JP7836688B2 - Laminated film - Google Patents

Description

This invention relates to a laminated film.

Optical products made from various materials such as synthetic resins, metals, and glass are susceptible to scratches and dirt during processing, transportation, and storage. Therefore, it is common practice to laminate protective sheets or films onto the surface. Generally, surface protective films with an adhesive layer formed on a support substrate made of thermoplastic resin or paper are used, and the adhesive layer is then applied to the substrate.

Examples of such surface protective films include those described in Patent Documents 1 to 3.

Japanese Patent Application Publication No. 04-146983 Special Publication No. 11-512478 Japanese Patent Publication No. 2011-037243

The required properties for such surface protection films include the ability to adhere to substrates with various surface shapes, not just smooth surfaces; resistance to peeling from the substrate due to environmental changes such as temperature and humidity, or minor stress; easy removal from the substrate after processing or use; and the absence of adhesive residue on the substrate after removal.

Products requiring surface protection films include, for example, display components, automotive components, building materials, and lenses for optical instruments and eyeglasses. Among these, lenses for optical instruments and eyeglasses have curved shapes, requiring strong adhesive force to protect the surface along its contours. However, achieving both strong adhesive force and ease of removal after use, as well as non-contamination of the adherend, has been extremely difficult.

Furthermore, in eyeglass lenses, polishing is performed during the surface finishing process. During this polishing, a block of molten low-melting-point alloy is cast onto the back of the lens surface, integrating it with the lens. This low-melting-point alloy is then mounted on a fixed shaft and rotated for polishing. In this process, a surface protection film is used on the back surface to protect the lens surface while ensuring adhesion with the low-melting-point alloy. While improving the adhesion of this surface protection film to the low-melting-point alloy generally involves improving the polarity of the contact surface with the alloy, it has been found that when conventional surface protection films are wound into a roll without a release liner, the adhesive surface and the low-melting-point alloy contact surface adhere strongly, making unwinding difficult.

Furthermore, when laminating the film to the lens, the film stretches during the lamination process, and then the stretched film is cut along the lens. However, with conventional surface protection films, lamination to the lens often resulted in uneven stretching, leading to localized stretching and tearing, making it difficult to cut the film along the lens.

Furthermore, even if the film can be uniformly stretched, if it is difficult to cut, film scraps are generated, worsening work efficiency. Therefore, achieving easy cutting was a challenge. For this reason, there is a need for a surface protection film that can be uniformly stretched and has excellent cutability.

The film described in Patent Document 1 has sufficient adhesion to low-melting-point alloys, but requires a release liner for winding in a roll, resulting in a high environmental impact. Furthermore, when used for eyeglass lenses, it presents problems such as poor cutting. The film described in Patent Document 2 also has sufficient adhesion to low-melting-point alloys, but lacks sufficient adhesive strength. When used for eyeglass lenses, it cannot conform to the curved surface of the lens, causing lifting at the edges and making cutting difficult. The film described in Patent Document 3 has excellent roll unwinding properties, but its adhesive strength is low. When used for eyeglass lenses, the film stretches locally during lamination to the lens, making cutting difficult.

Thus, the films described in Patent Documents 1 to 3 failed to provide a film that achieved both uniform stretchability during lens lamination and good cutability.

Therefore, the objective of the present invention is to provide a laminated film that maintains adhesiveness, exhibits excellent cutability, and has excellent uniform stretchability during lens bonding.

One preferred embodiment of the laminated film of the present invention is as follows.
(1) A laminated film having an adhesive resin layer A and a base layer, wherein the laminated film satisfies the following (a) and (b).
(a) Maximum tensile modulus of elasticity at 20% to 100% elongation in the extrusion direction (MD) is 1.0 to 20 MPa
(b) Tear strength in the extrusion direction (MD) of 4.9 to 49 N/mm
(2) The laminated film according to (1), wherein the stress ratio (stress in MD / stress in TD) between the extrusion direction (MD) and the width direction (TD) when stretched to 100% is 1.0 to 2.0.
(3) The laminated film according to (1) or (2), wherein the water contact angle of the surface opposite to the surface on the side of resin layer A is 90° or more and 110° or less.
(4) A laminated film according to any one of (1) to (3), wherein the maximum polycarbonate probe tack F on the surface of resin layer A is 0.098 to 0.245 N/ ^mm² .
(5) A laminated film according to any one of (1) to (4), wherein the surface on the side of resin layer A and the surface on the opposite side of the surface on the side of resin layer A are bonded at a pressure of 0.1 MPa, and the 180° peel strength after 24 hours of storage is 5.88 N/25 mm or less.
(6) A laminated film according to any one of (1) to (5), wherein the base layer contains a coloring agent.

