JP7496309B2 - Laminated Film - Google Patents

Description

The present invention relates to a laminated film that has excellent substrate dependency and exhibits a consistent adhesive strength on a variety of substrates with different surface shapes, regardless of the shape of the substrate.

Products made of various materials such as synthetic resin, metal, and glass are sometimes handled with a protective sheet or film attached to their surface to prevent scratches and dirt that may occur during processing, transportation, or storage. Generally, a surface protection film is used in which an adhesive layer is formed on a supporting substrate made of thermoplastic resin or paper, and the adhesive layer surface is attached to the adherend.

Liquid crystal displays and touch panel devices have become increasingly popular in recent years, and these are made up of numerous optical sheets, optical films, and other components made of synthetic resin. Since it is necessary to minimize defects such as optical distortion in such optical components, surface protection films are often used to prevent scratches and dirt that can cause defects.

The properties of such a surface protection film are required to be such that it does not easily peel off from the substrate when subjected to environmental changes such as temperature and humidity or small stresses, that it does not leave any adhesive or adhesive components on the substrate when peeled off, and that it can be easily peeled off after processing or use.

Among the optical components mentioned above, there are a variety of surface shapes available on the market for adherends with uneven surfaces such as diffusion plates and prism sheets, and there is a demand for the development of a surface protection film that exhibits uniform adhesive strength on adherends with such different surface shapes and can be used for general purposes, that is, a surface protection film that is less dependent on the adherend.

With regard to surface protection films used on adherends having uneven surfaces, the technologies described in Patent Documents 1 and 2 can be cited.

JP 2007-253435 A JP 2013-117019 A

However, the technologies described in Patent Documents 1 and 2, which are surface protection films used on adherends having the aforementioned uneven surfaces, do not improve the difference in adhesive strength due to differences in the uneven shape of the adherend, i.e., the so-called adherend dependency.

The object of the present invention is to solve the above-mentioned problems by providing a laminated film that exhibits uniform adhesive strength to adherends with different surface shapes, can be used for general purposes, and has excellent adherend dependency.

The above problems can be solved by:

A laminated film having a substrate and a resin layer A on at least one side of the substrate, which satisfies the following (a), (b), and (c).

(a) The maximum probe tack value F at 23° C. on the resin layer A side is 0.2 g/mm ² or more and 2.5 g/mm ² or less.

(b) When a nanoindentation load-unloading test is performed on the resin layer A side at 26°C with a maximum load of 1 mN, the ratio (hp/hm) of the residual displacement hp (unit: μm) to the maximum displacement hm (unit: μm) is 0.50 or more and 0.90 or less.

(c) Resin layer A has a melting point Tm of 50°C or higher.

In view of the above-mentioned problems, the present invention provides a laminated film that is highly adherend-dependent and exhibits good adhesive properties for a variety of adherends having different surface shapes.

The following describes an embodiment of the present invention. However, the present invention is not limited to the embodiment described below.

The present invention is a laminated film having a substrate and a resin layer A on at least one side of the substrate. Here, the resin layer A is a layer containing at least a resin, which is disposed on at least one side of the substrate, and which satisfies the following (a), (b), and (c). The type of resin in the resin layer A is not particularly limited as long as it contains a resin, but it is preferable to select the resin in the resin layer A so that the laminated film satisfies the following (a), (b), and (c). The preferred embodiment of the resin contained in the resin layer A will be described later.

(a) The maximum probe tack value F at 23° C. on the resin layer A side is 0.2 g/mm ² or more and 2.5 g/mm ² or less.

(b) When a nanoindentation load-unloading test is performed on the resin layer A side at 26°C with a maximum load of 1 mN, the ratio (hp/hm) of the residual displacement hp (unit: μm) to the maximum displacement hm (unit: μm) is 0.50 or more and 0.90 or less.

(c) Resin layer A has a melting point Tm of 50°C or higher.

The laminated film of the present invention has a maximum probe tack value F at 23°C on the resin layer A side of 0.2 g/ ^mm2 or more and 2.5 g/ ^mm2 or less. The maximum probe tack value F is more preferably 0.3 g/ ^mm2 or more, and even more preferably 0.4 g/ ^mm2 or more. The maximum probe tack value F is more preferably 2.0 g/ ^mm2 or less, and even more preferably 1.5 g/ ^mm2 or less.

When the maximum probe tack value F on the resin layer A side is less than 0.2 g/ ^mm2 , sufficient adhesive strength may not be obtained when the laminate film of the present invention is used as a surface protection film. When the maximum probe tack value F on the resin layer A side is more than 2.5 g/ ^mm2 , the adhesive strength may become too large, and the adhesive strength may become too large, particularly for an adherend with a small surface roughness, resulting in excessive dependency on the adherend.

The maximum probe tack value F can be controlled by adjusting the material constituting the resin layer A described below and the flexibility, thickness, surface roughness, etc. of the resin layer A. For example, the maximum probe tack value F can be reduced and controlled to be 0.2 g/ ^mm2 or more and 2.5 g/ ^mm2 or less by a method of hardening the resin layer A, a method of reducing the thickness of the resin layer A, or a method of increasing the surface roughness of the resin layer A.

The laminated film of the present invention has a ratio (hp/hm, hereinafter referred to as hp/hm) of the residual displacement hp (unit: μm) to the maximum displacement hm (unit: μm) when a load-unloading test is performed on the resin layer A side at 26°C with a maximum load of 1 mN. The ratio is 0.50 or more and 0.90 or less. hp/hm is more preferably 0.60 or more, and even more preferably 0.70 or more. Furthermore, hp/hm is more preferably 0.80 or less.

If hp/hm is less than 0.50, when the resin layer A side of the laminated film of the present invention is bonded to an adherend, the resin layer A will have difficulty conforming to the unevenness of the adherend, and the adhesive strength may become too small, or the adhesive strength may become too small, particularly for adherends with large surface roughness, and the adhesive strength may become too dependent on the adherend. If hp/hm exceeds 0.90, the adhesive strength may become too large. hp/hm can be controlled by the material constituting the resin layer A described below.

The resin layer A in the laminated film of the present invention has a melting point Tm of 50°C or higher, and more preferably has a melting point Tm of 100°C or higher. In addition, when the resin layer A of the present invention has two or more melting points, the melting point on the higher side is taken as the melting point Tm of the resin layer A of the present invention. There is no particular upper limit for Tm, but it is preferably substantially 180°C or lower. When the Tm is less than 50°C or when the resin layer A does not have a melting point, the contact area between the resin layer A and the adherend increases after the laminated film of the present invention is laminated to the adherend and stored at high temperatures or over time, and the adhesive force may become too large. When the Tm exceeds 180°C, when the resin layer A is molded by melt extrusion, the viscosity may become too high, resulting in poor productivity.

