organic particles (NP) is 0.6 or less.

[0019] [3] According to the multilayer film described in [1] or [2], wherein the above-mentioned base film contains a cyclic olefin-based polymer.

[0020] [4] According to the multilayer film described in any one of [1] to [3], wherein the above-mentioned organic particles (NP) are particles of a (meth)acrylic acid polymer.

[0021] [5] According to the multilayer film described in any one of [1] to [4], wherein the above-mentioned easy-adhesion layer is a cured product of an easy-adhesion layer material containing the above-mentioned organic particles (NP), a polymer (P1) having a (meth)acrylate unit, and a crosslinking agent (1).

[0022] [6] According to the multilayer film described in any one of [1] to [5], wherein the above-mentioned bonding layer is a cured product of a bonding layer material containing a polymer (P2) having a (meth)acrylate unit and a crosslinking agent (2).

[0023] [7] According to the multilayer film described in any one of [1] to [6], wherein the above-mentioned easy-adhesion layer is a cured product of an easy-adhesion layer material containing the above-mentioned organic particles (NP), a polymer (P1) having a (meth)acrylate unit, and a crosslinking agent (1).

[0024] The above-mentioned bonding layer is a cured product of a bonding layer material containing a polymer (P2) having a (meth)acrylate unit and a crosslinking agent (2).

[0025] The above-mentioned polymer (P1) and the above-mentioned polymer (P2) have a common (meth)acrylate unit.

[0026] [8] According to the multilayer film described in any one of [1] to [7], wherein the above-mentioned top layer is a cured product of a top layer material containing a polymer (P3) having a styrene-based monomer unit.

[0027] [9] According to the multilayer film described in any one of [1] to [8], wherein the above-mentioned multilayer film is a stretched film.

[0028]

[10] A method for manufacturing a multilayer film, wherein the multilayer film is the multilayer film described in any one of [1] to [9], and the manufacturing method includes the following steps:

[0029] Step (1), preparing a long strip of base film;

[0030] Step (2-1), coating a liquid easy-bonding layer material on the base film to form a coating film of the easy-bonding layer material;

[0031] Step (2-2), drying the coating film of the easy-bonding layer material to form an easy-bonding layer, and obtaining a multilayer body (I) having the base film and the easy-bonding layer;

[0032] Step (3), stretching the multilayer body (I) to obtain a multilayer body (II);

[0033] Step (4), winding the multilayer body (II);

[0034] Step (5-1), unwinding the wound multilayer body (II), and coating a liquid bonding layer material on the easy-bonding layer of the multilayer body (II) to form a coating film of the bonding layer material;

[0035] Step (5-2), drying the coating film of the bonding layer material to form a bonding layer, and obtaining a multilayer body (III) having the base film, the easy-bonding layer, and the bonding layer in sequence;

[0036] Step (6-1), coating a liquid top layer material on the bonding layer of the multilayer body (III) to form a coating film of the top layer material;

[0037] Step (6-2), drying the coating film of the top layer material to form a top layer, and obtaining a multilayer body (IV) having the base film, the easy-bonding layer, the bonding layer, and the top layer in sequence;

[0038] Step (7), stretching the multilayer body (IV) to obtain a multilayer film.

[0039] Advantages of the Invention

[0040] According to the present invention, it is possible to provide: a multilayer film with good adhesion between the base film and other functional layers; a method for manufacturing such a multilayer film with good adhesion. Detailed Description of the Invention

[0041] Hereinafter, embodiments and examples will be shown to explain the present invention in detail. However, the present invention is not limited to the embodiments and examples shown below, and can be arbitrarily changed within the scope of the claims of the present invention and its equivalent scope. The constituent elements of the embodiments shown below can be appropriately combined.

[0042] In the following description, a "long" film means a film having a length more than 5 times its width, preferably 10 times or more its width, specifically a film having a length such that it can be stored or transported in a rolled-up state. There is no particular limitation on the upper limit of the length of the film, and it can be, for example, 100,000 times or less its width.

[0043] In the following description, unless otherwise specified, the slow axis of a film or layer means the slow axis in the plane of the film or layer.

[0044] In the following description, unless otherwise specified, the orientation angle of a film or layer means the angle formed by the slow axis of the film or layer with respect to the length direction of the film or layer.

[0045] In the following description, unless otherwise specified, the angle formed by the optical axes (slow axis, transmission axis, absorption axis, etc.) of the respective layers in a member having multiple layers means the angle when viewed from the thickness direction of the above-mentioned layer.

[0046] In the following description, unless otherwise specified, the tilt direction of a long film means a direction in the plane of the film that is neither parallel nor perpendicular to the length direction of the film.

[0047] In the following description, unless otherwise specified, the in-plane retardation Re of a layer is the value represented by Re = (nx - ny) × d. Here, nx represents the refractive index in the direction that gives the maximum refractive index in the direction perpendicular to the thickness direction of the layer (in-plane direction). ny represents the refractive index in the direction orthogonal to the nx direction in the in-plane direction of the layer. d represents the thickness of the layer. Unless otherwise specified, the measurement wavelength is 550 nm.

[0048] In the following description, unless otherwise specified, the directions "parallel", "perpendicular", and "orthogonal" of an element may also include, within the range not impairing the effects of the present invention, errors, for example, within the range of ±3°, ±2°, or ±1°.

[0049] Unless otherwise specified, a "resin having positive intrinsic birefringence" means a resin in which the refractive index in the stretching direction is greater than the refractive index in the direction orthogonal to the stretching direction. In addition, unless otherwise specified, a "polymer having positive intrinsic birefringence" means a polymer in which the refractive index in the stretching direction is greater than the refractive index in the direction orthogonal to the stretching direction.

[0050] Unless otherwise specified, a "resin having negative intrinsic birefringence" means a resin in which the refractive index in the stretching direction is less than the refractive index in the direction orthogonal to the stretching direction. Unless otherwise specified, a "polymer having negative intrinsic birefringence" means a polymer in which the refractive index in the stretching direction is less than the refractive index in the direction orthogonal to the stretching direction.

[0051] In the following description, the term "(meth)acryloyl" includes "acryloyl", "methacryloyl", and combinations thereof.

[0052] The term "(meth)acrylic acid" includes "acrylic acid", "methacrylic acid", and combinations thereof.

[0053] The term "(meth)acrylonitrile" includes "acrylonitrile", "methacrylonitrile", and combinations thereof.

[0054] The term "(meth)acrylate" includes "acrylate", "methacrylate", and combinations thereof.

[0055] In the following description, the name of a certain monomer is sometimes used to represent a polymer unit having a structure formed by the polymerization of that monomer. For example, a unit having a structure formed by the polymerization of (meth)acrylate is sometimes referred to as a "(meth)acrylate unit". In addition, a unit having a structure formed by the polymerization of a styrene-based monomer is sometimes referred to as a "styrene-based monomer unit". Furthermore, a polymer containing a styrene-based monomer unit is sometimes simply referred to as a styrene-based polymer. However, in the present application, the structure of a molecule and its constituent elements is not limited by its manufacturing method.

[0056] In the following description, "a certain layer A is provided in direct contact with one surface of a certain layer B" means that there is no other arbitrary layer between one surface of layer B and layer A.

[0057] [1. Outline of the multilayer film]

[0058] A multilayer film according to an embodiment of the present invention has a base film, an easy-bonding layer provided in direct contact with one surface of the base film, a bonding layer provided in direct contact with the surface of the easy-bonding layer, and a top layer provided in direct contact with the surface of the bonding layer. In addition, the total thickness (T1 + T2) of the thickness T1 of the easy-bonding layer and the thickness T2 of the bonding layer is 150 nm or more, and the easy-bonding layer contains organic particles (NP) having an average particle diameter T3 of at least the thickness T1 of the easy-bonding layer.

[0059] Hereinafter, a multilayer film having one easy-bonding layer, one bonding layer, and one top layer respectively will be mainly described as an example. However, the present invention is not limited thereto. For example, the multilayer film may have an easy-bonding layer, a bonding layer, and a top layer provided on two main surfaces of one base film, respectively.

[0060] By the multilayer film having the above structure, a film with good adhesion can be produced. Here, the adhesion refers to an index of the peel resistance between the base film and the top layer.

[0061] Furthermore, due to the above-described structure of the easy-bonding layer, the multi-layer body of the intermediate-produced base film and the easy-bonding layer has good slidability. Therefore, even when the multi-layer body is wound during the manufacturing process, the multi-layer body is not easily scratched and can be smoothly unwound. Therefore, a multi-layer film with good adhesion can be easily manufactured.

[0062] The total thickness (T1 + T2) is preferably 80 nm or more, more preferably 100 nm or more, further preferably 110 nm or more, further preferably 150 nm or more, further preferably 160 nm or more, further preferably 165 nm or more, and from the viewpoint of reducing the influence on the optical properties of the multi-layer film, it is preferably 800 nm or less, more preferably 700 nm or less, further preferably 500 nm or less.

[0063] The thickness of the layer of the multi-layer film can be measured by a reflection spectroscopic film thickness measuring device (for example, the reflection spectroscopic film thickness measuring system "F20" manufactured by Filmetrics).

[0064] The ratio (T1 / T3) of the thickness T1 of the above-described easy-bonding layer to the average particle diameter T3 of the organic particles (NP) is usually 1 / 1 or less (i.e., 1 or less), preferably 0.8 or less, more preferably 0.6 or less, further preferably 0.46 or less, and is usually greater than 0, and can be, for example, 0.1 or more. When T1 / T3 is within the above range, both the adhesion of the multi-layer film and the surface state of the multi-layer film can be made good.

[0065] The average particle diameter T3 of the organic particles (NP) is, for example, 100 nm or more, for example, 150 nm or more, for example, 1000 nm or less, for example, 800 nm or less.

[0066] In the present specification, the average particle diameter T3 of the organic particles (NP) is the weight-average particle diameter measured by the dynamic light scattering method.

[0067] [1.1. Base film]

[0068] As the base film, a film containing a thermoplastic resin can be used. Hereinafter, the thermoplastic resin that can be contained in the base film is referred to as thermoplastic resin(s). The base film can be a film composed only of a thermoplastic resin.

[0069] As the thermoplastic resin(s), a thermoplastic resin containing a polymer and optionally any components is preferably used. As the thermoplastic resin(s), a resin having negative intrinsic birefringence can be used, and from the viewpoint of easily manufacturing a multi-layer film as a broadband wavelength film, a resin having positive intrinsic birefringence is preferably used.