The present invention aims to provide a laminated film that maintains adhesiveness, exhibits excellent cutability, and provides excellent uniform stretchability during lens bonding.

The embodiments of the present invention will be described below.

A preferred embodiment of the present invention is a laminated film having an adhesive resin layer A and a base layer, wherein the laminated film satisfies the following conditions (a) and (b).
(a) The maximum tensile modulus of elasticity when elongated from 20% to 100% in the extrusion direction (MD) is 1.0 to 20 MPa. (b) The tear strength in the extrusion direction (MD) is 4.9 to 49 N/mm.

By adopting the above configuration, it is possible to provide a laminated film that maintains adhesiveness while exhibiting excellent cutability and uniform stretchability during lens bonding.

Here, the resin layer A is preferably adhesive. Preferred embodiments of the resin layer A will be described later. In this invention, the surface of the laminated film on the resin layer A side refers to the air-side surface when the laminated film is placed in air and viewed in the order of air, resin layer A, and base layer.

From the viewpoint of cutting the laminated film after bonding to the adherend, it is preferable to include an olefin resin in the base layer. However, this presents a problem in that the film may not be uniformly stretched during bonding to the adherend, making it difficult to cut. To achieve both cutability and uniform stretchability in the laminated film, the inventors conducted extensive research and discovered that by setting the maximum tensile modulus and tear strength of the laminated film within a preferred range (20% to 100% elongation), it is possible to obtain a laminated film that maintains adhesiveness while exhibiting excellent cutability and uniform stretchability during lens bonding. This led to the present invention. The details are described below.

The laminated film of the present invention preferably has a maximum tensile modulus of elasticity of 1.0 to 20 MPa at 20% to 100% tension in the extrusion direction (MD) at a tensile speed of 300 mm/min. The tensile modulus can be calculated by performing a tensile test in the extrusion direction (MD direction) of the laminated film using the method described in the examples. If the MD direction of the laminated film is unknown, the tensile modulus can be calculated using the following method. First, tensile tests are performed five times each in four directions at 45° intervals, starting from an arbitrary direction within the film surface. Then, the arithmetic mean of the values in each direction is calculated, and the arithmetic mean of the direction with the highest tensile modulus is taken as the tensile modulus of the laminated film of the present invention.

By setting the maximum tensile modulus at 20% to 100% tension in the extrusion direction (MD) at a tensile speed of 300 mm/min to 1.0 MPa or higher, the laminated film can be stretched uniformly without localized stretching when bonded to an adherend, and film breakage during peeling can be suppressed. From a similar viewpoint, the maximum tensile modulus at 20% to 100% tension in the extrusion direction (MD) at a tensile speed of 300 mm/min is more preferably 5 MPa or higher. Furthermore, if the maximum tensile modulus at 20% to 100% tension in the extrusion direction (MD) at a tensile speed of 300 mm/min exceeds 20 MPa, the stress ratio between the extrusion direction (MD) and the width direction (TD) of the laminated film becomes large, and in the case of circular adherends such as eyeglass lenses, the laminated film cannot be stretched uniformly, stretching locally and becoming difficult to cut. Therefore, a maximum tensile modulus of 20 MPa or less at 20% to 100% tension is preferable. From a similar viewpoint, the maximum tensile modulus of the laminated film of the present invention at 20% to 100% tension in the extrusion direction (MD) at 300 mm/min is more preferably 10 MPa or less.

The tensile modulus of the laminated film of the present invention can be adjusted by adjusting the material and thickness of the base layer and resin layer A, as described later, but it can be achieved in particular by controlling the rigidity of the base layer based on the raw material composition and film formation conditions described later. Specifically, as a method to make the maximum tensile modulus of elasticity 1.0 to 20 MPa when tensile at 20% to 100% in the extrusion direction (MD) at 300 mm/min, for example, a method in which polyethylene resin such as low-density polyethylene with a density of 910 to 940 kg/ ^m³ , medium-density polyethylene, or linear low-density polyethylene is mainly included in the base layer.