One method for making resin layer A have a Tm of 50°C or higher is to add a crystalline resin having a melting point of 50°C or higher to the material constituting resin layer A. In other words, one method is to make resin layer A contain a crystalline resin having a melting point of 50°C or higher. A suitable crystalline resin for resin layer A is, for example, a crystalline olefin resin from the viewpoint of compatibility with other components used in resin layer A and productivity. Specific examples of olefin resins will be described later.

The above-mentioned maximum probe tack value F, hp/hm obtained by nanoindentation measurement, and melting point Tm of resin layer A can be measured by the method described in the examples.

The resin layer A of the present invention preferably has a storage modulus G'(A) at 50°C and 1 Hz of 1.5 MPa or more, more preferably 2.0 MPa or more, and even more preferably 2.5 MPa or more. There is no particular upper limit for the storage modulus G'(A), but from the viewpoint of adhesive properties such as stickiness, a value of 30 MPa is preferred.

It is preferable to set the storage modulus G'(A) of the resin layer A to 1.5 MPa or more in order to suppress an increase in the contact area between the resin layer A and the adherend and an increase in adhesive strength when the laminated film of the present invention is stored at high temperatures or over time after being laminated to the adherend. The storage modulus G'(A) of the resin layer A can be measured by the method described in the examples.

In addition, the storage modulus G'(A) of the resin layer A can be controlled by adjusting the material constituting the resin layer A. For example, methods for increasing the storage modulus G'(A) include, in an embodiment in which the resin layer A contains a styrene-based elastomer, further increasing the molecular weight of the styrene-based elastomer, using a crystalline resin having a melting point of 50°C or higher as the resin in the resin layer A, and using an unhydrogenated or partially hydrogenated aromatic copolymer or an aliphatic/aromatic copolymer as the resin in the resin layer A.

The arithmetic mean roughness Ra (A) of the resin layer A side of the present invention is preferably 0.20 μm or more, more preferably 0.30 μm or more, and particularly preferably 0.40 μm or more. The arithmetic mean roughness Ra (A) is preferably 0.80 μm or less, more preferably 0.70 μm or less, and particularly preferably 0.60 μm or less. It is preferable to set the arithmetic mean roughness Ra (A) to 0.20 μm or more in order to reduce the adherend dependency, and to suppress the increase in the contact area between the resin layer A and the adherend when the laminated film of the present invention is laminated to the adherend and stored at high temperatures or over time, and to suppress the increase in adhesive strength. The arithmetic mean roughness Ra (A) of the resin layer A side can be measured by the method described in the examples. The arithmetic mean roughness Ra (A) of the resin layer A side can be controlled, for example, by the material constituting the resin layer A described later, the material constituting the substrate, and the thickness of the resin layer A.

As described above, the laminated film of the present invention has a substrate and a resin layer A on at least one side of the substrate. Here, the resin layer A refers to a layer having a finite thickness, and preferably has adhesiveness at room temperature.

The resin layer A has adhesiveness means that when the resin layer A side of the laminated film is laminated to a SUS304 plate having an arithmetic mean roughness Ra of 0.2 μm and a ten-point mean roughness Rz of 2.8 μm using a roll press (special pressure roller manufactured by Yasuda Seiki Seisakusho Co., Ltd.) at a pasting pressure of 0.35 MPa, and then the adhesive strength between the resin layer A and the SUS304 plate is measured, the adhesive strength is 1 g/25 mm or more. The adhesive strength of the resin layer A is more preferably 2 g/25 mm or more, and even more preferably 5 g/25 mm or more. The higher the adhesive strength of the resin layer A, the better, and there is no particular upper limit, but if it exceeds 1000 g/25 mm, peeling after lamination becomes difficult and workability may decrease, so the upper limit is preferably about 1000 g/25 mm.

The position of the resin layer A is not particularly limited as long as it is disposed on at least one side of the substrate, but it is preferable that it is disposed on at least one outermost layer of the laminated film of the present invention. By disposing the adhesive resin layer A on the outermost layer of the laminated film, it becomes possible to attach the laminated film to an adherend via the resin layer A. In addition, since the resin layer A is not particularly limited as long as it is disposed on at least one side of the substrate, the substrate and the resin layer A may be disposed so as to be in direct contact with each other, or another layer such as an easy-adhesion layer may be provided between the substrate and the resin layer A.

The resin layer A is not particularly limited as long as it does not impair the effects of the present invention, and may include elastomers such as acrylic, silicone, natural rubber, and synthetic rubber. Among these, from the viewpoint of recyclability, it is preferable to use a thermoplastic synthetic rubber adhesive, and among these, a styrene elastomer is more preferable.

In the present invention, the styrene-based elastomer refers to a resin having a storage modulus G' (25) of 10 MPa or less at 25°C and 1 Hz, and containing at least a styrene component as a monomer component. Examples of styrene-based elastomers suitable for inclusion in the resin layer A include styrene-conjugated diene copolymers such as styrene-butadiene copolymer (SBR), styrene-isoprene-styrene copolymer (SIS), and styrene-butadiene-styrene copolymer (SBS), as well as hydrogenated products thereof (e.g., hydrogenated styrene-butadiene copolymer (HSBR), styrene-ethylenebutylene-styrene triblock copolymer (SEBS), and styrene-ethylenebutylene diblock copolymer (SEB)), and styrene-isobutylene copolymers (e.g., styrene-isobutylene-styrene triblock copolymer (SIBS), styrene-isobutylene diblock copolymer (SIB), or mixtures thereof). Among the above, styrene-conjugated diene copolymers such as styrene-butadiene-styrene copolymer (SBS) and hydrogenated products thereof, and styrene-isobutylene copolymers are preferably used. The styrene elastomers may be used alone or in combination of two or more kinds.

The content of the styrene-based elastomer suitably contained in the resin layer A in the resin layer A is preferably 40% by mass or more, and more preferably 50% by mass or more, when the entire resin layer A is taken as 100% by mass. The content of the styrene-based elastomer in the resin layer A is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 75% by mass or less. By setting the content of the styrene-based elastomer in the resin layer A within the above preferred range, good adhesive properties can be obtained when the laminated film of the present invention is used as an adhesive film.

