TW202106501A - Multilayer film - Google Patents

Abstract

A multilayer film which has a configuration wherein a cured resin layer (A) and a cured resin layer (B) are sequentially superposed on the surface of a base material film, and which is characterized in that with respect to elastic modulus as determined by measurement using a micro hardness gauge (JIS Z 2255), the elastic modulus of the cured resin layer (B) is higher than the elastic modulus of the of the cured resin layer (A), and the difference between the elastic modulus of the of the cured resin layer (A) and the elastic modulus of the cured resin layer (B) is more than 0 (MPa) but less than 220 (MPa).

Description

Laminated film

The present invention relates to a laminated film with excellent surface hardness and repeated bending characteristics.

In recent years, with the miniaturization and weight reduction of electronic equipment, there is a tendency to use flexible substrates and flexible printed circuits. In addition, with this trend, the requirements for flexibility in display applications tend to increase. In addition, the surface protection film for display screens used for this purpose requires not only high hardness, damage prevention, antifouling, abrasion resistance, and other surface protection properties, but also high durability for flexibility, and further requirements are required. Improve performance.

Therefore, in recent years, many proposals have been made for surface protection films in order to maintain scratch resistance with high hardness and to improve flexibility or bendability. For example, Patent Document 1 discloses the technical content of the hard coat film, that is, in the hard coat layer including the laminated structure, by making the elastic modulus of the intermediate layer larger than the surface layer, the surface hardness is improved and the stress is prevented. The damage state of the hard coating film caused by concentration, so that it is not easy to be damaged.

Patent Document 2 discloses a hard coat layer composed of a free-radical material for the surface layer and a cationic material for the intermediate layer and good interlayer adhesion.

Patent Document 3 discloses the technical content of controlling the elastic modulus of the hard coating film by including silica particles in the coating film.

Patent Document 4 discloses the technical content of the hard coat film, that is, in the hard coat layer including the laminated structure, the elastic modulus of the surface layer is greater than that of the intermediate layer, and the elongation coefficient of the hard coat film is set to a specific range , And excellent wear resistance and flexibility. Prior art literature Patent literature

Patent Document 1: Japanese Patent No. 4574766 Patent Document 2: Japanese Patent No. 4160217 Patent Document 3: Japanese Patent No. 5320848 Patent Document 4: Japanese Patent No. 4569807

[The problem to be solved by the invention]

As mentioned above, in recent years, the development of flexible mobile terminals that can bend or fold the image display screen (display) has been advanced. Regarding the surface protection film used for this type of image display screen, excellent surface hardness is also required, and it is practical. Ground repetitive bending, specifically, for example, durability of repetitive bending more than 200,000 times. However, none of the inventions described in Patent Document 1 to Patent Document 4 envisages the use of repeated bending, and there are situations in which it is difficult to cope with it.

Therefore, the present invention proposes a novel laminated film, which not only has excellent surface hardness, but also has excellent repeated bending characteristics in practical use. [Technical means to solve the problem]

The present invention proposes a laminated film characterized in that it has a structure in which a hardened resin layer (A) and a hardened resin layer (B) are sequentially laminated on the surface of a base film. Regarding the elastic modulus measured by a microhardness tester (JIS Z 2255), the elastic modulus of the hardened resin layer (B) is greater than the elastic modulus of the hardened resin layer (A), and the hardened resin layer (A) The difference between the elastic modulus and the elastic modulus of the hardened resin layer (B) is greater than 0 (MPa) and less than 220 (MPa).

As an example of the manufacturing method of the above-mentioned laminated film, the present invention proposes a method of manufacturing a laminated film, characterized in that the curable resin layer (A) is formed by applying a curable composition on a base film and curing it. And the mass average molecular weight of the curable composition is in the range of 1,000 to 500,000. [Effects of Invention]

The laminated film proposed by the present invention has the following characteristics: it has a structure in which a hardened resin layer (A) and a hardened resin layer (B) are sequentially laminated on the surface of a base film, and the elastic modulus and hardening of the hardened resin layer (A) The difference ((B)-(A)) of the elastic modulus of the resin layer (B) is greater than 0 (MPa) and less than 220 (MPa). Therefore, it is possible to maintain the surface hardness and improve the practical repetitive bending characteristics. Specifically, it is possible to obtain excellent repetitive bending characteristics that are not problematic even if it is repeatedly bent more than 200,000 times.

Next, the present invention will be described based on embodiment examples. However, the present invention is not limited to the embodiments described below.

＜＜The laminated film＞＞ The laminated film (referred to as the "this laminated film") of an example of the embodiment of the present invention is provided with a hardened resin layer (A) and a laminated film on at least one side surface of a base film (referred to as "this base film") and A laminated film composed of hardened resin layer (B). In addition, as long as this laminated film has the said structure, you may have another layer.

＜The base film＞ The material and structure of the base film are not limited as long as the film can obtain the required sufficient rigidity and repetitive flexibility.

The base film may have a single-layer structure or a multilayer structure. When the base film has a multilayer structure, in addition to a two-layer or three-layer structure, as long as it does not exceed the gist of the present invention, it may have four or more layers.

The base film may be a single-layer structure or a multilayer structure, and the main component resin of each layer is preferably polyester or polyimide (PI). This kind of film is called "polyester film" or "polyimide film". At this time, the "main component resin" refers to the resin with the largest content in the resin constituting the base film, for example, it occupies 50% by mass or more, especially 70% by mass or more, especially 80% by mass in the resin constituting the base film. Resin with a mass% or more (including 100% by mass). Furthermore, as long as the main component resin of each layer constituting the base film is polyester or polyimide, it may contain other resins or components other than resins other than polyester or polyimide.

(Polyester) The polyester (referred to as "this polyester") as the main component resin of each layer constituting the base film may be a homopolyester or a copolyester.

When the polyester contains a homopolyester, it is preferably obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic diol. As said aromatic dicarboxylic acid, terephthalic acid, 2, 6-naphthalenedicarboxylic acid, etc. are mentioned. As said aliphatic diol, ethylene glycol, diethylene glycol, 1, 4- cyclohexane dimethanol, etc. are mentioned.

On the other hand, when the polyester is a copolyester, as its dicarboxylic acid component, for example, isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid One or two or more of, sebacic acid, etc. On the other hand, as its glycol component, for example, one or two of ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, etc. the above.

As specific examples of representative polyesters, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), poly Butylene naphthalate (PBN), polyethylene furandicarboxylate (PEF), etc. Among them, PET and PEN are better in terms of operability. In addition, when the main component resin of each layer constituting the base film is, for example, polyethylene terephthalate, the film is referred to as a "polyethylene terephthalate film." The same is true when other resins are the main component resins.

(Polyimide) In addition to the polyester film, the base film is also suitably a polyimide film. Regarding the imidization of the above-mentioned polyimine, for example, the following method is exemplified: after polyimide acid is polymerized in an equivalent ratio of 1:1 between diamine and dianhydride, especially aromatic dianhydride and aromatic diamine, Carry out imidization. Examples of the aromatic dianhydride include 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4-(2,5-dioxotetrahydrofuran-3-yl) -1,2,3,4-Tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), pyromellitic dianhydride (1,2,4,5-benzenetetracarboxylic dianhydride, PMDA) , Benzophenone tetracarboxylic dianhydride (BTDA), biphenyl tetracarboxylic dianhydride (BPDA), and bis (carboxyphenyl) dimethyl silan dianhydride (SiDA), etc. These may be used alone, or two or more of them may be used in combination. In addition, as the above-mentioned aromatic diamine, oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p-methylene diphenylamine (pMDA), m-methylene diamine can be exemplified Aniline (mMDA), bistrifluoromethylbenzidine (TFDB), cyclohexanediamine (13CHD, 14CHD), and diaminohydroxyphenyl hexafluoropropane (DBOH), etc. These may be used alone, or two or more of them may be used in combination.

(Other resin components) Each layer constituting the base film may have other resins other than polyester and polyimide as the main component resin. As the main component resin in this case, for example, epoxy resin, polyarylate, polyether sulfide, polycarbonate, polyether ketone, poly sulfide, polyphenylene sulfide, polyester-based liquid crystal polymer, triethyl Cellulose, cellulose derivatives, polypropylene, polyamides, polycyclic olefins, etc.

(particle) The base film may also contain particles, the main purpose of which is to impart slipperiness to the film surface and prevent damage in each step. The kind of particles is not particularly limited as long as they are particles that can impart slipperiness. For example, inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, alumina, and titanium oxide, acrylic resin, styrene resin, urea resin, phenol resin, Organic particles such as epoxy resin and benzoguanamine resin. These can be used individually by 1 type, and 2 or more types of these can also be used in combination. Furthermore, in the polyester production step, it is also possible to use precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst.

The shape of the aforementioned particles is not particularly limited. For example, it may be any of a spherical shape, a block shape, a rod shape, and a flat shape. In addition, the hardness, specific gravity, color, etc. of the above-mentioned particles are also not particularly limited. These series of particles can also be used in combination of two or more types as needed.

The average particle diameter of the above-mentioned particles is preferably 5 μm or less, more preferably 0.01 μm or more or 3 μm or less, and more preferably 0.5 μm or more or 2.5 μm or less. When it exceeds 5 μm, there are cases where the surface roughness of the base film is too rough, and defects occur when a hardened resin layer containing various hardening compositions is formed in a subsequent step.

The content of the particles is preferably 5% by mass or less of the base film, among them, 0.0003% by mass or more or 3% by mass or less, and more preferably 0.01% by mass or more or 2% by mass or less. If the average particle size of the particles is within the above range, the surface roughness of the base film will not be too rough, so it is possible to suppress defects when forming a hardened resin layer containing various hardening compositions in subsequent steps. Happening.

The method of adding particles to the base film is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage in the production of raw material resins such as polyester. In the case of polyester, it is preferably added after the end of the esterification or transesterification reaction.