The laminated film of the present invention preferably has a tear strength of 4.9 to 49 N/mm in the extrusion direction (MD direction). The tear strength can be measured and calculated by the method described in the examples. If the extrusion direction (MD direction) of the laminated film is unknown, the tear strength can be calculated by the following method. First, the tear strength is evaluated five times each in four directions at 45° intervals, starting from any direction within the film surface. Then, the arithmetic mean of each direction is calculated, and the arithmetic mean of the direction with the highest tear strength and the direction at 90° to this direction (average of a total of 10 measurements) is taken as the tear strength of the laminated film of the present invention in the extrusion direction (MD direction). By setting the tear strength in the extrusion direction (MD direction) to 4.9 N/mm or higher, film breakage when peeling the film from the adherend can be suppressed. From a similar viewpoint, the tear strength in the extrusion direction (MD direction) is more preferably 9.8 N/mm or higher, and even more preferably 19.6 N/mm or higher. Furthermore, by setting the tear strength in the extrusion direction (MD direction) to 49 N/mm or less, the cutability of the laminated film when it is bonded to a curved surface such as a lens can be improved. From a similar viewpoint, a tear strength in the extrusion direction (MD direction) of 34.3 N/mm or less is more preferable.

The tear strength can be controlled by adjusting the materials, thickness, and film-forming conditions of the resin layer A, the base layer, or the layer having a surface opposite to the surface of resin layer A. In particular, it can be achieved by controlling the rigidity of the base layer based on the raw material composition of the base layer, as described later. A preferred method for achieving a tear strength of 4.9 N to 49 N/mm in the extrusion direction (MD direction) is similar to the method for achieving a maximum tensile modulus of elasticity of 1.0 to 20 MPa at 20% to 100% tension in the extrusion direction (MD).

The laminated film of the present invention preferably has a stress ratio (MD stress/TD stress) of 1.0 to 2.0 in the extrusion direction (MD) to the width direction (TD) when tensile at 100% tension at a tensile speed of 300 mm/min. The MD/TD stress ratio can be calculated by performing a tensile test on the laminated film using the method described in the examples. If the MD direction of the laminated film is unknown, the MD/TD stress ratio can be calculated using the following method. First, tensile tests are performed five times each in four directions at 45° intervals, starting from an arbitrary direction within the film surface. Then, the tensile stress in each direction is determined, and the direction with the highest tensile stress is taken as the MD tensile stress, and the tensile stress in the direction 90° to that direction is taken as the TD tensile stress. By setting the stress ratio (MD stress/TD stress) between the extrusion direction (MD) and the width direction (TD) at 100% tensile strength at a tensile speed of 300 mm/min to 1.0 or higher, circular adherends such as eyeglass lenses can be stretched more uniformly during bonding. Similarly, from the viewpoint of uniform stretchability, a stress ratio (MD stress/TD stress) of 2.0 or less at 100% tensile strength is preferable.

In order to achieve sufficient adhesion between the surface opposite to the resin layer A side and the low-melting-point alloy, the water contact angle of the laminated film of the present invention is preferably 90° to 110°.

The water contact angle was measured using the method described in the examples. By setting the water contact angle to 110° or less, the problem of the low-melting-point alloy block peeling off when the laminated film of the present invention is bonded to a curved substrate, a low-melting-point alloy is cast onto the surface opposite to the surface of resin layer A, and then integrated with the lens, and the lens is polished by pressing this block-shaped low-melting-point alloy against a rotating polishing surface mounted on a fixed shaft can be further resolved. From a similar viewpoint, the water contact angle of the surface opposite to the surface of resin layer A is preferably 105° or less, and more preferably 100° or less. Furthermore, by setting the water contact angle to 90° or more, the low-melting-point alloy cast onto the laminated film can be easily peeled off after lens polishing.

The adhesion force with the low-melting-point alloy can be controlled by the materials of the base layer and resin layer A, as well as the film-forming conditions, including the layer containing the surface opposite to the surface of resin layer A (described later). In particular, this can be achieved by controlling the adhesive properties of resin layer A, the rigidity of the base layer, and the surface properties of the layer containing the surface opposite to the surface of resin layer A, based on the raw material composition described later. A specific method for achieving a water contact angle of 90 to 110° on the surface opposite to the surface of resin layer A is, for example, a method in which 80% by mass or more of ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer are contained in 100% by mass of the layer containing the surface opposite to the surface of resin layer A.

