JP2020097165A - Laminated film - Google Patents

Abstract

To provide a novel laminated film not only provided with excellent surface hardness but also excellent in practicable repeated flexure properties.SOLUTION: The laminated film is provided that comprises: a scatter cured resin part (A) in which a plurality of protrusions are scattered at intervals on a substrate film, and a cured resin layer (B) covering the scatter resin part (A), wherein the relationship between a protrusion height Hof the scatter cured resin part (A) and a layer thickness Hof the cured resin layer (B) satisfies an inequation: 2×H≥H, and the relationship between an elastic modulus (MPa) of the scatter cured resin part (A) and an elastic modulus (MPa) of the cured resin layer (B) satisfies an inequation: an elastic modulus of the cured resin layer (B)-an elastic modulus of the scatter cured resin part (A)>50(MPa) with regard to an elastic modulus measured by microhardness tester measurement (JIS Z 2255).SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminated film having excellent surface hardness and repeated bending properties.

2. Description of the Related Art In recent years, with the miniaturization and weight reduction of electronic devices and the like, there is a tendency that flexible substrates and flexible printed circuits are used. Further, along with this trend, demands for flexibility also tend to increase in display applications. Then, in the surface protection film for display screens used for such applications, not only the surface protection characteristics such as high hardness, scratch resistance, stain resistance, and abrasion resistance, but also a high degree of bendability is required. Therefore, further performance improvement has been demanded.

Therefore, in recent years, many proposals have been made for the surface protection film in order to improve flexibility or flexibility while maintaining high hardness and scratch resistance.
For example, Patent Document 1 proposes a protective film devised from the structural aspect of the hard coat layer. The protective film includes a first hard coat layer provided by curing resin on the surface of the base material in a dotted pattern, and the dot hard resin of the first hard coat layer, and the surface of the hard coat. The second hard coat layer covering the first hard coat layer is formed on the base film so as to be smooth. It is disclosed that the protective film has excellent adhesion to the base film, flexibility and surface hardness.

In Patent Document 2, for example, urethane (meth)acrylate, tripentaerythritol octa(meth)acrylate, and a polymerization initiator are essential as examples of curable compositions in which the composition of the active energy ray-curable composition is devised. An active energy ray-curable composition characterized by being contained as a component has been proposed. It is disclosed that a hard coat, which is a cured coating film of such a composition, has high hardness and excellent flexibility.

In Patent Document 3, a hard coat composed of dots is formed on a base film as a surface protection film which has high hardness and is hard to be scratched, and which can withstand specifications such as rolling and bending. Each of the dots is a cured product of a curable composition, and each dot has an area of the top surface of the dot of 1×10 ⁻⁶ to 1 mm ² , and a dot center distance in the dot group is 10 to 10. There is disclosed a surface protective film having a thickness of 1000 μm and the number of dots per 1 cm ^{2 of the} coating film is 100 to 1×10 ⁶ .

JP 2000-84477 A JP, 2013-23585, A JP, 2016-93979, A

As described above, in recent years, development of a flexible mobile terminal capable of folding or folding an image display screen (display) has been advanced, and a surface protective film used for this type of image display screen also has an excellent surface. Along with hardness, practically repeatable bending, specifically, durability capable of being repeatedly bent 100,000 times or more is required.
However, none of the inventions described in Patent Documents 1 to 3 is supposed to be used for repeatedly bending, and there are cases where it is difficult to handle.

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

The present invention includes a dotted cured resin portion (A) in which a plurality of convex portions are scattered at intervals on the surface of a substrate film, and a cured resin layer that covers the dotted resin portion (A). Equipped with (B),
The relationship between the height H _A of the convex portion of the dotted cured resin portion (A) and the layer thickness H _B of the cured resin layer (B) satisfies 2×H _A ≧H _B , and
Regarding the elastic modulus measured by a micro hardness meter measurement (JIS Z 2255), the relationship between the elastic modulus (MPa) between the dotted cured resin portion (A) and the cured resin layer (B) is the cured resin layer (B)- A laminated film is proposed which is characterized by satisfying the dotted cured resin portion (A)>50 (MPa).

The laminated film proposed by the present invention includes a dotted cured resin portion (A) in which a plurality of convex portions are scattered at intervals on the surface of a base film. That is, since the convex portions made of the cured resin composition are discontinuously provided in the dotted cured resin portion (A), the curable resin can be practically repeatedly bent while maintaining curability. Moreover, the elastic modulus of the dotted cured resin portion (A) is set lower than that of the cured resin layer (B), and the height H _A of the convex portion of the dotted cured resin portion (A) and the cured resin When the relationship with the layer thickness H _B of the layer (B) satisfies 2×H _A ≧H _B , the repeatability can be further enhanced. Specifically, even when repeatedly bent 100,000 times or more, there is a problem. It was possible to obtain excellent repeated bending characteristics.

It is sectional drawing shown typically in order to demonstrate the structural example of the laminated film of this invention. It is a top view showing an example of a scattered hardening resin part (A). It is a top view for explaining the measuring method of the coverage of the dotted hardening resin part (A) in an example.

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

<<This laminated film>>
A laminated film according to an example of an embodiment of the present invention (referred to as “present laminated film”) has a plurality of convex portions spaced at least on one surface side of a substrate film (referred to as “present substrate film”). And a cured resin layer (B) that covers the dotted resin portion (A).
The laminated film may have other layers as long as it has the above-mentioned structure.

<The base film>
The present base material film is not limited in material and constitution as long as it is a film capable of obtaining necessary and sufficient rigidity and repetitive bendability.

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

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. Such a film is called a "polyester film" or a "polyimide film".
In this case, the "main component resin" means a resin having the highest content ratio among the resins constituting the present base film, and for example, 50% by mass or more, particularly 70 wt% of the resins constituting the present base film. % Or more, and particularly 80% by mass or more (including 100% by mass).
In addition, each layer which comprises this base material film may contain other resin other than polyester or polyimide, or a component other than resin, if the main component resin is polyester or polyimide.