(Other ingredients) The base film may optionally contain, for example, previously known antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, ultraviolet absorbers, etc., as other components.

(thickness) The thickness of the base film is, in terms of obtaining the required and sufficient rigidity and repetitive flexibility, for example, it is preferably 9 μm to 125 μm, more preferably 12 μm or more or 100 μm or less, and more preferably 20 μm or more or 75 μm or less.

(Preparation method) The present base film can be formed by, for example, molding the resin composition into a film shape by a melt film forming method or a solution film forming method. In the case of multilayer structure, it can also be co-extrusion. In addition, it may be obtained by uniaxial stretching or biaxial stretching. In terms of rigidity, a biaxially stretched film is preferable.

(Characteristics of this base film) The tensile elastic modulus (JIS K 7161) of the base film is preferably 2.0 GPa or more, preferably 9.0 GPa or less, in terms of obtaining the required sufficient rigidity and repetitive bendability. It is 3.0 GPa or more or 8.0 GPa or less, and among them, it is more preferably 3.0 GPa or more or 7.0 GPa or less.

＜Cured resin layer (A), (B)＞ This laminated film has a laminated structure in which a hardened resin layer (A) is provided on at least one side of the base film, and a hardened resin layer (B) is provided on the surface side of the hardened resin layer (A). to make. Furthermore, the cross-linked resin layer refers to a layer having a cross-linked resin structure. Regarding whether it has a cross-linked resin structure, TOFSIMS (time of flight secondary ion mass spectrometry) and IR (infrared radiation) devices can be used to analyze the crystal structure to determine whether there is a cross-linked resin structure. But it is not limited to this method.

(Elastic modulus of each layer) The hardened resin layers (A) and (B) are layers containing hardened resin. In other words, they are layers containing a resin with a crosslinked structure. Preferably, the elastic modulus of the hardened resin layer (A) is lower than that of the hardened resin The elastic modulus of layer (B). Furthermore, with regard to the modulus of elasticity measured by a microhardness tester (JIS Z 2255), the difference between the modulus of elasticity of the hardened resin layer (A) and that of the hardened resin layer (B) (hardened The elastic modulus of the resin layer (B)-the elastic modulus of the hardened resin layer (A)) is greater than 0 (MPa) and less than 220 (MPa). When there is only the hardened resin layer (B) on at least one side surface of the base film, the laminate film cannot withstand deformation when an external force is applied to the laminate film, resulting in damage to the laminate film surface or irreversible cracks. On the contrary, make the elastic modulus of the hardened resin layer (A) lower than that of the hardened resin layer (B), and the difference between the elastic modulus of the hardened resin layer (A) and the elastic modulus of the hardened resin layer (B) is greater than 0 (MPa) and less than 220 (MPa), thereby avoiding stress concentration, and further, by deforming the hardened resin layer (A) to absorb external force. Therefore, a laminated film with excellent repeated bending characteristics can be produced.

Among them, the difference between the above-mentioned elastic modulus of the hardened resin layer (A) and the hardened resin layer (B) is more preferably 50 MPa or more, more preferably 100 MPa or more from the viewpoint of flexibility, and particularly More preferably, it is 150 MPa or more. On the other hand, from the viewpoint of surface hardness, the difference is preferably 210 MPa or less, among them, 200 MPa or less is more preferable, and among them, 190 MPa or less is more preferable.

In addition, with regard to the elastic modulus measured by a microhardness tester (JIS Z 2255), it is preferable that the hardened resin layer (B)>the hardened resin layer (A)≧10 MPa. When there is only the hardened resin layer (B) on at least one side surface of the base film, the laminate film cannot withstand deformation when an external force is applied to the laminate film, resulting in damage to the laminate film surface or irreversible cracks. In contrast, this laminated film has a hardened resin layer (A) that satisfies hardened resin layer (B)> hardened resin layer (A)≧10 MPa as the lower layer of hardened resin layer (B), which can avoid stress concentration. . Furthermore, external force can be absorbed by deforming the hardened resin layer (A). Therefore, a laminated film with excellent repeated bending characteristics can be produced.

From the above viewpoint, the modulus of elasticity of the cured resin layer (A) is more preferably 20 MPa or more, particularly preferably 50 MPa or more, and particularly more preferably 100 MPa or more. On the other hand, the upper limit is preferably 495 MPa or less, particularly 400 MPa or less, and even more preferably 350 MPa or less.

On the other hand, the above-mentioned elastic modulus of the cured resin layer (B) is preferably 100 MPa or more from the viewpoint of surface hardness, particularly preferably 200 MPa or more, and even more preferably 300 MPa or more. On the other hand, it is preferably 900 MPa or less, of which 800 MPa or less is more preferable, and even more preferably, it is 700 MPa or less.

(Adjustment method of elastic modulus of each layer) The modulus of elasticity of the hardened resin layer (A) and hardened resin layer (B) can be changed by changing the thickness of each layer, the content of particles, the selection of curable monomers, the composition ratio of curable monomers, and the content of crosslinkable monomers. The ratio, crosslinking density (molecular weight between crosslinking points), the molecular weight of the base polymer forming each layer or the molecular weight of the hardened resin composition forming each layer are adjusted. But it is not limited to these methods. Furthermore, the "base polymer" in the present invention means the resin with the highest mass ratio among the resins constituting each layer.

(Thickness of each layer) By changing the thickness of each of the hardened resin layers (A) and (B), not only the elastic modulus of the hardened resin layers (A) and (B) can be adjusted, but also the surface hardness can be improved. For example, by making the thickness of the hardened resin layer (B) greater than the thickness of the hardened resin layer (A), the surface hardness can be increased. The thickness of the hardened resin layer (A) is preferably 10 to 300% of the thickness of the hardened resin layer (B), among which 20% or more or 200% or less is more preferable, and 30% or more or 100% or less is more preferable.

On the basis of satisfying the above relationship, the thickness of the cured resin layer (A) is preferably 1.0 μm or more and 30.0 μm or less. If it is 1.0 μm or more, for example, when the cured resin layer (A) is cured by irradiating ultraviolet rays, insufficient curing due to oxygen hindrance or the like can be prevented. On the other hand, if it is 30.0 μm or less, it is easy to ensure the surface smoothness of the laminated film, and it is easy to ensure transparency. From this point of view, the thickness of the layer is preferably 1.0 μm or more and 30.0 μm or less, particularly preferably 20.0 μm or less, particularly preferably 10.0 μm or less, and even more preferably 5.0 μm or less. On the other hand, the thickness of the hardened resin layer (B) is preferably 1.0 μm or more and 30.0 μm or less, more preferably 20.0 μm or less, particularly preferably 10.0 μm or less, and particularly further preferably 5 μm or less.

Furthermore, the total thickness of the cured resin layer (A) and the cured resin layer (B) may be 20.0 μm or less, preferably 10.0 μm or less, and more preferably 8.0 μm or less from the viewpoint of flexibility. It is preferably 6.0 μm or less, and particularly preferably 5.0 μm or less.

(Particle content of each layer) In addition, it can be adjusted so that the hardened resin layer (A) does not contain particles, on the other hand, the hardened resin layer (B) contains particles, or the hardened resin layer (A) has a smaller particle content than the hardened resin layer (B), The elastic modulus of the hardened resin layer (B) is higher than that of the hardened resin layer (A). As a specific example of the latter, the particle content of the hardened resin layer (A) can be set to 1% by mass to 20% by mass, and on the other hand, the particle content of the hardened resin layer (B) can be set to 20% by mass to 60% by mass. , And adjust the elastic modulus of each layer. At this time, the content of particles in the hardened resin layer (A) is 1% by mass or more, preferably 2% by mass or more, and more preferably 5% by mass or more, and on the other hand, 20% by mass or less, which is more preferable It is 15% by mass or less, and among them, it is more preferably 10% by mass or less. On the other hand, the particle content of the hardened resin layer (B) is 20% by mass or more, preferably 25% by mass or more, and more preferably 30% by mass or more, and on the other hand, 60% by mass or less. It is preferably 55% by mass or less, and more preferably 50% by mass or less. Furthermore, the types of particles contained in the cured resin layer (A) and the cured resin layer (B) will be described below.

(Surface state of each layer) The surface of the hardened resin layer (A) may be uneven or flat. Among them, from the viewpoint of appearance (surface gloss), it is preferably flat. On the other hand, the surface of the cured resin layer (B) may be uneven or flat. Among them, from the viewpoint of appearance (surface gloss), it is preferably flat.

(Optical properties of each layer) In consideration of optical use, both of the cured resin layers (A) and (B) are preferably transparent.

Among them, in order to improve visibility at a high level, the difference in refractive index between the cured resin layer (A) and the cured resin layer (B) is preferably 0.15 or less. If the refractive index difference between the cured resin layer (A) and the cured resin layer (B) is 0.15 or less, the visibility can be improved. Specifically, when visually observing from an angle inclined at 45 degrees with respect to the film surface, the outline from the cured resin layer (A) is not easily observed. From this viewpoint, the difference in refractive index between the cured resin layer (A) and the cured resin layer (B) is preferably 0.15 or less, more preferably 0.10 or less, and even more preferably 0.05 or less. The lower limit of the refractive index difference is zero.

＜＜The manufacturing method of this laminated film＞＞ Both the hardened resin layer (A) and the hardened resin layer (B) can be formed by hardening a curable composition, that is, a composition having properties that can be hardened. More specifically, the curable composition is applied to at least one side surface of the base film and cured to form a cured resin layer (A), and then the curable composition is applied on the cured resin layer (A) And it is hardened to form a hardened resin layer (B), by which this laminated film can be manufactured. At this time, the hardening of the hardened resin layer (A) and the hardened resin layer (B) can also be carried out at the same time. In addition, after the cured resin layer (A) is formed, the film can be temporarily wound into a roll shape, and then the film is rolled out again, and the curable composition is applied on the cured resin layer (A) and cured to form a cured For the resin layer (B), after the hardened resin layer (A) is formed on the surface of the base film, the curable composition may be continuously applied and hardened to form the hardened resin layer (B). The manufacturing method of the laminated film is not limited by this method.