[0070] The resin having positive intrinsic birefringence contains a polymer having positive intrinsic birefringence. When examples of polymers having positive intrinsic birefringence are cited, polyolefins such as polyethylene and polypropylene can be cited; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyarylene sulfides such as polyphenylene sulfide; polyvinyl alcohol; polycarbonate; polyarylate; cellulose ester polymer; polyethersulfone; polysulfone; polyarylsulfone; polyvinyl chloride; alicyclic structure-containing polymers such as norbornene-based polymers; rod-like liquid crystal polymers, etc. These polymers can be used alone or two or more of them can be used in any ratio in combination. In addition, the polymer can be a homopolymer or a copolymer.

[0071] As the polymer(s) contained in the thermoplastic resin(s), an alicyclic structure-containing polymer is preferred because of its excellent mechanical properties, heat resistance, transparency, low hygroscopicity, dimensional stability, and lightness. As an example of the polymer containing an alicyclic structure, a cyclic olefin-based polymer, that is, a polymer containing a structural unit having a structure obtained by polymerizing a cyclic olefin and its hydride can be cited.

[0072] As examples of the alicyclic structure-containing polymer of the cyclic olefin-based polymer, (1) norbornene-based polymers, (2) monocyclic cyclic olefin polymers, (3) cyclic conjugated diene polymers, (4) vinyl alicyclic hydrocarbon polymers, and their hydrides, etc. can be cited. Among these, norbornene-based polymers are preferred. As the norbornene-based polymer, for example, a ring-opening polymer of a norbornene monomer, a ring-opening copolymer of a norbornene monomer and other monomers capable of ring-opening copolymerization, and their hydrides; an addition polymer of a norbornene monomer, an addition copolymer of a norbornene monomer and other monomers capable of copolymerization, etc. can be cited. Among these, from the viewpoint of transparency, a hydride of a ring-opening polymer of a norbornene monomer is particularly preferred. The alicyclic structure-containing polymer can be selected from the polymers disclosed in, for example, Japanese Patent Laid-Open No. 2002-321302.

[0073] The proportion of the polymer in the thermoplastic resin(s) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, and particularly preferably 90% by weight to 100% by weight. When the proportion of the polymer is within the above range, a multilayer film excellent in heat resistance and transparency can be manufactured.

[0074] The thermoplastic resin(s) can also contain any component other than the above polymer in combination with the polymer. As the arbitrary component, for example, colorants such as pigments and dyes; plasticizers; fluorescent brighteners; dispersants; heat stabilizers; light stabilizers; ultraviolet absorbers; antistatic agents; antioxidants; fine particles; surfactants, etc. can be cited. These components can be used alone or two or more of them can be used in any ratio in combination.

[0075] The glass transition temperature TgA of the thermoplastic resin(s) is preferably 100 °C or higher, more preferably 110 °C or higher, particularly preferably 120 °C or higher, preferably 190 °C or lower, more preferably 180 °C or lower, and particularly preferably 170 °C or lower. When the glass transition temperature TgA of the thermoplastic resin(s) is at or above the lower limit value of the above range, the durability of the substrate film in a high-temperature environment can be improved. In addition, when the glass transition temperature TgA of the thermoplastic resin(s) is at or below the upper limit value of the above range, the stretching treatment can be easily performed. The glass transition temperature can be measured using a differential scanning calorimeter (manufactured by SIINano technology, product name: DSC6220) based on JIS-K7121 under the condition of a heating rate of 10 °C / minute.

[0076] The thermoplastic resin(s) preferably does not contain particles. In this application, "does not contain" particles can also include the case of substantially not containing particles. The case of substantially not containing particles means that when the thermoplastic resin(s) contains particles, the increase in haze of the substrate film is within the range of 0.05% or less compared to the state of completely not containing particles.

[0077] The substrate film may have optical isotropy, and thus may not have a slow axis. In addition, the substrate film may have optical anisotropy, and thus may have a slow axis. When the substrate film included in the multilayer film before stretching has a slow axis, the direction of the slow axis can be arbitrarily set within the range that can obtain the desired optical properties of the stretched multilayer film.

[0078] The in-plane retardation Re of the substrate film is not particularly limited, preferably 190 nm or higher, more preferably 200 nm or higher, particularly preferably 205 nm or higher, preferably 300 nm or lower, more preferably 280 nm or lower, and particularly preferably 260 nm or lower. The in-plane retardation Re of the substrate film represents the in-plane retardation at a measurement wavelength of 550 nm.

[0079] The thickness of the substrate film is not particularly limited, preferably 30 μm or higher, more preferably 35 μm or higher, particularly preferably 40 μm or higher, preferably 60 μm or lower, more preferably 55 μm or lower, and particularly preferably 50 μm or lower.

[0080] The surface of the base film can be modified. Through the modification treatment, the adhesion between the base film and the easy-to-bond layer can be improved. Examples of the modification treatment include energy ray irradiation treatment and chemical treatment. Examples of the energy ray irradiation treatment include corona treatment, plasma treatment, electron beam irradiation treatment, ultraviolet irradiation treatment, etc. From the perspective of treatment efficiency, corona treatment and plasma treatment are preferred, and corona treatment is particularly preferred. In addition, as the chemical treatment, for example, saponification treatment, a method of dipping in an aqueous solution of an oxidant such as potassium dichromate solution or concentrated sulfuric acid and then washing with water can be cited.

[0081] The output power of the corona treatment is preferably the treatment condition with as little damage as possible to the surface to be treated. Specifically, it is preferably 0.02 kW or more, more preferably 0.04 kW or more, preferably 5 kW or less, and more preferably 2 kW or less.

[0082] [1.2. Easy-to-bond layer]

[0083] The easy-to-bond layer contains organic particles (NP), and preferably contains a polymer in addition to the organic particles (NP).

[0084] The easy-to-bond layer is more preferably a cured product of the easy-to-bond layer material. The easy-to-bond layer is provided to improve the slidability of the film during intermediate manufacturing in the production of the multilayer film. The easy-to-bond layer material preferably contains a polymer (P1) and a crosslinking agent (1) in addition to the organic particles (NP).

[0085] (Easy-to-bond layer material: Organic particles (NP))

[0086] (Examples of organic particles)

[0087] From the perspective of easily adjusting the refractive index of the particles and narrowing the width of the particle size distribution, the organic particles are preferably particles of an organic polymer.

[0088] Examples of the organic particles include silicone polymer particles, fluororesin particles, and particles of (meth)acrylic polymers.

[0089] As the particles of the organic polymer, from the perspective of improving the affinity with the polymer (P1), particles of (meth)acrylic polymers are preferred.

[0090] (Meth)acrylic polymers refer to polymers containing (meth)acrylic monomer units as repeating units. The (meth)acrylic monomer units are structural units having a structure obtained by polymerizing (meth)acrylic monomers. (Meth)acrylic monomers are (meth)acrylic acid and derivatives of (meth)acrylic acid. Examples of derivatives of (meth)acrylic acid include (meth)acrylic esters, (meth)acrylamides, and (meth)acrylonitriles, with (meth)acrylic esters being preferred. Examples of (meth)acrylic esters include alkyl (meth)acrylates, and the alkyl group in the alkyl (meth)acrylate may have substituents such as a hydroxyl group and a halogen atom, or may have no substituents.

[0091] (Meth)acrylic polymers may also contain arbitrary monomer units in addition to (meth)acrylic monomer units.

[0092] (Meth)acrylic polymers are preferably crosslinked polymers containing crosslinkable monomer units. The crosslinkable monomer units are units that can be obtained by polymerizing crosslinkable monomers. Examples of crosslinkable monomers include polyfunctional monomers containing two or more polymerizable groups per molecule. Specifically, examples include divinylbenzene, ethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, pentaerythritol triacrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetraacrylate, diallyl phthalate, and triallyl cyanurate. The crosslinkable monomers can be used alone or in combination of two or more in any ratio.

[0093] As the particles of the (meth)acrylic polymer, particles containing (meth)acrylate units are preferred, and particles of a polymethyl methacrylate-based crosslinked polymer containing methyl methacrylate units and crosslinkable monomer units are more preferred.

[0094] As the organic particles, commercially available products can be used. Examples of commercially available products include "EPOSTAR (registered trademark) MX series" (particles of polymethyl methacrylate-based crosslinked polymer) manufactured by Nippon Shokubai Co., Ltd., "CHEMISNOW MP series" (acrylic polymer particles) manufactured by Soken Chemical & Engineering Co., Ltd., "CHEMISNOW MX series" (styrene-acrylic resin particles) manufactured by Soken Chemical & Engineering Co., Ltd., and "TECHPOLYMER" manufactured by Sekisui Chemical Co., Ltd.

[0095] (Average particle size of organic particles)

[0096] The average particle diameter of the particles is usually not less than the thickness T1 of the easily adhesive layer, preferably less than 450 nm, more preferably not more than 400 nm, and still more preferably not more than 350 nm. When the average particle diameter of the organic particles is within the above range, the organic particles are not likely to fall off from the easily adhesive layer. In addition, the slidability of the multi-layer body of the intermediate-produced base film and the easily adhesive layer is improved.

[0097] (Content ratio of organic particles)

[0098] The content ratio of the organic particles in the easily adhesive layer is preferably not less than 1% by weight, more preferably not less than 1.2% by weight, still more preferably not less than 1.5% by weight, preferably not more than 5% by weight, more preferably not more than 4.5% by weight, and still more preferably not more than 4% by weight. The content ratio of the organic particles in the easily adhesive layer is the weight ratio of the organic particles contained in the easily adhesive layer per unit weight. The content ratio of the organic particles in the easily adhesive layer is usually the same as the weight ratio of the organic particles contained in the easily adhesive material when the total amount of the solid components in the easily adhesive layer material used for forming the easily adhesive layer is 100% by weight.

[0099] (Easily adhesive layer material: Polymer (P1))

[0100] As the easily adhesive layer material, various resins containing polymers can be used. Examples of the resin include polyurethane resin, olefin resin, polyester resin, epoxy resin, and (meth)acrylic resin. By using these resins to form the easily adhesive layer, a multi-layer film with excellent adhesiveness between the easily adhesive layer and other layers can be achieved.

[0101] As the polyurethane resin, a resin containing polyurethane or its cross-linked product as the polymer (P1) can be used. Examples of the polyurethane include polyurethanes derived from various polyols and polyisocyanates. Examples of the polyol include any one of aliphatic polyester polyols, polyether polyols, polycarbonate polyols, and polyethylene terephthalate polyols obtained by reacting a polyol compound with a polycarboxylic acid; and mixtures thereof. Examples of the polyol compound include, for example, ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, glycerol, trimethylolpropane, etc. Examples of the polycarboxylic acid include polycarboxylic acids such as polycarboxylic acids containing dicarboxylic acids and tricarboxylic acids or their acid anhydrides. Examples of the dicarboxylic acid include, for example, adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid. Examples of the tricarboxylic acid include, for example, trimellitic acid. Examples of the polyether polyol include, for example, poly(propylene oxide ether) polyol, poly(ethylene-propylene oxide ether) polyol, etc.