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

When the present polyester is 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 copolyester, 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 kind or two or more kinds 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), and polybutylene naphthalate (PBN). Among them, PET and PEN are preferable in terms of handleability.
When the main component resin of each layer constituting the present 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 resin.

(Polyimide)
As the base material film, a polyimide film is also suitable in addition to the polyester film. Regarding the imidization of the polyimide, for example, a method in which a diamine and a dianhydride, particularly an aromatic dianhydride and an aromatic diamine are polyamic acid polymerized at an equivalent ratio of 1:1 and then imidized is exemplified.
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 tetra Examples thereof include carboxylic acid dianhydride (BTDA), biphenyltetracarboxylic acid dianhydride (BPDA), and biscarboxyphenyldimethylsilane dianhydride (SiDA). These may be used alone or in combination of two or more.
As the aromatic diamine, oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), p-methylenedianiline (pMDA), m-methylenedianiline (mMDA), Examples 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 present base material film may contain a resin other than polyester and polyimide (PI) as a main component resin. As the main component resin in that case, for example, epoxy, polyarylate, polyether sulfone, polycarbonate, polyether ketone, polysulfone, polyphenylene sulfide, polyester liquid crystal polymer, triacetyl cellulose, cellulose derivative, polypropylene, polyamides, poly Cycloolefins etc. can be illustrated.

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

The shape of the particles is not particularly limited. For example, it may be spherical, block-shaped, rod-shaped, or flat.
Further, the hardness, specific gravity, color, etc. 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 further preferably 0.5 μm or more or 2.5 μm or less. When it exceeds 5 μm, the surface roughness of the present base film becomes too rough, and problems may occur when a cured resin layer made of various cured compositions is formed in a subsequent step.

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

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

(Other ingredients)
The present base film may contain other components, for example, conventionally known antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, ultraviolet absorbers, etc., if necessary. ..

(Thickness)
The thickness of the present base film is preferably, for example, 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 from the viewpoint that necessary and sufficient rigidity and repetitive bendability can be obtained. Is more preferable.

(Manufacturing method)
The base film can be formed, for example, by forming the resin composition into a film by a melt film forming method or a solution film forming method. In the case of a multilayer structure, you may coextrude.
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 present base film is preferably 2 GPa or more, in particular 8 GPa or less, and particularly 3 GPa or more or 7 GPa or less, from the viewpoint that necessary and sufficient rigidity and repetitive bending property can be obtained. Among them, it is more preferably 3 GPa or more or 5 GPa or less.

<Spotted cured resin part (A)>
The present laminated film is provided with a dotted cured resin portion (A) having a plurality of convex portions scattered at intervals on at least one side surface of the present base film, and a cured resin layer is further provided on these surface sides. It is a laminated film having a configuration including (B).
When the surface of the laminated film is formed only by the cured resin layer (B), it cannot withstand deformation when external force is applied to the laminated film, causing damage to the laminated film surface or irreversible craze. Occur. On the other hand, the present laminated film can avoid stress concentration due to the presence of the dotted cured resin portion (A). Furthermore, the external force can be absorbed by the deformation of the dotted cured resin portion (A). Therefore, a laminated film having excellent repeated bending properties can be obtained.

The interspersed cured resin part (A) refers to a set of a plurality of convex parts provided on at least one surface of the present base material film.
The dotted cured resin portion (A) is preferably a set of convex portions made of a cured resin, that is, a resin having a crosslinked structure, and made of a resin softer than the cured resin layer (B), as described later. The details of the composition and forming method of such a resin will be described later.

The convex portion forming the dotted cured resin portion (A) may have a cross-sectional shape of, for example, an arc shape, a triangular shape, a quadrangular shape, or any other shape, and among them, the arc shape is preferable. At this time, all the convex portions may or may not have the same sectional shape. By optimizing the cross-sectional shape of the convex portion in this way, it may be possible to have excellent repeated bending characteristics.
Further, the plan view shape of the convex portion may be, for example, a circular shape, an elliptical shape, a triangular shape, a quadrangular shape, another polygonal shape, or any other arbitrary shape, among which the circular shape or the elliptical shape is preferable. Is preferred. At this time, all the convex portions may or may not have the same plan view shape. By optimizing the plan view shape of the convex portion in this manner, it may be possible to have excellent repeated bending characteristics.
The convex portions may be regularly arranged in the vertical and horizontal directions, for example, in a grid pattern, may be regularly arranged in a concentric circle pattern, may be regularly arranged, or may be randomly arranged. You may.

The height of the convex portion is preferably 1 μm or more and 30 μm or less. If it is 1 μm or more, for example, when the dotted cured resin layer (A) is cured by irradiation with ultraviolet rays, insufficient curing due to oxygen inhibition or the like can be prevented. On the other hand, when it is 30 μm or less, it becomes easy to secure the surface smoothness of the present laminated film, and it becomes easy to secure the transparency. From this viewpoint, the height of the convex portion is preferably 1 μm or more and 30 μm or less, more preferably 20 μm or less, and further preferably 10 μm or less. Here, the height of the convex portion includes any meaning of the height of any one convex portion and the average value of the heights of a plurality of convex portions.
When forming the protrusions by the inkjet method, as a specific means for adjusting the height of the protrusions, for example, a method of adjusting the solid content concentration, the viscosity or the like can be mentioned. However, it is not limited to this.

The pitch between the convex portions means a distance from the convex portion to another convex portion existing closest to the arbitrary convex portion as a reference, and means an average value thereof. However, as described above, the convex portions may be randomly arranged or may be regularly arranged.
For example, when they are arranged in a vertical and horizontal lattice pattern, the pitch between the convex portions, that is, the distance between the centers of the convex portions is λx of the pitch in the X direction and the Y direction (perpendicular to the X direction as shown in FIG. It is preferable that all pitches λy in the (direction) are 100 μm or more and 500 μm or less. If the pitch is 100 μm or more, it is easy to maintain the independence or discontinuity of each convex portion, and if it is 500 μm or less, it is easy to ensure transparency.
From this point of view, the pitch between the convex portions is preferably 100 μm or more and 500 μm or less, both of the pitch λx in the X direction and the pitch λy in the Y direction, more preferably 400 μm or less, and further preferably 300 μm or less. preferable.

