WO2020235164A1 - 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 microhardness 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 having excellent surface hardness and repeated bending characteristics.

In recent years, flexible substrates and flexible printed circuits have tended to be used as electronic devices become smaller and lighter. In addition, along with this trend, the demand for flexibility tends to increase also in display applications. The surface protective film for display screens used for such applications requires not only surface protective properties such as high hardness, scratch prevention, stain resistance, and abrasion resistance, but also high durability in terms of bendability. It was said that further performance improvement was requested.

Therefore, in recent years, many proposals have been made for surface protective films in order to improve flexibility or flexibility while maintaining high hardness and scratch resistance.
For example, in Patent Document 1, in a hard coat layer having a laminated structure, the intermediate layer has a larger elastic modulus than the surface layer to improve the surface hardness and damage to the hard coat film due to stress concentration. The technical contents regarding the hard coat film which prevents the stress and is hard to be scratched are disclosed.

Patent Document 2 discloses a hard coat layer having a laminated structure in which a radical material is used for the surface layer and a cationic material is used for the intermediate layer, and the interlayer adhesion is good.

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

According to Patent Document 4, in the hard coat layer having a laminated structure, the surface layer has a larger elastic modulus than the intermediate layer, and the abrasion resistance and flexibility are excellent by setting the elongation rate of the cured coating film within a specific range. The technical contents related to the hard coat film are disclosed.

Japanese Patent No. 45747666 Japanese Patent No. 4160217 Japanese Patent No. 5320848 Japanese Patent No. 4569807

As mentioned above, in recent years, the development of flexible mobile terminals capable of folding or folding an image display screen (display) has been promoted, and the surface protective film used for this type of image display screen also has an excellent surface. Along with hardness, durability that can be repeatedly bent practically, specifically, for example, 200,000 times or more is required.
However, all of the inventions described in Patent Documents 1 to 4 are not intended for repeated bending, and may be difficult to deal with.

Therefore, the present invention proposes a new laminated film that not only has excellent surface hardness but also has excellent practical repeated bending characteristics.

The present invention has a configuration in which a cured resin layer (A) and a cured resin layer (B) are sequentially laminated on the surface of a base film.
Regarding the elastic modulus measured by the micro-hardness meter measurement (JIS Z 2255), the elastic modulus of the cured resin layer (B) is larger than the elastic modulus of the cured resin layer (A), and the cured resin layer (A) We propose a laminated film characterized in that the difference between the elastic modulus of the above and the elastic modulus of the cured resin layer (B) is larger than 0 (MPa) and smaller than 220 (MPa).

The present invention is characterized in that, as an example of the method for producing a laminated film, the cured resin layer (A) is formed by applying a curable composition onto a base film and curing the curable composition. , A method for producing a laminated film, characterized in that the mass average molecular weight is in the range of 1,000 to 500,000.

The laminated film proposed by the present invention has a structure in which a cured resin layer (A) and a cured resin layer (B) are sequentially laminated on the surface of a base film, and the elastic modulus and curing of the cured resin layer (A) are provided. The difference in elastic modulus of the resin layer (B) ((B)-(A)) is larger than 0 (MPa) and smaller than 220 (MPa). Therefore, it is possible to improve the practical repetitive bending characteristics while maintaining the surface hardness, and specifically, it is possible to obtain excellent repetitive bending characteristics that do not cause any problem even if the surface is repeatedly bent 200,000 times or more.

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

<< This laminated film >>
The laminated film (referred to as "the present laminated film") according to an example of the embodiment of the present invention has a cured resin layer (A) and a cured resin layer (A) on at least one side surface of the base film (referred to as the "main base film"). It is a laminated film having a structure in which a resin layer (B) is sequentially laminated.
The laminated film may have other layers as long as it has the above structure.

<This base film>
The material and composition of the base film are not limited as long as the film can obtain the necessary and sufficient rigidity and repeatability.

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

Regardless of whether the base film has a single-layer structure or a multi-layer structure, the main component resin of each layer is preferably polyester or polyimide (PI). Such a film is referred to as a "polyester film" or a "polyimide film".
At this time, the "main component resin" means the resin having the highest content ratio among the resins constituting the present base film, for example, 50% by mass or more, particularly 70% by mass of the resins constituting the present base film. % Or more, especially 80% by mass or more (including 100% by mass).
In addition, each layer constituting this base film may contain other resin other than polyester or polyimide, or component other than resin, as long as the main component resin is polyester or polyimide.

(polyester)
The polyester (referred to as “the present polyester”) as the main component resin of each layer constituting the present base film may be a homopolyester or a copolymerized polyester.

When the present polyester is made of a homopolyester, it is preferably obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol.
Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid.
Examples of the aliphatic glycol include ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol and the like.

On the other hand, when the present polyester is a copolymerized polyester, examples of the dicarboxylic acid component include one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, sebacic acid and the like. be able to. On the other hand, examples of the glycol component include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like.

Specific examples of typical polyesters include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polybutylene terephthalate (PBN), polyethylene furanoate (PEF), and the like. Can be done. Of these, PET and PEN are preferable in terms of handleability.
When the main component resin of each layer constituting the base film is, for example, polyethylene terephthalate, the film is referred to as "polyethylene terephthalate film". The same applies when the other resin is the main component resin.

(Polyimide)
As the base film, a polyimide film is also suitable in addition to the polyester film. Regarding the imidization of the polyimide, for example, a method of imidizing after polyamic acid polymerization of diamine and dianehydride, particularly aromatic dianhydride and aromatic diamine at a 1: 1 equivalent ratio is exemplified.
Examples of the aromatic dianhydride include 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropanedianhydride (6FDA), 4- (2,5-dioxotetraki-yl) -1, 2,3,4-Tetrahydronaphthalene-1,2-dicarboxylic dianhydride (TDA), pyromellitic dianhydride (1,2,4,5-benzenetetracarboxylic dianhydride, PMDA), benzophenonetetra Examples thereof include carboxylic acid dianhydride (BTDA), biphenyltetracarboxylic dianhydride (BPDA), and biscarboxyphenyldimethylsilane dianhydride (SiDA). These may be used alone or in combination of two or more.
Examples of the aromatic diamine include oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p-methylenedianiline (pMDA), m-methylenedianiline (mMADA), Examples thereof include bistrifluoromethylbenzidine (TFDB), cyclohexanediamine (13CHD, 14CHD), and bisaminohydroxyphenylhexafluoropropane (DBOH). These may be used alone or in combination of two or more.

(Other resin components)
Each layer constituting the base film may contain a resin other than polyester and polyimide as a main component resin. In that case, the main component resins include, for example, epoxy, polyarylate, polyethersulphon, polycarbonate, polyetherketone, polysulphon, polyphenylene sulfide, polyester-based liquid crystal polymer, triacetyl cellulose, cellulose derivative, polypropylene, polyamides, and poly. Cycloolefins and the like can be exemplified.

(particle)
The base film may contain particles for the purpose of imparting slipperiness to the film surface and for the main purpose of preventing scratches in each step.
The type of the particles is not particularly limited as long as the particles can be easily slippery. For example, inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, titanium oxide, acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, benzoguanamine. Examples include organic particles such as resin. These may be used alone or in combination of two or more of them.
Further, during the polyester manufacturing process, precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed can also be used.

The shape of the particles is not particularly limited. For example, it may be spherical, lumpy, rod-shaped, flat-shaped, or the like.
Further, the hardness, specific gravity, color and the like of the particles are not particularly limited. Two or more kinds of these series of particles may be used in combination, if necessary.

The average particle size of the 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. If it exceeds 5 μm, the surface roughness of the base film may become too rough, and a problem may occur when a cured resin layer made of various cured compositions is formed in a subsequent step.

The particle content is preferably 5% by mass or less of the present base film, particularly 0.0003% by mass or more or 3% by mass or less, and among them, 0.01% by mass or more or 2% by mass or less. More preferred.
If the average particle size of the particles is within the above range, the surface roughness of the base film is not too coarse, so that a problem occurs when a cured resin layer made of various cured compositions is formed in a subsequent step. Can be suppressed.