[0102] In the above polyurethane, after the reaction of, for example, a polyol and a polyisocyanate, the hydroxyl groups remaining in an unreacted form can be utilized as polar groups capable of undergoing a crosslinking reaction with the functional groups in the crosslinking agent. As the polyurethane, a polycarbonate-based polyurethane derived from a polycarbonate-based polyol and a polyisocyanate and containing a carbonate structure in its skeleton is preferred. Regarding the polyurethane resin, reference can be made to, for example, the description in Japanese Patent Application Laid-Open No. 2016-182568.

[0103] As the polyurethane, the polyurethane contained in an aqueous emulsion commercially available as an aqueous polyurethane resin can be used. The aqueous polyurethane resin is a composition containing a polyurethane and water, and is usually a composition in which the polyurethane and any components contained as needed are dispersed in water. As examples of the aqueous urethane resin, "ADEKABONTIGHTER" series manufactured by ADEKA Corporation, "OLESTER" series manufactured by Mitsui Chemicals, Inc., "BONDIC" series manufactured by DIC Corporation, "HYDRAN (WLS201, WLS202, etc.)" series, "Impranil" series manufactured by Bayer AG, "POIZ" series manufactured by Kao Corporation, "SANPRENE" series manufactured by Sanyo Chemical Industries, Ltd., "SUPERFLEX" series manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "NeoRez" series manufactured by Kusumoto Chemicals, Ltd., "Sancure" series manufactured by Lubrizol Corporation, etc. can be used.

[0104] As the olefin resin, an acid-modified polyolefin or its crosslinked product containing 0.1% by weight to 10% by weight of an unsaturated carboxylic acid component can be used as the resin of the polymer (P1). Preferred examples of the olefin component as the main component of the acid-modified polyolefin include olefins having 2 to 6 carbon atoms such as ethylene, propylene, isobutene, 2-butene, 1-butene, 1-pentene, 1-hexene, and mixtures thereof. Among them, from the viewpoint of improving the adhesion of the resin layer, olefins having 2 to 4 carbon atoms such as ethylene, propylene, isobutene, and 1-butene are more preferred, ethylene and propylene are further preferred, and ethylene is particularly preferred. On the other hand, as the unsaturated carboxylic acid component as the modifying component of the acid-modified polyolefin, for example, acrylic acid, methacrylic acid, maleic acid (anhydride), itaconic acid (anhydride), fumaric acid, crotonic acid, half esters and half amides of unsaturated dicarboxylic acids, etc. can be mentioned. Among them, since the adhesion of the layer formed by the resin (hereinafter, also referred to as the resin layer) can be improved and cracks can be suppressed, acrylic acid, methacrylic acid, and maleic acid (anhydride) are preferred, and acrylic acid and maleic acid (anhydride) are particularly preferred. The above-mentioned unsaturated carboxylic acid component is usually copolymerized in the acid-modified polyolefin, and its form is not particularly limited. As the copolymerized state, for example, random copolymerization, block copolymerization, graft copolymerization (graft modification), etc. can be mentioned. Regarding the olefin resin, reference can be made to, for example, the description in Japanese Patent Application Laid-Open No. 2014-240174.

[0105] As the acid-modified polyolefin, commercially available products can be used. Examples of such commercially available products of the aqueous dispersion include the "ARROW BASE (ARROW BASE SA-1200, ARROW BASE SB-1200, ARROW BASE SE-1200, ARROW BASE SB-1010)" series (manufactured by Unitika Ltd.).

[0106] As the polyester resin, a resin can be used which contains a polyester or its cross-linked product obtained by the reaction of the above polyol compound and the above polyacid as the polymer (P1). In this polyester, for example, after the reaction of the polyol compound and the polyacid is completed, the unreacted remaining hydroxyl groups and carboxyl groups can be used as polar groups capable of undergoing a cross-linking reaction with a cross-linking agent. In addition, the polyester may be a copolymer obtained by copolymerizing a copolymerization component having polar groups such as hydroxyl groups and carboxyl groups with the above polyol compound and polyacid. Further, in order to improve the adhesion of the resin layer, the polyester resin preferably contains an acrylic polymer in combination with a polyester or its cross-linked product. Regarding the polyester resin, reference can be made to, for example, the description in Japanese Patent Laid-Open No. 2015-024511.

[0107] As the polyester, commercially available products can be used. Examples of commercially available water-soluble or water-dispersible polyesters include the "Nichigo Polyester (Nichigo Polyester W-0030, Nichigo Polyester W-0005S30WO, Nichigo Polyester WR-961, etc.)" series (manufactured by Nippon Gohsei Co., Ltd.), the "Pesresin A (Pesresin A-210, Pesresin A-520, Pesresin A-684G, Pesresin A-695GE, etc.)" series (manufactured by Takamatsu Oil & Fat Co., Ltd.), and the like.

[0108] As the epoxy resin, any epoxy resin such as a one-component curable epoxy resin or a two-component curable epoxy resin can be used. It is particularly preferable to include a water-soluble epoxy polymer as the polymer (P1). Preferred examples of the water-soluble epoxy polymer include polyamide epoxy polymers. The polyamide epoxy polymer can be obtained, for example, by reacting epichlorohydrin with a polyamide polyamine, and the polyamide polyamine is obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adipic acid. Commercially available products of such polyamide epoxy polymers include, for example, "Sumirez Resin 650(30)" and "Sumirez Resin 675" manufactured by Sumitomo Chemical Co., Ltd. Regarding epoxy resins, the description in, for example, Japanese Patent Laid-Open No. 2008-26352 can be referred to.

[0109] In the case of using a water-soluble epoxy polymer, in order to further improve the coatability, it is preferable to use a water-soluble polymer such as polyvinyl alcohol in combination. The polyvinyl alcohol includes not only partially saponified polyvinyl alcohol and completely saponified polyvinyl alcohol, but also modified polyvinyl alcohols such as carboxyl-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, hydroxymethyl-modified polyvinyl alcohol, and amino-modified polyvinyl alcohol. A commercially available product of polyvinyl alcohol is, for example, anionic group-containing polyvinyl alcohol "KL-318" manufactured by Kuraray Co., Ltd.

[0110] As the (meth)acrylic resin, a resin containing a (meth)acrylic polymer or its crosslinked product as the polymer (P1) can be used. In addition, as the (meth)acrylic polymer, for example, a homopolymer of a (meth)acrylic monomer, a copolymer of two or more (meth)acrylic monomers, a copolymer of one or more (meth)acrylic monomers and other monomers, etc. can be cited. In addition, as the (meth)acrylic monomer, for example, acrylic acid esters such as acrylic acid and acrylic alkyl esters, methacrylic acid esters such as acrylamide, acrylonitrile, methacrylic acid, and methacrylic alkyl esters, methacrylamide, and methacrylonitrile can be cited.

[0111] Among them, as the polymer (P1), a polymer having a (meth)acrylate unit is preferable, and a homopolymer and a copolymer of acrylic monomers selected from acrylic esters and methacrylic esters are more preferable. As a particularly preferable example, a homopolymer and a copolymer of acrylic monomers selected from acrylic esters and methacrylic esters having an alkyl group with 1 to 6 carbon atoms can be cited. In addition, the acrylic polymer is preferably an acrylic polymer obtained by copolymerizing a copolymerizable component having a polar group such as a hydroxyl group or a carboxyl group with the above acrylic monomer in such a manner that it can react (crosslink) with the functional group of the crosslinking agent. Regarding acrylic resins, the description in, for example, Japanese Patent Laid-Open No. 2015-024511 can be referred to.

[0112] When the polymer (P1) has (meth)acrylate units, taking the total of the monomer units contained in the polymer (P1) as 100% by weight, the weight ratio of the (meth)acrylate units in the polymer (P1) is preferably 1% by weight or more, more preferably 5% by weight or more, still more preferably 10% by weight or more, and usually 100% by weight or less.

[0113] When the easy - adhesive layer material is a (meth)acrylic resin, as the polymer (P1) contained in the easy - adhesive layer material, a copolymer of an alkyl acrylate of methacrylic acid and an alkyl acrylate of acrylic acid is preferred. In this case, the number of carbon atoms of the alkyl group constituting the alkyl ester is preferably 1 - 6, particularly preferably 1 - 4. As a more specific example, the polymer (P1) is particularly preferably a copolymer of methyl methacrylate and butyl acrylate. By using such a preferred polymer (P1), the adhesion between the easy - adhesive layer and the bonding layer is excellent, and thus it is particularly preferred.

[0114] The polymer (P1) constituting the easy - adhesive layer material may be one kind or two or more kinds. Thus, the easy - adhesive layer material may also be a composite resin that combinatorially contains two or more of the above - mentioned polyurethane, polyolefin, polyester, epoxy polymer, and (meth)acrylic polymer. It may be, for example, a resin that combinatorially contains polyurethane and acid - modified polyolefin, or a resin that combinatorially contains polyester and acrylic polymer.

[0115] The proportion of the polymer (P1) in the solid content (total amount of components other than the solvent) of the easy - adhesive layer material is preferably 50% by weight - 99% by weight, more preferably 70% by weight - 99% by weight, and particularly preferably 90% by weight - 97% by weight. When the proportion of the polymer (P1) is within the above range, the resulting easy - adhesive layer can exhibit desired adhesion.

[0116] (Easy - adhesive layer material: Cross - linker (1))

[0117] By making the easy - adhesive layer material contain the cross - linker (1), the easy - adhesive layer, which is a cured product of the easy - adhesive layer material, can become a layer containing a polymer having a cross - linked structure. As the cross - linker (1), a compound having two or more functional groups in the molecule that can react with functional groups such as polar groups contained in the polymer to form bonds, a polymer cross - linker that becomes a polymer having functional groups capable of forming bonds by polymerizing a monomer composition containing the compound, or a mixture thereof can be used. As examples of the cross - linker compound (including the monomers constituting the polymer cross - linker), epoxy compounds, carbodiimide compounds, oxazoline compounds, isocyanate compounds, etc. can be cited. In addition, the cross - linker compound can be used alone or two or more kinds can be used in any ratio in combination.

[0118] As the epoxy compound, a polyfunctional epoxy compound having two or more epoxy groups in the molecule can be used. Thereby, the crosslinking reaction can proceed to effectively improve the mechanical strength of the resin layer.