The laminated film of the present invention preferably has a polycarbonate probe tack maximum value F of 0.098 to 0.245 N/ ^mm² on the surface on the resin layer A side. The polycarbonate probe tack maximum value F is measured by the method described in the examples. The polycarbonate probe tack maximum value F is an index of the tackiness of the surface on the resin layer A side, evaluated with a polycarbonate probe. Furthermore, if the surface on the resin layer A side and the surface opposite to the resin layer A side of the laminated film are unknown, the surfaces can be identified by the following method. First, the polycarbonate probe tack maximum value F of both sides of the laminated film is measured according to the method described in the examples. Then, the surface with a large arithmetic mean of the polycarbonate probe tack maximum value F of the laminated film is designated as the surface on the resin layer A side, and the surface with a small value is designated as the surface opposite to the resin layer A side.

When the maximum polycarbonate probe tack F on the surface of resin layer A is 0.098 N/ ^mm² or higher, sufficient adhesion can be achieved, and when the laminated film of the present invention is bonded to a curved substrate, it is possible to suppress the laminated film from lifting away from the substrate due to its inability to conform to the curved surface. Furthermore, because it has sufficient adhesive strength, when used as a protective film for eyeglass lenses, for example, it is possible to suppress the film from peeling off the lens during polishing of the eyeglass lenses. In addition, when peeled off from the substrate, the adhesive component is less likely to remain on the substrate. From a similar viewpoint, the maximum polycarbonate probe tack F is more preferably 0.147 N/ ^mm² or higher, and even more preferably 0.196 N/ ^mm² or higher.

Furthermore, since the maximum polycarbonate probe tack value F is 0.245 N/ ^mm² or less, even when the layer including the surface opposite to the surface on the resin layer A side contains a polyolefin resin containing a carboxylic acid group and/or a polyolefin resin containing a carboxylic acid metal base, and when wound into a roll without a release liner, it can be easily unwound without blocking, thus not impairing workability.

The maximum polycarbonate probe tack value F can be achieved by controlling the surface condition based on the raw material composition and film formation conditions described later. Specifically, as a method to set the maximum polycarbonate probe tack value F on the resin layer A side surface to 0.098 to 0.245 N/ ^mm² , for example, a method in which 60 to 90% by mass of styrene-based elastomer having a storage modulus of 0.1 to 0.9 MPa at 25°C and 1 Hz is contained in 100% by mass of resin layer A, and 10 to 40% by mass of terpene-based resin is contained in resin layer A as a tackifier.

By setting the viscoelasticity and content of the styrene-based elastomer contained in resin layer A within the above range, the laminated film of the present invention exhibits good adhesion when bonded to an adherend, and demonstrates excellent adhesive properties, such as suppression of adhesive residue. Furthermore, by including a terpene-based resin in resin layer A and setting its content within the above range, good adhesion to adherends with curved shapes can be obtained. Additionally, adhesive residue is less likely to occur when peeling the film off after bonding to an adherend.

The laminated film of the present invention preferably has a 180° peel strength (hereinafter referred to as peel strength) of 5.88 N/25 mm or less, more preferably 4.9 N/25 mm or less, and even more preferably 2.94 N/25 mm or less, after being stored for 24 hours following lamination of the surface of the laminated film on the side of resin layer A with the surface opposite to the resin layer A side at 0.1 MPa. From the viewpoint of ease of handling, a lower peel strength is preferable, and no specific lower limit is set. However, considering that it is preferable for the surface on the side with resin layer A to be adhesive, the practical lower limit is approximately 0.49 N/25 mm. When the peel strength is within the above preferred range, the laminated film of the present invention can be easily unwound when used, even when wound into a roll without using a release liner. The peel strength was measured using the method described in the examples.

Furthermore, the peeling force can be controlled to the preferred range by adjusting the material and surface roughness of the layer including the surface opposite to the surface of resin layer A, as well as the rigidity of the base layer, as described later. Specifically, for example, it is preferable to set the ten-point average roughness Rz of the surface opposite to the surface of resin layer A to 5 μm or more, and to include a 4-methyl-1-pentene-α-olefin copolymer in the layer including the surface opposite to the surface of resin layer A.

Furthermore, the thickness of the laminated film of the present invention is preferably 15 μm or more, and more preferably 30 μm or more, from the viewpoint of transportability and productivity during manufacturing and use. In addition, the thickness of the laminated film is preferably 250 μm or less, in addition to the same viewpoints as above, from the viewpoint of conformability to the adherend.