The coverage of the dotted cured resin portion (A), that is, the ratio of the area occupied by the dotted cured resin portion (A) to the film area (one surface) of the base film when the film is viewed in plan is from 10 to 90. % Is preferred.
If the coverage of the interspersed cured resin part (A) is 10% or more, the flexibility can be improved, and if it is 90% or less, the decrease in the surface hardness can be suppressed and the flexibility can be improved. Therefore, it is preferable.
From this viewpoint, the coverage of the interspersed cured resin portion (A) is preferably 10% or more and 90% or less, more preferably 15% or more or 85% or less, and even more preferably 20% or more or 80% or less. More preferable.

The density of the interspersed cured resin portion (A), that is, the number of convex portions present per unit area 1 cm ² of the film surface of the substrate film when the film is viewed in plan is 100 or more and 1×10 ⁶ or less. preferable.
When the density (pieces/cm ² ) of the dotted cured resin portion (A) is 100 or more, the smoothness of the surface of the laminated film is improved, and the independence or discontinuity of each convex portion can be maintained. It is easy, and if it is 1×10 ⁶ or less, a decrease in hardness can be prevented, which is preferable.
From this viewpoint, the density (pieces/cm ² ) of the interspersed cured resin part (A) is preferably 100 or more and 1×10 ⁶ or less, and more preferably 200 or more or 7×10 ⁵ or less, and among them 300 or more or 5 It is more preferable that it is not more than ×10 ⁵ .

In addition, the size of each convex portion (area of the convex portion when viewed in plan) is preferably 1 μm or more and 1000 μm or less in terms of a radius r equivalent to a circle, and 1 μm or more or 500 μm or less, Among them, it is more preferably 1 μm or more or 200 μm or less.

The dotted cured resin part (A) is preferably transparent in consideration of optical use.

<Cured resin layer (B)>
The cured resin layer (B) is a resin layer that covers the dotted cured resin portion (A).
Above all, it is preferable that the cured resin layer (B) fill the gaps between the convex portions of the dotted cured resin portion (A) and have a flat surface.

The cured resin layer (B) is preferably made of a cured resin, in other words, a resin having a crosslinked structure, and a resin harder than the interspersed cured resin portion (A).
More specifically, from the viewpoint of satisfying both the hardness of the film surface and the repeated bending property at a high level, regarding the elastic modulus measured by a micro hardness meter measurement (JIS Z 2255), the dotted cured resin part (A) The elastic modulus relationship between the cured resin layer (B) and the cured resin layer (B) is preferably: interspersed cured resin portion (A)<cured resin layer (B).
Above all, the difference in elastic modulus between the dotted cured resin portion (A) and the cured resin layer (B) is 50 MPa or more (that is, the elastic modulus of the cured resin layer (B)-the elastic modulus of the dotted cured resin portion (A)). >50 (MPa)), preferably 100 MPa or more or 500 MPa or less, and more preferably 200 MPa or more or 400 MPa or less.

The elastic modulus of the cured resin layer (B) measured by a micro hardness tester (JIS Z 2255) is preferably 100 MPa or more and 900 MPa or less, and more preferably 200 MPa or more or 800 MPa or less, and 300 MPa or more or 700 MPa or less. It is more preferable that there is.
Examples of the method for adjusting the elastic moduli of the dotted cured resin portion (A) and the cured resin layer (B) include a method for optimizing the material selection and composition of the curable composition described later. Specifically, a method of optimizing the selection of the curable monomer, the composition ratio of the curable monomer, the content ratio of the crosslinkable monomer and the like can be mentioned.

Regarding the layer thickness of the cured resin layer (B), in the relation between the convex portion height H _A of the scattered cured resin portion (A) and the layer thickness H _B of the cured resin layer (B), 2×H _A ≧ It is preferable to satisfy H _B. At this time, both the height H _{A of the} convex portion and the layer thickness H _B are the height after curing and drying when forming the convex portion of the dotted cured resin portion (A) or the cured resin layer (B). Is.
If 2×H _A ≧H _B is satisfied, the surface hardness can be increased.
Furthermore, if 3/2×H _A ≧H _B is satisfied, excellent repeated bending properties can be obtained, which is more preferable.
From the same viewpoint, it is more preferable to satisfy 5/4×H _A ≧H _B, and it is further preferable to satisfy H _A ≦H _B.

The layer thickness of the cured resin layer (B) is preferably 1 μm or more and 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. When calculating the layer thickness of the cured resin layer (B), the average thickness including the interspersed cured resin portion (A) is calculated.

Considering optical applications, the cured resin layer (B) is preferably transparent.
Above all, in order to improve the visibility at a high level, it is preferable that the difference in refractive index between the dotted cured resin portion (A) and the cured resin layer (B) is 0.15 or less.
When the difference in refractive index between the dotted cured resin portion (A) and the cured resin layer (B) is 0.15 or less, it becomes difficult to visually recognize the convex portion of the dotted cured resin portion (A) from the outside, and the visibility is improved. Can be increased. Specifically, when visually observed from an angle of 45 degrees oblique to the film surface, the contour derived from the interspersed cured resin portion (A) becomes difficult to see.
From this viewpoint, the difference in refractive index between the dotted cured resin portion (A) and the cured resin layer (B) is preferably 0.15 or less, more preferably 0.12 or less, and most preferably 0.10 or less. More preferable. The lower limit of the refractive index difference is 0.

<<Manufacturing method of the present laminated film>>
Each of the interspersed cured resin portion (A) and the cured resin layer (B) can be formed by curing a curable composition, that is, a composition having the capability of being cured.
More specifically, after the curable composition is applied to at least one surface of the base film and cured to form the interspersed cured resin part (A), the curable composition is applied thereon. Then, the present laminated film can be produced by curing and then forming the cured resin layer (B). At this time, the dotted cured resin portion (A) and the cured resin layer (B) may be simultaneously cured.
However, the method for producing the present laminated film is not limited to this method.