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 a raw material resin such as polyester. In the case of polyester, it is preferable to add it after the esterification or transesterification reaction is completed.

(Other ingredients)
If necessary, the base film may contain, for example, conventionally known antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, ultraviolet absorbers, and the like as other components. ..

(Thickness)
The thickness of the base film is preferably, for example, 9 μm to 125 μm, more preferably 12 μm or more or 100 μm or less, and among them, 20 μm or more or 75 μm or less, from the viewpoint that necessary and sufficient rigidity and repeatability can be obtained. Is more preferable.

(Manufacturing method)
The base film can be formed, for example, by forming a resin composition into a film shape by a melt film forming method or a solution film forming method. In the case of a multi-layer structure, co-extrusion may be performed.
Further, it may be uniaxially stretched or biaxially stretched, and a biaxially stretched film is preferable from the viewpoint of rigidity.

(Characteristics of this base film)
The tensile elastic modulus (JIS K 7161) of the base film is preferably 2.0 GPa or more, particularly 9.0 GPa or less, and 3 among them, from the viewpoint of obtaining necessary and sufficient rigidity and repetitive bendability. More preferably, it is 0.0 GPa or more or 8.0 GPa or less, and more preferably 3.0 GPa or more or 7.0 GPa or less.

<Curing resin layers (A) (B)>
The laminated film has a laminated structure in which a cured resin layer (A) is provided on at least one side surface of the base film, and a cured resin layer (B) is further provided on the surface side thereof.
The crosslinked resin layer means a layer having a crosslinked resin structure. Whether or not it has a crosslinked resin structure can be determined by analyzing the crystal structure using an apparatus such as TOFSIMS or IR to determine the presence or absence of the crosslinked resin structure. However, the method is not limited to this method.

(Elastic modulus of each layer)
Each of these cured resin layers (A) and (B) is a layer containing a cured resin, in other words, a resin having a crosslinked structure, and the elasticity of the cured resin layer (A) is higher than the elastic modulus of the cured resin layer (B). It is preferable that the rate is lower.
Further, regarding the elastic modulus measured by the micro-hardness meter measurement (JIS Z 2255), the difference between the elastic modulus of the cured resin layer (A) and the elastic modulus of the cured resin layer (B) (elastic modulus of the cured resin layer (B)). -The elastic modulus of the cured resin layer (A) is preferably larger than 0 (MPa) and smaller than 220 (MPa).
When only the cured resin layer (B) is present on at least one side surface of the base film, it cannot withstand deformation when an external force is applied to the laminated film, and the surface of the laminated film is damaged or irreversible. Craze occurs. On the other hand, the elastic modulus of the cured resin layer (A) is lower than that of the cured resin layer (B), and the difference between the elastic modulus of the cured resin layer (A) and the elastic modulus of the cured resin layer (B). Is larger than 0 (MPa) and smaller than 220 (MPa), so that stress concentration can be avoided, and further, external force can be absorbed by the deformation of the cured resin layer (A). Therefore, it is possible to obtain a laminated film having excellent repetitive bending characteristics.

Above all, the difference in elastic modulus between the cured resin layer (A) and the cured resin layer (B) is more preferably 50 MPa or more, particularly 100 MPa or more, and particularly 150 MPa or more from the viewpoint of bendability. Is even more preferable. On the other hand, from the viewpoint of surface hardness, the difference is preferably 210 MPa or less, more preferably 200 MPa or less, and more preferably 190 MPa or less.

Further, regarding the elasticity measured by the micro-hardness meter measurement (JIS Z 2255), it is preferable that the cured resin layer (B)> the cured resin layer (A) ≥ 10 MPa.
When only the cured resin layer (B) is present on at least one side surface of the base film, it cannot withstand deformation when an external force is applied to the laminated film, and the surface of the laminated film is damaged or irreversible. Craze occurs. On the other hand, in this laminated film, the cured resin layer (A) satisfying the condition of the cured resin layer (B)> the cured resin layer (A) ≥ 10 MPa exists as the lower layer of the cured resin layer (B), so that the stress It is possible to avoid concentration. Further, the cured resin layer (A) can be deformed to absorb an external force. Therefore, it is possible to obtain a laminated film having excellent repetitive bending characteristics.

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

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

(How to adjust the elastic modulus of each layer)
The elastic properties of the cured resin layer (A) and the cured resin layer (B) are the thickness of each layer, the particle content, the selection of the curable monomer, the composition ratio of the curable monomer, and the crosslinkable monomer. It can be adjusted by changing the content ratio, the cross-linking density (molecular weight between the cross-linking points), the molecular weight of the base polymer forming each layer, the molecular weight of the cured resin composition forming each layer, and the like. However, the method is not limited to these methods.
In the present invention, the "base polymer" refers to a resin having the highest mass ratio among the resins constituting each layer.

(Thickness of each layer)
By changing the thickness of each of the cured resin layers (A) and (B), not only the elastic modulus of the cured resin layers (A) and (B) can be adjusted, but also the surface hardness can be improved. For example, the surface hardness can be improved by increasing the thickness of the cured resin layer (B) rather than the thickness of the cured resin layer (A).
The thickness of the cured resin layer (A) is preferably 10 to 300% of the thickness of the cured resin layer (B), particularly 20% or more or 200% or less, and among them, 30% or more or 100% or less. It is more preferable to have it.

After 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 with ultraviolet rays, insufficient curing due to oxygen inhibition or the like can be prevented. On the other hand, if it is 30.0 μm or less, it becomes easy to secure the surface smoothness of the laminated film, and it becomes easy to secure the transparency. From this point of view, the layer thickness is preferably 1.0 μm or more and 30.0 μm or less, and more preferably 20.0 μm or less, particularly 10.0 μm or less, and particularly 5.0 μm or less.
On the other hand, the layer thickness of the cured resin layer (B) is preferably 1.0 μm or more and 30.0 μm or less, more preferably 20.0 μm or less, of which 10.0 μm or less, and particularly 5 μm or less. Is even more preferable.

The total thickness of the cured resin layer (A) and the cured resin layer (B) is 20.0 μm or less, preferably 10.0 μm or less, more preferably 8.0 μm or less, and particularly 6 among them, from the viewpoint of bendability. It is preferably 0.0 μm or less, and 5.0 μm or less.

(Particle content of each layer)
Further, while the cured resin layer (A) does not contain particles, the cured resin layer (B) may contain particles, or the particle content of the cured resin layer (A) may be adjusted to the cured resin layer (B). It can be adjusted so that the elastic modulus of the cured resin layer (B) is higher than that of the cured resin layer (A).
As a specific example of the latter, the particle content of the cured resin layer (A) is 1% by mass to 20% by mass, while the particle content of the cured resin layer (B) is 20% by mass to 60% by mass. The elastic modulus of can be adjusted.
At this time, the particle content of the cured resin layer (A) is more preferably 1% by mass or more, particularly 2% by mass or more, and more preferably 5% by mass or more, while 20% by mass or less, particularly 15% by mass or less. Among them, it is more preferably 10% by mass or less.
On the other hand, the particle content of the cured resin layer (B) is more preferably 20% by mass or more, particularly 25% by mass or more, and more preferably 30% by mass or more, while 60% by mass or less, particularly 55% by mass or less. Above all, it is more preferably 50% by mass or less. The types of particles contained in the cured resin layer (A) and the cured resin layer (B) will be described later.

(Surface condition of each layer)
The surface of the cured resin layer (A) may be uneven or flat. Above all, it is preferable that it is flat from the viewpoint of appearance (surface gloss).
On the other hand, the surface of the cured resin layer (B) may also be uneven or flat. Above all, it is preferable that it is flat from the viewpoint of appearance (surface gloss).

(Optical characteristics of each layer)
Both the cured resin layers (A) and (B) are preferably transparent in consideration of optical applications.