The film roll obtained by winding the laminated film of the present invention is preferably a film roll in which the surface of the laminated film having the resin layer A is in contact with the surface of the opposite layer. By adopting this configuration without a release liner, the process of peeling off the release liner during use can be eliminated, further reducing the amount of waste. Furthermore, because a release liner is not laminated, the usable surface area of the protective film per roll increases, and effects such as reducing the frequency of roll product replacement can be expected.

(Resin layer A)
The resin layer A in the present invention 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. However, it is preferable that the components after drying the insoluble matter (tetrahydrofuran insoluble matter) obtained by extracting the resin layer A with tetrahydrofuran contain at least a styrene component as a monomer component, and that the storage modulus G'(25) of the components after drying the insoluble matter at 25°C and 1 Hz is 0.05 to 0.9 MPa, and that the content of the insoluble matter in 100% by mass of the resin layer A is 40 to 90% by mass.

Furthermore, when resin layer A in the present invention is extracted with tetrahydrofuran, an excess amount of acetone is added to the dissolved substance. The resulting insoluble matter (acetone-insoluble matter) and acetone-soluble matter are centrifuged using a centrifuge, and the components after drying the separated acetone-soluble matter preferably contain a terpene resin. When resin layer A is considered as 100% by mass, the content of the components after drying the acetone-soluble matter is preferably 10 to 40% by mass. In particular, it is more preferable that 100% by mass of resin layer A contains 40 to 90% by mass of styrene elastomer and 10 to 40% by mass of terpene resin. Even more preferable is that the storage modulus G'(25) of the styrene elastomer at 25°C and 1 Hz is 0.05 to 0.9 MPa. The tetrahydrofuran-insoluble matter, acetone-soluble matter, and methods for extracting and analyzing the acetone-insoluble matter can be carried out by the following methods.

First, with the resin layer A side of the laminated film facing upwards, the opposite side of the resin layer A side is pressed tightly against the inside of the tray. Tetrahydrofuran is poured onto the resin layer A side and immersed at a liquid temperature of 25°C for 10 minutes. After that, the solution is collected and used as the one-sided extract (extraction area: 15 cm x 20 cm x 2 sheets of laminated film). Then, the tetrahydrofuran insoluble and tetrahydrofuran soluble substances are separated by centrifugation. Next, acetone is poured into the tetrahydrofuran soluble substance at a ratio of 50 L of acetone to 1 L of tetrahydrofuran, and the acetone insoluble substance is separated by centrifugation. The tetrahydrofuran insoluble substance, acetone soluble substance, and acetone insoluble substance are dried, their mass is determined, and then the mass percentage of each sample is calculated relative to the mass of resin layer A, which is set to 100% by mass. Of these, ^1H -NMR is performed on the tetrahydrofuran insoluble substance and acetone insoluble substance, and the presence or absence of styrene components is confirmed by identifying the peaks. Furthermore, after calculating the amount of styrene-containing material based on the peak area ratios of tetrahydrofuran-insoluble and acetone-insoluble materials, the mass percentage of tetrahydrofuran-insoluble material and the mass percentage of acetone-insoluble material are multiplied by these two values and summed to obtain the styrene-based elastomer content in 100% by mass of resin layer A.

Next, the tetrahydrofuran-insoluble material is dried and then melt-molded to a thickness of 1 mm to obtain a sample. Measurements are performed using a TA Instruments AR2000ex rheometer. The sample is cooled from 200°C to -20°C at a rate of 20°C/min, then heated from -20°C to 40°C at a rate of 10°C/min while undergoing dynamic shear deformation at a frequency of 1 Hz and a strain of 0.01%. The storage modulus at 25°C during the heating process of the tetrahydrofuran-insoluble sample is evaluated. When a dried tetrahydrofuran-insoluble material and a dried acetone-insoluble material are melt-mixed and melt-molded and measured in the same manner as described above, the storage modulus obtained is 0.05 to 0.9 MPa. Alternatively, if the storage modulus G'(25) of the styrene-based elastomer determined from the raw materials at 25°C and 1 Hz is 0.05 to 0.9 MPa, then the storage modulus G'(25) of the styrene-based elastomer at 25°C and 1 Hz is considered to be 0.05 to 0.9 MPa.

For the dried acetone-soluble material, ^1H -NMR is performed, and the ratio of terpene resin is determined from the peak area ratio. This ratio is then multiplied by the mass percentage of the acetone-soluble material to obtain the terpene resin content in resin layer A.