<Curable composition>
The curable composition for forming the interspersed cured resin part (A) and the cured resin layer (B) includes a curable monomer and, if necessary, a photopolymerization initiator, a solvent, particles, and a crosslinking agent. , And other components are preferably contained. Each will be described below.

<Curable monomer>
The curable monomer may be any compound that can be cured. Among these, from the viewpoint of achieving both excellent surface hardness and repetitive bendability, those containing a mixture of two or more selected from the group consisting of crosslinkable monomers, acrylic acid esters, and methacrylic acid esters are preferable. ..
Among them, from the viewpoints of handleability, industrial availability, and cost, it is a co-mixture of at least two kinds selected from crosslinkable monomers and (meth)acrylic acid esters, Alternatively, the mixture is preferably a mixture of at least two kinds selected from methacrylic acid esters and vinyl monomers.
As described above, when two types of monomers (a/b) are used, the compounding ratio (a/b) is preferably in the range of 90/10 to 10/90 by mass ratio, and more preferably , 80/20 to 40/60, and particularly 70/30 to 40/60.

From these mixtures, it is preferable to select each main component so that each of the dotted cured resin portion (A) and the cured resin layer (B) can satisfy at least the elastic modulus and the refractive index described above.
Among them, the curable monomer used in the curable composition for forming the interspersed cured resin portion (A) makes it possible to satisfy the elastic modulus and the refractive index described above, and at the same time, to form the convex portion by an inkjet method. It is preferably selected so that it can be formed.
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 elastic modulus and the refractive index described above.

(Crosslinkable monomer)
The crosslinkable monomer refers to a monomer having two or more polymerizable functional groups in one molecule.
Examples of the crosslinkable monomer include allyl acrylate, allyl methacrylate, 1-acryloxy-3-butene, 1-methacryloxy-3-butene, 1,2-diacryloxy-ethane, 1,2-dimethacryloxy-ethane, 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 Glycol dimethacrylate, polyethylene glycol diacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, triethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1.9-nonanediol diacrylate , Divinylbenzene, 1,4-pentadiene, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate and the like. These may be used alone or in combination of two or more.

(Acrylic acid esters)
Examples of the acrylates 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; cycloalkyl acrylates such as cyclohexyl acrylate and isobornyl acrylate; Examples thereof include 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, glycidyl acrylate, and the like.

(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, methacrylic acid. Acrylic acid, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, pentadecyl methacrylate, dodecyl methacrylate and other acyclic alkyl methacrylate esters; cyclohexyl methacrylate and isobornyl methacrylate cyclic alkyl esters; Examples thereof include methacrylic acid aryl esters such as phenyl methacrylate and 2-hydroxyethyl methacrylate, 2-methoxyethyl methacrylate, methacrylic acid acyclic alkyl esters having functional groups such as glycidyl methacrylate, and the like. These may be used alone or in combination of two or more.

(Photopolymerization initiator)
When the above 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 photopolymerization initiator and an amine 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-methylproton. Piophenone, 2-hydroxy-2-methyl-4'-isopropylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, isopropyl benzoin ether, isobutyl benzoin ether, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2- Phenylacetophenone, camphorquinone, benzanthrone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl) -Butanone-1,4-dimethylaminobenzoic acid ethyl ester, 4-dimethylaminobenzoic acid 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-[p-N,N-di(ethoxycarbonylmethyl)]-2,6-di(trichloro 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′-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-dimethylaminopropionyl)carbazole, 3,6-bis(2-methyl-2-morpholinopropionyl)-9- n-dodecylcarbazole, 1-hydroxycyclohexyl phenyl ketone, bis(η5-2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl) Examples include titanium, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide. These photopolymerization initiators may be used alone or in combination of two or more.

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

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.
When the content of the photopolymerization initiator is 1 part by mass or more, the desired polymerization initiation effect is obtained, and when the content of the photopolymerization initiator is 10 parts by mass or less, the yellowing of the resin layer occurs. Can be suppressed. The photocuring initiator and the 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-based 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, Examples thereof include ester solvents such as butyl lactate; organic solvents such as hydrocarbon solvents such as toluene, xylene, solvent naphtha, hexane, cyclohexane, ethylcyclohexane, methylcyclohexane, heptane, octane and decane. These organic solvents may be used alone or in combination of two or more kinds.

(particle)
The curable composition may contain particles for improving slipperiness and blocking.
Examples of the particles include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, inorganic particles such as titanium oxide, acrylic resin, styrene resin, urea resin, phenol resin, Examples thereof include organic particles such as epoxy resin and benzoguanamine resin. These may be used alone or in combination of two or more.

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

The oxazoline compound used for the cross-linking agent is a compound having an oxazoline group in the molecule, particularly preferably a polymer containing an oxazoline group, and is prepared by polymerization of an addition-polymerizable oxazoline group-containing monomer alone or with another monomer. be able to.
As the addition-polymerizable oxazoline group-containing monomer, 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 and the like can be mentioned, and one kind or a mixture of two or more kinds thereof can be used. .. Of these, 2-isopropenyl-2-oxazoline is industrially easily available and suitable.
The above-mentioned other monomer is not limited as long as it is a monomer copolymerizable with the addition-polymerizable oxazoline group-containing monomer, and examples thereof include alkyl (meth)acrylate (wherein the alkyl group is a methyl group, an ethyl group, an n-propyl group, an isopropyl group). Group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group) and the like (meth)acrylic acid esters; acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid , Styrene sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.) and the like; unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth)acrylamide, N- Alkyl (meth)acrylamide, N,N-dialkyl (meth)acrylamide, (as the alkyl group, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2 -Ethylhexyl group, cyclohexyl group, etc.), unsaturated amides; vinyl acetates 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; Examples thereof include halogen-containing α,β-unsaturated monomers such as vinylidene chloride; α,β-unsaturated aromatic monomers such as styrene and α-methylstyrene. One or more of these monomers can be used. Can be used.