The melt flow rate (MFR, measured under conditions of 230°C and 2.16 kg) of the styrene-based elastomer preferably contained in the resin layer A is preferably 3 g/10 min or more, more preferably 7 g/min or more, and even more preferably 10 g/10 min or more. The MFR of the styrene-based elastomer is preferably 50 g/10 min or less, more preferably 30 g/10 min or less, and even more preferably 20 g/10 min or less. By setting the MFR of the styrene-based elastomer suitable for the resin layer A within the above range, excellent productivity is achieved, and when the laminated film of the present invention is used as a surface protection film, good adhesion properties are exhibited.

In addition, the content of the styrene component in the styrene-based elastomer suitable for resin layer A is preferably 5% by mass or more, and more preferably 8% by mass or more, when the entire styrene-based elastomer is taken as 100% by mass. In addition, the content of the styrene component in the styrene-based elastomer is preferably 55% by mass or less, and more preferably 40% by mass or less. By setting the content of the styrene component in the styrene-based elastomer within the above range, when the laminated film of the present invention is bonded to an adherend, it exhibits good adhesion properties such as good adhesion and suppression of adhesive residue.

The resin layer A of the present invention preferably contains an olefin resin having a melt flow rate (MFR, measured under conditions of 230 ° C. and 2.16 kg) of 0.01 g / 10 min or more and 1.5 g / 10 min or less. By containing an olefin resin having an MFR of 0.01 g / 10 min or more and 1.5 g / 10 min or less, a structure is formed in which the olefin resin is dispersed as a domain component in the elastomer which is the matrix component of the resin layer A, and the arithmetic average roughness Ra (A) on the resin layer A side can be preferably controlled, and when the laminated film of the present invention is used as an adhesive film, it is possible to reduce the adherend dependency. The MFR of the olefin resin in the resin layer A is more preferably 0.1 g / 10 min or more, and more preferably 0.2 g / 10 min or more. In addition, the MFR of the olefin resin is more preferably 1.3 g / 10 min or less, and more preferably 1.0 g / 10 min or less. When the MFR is less than 0.01 g/10 min, the olefin resin may aggregate due to poor dispersion of the domain components, resulting in FE. On the other hand, when the MFR exceeds 1.5 g/10 min, the dispersibility of the domain components increases, making it difficult to adjust the arithmetic mean roughness Ra(A) of the resin layer A to the range specified in the present application. Examples of olefin-based resins that are preferably contained in the resin layer A include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, low-crystalline or amorphous ethylene-α-olefin copolymers, crystalline polypropylene, low-crystalline polypropylene, amorphous polypropylene, propylene-α-olefin copolymers, propylene-ethylene-α-olefin copolymers, polybutene, 4-methyl-1-pentene-α-olefin copolymers, ethylene-ethyl (meth)acrylate copolymers, ethylene-methyl (meth)acrylate copolymers, ethylene-n-butyl (meth)acrylate copolymers, and ethylene-vinyl acetate copolymers. Among the above, polypropylene-based resins such as crystalline polypropylene, low-crystalline polypropylene, amorphous polypropylene, propylene-α-olefin copolymers, and propylene-ethylene-α-olefin copolymers are preferably used. These olefin-based resins may be used alone or in combination. The α-olefin is not particularly limited as long as it is copolymerizable with ethylene, propylene, and 4-methyl-1-pentene, and examples thereof include ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-pentene, and 1-heptene. Among these, crystalline polypropylene is particularly preferable as the olefin-based resin in the resin layer A. The olefin-based resin referred to here may be one that corresponds to the olefin-based elastomer described below. On the other hand, the olefin-based resin referred to here does not include the above-mentioned styrene-based elastomer.

The content of the olefin resin in the resin layer A is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 10% by mass or more, when the entire resin layer A is 100% by mass. The content of the olefin resin in the resin layer A is preferably 35% by mass or less, more preferably 30% by mass or less, and particularly preferably 25% by mass or less. By setting the content of the olefin resin in the resin layer A within the above range, the arithmetic mean roughness Ra (A) on the resin layer A side can be preferably adjusted while ensuring good productivity, and thus, when the laminated film of the present invention is used as an adhesive film, the adhesion properties are further improved, such as the adherend dependency being reduced.

It is preferable that the resin layer A of the present invention contains an olefin-based elastomer. The olefin-based elastomer in the present invention refers to an olefin-based resin having a storage modulus G' (25) of 10 MPa or less at 25°C and 1 Hz, and/or an olefin-based resin having a tan δ (25) of 0.5 or more at 25°C and 1 Hz. In other words, since an olefin-based elastomer is an olefin-based resin having a certain storage modulus G' (25) or a certain tan δ (25), those that fall under the olefin-based elastomer also fall under the above-mentioned olefin-based resin. In addition, as mentioned above, olefin-based resins do not include styrene-based elastomers, so the olefin-based elastomers that are part of olefin-based resins do not include the above-mentioned styrene-based elastomers.

The resin layer A of the present invention preferably contains an olefin-based elastomer, and more preferably contains an olefin-based elastomer having a tan δ (25) of 0.5 or more, which is tan δ at 25°C and 1 Hz, among the above-mentioned olefin-based elastomers. The tan δ (25) of the above-mentioned olefin-based elastomer is more preferably 1.0 or more, and particularly preferably 1.5 or more. By containing the above-mentioned olefin-based elastomer in the resin layer A of the present invention, the above-mentioned maximum probe tack value F and the hp/hm obtained by nanoindentation on the resin layer A side can be preferably controlled.

Examples of olefin-based elastomers suitable for such resin layer A include amorphous polypropylene, low crystalline polypropylene, amorphous polybutene, 4-methyl-1-pentene/α-olefin copolymer, etc., with amorphous polypropylene and 4-methyl-1-pentene/α-olefin copolymer being preferred.

The content of the olefin-based elastomer in the resin layer A of the present invention is preferably 3% by mass or more, and more preferably 5% by mass or more, when the resin layer A is 100% by mass. The content of the olefin-based elastomer in the resin layer A is preferably 30% by mass or less, and more preferably 20% by mass. If the content of the olefin-based elastomer in the resin layer A exceeds 30% by mass, the adhesive strength to the adherend may become too low.

The resin layer A of the present invention preferably contains a tackifier in order to enhance adhesion to the adherend. As the tackifier, a known one for this application can be used, but for example, a petroleum resin such as an aliphatic copolymer, an aromatic copolymer, an aliphatic-aromatic copolymer, or an alicyclic copolymer, a terpene resin, a terpene phenol resin, a rosin resin, an alkylphenol resin, a xylene resin, or a hydrogenated product thereof, or the like, which is generally used for this application, can be used. The content of the tackifier is preferably 5% by mass or more, and more preferably 10% by mass or more, when the entire resin layer A is taken as 100% by mass. In addition, the content of the tackifier is preferably 40% by mass or less, and more preferably 30% by mass or less, when the entire resin layer A is taken as 100% by mass.