Above all, 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.
When the difference in refractive index between the cured resin layer (A) and the cured resin layer (B) is 0.15 or less, the visibility can be improved. Specifically, when viewed from an angle of 45 degrees with respect to the film surface, the contour derived from the cured resin layer (A) becomes difficult to see.
From this point of view, 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 more preferably 0.05 or less. .. The lower limit of the refractive index difference is 0.

<< Manufacturing method of this laminated film >>
Both the cured resin layer (A) and the cured resin layer (B) can be formed by curing a curable composition, that is, a composition having a ability to be cured.
More specifically, a curable composition is applied and cured on at least one side surface of the base film to form a cured resin layer (A), and then the curable composition is applied and cured on the curable resin layer (A). This laminated film can be manufactured by forming the cured resin layer (B). At this time, the cured resin layer (A) and the cured resin layer (B) may be cured at the same time.
Further, after forming the cured resin layer (A), the film is once wound into a roll, the film is unwound again, and the curable composition is applied onto the cured resin layer (A) and cured. The cured resin layer (B) may be formed by forming the cured resin layer (B), or after the cured resin layer (A) is formed on the surface of the base film, the curable composition is continuously applied and cured to form the cured resin layer. (B) may be formed. The method for producing the present laminated film is not limited to such a method.

<Curable composition>
The curable composition for forming the curable resin layer (A) and the curable resin layer (B) includes a curable monomer, a photopolymerization initiator, a solvent, particles, a cross-linking agent, and the like, if necessary. It is preferable to contain the components of. Each will be described below.

The cured resin layer (B) is formed by setting the mass average molecular weight of the base polymer forming the cured resin layer (A), that is, the curable monomer to the mass average molecular weight of the curable resin composition forming the cured resin layer (A). By making the mass average molecular weight of the base polymer, that is, the curable monomer, or the mass average molecular weight of the curable resin composition forming the cured resin layer (B) larger than that of the cured resin layer (A), the cured resin layer It can be adjusted so that the elastic coefficient of (B) becomes high.
Above all, while reducing 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 30 μm or less, particularly 20 μm or less, and among them, 10 μm or less. From the viewpoint of maintaining hardness and enhancing repeated bending characteristics, the mass average molecular weight of the base polymer forming the cured resin layer (A) or the mass average of the curable resin composition forming the cured resin layer (A). The molecular weight is increased by an order of magnitude or more, that is, 10 times or more, from the mass average molecular weight of the base polymer forming the cured resin layer (B) to the mass average molecular weight of the curable resin composition forming the cured resin layer (B). Therefore, the elastic ratio of the cured resin layer (B) can be adjusted to be higher than that of the cured resin layer (A).

From this point of view, the mass average molecular weight of the base polymer forming the cured resin layer (A), that is, the curable monomer, or the mass average molecular weight of the curable resin composition forming the cured resin layer (A) is 1,000 or more. It is preferably 3,000 or more, and more preferably 5,000 or more. On the other hand, it is preferably 500,000 or less, more preferably 400,000 or less, and more preferably 250,000 or less.
On the other hand, the mass average molecular weight of the base polymer forming the cured resin layer (B), that is, the curable monomer, or the mass average molecular weight of the curable resin composition forming the cured resin layer (B) is preferably 100 or more. Above all, it is more preferably 200 or more, and among them, 400 or more. On the other hand, it is preferably 500,000 or less, more preferably 400,000 or less, and more preferably 250,000 or less.

(Curable monomer)
The curable monomer may be any compound that can be cured. Among them, those containing at least one selected from the group consisting of crosslinkable monomers, acrylic acid esters, and methacrylic acid esters are preferable from the viewpoint of achieving both excellent surface hardness and repetitive bendability.
Among them, is it a comixture consisting of at least two kinds selected from crosslinkable monomers and (meth) acrylic acid esters from the viewpoint of handleability, industrial availability, and cost? Alternatively, it is preferably a mixture consisting of at least two types selected from methacrylic acid esters and vinyl-based 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. , 80/20 to 40/60, and more preferably 70/30 to 40/60.

In the present invention, when the expression "(meth) acrylic" is used, it means one or both of "acrylic" and "methacrylic". The same applies to "(meth) acrylate" and "(meth) acryloyl". Further, "(poly) propylene glycol" shall mean one or both of "propylene glycol" and "polypropylene glycol". “(Poly) ethylene glycol” has the same meaning.

From these mixtures, it is preferable to select each main component so that each of the cured resin layer (A) and the cured resin layer (B) can satisfy at least the elastic modulus and the refractive index described above.
Above all, the curable monomer used in the curable composition for forming the cured 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 cured resin layer (B) is preferably selected so as to satisfy the above-mentioned elastic modulus and refractive index.

(Crosslinkable monomer)
The crosslinkable monomer refers to a monomer having one or more polymerizable functional groups in one molecule.
Examples of the crosslinkable monomer include allyl acrylate, allyl methacrylate, 1-acryroxy-3-butane, 1-methacryloxy-3-butane, 1,2-diacryloxy-ethane, 1,2-dimethacryloxy-ethane, and the like. 1,2-Diacryloxy-propane, 1,3-diacryloxy-propane, 1,4-diacryloxy-butane, 1,3-dimethacryloxy-propane, 1,2-dimethacryloxy-propane, 1,4-dimethacryloxy-butane, triethylene Glycoldimethacrylate, polyethylene glycol diacrylate, 1,6-hexanediol dimethacrylate, 1.9-nonanediol dimethacrylate, triethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1.9-nonanediol diacrylate , 1,4-Pentadiene, trimethylolpropane triacrylate and the like.

Examples of the hydroxyl group-containing (meth) acrylate compound include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6. -Hydroxyalkyl (meth) acrylates such as hydroxyhexyl (meth) acrylates, 2-hydroxyethylacryloyl phosphate, 2- (meth) acryloyloxyethyl-2-hydroxypropylphthalates, caprolactone-modified 2-hydroxyethyl (meth) acrylates, Dipropylene glycol (meth) acrylate, fatty acid-modified-glycidyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, 2-hydroxy-3- (meth) acryloyloxypropyl (meth) acrylate , Etc. (meth) acrylate-based compound containing one ethylenically unsaturated group; containing two ethylenically unsaturated groups such as glycerindi (meth) acrylate and 2-hydroxy-3-acryloyl-oxypropyl methacrylate. (Meta) acrylate compounds; pentaerythritol tri (meth) acrylate, caprolactone-modified pentaerythritol tri (meth) acrylate, ethylene oxide-modified pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, caprolactone-modified dipentaerythritol Examples thereof include (meth) acrylate-based compounds containing three or more ethylenically unsaturated groups such as penta (meth) acrylate and ethylene oxide-modified dipentaerythritol penta (meth) acrylate.

Examples of the crosslinkable monomer having a vinyl group include glycidyl (meth) acrylate, β-methylglucidyl (meth) acrylate, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, and p-vinylbenzyl glycidyl ether. Examples thereof include α-methyl-o-vinylbenzyl glycidyl ether, α-methyl-m-vinylbenzyl glycidyl ether, and α-methyl-p-vinylbenzyl glycidyl ether, among which o-vinylbenzyl glycidyl ether and m. -Vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, 3,4-epoxycyclohexylmethyl (meth) acrylate are exemplified. These may be used alone or in combination of two or more.

(Acrylic esters)
Examples of the acrylic acid esters include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, and acrylic. Acrylic acid acyclic alkyl esters such as amyl acid, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate; cyclic alkyl acrylates such as cyclohexyl acrylate and isobornyl acrylate; Acrylic acid aryl esters such as phenyl acrylate and naphthyl acrylate; functional group-containing acrylic acid acyclic alkyl esters such as 2-hydroxyethyl acrylate, 2-methoxyethyl acrylate, and glycidyl acrylate can be exemplified.