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

The above-mentioned isocyanate compound used for the cross-linking agent is a compound having an isocyanate derivative structure represented by, for example, isocyanate or blocked isocyanate.
Examples of the isocyanate include an aromatic isocyanate such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, and an aromatic ring such as α,α,α′,α′-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylenebis(4-cyclohexyl isocyanate), isopropylidene dicyclohexyl diisocyanate, etc. The alicyclic isocyanates and the like can be exemplified. Further, polymers and derivatives of these isocyanates such as burettes, isocyanurates, uretdiones, and carbodiimide modified products are also included. These may be used alone or in combination of two or more. Among the above-mentioned isocyanates, an aliphatic isocyanate or an alicyclic isocyanate is preferable as a measure against yellowing due to ultraviolet irradiation.

When used in a blocked isocyanate state, examples of the blocking agent include bisulfites, phenolic compounds such as phenol, cresol and ethylphenol, propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, alcohols such as methanol and ethanol. Compounds, methyl isobutanoyl acetate, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, active methylene compounds such as acetylacetone, mercaptan compounds such as butyl mercaptan, dodecyl mercaptan, ε-caprolactam, δ-valerolactam, etc. Lactam compounds, diphenylaniline, aniline, ethyleneimine and other amine compounds, acetanilide, acetic acid amide acid amide compounds, formaldehyde, acetoaldoxime, acetone oxime, methyl ethyl ketone oxime, cyclohexanone oxime and other oxime compounds. These may 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 combined product with various polymers. From the viewpoint of improving the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or combination of polyester resin and urethane resin.

The above-mentioned epoxy compound used for the cross-linking agent is a compound having an epoxy group in the molecule, for example, a condensate of epichlorohydrin with a hydroxyl group or an amino group such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin, and 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, triglycidyl tris(2-hydroxyethyl)isocyanate, glycerol polyglycidyl ether, trimethylolpropane. Examples of the polyglycidyl ether and 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, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, glycidyl amine compounds N, N, N', N Examples thereof include'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N-diglycidylamino)cyclohexane. From the viewpoint of improving adhesiveness, a polyether-based epoxy compound is preferable. Moreover, as the amount of the epoxy group, a polyepoxy compound having a polyfunctionality of three or more functional groups is preferable to a bifunctional one.

The melamine compound used in the cross-linking agent is a compound having a melamine skeleton in the compound, for example, an alkylolated melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative. , And mixtures 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. The melamine compound may be a monomer, a dimer or higher polymer, or a mixture thereof. Further, a catalyst in which urea or the like is co-condensed with a part of melamine, and a catalyst can be used together for improving the reactivity of the melamine compound.

The content of the cross-linking agent is preferably 10 parts by mass or more based on 100 parts by mass of the curable monomer, and more preferably 20 parts by mass or more, and particularly 25 parts by mass, from the viewpoint of obtaining good coating 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 even more preferably 40 parts by mass or less.

(Carbodiimide compound)
The carbodiimide compound used for the 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 compound having two or more molecules in the molecule is more preferable for better adhesion.
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 of aromatic series and aliphatic series can be used. Specifically, tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, Hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, dicyclohexylmethane diisocyanate and the like can be mentioned.

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 particularly 250 or more or 800 or less, Among them, it is more preferably 300 or more or 700 or less. Use of the above range improves the durability of the coating film.

(Other ingredients)
In order not to impair the gist of the present invention, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound, by adding a surfactant, polyalkylene oxide, quaternary ammonium salt of dialkylamino alcohol, hydroxyalkyl It is possible to add a hydrophilic monomer such as a sulfonate as appropriate.

When such a cross-linking component is contained, a component for promoting cross-linking, such as a cross-linking catalyst, can be used together.

<Curable composition for forming dotted cured resin part (A)>
The curable composition for forming the interspersed cured resin part (A) is preferably applied by an inkjet method, and therefore, in the state of an inkjet ink, that is, in a liquid state, measured at 25° C. with an E-type viscometer. The viscosity is preferably 10 to 60 mPa·s, more preferably 30 mPa·s or less, even more preferably 20 mPa·s or less, even more preferably 15 mPa·s or less, and even more preferably 12 mPa·s or less.
It is also possible to apply the ink having a higher viscosity by heating the head portion of the inkjet. In this case, the viscosity (standard) is 10 to 70 mPa·s, more preferably 10 to 60 mPa·s, and even more preferably 10 to 50 mPa·s.

<Method of forming dotted cured resin portion (A)>
The dotted cured resin portion (A) is preferably formed by applying a curable composition using an inkjet printing method and then curing the composition by irradiating it with light, for example, ultraviolet rays.
By applying using an inkjet printing method, it is possible to apply a predetermined pattern shape with high accuracy. Therefore, the shape, size, forming density, coverage, and the like of the convex portions that form the dotted cured resin portion (A) can be appropriately adjusted. Above all, compared with gravure printing or the like, it is possible to reduce the size of the convex portions and form them with a high density, and it is possible to further enhance the repetitive bendability. Moreover, since the resin composition can be applied only to the necessary portions, the amount used can be minimized, which can contribute to the improvement in productivity.

When applying using an inkjet printing method, it is preferable to adjust the viscosity, specific gravity, conductivity, and surface tension of the curable composition in order to prevent clogging of the ejection port (jet head).

Examples of the inkjet coating method include a method of applying mechanical energy to the ink to eject (apply) the ink from an inkjet head (so-called piezo method), and a coating method of applying thermal energy to the ink to apply the ink. (So-called bubble jet (registered trademark) method) and the like can be mentioned.

In the case of irradiating ultraviolet rays, the amount of ultraviolet irradiation will depend on the composition of the ink, preferably 50~1,000mJ / cm ² in accumulated light quantity, among others 100 mJ / cm ² or more, or 800 mJ / cm ² or less, among them, even more preferably 200 mJ / cm ² or more, or 600 mJ / cm ² or less.

<Method for forming cured resin layer (B)>
As a method of providing the cured resin layer (B), a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, and inkjet can be used.