The resin layer A of the present invention preferably contains at least an aromatic copolymer or an aliphatic-aromatic copolymer among the above-mentioned tackifiers. The aromatic copolymer or the aliphatic-aromatic copolymer is preferably an unhydrogenated or partially hydrogenated aromatic copolymer or an unhydrogenated or partially hydrogenated aliphatic-aromatic copolymer. The term "partially hydrogenated" as used herein means that the hydrogenation rate is 1% by mass or more and less than 90% by mass, and the term "unhydrogenated" means that the hydrogenation rate is 0% by mass or more and less than 1% by mass. The hydrogenation rate of the partially hydrogenated aromatic copolymer or the partially hydrogenated aliphatic-aromatic copolymer is more preferably less than 80% by mass, even more preferably less than 70% by mass, and particularly preferably less than 50% by mass. By containing the unhydrogenated or partially hydrogenated aromatic copolymer or the unhydrogenated or partially hydrogenated aliphatic-aromatic copolymer, the value of the above-mentioned maximum probe tack F can be preferably controlled and the adherend dependency can be reduced. Incidentally, the unhydrogenated or partially hydrogenated aromatic copolymer and the unhydrogenated or partially hydrogenated aliphatic-aromatic copolymer can preferably be one having a softening point of 80° C. or higher. That is, it is particularly preferred that the resin layer A of the laminated film of the present invention contains an unhydrogenated or partially hydrogenated aromatic copolymer and/or an unhydrogenated or partially hydrogenated aliphatic-aromatic copolymer having a softening point of 80° C. or higher. The hydrogenation rate can be calculated by nuclear magnetic resonance spectrum ( ¹ H-NMR spectrum) measurement.

In addition, other components such as lubricants and other additives may be appropriately added to the resin layer A of the present invention in addition to those described above, as long as they do not impair the objectives of the present invention.

The lubricant used in the resin layer A of the present invention is added to the chip surface to prevent the chips from sticking or blocking when the styrene-based elastomer is chipped, to adjust the adhesive strength by precipitating on the surface of the resin layer A, or to obtain good extrudability when the resin layer A is melt-extruded. For example, fatty acid metal salts such as calcium stearate and magnesium behenate, fatty acid amides such as ethylene bisstearic acid amide and hexamethylene bisstearic acid amide, and waxes such as polyethylene wax, polypropylene wax, and paraffin wax can be mentioned. The content of the lubricant is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 3% by mass or less, when the entire resin layer A is taken as 100% by mass.

In addition, the other additives mentioned above include a crystal nucleating agent, an antioxidant, a heat resistance imparting agent, a weather resistance agent, an antistatic agent, etc. These additives may be used alone or in combination, but the total content is preferably 3% by mass or less, and more preferably 2% by mass or less, when the entire resin layer A is taken as 100% by mass.

In addition, the resin layer A of the present invention may contain particles for the purpose of controlling the arithmetic mean roughness Ra (A) of the resin layer A. For example, inorganic particles or organic particles can be used as the particles in the resin layer A, and organic particles that are less likely to damage the adherend when bonded to the adherend are preferable. Examples of organic particles include acrylic resin particles, styrene resin particles, polyolefin resin particles, polyester resin particles, polyurethane resin particles, polycarbonate resin particles, polyamide resin particles, silicone resin particles, fluorine resin particles, or copolymer resin particles of two or more monomers used in the synthesis of the above resins, and these may be used alone or in combination.

The average particle diameter of the particles in the resin layer A is preferably 0.1 μm or more, more preferably 1.0 μm or more, and even more preferably 2.0 μm or more, from the viewpoint of favorably controlling the arithmetic mean roughness Ra(A) and adhesive properties of the resin layer A. The average particle diameter of the particles in the resin layer A is preferably 20.0 μm or less, more preferably 15.0 μm or less, and particularly preferably 10.0 μm or less.

The thickness of the resin layer A of the present invention is preferably 1.0 μm or more, more preferably 2.0 μm or more, from the viewpoint of ensuring adhesion to the adherend. The thickness of the resin layer A is preferably 6.0 μm or less, more preferably 5.0 μm or less, and even more preferably 3.0 μm or less, from the viewpoint of reducing the adherend dependency and suppressing adhesion increase due to aging or heating after attachment to the adherend.

The laminated film of the present invention has a substrate. Here, the substrate refers to a layer having a finite thickness. The material of the substrate is not particularly limited, but for example, olefin-based resins or ester-based resins can be used, and from the viewpoint of productivity and processability, it is preferable to use an olefin-based resin as the main component. The main component referred to here refers to the component with the highest mass percentage (the component with the highest content) among all the components constituting the substrate.

Examples of olefin resins contained as a main component in the substrate include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, low-crystalline or non-crystalline ethylene-α-olefin copolymers, polypropylene, propylene-α-olefin copolymers, propylene-ethylene-α-olefin copolymers, ethylene-ethyl (meth)acrylate copolymers, ethylene-methyl (meth)acrylate copolymers, ethylene-n-butyl (meth)acrylate copolymers, and ethylene-vinyl acetate copolymers. Among these, polypropylene is particularly preferred. These may be used alone or in combination. The α-olefin is not particularly limited as long as it can be copolymerized with propylene or ethylene, and examples include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-pentene, and 1-heptene. The olefin resin referred to here may be one corresponding to the above-mentioned olefin elastomer. On the other hand, the olefin resin referred to here does not include the above-mentioned styrene elastomer.

Among the above olefin resins, in order to control the arithmetic mean roughness Ra(A) of the resin layer A within the desired range, it is preferable that the substrate also has a structure in which domain components are dispersed in the matrix resin, which is the main component. The above structure can be formed, for example, by using polypropylene as the main component of the substrate and adding an incompatible polyolefin to it, or by using a commercially available block polypropylene, a so-called block copolymer or impact copolymer.

The melt flow rate (MFR, measured under conditions of 230°C and 2.16 kg) of the resin used in the substrate of the present invention is preferably 0.5 g/10 min or more, more preferably 1 g/10 min or more, and even more preferably 2 g/10 min or more, from the viewpoints of productivity and stability when laminating with adjacent layers. In addition, from the same viewpoints as above, the MFR of the resin used in the substrate is preferably 30 g/10 min or less, more preferably 25 g/10 min or less, and even more preferably 20 g/10 min or less.