＜Curable composition＞ The curable composition used to form the cured resin layer (A) and the cured resin layer (B) preferably contains a photopolymerization initiator, solvent, particles, crosslinking agent, and other components in addition to the curable monomer as necessary . Hereinafter, each of them will be explained.

By making the mass average molecular weight of the base polymer forming the hardened resin layer (A), that is, the curable monomer, or the mass average molecular weight of the hardening resin composition forming the hardened resin layer (A) larger than that of the hardened resin layer (B) The base polymer, the mass average molecular weight of the curable monomer or the mass average molecular weight of the curable resin composition forming the hardened resin layer (B), can be adjusted so that the elastic modulus of the hardened resin layer (B) is higher than that of the hardened resin Layer (A). Among them, to reduce the total thickness of the cured resin layers (A) and (B), for example, the total thickness of the cured resin layers (A) and (B) is set to 30 μm or less, of which 20 μm or less, especially 10 μm or less , And can maintain the surface hardness and improve the repeated bending characteristics, by making the mass average molecular weight of the base polymer forming the hardened resin layer (A) or the mass of the hardening resin composition forming the hardened resin layer (A) The average molecular weight is more than one digit greater than the mass average molecular weight of the base polymer forming the hardened resin layer (B) or the mass average molecular weight of the curable resin composition forming the hardened resin layer (B), that is, set to 10 times or more, or It can be adjusted so that the elastic modulus of the hardened resin layer (B) is higher than that of the hardened resin layer (A).

From this point of view, the mass average molecular weight of the base polymer that forms the hardened resin layer (A), that is, the curable monomer, or the mass average molecular weight of the curable resin composition that forms the hardened resin layer (A), is preferably 1,000 or more Among them, it is preferably 3,000 or more, and among them, it is more preferably 5,000 or more. On the other hand, it is preferably 500,000 or less, of which 400,000 or less is more preferable, and among them, 250,000 or less is more preferable. On the other hand, the mass average molecular weight of the base polymer that forms the hardened resin layer (B), that is, the curable monomer, or the mass average molecular weight of the curable resin composition that forms the hardened resin layer (B), is preferably 100 or more, wherein Preferably it is 200 or more, and among them, it is more preferably 400 or more. On the other hand, it is preferably 500,000 or less, of which 400,000 or less is more preferable, and among them, 250,000 or less is more preferable.

(Curable monomer) The above-mentioned curable monomer may be a compound capable of curing. Among them, it is preferable to contain one or more selected from the group consisting of crosslinkable monomers, acrylic esters, and methacrylic esters from the viewpoint of achieving both excellent surface hardness and repeated bending properties. Among them, from the viewpoints of handling properties, ease of industrial availability, and cost, it is preferable to include a blend of at least two selected from crosslinkable monomers and (meth)acrylates, or to include A mixture of at least two types of methacrylates and vinyl monomers. As described above, when two types of monomers (a/b) are used, the blending ratio (a/b) is preferably in the range of 90/10 to 10/90 in terms of mass ratio, and more preferably 80/ The range is 20-40/60, and the range of 70/30-40/60 is preferable.

Furthermore, in the present invention, when the expression "(meth)acrylic acid" is used, it refers to one or both of "acrylic acid" and "methacrylic acid". The same applies to "(meth)acrylate" and "(meth)acryloyl". In addition, "(poly)propylene glycol" refers to one or both of "propylene glycol" and "polypropylene glycol". "(Poly)ethylene glycol" also has the same meaning.

It is preferable to select each main component from these mixtures so that each of the hardened resin layer (A) and the hardened resin layer (B) satisfies at least the above-mentioned elastic modulus and refractive index. Among them, the curable monomer used in the curable composition for forming the curable resin layer (A) is preferably selected so as to satisfy the above-mentioned elastic modulus and refractive index. On the other hand, the curable monomer used in the curable composition for forming the curable resin layer (B) is preferably selected so as to satisfy the above-mentioned elastic modulus and refractive index.

(Crosslinkable monomer) The above-mentioned crosslinkable single system refers to a monomer having one or more polymerizable functional groups in one molecule. As the crosslinkable monomer, for example, allyl acrylate, allyl methacrylate, 1-acryloxy-3-butene, 1-methacryloxy-3-butene, 1,2-Dipropenyloxyethane, 1,2-dimethylpropenyloxyethane, 1,2-dipropenyloxypropane, 1,3-dipropenyloxypropane, 1, 4-dipropenyloxybutane, 1,3-dimethylpropenyloxypropane, 1,2-dimethylpropenyloxypropane, 1,4-dimethylpropenyloxybutane, Triethylene glycol dimethacrylate, polyethylene glycol diacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, triethylene glycol diacrylate Esters, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, 1,4-pentadiene, trimethylolpropane triacrylate, etc.

In addition, examples of hydroxyl-containing (meth)acrylate compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate Esters, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate and other hydroxyalkyl (meth)acrylates, 2-hydroxyethyl acryloyl phosphate, phthalic acid 2 -(Meth)acryloyloxyethyl-2-hydroxypropyl, caprolactone-modified 2-hydroxyethyl (meth)acrylate, dipropylene glycol (meth)acrylate, fatty acid modified-(methyl) ) Glycidyl acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-(meth)acryloxypropyl (meth)acrylate, etc. (Meth)acrylate compounds containing one ethylenically unsaturated group; glycerol di(meth)acrylate, 2-hydroxy-3-propenoxypropyl methacrylate, etc. contain two ethylenically unsaturated groups Base (meth)acrylate compounds; pentaerythritol tri(meth)acrylate, caprolactone modified pentaerythritol tri(meth)acrylate, ethylene oxide modified pentaerythritol tri(meth)acrylate, two Pentaerythritol penta(meth)acrylate, caprolactone modified dipentaerythritol penta(meth)acrylate, ethylene oxide modified dipentaerythritol penta(meth)acrylate, etc. containing more than 3 ethylenically unsaturated groups (Meth) acrylate-based compounds, etc.

As a crosslinkable monomer having a vinyl group, for example, glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, o-vinylbenzyl glycidyl ether, m-vinylbenzyl Glycidyl ether, p-vinylbenzyl glycidyl ether, α-methyl o-vinylbenzyl glycidyl ether, α-methyl m-vinylbenzyl glycidyl ether, α-methyl p-vinylbenzyl glycidyl ether Glyceryl ethers, among which, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, and (meth)acrylic acid-3,4-epoxycyclohexyl methyl ester can be exemplified . These may be used alone, or two or more of them may be used in combination.

(Acrylic) As the above-mentioned acrylates, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, second butyl acrylate, third butyl acrylate, Amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate and other non-cyclic alkyl acrylates; cyclohexyl acrylate, iso-acrylate Cyclic alkyl acrylates such as 𦯉yl esters; aryl acrylates such as phenyl acrylate and naphthyl acrylate; 2-hydroxyethyl acrylate, 2-methoxyethyl acrylate, glycidyl acrylate and other acrylic acid containing functional groups Non-cyclic alkyl esters and the like.

(Methacrylates) Examples of the above-mentioned methacrylates include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate. Ester, second butyl methacrylate, third butyl methacrylate, pentyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid Non-cyclic alkyl methacrylates such as pentadecyl ester and dodecyl methacrylate; Cyclic alkyl methacrylates such as cyclohexyl methacrylate and isopropyl methacrylate; A Aryl methacrylate such as phenyl acrylate; 2-hydroxyethyl methacrylate, 2-methoxyethyl methacrylate, glycidyl methacrylate and other functional group-containing non-cyclic methacrylic acid Base ester and so on. These may be used alone, or two or more of them may be used in combination.

(Photopolymerization initiator) In the case of photocuring the above-mentioned curable composition, it is preferable to prepare a photopolymerization initiator.