<Physical properties of the 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 2H or more, and particularly 3H or more.

(Repeatability)
The present laminated film having the above-mentioned structure is provided with a dotted cured resin portion (A) in which a plurality of convex portions are scattered at intervals on the surface of the present base film, and the dotted cured resin portion is further provided. By setting the elastic modulus of (A) to be lower than the elastic modulus of the cured resin layer (B), it was possible to further improve the practical repeating characteristics.
Therefore, the laminated film of the present invention has a durability such that cracks do not occur even after being repeatedly bent 100,000 times, particularly 150,000 times or more, and 200,000 times or more, in repeated bending property evaluation (R=2.5 condition). Can be obtained.

(Film haze)
When the present laminated film is supposed to be applied to optical use, the film haze is preferably 5% or less, more preferably 4% or less, and particularly preferably 3% or less.

<<Applications of this laminated film>>
This laminated film has excellent surface hardness and practical repetitive foldability, and since it is also possible to obtain transparency, it is a surface protective film, especially a surface protective film for displays, and among them, flexible. It can be suitably used as a surface protective film for a display. However, the use of the present laminated film is not limited to these uses.

<<Explanation of terms>>
In the present invention, the term "film" includes a "sheet", and the term "sheet" includes a "film".

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

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 methods and evaluation methods used in the present invention are as follows.

(1) Height of convex portion of dotted cured resin part (A) Non-contact surface/layer cross-section shape measuring system "Vert Scan" manufactured by Mitsubishi Chemical System Co., Ltd.
The measurement was performed using the model R5500GML-M100 under the following measurement conditions.
(Measurement condition)
Magnification: 5 times Field of view: 950 μm x 710 μm in plane direction, 8 μm in height direction

(2) Method of measuring film thickness of cured resin layer (B) The surface of the cured resin layer (B) was dyed with RuO ₄ and embedded in an epoxy resin. Then, the section prepared by the ultrathin section method was again stained with RuO _4, and the cross section of the cured resin layer (B) was measured using a transmission electron microscope (H-7650 manufactured by Hitachi, acceleration voltage 100 kV).

(3) Film haze (transparency)
According to JIS K 7136, the film haze of each film was measured using a haze meter HM-150 manufactured by Murakami Color Research Laboratory.
(Criteria)
A (good): 3% or less B (poor): Over 3% and 5% or less

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

(5) Repeated Bending Property A bending tester (DLDMLH-FS manufactured by Yuasa System Equipment Co., Ltd.) was used to perform a test so that the resin layer (hard coat layer) of the sample film would be the outer surface, and the cured resin The presence or absence of cracks in the layer (B) was visually confirmed.
Then, the number of repeated bendings was measured together with the minimum radius (R) at which cracks did not occur, and based on the result, it was judged according to the following judgment criteria.
(Criteria)
A (good): R=2.0 or less, and the number of repeated foldings is 200,000.
B (little good): R=2.0 or more, the number of repeated folding is 10,000 or more and less than 200,000 C(poor): R=2.0 or more, or the number of repeated folding is 10,000. Less than.

(6) Coverage of interspersed cured resin portion (A) As shown in FIG. 3, when the interspersed cured resin portion (A) is viewed in plan, the center between adjacent convex portions ((A) in FIG. 3) The distance (pitch) is λ [m], the diameter of each convex portion is 2r [m], the area of the unit cell and the area of the convex portion in the unit cell shown in FIG. 3 are obtained, and the covered area is calculated by the following formula. The rate q (%), that is, the ratio (%) of the area occupied by the interspersed cured resin part (A) to the film area (one surface) of the substrate film was calculated.
Area of unit cell S ₁ =x ²
Area of resin part (A) in unit cell S ₂ =πr ²
Covering area ratio q=S ₂ /S ₁ =πx ² /λ ²

(7) Elastic Modulus of Dotted Cured Resin Part (A) and Cured Resin Layer (B) The elastic modulus was determined by a dynamic ultra-micro hardness meter (DUH-W201, manufactured by Shimadzu Corporation).

(8) The refractive index was obtained by measuring the refractive index Abbe of the dotted cured resin portion (A) and the cured resin layer (B). It judged based on the result based on the following criteria.
(Criteria)
A (good): The difference in refractive index between the dotted cured resin portion (A) and the cured resin layer (B) is 0.15 or less.
B (poor): The difference in refractive index between the dotted cured resin portion (A) and the cured resin layer (B) exceeded 0.15.

(9) Comprehensive Evaluation Each laminated film obtained in Examples and Comparative Examples was evaluated according to the following evaluation criteria.
(Criteria)
A (good): Transparency, hard coat property, repetitive bending property, and refractive index difference between the dotted cured resin portion (A) and the cured resin layer (B) are all A.
B (little good): transparency, hard coat property, repetitive bending property, and refractive index difference between the dotted cured resin portion (A) and the cured resin layer (B), at least one is B, and the rest Is A.
C (poor): transparency, hard coat property, repetitive bending property, and at least hard coat property and repetitive bending property for each item of refractive index difference between the dotted cured resin portion (A) and the cured resin layer (B). One of them is C, and the rest is A or B.

Various materials used in 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)

<Base film F2>
Teijin: polyethylene naphthalate biaxially stretched film (grade name "Teonex W51", thickness: 50 μm)

<Base film F3>
Kolon: Polyimide film (Product name: (C60)) Thickness: 50 μm

[Example 1]
The curable composition a prepared as described below was formed on the base film F2 in a circular shape having a diameter of 120 μm when viewed in a plan view using an inkjet device (DMP-2850 manufactured by FUJIFILM Corporation). The dots were applied at 25° C. so that the application amount (after drying) was 0.5 g/m ² so as to form a pattern in which dots were arranged at a pitch of 250 μm in the X direction and 250 μm in the Y direction, and dried. After that, ultraviolet rays having an integrated light amount of 400 mJ/cm ² were irradiated to provide the dotted cured resin portion (A).
Next, the curable composition b prepared as described below is applied with a bar coater so as to fill the spaces between the convex portions of the dotted cured resin portion (A) and cover the dotted cured resin portion (A), After being dried by heating at 90° C. for 1 min, the cured resin layer (B) was formed by irradiating with an integrated light amount of ultraviolet rays of 400 mJ/cm ² to obtain a laminated film.