By adopting the above configuration, sufficient tackiness is achieved while minimizing adhesive residue. Furthermore, the surface opposite to the resin layer A side exhibits the preferred configuration described above, and blocking is reduced even when the film is wound onto a roll without a release liner. Specifically, the storage modulus G'(25) at 25°C and 1 Hz of the component remaining after drying the insoluble material extracted from resin layer A with tetrahydrofuran is 0.05 to 0.9 MPa. This component itself provides some tackiness, and because it has low adhesive residue, when included with the terpene resin, it provides sufficient tackiness. Even when the laminated film of the present invention is wound without a release liner, it can be easily unwound during use. Additionally, by including a terpene resin that does not have excessively high tack-imparting properties, sufficient tackiness is achieved while minimizing adhesive residue when the laminated film is peeled from the substrate.

As a method for achieving the above embodiment, a method is preferred in which 40 to 90% by mass of styrene-based elastomer and 10 to 40% by mass of terpene-based resin are contained in 100% by mass of resin layer A. 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. As the styrene-based elastomer, for example, styrene-conjugated diene copolymers such as styrene-butadiene copolymer (SBR), styrene-isoprene-styrene copolymer (SIS), and styrene-butadiene-styrene copolymer (SBS), or their hydrogenated products can be used. Specifically, for example, hydrogenated styrene-butadiene copolymer (HSBR), styrene-ethylenebutylene-styrene triblock copolymer (SEBS), styrene-ethylenebutylene diblock copolymer (SEB), and styrene-isobutylene copolymers can be suitably used. As the styrene-isobutylene copolymer mentioned above, for example, styrene-isobutylene-styrene triblock copolymer (SIBS), styrene-isobutylene diblock copolymer (SIB), or mixtures thereof can be suitably used. Among these, from the viewpoint of having sufficient tackiness while minimizing adhesive residue, maintaining the preferred configuration on the surface opposite to the resin layer A side, and reducing blocking when wound onto a roll without a release liner, it is more preferable to use one or more selected from styrene-butadiene-styrene copolymers such as styrene-conjugated diene copolymers, their hydrogenated derivatives, and styrene-isobutylene copolymers. Using styrene-ethylenebutylene-styrene triblock copolymer (SEBS) is even more preferable. Furthermore, only one type of styrene elastomer may be used, or two or more types may be used in combination.

Furthermore, when the laminated film of the present invention is laminated to a curved substrate, in order to prevent the laminated film from lifting away from the substrate due to its inability to conform to the curved surface and to adequately protect the substrate, it is preferable that the storage modulus G'(25) of the styrene-based elastomer at 25°C and 1 Hz is 0.9 MPa or less, more preferably 0.7 MPa or less, and even more preferably 0.5 MPa or less. Also, in order to suppress adhesive residue when peeling off the laminated film of the present invention after use, it is preferable that the storage modulus G'(25) of the styrene-based elastomer is 0.05 MPa or more, and more preferably 0.1 MPa or more.

The melt flow rate (measured under the conditions of MFR, 230°C, and 2.16 kg) of the styrene-based elastomer is preferably 2 g/10 min or more, more preferably 4 g/10 min or more, and even more preferably 10 g/10 min or more. Furthermore, the MFR of the styrene-based elastomer is preferably 60 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 within the above range, excellent productivity can be achieved, and when the laminated film of the present invention is used as a surface protective film, good adhesive properties can be obtained.

Furthermore, the styrene content in the styrene-based elastomer is preferably 5% by mass or more, and more preferably 8% by mass or more, when the total styrene-based elastomer is considered to be 100% by mass. Also, the styrene content in the styrene-based elastomer is preferably 55% by mass or less, and more preferably 40% by mass or less. By keeping the styrene content 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, suppresses adhesive residue, and demonstrates other excellent adhesive properties.

In the present invention, the resin layer A preferably contains a tackifier to enhance adhesion to the adherend. While known tackifiers can be used, commonly used ones can be employed, such as aliphatic copolymers, aromatic copolymers, aliphatic-aromatic copolymers, alicyclic copolymers, petroleum resins, terpene resins, rosin resins, alkylphenol resins, xylene resins, or their hydrogenated derivatives. Among these, aliphatic copolymers, aliphatic-aromatic copolymers, terpene resins, and their hydrogenated derivatives are preferred due to their excellent compatibility with the styrene elastomer and their ability to increase the maximum polycarbonate probe tack value F of the laminated film. In particular, terpene resins and their hydrogenated derivatives are more preferably used from the above-mentioned perspective, and terpene phenol resins are even more preferably used as the terpene resin.