、異丙基𠮿酮、2,4-二乙基-9-氧硫𠮿

、2-乙基蒽醌、苯乙酮、2-羥基-2-甲基苯丙酮、2-羥基-2-甲基-4'-異丙基苯丙酮、1-羥基環己基苯基酮、安息香異丙醚、安息香異丁醚、2,2-二乙氧基苯乙酮、2,2-二甲氧基-2-苯基苯乙酮、樟腦醌、苯并蒽酮、2-甲基-1-[4-(甲硫基)苯基]-2-𠰌啉基丙烷-1-酮、2-苄基-2-二甲胺基-1-(4-𠰌啉基苯基)-丁酮-1、4-二甲胺基苯甲酸乙酯、4-二甲胺基苯甲酸異戊酯、4,4'-二(第三丁基過氧基羰基)二苯甲酮、3,4,4'-三(第三丁基過氧基羰基)二苯甲酮、3,3',4,4'-四(第三丁基過氧基羰基)二苯甲酮、3,3',4,4'-四(第三己基過氧基羰基)二苯甲酮、3,3'-二(甲氧基羰基)-4,4'-二(第三丁基過氧基羰基)二苯甲酮、3,4'-二(甲氧基羰基)-4,3'-二(第三丁基過氧基羰基)二苯甲酮、4,4'-二(甲氧基羰基)-3,3'-二(第三丁基過氧基羰基)二苯甲酮、1,2-辛二酮,1-[4-(苯硫基)苯基]-,2-(鄰苯甲醯基肟)、2-(4'-甲氧基苯乙烯基)-4,6-雙(三氯甲基)-對稱三𠯤、2-(3',4'-二甲氧基苯乙烯基)-4,6-雙(三氯甲基)-對稱三𠯤、2-(2',4'-二甲氧基苯乙烯基)-4,6-雙(三氯甲基)-對稱三𠯤、2-(2'-甲氧基苯乙烯基)-4,6-雙(三氯甲基)-對稱三𠯤、2-(4'-戊氧基苯乙烯基)-4,6-雙(三氯甲基)-對稱三𠯤、4-[對-N,N-二(乙氧基羰基甲基)]-2,6-二(三氯甲基)-對稱三𠯤、1,3-雙(三氯甲基)-5-(2'-氯苯基)-對稱三𠯤、1,3-雙(三氯甲基)-5-(4'-甲氧基苯基)-對稱三𠯤、2-(對二甲胺基苯乙烯基)苯并㗁唑、2-(對二甲胺基苯乙烯基)苯并噻唑、2-巰基苯并噻唑、3,3'-羰基雙(7-二乙基胺基香豆素)、2-(鄰氯苯基)-4,4',5,5'-四苯基-1,2'-聯咪唑、2,2'-雙(2-氯苯基)-4,4',5,5'-四(4-乙氧基羰基苯基)-1,2'-聯咪唑、2,2'-雙(2,4-二氯苯基)-4,4',5,5'-四苯基-1,2'-聯咪唑、2,2'-雙(2,4-二溴苯基)-4,4',5,5'-四苯基-1,2'-聯咪唑、2,2'-雙(2,4,6-三氯苯基)-4,4',5,5'-四苯基-1,2'-聯咪唑、3-(2-甲基-2-二甲胺基丙醯基)咔唑、3,6-雙(2-甲基-2-𠰌啉基丙醯基)-9-正十二烷基咔唑、1-羥基環己基苯基酮、雙(η5-2,4-環戊二烯-1-基)-雙(2,6-二氟-3-(1H-吡咯-1-基)-苯基)鈦、雙(2,4,6-三甲基苯甲醯基)苯基氧化膦、或2,4,6-三甲基苯甲醯基二苯基氧化膦等。該等光聚合起始劑可僅使用1種，亦可使用2種以上。The photopolymerization initiator is not particularly limited. For example, a ketone-based photopolymerization initiator, an amine-based photopolymerization initiator, etc. may be mentioned. Specifically, for example, benzophenone, Michelanone, 4,4'-bis(diethylamino)benzophenone, ketone, 9-oxysulfur 𠮿

, Isopropyl ketone, 2,4-diethyl-9-oxysulfur

, 2-ethylanthraquinone, acetophenone, 2-hydroxy-2-methylpropiophenone, 2-hydroxy-2-methyl-4'-isopropylpropiophenone, 1-hydroxycyclohexylphenylketone, Benzoin isopropyl ether, benzoin isobutyl ether, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, camphorquinone, benzoanthrone, 2-methyl -1-[4-(methylthio)phenyl]-2-𠰌line propan-1-one, 2-benzyl-2-dimethylamino-1-(4-𠰌line phenyl) -Butanone-1, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 4,4'-bis(tert-butylperoxycarbonyl)benzophenone, 3,4,4'-tris(tert-butylperoxycarbonyl)benzophenone, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, 3 ,3',4,4'-tetrakis(third hexylperoxycarbonyl)benzophenone, 3,3'-bis(methoxycarbonyl)-4,4'-bis(tertiary butylperoxy) Carbonyl)benzophenone, 3,4'-bis(methoxycarbonyl)-4,3'-bis(tertiary butylperoxycarbonyl)benzophenone, 4,4'-bis(methyl Oxycarbonyl)-3,3'-bis(tert-butylperoxycarbonyl)benzophenone, 1,2-octanedione, 1-[4-(phenylthio)phenyl]-,2 -(O-benzyl oxime), 2-(4'-Methoxystyryl)-4,6-bis(trichloromethyl)-symmetric three 𠯤, 2-(3',4'-two Methoxystyryl)-4,6-bis(trichloromethyl)-symmetric tris, 2-(2',4'-dimethoxystyryl)-4,6-bis(trichloro (Methyl)-symmetric tris, 2-(2'-methoxystyryl)-4,6-bis(trichloromethyl)-symmetric tris, 2-(4'-pentoxystyryl) )-4,6-bis(trichloromethyl)-symmetric tris, 4-[p-N,N-bis(ethoxycarbonylmethyl)]-2,6-bis(trichloromethyl)- Symmetrical tris, 1,3-bis(trichloromethyl)-5-(2'-chlorophenyl)-symmetrical tris, 1,3-bis(trichloromethyl)-5-(4'-methyl (Oxyphenyl)-symmetric three 𠯤, 2- (p-dimethylamino styryl) benzo azole, 2- (p-dimethylamino styryl) benzothiazole, 2-mercaptobenzothiazole, 3,3'-carbonylbis(7-diethylaminocoumarin), 2-(o-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole , 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetra(4-ethoxycarbonylphenyl)-1,2'-biimidazole, 2,2'- Bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4-dibromophenyl) -4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4,6-trichlorophenyl)-4,4',5,5 '-Tetraphenyl-1,2'-biimidazole, 3-(2-methyl-2-dimethylaminopropyl)carbazole, 3,6-bis(2-methyl-2-𠰌 Linylpropionyl)-9-n-dodecylcarbazole, 1-hydroxycyclohexyl phenyl ketone, bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6- Difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium, bis(2,4,6-trimethylbenzyl)phenylphosphine oxide, or 2,4,6-trimethyl Benzyl diphenyl phosphine oxide and the like. Only one type of these photopolymerization initiators may be used, or two or more types may be used.

In addition, if necessary, a sensitizer and a light curing initiator may be used in combination. As specific examples of the sensitizer, aliphatic amines such as n-butylamine, triethylamine, and ethyl p-dimethylaminobenzoate, aromatic amines, and the like can be exemplified.

The content of the photopolymerization initiator is preferably in the range of 1 to 10 parts by mass with respect to 100 parts by mass of the curable composition. More preferably, it is in the range of 1 to 5 parts by mass. By making the content of the photopolymerization initiator 1 part by mass or more, the desired polymerization initiation effect can be obtained, and by making the content of the photopolymerization initiator less than 10 parts by mass, the yellowing of the resin layer can be suppressed. change. The photocuring initiator and the sensitizer are preferably used at a ratio of 20% by mass or less based on the solid content of the photocurable composition.

(Solvent) Examples of the above-mentioned solvent include ketone solvents such as methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, diacetone alcohol, and acetone; pentanol, Alcohol solvents such as hexanol, heptanol, and octanol; ether solvents such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, and propylene glycol monomethyl ether acetate; methyl acetate , Ethyl acetate, butyl acetate, methoxybutyl acetate, pentyl acetate, propyl acetate, ethyl lactate, methyl lactate, butyl lactate and other ester solvents; toluene, xylene, solvent naphtha, Organic solvents such as hydrocarbon solvents such as hexane, cyclohexane, ethylcyclohexane, methylcyclohexane, heptane, octane, and decane. These organic solvents may be used alone, or two or more of them may be used in combination.

(particle) In order to improve lubricity and agglomeration, and to adjust the elastic modulus of each layer, the curable composition may contain a specific amount of particles. Examples of the particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, alumina, and titanium oxide, acrylic resin, styrene resin, and urea. Organic particles such as resin, phenol resin, epoxy resin, benzoguanamine resin, etc. These can be used individually by 1 type, and 2 or more types of these can also be used in combination. Furthermore, in the polyester production step, it is also possible to use precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst.

The shape of the aforementioned particles is not particularly limited. For example, it may be any of a spherical shape, a block shape, a rod shape, and a flat shape. In addition, the hardness, specific gravity, color, etc. of the above-mentioned particles are also not particularly limited. These series of particles can also be used in combination of two or more types as needed.

If the average particle size of the above-mentioned particles is too large, there will be cases where the surface roughness is too rough, and defects will occur when a hardened resin layer containing various hardening compositions is formed in a subsequent step. On the other hand, if it is too small, The effect of the addition of particles is reduced, so it is preferably 5 μm or less, among them, 0.01 μm or more or 3 μm or less, and even more preferably 0.5 μm or more or 2.5 μm or less.

(Crosslinking agent) From the viewpoint of improving chemical resistance or improving elastic modulus, it is preferable to formulate a crosslinking agent. The cross-linking agent mentioned here refers to those other than the above-mentioned cross-linkable monomers. As this crosslinking agent, an azoline compound, an isocyanate compound, an epoxy compound, a melamine compound, a carbodiimide compound etc. are mentioned, for example. Among them, from the viewpoint of improving adhesiveness, it is more preferable to use at least one of an azoline compound or an isocyanate compound.

(Azoline compound) The oxazoline compound used in the crosslinking agent is a compound having an oxazoline group in the molecule, and is particularly preferably a polymer containing an oxazoline group, which can be carried out by a monomer containing an addition polymerizable oxazoline group It is produced by homopolymerization or polymerization with other monomers. As the monomer containing an addition polymerizable oxazoline group, for example, 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, etc., can use one or a mixture of two or more of them. Among them, 2-isopropenyl-2-oxazoline is also easy to obtain industrially, so it is more suitable. The above-mentioned other monomers are not limited as long as they can be copolymerized with monomers containing addition polymerizable oxazoline groups. For example, examples include: (meth)acrylic acid alkyl esters (as the alkyl group, there is a methyl group). , Ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, 2-ethylhexyl, cyclohexyl) and other (meth)acrylates; acrylic acid, methacrylic acid, Iraq Unsaturated carboxylic acids such as aconic acid, maleic acid, fumaric acid, crotonic acid, styrene sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); acrylonitrile, methacrylic acid Unsaturated nitriles such as nitrile; (meth)acrylamide, N-alkyl(meth)acrylamide, N,N-dialkyl(meth)acrylamide (as the alkyl group, there are methyl, Unsaturated amines such as ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, 2-ethylhexyl, cyclohexyl, etc.); vinyl acetate, vinyl propionate, etc. Vinyl esters; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride and vinylidene chloride; As for α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene, one or two or more of these monomers can be used.