(Curable composition a)
30 parts by mass of tertiary butyl acrylate (TBA) and 70 parts by mass of polyethylene glycol diacrylate (PEGDA) were mixed, and 10 parts by mass of a photopolymerization initiator was added thereto to prepare a curable composition a. The dotted cured resin portion (A) had a refractive index of 1.45.

(Curable composition b)
A curable composition b was prepared by adding 5 parts by mass of a photopolymerization initiator to 100 parts by mass of acrylate (Yupimer UV “HH2100” manufactured by Mitsubishi Chemical Corporation). The refractive index of the cured resin layer (B) was 1.54.

[Example 2]
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 F1.

[Example 3]
Example 1 except that the height of the convex portion of the dotted cured resin portion (A) was changed by adjusting the inkjet coating conditions (the number of scans for printing was changed from 5 times to 3 times). A laminated film was obtained in the same manner as in.

[Example 4]
A laminated film was obtained in the same manner as in Example 1, except that the curable composition b constituting the cured resin layer (B) was changed to the following curable composition a2.

(Curable composition a2)
60 parts by mass of pentaerythritol triacrylate, 30 parts by mass of trimethylolpropane triacryacrylate, and 10 parts by mass of dimethyloltricyclodecanediacrylate were mixed, and 5 parts by mass of a photopolymerization initiator was added thereto to prepare a curable composition a2. Was prepared. The refractive index of the dotted cured resin portion (A) was 1.50.

[Example 5]
A laminated film was obtained in the same manner as in Example 1 except that the pitch between the convex portions in the dotted cured resin portion (A) was changed as shown in Table 1.

[Example 6]
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 was applied onto the base film F2 with a bar coater, dried by heating at 90° C. for 1 min, and then irradiated with ultraviolet rays of 400 mJ/cm ^{2 in} integrated light quantity. Then, a cured resin layer (A) was formed to obtain a laminated film having a thickness (after drying) of 10 μm. At this time, the cured resin part (B) was not formed.
In Comparative Example 1, the dotted cured resin portion (A) composed of a plurality of convex portions was not formed, so that the dotted cured resin portion (A) of Comparative Example 1 shown in Table 2 had a uniform thickness. The above means the cured resin layer (A), and the height of the convex portion means the layer thickness of the cured resin layer (A).

[Comparative Example 2]
As in Example 1, the curable composition b was applied onto the base film F2 with a bar coater, dried by heating at 90° C. for 1 min, and then irradiated with ultraviolet rays of 400 mJ/cm ^{2 in} integrated light quantity. Thus, a cured resin layer (B) was formed to obtain a laminated film having a thickness (after drying) of 10 μm. At this time, the dotted cured resin portion (A) was not formed.

[Comparative Example 3]
On the base film F2, when the curable composition a2 prepared as described below was viewed in a plane using a screen printing machine (manufactured by Ranas Industry Co., Ltd., model FA-1V), circular dots having a diameter of 120 μm were formed. , To form a pattern in which the pitch is 250 μm in the X direction and 250 μm in the Y direction so that the coating amount (after drying) is 0.5 g/m ² at 25° C. Ultraviolet rays of 400 mJ/cm ² were irradiated to provide the dotted cured resin portion (A).
Next, the curable composition a prepared in the same manner as in Example 1 was filled with a bar coater so as to fill the spaces between the convex portions of the dotted cured resin portion (A) and cover the dotted cured resin portion (A). The coating was applied, and the cured resin layer (B) was formed by irradiating with ultraviolet rays of 400 mJ/cm ² in integrated light quantity to obtain a laminated film.

(Curable composition a2)
60 parts by mass of pentaerythritol triacrylate, 30 parts by mass of trimethylolpropane triacryacrylate, and 10 parts by mass of dimethyloltricyclodecanediacrylate were mixed, and 5 parts by mass of a photopolymerization initiator was added thereto to prepare a curable composition a2. Was prepared. The refractive index of the dotted cured resin portion (A) was 1.50.

[Comparative Example 4]
The curable composition a was applied onto the base film F2 so that the thickness (after drying) was 5 μm, dried and cured in the same manner as in Comparative Example 1 to form the first layer, and then the curable composition a. Similarly to Comparative Example 2, b was applied, dried and cured to a thickness (after drying) of 5 μm to form a first layer, and a laminated film was obtained.
In Comparative Example 4, since the dotted cured resin portion (A) composed of a plurality of convex portions was not formed, the dotted cured resin portion (A) of Comparative Example 4 shown in Table 2 had a uniform thickness. And the height of the convex portion means the layer thickness of the first layer. Further, the cured resin layer (B) means the above-mentioned second layer.

[Comparative Example 5]
A circular dot having a diameter of 100 μm when the curable composition a2 prepared in the same manner as in Comparative Example 3 was planarly viewed on a base film F2 using a screen printing machine (Ranas Industry Co., Ltd., model FA-1V). Is applied at 25° C. so that the applied amount (after drying) is 0.5 g/m ² so as to form a pattern having a pitch of 180 μm in the X direction and 180 μm in the Y direction. At a temperature of 400 mJ/cm ² to irradiate the resin with the dotted cured resin portion (A).
Next, the curable composition b2 prepared as described below is applied with a bar coater so as to fill the spaces between the convex portions of the dotted cured resin portion (A) and cover the dotted cured resin portion (A), After drying by heating at 90° C. for 1 min, the cured resin layer (B) was formed by irradiating with an integrated light amount of ultraviolet rays of 400 mJ/cm ² to obtain a laminated film.