The tackifier content is preferably 10% by mass or more, and more preferably 15% by mass or more, when the entire resin layer A is considered to be 100% by mass. Furthermore, the tackifier content is preferably 40% by mass or less, and more preferably 30% by mass or less, when the entire resin layer A is considered to be 100% by mass. By setting the tackifier content to 10% by mass or more, the maximum polycarbonate probe tack value F of the laminated film of the present invention can be increased, resulting in good adhesion to curved substrates. Additionally, by setting the tackifier content to 40% by mass or less, adhesive residue is less likely to occur when peeling after bonding to a substrate.

The resin layer A in the present invention may contain an olefin resin from the viewpoint of controlling the viscoelasticity of the resin layer and adjusting the adhesive strength, and from the viewpoint of obtaining good film-forming properties. Examples of olefin resins include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, low-crystalline or amorphous ethylene-α-olefin copolymer, crystalline polypropylene, low-crystalline polypropylene, amorphous polypropylene, propylene-ethylene copolymer (random copolymer and/or block copolymer), propylene-α-olefin copolymer, propylene-ethylene-α-olefin copolymer, polybutene, 4-methyl-1-pentene-α-olefin copolymer, ethylene-ethyl (meth)acrylate copolymer, ethylene-methyl (meth)acrylate copolymer, ethylene-n-butyl (meth)acrylate copolymer, and ethylene-vinyl acetate copolymer, which may be used alone or in combination. The α-olefin is not particularly limited as long as it can copolymerize with ethylene or propylene. For example, ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-pentene, and 1-heptene are preferred.

Among the olefin resins mentioned above, low-density polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, polybutene, crystalline polypropylene, low-crystalline polypropylene, amorphous polypropylene, or 4-methyl-1-pentene-α-olefin copolymer are preferably used.

When an olefin-based resin is used in the resin layer A of this invention, its content is preferably 20% by mass or less, and more preferably 10% by mass or less, when the total mass of resin layer A is considered to be 100% by mass.

The resin layer A in this invention may contain other components such as resin components and particles, fillers, and additives other than the styrene-based elastomer, tackifier, and olefin-based resin mentioned above, as long as they do not impair the objectives of this invention. Examples of such additives include lubricants, nucleating agents, antioxidants, heat-resistant agents, weather-resistant agents, and antistatic agents. These additives may be used individually or in combination, but the total content of these additives is preferably 3% by mass or less, and more preferably 2% by mass or less, when the total mass of the resin layer A is considered to be 100% by mass.

(Base material layer)
A preferred embodiment of the laminated film of the present invention has a base layer, where the base layer refers to a sheet-like material having a finite thickness.

In this invention, the base layer may be positioned as the outermost layer opposite to the surface of resin layer A, and may also be a layer that includes the surface opposite to the surface of resin layer A. However, it is more preferable to have a three-layer structure consisting of resin layer A, the base layer, and the layer opposite to the surface of resin layer A (hereinafter sometimes referred to as resin layer B). In this case, the material of the base layer is not particularly limited, but for example, olefin resins or ester resins can be used, and among these, it is preferable to use an olefin resin as the main component from the viewpoint of productivity and processability. The main component referred to here means the component with the highest mass percentage among all the components constituting the base layer.

Examples of the olefin resins included as the main component in the substrate layer include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, low-crystalline or amorphous 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, ethylene resins such as low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, low-crystalline or amorphous 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 are particularly preferred. These may be used alone or in combination.

In particular, as an olefin resin suitable for the laminated film of the present invention, methods that mainly contain low-density polyethylene with a density of 910 to 940 kg/ ^m³ , medium-density polyethylene, linear low-density polyethylene, etc., are preferred. Among these, the use of low-density polyethylene with a density of 910 to 940 kg/ ^m³ is especially preferred. By using low-density polyethylene with a density of 910 to 940 kg/ ^m³ and an MFR of 0.2 to 10 g/min, the rigidity of the base layer can be controlled, and the uniform stretchability of the laminated film of the present invention can be achieved.

Furthermore, from the viewpoint of controlling tear strength and rigidity, it is more preferable to use low-density polyethylene with a density of 920 to 930 kg/ ^{m³ and} an MFR of 0.4 to 6 g/min. By using low-density polyethylene with a density of 920 to 940 kg/m³ and an MFR of 0.4 to 6 g/min, the uniform stretchability of the laminated film of the present invention can be further enhanced.