(Methacrylic acid esters)
Examples of the methacrylic acid esters include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate and methacrylic acid. Amilic methacrylic acid such as amyl acid, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, pentadecyl methacrylate, dodecyl methacrylate; cyclic alkyl methacrylate such as cyclohexyl methacrylate and isobornyl methacrylate; Arylmethacrylic acid esters such as phenyl methacrylate; functional group-containing acyclic alkyl esters of methacrylic acid such as 2-hydroxyethyl methacrylate, 2-methoxyethyl methacrylate, and glycidyl methacrylate can be exemplified. These may be used alone or in combination of two or more.

(Photopolymerization initiator)
When the curable composition is photocured, it is preferable to add a photopolymerization initiator.

The photopolymerization initiator is not particularly limited, and examples thereof include a ketone-based photopolymerization initiator and an amine-based photopolymerization initiator. Specifically, for example, benzophenone, Michler's ketone, 4,4'-bis (diethylamino) benzophenone, xanthone, thioxanthone, isopropylxanthone, 2,4-diethylthioxanthone, 2-ethylanthraquinone, acetophenone, 2-hydroxy-2-methylpro. Piophenone, 2-Hydroxy-2-methyl-4'-isopropylpropiophenone, 1-hydroxycyclohexylphenylketone, isopropylbenzoin ether, isobutylbenzoin ether, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2- Phenylacetophenone, camphorquinone, benzanthron, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -Butanone-1, 4-dimethylaminobenzoate ethyl, 4-dimethylaminobenzoate isoamyl, 4,4'-di (t-butylperoxycarbonyl) benzophenone, 3,4,4'-tri (t-butylperoxycarbonyl) ) Benzophenone, 3,3', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, 3,3', 4,4'-tetra (t-hexylperoxycarbonyl) benzophenone, 3,3'-di ( Methoxycarbonyl) -4,4'-di (t-butylperoxycarbonyl) benzophenone, 3,4'-di (methoxycarbonyl) -4,3'-di (t-butylperoxycarbonyl) benzophenone, 4,4'- Di (methoxycarbonyl) -3,3'-di (t-butylperoxycarbonyl) benzophenone, 1,2-octanedione, 1- [4- (phenylthio) phenyl]-, 2- (o-benzoyloxime), 2 -(4'-methoxystyryl) -4,6-bis (trichloromethyl) -s-triazine, 2- (3', 4'-dimethoxystyryl) -4,6-bis (trichloromethyl) -s-triazine, 2- (2', 4'-dimethoxystyryl) -4,6-bis (trichloromethyl) -s-triazine, 2- (2'-methoxystyryl) -4,6-bis (trichloromethyl) -s-triazine , 2- (4'-Pentyloxystyryl) -4,6-bis (trichloromethyl) -s-triazine, 4- [pn, N-di (ethoxycarbonylmethyl)]-2,6-di (trichloromethyl) Methyl) -s-triazine, 1 , 3-bis (trichloromethyl) -5- (2'-chlorophenyl) -s-triazine, 1,3-bis (trichloromethyl) -5- (4'-methoxyphenyl) -s-triazine, 2- (p -Dimethylaminostyryl) benzoxazole, 2- (p-dimethylaminostyryl) benzthiazole, 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'-tetrakis (4-ethoxycarbonylphenyl)- 1,2'-bimidazole, 2,2'-bis (2,4-dichlorophenyl) -4,4', 5,5'-tetraphenyl-1,2'-bimidazole, 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-dimethylaminopropionyl) carbazole, 3,6-bis (2-methyl-2-morpholinopropionyl) -9- n-dodecylcarbazole, 1-hydroxycyclohexylphenylketone, bis (η5-2,4-cyclopentadiene-1-yl) -bis (2,6-difluoro-3- (1H-pyrrole-1-yl) -phenyl) Examples thereof include titanium, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide. Only one kind of these photopolymerization initiators may be used, or two or more kinds thereof may be used.

Further, a sensitizer may be used in combination with the photocuring initiator, if necessary. Specific examples of the sensitizer include aliphatic amines such as n-butylamine, triethylamine, and ethyl p-dimethylaminobenzoate, and aromatic amines.

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, the range is 1 to 5 parts by mass.
When the content of the photopolymerization initiator is 1 part by mass or more, the desired polymerization initiation effect can be obtained, and when the content of the photopolymerization initiator is 10 parts by mass or less, the resin layer turns yellow. Can be suppressed. The photocurable initiator and sensitizer are preferably used in a proportion of 20% by mass or less based on the solid content of the photocurable composition.

(solvent)
Examples of the solvent include ketone solvents such as methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, diacetone alcohol and acetone; alcohol solvents such as pentanol, hexanol, heptanol and octanol; ethylene glycol monoethyl. Ether solvents such as ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate; methyl acetate, ethyl acetate, butyl acetate, methoxybutyl acetate, amyl acetate, propyl acetate, ethyl lactate, methyl lactate, Ester-based solvents such as butyl lactate; organic solvents such as hydrocarbon solvents such as toluene, xylene, solventnaphtha, hexane, cyclohexane, ethylcyclohexane, methylcyclohexane, heptane, octane, and decane can be exemplified. These organic solvents may be used alone or in combination of two or more.

(particle)
The curable composition can contain a predetermined amount of particles in order to improve slipperiness and blocking, and further to adjust the elastic modulus of each layer.
Examples of the particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, titanium oxide, acrylic resin, styrene resin, urea resin, and phenol resin. Organic particles such as epoxy resin and benzoguanamine resin can be mentioned. These may be used alone or in combination of two or more of them.
Further, during the polyester manufacturing process, precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed can also be used.

The shape of the particles is not particularly limited. For example, it may be spherical, lumpy, rod-shaped, flat-shaped, or the like.
Further, the hardness, specific gravity, color and the like of the particles are not particularly limited. Two or more kinds of these series of particles may be used in combination, if necessary.

If the average particle size of the particles is too large, the surface roughness becomes too coarse, which may cause problems when forming a cured resin layer made of various cured compositions in a subsequent step, but it is too small. In order to reduce the effect of adding particles, the thickness 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.

(Crosslinking agent)
From the viewpoint of improving chemical resistance or elastic modulus, it is preferable to add a cross-linking agent. The cross-linking agent referred to here means a cross-linking agent other than the above-mentioned cross-linking monomer.
Examples of the cross-linking agent include oxazoline compounds, isocyanate compounds, epoxy compounds, melamine compounds, and carbodiimide compounds. Above all, from the viewpoint of improving adhesion, it is more preferable to use at least one of an oxazoline compound or an isocyanate compound.

(Oxazoline compound)
The above-mentioned oxazoline compound used as a cross-linking agent is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferable, and it is prepared by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with another monomer. be able to.
Examples of the addition polymerizable oxazoline group-containing monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, and 2-isopropenyl-2-. Examples thereof include oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and one or a mixture of two or more thereof can be used. .. Among them, 2-isopropenyl-2-oxazoline is suitable because it is easily available industrially.
The other monomer is not limited as long as it is a monomer copolymerizable with an addition-polymerizable oxazoline group-containing monomer, and is, for example, an alkyl (meth) acrylate (the alkyl group is a methyl group, an ethyl group, an n-propyl group, or an isopropyl). (Meta) acrylic acid esters such as group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid , Unsaturated carboxylic acids such as styrene sulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth) acrylamide, N- Alkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide, (alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2 -Unsaturated amides such as ethylhexyl group, cyclohexyl group, etc .; Vinyl esters such as vinyl acetate and vinyl propionate; Vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; Vinyl chloride, Halogen-containing α, β-unsaturated monomers such as vinylidene chloride; α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene can be mentioned, and one or more of these monomers can be used. Can be used.

From the viewpoint of improving adhesion, the amount of the oxazoline group of the oxazoline compound is preferably 0.5 to 10 mmol / g, particularly 1 mmol / g or more or 9 mmol / g or less, and 3 mmol / g or more or 8 mmol / g or less among them. Among them, it is more preferably 4 mmol / g or more or 6 mmol / g or less.