(Curable composition b2)
30 parts by mass of ditrimethylolpropane tetraacrylate and 20 parts by mass of pentaerythritol triacrylate were mixed, and 2.5 parts by mass of a photoinitiator and 30 parts of a solvent (ethyl acetate) were added to prepare a curable composition b2. The refractive index of the cured resin layer (B) was 1.51.

[Comparative Example 6]
A laminated film was obtained in the same manner as in Example 1, except that the thickness of the cured resin layer (B) was changed.

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

<Discussion>
From the above examples and the test results conducted by the inventor so far, when the laminated film having the constitution of the present invention is used, the surface hardness (for example, 3H or more in pencil hardness evaluation) and the repeated bendability (R =2.5, it is possible to be compatible with 200,000 bends).
The dotted cured resin portion (A) corresponding to the first layer is configured to have a plurality of convex portions scattered at intervals, and the height of the convex portions and the thickness of the cured resin layer (B) are adjusted. Therefore, it is presumed that, by making the structure discontinuous, it is possible to reduce the stress propagation to the inside of the cured resin layer (B), which is applied when the laminated film is bent. Therefore, in the conventional method (overall coating formulation), it is possible to use a resin component composed of an acrylic monomer, which has been difficult to use, and there is an advantage that flexibility in designing a laminated film increases. Furthermore, since the two-layered structure of the dotted cured resin portion (A) and the cured resin layer (B) can be expected to disperse stress in the thickness direction, it is presumed that it is possible to contribute to further improvement in bending durability. It

Further, by setting the elastic modulus of the dotted cured resin portion (A) lower than that of the cured resin layer (B), the surface hardness (for example, 3H or higher in pencil hardness evaluation) is repeated at a high level. It was found that compatibility with the bendability (being able to bend 200,000 times under the condition of R=2.5) is possible. On the other hand, it has also been found that it is difficult to achieve both desired hard coat properties and repetitive bending properties by simply using the above-mentioned two-layer structure (Comparative Example 3).

It was also found that the use of the two-layer constitution of the resin layer of the present invention does not require an extremely large tensile elastic modulus of the substrate film 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, 3H or higher), a base film used is constructed as necessary. The tensile elastic modulus had to be further increased by reviewing the structural design of the raw material.
On the other hand, by using a two-layer structure of the dotted cured resin portion (A) and the cured resin layer (B) according to the present invention, it is possible to appropriately select a general-purpose substrate film distributed in the market. There is an advantage that the degree of freedom is increased in terms of selecting a base film.

Further, the present inventor notices that the contour of the convex portion may appear thin depending on the viewing angle when the resin layer surface is visually observed more severely when it is supposed to be applied to an optical use, and the countermeasure is also taken. is suggesting. That is, by setting the refractive index difference between the dotted cured resin portion (A) and the cured resin layer (B) to be 0.15 or less, the outline of the convex portion becomes invisible, and it is proposed that the visibility can be improved. There is.

The laminated film of the present invention has good hard coat properties (for example, 3H or more in pencil hardness evaluation) and repeated bendability (being able to bend 200,000 times under the condition of R=2.5) at a high level, and various surfaces. It can be used for protection. Among them, it can be suitably used for optical applications such as display members (surface protection film, etc.), which particularly require flexibility.

Claims (18)

On the surface of the base film, a plurality of convex portions are provided with a dotted cured resin portion (A) scattered at intervals, and a cured resin layer (B) covering the dotted resin portion (A) is provided. Is equipped with
The relationship between the height H _A of the convex portion of the dotted cured resin portion (A) and the layer thickness H _B of the cured resin layer (B) satisfies 2×H _A ≧H _B , and the micro hardness meter measurement is performed. Regarding the elastic modulus measured according to (JIS Z 2255), the relationship between the elastic modulus (MPa) between the dotted cured resin portion (A) and the cured resin layer (B) is the cured resin layer (B)-the dotted cured resin. Part (A)>50 (MPa) is satisfied, The laminated film characterized by the above-mentioned. The laminated film according to claim 1, wherein the surface of the cured resin layer (B) has a pencil hardness of 2H or more. The laminated film according to claim 1 or 2, which is capable of being folded 200,000 times or more in repeated bending property evaluation (R=2.5). The laminated film according to claim 1, which has a film haze of 5% or less. The laminated film according to any one of claims 1 to 4, wherein the base film has a tensile elastic modulus (JIS K 7161) of 2 GPa or more. The laminated film according to claim 1, wherein the base film is a polyester film. The laminated film according to claim 1, wherein the base film is a polyethylene naphthalate (PEN) film. The laminated film according to claim 1, wherein the base film is a polyethylene terephthalate (PET) film. The laminated film according to claim 1, wherein the base film is a polyimide film. The laminated film according to any one of claims 1 to 9, wherein a pitch between the convex portions of the dotted cured resin portion (A) is 100 µm to 500 µm. The laminated film according to any one of claims 1 to 10, wherein a difference in refractive index between the dotted cured resin portion (A) and the cured resin layer (B) is 0.15 or less. The projection height H _{A of the} dotted cured resin portion (A) and the layer thickness H _B of the cured resin layer (B) have a relationship of 3/2×H _A ≧H _B. The laminated film according to any one of 1. 13. The ratio of the area occupied by the interspersed cured resin portion (A) to the film area (one surface) of the substrate film when the film is viewed in plan is 10 to 90%, according to claim 1. Laminated film. The laminated film according to any one of claims 1 to 13, which is for surface protection. The laminated film according to any one of claims 1 to 14, which is for a display. It is a manufacturing method of the laminated film in any one of Claims 1-15, Comprising:
The dotted cured resin portion (A) is formed by applying a curable composition onto a base film by an inkjet method and curing the composition. The method for producing a laminated film according to claim 16, wherein the curable composition has a viscosity of 10 to 60 mPa·s in an inkjet ink state. It is a manufacturing method of the laminated film in any one of Claims 1-15, Comprising:
The dotted curable resin part (A) is characterized in that it is formed by applying a curable composition onto a substrate film and curing it, and the curable composition comprises a crosslinkable monomer and (meth)acrylic acid. A method for producing a laminated film, which comprises at least two kinds selected from esters.

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