[0119] As the epoxy compound, from the viewpoint of ease of use, an epoxy compound that is soluble in water or can be dispersed and emulsified in water is preferred. Examples of the above epoxy compounds include: a diepoxy compound obtained by etherification of 1 mole of glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol with 2 moles of epichlorohydrin; a polyepoxy compound obtained by etherification of 1 mole of polyols such as glycerol, polyglycerol, trimethylolpropane, pentaerythritol, and sorbitol with 2 moles or more of epichlorohydrin; a diepoxy compound obtained by esterification of 1 mole of dicarboxylic acids such as phthalic acid, terephthalic acid, oxalic acid, and adipic acid with 2 moles of epichlorohydrin, and the like.

[0120] More specifically, as the epoxy compound, epoxy compounds such as 1,4-bis(2’,3’-epoxypropoxy)butane, 1,3,5-triglycidyl isocyanurate, 1,3-diglycidyl-5-(γ-acetoxy-β-oxypropyl) isocyanurate, sorbitol polyglycidyl ethers, polyglycerol polyglycidyl ethers, pentaerythritol polyglycidyl ethers, diglycerol polyglycidyl ether, glycerol polyglycidyl ethers, and trimethylolpropane polyglycidyl ethers are preferred. Examples of specific commercially available products thereof include the "Denacol (Denacol EX-521, EX-614B, etc.)" series manufactured by Nagase ChemteX Corporation.

[0121] As the oxazoline compound, an addition-polymerizable oxazoline compound can be used. Specific examples thereof include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like. In addition, one of them can be used alone, or two or more of them can be used in any ratio in combination. Among these, 2-isopropenyl-2-oxazoline is also easily available industrially, and thus is preferred.

[0122] When the crosslinking agent (1) is a polymer crosslinking agent, a polymer of an addition-polymerizable oxazoline compound and an arbitrary unsaturated monomer, namely the crosslinking agent (1-o), is particularly preferred. As an arbitrary unsaturated monomer other than the oxazoline compound constituting the crosslinking agent (1-o), any monomer that can copolymerize with the addition-polymerizable oxazoline and does not react with the oxazoline group can be used. Such an arbitrary unsaturated monomer can be arbitrarily selected from the above-mentioned monomers for use. As a preferred specific example of such an unsaturated monomer, methacrylates such as methyl methacrylate can be cited. Moreover, as the crosslinking agent (1-o), a copolymer of 2-isopropenyl-2-oxazoline and a methacrylate is particularly preferred from the viewpoint of exhibiting desired effects such as good adhesion.

[0123] The amount of the addition-polymerizable oxazoline used in the production of the crosslinking agent (1-o) is preferably 5 parts by weight or more relative to 100 parts by weight of all the monomer components used for producing the oxazoline compound.

[0124] As the crosslinking agent (1-o), a crosslinking agent that can be obtained as a commercial product can be used. Among the crosslinking agents (1-o), as examples of the water-soluble type crosslinking agent, EPOCROS WS-500 and WS-700 manufactured by Nippon Shokubai Co., Ltd. can be cited. In addition, for example, as examples of the emulsion type crosslinking agent, EPOCROS K-2010, K-2020, and K-2030 manufactured by Nippon Shokubai Co., Ltd. can be cited.

[0125] The crosslinking agent (1), such as the crosslinking agent (1-o) and other crosslinking agents, can be used alone or in combination of two or more in any ratio.

[0126] In the easy-bonding layer, the ratio of the crosslinking agent (1) to the polymer (P1) can be appropriately adjusted within the range where desired adhesion and other effects are exhibited. Specifically, the ratio of the crosslinking agent (1) to the total 100 parts by weight of the polymer (P1) and the crosslinking agent (1) is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and on the other hand, preferably 30 parts by weight or less, more preferably 20 parts by weight or less.

[0127] (Easy-bonding layer material: solvent)

[0128] The easy - adhesion layer material can contain a solvent. By containing a solvent, the easy - adhesion layer material can be made into a liquid composition, which can facilitate the formation operations of the easy - adhesion layer such as coating. As the solvent, water, an organic solvent, or a mixture thereof can be appropriately selected. Examples of the organic solvent include methyl acetate, ethyl acetate, acetone, methyl ethyl ketone, 3 - methyl - 2 - butanone, methyl isopropyl ketone, methyl isobutyl ketone, tetrahydrofuran, cyclopentyl methyl ether, acetylacetone, cyclohexanone, 2 - methylcyclohexanone, 1,3 - dioxolane, 1,4 - dioxane, 2 - pentanone, N,N - dimethylformamide, etc. In addition, the solvent can be used alone or two or more solvents can be used in any ratio. From the aspects of good high - volatility and high ability to dissolve other components, water can be preferably used as the solvent.

[0129] The proportion of the solvent contained in the easy - adhesion layer material can be appropriately adjusted in such a way as to obtain physical properties suitable for the formation operations of the easy - adhesion layer such as coating. Specifically, the proportion can be adjusted so that the solid - component concentration (the proportion of the components other than the solvent, including organic particles (NP)) is preferably 1 wt% - 20 wt%, more preferably 2 wt% - 10 wt%.

[0130] (Easy - adhesion layer material: other components)

[0131] The easy - adhesion layer material can further contain arbitrary components. Examples of the arbitrary components include a curing accelerator, a curing aid, particles other than organic particles (NP), a heat stabilizer, a weather stabilizer, a leveling agent, a surfactant, an antioxidant, an antistatic agent, a slip agent, an anti - blocking agent, an antifogging agent, a lubricant, a dye, a pigment, a natural oil, a synthetic oil, a wax, etc.

[0132] [1.3. Bonding layer]

[0133] The bonding layer is preferably a cured product of the bonding - layer material. The bonding layer is provided to improve the adhesion between the substrate film and the top layer. The bonding - layer material contains a polymer (P2) and a cross - linker (2).

[0134] (Bonding - layer material: polymer (P2))

[0135] As the bonding - layer material, various resins containing polymers can be used. Examples of the resin are the same as those of the resins that the easy - adhesion layer material can contain.

[0136] The polymer (P2) contained as the bonding layer material is preferably a polymer having (meth)acrylate units. Among them, as the polymer (P2), a polymer having (meth)acrylate units is preferred, and more preferably a homopolymer or copolymer of acrylic monomers selected from acrylate and methacrylate. Among them, as a particularly preferred example, a homopolymer or copolymer of acrylic monomers selected from acrylate and methacrylate having an alkyl group with 1 to 6 carbon atoms can be cited. In addition, the acrylic polymer is preferably an acrylic polymer obtained by copolymerizing a copolymerization component having a polar group such as a hydroxyl group or a carboxyl group with the above acrylic monomer in such a manner as to be able to react (crosslinking reaction) with the functional group of the crosslinking agent.

[0137] When the polymer (P2) has (meth)acrylate units, the weight ratio of the (meth)acrylate units in the polymer (P2) can be in the same range as the weight ratio of the (meth)acrylate units in the polymer (P1) when the polymer (P1) has (meth)acrylate units.

[0138] When the bonding layer material is a (meth)acrylic resin, as the polymer (P2) contained in the bonding layer material, a copolymer of an alkyl ester of methacrylic acid and an alkyl ester of acrylic acid is preferred. In this case, the number of carbon atoms of the alkyl group constituting the alkyl ester is preferably 1 to 6, and particularly preferably 1 to 4. As a more specific example, the polymer (P2) is particularly preferably a copolymer of methyl methacrylate and butyl acrylate. By using such a preferred polymer (P2), the adhesion between the bonding layer, the easy-bonding layer, and the top layer is excellent, and thus it is particularly preferred.

[0139] The proportion of the polymer (P2) in the solid content (total amount of components other than the solvent) of the bonding layer material is preferably 50% by weight to 99% by weight, more preferably 70% by weight to 99% by weight, and particularly preferably 90% by weight to 99% by weight. When the proportion of the polymer (P2) is within the above range, the obtained bonding layer can exhibit the desired adhesion.

[0140] (Bonding layer material: Crosslinking agent (2))

[0141] By including the crosslinking agent (2) in the bonding layer material, the bonding layer as a cured product of the bonding layer material can be a layer containing a polymer having a crosslinked structure. Examples of the crosslinking agent (2) are the same as those of the crosslinking agent (1) that the easy-bonding layer can contain.

[0142] In the bonding layer, the ratio of the crosslinking agent (2) to the polymer (P2) can be appropriately adjusted within a range that exhibits the desired adhesion and other effects. Specifically, it can be within the same range as the ratio of the crosslinking agent (1) to the polymer (P1) in the easy-bonding layer.

[0143] (Bonding layer material: solvent)

[0144] The bonding layer material can contain a solvent. By containing a solvent, the bonding layer material can be made into a liquid composition, and operations for forming the bonding layer such as coating can be easily performed. As the solvent, the same examples as those of the solvents that the easy-bonding layer can contain can be cited. In addition, one type of solvent can be used alone, or two or more types can be used in any ratio in combination. From the aspects of good high volatility and high ability to dissolve other components, water can be preferably used as the solvent.

[0145] The ratio of the solvent contained in the bonding layer material can be appropriately adjusted in a manner that provides physical properties suitable for operations for forming the bonding layer such as coating. Specifically, the ratio can be adjusted such that the solid content concentration (the ratio of components other than the solvent) is preferably 1% by weight to 20% by weight, and more preferably 2% by weight to 15% by weight.

[0146] The bonding layer material can further contain arbitrary components. As examples of the arbitrary components, the same examples as those of the arbitrary components that the easy-bonding layer can contain can be cited. One type of arbitrary component can be used alone, or two or more types can be used in any ratio in combination.

[0147] (Relationship between the bonding layer material and the easy-bonding layer material)

[0148] The polymer (P2) that the bonding layer material can contain and the polymer (P1) that the easy-bonding layer material can contain preferably have common monomer units.

[0149] More preferably, the bonding layer material contains a polymer containing (meth)acrylate units as the polymer (P2), and the easy-bonding layer material contains a polymer containing (meth)acrylate units as the polymer (P1), and the polymer (P1) and the polymer (P2) have common (meth)acrylate units.

[0150] That the polymer (P1) and the polymer (P2) “have common (meth)acrylate units” means that both the polymer (P1) and the polymer (P2) have common acrylate units and / or have common methacrylate units. In particular, from the viewpoint of obtaining good adhesion, as the “common (meth)acrylate units”, methacrylate units are preferably present, and methyl methacrylate units are more preferably present.

[0151] More specifically, both the polymer (P1) and the polymer (P2) are preferably polymers having methyl methacrylate units and butyl acrylate units, and more preferably copolymers of methyl methacrylate and butyl acrylate.