(Isocyanate compound)
The isocyanate compound used as a cross-linking agent is, for example, an isocyanate or a compound having an isocyanate derivative structure typified by blocked isocyanate.
The isocyanate has, for example, aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyldiisocyanate, phenylenedi isocyanate and naphthalenedi isocyanate, and aromatic rings such as α, α, α', α'-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as aliphatic isocyanates, methylene diisocyanates, propylene diisocyanates, lysine diisocyanates, trimethylhexamethylene diisocyanates, hexamethylene diisocyanates, cyclohexane diisocyanates, methylcyclohexane diisocyanates, isophorone diisocyanates, methylenebis (4-cyclohexylisocyanates), isopropyridene dicyclohexyldiisocyanates, etc. The alicyclic isocyanate of the above can be exemplified. In addition, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimides of these isocyanates can also be mentioned. These may be used alone or in combination of two or more. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are preferable as measures against yellowing due to ultraviolet irradiation.

When used in the state of blocked isocyanate, the blocking agent includes, for example, phenolic compounds such as heavy sulfites, phenol, cresol and ethylphenol, and alcoholic compounds such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol and ethanol. Compounds, active methylene compounds such as methyl isobutanoyl acetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, ε-caprolactam, δ-valerolactam, etc. Lactam compounds, amine compounds such as diphenylaniline, aniline, ethyleneimine, acetoanilide, acid amide compounds of acetate amide, formaldehyde, acetoaldoxime, acetone oxime, methyl ethyl ketone oxime, cyclohexanone oxime and other oxime compounds. These can be used alone or in combination of two or more.

The isocyanate compound may be used alone, or may be used as a mixture or a bond with various polymers. From the viewpoint of improving the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or a bond with a polyester resin or a urethane resin.

(Epoxy compound)
The epoxy compound used as a cross-linking agent is a compound having an epoxy group in the molecule, and is, for example, a condensate of epichlorohydrin and a hydroxyl group or an amino group such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin, or bisphenol A. Examples thereof include polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and glycidylamine compounds.
Examples of the polyepoxy compound include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyltris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, and trimethylolpropane. Examples of the polyglycidyl ether and the diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and propylene glycol diglycidyl ether. , Polypropylene glycol diglycidyl ether, Polytetramethylene glycol diglycidyl ether, Monoepoxy compounds include, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenylglycidyl ether, glycidylamine compounds N, N, N', N ′ -Tetraglycidyl-m-xylylene diamine, 1,3-bis (N, N-diglycidylamino) cyclohexane and the like can be mentioned. From the viewpoint of improving adhesion, a polyether epoxy compound is preferable. Further, as the amount of the epoxy group, a polyepoxy compound having trifunctional or higher functionalities is preferable to bifunctional.

(Melamine compound)
The above-mentioned melamine compound used as a cross-linking agent is a compound having a melamine skeleton in the compound, for example, an alkylolated melamine derivative or a compound obtained by reacting an alkylolated melamine derivative with an alcohol to partially or completely etherify. , And a mixture thereof can be used.
As the alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Further, the melamine compound may be either a monomer or a multimer of a dimer or more, or a mixture thereof may be used. Further, a type in which urea or the like is copolymerized with a part of melamine, or a catalyst can be used in combination to improve the reactivity of the melamine compound.

The content of the cross-linking agent is preferably 10 parts by mass or more, particularly 20 parts by mass or more, and 25 parts by mass among them, with respect to 100 parts by mass of the curable monomer, from the viewpoint of obtaining good coating film strength. The above is more preferable. 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 more preferably 40 parts by mass or less.

(Carbodiimide compound)
The carbodiimide compound used as a cross-linking agent is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule. A polycarbodiimide-based compound having two or more in the molecule is more preferable for better adhesion and the like.
This carbodiimide compound can be synthesized by a conventionally known technique, and a condensation reaction of a diisocyanate compound is generally used. The diisocyanate compound is not particularly limited, and any aromatic or aliphatic type can be used. Specifically, tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylenedi isocyanate, naphthalenedi isocyanate, etc. Examples thereof include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyldiisocyanis, and dicyclohexylmethane diisocyanate.

The content of the carbodiimide group contained in the carbodiimide compound is a carbodiimide equivalent (weight [g] of the carbodiimide compound for giving 1 mol of the carbodiimide group), preferably 100 to 1000, and more than 250 or 800 or less. Among them, it is more preferably 300 or more or 700 or less. By using in the above range, the durability of the coating film is improved.

(Other ingredients)
(Polyol compound)
Examples of the polyol compound include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, and 1,4-butane. Diol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, 1,9-nonanediol, 2,2-dimethylolheptan, tri Methylene glycol, 1,4-tetramethylene glycol, dipropylene glycol, 1,3-tetramethylenediol, 2-methyl-1,3-trimethylenediol, 2,4-diethyl-1,5-pentamethylenediol, water Additive bisphenol A, hydroxyalkylated bisphenol A, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol, 2,2,4-trimethyl-1,3-pentanediol, N, N-bis- (2-hydroxy) Low molecular weight diols such as ethyl) dimethyl hydantin; polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, polybutadiene polyols, (meth) acrylic polyols, polycaprolactone polyols, polysiloxane polyols, polyurethanes Examples thereof include high molecular weight polyols such as system polyols.

Examples of the polyether polyol include oxyalkylene structure-containing polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutylene glycol, and polyhexamethylene glycol, and random or block co-weights of these polyalkylene glycols. Coalescence is mentioned.

Among these, an oxyalkylene structure-containing polyether polyol is preferable, and the number of carbon atoms in the alkylene structure is preferably 2 to 6, particularly preferably 2 to 4, and even more preferably 4.

Examples of the polyester-based polyol include a condensation polymer of a polyhydric alcohol and a polyvalent carboxylic acid; a ring-opening polymer of a cyclic ester (lactone); a polyhydric alcohol, a polyvalent carboxylic acid, and a cyclic ester. Examples thereof include reactants.
Examples of the polyhydric alcohol include the low molecular weight diols mentioned above.
Examples of the polyvalent carboxylic acid include aliphatic dicarboxylic acids such as malonic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecandioic acid; 1,4 An alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, paraphenylenedicarboxylic acid and trimellitic acid can be mentioned.
Examples of the cyclic ester include propiolactone, β-methyl-δ-valerolactone, and ε-caprolactone.

Examples of the polycarbonate-based polyol include a reaction product of a polyhydric alcohol and a phosgene; a transesterification reaction product of a carbonic acid ester and a polyhydric alcohol.
Examples of the polyhydric alcohol include the low molecular weight diol and the like, and examples of the alkylene carbonate include ethylene carbonate, dimethyl carbonate, diethyl carbonate, di-n-propyl carbonate, diisopropyl carbonate, dibutyl carbonate, dicyclohexyl carbonate and the like. Examples include diphenyl carbonate.
The polycarbonate-based polyol may be a compound having a carbonate bond in the molecule and having a hydroxyl group at the end, and may have an ester bond together with the carbonate bond.

<Curable composition for forming the cured resin layers (A) and (B)>
Examples of the curable composition for forming the cured resin layers (A) and (B) include a combination of a hydroxyl group-containing (meth) acrylate compound and an isocyanate compound, or a hydroxyl group-containing (meth) acrylate compound and an isocyanate. Examples thereof include urethane (meth) acrylate compounds obtained by combining a compound and a polyol compound.
Further, a combination of acrylic acid esters and a crosslinkable monomer having a vinyl group, a combination of methacrylic acid esters and a crosslinkable monomer having a vinyl group, acrylic acid esters and a hydroxyl group-containing (meth) acrylate type. Examples thereof include a combination with a compound, a combination of methacrylic acid esters and a hydroxyl group-containing (meth) acrylate-based compound, and the like. However, it is not limited to these.