The substrate of the present invention preferably contains a styrene-based elastomer. That is, it is particularly preferable that the substrate of the laminated film of the present invention contains an olefin-based resin and a styrene-based elastomer. By containing a styrene-based elastomer in the substrate, when a styrene-based elastomer is used in the resin layer A, the affinity between the substrate and the resin layer A is improved, and the interfacial adhesion between the substrate and the resin layer A can be increased. When the entire substrate is taken as 100% by mass, the content of the styrene-based elastomer in the substrate is preferably 1% by mass or more, more preferably 2% by mass or more. In addition, the content of the styrene-based elastomer in the substrate is preferably 20% by mass or less, more preferably 10% by mass or less. In addition, the styrene-based elastomer used in the substrate of the present invention can be a known one, and for example, the same styrene-based elastomer as the styrene-based elastomer suitable for the resin layer A described above can be used.

One method for incorporating a styrene-based elastomer into the substrate of the present invention is, for example, to recover the laminate film containing a styrene-based elastomer in the resin layer A, add the recycled raw material, and use it as the substrate. This method is preferred from the standpoint of recycling the resin and reducing production costs.

In addition, various additives such as crystal nucleating agents, lubricants, antioxidants, weathering agents, antistatic agents, pigments, etc. may be appropriately added to the substrate of the present invention within the scope of not impairing the properties of the laminated film of the present invention. In addition, the substrate of the present invention may further contain an easy-to-adhere component for favorable lamination with the resin layer A of the present invention.

The thickness of the substrate constituting the laminated film of the present invention can be adjusted appropriately according to the required characteristics of the laminated film, but from the viewpoints of transportability and productivity during production and use, it is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm or more. In addition, from the same viewpoints as above, the thickness of the substrate constituting the laminated film is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 80 μm or less.

The laminated film of the present invention preferably has a resin layer B on the side opposite to the side having the resin layer A of the substrate. Here, the resin layer B is a layer that is arranged on the side opposite to the side having the resin layer A of the substrate, is a layer that contains at least a resin, and is a layer different from the resin layer A. In other words, the resin layer B is a layer that does not satisfy at least one of the above-mentioned (a), (b), and (c). This resin layer B preferably has releasability, and refers to a layer having a finite thickness.

The position of resin layer B is not particularly limited as long as it is placed on the side of the substrate opposite to the side having resin layer A, so the substrate and resin layer B may be placed in direct contact with each other, or another layer may be provided between the substrate and resin layer B.

Examples of resins used in the resin layer B of the laminate film of the present invention include olefin-based resins and ester-based resins, and from the viewpoints of productivity and processability, it is preferable to use an olefin-based resin as the main component. The main component referred to here refers to the component with the highest mass percentage (the component with the highest content) among the components constituting the resin layer B of the laminate film.

Examples of olefin resins suitable for the resin layer B include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, low-crystalline or non-crystalline ethylene-α-olefin copolymers, polypropylene, propylene-α-olefin copolymers, propylene-ethylene-α-olefin copolymers, ethylene-ethyl (meth)acrylate copolymers, ethylene-methyl (meth)acrylate copolymers, ethylene-n-butyl (meth)acrylate copolymers, and ethylene-vinyl acetate copolymers. These may be used alone or in combination. The α-olefin is not particularly limited as long as it can be copolymerized with propylene or ethylene, and examples include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-pentene, and 1-heptene. Among the above-mentioned polyolefin resins, from the viewpoint of imparting release properties by controlling the roughness of the resin layer B, it is preferable to use a method in which the main component constituting the resin layer B is polypropylene and an incompatible polyolefin is added thereto, or to use a commercially available block polypropylene, a so-called block copolymer, or an impact copolymer. The olefin-based resin in the resin layer B may be one type or two or more types. The olefin-based resin may be the above-mentioned olefin-based elastomer. On the other hand, the olefin-based resin does not include the above-mentioned styrene-based elastomer.

The melt flow rate (MFR, measured under conditions of 230°C and 2.16 kg) of the resin used in the resin layer B of the present invention is preferably 0.5 g/10 min or more, more preferably 1 g/10 min or more, and even more preferably 2 g/10 min or more, from the viewpoints of productivity and stability when laminating with adjacent layers. In addition, the MFR of the resin used in the resin layer B is preferably 30 g/10 min or less, more preferably 25 g/10 min or less, and even more preferably 20 g/10 min or less, from the same viewpoints as above.

The material constituting resin layer B may further contain a lubricant such as a fluorine-based resin, a silicone-based resin, a fatty acid metal salt, a fatty acid amide, inorganic particles, or organic particles as a release agent.

The laminate film of the present invention has resin layer B, which allows the laminate film to be wound into a roll in a good roll shape during the manufacturing process or slitting process, and allows the film to be unwound smoothly without too much force being applied when unwinding the film from the roll during slitting or use. As another method for imparting releasability to the surface opposite to resin layer A in the laminate film of the present invention, a method of adding the above-mentioned lubricant to the substrate without providing resin layer B can be mentioned, but from the viewpoints of productivity, cost, and release effect, the method of providing resin layer B is more preferable.

The arithmetic mean roughness Ra(B) of the resin layer B of the laminated film of the present invention is preferably 0.1 μm or more, more preferably 0.2 μm or more. There is no particular upper limit for the arithmetic mean roughness Ra(B) of the resin layer B, but if it is 2 μm or more, there may be problems with reduced thickness accuracy and strength.

The laminated film of the present invention has a substrate and a resin layer A on at least one side thereof, but as described above, it is preferable to have a resin layer B on the side opposite to the side having the resin layer A. The laminated film of the present invention may also have layers other than the substrate, the resin layer A, and the resin layer B, as long as the effects of the present invention are not impaired, but it is preferable that the resin layer A and the resin layer B are each located on the outermost surface of the laminated film. The thickness of the laminated film of the present invention is preferably 10 μm or more, more preferably 25 μm or more, from the viewpoint of transportability and productivity during production and use. The thickness of the laminated film is preferably 250 μm or less, more preferably 100 μm or less, from the same viewpoint as above.

Next, we will explain the manufacturing method of the laminated film of the present invention.

The method for producing the laminated film of the present invention is not particularly limited. For example, in the case of a three-layer laminate structure having a resin layer A, a substrate, and a resin layer B in this order, the resin compositions constituting each layer are melt-extruded from individual extruders and laminated together in a die, which is called a co-extrusion method, or a method in which the resin layer A, the substrate, and the resin layer B are melt-extruded separately and then laminated by a lamination method, etc. can be mentioned. From the viewpoint of productivity, however, it is preferable to produce the laminated film by the co-extrusion method. The materials constituting each layer may be mixed with each other using a Henschel mixer or the like, or all or part of the materials for each layer may be kneaded in advance. For the co-extrusion method, known methods such as the inflation method and the T-die method are used, but from the viewpoint of excellent thickness accuracy and surface shape control, the hot melt co-extrusion method using the T-die method is particularly preferable.