From the viewpoint of improving the adhesion, the amount of the oxazoline group of the azoline compound is preferably 0.5 to 10 mmol/g, of which 1 mmol/g or more or 9 mmol/g or less is more preferable, and 3 is more preferable. mmol/g or more or 8 mmol/g or less, and more preferably 4 mmol/g or more or 6 mmol/g or less.

(Isocyanate compound) The above-mentioned isocyanate compound used in the crosslinking agent is, for example, a compound having an isocyanate derivative structure represented by an isocyanate or a blocked isocyanate. Examples of the isocyanate include aromatic isocyanates such as toluene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, and α,α,α',α'- Aliphatic isocyanate with aromatic ring such as tetramethylxylylene diisocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate Aliphatic isocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis(4-cyclohexyl isocyanate), isopropylidene dicyclohexyl diisocyanate and other alicyclic rings Group isocyanate and so on. In addition, polymers or derivatives of these isocyanates such as biuret, isocyanurate, uretdione, and modified carbodiimide can also be cited. These can be used alone or in combination. Among the above-mentioned isocyanates, aliphatic isocyanates or alicyclic isocyanates are suitable as a countermeasure against yellowing caused by ultraviolet irradiation.

When used in the state of blocked isocyanate, as the blocking agent, for example, bisulfites, phenolic compounds such as phenol, cresol, and ethyl phenol, propylene glycol monomethyl ether, ethylene glycol , Benzyl alcohol, methanol, ethanol and other alcoholic compounds, methyl isobutyryl acetate, dimethyl malonate, diethyl malonate, methyl acetylacetate, ethyl acetate, acetone, etc. Methylene-based compounds, thiol-based compounds such as butanethiol and dodecyl mercaptan, ε-caprolactam, δ-valerolactam and other internal amide-based compounds, diphenylaniline, aniline, ethylene Amine compounds such as imines, acetaniline, acetamide compounds of acetamide, formaldehyde, acetaldoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime and other oxime compounds, these can be used alone, Two or more types can also be used in combination.

Isocyanate compounds can be used in the form of monomers, or in the form of mixtures or combinations with various polymers. In terms of improving the dispersibility or crosslinkability of the isocyanate compound, it is preferable to use a mixture or combination with a polyester resin or a urethane resin.

(Epoxy compound) The epoxy compound used in the crosslinking agent is a compound having an epoxy group in the molecule, for example, epichlorohydrin and hydroxyl groups such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A, etc. The condensate of an amine group may, for example, be a polyepoxy compound, a diepoxide compound, a monoepoxy compound, a glycidylamine compound, and the like. As the above-mentioned polyepoxy compound, for example, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris(2-hydroxyethyl) Group) isocyanate, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether; as the diepoxide compound, for example, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether Ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl Glyceryl ether; as the monoepoxy compound, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether; as the glycidyl amine compound, for example: N, N, N',N'-tetraglycidyl metaxylylenediamine, 1,3-bis(N,N-diglycidylamino)cyclohexane, etc. From the viewpoint of improving adhesiveness, a polyether epoxy compound is preferred. In addition, the amount of epoxy groups is preferably a polyepoxy compound of trifunctional or higher polyfunctionality than bifunctional.

(Melamine compound) Among the above-mentioned melamine compound compounds used in the crosslinking agent, compounds having a melamine skeleton can be used, for example, hydroxyalkylated melamine derivatives, compounds obtained by partially or completely etherification by reacting alcohols with hydroxyalkylated melamine derivatives, and A mixture of these. As the alcohol used for etherification, methanol, ethanol, isopropanol, n-butanol, isobutanol, etc. are preferably used. In addition, as the melamine compound, it may be any one of a monomer or a dimer or higher polymer, or a mixture of these may also be used. Furthermore, a compound obtained by co-condensing a part of melamine with urea or the like can also be used. In order to increase the reactivity of the melamine compound, a catalyst can also be used in combination.

From the viewpoint of obtaining good coating film strength, the content of the crosslinking agent is preferably 10 parts by mass or more relative to 100 parts by mass of the curable monomer, more preferably 20 parts by mass or more, and more preferably 25 parts by mass or more. On the other hand, from the viewpoint of obtaining good adhesion between the films, it is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 40 parts by mass or less.

(Carbodiimide compound) The above-mentioned carbodiimide compound used in the crosslinking agent is a compound having a carbodiimide structure, and is a compound having more than one carbodiimide structure in the molecule. In order to achieve better adhesion, etc., it is more preferable to have two or more polycarbodiimide-based compounds in the molecule. The carbodiimide compound can be synthesized by a previously known technique, and the condensation reaction of a diisocyanate compound is usually used. The diisocyanate compound is not particularly limited. Both aromatic and aliphatic compounds can be used. Specifically, toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene can be mentioned. Diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, dicyclohexyl Methane diisocyanate and so on.

The content of the carbodiimide group contained in the carbodiimide compound is preferably the carbodiimide equivalent (to provide the weight of the carbodiimide compound of 1 mol of the carbodiimide group [g ]) is 100 to 1000, of which 250 or more or 800 or less is preferable, and 300 or more or 700 or less is more preferable. By using the above range, the durability of the coating film can be improved.

(Other ingredients) (Polyol compound) As the polyol compound, for example, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 2,3- Butylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, 1 ,9-nonanediol, 2,2-dimethylolheptane, 1,3-propanediol, 1,4-butanediol, dipropylene glycol, 1,3-tetramethylene glycol, 2-methyl -1,3-trimethylene glycol, 2,4-diethyl-1,5-pentamethylene glycol, hydrogenated bisphenol A, hydroxyalkylated bisphenol A, 1,4-cyclohexane Dimethanol, 1,4-cyclohexanediol, 2,2,4-trimethyl-1,3-pentanediol, N,N-bis(2-hydroxyethyl)dimethylhydantoin, etc. Low molecular weight glycols; polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, polybutadiene polyols, (meth)acrylic polyols, polyhexyl alcohols High molecular weight polyols such as lactone-based polyols, polysiloxane-based polyols, and polyurethane-based polyols.

As polyether polyols, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutylene glycol, polyhexylene glycol, and other polyether polyols containing an oxyalkylene structure , Or random or block copolymers of these polyalkylene glycols.

Among these, polyether polyols containing an oxyalkylene structure are preferred. The number of carbon atoms in the alkylene structure is preferably 2-6, particularly preferably 2-4, and more preferably 4.

As polyester-based polyols, for example, polycondensates of polyols and polycarboxylic acids; ring-opening polymers of cyclic esters (lactones); reaction of three components: polyols, polycarboxylic acids and cyclic esters Things and so on. As said polyol, the said low molecular-weight diol etc. are mentioned. As the above-mentioned polycarboxylic acid, for example, malonic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecane Aliphatic dicarboxylic acids such as acids; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid; terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, p- Aromatic dicarboxylic acids such as phthalic acid and trimellitic acid. As said cyclic ester, propiolactone, β-methyl-δ-valerolactone, ε-caprolactone, etc. may be mentioned, for example.

As the polycarbonate-based polyol, for example, a reactant of a polyol and phosgene; a transesterification reactant of a carbonate and a polyol, etc. may be mentioned. Examples of the above-mentioned polyols include the above-mentioned low-molecular-weight diols, and examples of the above-mentioned alkylene carbonates include: ethylene carbonate, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, and di-n-propyl carbonate. Isopropyl ester, dibutyl carbonate, dicyclohexyl carbonate and diphenyl carbonate, etc. In addition, the polycarbonate-based polyol may be a compound having a carbonate bond in the molecule and a hydroxyl group at the terminal, and may also have a carbonate bond and an ester bond together.

<The curable composition used to form the hardened resin layer (A), (B)> As an example of the curable composition for forming the curable resin layer (A) and (B), for example, a combination of a hydroxyl group-containing (meth)acrylate compound and an isocyanate compound, or a hydroxyl group-containing (former (Meth)acrylate urethane-based compound obtained by combining an acrylate-based compound, an isocyanate compound, and a polyol-based compound. In addition, examples include combinations of acrylic esters and crosslinkable monomers having a vinyl group, combinations of methacrylic esters and crosslinkable monomers having a vinyl group, acrylic esters and hydroxyl-containing (meth) Combinations of acrylate-based compounds, combinations of methacrylates and (meth)acrylate-based compounds containing hydroxyl groups, etc. But it is not limited to these.

In order to achieve good coating properties, the curable composition used to form the curable resin layer (A) and (B) has a viscosity of 10-60 mPa･s as measured by an E-type viscometer at 25°C. Preferably it is 30 mPa･s or less, among them, it is preferably 20 mPa･s or less, among them, it is preferably 15 mPa･s or less, and among them, it is more preferably 12 mPa･s or less.

＜Formation method of hardened resin layer (A)＞ The hardened resin layer (A) is preferably, for example, using conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die nozzle coating, bar coating, curtain coating, and inkjet. After the curable composition is applied, light irradiation, for example, ultraviolet ray irradiation, is performed to harden and form it.

＜Formation method of hardened resin layer (B)＞ The method of providing the hardened resin layer (B) is preferably, for example, reverse gravure coating, direct gravure coating, roll coating, die nozzle coating, bar coating, curtain coating, inkjet and other previously known methods. Coating method After the curable composition is applied, light irradiation, for example, ultraviolet ray irradiation, is performed to harden and form.

＜＜Physical properties of this laminated film＞＞ (Pencil hardness) In the present laminated film having the above-mentioned structure, the surface hardness of the film, specifically, the pencil hardness of the surface of the cured resin layer (B) can be set to 2H or more, especially 3H or more.