The curable composition for forming the cured resin layers (A) and (B) preferably has a viscosity at 25 ° C. of 10 to 60 mPa · s as measured by an E-type viscometer in order to improve coatability. Above all, it is more preferably 30 mPa · s or less, among them 20 mPa · s or less, among them 15 mPa · s or less, and among them 12 mPa · s or less.

<Method of forming the cured resin layer (A)>
The cured resin layer (A) is coated with a curable composition using a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, and inkjet, and then light. It is preferably formed by irradiation, for example, irradiation with ultraviolet rays and curing.

<Method of forming the cured resin layer (B)>
As a method of providing the cured resin layer (B), a curable composition is applied by using a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, and inkjet. After that, it is preferably formed by irradiating with light, for example, ultraviolet rays and curing.

<< Physical properties of this laminated film >>
(Pencil hardness)
In the present laminated film having the above structure, the surface hardness of the film, specifically, the pencil hardness on the surface of the cured resin layer (B) can be 2H or more, and in particular, 3H or more.

(Repeat bendability)
The laminated film having the above structure is provided with a cured resin layer (A) on the surface of the base film, and the elasticity of the cured resin layer (A) is higher than that of the cured resin layer (B). By setting it low, it was possible to further enhance the practical repeatability.
Therefore, this laminated film can obtain durability without cracks even if it is bent 200,000 times or more in the repeated bendability evaluation (under the condition of R = 2.5).

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

<< Features and applications of this laminated film >>
From the examples and the test results conducted by the inventor so far, if this laminated film is used, the surface hardness (for example, 2H or more in the pencil hardness evaluation) and the repetitive bendability (R = 2.5 condition) are used at a high level. , 200,000 times bending) was found to be compatible.
By adjusting the thickness of the cured resin layer (A) corresponding to the first layer and the cured resin layer (B) of the second layer, the stress propagation into the cured resin layer (B) applied when the laminated film is bent is reduced. It is speculated that it will be possible. Therefore, in the conventional method (whole coating formulation with a single layer structure), a resin component composed of an acrylic monomer, which has been considered difficult to use, can also be used, which has an advantage of increasing the degree of freedom when designing a laminated film. .. Furthermore, it is presumed that the two-layer structure of the cured resin layer (A) and the cured resin layer (B) can be expected to disperse stress in the thickness direction, which can contribute to further improvement of bending durability.

Further, by setting the elastic modulus of the cured resin layer (A) to be lower than the elastic modulus of the cured resin layer (B), the surface hardness (for example, 2H or more in the pencil hardness evaluation) and the repetitive bending property (for example, 2H or more in the pencil hardness evaluation) are set at a high level. It was found that it is possible to achieve compatibility with the fact that it can be bent 200,000 times under the condition of R = 2.5). On the other hand, it was also found that it is difficult to achieve both the desired hard coat property and the repetitive bendability by simply adopting the above-mentioned two-layer structure (Comparative Examples 3 to 5).

Further, it was found that it is not necessary to extremely increase the tensile elastic modulus of the base film to be used if the two-layer structure including the cured resin layer (A) and the cured resin layer (B) as described above is used.
Conventionally, in a laminated film having a surface layer having a high surface hardness, when designing a target surface hardness to a desired level (for example, 2H or more), the base film used is constructed as necessary. It was necessary to review the structural design of the raw material and further increase the tensile elastic modulus.
On the other hand, by using the two-layer structure of the cured resin layer (A) and the cured resin layer (B) as described above, it is possible to appropriately select a general-purpose base film on the market. It has the advantage of increasing the degree of freedom in terms of selecting the base film.

This laminated film has excellent surface hardness, practical repetitive bendability, and can also obtain transparency, so it is used for surface protection, displays, and especially for front panels. Can be used for. For example, it can be suitably used as a surface protective film, particularly a surface protective film for a display, and among them, a surface protective film for a flexible display. However, the use of this laminated film is not limited to these uses.

<< Explanation of words >>
In the present invention, the term "film" shall include the "sheet", and the term "sheet" shall include the "film".

In the present invention, when "X to Y" (X, Y are arbitrary numbers) is described, it means "X or more and Y or less" and "preferably larger than X" or "preferably Y", unless otherwise specified. It also includes the meaning of "smaller".
In addition, when "X or more" (X is an arbitrary number) is described, it includes the meaning of "preferably larger than X" and is described as "Y or less" (Y is an arbitrary number) unless otherwise specified. In this case, unless otherwise specified, it also includes the meaning of "preferably smaller than Y".

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

(1) Method for measuring film thickness of cured resin layer Each laminated film was adhered onto a glass slide glass using "Aron Alpha Series" manufactured by Toagosei Co., Ltd. to prepare a sample for SAICS (Psycus). The obtained SAICS sample was set in Cycus (DN-01 type manufactured by Daipla Wintes Co., Ltd.), and a notch with a width of 300 μm and a depth of 1 μm was made in advance with a diamond cutting edge. The cut was made using a single crystal diamond blade having a V angle of 80 °, a squeeze angle of 5 °, and a niger angle of 5 °. For the measurement, a borazon cutting edge having a width of 300 μm is set in the sample in which a notch having a width of 300 μm is made in advance, and each cured resin layer is measured at an arbitrary depth, a horizontal speed of 1 μm / s, and a vertical speed of 0.5 μm / s. The film thickness was measured. For the measurement, a boron nitride blade having a blade width dimension of 0.3 mm, a squeeze angle of 20 °, and a niger angle of 10 ° was used. The material strength was measured from the vertical displacement position and the cutting force, and the thickness of each layer was confirmed.

(2) Film haze (transparency)
The film haze of each laminated film was measured using a haze meter HM-150 manufactured by Murakami Color Technology Research Institute in accordance with JIS K 7136.
(Criteria)
A (good): 5% or less B (poor): higher than 5%

(3) Pencil hardness (hard coat property)
The pencil hardness was evaluated with a pencil hardness tester (manufactured by Yasuda Seiki Co., Ltd.) under a load condition of 750 g in accordance with JIS K 5600-5-4. Based on the result, it was judged according to the following criteria.
(Criteria)
A (good): Pencil hardness is 3H or more.
B (little good): Pencil hardness is 2H or more and less than 3H.
C (poor): Pencil hardness is less than 2H.

(4) Repeated foldability A bending tester (DLDMLLH-FS, manufactured by Yuasa System Co., Ltd.) was used to perform a test so that the cured resin layer side of the laminated film was the outer surface, and the cured resin on the outer surface. The presence or absence of cracks in the layer was visually confirmed.
Then, the number of repeated bends was measured together with the minimum radius (R) at which cracks did not occur, and the determination was made according to the following criteria based on the result.
(Criteria)
A (good): R = 2.5 or less and can be repeatedly bent 200,000 times.
B (little good): R = 2.5 or more, or the number of repeated bends is 10,000 or more and less than 200,000 C (poor): R = 2.5 or more, or the number of repeated bends is 10,000 times Less than.

(5) Evaluation by specifying the bending direction (In / Out) Using a bending tester (DLDMLLH-FS manufactured by Yuasa System Co., Ltd.), the cured resin layer side of the laminated film is the inner surface (In) or the outer surface (In). The test was carried out so as to be Out), and the presence or absence of cracks in the cured resin layer on the inner surface (In) or the outer surface (Out) was visually confirmed.
Then, the minimum radius (R) at which cracks do not occur was measured, and based on the result, the determination was made according to the following criteria.
(Criteria)
A (good): R = 1.5 or more and less than 2.0 for both Out / In B (little good): Out is R = 2.0 or more and less than R2.5 C (poor): Out is R = 2.5 that's all

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

(7) Refractive index of the cured resin layer (A) and the cured resin layer (B) The refractive index of each layer was determined by Abbe measurement. Based on the result, it was judged according to the following criteria.
(Criteria)
A (good): The difference in refractive index between the cured resin layer (A) and the cured resin layer (B) is 0.15 or less.
B (poor): The difference in refractive index between the cured resin layer (A) and the cured resin layer (B) exceeded 0.15.