When manufacturing by the co-extrusion method, the components of resin layer A, the substrate, and resin layer B are each extruded from a melt extruder. At this time, the extrusion temperature of resin layer A is preferably 250°C or less, more preferably 230°C or less, and even more preferably 220°C or less. If the extrusion temperature of resin layer A exceeds 250°C, the arithmetic average roughness Ra(A) of the resin layer A side may not be controlled within the desired range. Although there is no particular lower limit, at a resin temperature of less than 180°C, the melt viscosity is too high, and productivity may decrease.

Resin layer A, the substrate, and resin layer B are laminated together inside the T-die and co-extruded. The resin is then cooled and solidified on a metal cooling roll, formed into a film, and wound into a roll to obtain a laminated film.

The laminated film of the present invention can be used as a surface protection film for preventing scratches and dirt adhesion during the production, processing, and transportation of synthetic resin plates, metal plates, glass plates, etc., but is preferably used as an optical surface protection film having uneven surfaces such as diffusion plates and prism sheets. It can also be preferably used as a surface protection film for use by bonding to an adherend having an arithmetic mean roughness Ra of 0.1 μm or more and 2 μm or less on the surface in contact with the resin layer A.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Measurements and evaluations of various physical properties were carried out by the following methods. Examples 1, 2, 4, and 6-10 below are to be read as Reference Examples 1, 2, 4, and 6-10.

(1) Surface roughness The arithmetic mean roughness Ra (A) of the resin layer A side, the arithmetic mean roughness Ra (B) of the resin layer B, the arithmetic mean roughness Ra (X) of the adherend X, the ten-point mean roughness Rz (X) of the adherend X, the arithmetic mean roughness Ra (Y) of the adherend Y, and the ten-point mean roughness Rz (Y) of the adherend Y were evaluated by using a high-precision fine shape measuring instrument (SURFCORDER ET4000A) manufactured by Kosaka Laboratory Co., Ltd., in accordance with JIS B0601-1994, with the scanning direction being the width direction and 21 measurements being carried out at 10 μm intervals in the longitudinal direction for a range of 2 mm in the width direction and 0.2 mm in the longitudinal direction of the laminated film and adherend, and three-dimensional analysis was performed. Note that a diamond needle with a stylus tip radius of 2.0 μm was used, and the measurement was performed with a measuring force of 100 μN and a cutoff of 0.8 mm.

(2) Maximum probe tack value Using a Rhesca TAC1000 tack tester, a SUS probe with a diameter of 5 mm was brought into contact with the resin layer A side of the laminate film under the following conditions, and the maximum load when peeled off was read and divided by the area of the probe to calculate the load per unit area. The test was performed five times for one type of laminate film, and the average value was taken as the maximum probe tack value F on the resin layer A side of the laminate film.
Temperature: 23°C
Holding time after placing the sample: 5 minutes Contact speed, peeling speed: 2 mm/sec Contact time: 2 seconds.

(3) The ratio hp/hm of the residual displacement hp to the maximum displacement hm measured by nanoindentation
Using an ENT-2100 nanoindentation tester manufactured by Elionix, a Berkovich indenter (triangular pyramid tip) was used to perform a load-unload indentation test 10 times for each type of laminate film from the resin layer A side of the laminate film under the following conditions: hp/hm was calculated from the obtained maximum displacement hm (unit: μm) and residual displacement hp (unit: μm), and the average value of hp/hm obtained from the 10 measurements was recorded as the hp/hm value for the resin layer A side of the laminate film.
Temperature: 26°C
Maximum load: 1mN
Loading speed/unloading speed: 0.1 mN/s
Load at the start of the load-unload test: 0 mN
Holding time at maximum load: 1 second Surface detection method: Inclined method Surface detection threshold coefficient: 1.5
Spring compensation: Real-time spring compensation.

(4) Melting point From the laminated film shown in the examples and comparative examples, only the resin layer A was scraped off using a stainless steel spatula, and 5 mg was weighed out to obtain a measurement sample. The sample was then collected in an aluminum pan, and using a differential scanning calorimeter (Seiko Denshi Kogyo RDC220) in a nitrogen atmosphere, the temperature was raised from room temperature to 250°C at 20°C/min, and the temperature was held at 250°C for 5 minutes, and then the temperature was lowered to 20°C at 20°C/min. After that, the temperature was raised again to 250°C at 40°C/min, and the temperature of the endothermic peak obtained at this time was defined as the melting point Tm of the resin layer A.

(5) Storage modulus From the laminated film shown in the examples and comparative examples, only the resin layer A was scraped off using a stainless steel spatula, and this was melt-molded to a thickness of 1 mm to obtain a sample. Measurements were performed using a rheometer AR2000ex manufactured by TA Instruments, and the temperature was lowered from 200°C to -20°C at a rate of 20°C/min, and then the temperature was raised from -20°C to 100°C at a rate of 10°C/min while dynamic shear deformation was performed at a frequency of 1 Hz and a strain of 0.01%, and the storage modulus G' at 50°C during the temperature rise process was taken as the storage modulus G'(A) of the resin layer A.

In addition, pellets of the olefin resin and styrene elastomer were melt-molded to a thickness of 1 mm, and the storage modulus G' at 25°C during the heating process obtained by measuring in the same manner as above was taken as G'(25).

(6) Thickness Using a microtome method, an ultra-thin section of 5 mm in width having a cross section in the width direction-thickness direction of the laminate film was prepared, and the cross section was platinum-coated to prepare an observation sample. Next, using a Hitachi field emission scanning electron microscope (S-4800), the cross section of the laminate film was observed at an acceleration voltage of 2.5 kV, and the thicknesses of the substrate, resin layer A, resin layer B, and the total thickness of the laminate film were measured from any point of the observed image. Regarding the observation magnification, the thicknesses of the resin layers A and B were measured at 5,000 times, and the thicknesses of the substrate and laminate film were measured at 1,000 times. Furthermore, the same measurement was performed a total of 10 times, and the average values were used as the thicknesses of the substrate, resin layers A and B, and the total thickness of the laminate film.