(Repetitive bendability) The laminated film with the above-mentioned structure is provided with a hardened resin layer (A) on the surface of the base film, and the elastic modulus of the hardened resin layer (A) is set to be lower than the elastic modulus of the hardened resin layer (B) , Can further improve the practical repetitive characteristics. Therefore, even if the laminated film is bent more than 200,000 times in the repeated bendability evaluation (under the condition of R=2.5), the durability without cracks can be obtained.

(Film Haze) When the laminated film is assumed to be applied to optical applications, the haze of the film is preferably 5.0% or less, among them, 4.0% or less, and particularly preferably 3.0% or less.

＜＜Characteristics and uses of this laminated film＞＞ From the examples and the test results conducted by the inventors so far, it can be seen that if the laminated film is used, the surface hardness (for example, 2H or more in pencil hardness evaluation) and repetitive bendability (under the condition of R=2.5) can be balanced at a high level. It can be bent 200,000 times). Presumably, by adjusting the thickness of the hardened resin layer (A) of the first layer and the hardened resin layer (B) of the second layer, the stress transmission to the hardened resin layer (B) applied when the laminated film is bent can be reduced. Therefore, it has the advantage that it can also use the resin component composed of acrylic monomer which is considered difficult to use in the previous method (single-layer structure coating method), which increases the degree of freedom in designing the laminated film. Furthermore, it is speculated that the double-layer structure of the hardened resin layer (A) and the hardened resin layer (B) can also be expected to disperse the stress in the thickness direction, which can contribute to further improvement of the bending durability.

In addition, it can be seen that by setting the elastic modulus of the cured resin layer (A) to be lower than the elastic modulus of the cured resin layer (B), a high level of surface hardness (for example, 2H or more in pencil hardness evaluation) and Repeated bendability (under the condition of R=2.5, it can bend 200,000 times). On the other hand, it can also be seen that it is difficult to achieve both required hard coat properties and repetitive bendability if only the two-layer structure described above (Comparative Example 3 to Comparative Example 5) is used.

In addition, it can be seen that if it has a two-layer structure including the cured resin layer (A) and the cured resin layer (B) as described above, it is not necessary to maximize the tensile modulus of the base film used. Previously, when designing the target surface hardness to the required level (for example, 2H or more) in a laminate film with a surface layer with high surface hardness, it was necessary to redesign the structure of the raw material that constitutes the base film used as needed. Research to further increase the tensile modulus of elasticity. In contrast, if the above-mentioned two-layer structure of the hardened resin layer (A) and the hardened resin layer (B) is used, it has the following advantages: it is also possible to appropriately select a general-purpose base film circulating in the market for selection. With regard to the base film, the degree of freedom is increased.

The laminated film has excellent surface hardness and practical reversible flexibility, and can also obtain transparency, so it can be used for surface protection applications, display applications, and especially front panel applications. For example, it can be suitably used as a surface protective film, especially a surface protective film for displays, and can be suitably used as a surface protective film for flexible displays among them. However, the use of the laminated film is not limited to these uses.

＜＜Explanation of words and sentences＞＞ In the present invention, when it is called a "film", it also includes a "sheet", and when it is called a "sheet", it also includes a "film".

In the present invention, when it is described as "X～Y" (X and Y are arbitrary numbers), unless otherwise specified, it also includes the meaning of "more than X and less than Y", and "preferably greater than X" "" or "preferably less than Y". In addition, when it is described as "more than X" (X is an arbitrary number), unless otherwise specified, it includes the meaning of "preferably greater than X", and is described as "below Y" (Y is an arbitrary number) In the case of ), unless otherwise specified, it also includes the meaning of "preferably less than Y". Example

Hereinafter, the present invention will be specifically described with examples. However, the present invention is not limited in any way by the following examples. The measurement method and evaluation method used in the present invention are as follows.

(1) Measuring method of film thickness of hardened resin layer Using the "Aron Alpha series" manufactured by Toagosei Co., Ltd., each laminated film was adhered to a glass slide to prepare samples for SAICS (Surface And Interfacial Cutting Analysis System). The obtained SAICS sample was set in SAICAS (DN-01 type manufactured by Daipla Wintes Co., Ltd.), and a cut with a width of 300 μm and a depth of 1 μm was cut with a diamond tip in advance. The incision is cut out using a single crystal diamond knife with a V-angle size of 80°, a bevel angle of 5°, and a relief angle of 5°. The measurement is to set a 300 μm-wide boron nitride cutter on the sample previously cut with a 300 μm wide notch, and measure the film thickness of each hardened resin layer at any depth, horizontal speed 1 μm/s, vertical speed 0.5 μm/s . The measurement uses a boron nitride knife with a knife width of 0.3 mm, a bevel angle of 20°, and a relief angle of 10°. Measure the strength of the material according to the vertical displacement position and cutting force, and confirm the thickness of each layer.

(2) Film haze (transparency) According to JIS K 7136, the haze meter HM-150 manufactured by Murakami Color Technology Research Institute was used to measure the film haze of each laminated film. (Judgment criteria) A (Excellent): Below 5% B (bad): higher than 5%

(3) Pencil hardness (hard coatability) According to JIS K 5600-5-4, the pencil hardness is evaluated by a pencil hardness tester (manufactured by Yasuda Seiki Co., Ltd.) under a load of 750 g. Based on this result, the judgment is made according to the following judgment criteria. (Judgment criteria) A (Excellent): The pencil hardness is 3H or more. B (slightly better): The pencil hardness is 2H or more and less than 3H. C (bad): The pencil hardness is less than 2H.

(4) Repetitive bending Using a bending tester (manufactured by Yuasa System Co., Ltd., DLDMLH-FS), test so that the hardened resin layer side of the laminated film becomes the outer surface, and visually confirm whether the hardened resin layer on the outer surface has cracks. Then, the minimum radius (R) that does not cause cracks and the number of repetitive bending are measured, and based on the results, the following judgment criteria are used for judgment. (Judgment criteria) A (Excellent): R=2.5 or less, and the number of repeated bending can be 200,000 times. B (slightly better): R exceeds 2.5, or the number of repeated bending is more than 10,000 times and less than 200,000 times. C (bad): R exceeds 2.5, or the number of repeated bendings is less than 10,000.

(5) Evaluation based on the specified bending direction (In/Out) Use a bending tester (manufactured by Yuasa System Machinery Co., Ltd., DLDMLH-FS) to test so that the hardened resin layer side of the laminated film becomes the inner surface (In) or the outer surface (Out), and visually confirm the inner surface (In ) Or whether the hardened resin layer on the outer surface (Out) is cracked. Then, the minimum radius (R) that does not cause cracks is measured, and based on the result, the judgment is made by the following judgment criteria. (Judgment criteria) A (Excellent): Both Out/In are R=1.5 and less than 2.0 B (slightly better): Out is R=2.0 or more and R is less than 2.5 C (bad): Out is R=2.5 or more

(6) The modulus of elasticity of the hardened resin layer (A) and the hardened resin layer (B) Using a dynamic ultra-micro hardness tester (DUH-W201, manufactured by Shimadzu Corporation), the elastic modulus (MPa) was determined in accordance with JIS Z 2255. At this time, the sample temperature was set to 25°C, the test force was set to 4 mN, the load speed was set to 0.7 mN/S, and the holding time was set to 5 seconds.

(7) Refractive index of hardened resin layer (A) and hardened resin layer (B) Determine the refractive index of each layer by Abbe measurement. Based on this result, the judgment was made based on the following judgment criteria. (Judgment criteria) A (Excellent): The difference in refractive index between the cured resin layer (A) and the cured resin layer (B) is 0.15 or less. B (bad): The difference in refractive index between the cured resin layer (A) and the cured resin layer (B) exceeds 0.15.

(8) Adhesion of the cured resin layer (A) and the cured resin layer (B) According to JIS K 5600-5-6, the adhesion between the hardened resin layer (A) and the hardened resin layer (B) was evaluated by the cross-cut method (10×10 of 100 cells). Based on this result, the judgment was made based on the following judgment criteria. (Judgment criteria) A (Excellent): Good adhesion on the whole surface (closed area: 100%) B (slightly better): partial peeling (Closed area: more than 50% and less than 100%) C (Poor): Partial peeling or peeling on the entire surface. (Closed area: less than 50%)

(9) Comprehensive evaluation Based on the following criteria, the laminated films obtained in the Examples and Comparative Examples were evaluated. (Judgment criteria) A (Excellent): Regarding transparency, hard coating, repeated bending, bending direction, the difference in refractive index between the hardened resin layer (A) and the hardened resin layer (B), the hardened resin layer (A) and the hardened resin layer ( B) All items of tightness are A. B (slightly better): Regarding transparency, hard coating properties, repetitive bendability, bending direction, the difference in refractive index between the hardened resin layer (A) and the hardened resin layer (B), the hardened resin layer (A) and the hardened resin layer (B) For each item of adhesion, at least one is B and the rest are A. C (Inferior): Regarding transparency, hard coatability, repetitive bendability, bending directionality, the difference in refractive index between the cured resin layer (A) and the cured resin layer (B), the cured resin layer (A) and the cured resin layer ( For each item of adhesion of B), at least any one of hard coatability, repetitive bending property and bending directionality is C, and the rest are A or B.

Various materials used in Examples and Comparative Examples were prepared as follows.

＜Base film F1＞ Manufactured by Mitsubishi Chemical Corporation: Polyethylene terephthalate biaxially stretched film (product name "DIAFOIL T612 type"), thickness: 50 μm, tensile modulus of elasticity (JIS K 7161) 4.3 GPa.

＜Base film F2＞ Manufactured by Teijin: Polyethylene naphthalate biaxially stretched film (grade name "Teonex W51"), thickness: 50 μm, tensile modulus (JIS K 7161) 6.4 GPa.

＜Base film F3＞ Kolon company manufacture: polyimide film (product name "C50"), thickness: 50 μm, tensile modulus (JIS K 7161) 6.9 GPa.