[0152] The crosslinking agent (2) that the bonding layer material can contain and the crosslinking agent (1) that the easy-bonding layer material can contain are preferably the same crosslinking agent. More specifically, it is more preferable that both the crosslinking agent (1) and the crosslinking agent (2) are copolymers of methyl methacrylate and 2-isopropenyl oxazoline.

[0153] [1.4. Top layer]

[0154] The top layer is preferably a cured product of the top layer material. The top layer is preferably a coating layer formed by coating the top layer material. The top layer material is preferably a material containing the polymer (P3).

[0155] (Top layer material: polymer (P3))

[0156] As the polymer (P3) that the top layer can contain, a polymer having positive intrinsic birefringence can be used, but from the viewpoint of easily manufacturing a multilayer film as a broadband wavelength film, a polymer having negative intrinsic birefringence is preferred.

[0157] When examples of polymers having negative intrinsic birefringence are given, homopolymers of styrene or styrene derivatives, and styrene-based polymers (such as polystyrene, poly(2-vinylnaphthalene)) containing copolymers of styrene or styrene derivatives and arbitrary monomers can be cited; polyacrylonitrile polymers; polymethyl methacrylate polymers; these multi-copolymerized polymers; and cellulose compounds such as cellulose ester polymers, etc. These polymers can be used alone or in combination of two or more in any ratio. Among them, polymers having styrene-based monomer units or cellulose ester polymers are preferred, and polymers having styrene-based monomer units are more preferred. Here, the term "styrene-based monomer" refers to styrene monomers, styrene derivative monomers, and combinations thereof.

[0158] Examples of arbitrary monomers copolymerized with styrene or styrene derivatives include acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene. In addition, these polymers can be used alone or in combination of two or more in any ratio.

[0159] As examples of styrene derivatives, derivatives having substituents at one or more substitution positions selected from the benzene ring, α-position, or β-position of styrene and their hydrides can be cited. As examples of the substituents, halogen atoms, alkyl groups, alkenyl groups, aromatic groups, alkoxy groups, and alkoxycarbonyl groups can be cited. When the substituent is a carbon-containing group, the number of carbon atoms of each substituent can be 1 to 6. In addition, derivatives having a structure in which substituents at multiple substitution positions of the benzene ring are combined to form a ring (for example, vinylnaphthalene) are also included in the styrene derivatives.

[0160] As specific examples of styrene monomers, styrene, halogenated styrene, halogenated alkylstyrene, alkylstyrene, alkenylstyrene, alkoxystyrene, alkoxycarbonylstyrene, and their hydrides can be cited.

[0161] As examples of halogenated styrene, chlorostyrene, bromostyrene, and fluorostyrene can be cited. As examples of halogenated alkylstyrene, chloromethylstyrene can be cited.

[0162] As examples of alkylstyrene, methylstyrene, ethylstyrene, isopropylstyrene, tert-butylstyrene, and 2,4-dimethylstyrene can be cited. As examples of alkenylstyrene, vinylstyrene can be cited.

[0163] As examples of alkoxystyrene, methoxystyrene and ethoxystyrene can be cited. As examples of alkoxycarbonylstyrene, vinyl benzoate can be cited.

[0164] As examples of other styrene monomers, phenylstyrene and vinylnaphthalene can be cited.

[0165] As examples of cellulose ester polymers having negative intrinsic birefringence, cellulose ester polymers in which suitable aryl groups are introduced into cellulose by acylation can be cited.

[0166] As a particularly preferred example of the polymer (P3) constituting the top layer material, a copolymer of styrene or a styrene derivative and maleic anhydride can be cited. From the viewpoint of high heat resistance, a copolymer of styrene or a styrene derivative and maleic anhydride is particularly preferred. In this copolymer, the amount of maleic anhydride units is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, particularly preferably 15 parts by weight or more, preferably 30 parts by weight or less, more preferably 28 parts by weight or less, and particularly preferably 26 parts by weight or less, relative to 100 parts by weight of the styrene polymer. The maleic anhydride unit means a structural unit having a structure formed by polymerizing maleic anhydride.

[0167] The proportion of the polymer (P3) in the solid components (total amount of components other than the solvent) of the top layer material is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, and particularly preferably 90% by weight to 100% by weight. When the proportion of the polymer (P3) is within the above range, the top layer can exhibit appropriate optical properties.

[0168] (Top layer material: Solvent)

[0169] The top layer material can contain a solvent. By containing a solvent, the top layer material can be made into a liquid composition, and the formation operations of the top layer such as coating can be easily performed. Examples of the solvent are the same as those of the solvents that the easy adhesion layer can contain. The solvent can be used alone or in combination of two or more in any ratio. From the aspects of good high volatility and high ability to dissolve other components, it is possible to preferably use a ketone such as methyl ethyl ketone, methyl isobutyl ketone, or a mixture thereof as the solvent.

[0170] The proportion of the solvent contained in the top layer material can be appropriately adjusted in such a way as to obtain physical properties suitable for the formation operations of the top layer such as coating. Specifically, the proportion can be adjusted in such a way that the solid component concentration (proportion of components other than the solvent) is preferably 5% by weight to 25% by weight, more preferably 10% by weight to 20% by weight.

[0171] (Top layer material: Additive (t))

[0172] The top layer material can further optionally contain an additive (t). In the top layer material, the additive (t) is other components with a lower content ratio by weight compared to the polymer (P3) which is usually the main component. The additive (t) is preferably a substance that can be compatible with the polymer (P3). Specifically, when the additive (t) is contained, it is preferable to appropriately select its type to meet the requirements of the haze of the obtained multilayer film.

[0173] The additive (t) can exhibit functions such as adjusting the degree of manifestation of the optical anisotropy of the top layer within a desired range. That is, when the thickness of the top layer suitable for obtaining the desired optical properties of the finally stretched multilayer film is too thin, the molding accuracy decreases, and the surface unevenness of the top layer may become large. In such a case, by combining an additive (t) having a positive intrinsic birefringence with a polymer (P3) having a negative intrinsic birefringence and adding them to the top layer material, the surface unevenness of the top layer can be improved.

[0174] Examples of the additive (t) include polymers such as (meth)acrylic polymers, styrene polymers, (meth)acrylic acid-styrene copolymers, polyesters, polycarbonates, and olefin polymers. These polymers can be used alone, or two or more of them can be used in any ratio, or they can be copolymers of each resin. In particular, (meth)acrylic polymers, styrene polymers, and (meth)acrylic acid-styrene copolymers are preferred because they are highly likely to be compatible with the polymer (P3) having a negative intrinsic birefringence value.

[0175] From the viewpoint of well satisfying the compatibility with the preferred polymer (P3), the characteristics as the above additive, and other requirements of the present invention, particularly preferred examples of the additive (t) include copolymers containing (meth)acrylate units and styrene-based monomer units (for example, the trade name "TX-100S", manufactured by Denka Co., Ltd., a copolymer of methyl methacrylate and styrene).

[0176] When the top layer material contains the additive (t), the ratio of the additive (t) to the polymer (P3) can be appropriately adjusted to a range that exhibits desired optical effects and other effects, such as adjusting the degree of manifestation of the optical anisotropy of the top layer to a desired range. Specifically, when the top layer material contains the additive (t), the ratio of the additive (t) to 100 parts by weight of the polymer (P3) is preferably greater than 0 part by weight, preferably 5 parts by weight or more, preferably 75 parts by weight or less, more preferably 70 parts by weight or less, further preferably 50 parts by weight or less, and can be further preferably 25 parts by weight or less.

[0177] (Top layer material: other components)

[0178] The top layer material can further contain arbitrary components. Examples of the arbitrary components include the same examples as the arbitrary components that the thermoplastic resin (s) can contain. The arbitrary components can be used alone, or two or more of them can be used in any ratio.

[0179] [2. Easy-bonding layer, bonding layer, top layer, and manufacturing method of multilayer film]

[0180] The easy - adhesion layer is usually a cured product of the above - mentioned easy - adhesion layer material, the bonding layer is usually a cured product of the above - mentioned bonding layer material, and the top layer is usually a cured product of the above - mentioned top layer material. The methods for forming the easy - adhesion layer, the bonding layer, and the top layer from the easy - adhesion layer material, the bonding layer material, and the top layer material respectively are not particularly limited, and any known method can be appropriately selected and used. Specifically, by coating the easy - adhesion layer material on the surface of the substrate film to form a coating film of the easy - adhesion layer material and drying the coating film, the easy - adhesion layer can be formed. In addition, by coating the bonding layer material on the surface of the easy - adhesion layer to form a coating film of the bonding layer material and drying the coating film, the bonding layer can be formed. Further, by coating the top layer material on the surface of the bonding layer to form a coating film of the top layer material and drying the coating film, the top layer can be formed.

[0181] The easy - adhesion layer material, the bonding layer material, and the top layer material can each contain a solvent. When forming the easy - adhesion layer, the bonding layer, and the top layer, these solvents volatilize, and part or all of them can disappear from the layer. In addition, the easy - adhesion layer material and the bonding layer material can include reactive materials such as cross - linkers. When forming the easy - adhesion layer and the bonding layer, these reactive materials can react and become elements that form part of the polymer molecular structure such as cross - linking.

[0182] The multilayer film of the present embodiment can be manufactured by any method. For example, the multilayer film can be manufactured by a manufacturing method that sequentially includes the following steps (1), (2 - 1), (2 - 2), (3), (4), (5 - 1), (5 - 2), (6 - 1), (6 - 2), (7). The method for manufacturing the multilayer film can include any additional steps in addition to the following steps.

[0183] Step (1): A step of preparing a long strip of substrate film.

[0184] Step (2 - 1): A step of coating a liquid easy - adhesion layer material on the above - mentioned substrate film to form a coating film of the above - mentioned easy - adhesion layer material.

[0185] Step (2 - 2): A step of drying the coating film of the above - mentioned easy - adhesion layer material to form an easy - adhesion layer and obtaining a multilayer body (I) having the above - mentioned substrate film and the above - mentioned easy - adhesion layer.

[0186] Step (3): A step of stretching the above - mentioned multilayer body (I) to obtain a multilayer body (II).

[0187] Step (4): A step of winding the above - mentioned multilayer body (II).

[0188] Step (5 - 1): A step of unwinding the wound above - mentioned multilayer body (II) and coating a liquid bonding layer material on the above - mentioned easy - adhesion layer of the above - mentioned multilayer body (II) to form a coating film of the above - mentioned bonding layer material.