(7) tan δ (25)
After melt molding the pellets of the olefin resin to a thickness of 1 mm, the measurement was performed using a rheometer AR2000ex manufactured by TA Instruments. The temperature was lowered from 200°C to -20°C at a rate of 20°C/min, and then the temperature was raised from -20°C to 40°C at a rate of 10°C/min, while dynamic shear deformation was performed at a frequency of 1 Hz and a strain of 0.01%, and tan δ at 25°C during the heating process was taken as tan δ(25).

(8) Softening Point The softening point was measured based on the ring and ball method defined in JIS K-2207:2006.

(9) Melt flow rate (MFR)
The measurements were performed using a melt indexer manufactured by Toyo Seiki Seisakusho Co., Ltd., in accordance with JIS K7210-1997, at a temperature of 230°C and a load of 2.16 kg/ ^cm2 . The units are all g/10 min.

(10) Lamination of laminated film to adherend The resin layer A side of the laminated film of the examples and comparative examples, which had been stored and adjusted for 24 hours under conditions of 23°C temperature and 50% relative humidity, and the adherend were laminated using a roll press machine (special pressure roller manufactured by Yasuda Seiki Seisakusho Co., Ltd.) at a lamination pressure of 0.35 MPa. Two types of adherends (adherend X and adherend Y) were used, each having a matte surface formed on the opposite side of a prism sheet made of acrylic resin. The arithmetic mean roughness Ra(X) of adherend X was 0.2 μm, the ten-point mean roughness Rz(X) was 2.2 μm, and the arithmetic mean roughness Ra(Y) of adherend Y was 0.4 μm, and the ten-point mean roughness Rz(Y) was 3.2.

(11) Adhesive Strength The bonded sample obtained in (10) above was stored in a room at 23°C for 24 hours, and then adhesive strength was measured using a tensile tester (Orientec Co., Ltd. "Tensilon" universal testing machine) at a tensile speed of 300 mm/min and a peel angle of 180°. The adhesive strength of each of the adherends X and Y was measured for one type of laminated film. The adhesive strength ratio of the adherends X and Y was calculated according to the following formula (P1).
Adhesive strength ratio = Adhesive strength to adherend X / Adhesive strength to adherend Y Formula (P1)
The adhesive strength of the adherend X and the adherend Y was evaluated according to the following three-level criteria.
⊚: 5 g/25 mm or more and less than 15 g/25 mm ◯: 3 g/25 mm or more and less than 5 g/25 mm, or 15 g/25 mm or more and less than 25 g/25 mm ×: less than 3 g/25 mm, or 25 g/25 mm or more In addition, the adhesive strength ratio of adherend X and adherend Y calculated based on formula (P1) closer to 1 indicates that the laminate film is more excellent in adherend dependency, and was evaluated on the following three-level scale.
⊚: 0.5 or more and less than 2.0 ◯: 0.3 or more and less than 0.5, or 2.0 or more and less than 4.0 ×: less than 0.3, or 4.0 or more.

(12) Adhesive strength after heat storage Among the laminated samples obtained in (10) above, the sample laminated with the adherend X was stored in a hot air dryer at 50°C for 100 hours, and then stored under conditions of a temperature of 23°C and a relative humidity of 50%, and then the adhesive strength was measured using a tensile tester (Orientec Co., Ltd. "Tensilon" universal testing machine) at a tensile speed of 300 mm/min and a peel angle of 180°. According to the following formula (P2), the ratio of the adhesive strength after heat storage at 50°C to the adhesive strength after storage at 23°C to the adhesive strength calculated in (11) above for the adherend X was calculated, and this was taken as the adhesive enhancement ratio.
Adhesion enhancement ratio = Adhesion strength after storage at 50°C / Adhesion strength after storage at 23°C Formula (P2)
The adhesion enhancement ratio calculated based on formula (P2) indicates that the closer to 1 the laminate film is in stability during heated storage, and was evaluated according to the following three levels.
⊚: 0.5 or more and less than 1.6 ◯: 0.3 or more and less than 0.5, or 1.6 or more and less than 2.5 ×: less than 0.3, or 2.5 or more.

Example 1
The constituent resins for each layer were prepared as follows.

Substrate: 97% by mass of commercially available block polypropylene with an MFR of 8.5 g/10 min and 3% by mass of a styrene-based elastomer (Asahi Kasei SEBS, "Tuftec" H1052, MFR 13 g/10 min, G'(25) ≦ 10 MPa).

Resin layer A: 70% by mass of styrene-based elastomer (Asahi Kasei SEBS, "Tuftec" H1052, MFR 13 g/10 min, G'(25) ≦ 10 MPa), 15% by mass of high melt tension polypropylene (Japan Polypropylene Corporation, "Waymax" MFX8, MFR 1 g/10 min, G'(25) > 10 MPa, tan δ(25) < 0.5), and 15% by mass of tackifier (Arakawa Chemical Industries, "Alcon" M115, aromatic copolymer, softening point 115°C, hydrogenation rate < 90%). These were previously mixed and chipped in a twin-screw extruder.

Resin layer B: 95% by weight of the same commercially available block polypropylene used as the substrate, and 5% by weight of a commercially available silicone-based surface modifier used as a release agent.

Next, the constituent resins of each layer were fed into each extruder of a T-die composite film-forming machine having three extruders, and the output rate of each extruder was adjusted so that resin layer A was 3.5 μm, the substrate was 30 μm, and resin layer B was 5 μm. They were then laminated in this order and extruded from the composite T-die at an extrusion temperature of 200°C. The resins were then cast onto a roll whose surface temperature was controlled at 40°C, and molded into a film shape, which was then wound up to obtain a laminated film.

The obtained laminated film was then evaluated by the method described above. The thickness of the substrate was 30 μm, the thickness of the resin layer B was 5 μm, and the arithmetic mean roughness Ra(B) of the resin layer B was 0.20 μm.

Example 2
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting the resin layer A was 70% by mass of a styrene-based elastomer ("Tuftec" H1052), 15% by mass of a high melt tension polypropylene ("Waymax" MFX8), 5% by mass of a tackifier "Alcon" M115, and 10% by mass of a tackifier "FTR" 8100 (manufactured by Mitsui Chemicals, aromatic copolymer, softening point 100°C, hydrogenation rate <90%).

Example 3
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting the resin layer A was 60% by mass of a styrene-based elastomer ("Tuftec" H1052), 15% by mass of a high melt tension polypropylene ("Waymax" MFX8), 5% by mass of a tackifier "Alcon" M115, 10% by mass of a tackifier "FTR" 8100, and 10% by mass of an olefin-based elastomer ("Absortomer" EP-1001, manufactured by Mitsui Chemicals, MFR 10 g/10 min, G'(25) 33 MPa, tan δ(25) 1.9).