＜Acrylic (A)＞ Add 98 parts by mass of glycidyl methacrylate (“Acryester G” manufactured by Mitsubishi Chemical Corporation) and methyl methacrylate (“Acryester M” manufactured by Mitsubishi Chemical Corporation) to a reactor equipped with a stirrer, reflux condenser and thermometer. 1 part by mass, 1 part by mass of ethyl acrylate (manufactured by Mitsubishi Chemical Corporation), 1.9 parts by mass of mercaptopropyl trimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd. "KBM803"), 157.3 parts by mass of propylene glycol monomethyl ether (PGM), start After stirring, the system was replaced with nitrogen and the temperature was raised to 55°C. After adding 1 part by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) ("V-65" manufactured by FUJIFILM Wako Pure Chemical Industries, Inc.), the temperature in the system was raised to 65°C, After stirring for 3 hours, 0.5 part by mass of V-65 was further added, and the mixture was stirred at 65°C for 3 hours. The temperature in the system was raised to 100°C, and after stirring for 30 minutes, 0.45 parts by mass of p-methoxyphenol (manufactured by FUJIFILM Wako Pure Chemical Industries) and 138.1 parts by mass of PGM were added, and the temperature in the system was raised to 100°C again. Then, after adding 3.1 parts by mass of triphenylphosphine (manufactured by FUJIFILM Wako Pure Chemical Industries), 50.7 parts by mass of acrylic acid (manufactured by Mitsubishi Chemical Corporation) was added, the temperature was raised to 110° C., and the mixture was stirred for 6 hours to obtain a side chain having (methyl) A solution of acrylic acrylate (A). Furthermore, the composition of the reaction liquid is X/PGM=30/70 (mass ratio).

[Example 1] Using a bar coater, the curable composition a prepared in the following manner was coated on the base film F2 at 25°C so that the coating thickness (after drying) became 2.0 μm , Heated at 90 ℃ for 1 min to make it dry. Next, the curable composition b prepared in the following manner was coated by a bar coater so that the coating thickness (after drying) became 3.0 μm so as to coat the hardened resin layer (A), at 90°C After heating for 1 minute to dry, apply ^{UV radiation with a cumulative light quantity of 400 mJ/cm 2} to harden the hardened resin layers (A) and (B) to obtain a base film F2/hardened resin layer (A)/hardened resin layer ( B) Laminated film composed of laminated layers.

(Curable composition a) 5 parts by mass of a photopolymerization initiator was added to 100 parts by mass of acrylate (A) to prepare curable composition a. The mass average molecular weight of the curable composition a was 15,000, and the refractive index of the curable resin layer (A) was 1.53.

(Curable composition b) Add 67 parts by mass of silicon dioxide particles (MEK-AC-2140Y, manufactured by Nissan Chemical Co., Ltd.) to 100 parts by mass of acrylic urethane (Mitsubishi Chemical Co., Ltd., "UT-5670"). 5 parts by mass of the starting agent was used to prepare a curable composition b. The mass average molecular weight of the curable composition b was 10,500, and the refractive index of the curable resin layer (B) was 1.50.

[Example 2] Except for changing the thickness of the cured resin layer (A) and the cured resin layer (B) in Example 1, it was manufactured in the same manner as in Example 1 to obtain a laminated film.

[Example 3] In Example 1, the curable composition b was changed to the following curable composition b1, except that it was produced in the same manner as in Example 1 to obtain a laminated film.

(Curable composition b1) To 100 parts by mass of acrylate (A), 67 parts by mass of alumina particles (ALTPGDA manufactured by CIK NanoTek Co., Ltd.) and 5 parts by mass of a photopolymerization initiator were added to prepare a curable composition b1. The mass average molecular weight of the curable composition b1 was 15,000, and the refractive index of the curable resin layer (B) was 1.54.

[Example 4] In Example 1, the base film F2 was changed to the above-mentioned base film F1, except that it was manufactured in the same manner as in Example 1 to obtain a laminated film.

[Example 5] In Example 1, the base film F2 was changed to the above-mentioned base film F3, except that it was produced in the same manner as in Example 1, to obtain a laminated film.

[Comparative Example 1] In the same manner as in Example 1, the curable composition a was applied to the base film F2 at 25°C by a bar coater so that the coating thickness (after drying) became 5.0 μm After heating at 90°C for 1 min to dry it, irradiate ^{UV rays with a cumulative light quantity of 400 mJ/cm 2 to} form a cured resin layer (A) with a thickness (after drying) of 5.0 μm to obtain a laminated film. At this time, the hardened resin layer (B) was not formed.

[Comparative Example 2] In the same manner as in Example 1, the curable composition b was coated on the base film F2 by a bar coater so that the coating thickness (after drying) became 5.0 μm uniformly. After heating at 90°C for 1 minute to dry, irradiate ^{UV rays with a cumulative light quantity of 400 mJ/cm 2 to} form a cured resin layer (B) with a thickness (after drying) of 5.0 μm, and obtain a laminated film. At this time, the hardened resin layer (A) was not formed.

[Comparative Example 3] In Example 1, the curable composition a was changed to the following curable composition a1, and the curable composition b was changed to the following curable composition b2, except that the same procedure as in Example 1 was carried out. Obtain laminated film.

(Curable composition a1) 5 parts by mass of a photopolymerization initiator was added to 100 parts by mass of urethane acrylate (UV-6640B, manufactured by Mitsubishi Chemical Co., Ltd.) to prepare a curable composition a1. The mass average molecular weight of the curable composition a1 was 5,000, and the refractive index of the curable resin layer (A) was 1.51.

(Curable composition b2) 80 parts by mass of DPHA and 5 parts by mass of the photopolymerization initiator were added to 100 parts by mass of urethane acrylate (UV-1700B, manufactured by Mitsubishi Chemical Co., Ltd.) to prepare a curable composition b2. The mass average molecular weight of the curable composition b2 was 2,000, and the refractive index of the curable resin layer (B) was 1.51. DPHA: aronix M-404 (Dipentaerythritol hexaacrylate/Dipentaerythritol pentaacrylate) manufactured by Dong-A Synthetic Co., Ltd.

[Comparative Example 4] Except that the coating order of the curable composition a and the curable composition b was reversed in Example 1, the laminated film was obtained in the same manner as in Example 1.

[Comparative Example 5] In Example 1, the curable composition a was changed to the following curable composition a2, and the curable composition b was changed to the following curable composition b3, except that the same procedure as in Example 1 was carried out. Obtain laminated film.

(Curable composition a2) Add 100 parts by mass of 6 mol of EO-modified DPHA, 200 parts by mass of silica particles (MEK-AC-2140Y manufactured by Nissan Chemical Co., Ltd.), and 5 parts by mass of photopolymerization initiator to 100 parts by mass of the aforementioned DPHA, The curable composition a2 is prepared. The mass average molecular weight of the curable composition a2 was 790, and the refractive index of the curable resin layer (A) was 1.50.

(Curable composition b3) To 100 parts by mass of acrylic urethane (UV-7650B, manufactured by Mitsubishi Chemical Co., Ltd.), 100 parts by mass of pentaerythritol triacrylate and 5 parts by mass of a photopolymerization initiator were added to prepare a curable composition b3. The mass average molecular weight of the curable composition b3 was 2,300, and the refractive index of the curable resin layer (B) was 1.51.

[Comparative Example 6] In Example 1, the curable composition a was changed to the following curable composition a3, and the curable composition b was changed to the following curable composition b4, except that it was the same as in Example 1, except that Obtain laminated film.

(Curable composition a3) To 100 parts by mass of the following (meth)acrylic polymer solution, 6 parts by mass of the following polyisocyanate and 23 parts by mass of the aforementioned DPHA were added to prepare a curable composition a3. The mass average molecular weight of the curable composition a3 was 15,000, and the refractive index of the curable resin layer (A) was 1.50.

((Meth)acrylic polymer solution) Combine 283 parts by mass of methyl isobutyl ketone, 149 parts by mass of glycidyl methacrylate, 276 parts by mass of methyl methacrylate, and tertiary butyl peroxide (2-ethylhexanoic acid) (Japan Emulsifier Co., Ltd.) Co., Ltd., trade name: PERBUTYL O) 25 parts by mass were synthesized to obtain a precursor, 76 parts by mass of acrylic acid was added to the synthesis, and 1000 parts by mass of a methyl isobutyl ketone solution of (meth)acrylic polymer was obtained ( Non-volatile content 50.0% by mass). The property values of this (meth)acrylic polymer are as follows. Weight average molecular weight (Mw): 15,000, The theoretical propylene equivalent of solid content conversion: 478 g/eq, Hydroxyl value: 117 mgKOH/g.

(Polyisocyanate) Burnock DN-950 (adduct polyisocyanate) manufactured by DIC Co., Ltd.

(Curable composition b4) To 100 parts by mass of the following (meth)acrylic polymer solution, 6 parts by mass of the following polyisocyanate and 8 parts by mass of the aforementioned DPHA were added to prepare a curable composition b4. The mass average molecular weight of the curable composition b4 was 40,000, and the refractive index of the curable resin layer (B) was 1.52.

((Meth)acrylic polymer solution) Add 229 parts by mass of methyl isobutyl ketone to a reaction device equipped with a stirring device, a condenser, a dropping funnel, and a nitrogen introduction pipe. While stirring, the temperature in the system was raised to 110°C, and then the reaction time from the dropping funnel was 3 times. Hourly dropping contains 309 parts by mass of glycidyl methacrylate, 34 parts by mass of methyl methacrylate, and tertiary butyl peroxide (2-ethylhexanoic acid) (manufactured by Japan Emulsifier Co., Ltd., product name: PERBUTYL O) After 10 parts by mass of the mixed solution, keep it at 110°C for 15 hours. Then, after lowering the temperature of the above-mentioned mixed solution to 90°C, 0.1 parts by mass of p-methoxyphenol and 157 parts by mass of acrylic acid were added, and 3 parts by mass of triphenylphosphine were added. The temperature was raised to 100°C and kept for 8 hours. Dilute with methyl isobutyl ketone to obtain 1000 parts by mass of a methyl isobutyl ketone solution of (meth)acrylic polymer (A1) (non-volatile content 50.0% by mass). The property values of the (meth)acrylic polymer (A) are as follows. Weight average molecular weight (Mw): 40,000, The theoretical propylene equivalent of solid content conversion: 230 g/eq, Hydroxyl value: 244 mgKOH/g.