(8) Adhesion between the cured resin layer (A) and the cured resin layer (B) In accordance with JIS K 5600-5-6, the cured resin layer (A) and the cured resin layer (A) are subjected to the cross-cut method (10 x 10 100 squares). The adhesion with the cured resin layer (B) was evaluated. Based on the result, it was judged according to the following criteria.
(Criteria)
A (good): Good adhesion on the entire surface (area of adhesion: 100%)
B (little good): Partially peeled off.
(Area in close contact: 50% or more and less than 100%)
C (poor): Partial peeling or total peeling occurs.
(Area in close contact: less than 50%)

(9) Comprehensive evaluation Each laminated film obtained in Examples and Comparative Examples was judged according to the following judgment criteria.
(Criteria)
A (good): Transparency, hard coat property, repetitive bendability, bend direction, refractive index difference 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 in B), all are A.
B (little good): transparency, hard coat property, repetitive bendability, bending direction, refractive index difference 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 in (B), at least one is B and the rest is A.
C (poor): Transparency, hard coat property, repetitive bendability, bend direction, refractive index difference 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 the adhesion of B), at least one of the hard coat property, the repeat bendability and the bend directionability is C, and the rest is A or B.

The various materials used in the examples and comparative examples were prepared as follows.

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

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

<Base film F3>
Co., Ltd .: Polyimide film (product name "C50"), thickness: 50 μm, tensile elastic modulus (JIS K 7161) 6.9 GPa.

<Acrylate (A)>
98 parts by mass of glycidyl methacrylate ("Acryester G" manufactured by Mitsubishi Chemical Co., Ltd.) and 1 part by mass of methyl methacrylate ("Acryester M" manufactured by Mitsubishi Chemical Co., Ltd.) in a reactor equipped with a stirrer, a reflux cooling tube and a thermometer. Add 1 part by mass of ethyl acrylate (manufactured by Mitsubishi Chemical Co., Ltd.), 1.9 parts by mass of mercaptopropyltrimethoxysilane ("KBM803" manufactured by Shinetsu Chemical Industry Co., Ltd.), and 157.3 parts by mass of propylene glycol monomethyl ether (PGM), and start stirring. Later, the inside of 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 Fuji Film Wako Pure Chemical Industries, Ltd.), the temperature inside the system was raised to 65 ° C. After stirring for 3 hours, 0.5 parts by mass of V-65 was further added and the mixture was stirred at 65 ° C. for 3 hours. The temperature inside the system was raised to 100 ° C., and after stirring for 30 minutes, 0.45 parts by mass of p-methoxyphenol (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) and 138.1 parts by mass of PGM were added, and the temperature inside the system was again 100 ° C. The temperature was raised to. Next, after adding 3.1 parts by mass of triphenylphosphine (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), 50.7 parts by mass of acrylic acid (manufactured by Mitsubishi Chemical Industries, Ltd.) was added, and the temperature was raised to 110 ° C. for 6 hours. Stirring gave a solution of acrylate (A) having a (meth) acryloyl group in the side chain. The composition of the reaction solution was X / PGM = 30/70 (mass ratio).

[Example 1]
The curable composition a prepared as described below is applied onto the base film F2 with a bar coater at 25 ° C. so that the coating thickness (after drying) is 2.0 μm, and 1 min at 90 ° C. It was dried by heating.
Next, the curable composition b prepared as described below was applied with a bar coater so as to coat the cured resin layer (A) so that the coating thickness (after drying) was 3.0 μm, and 90 After drying by heating at ° C. for 1 min, the cured resin layers (A) and (B) are cured by irradiating with ultraviolet rays of 400 mJ / cm ^{2 in} an integrated light amount, and the base film F2 / cured resin layer (A) / A laminated film having a laminated structure of the cured resin layer (B) was obtained.

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

(Curable composition b)
To 100 parts by mass of urethane acrylate (Shikou "UT-5670" manufactured by Mitsubishi Chemical Co., Ltd.), 67 parts by mass of silica particles (MEK-AC-2140Y manufactured by Nissan Chemical Co., Ltd.) and 5 parts by mass of photopolymerization initiator are added and cured. The sex composition b was prepared. The mass average molecular weight of the curable composition b was 10,500, and the refractive index of the cured resin layer (B) was 1.50.

[Example 2]
A laminated film was obtained in the same manner as in Example 1 except that the thicknesses of the cured resin layer (A) and the cured resin layer (B) were changed in Example 1.

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

(Curable composition b1)
67 parts by mass of alumina particles (ALTPGDA manufactured by CIK Nanotech Co., Ltd.) and 5 parts by mass of a photopolymerization initiator were added to 100 parts by mass of acrylate (A) 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 cured resin layer (B) was 1.54.

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

[Example 5]
In Example 1, a laminated film was obtained in the same manner as in Example 1 except that the base film F2 was changed to the base film F3.

[Comparative Example 1]
Similar to Example 1, the curable composition a is applied onto the base film F2 with a bar coater at 25 ° C. so that the coating thickness (after drying) is 5.0 μm, and heated at 90 ° C. for 1 min. After drying, a cured resin layer (A) having a thickness (after drying) of 5.0 μm was formed by irradiating ultraviolet rays of 400 mJ / cm ² with an integrated light amount to obtain a laminated film. At this time, the cured resin layer (B) was not formed.

[Comparative Example 2]
Similar to Example 1, the curable composition b was applied onto the base film F2 with a bar coater so that the coating thickness (after drying) was evenly 5.0 μm, and heated at 90 ° C. for 1 min. After drying, a cured resin layer (B) having a thickness (after drying) of 5.0 μm was formed by irradiating ultraviolet rays of 400 mJ / cm ² with an integrated light amount to obtain a laminated film. At this time, the cured resin layer (A) was not formed.

[Comparative Example 3]
Laminated film in the same manner as in Example 1 except that the curable composition a was changed to the next curable composition a1 and the curable composition b was changed to the next curable composition b2 in Example 1. Got

(Curable composition a1)
A curable composition a1 was prepared by adding 5 parts by mass of a photopolymerization initiator to 100 parts by mass of urethane acrylate (Shikou "UV-6640B" manufactured by Mitsubishi Chemical Corporation). The curable composition a1 had a mass average molecular weight of 5,000 and the refractive index of the cured resin layer (A) was 1.51.

(Curable composition b2)
A curable composition b2 was prepared by adding 80 parts by mass of DPHA and 5 parts by mass of a photopolymerization initiator to 100 parts by mass of urethane acrylate (Shikou "UV-1700B" manufactured by Mitsubishi Chemical Corporation). The curable composition b2 had a mass average molecular weight of 2,000, and the refractive index of the cured resin layer (B) was 1.51.
DPHA: Aronix M-404 (dipentaerythritol hexaacrylate / dipentaerythritol pentaacrylate) manufactured by Toagosei Co., Ltd.

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

[Comparative Example 5]
Laminated film in the same manner as in Example 1 except that the curable composition a was changed to the next curable composition a2 and the curable composition b was changed to the next curable composition b3 in Example 1. Got

(Curable composition a2)
A curable composition a2 was prepared by adding 100 parts by mass of 6 molEO-modified DPHA, 200 parts by mass of silica particles (MEK-AC-2140Y manufactured by Nissan Chemical Industries, Ltd.), and 5 parts by mass of a photopolymerization initiator to 100 parts by mass of the above DPHA. .. The mass average molecular weight of the curable composition a2 was 790, and the refractive index of the cured resin layer (A) was 1.50.

(Curable composition b3)
A curable composition b3 was prepared by adding 100 parts by mass of pentaerythritol triacrylate and 5 parts by mass of a photopolymerization initiator to 100 parts by mass of urethane acrylate (Shikou "UV-7650B" manufactured by Mitsubishi Chemical Corporation). The curable composition b3 had a mass average molecular weight of 2,300, and the refractive index of the cured resin layer (B) was 1.51.