Example 4
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting resin layer A was 80% by mass of a styrene-based elastomer ("Tuftec" H1052), 10% by mass of high melt tension polypropylene ("Waymax" MFX8), and 10% by mass of a tackifier "Alcon" M115.

Example 5
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting resin layer A was 70% by mass of a styrene-based elastomer ("Tuftec" H1052), 10% by mass of high melt tension polypropylene ("Waymax" MFX8), 10% by mass of tackifier "Alcon" M115, and 10% by mass of an olefin-based elastomer ("Absoutomer" EP-1001).

Example 6
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting resin layer A was 79.5% by mass of a styrene-based elastomer ("Tuftec" H1052), 10% by mass of high melt tension polypropylene ("Waymax" MFX8), 10% by mass of a tackifier "Alcon" M115, and 0.5% by mass of commercially available ethylene bisstearic acid amide (EBSA).

(Example 7)
A laminated film was obtained in the same manner as in Example 1, except that, in the composition constituting the resin layer A, high-density polyethylene ("Nipolonhard" 7300A manufactured by Tosoh, density 952 kg/ ^m3 , MFR 2 g/10 min, G'(25) > 10 MPa, tan δ(25) < 0.5) was used instead of the high melt tension polypropylene ("Waymax" MFX8).

(Example 8)
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting the resin layer A was 70% by mass of a styrene-based elastomer ("Tuftec" H1052), 15% by mass of a high melt tension polypropylene ("Waymax" MFX8), and 15% by mass of a tackifier "Alcon" P125 (manufactured by Arakawa Chemical Industries, Ltd., aromatic copolymer, softening point 125°C, hydrogenation rate ≧90%).

Example 9
A laminated film was obtained in the same manner as in Example 1, except that the thickness of the resin layer A was 2.8 μm.

Example 10
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting the resin layer A was 70% by mass of a styrene-based elastomer ("Tuftec" H1052), 15% by mass of a high melt tension polypropylene ("Waymax" EX8000, MFR 1.5 g/10 min, G'(25)>10 MPa, tan δ(25)<0.5), 5% by mass of a tackifier "Alcon" M115, and 5% by mass of a tackifier "FTR" 8100 (manufactured by Mitsui Chemicals, aromatic copolymer, softening point 100°C, hydrogenation rate <90%).

(Comparative Example 1)
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting the resin layer A was 90% by mass of a styrene-based elastomer ("Tuftec" H1052) and 10% by mass of a tackifier "Alcon" M115.

(Comparative Example 2)
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting the resin layer A was 94 mass% styrene-based elastomer ("Tuftec" H1052), 5 mass% high melt tension polypropylene ("Waymax" MFX8), and 1 mass% commercially available ethylene bisstearic acid amide (EBSA).

(Comparative Example 3)
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting resin layer A was 69 mass% styrene-based elastomer ("Tuftec" H1052), 15 mass% high melt tension polypropylene ("Waymax" MFX8), 15 mass% tackifier ("Alcon" M115), and 1 mass% commercially available ethylene bisstearic acid amide (EBSA), and the thickness of resin layer A was 2.5 μm.

(Comparative Example 4)
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting the substrate was 97% by mass of homopolypropylene (manufactured by Sumitomo Chemical Co., Ltd., "Noblen" FLX80E4, MFR 8 g/10 min) and 3% by mass of styrene-based elastomer ("Tuftec" H1052), and the composition constituting resin layer A was 20% by mass of styrene-based elastomer ("Tuftec" H1052) and 80% by mass of olefin-based elastomer ("Absortomer" EP-1001).

(Comparative Example 5)
A laminated film was obtained in the same manner as in Example 1, except that the composition constituting the resin layer A was 70% by mass of a styrene-based elastomer ("Tuftec" H1052), 15% by mass of a high melt tension polypropylene ("Waymax" MFX3, MFR 9 g/10 min, G'(25)>10 MPa, tan δ(25)<0.5), and 15% by mass of a tackifier "Alcon" M115.

Examples 1 to 9, which satisfy the requirements of the present invention, were laminate films that had good adhesion to any adherend, had little adherend dependency, and were excellent in suppressing adhesion buildup. On the other hand, Comparative Examples 1 and 2 were laminate films that had high adhesion to adherend X, had poor adherend dependency, and were prone to adhesion buildup. Furthermore, Comparative Example 3 had insufficient adhesion to adherend Y. Comparative Example 4 was a laminate film that not only had insufficient adhesion to adherend Y, but was also prone to adhesion buildup.

The laminated film of the present invention has excellent adhesive properties such as adherend dependency, and can therefore be preferably used as a surface protection film for products made of various materials such as synthetic resins, metals, and glass, having various surface shapes.

Claims (6)

A laminated film having a substrate and a resin layer A on at least one side of the substrate, the laminated film satisfying the following (a), (b), and (c):
The arithmetic average roughness Ra(A) of the resin layer A side is 0.30 μm or more and 0.70 μm or less,
The resin layer A contains an olefin-based elastomer having a tan δ(25) of 0.5 or more at 25° C. and 1 Hz,
The resin layer A comprises an olefin resin having a melt flow rate of 0.01 g/10 min or more and 1.5 g/10 min or less at 230° C. and 2.16 kg.
(a) The maximum probe tack value F at 23° C. on the resin layer A side is 0.2 g/mm ² or more and 2.5 g/mm ² or less.
(b) When a nanoindentation load-unloading test is performed on the resin layer A side at 26°C with a maximum load of 1 mN, the ratio (hp/hm) of the residual displacement hp (unit: μm) to the maximum displacement hm (unit: μm) is 0.50 or more and 0.90 or less.
(c) Resin layer A has a melting point Tm of 50° C. or higher. The laminated film according to claim 1, wherein the storage modulus G'(A) of the resin layer A at 50°C and 1 Hz is 1.5 MPa or more. The laminated film according to claim 1 or 2, wherein the resin layer A contains a styrene-based elastomer having a melt flow rate of 3 g/10 min or more and 50 g/10 min or less at 230°C and 2.16 kg. The laminate film according to any one of claims 1 to 3, wherein the resin layer A contains an unhydrogenated or partially hydrogenated aromatic copolymer and/or an unhydrogenated or partially hydrogenated aliphatic-aromatic copolymer having a softening point of 80° C or higher. The laminated film according to any one of claims 1 to 4 , wherein the substrate comprises an olefin-based resin and a styrene-based elastomer. 6. The laminated film according to claim 1 , further comprising a resin layer B on the side opposite to the side on which the resin layer A is formed of the substrate.