[0189] Step (5-2): A step of drying the coating film of the above-described bonding layer material to form a bonding layer, and obtaining a multilayer body (III) having successively the above-described base material film, the above-described easily adhesive layer, and the above-described bonding layer.

[0190] Step (6-1): A step of applying a liquid top layer material onto the bonding layer of the above-described multilayer body (III) to form a coating film of the above-described top layer material.

[0191] Step (6-2): A step of drying the coating film of the above-described top layer material to form a top layer, and obtaining a multilayer body (IV) having successively the above-described base material film, the above-described easily adhesive layer, the above-described bonding layer, and the above-described top layer.

[0192] Step (7): A step of stretching the above-described multilayer body (IV) to obtain a multilayer film.

[0193] [2.1. Step (1)]

[0194] In step (1), a base material film is prepared. Generally, the base material film is formed by molding a thermoplastic resin(s). Generally, the base material film is formed into a film. From the viewpoint of effectively manufacturing a long multilayer film, it is preferable that the base material film is formed into a long film. In the case where the base material film is a long film, the base material film can be transported along its length direction on a transport line, and the subsequent steps can be continuously performed downstream of the transport line.

[0195] The method for forming the base material film is not particularly limited. Examples of the method for forming the base material film include, for example, a melt molding method or a solution casting method. More specific examples of the melt molding method include an extrusion molding method, a compression molding method, a blow molding method, an injection molding method, a blow molding method, and a stretching molding method. Among these methods, from the viewpoint of obtaining a base material film having excellent mechanical strength and surface accuracy, an extrusion molding method, a blow molding method, or a compression molding method is preferable, and among them, from the viewpoint of being able to efficiently and simply manufacture the base material film, an extrusion molding method is particularly preferable.

[0196] [2.2. Step (2-1)]

[0197] In step (2-1), a liquid easily adhesive layer material is applied onto the above-described base material film to form a coating film of the above-described easily adhesive layer material.

[0198] Examples of the coating method of the liquid easily adhesive layer material include: a curtain coating method, an extrusion coating method, a roll coating method, a spin coating method, a dip coating method, a bar coating method, a spray coating method, a slide coating method, a printing coating method, an intaglio coating method, a die coating method, and a slot coating method, etc.

[0199] The coating film thickness of the easily adhesive layer material can be adjusted so that the easily adhesive layer has a desired thickness T1 in the manufactured multilayer film.

[0200] [2.3. Process (2-2)]

[0201] In process (2-2), the coating film of the above-mentioned easily adherable layer material is dried to form an easily adherable layer, and a multilayer body (I) having the above-mentioned base material film and the above-mentioned easily adherable layer is obtained. In process (2-2), the drying of the coating film of the easily adherable layer material can be carried out by drying methods such as natural drying, heat drying, reduced pressure drying, reduced pressure heat drying, etc.

[0202] In addition, in process (2-2), a treatment for promoting crosslinking can be arbitrarily performed on the coating film of the easily adherable layer material. By this treatment, the crosslinking reaction of the crosslinking agent (1) can be carried out, and the mechanical strength and solvent resistance of the easily adherable layer can be improved. Examples of the crosslinking treatment include heat treatment, irradiation treatment with active energy rays such as ultraviolet rays, etc.

[0203] [2.4. Process (3)]

[0204] In process (3), the above-mentioned multilayer body (I) is stretched to obtain a multilayer body (II).

[0205] The stretching direction in process (3) can be set according to the optical properties that the multilayer film is desired to exhibit. For example, in the case of manufacturing a long strip broadband wavelength film as a multilayer film by combining a base material film of a thermoplastic resin (s) having positive intrinsic birefringence and a top layer containing a polymer (P3) having negative intrinsic birefringence, the stretching direction in process (3) is preferably an inclined direction that is neither parallel nor perpendicular to the width direction of the base material film. In this case, the angle formed by the stretching direction with respect to the width direction of the base material film is preferably 35° or more, more preferably 37° or more, further preferably 40° or more, particularly preferably 42° or more, preferably 55° or less, more preferably 53° or less, further preferably 50° or less, and particularly preferably 48° or less.

[0206] The stretching ratio in process (3) is preferably 1.1 times or more, more preferably 1.2 times or more, preferably 2.5 times or less, more preferably 2.0 times or less. When the stretching ratio is above the lower limit value of the above range, the refractive index in the stretching direction can be increased. In addition, when the stretching ratio is below the upper limit value of the above range, the direction of the slow axis of the stretched base material film can be easily controlled.

[0207] The stretching temperature in step (3) is preferably not lower than TgA, more preferably not lower than (TgA + 2)°C, particularly preferably not lower than (TgA + 5)°C, preferably not higher than (TgA + 40)°C, more preferably not higher than (TgA + 35)°C, particularly preferably not higher than (TgA + 30)°C. Herein, "TgA" represents the glass transition temperature of the thermoplastic resin(s). When the stretching temperature is within the above range, the molecules contained in the base film can be effectively oriented, and thus the production of a multilayer film having desired optical properties can proceed smoothly.

[0208] The direction of the slow axis of the multilayer body (II) is preferably an inclined direction that is neither parallel nor perpendicular to the width direction of the multilayer body (II). From the viewpoint of obtaining a broadband wavelength film as the multilayer film, the orientation angle of the multilayer body (II) is preferably not less than 25°, more preferably not less than 30°, further preferably not less than 35°, preferably less than 55°, more preferably less than 50°, and further preferably less than 48°.

[0209] Optical properties such as the retardation of the multilayer body (II) can be set according to the optical properties that the multilayer film is desired to exhibit. For example, when producing a broadband wavelength film as the multilayer film, the in-plane retardation Re of the multilayer body (II) is preferably not less than 180 nm, more preferably not less than 190 nm, particularly preferably not less than 200 nm, preferably not higher than 250 nm, more preferably not higher than 240 nm, and particularly preferably not higher than 230 nm.

[0210] The thickness of the multilayer body (II) can be arbitrarily set within the range where a desired multilayer film can be obtained. Specifically, the thickness is preferably not less than 30 μm, more preferably not less than 35 μm, particularly preferably not less than 40 μm, preferably not higher than 80 μm, more preferably not higher than 70 μm, and particularly preferably not higher than 60 μm.

[0211] [2.5. Step (4)]

[0212] In step (4), the multilayer body (II) is wound. In the production method of the present embodiment, a multilayer body (II) having a base film and an easy-adhesion layer that is provided in direct contact with one surface of the base film and is a cured product of an easy-adhesion layer material containing organic particles (NP) can be obtained. Since the easy-adhesion layer containing organic particles (NP) is exposed on the surface of the multilayer body (II), the slidability of the multilayer body (II) is improved. Therefore, even when the multilayer body (II) is wound, damage caused by friction due to the close contact of the wound and overlapping multilayer bodies (II) with each other is not likely to occur. Further, in step (5-1) described later, the multilayer body (II) can be smoothly unwound.

[0213] The coefficient of kinetic friction between the base film and the easy-to-bond layer of the multilayer body (II) can more effectively reduce defects, so it is preferably 0.8 or less, more preferably 0.75 or less, and the smaller the better. Usually, it is 0 or more, and it can also be greater than 0. The coefficient of kinetic friction between the base film and the easy-to-bond layer can be measured by the following method.

[0214] (Method for measuring the coefficient of kinetic friction)

[0215] Cut the multilayer body (II) into two pieces with a size of 80 mm × 200 mm to obtain two test pieces. Overlap the two test pieces with the base film and the easy-to-bond layer facing each other, and measure the coefficient of kinetic friction between the base film and the easy-to-bond layer in accordance with JIS K7125 (1999). The measurement can be carried out using a friction tester (for example, manufactured by Toyo Seiki Seisakusho, "TR-2") with a load of 200 g, a moving distance of 100 mm, and a moving speed of 500 mm / minute.

[0216] [2.6. Process (5-1)]

[0217] In process (5-1), unwind the wound multilayer body (II), and apply a liquid bonding layer material on the easy-to-bond layer of the multilayer body (II) to form a coating film of the bonding layer material. As an example of the coating method of the liquid bonding layer material, the same examples as those cited as examples of the coating method of the liquid easy-to-bond layer material in process (2-1) can be cited.

[0218] The coating film thickness of the bonding layer material can be adjusted so that the bonding layer becomes the desired thickness T2 in the manufactured multilayer film.

[0219] [2.7. Process (5-2)]

[0220] In process (5-2), dry the coating film of the bonding layer material to form a bonding layer, and obtain a multilayer body (III) having the above-mentioned base film, the above-mentioned easy-to-bond layer, and the above-mentioned bonding layer in sequence.

[0221] As an example of the drying method of the coating film of the bonding layer material, the same examples as those cited as examples of the drying method of the coating film of the easy-to-bond layer material in process (2-2) can be cited.

[0222] [2.8. Process (6-1)]

[0223] In process (6-1), apply a liquid top layer material on the above-mentioned bonding layer of the multilayer body (III) to form a coating film of the top layer material. As an example of the coating method of the liquid top layer material, the same examples as those cited as examples of the coating method of the liquid easy-to-bond layer material in process (2-1) can be cited.

[0224] The coating thickness of the top layer material can be adjusted in such a way that the top layer has a desired thickness in the manufactured multilayer film.

[0225] [2.9. Process (6-2)]

[0226] In process (6-2), the coating of the top layer material is dried to form the top layer, and a multilayer body (IV) having the above-mentioned base film, the above-mentioned easy-bonding layer, the above-mentioned bonding layer, and the above-mentioned top layer in this order is obtained.

[0227] As an example of the drying method of the coating of the top layer material, the same examples as those cited as examples of the drying method of the coating of the easy-bonding layer material in process (2-2) can be cited, and heat drying using an oven is preferably used.

[0228] [2.10. Process (7)]

[0229] In process (7), the multilayer body (IV) is stretched to obtain a multilayer film.

[0230] The stretching of the multilayer body (IV) in process (7) is usually carried out in an oven.

[0231] The stretching direction in process (7) can be set according to the optical properties that the multilayer film is desired to exhibit. For example, in the case of manufacturing a long strip broadband wavelength film as a multilayer film by combining a base film as a layer of a thermoplastic resin (s) having positive intrinsic birefringence and a top layer containing a polymer (P3) having negative intrinsic birefringence, the stretching direction in process (7) is preferably a direction substantially parallel to the length direction of the multilayer body (IV). In this case, the angle formed by the stretching direction with respect to the width direction of the multilayer body (IV) is preferably 85° or more, more preferably 87° or more, further preferably 89° or more, preferably 95° or less, more preferably 93° or less, further preferably 91° or less, and particularly preferably 90°.