(Polyisocyanate) Barnock DN-980S (isocyanurate type polyisocyanate) manufactured by DIC Co., Ltd.

＜Evaluation result＞ The characteristics of each laminated film obtained in the above-mentioned Examples and Comparative Examples are shown in Table 1 and Table 2 below.

[Table 1] project unit Example 1 Example 2 Example 3 Example 4 Example 5 Hardened resin layer (B) Modulus of elasticity MPa 500 500 410 500 500 Refractive index - 1.50 1.50 1.54 1.50 1.50 Thickness (H _B ) μm 3.0 2.5 3.0 3.0 3.0 Hardened resin layer (A) Modulus of elasticity MPa 330 330 330 330 330 Refractive index - 1.53 1.53 1.53 1.53 1.53 Thickness (H _A ) μm 2.0 2.5 2.0 2.0 2.0 Base film species F2 F2 F2 F1 F3 material - PEN PEN PEN PET PI thickness μm 50 50 50 50 50 Tensile modulus of elasticity GPa 6.4 6.4 6.4 4.3 6.9 The difference in modulus of elasticity between hardened resin layer (A) and hardened resin layer (B) MPa 170 170 80 170 170 - B＞A B＞A B＞A B＞A B＞A Haze of laminated film % 1.2 1.2 1.2 0.8 0.7 Transparency assessment - A A A A A Pencil hardness (hard coating) - 3H 3H 3H 2H 4H Hard coat evaluation - A A A B A Repetitive bending R - 2.5 2.5 2.5 2.5 2.5 Repeated bending times Times 200,000 200,000 200,000 200,000 200,000 Repeated bendability evaluation - A A A A A Bending direction In R - 1.5 1.5 1.5 1.5 1.5 Bending direction Out R - 1.5 1.5 1.5 1.5 1.5 Evaluation of bending directionality - A A A A A Evaluation of the difference in refractive index between the hardened resin layer (A) and the hardened resin layer (B) - A A A A A Evaluation of the adhesion between the hardened resin layer (A) and the hardened resin layer (B) - A A A A A Comprehensive Evaluation - A A A B A

[Table 2] project unit Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative example 5 Comparative example 6 Hardened resin layer (B) Modulus of elasticity MPa - 500 430 330 250 410 Refractive index - - 1.50 1.51 1.53 1.51 1.50 Thickness (H _B ) μm - 5.0 3.0 3.0 2.0 20.0 Hardened resin layer (A) Modulus of elasticity MPa 330 - 1 500 320 190 Refractive index - 1.53 - 1.51 1.50 1.50 1.52 Thickness (H _A ) μm 5.0 - 2.0 2.0 3.0 15.00 Base film species F2 F2 F2 F2 F2 F2 material - PEN PEN PEN PEN PEN PEN thickness μm 50 50 50 50 50 50 Tensile modulus of elasticity GPa 6.4 6.4 6.4 6.4 6.4 6.4 The difference in modulus of elasticity between the hardened resin layer (A) and the hardened resin layer (B) MPa - - 429 -170 -70 220 - - - B＞A B＜A B＜A B＞A Haze of laminated film % 1.2 1.2 1.2 1.2 1.2 1.2 Transparency assessment - A A A A A A Pencil hardness (hard coating) - H 4H 3B 2H 4H H Hard coat evaluation - C A C B A C Repetitive bending R - 2.5 2.5 2.5 2.5 2.5 3.0 Repeated bending times Times 200,000 100,000 20000 200,000 40000 - Repeated bendability evaluation - A B B A B C Bending direction In R - 1.5 1.5 1.5 1.5 1.0 3.0 Bending direction Out R - 1.5 2.0 1.5 1.5 2.5 3.0 Evaluation of bending directionality - A B A A C C Evaluation of the difference in refractive index between the hardened resin layer (A) and the hardened resin layer (B) - - - A A A - Evaluation of the adhesion between the hardened resin layer (A) and the hardened resin layer (B) - - - A C A - Comprehensive Evaluation - C C C C C C

＜Discussion＞ From the above-mentioned examples and the results of experiments conducted by the inventors so far, it can be seen that it has the following characteristics: a structure in which a hardened resin layer (A) and a hardened resin layer (B) are sequentially laminated on the surface of the base film. Elastic modulus, hardened resin layer (B)> hardened resin layer (A), and the difference between the elastic modulus of hardened resin layer (A) and hardened resin layer (B) ((B)－(A) ) Is greater than 0 (MPa) and less than 220 (MPa), so that the surface hardness (for example, 2H or more in pencil hardness evaluation) and repetitive bendability (under the condition of R=2.5, 200,000 times of bending can be achieved at a high level) ). In contrast to this, it has also been found that if only the two-layer structure is used as in Comparative Example 3 to Comparative Example 6, it is difficult to achieve both required hard coatability and repetitive bendability. It is estimated that the main reason for this difference is that the difference ((B)－(A)) between the elastic modulus of the hardened resin layer (A) and the elastic modulus of the hardened resin layer (B) is greater than 0 (MPa) And 220 (MPa), can reduce the stress transmission into the hardened resin layer (B) when the laminated film is bent. In addition, the stress in the thickness direction is dispersed, which helps to improve the bending durability.

At this time, it can be confirmed that as long as the elastic modulus of each of the cured resin layers (A) and (B) is adjusted by adjusting the thickness and composition of each of the cured resin layers (A) and (B), for example, the particle content can. Therefore, it has the advantage that it is also possible to use the resin component composed of acrylic monomer which is considered difficult to use in the previous method (the whole surface coating method of single-layer structure), and the degree of freedom in designing the laminated film is increased.

Furthermore, it is also known that if the difference ((B)-(A)) between the elastic modulus of the hardened resin layer (A) and the elastic modulus of the hardened resin layer (B) is greater than 0 (MPa) and less than 220 ( MPa), there is no need to maximize the tensile modulus of the substrate film used. Previously, when designing the target surface hardness to the required level (for example, 2H or more) in a laminate film with a surface layer with high surface hardness, it was necessary to redesign the structure of the raw material that constitutes the base film used as needed. Research to further increase the tensile modulus of elasticity. On the other hand, if the two-layer structure of the above-mentioned hardened resin layer (A) and hardened resin layer (B) is adopted, it has the following advantages: it is also possible to appropriately select a general-purpose base film circulating in the market to select a base material With regard to the membrane, the degree of freedom increases.

In the above examples, the case where the elastic modulus of the hardened resin layer (A) measured by a microhardness tester (JIS Z 2255) is 330 MPa was studied. For example, from a viewpoint other than an extremely soft layer such as an adhesive layer, it is estimated that if the elastic modulus of the cured resin layer (A) is 10 MPa or more, the same effect can be obtained. [Industrial availability]

The laminated film of the present invention has a high level of hard coatability (for example, 2H or more in pencil hardness evaluation) and good repetitive bending properties (200,000 times of bending under the condition of R=2.5), and can be used for various surface protection. . Among them, it can be suitably used for optical applications such as display members (surface protective films, etc.) that require flexibility.

Claims (16)

A laminated film characterized by having a structure in which a hardened resin layer (A) and a hardened resin layer (B) are sequentially laminated on the surface of a base film, Regarding the elastic modulus measured by a microhardness tester (JIS Z 2255), the elastic modulus of the hardened resin layer (B) is greater than the elastic modulus of the hardened resin layer (A), and the hardened resin layer (A) The difference between the elastic modulus and the elastic modulus of the hardened resin layer (B) is greater than 0 (MPa) and less than 220 (MPa). Such as the laminated film of claim 1, wherein the elastic modulus of the hardened resin layer (A) is 10 (MPa) or more. Such as the laminated film of claim 1 or 2, wherein the pencil hardness of the surface of the hardened resin layer (B) is 2H or more. Such as the laminated film of any one of claims 1 to 3, which can be bent more than 200,000 times in the repeated bending evaluation (under the condition of R=2.5). For the laminated film of any one of claims 1 to 4, the film haze is 5.0% or less. The laminated film according to any one of claims 1 to 5, wherein the tensile elastic modulus (JIS K 7161) of the base film is 2.0 GPa or more. The laminated film according to any one of claims 1 to 6, wherein the base film is a polyester film. The laminated film according to any one of claims 1 to 7, wherein the base film is a polyethylene naphthalate (PEN) film. The laminated film according to any one of claims 1 to 7, wherein the base film is a polyethylene terephthalate (PET) film. The laminated film according to any one of claims 1 to 7, wherein the base film is a polyimide (PI) film. The laminated film according to any one of claims 1 to 10, wherein the difference in refractive index between the hardened resin layer (A) and the hardened resin layer (B) is 0.15 or less. The laminated film according to any one of claims 1 to 11, wherein the total thickness of the cured resin layer (A) and the cured resin layer (B) is 6.0 μm or less. The laminated film of any one of claims 1 to 12, which is used for surface protection. Such as the laminated film of any one of claims 1 to 12, which is used in a display. Such as the laminated film of any one of claims 1 to 12, which is used for the front panel. A method of manufacturing a laminated film, characterized in that it is a method of manufacturing a laminated film as claimed in any one of claims 1 to 12, and The curable resin layer (A) is formed by applying a curable composition on a base film and curing it, and the mass average molecular weight of the curable composition is in the range of 1,000 to 500,000.