[Comparative Example 6]
Laminated film in the same manner as in Example 1 except that the curable composition a was changed to the next curable composition a3 and the curable composition b was changed to the next curable composition b4 in Example 1. Got

(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 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 cured resin layer (A) was 1.50.

((Meta) acrylic polymer solution)
283 parts by mass of methylisobutylketone, 149 parts by mass of glycidyl methacrylate, 276 parts by mass of methyl methacrylate, and 25 parts by mass of t-butylperoxy-2-ethylhexanoate (manufactured by Nippon Emulsifier Co., Ltd., trade name: Perbutyl O) Was synthesized to obtain a precursor, and 76 parts by mass of acrylic acid was added thereto for synthesis to obtain 1000 parts by mass (50.0% by mass) of a methylisobutylketone solution of a (meth) acrylic polymer.
The property values of the (meth) acrylic polymer were as follows.
Weight Average Molecular Weight (Mw): 15,000,
Theoretical acryloyl group equivalent in terms of solid content: 478 g / eq,
Hydroxy group value: 117 mgKOH / g.

(Polyisocyanate)
Burnock DN-950 (adduct type polyisocyanate) manufactured by DIC Corporation

(Curable composition b4)
A curable composition b4 was prepared by adding 6 parts by mass of the following polyisocyanate and 8 parts by mass of the DPHA to 100 parts by mass of the following (meth) acrylic polymer solution. The curable composition b4 had a mass average molecular weight of 40,000, and the refractive index of the cured resin layer (B) was 1.52.

((Meta) acrylic polymer solution)
229 parts by mass of methyl isobutyl ketone was charged into a reactor equipped with a stirrer, a cooling tube, a dropping funnel and a nitrogen introduction tube, and the temperature was raised to 110 ° C. with stirring, and then glycidyl methacrylate 309 A mixed solution consisting of 10 parts by mass of mass, 34 parts by mass of methyl methacrylate, and 10 parts by mass of t-butylperoxy-2-ethylhexanoate (manufactured by Nippon Emulsifier Co., Ltd., product name: perbutyl O) was added dropwise over 3 hours. After further dropping, the mixture was kept at 110 ° C. for 15 hours. Then, after lowering the temperature of the mixed solution to 90 ° C., 0.1 part by mass of methquinone and 157 parts by mass of acrylic acid were charged, and then 3 parts by mass of triphenylphosphine was added and the temperature was raised to 100 ° C. After holding for 8 hours, the mixture was diluted with methyl isobutyl ketone to obtain 1000 parts by mass (50.0% by mass) of a methyl isobutyl ketone solution of the (meth) acrylic polymer (A1).
The property values of the (meth) acrylic polymer (A) were as follows.
Weight average molecular weight (Mw): 40,000,
Theoretical acryloyl group equivalent in terms of solid content: 230 g / eq,
Hydroxy group value: 244 mgKOH / g.

(Polyisocyanate)
Barnock DN-980S (isocyanurate type polyisocyanate) manufactured by DIC Corporation

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

<Discussion>
Based on the above examples and the test results conducted by the inventor so far, the cured resin layer (A) and the cured resin layer (B) are sequentially laminated on the surface of the base film, and the elastic modulus is described. , The cured resin layer (B)> the cured resin layer (A), and the difference between the elastic modulus of the cured resin layer (A) and the elastic modulus of the cured resin layer (B) ((B)-(A)) is 0 ( By having the characteristics of being larger than MPa) and smaller than 220 (MPa), it has a high level of surface hardness (for example, 2H or more in pencil hardness evaluation) and repetitive bendability (under the condition of R = 2.5, 200,000). It was found that it is possible to achieve both the ability to bend and bend.
On the other hand, it was also found that it is difficult to achieve both the desired hard coat property and the repetitive bendability only by forming the two-layer structure as in Comparative Examples 3 to 6.
The reason why such a difference occurs is that the difference ((B)-(A)) between the elastic modulus of the cured resin layer (A) and the elastic modulus of the cured resin layer (B) is larger than 0 (MPa) and 220 (MPa). ), It is possible to reduce the stress propagation into the cured resin layer (B) that is applied when the laminated film is bent, and the stress in the thickness direction is dispersed, which contributes to the improvement of bending durability. It is presumed that it is.

At this time, it was confirmed that the elastic modulus of each of the cured resin layers (A) and (B) should be adjusted by adjusting the thickness and composition of each of the cured resin layers (A) and (B), for example, the particle content. We were able to. Therefore, in the conventional method (whole coating formulation with a single layer structure), a resin component composed of an acrylic monomer, which has been considered difficult to use, can also be used, which has an advantage of increasing the degree of freedom when designing a laminated film. ..

If the difference ((B)-(A)) between the elastic modulus of the cured resin layer (A) and the elastic modulus of the cured resin layer (B) is larger than 0 (MPa) and smaller than 220 (MPa), it can be used. It was also found that it is not necessary to make the tensile elastic modulus of the base film to be extremely large.
Conventionally, in a laminated film having a surface layer having a high surface hardness, when designing a target surface hardness to a desired level (for example, 2H or more), the base film used is constructed as necessary. The structural design of the raw material had to be reviewed to further increase the tensile modulus.
On the other hand, if the two-layer structure of the cured resin layer (A) and the cured resin layer (B) is used, it is possible to appropriately select a general-purpose base film on the market, and the base film can be appropriately selected. It has the advantage of increasing the degree of freedom in terms of selection.

In the above example, the case where the elastic modulus of the cured resin layer (A) measured by the micro-hardness meter measurement (JIS Z 2255) is 330 MPa is examined. For example, from the viewpoint of excluding an extremely flexible layer such as an adhesive layer, it is presumed that the same effect can be obtained if the elastic modulus of the cured resin layer (A) is 10 MPa or more.

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

Claims (16)

1. A cured resin layer (A) and a cured resin layer (B) are sequentially laminated on the surface of the base film.
   Regarding the elastic modulus measured by the micro-hardness meter measurement (JIS Z 2255), the elastic modulus of the cured resin layer (B) is larger than the elastic modulus of the cured resin layer (A), and the cured resin layer (A) The laminated film is characterized in that the difference between the elastic modulus of the above and the elastic modulus of the cured resin layer (B) is larger than 0 (MPa) and smaller than 220 (MPa).
2. The laminated film according to claim 1, wherein the elastic modulus of the cured resin layer (A) is 10 (MPa) or more.
3. The laminated film according to claim 1 or 2, wherein the pencil hardness on the surface of the cured resin layer (B) is 2H or more.
4. The laminated film according to any one of claims 1 to 3, which can be bent 200,000 times or more in a repeated foldability evaluation (under the condition of R = 2.5).
5. The laminated film according to any one of claims 1 to 4, wherein the film haze is 5.0% or less.
6. 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.
7. The laminated film according to any one of claims 1 to 6, wherein the base film is a polyester film.
8. The laminated film according to any one of claims 1 to 7, wherein the base film is a polyethylene naphthalate (PEN) film.
9. The laminated film according to any one of claims 1 to 7, wherein the base film is a polyethylene terephthalate (PET) film.
10. The laminated film according to any one of claims 1 to 7, wherein the base film is a polyimide (PI) film.
11. The laminated film according to any one of claims 1 to 10, wherein the difference in refractive index between the cured resin layer (A) and the cured resin layer (B) is 0.15 or less.
12. 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.
13. The laminated film according to any one of claims 1 to 12, which is for surface protection.
14. The laminated film according to any one of claims 1 to 12, which is for a display.
15. The laminated film according to any one of claims 1 to 12, which is used for a front plate.
16. The method for producing a laminated film according to any one of claims 1 to 12.
    The cured resin layer (A) is characterized in that the curable composition is applied onto a base film and cured to form the curable composition, and the curable composition has a mass average molecular weight in the range of 1,000 to 500,000. A method for producing a laminated film, which is characterized by the above.