[0232] In the case of stretching in a direction substantially parallel to the length direction of the multilayer body (IV), the stretching in process (7) can be carried out in a free uniaxial stretching manner. Free uniaxial stretching is stretching in a certain direction without applying a binding force in the direction other than the stretching direction. Therefore, for example, the free uniaxial stretching in the direction substantially parallel to the length direction of the multilayer body (IV) can be the stretching in the length direction without restricting the ends in the width direction of the multilayer body (IV).

[0233] The draw ratio in step (7) is preferably 1.1 times or more, more preferably 1.15 times or more, particularly preferably 1.2 times or more, preferably 2.0 times or less, more preferably 1.8 times or less, and particularly preferably 1.6 times or less. When the draw ratio in step (7) is within the above range, a multilayer film having desired optical properties can be easily obtained.

[0234] [3. Properties of Multilayer Film, etc.]

[0235] The film of the present embodiment can be made into a film with good adhesion. Here, the adhesion refers to an index of the peel resistance between the base film and the top layer. The adhesion can be evaluated by the cross-cut test specified in JIS K5600-5-6 (1999).

[0236] Specifically, incisions are made at 1 mm intervals in the top layer, the adhesive layer, and the easy-to-bond layer of the multilayer film as a specimen in the range of 5 mm × 5 mm to produce 25 squares with a side length of 1 mm. A transparent tape is pasted on the surface on the top layer side of the specimen, and the transparent tape is peeled off. The number of squares that are not peeled off and adhere to the base film of the multilayer film and remain is measured, whereby the adhesion can be evaluated. The higher the number of remaining squares, the higher the adhesion. In the present embodiment, an adhesion of 20 / 25 or more can be exhibited in this test.

[0237] By making the adhesion of the multilayer film good, the durability of the display device assembled with the multilayer film can be improved. In addition, reprocessing in the manufacturing process of the display device can be facilitated. For example, when the multilayer film is attached to a panel having a display element (such as a liquid crystal cell of a liquid crystal display device) and it is found that there is a defect in the attachment, and the multilayer film is peeled off for reusing the panel, the occurrence of a defect such that only a part of the layer of the multilayer film remains on the panel can be reduced.

[0238] The multilayer film preferably has high transparency. Therefore, the multilayer film preferably has a high total light transmittance. The specific total light transmittance of the multilayer film is preferably 80% or more, more preferably 85% or more, and particularly preferably 88% or more. The light transmittance can be measured in the wavelength range of 400 nm to 700 nm using a spectrophotometer in accordance with JIS K0115.

[0239] There is no particular limitation on the overall thickness of the multilayer film, which is preferably 30 μm or more, more preferably 35 μm or more, particularly preferably 40 μm or more, preferably 100 μm or less, more preferably 90 μm or less, and particularly preferably 80 μm or less.

[0240] The multilayer film preferably has a strip shape. The width of the strip-shaped multilayer film is not particularly limited, preferably 1300 mm or more, more preferably 1400 mm or more, particularly preferably 1500 mm or more, preferably 2000 mm or less, and more preferably 1800 mm or less.

[0241] The use of the multilayer film is not limited. From the viewpoint of making use of excellent optical properties, it is preferably used as an optical film. When specific examples of preferred uses are given, the multilayer film as a broadband wavelength film can also be bonded to a linear polarizer and used for manufacturing a circular polarizer. Since the in-plane retardation deviation of the above multilayer film is small, the circular polarizer having the multilayer film can suppress the deviation of the polarization state of the circularly polarized light transmitted through the circular polarizer. Thus, the circular polarizer can be used as a reflection suppression film that suppresses light reflection with high uniformity.

[0242] Examples

[0243] The following examples specifically illustrate the present invention. However, the present invention is not limited to the following examples and can be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and its equivalent scope.

[0244] In the following description, unless otherwise specified, "%" and "parts" representing amounts are based on weight. In addition, unless otherwise specified, the following operations are performed under conditions of normal temperature (20°C ± 15°C) and normal pressure (1 atm).

[0245] [Evaluation Method]

[0246] (Thickness of the layer)

[0247] The thickness of the film or each layer constituting it was measured using the reflection spectroscopic film thickness measurement system "F20" of Filmetrics.

[0248] (Average particle size)

[0249] The weight average particle size of the particles was measured by the dynamic light scattering method using "Nanotrac UPA-EX150" manufactured by Microtrac, USA.

[0250] (In-plane retardation Re)

[0251] The in-plane retardation Re of the film of the specimen was measured using a phase difference meter ("AxoScan" manufactured by Axometrics Co., Ltd.).

[0252] (Evaluation method for adhesion)

[0253] As an evaluation method for adhesion, a cross-cut test specified in JIS K5600-5-6 (1999) was performed.

[0254] In the top layer, bonding layer, and easily bondable layer of the multilayer film used as a specimen, incisions are made at 1-mm intervals within a range of 5 mm × 5 mm to produce 25 squares with sides of 1 mm. A transparent tape is adhered to the surface on the top-layer side of the specimen, and then the transparent tape is peeled off. The number of squares that remain attached to the base film of the multilayer film without being peeled off is measured, and evaluation is performed according to the following evaluation criteria.

[0255] Good: The number of remaining squares is 20 / 25 or more and 25 / 25 or less.

[0256] Bad: The number of remaining squares is 19 / 25 or less.

[0257] (Number of foreign substances observed in appearance)

[0258] The multilayer film is placed on a blackboard, and planar observation is performed visually under a fluorescent lamp. The multilayer film is observed within a range of 1 m × 1 m, and foreign substances with a size having a maximum diameter of 100 μm or more are counted as defects.

[0259] [Example 1]

[0260] (1-1. Base film)

[0261] The granular norbornene-based resin (manufactured by Zeon Corporation; glass transition temperature 126°C) is dried at 100°C for 5 hours. The dried resin is supplied to an extruder and extruded in a sheet form from a T-die onto a casting drum via a polymer tube and a polymer filter to perform extrusion molding. The molded resin is cooled to obtain a long-strip base film (i) with a thickness of 70 μm.

[0262] (1-2. Easily bondable layer material 1)

[0263] The following materials are mixed to obtain a liquid easily bondable layer material 1 with a solid content of 8.7% as an uncured acrylic resin.

[0264] Material containing polymer (P1): 14 parts of an aqueous dispersion (solid content concentration 50%) of a methyl methacrylate / butyl acrylate copolymer (polymerization ratio: 60 wt% methyl methacrylate and 40 wt% butyl acrylate) as an acrylic resin

[0265] Material containing crosslinking agent (1): 6 parts of an oxazoline group-containing (meth)acrylic crosslinking agent (trade name “EPOCROS WS-700”, manufactured by Nippon Shokubai Co., Ltd., copolymer of methyl methacrylate and 2-isopropenyl oxazoline, solid content concentration 25 wt%, amount of oxazoline group 4.5 mmol / (g solid content))

[0266] Two parts of an aqueous dispersion of (meth)acrylic polymer particles as organic particles (NP) (manufactured by Nippon Shokubai Co., Ltd., "EPOSTAR MX200W"; polymethyl methacrylate-based crosslinked polymer, weight average particle diameter 300 nm, solid content concentration 10% by weight)

[0267] 0.5% by weight of an acetylene-based surfactant as a wetting agent (manufactured by Air Products and Chemicals, Inc., "Surfynol 440") relative to the total solid content

[0268] Water: 78 parts

[0269] (1 - 3. Multilayer body (I))

[0270] The surface of the substrate film (i) obtained in (1 - 1) is subjected to corona treatment. The corona treatment is carried out using a corona treatment device (manufactured by Kasuga Electric Co., Ltd.) under the conditions of a line speed of 10 m / minute, a nitrogen environment, and a power of 1.5 kW.

[0271] The easy - adhesive layer material 1 obtained in (1 - 2) is coated on the corona - treated surface of the substrate film (i) to form a coating film of the easy - adhesive layer material. The coating is carried out using a roll coater under the condition that the thickness after drying of the coating film becomes 0.1 μm.

[0272] After that, the coating film of the easy - adhesive layer material is heated at a temperature of 110°C for 60 seconds to form an easy - adhesive layer (i) on the substrate film (i). Thus, a multilayer body (I) having a layer structure of (substrate film (i)) / (easy - adhesive layer (i)) is obtained. The obtained multilayer body (I) is wound around a roll and recovered.

[0273] (1 - 4. Multilayer body (II))

[0274] The multilayer body (I) is unrolled from the roll.

[0275] The unrolled multilayer body (I) is continuously fed to a stretching machine for width - expansion and stretching, and the multilayer body (I) is stretched using the stretching machine for width - expansion. The stretching direction is a direction at an angle of 45° with respect to the width direction of the multilayer body (I). The stretching temperature is 135°C and the stretching ratio is 1.5 times. Through this stretching, a multilayer body (II) having a layer structure of (substrate film (ii)) / (easy - adhesive layer (ii)) is obtained. The substrate film (ii) is a layer obtained by stretching the substrate film (i), and the easy - adhesive layer (ii) is a layer obtained by stretching the easy - adhesive layer (i). The orientation angle of the substrate film (ii) in the multilayer body (II) with respect to the film width direction is 45°, and the in - plane retardation Re of the multilayer body (II) is 215 nm. The thickness of the substrate film (ii) in the multilayer body (II) is 47 μm, and the thickness of the easy - adhesive layer (ii) is 0.085 μm. The obtained multilayer body (II) is wound around a roll and recovered.

[0276] (1 - 5. Bonding layer material)

[0277] Mix the following materials to obtain a liquid aqueous resin with a solid content of 8.5% as an uncured acrylic resin. Use this aqueous resin as the bonding layer material 1.

[0278] Material containing polymer (P2): 14 parts of an aqueous dispersion (solid content concentration 50%) of a methyl methacrylate / butyl acrylate copolymer (polymerization ratio: 60% by weight of methyl methacrylate and 40% by weight of butyl acrylate) as an acrylic resin

[0279] Material containing cross - linker (2): 6 parts of an oxazoline - group - containing (meth)acrylic cross - linker (trade name “EPOCROS WS - 700”, manufactured by Nippon Shokubai Co., Ltd., copolymer of methyl methacrylate and 2 - isopropenyl oxazoline, solid content concentration 25% by weight, amount of oxazoline group 4.5 mmol / (g solid content);

[0280] Wetting agent: 0.5% by weight of an acetylene - based surfactant (“Surfynol 440” manufactured by Air Products and Chemicals, Inc.) relative to the total amount of solid components

[0281] Water: 80 parts

[0282] (1 - 6. Multilayer body (III))

[0283] The multilayer body (II) obtained from the roll unwinding (1 - 4).

[0284] Apply the bonding layer material 1 obtained in (1 - 5) to the surface of the base film (ii) of the unwound multilayer body (II) (i.e., the surface of the easy - adhesion layer (ii)) to form a coating film of the bonding layer material 1. The application is carried out using a reverse gravure roll that rotates in the opposite direction to the film conveyance direction.

[0285] Dry the applied bonding layer material at 120 °C. During drying, cross - link the bonding layer material to form the bonding layer (i). As a result, a long - strip multilayer body (III) with a layer structure of (bonding layer (i)) / (easy - adhesion layer (ii)) / (base film (ii)) is obtained. The total thickness of the bonding layer and the easy - adhesion layer in the obtained multilayer body (III) is 0.205 μm.

[0286] (1 - 7. Multilayer body (IV))

[0287] Prepare a styrene - maleic anhydride copolymer resin (“Daylark D332” manufactured by Nova Chemicals Corporation) as a resin with a negative intrinsic birefringence. In addition, prepare a mixed solvent of methyl ethyl ketone and methyl isobutyl ketone (weight ratio 8:2).

[0288] Dissolve 100 parts of a styrene-maleic anhydride copolymer resin in a mixed solvent, and further add 5 parts of triphenyl phosphate as a plasticizer to obtain a liquid top layer material 1 with a solid content concentration of 15% by weight.

[0289] Coat the surface on the obtained bonding layer (i) side with the top layer material 1 by a die coating method to form a coating film of the top layer material 1.

[0290] After that, dry the formed coating film of the top layer material 1 at 120 °C to form the top layer (i). As a result, a long multi-layer body (IV) having a layer structure of (top layer (i)) / (bonding layer (i)) / (easy-bonding layer (ii)) / (substrate film (ii)) is obtained. The thickness of the top layer in the obtained multi-layer body (IV) is 8 μm. After the obtained multi-layer body (IV) is adhered to a masking film, it is wound around a roller for recovery.

[0291] (1-8. Multi-layer film)

[0292] Continuously supply the unwound multi-layer body (IV) to a longitudinal stretching machine, and stretch the multi-layer body (IV) using the longitudinal stretching machine. The stretching is free uniaxial stretching in the length direction of the multi-layer body (IV). The stretching temperature is 127 °C, and the stretching ratio is 1.4 times. Through this stretching, a long multi-layer film having a layer structure of (top layer (ii)) / (bonding layer (ii)) / (easy-bonding layer (iii)) / (substrate film (iii)) is obtained. The top layer (ii) is a layer obtained by stretching the top layer (i), the bonding layer (ii) is a layer obtained by stretching the bonding layer (i), the easy-bonding layer (iii) is a layer obtained by stretching the easy-bonding layer (ii), and the substrate film (iii) is a layer obtained by stretching the substrate film (ii).

[0293] Visually inspect the appearance of the obtained multi-layer film, and evaluate the presence or absence of the number of foreign matters in the film.

[0294] In addition, evaluate the adhesion of the obtained multi-layer film, and the result shows that all squares are adhered (25 / 25).

[0295] [Example 2]

[0296] In (1-3), adjust the coating conditions of the roll coater to change the thickness of the coating film of the easy-bonding layer material so that the thickness of the easy-bonding layer in the multi-layer film becomes the thickness shown in the table.

[0297] Except for the above matters, operate in the same manner as in Example 1 to obtain a multi-layer film and evaluate it.

[0298] [Example 3]

[0299] In (1-2), as the organic particles (NP), “EPOSTAR MX100W” (weight average particle diameter 150 nm, solid component concentration 10%) manufactured by Nippon Shokubai Co., Ltd. was used instead of “EPOSTAR MX200W” (weight average particle diameter 300 nm) manufactured by Nippon Shokubai Co., Ltd.

[0300] Except for the above matters, the operation was the same as in Example 1 to obtain a multilayer film and evaluate it.

[0301] [Comparative Example 1]

[0302] (1-5) to (1-6) were not carried out.

[0303] In (1-7), a topcoat material 1 was applied to the surface on the adhesive layer (ii) side of the multilayer body (II) obtained in (1-4) to form a coating film of the topcoat material 1.

[0304] Except for the above matters, the operation was the same as in Example 1 to obtain a multilayer film and evaluate it.

[0305] The multilayer film obtained in this example has a layer structure of (top layer (ii)) / (adhesive layer (iii)) / (substrate film (iii)).

[0306] [Comparative Example 2]

[0307] In (1-6), the coating thickness of the adhesive layer material changed by adjusting the coating conditions of the reverse gravure was adjusted so that the thickness of the adhesive layer in the multilayer film became the thickness shown in the table.

[0308] Except for the above matters, the operation was the same as in Example 1 to obtain a multilayer film and evaluate it.

[0309] [Comparative Example 3]

[0310] In (1-2), as the organic particles (NP), “EPOSTAR MX100W” (weight average particle diameter 150 nm, solid component concentration 10%) manufactured by Nippon Shokubai Co., Ltd. was used instead of “EPOSTAR MX200W” (weight average particle diameter 300 nm) manufactured by Nippon Shokubai Co., Ltd.

[0311] In (1-3), the coating thickness of the adhesive layer material was changed by adjusting the coating conditions of the roll coater so that the thickness of the adhesive layer in the multilayer film became the thickness shown in the table.

[0312] Except for the above matters, the operation was the same as in (1-1) to (1-5) of Example 1.

[0313] Next, it was intended to perform the same operations as in (1-6) of Example 1. However, when the multilayer body (II) was unfolded, wrinkles were generated in the multilayer body (II), and thus the application of the bonding layer material could not be carried out, and a multilayer film could not be obtained.

[0314] [Results]

[0315] The thickness of each layer in the multilayer film and the evaluation results of the multilayer film are shown in the following table.

[0316] [Table 1]

[0317] Table 1

[0318] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Thickness of easy - adhesion layer T1 (nm) 70 200 70 70 70 200 Average particle size of organic particles T3 (nm) 300 300 150 300 300 150 (T1 / T3) 0.23 0.67 0.47 0.23 0.23 1.33 Thickness of bonding layer T2 (nm) 100 100 100 - 30 - Thickness (T1 + T2) (nm) 170 300 170 70 100 - Sealability Good Good Good Poor Poor <![CDATA[- *1 > Number of defects 0 3 3 0 0 <![CDATA[- *1 >

[0319] In the table, *1 indicates that when the multilayer body (II) was unfolded in (1-6), wrinkles were generated in the multilayer body (II), and thus the application of the bonding layer material could not be carried out. Since a multilayer film could not be obtained, evaluation could not be performed.

[0320] Based on the above results, the adhesion of the multilayer films of Examples 1 to 3 was evaluated favorably. In addition, it was found that the number of defects in the multilayer film of Example 1 with T1 / T3 of 0.6 or less was 0, and high-standard adhesion and low defects could be achieved.

[0321] On the other hand, the adhesion of the multilayer films of Comparative Examples 1 and 2 with T1+T2 less than 150 nm was evaluated unfavorably.

[0322] It was found that a multilayer film with excellent adhesion could be obtained by the method for producing a multilayer film according to Examples 1 to 3.

[0323] On the other hand, in the method for producing a multilayer film of Comparative Example 3 where T3 was less than T1, i.e., T1 / T3 was greater than 1, the target multilayer film could not be obtained. It was speculated that this was because the slidability of the intermediate multilayer body (II) was insufficient.

Claims

1. A multilayer film having a base film, an easy-bonding layer disposed in direct contact with one surface of the base film, a bonding layer disposed in direct contact with the surface of the easy-bonding layer, and a top layer disposed in direct contact with the surface of the bonding layer, wherein the total thickness (T1 + T2) of the thickness T1 of the easy-bonding layer and the thickness T2 of the bonding layer is 150 nm or more, the easy-bonding layer contains organic particles (NP) having an average particle diameter T3 that is equal to or greater than the thickness T1 of the easy-bonding layer.

2. The multilayer film according to claim 1, wherein, The ratio (T1 / T3) of the thickness T1 of the easy-bonding layer to the average particle diameter T3 of the organic particles (NP) is 0.6 or less.

3. The multilayer film according to claim 1, wherein, The base film contains a cyclic olefin-based polymer.

4. The multilayer film according to claim 1, wherein, The organic particles (NP) are particles of a (meth)acrylic acid polymer.

5. The multilayer film according to claim 1, wherein, The easy-bonding layer is a cured product of an easy-bonding layer material containing the organic particles (NP), a polymer (P1) having a (meth)acrylate unit, and a crosslinking agent (1).

6. The multilayer film according to claim 1, wherein, The bonding layer is a cured product of a bonding layer material containing a polymer (P2) having a (meth)acrylate unit and a crosslinking agent (2).

7. The multilayer film according to claim 1, wherein, The easy-bonding layer is a cured product of an easy-bonding layer material containing the organic particles (NP), a polymer (P1) having a (meth)acrylate unit, and a crosslinking agent (1). The bonding layer is a cured product of a bonding layer material containing a polymer (P2) having a (meth)acrylate unit and a crosslinking agent (2). The polymer (P1) and the polymer (P2) have a common (meth)acrylate unit.

8. The multilayer film according to claim 1, wherein, The top layer is a cured product of a top layer material containing a polymer (P3) having a styrene-based monomer unit.

9. The multilayer film according to claim 1, wherein The multilayer film is a stretched film.

10. A method for manufacturing a multilayer film, the multilayer film being the multilayer film according to any one of claims 1 to 9, the manufacturing method including the following steps: Step (1), preparing a long strip of base film; Step (2-1), coating a liquid easy-bonding layer material on the base film to form a coating film of the easy-bonding layer material; Step (2-2), drying the coating film of the easy-bonding layer material to form an easy-bonding layer, and obtaining a multilayer body (I) having the base film and the easy-bonding layer; Step (3), stretching the multilayer body (I) to obtain a multilayer body (II); Step (4), winding the multilayer body (II); Step (5-1), unwinding the wound multilayer body (II), and coating a liquid bonding layer material on the easy-bonding layer of the multilayer body (II) to form a coating film of the bonding layer material; Step (5-2), drying the coating film of the bonding layer material to form a bonding layer, and obtaining a multilayer body (III) having the base film, the easy-bonding layer, and the bonding layer in sequence; Step (6-1), coating a liquid top layer material on the bonding layer of the multilayer body (III) to form a coating film of the top layer material; Step (6-2), drying the coating film of the top layer material to form a top layer, and obtaining a multilayer body (IV) having the base film, the easy-bonding layer, the bonding layer, and the top layer in sequence; Step (7), stretching the multilayer body (IV) to obtain a multilayer film.