The base layer in the present invention preferably contains a styrene-based elastomer. That is, the base layer of the laminated film of the present invention more preferably contains an olefin-based resin and a styrene-based elastomer, even more preferably contains the olefin-based elastomer and an olefin-based resin excluding the olefin-based elastomer, and particularly preferably contains the olefin-based elastomer, an olefin-based resin excluding the olefin-based elastomer, and a styrene-based elastomer.

By including a styrene-based elastomer in the base layer, when a styrene-based elastomer is used in the resin layer A, the affinity between the base layer and the resin layer A is improved, and the interfacial adhesion between the base layer and the resin layer A can be enhanced. When the entire base layer is considered as 100% by mass, the styrene-based elastomer content in the base layer is preferably 1% by mass or more, and more preferably 2% by mass or more. Furthermore, the styrene-based elastomer content in the base layer is preferably 20% by mass or less, and more preferably 10% by mass or less. In addition, known styrene-based elastomers can be used in the base layer of this invention; for example, the same styrene-based elastomer suitable for the resin layer A described above can be used.

One method for incorporating a styrene-based elastomer into the base layer of the present invention is to use a resin layer A containing a recovered laminated film with recycled raw materials added to it. This method is preferable from the viewpoint of resin recycling and reducing production costs.

Furthermore, the substrate layer in the present invention may contain various additives such as nucleating agents, lubricants, antioxidants, weather-resistant agents, and antistatic agents, as long as they do not impair the properties of the laminated film of the present invention. The substrate layer in the present invention may also contain an easy-adhesion component to ensure good lamination with the resin layer A of the present invention.

The laminated film of the present invention preferably contains a coloring agent in the base layer. When used as a surface protective film, coloring the laminated film can reduce the risk of forgetting to remove it. To suppress contamination of the adherend, it is preferable to include the coloring agent in the base layer. While the coloring agent is not particularly limited, it is preferably a pigment from the viewpoint of dispersibility in the resin.

The above-mentioned pigments may be either inorganic or organic pigments. Examples of inorganic pigments include pigments derived from natural earths such as amber, sienna, and calcium carbonate, as well as synthetic inorganic pigments such as Prussian blue, titanium dioxide, zinc oxide, synthetic iron oxide red, cadmium yellow, nickel titanium yellow, strontium yellow, hydrated chromium oxide, chromium oxide, cobalt aluminate, and synthetic ultramarine blue. Carbon flax can also be used. Organic pigments can be azo pigments or polycyclic pigments. Examples of azo pigments include monoazo pigments, disazo pigments, condensed disazo pigments, and benzimidazolone pigments. Examples of polycyclic pigments include isoindolinone, isoindoline, azomethine, anthraquinone, anthrone, xanthene, diketopyrrolopyrrole, perylene, quinacridone, indigoid, dioxazine, and phthalocyanine. These inorganic and organic pigments may be used individually or in combination.

(The layer including the surface opposite to the surface on the side of resin layer A: resin layer B)
The laminated film of the present invention is a laminated film having at least a resin layer A and a base layer, but the layer including the surface opposite to the surface on the side of resin layer A is a layer that contains at least resin and is a different layer from resin layer A. For example, if the laminated film of the present invention has a two-layer structure of resin layer A and base layer, the layer including the surface opposite to the surface on the side of resin layer A refers to the base layer. As another example, if the laminated film of the present invention has a three-layer structure of resin layer A, base layer and resin layer B, and each layer is laminated in this order, the layer including the surface opposite to the surface on the side of resin layer A refers to resin layer B. The resin layer B refers to, for example, a layer having a thickness of up to 250 μm, and preferably has release properties such that it does not block when wound into a roll on the surface of the laminated film that has resin layer A.

The laminated film of the present invention preferably has a polycarbonate probe tack maximum value F of 0.098 to 0.245 N/ ^mm² on the surface of resin layer A, and from the viewpoint of improving adhesion with low-melting-point alloys and suppressing blocking when wound into a roll, it is preferable that the base layer and resin layer B include a polyolefin resin containing carboxylic acid groups and/or a polyolefin resin containing a carboxylic acid metal base. The preferred composition and content of the polyolefin resin containing carboxylic acid groups and/or a polyolefin resin containing a carboxylic acid metal base is preferably 90% by mass or less of ethylene-acrylic acid copolymer and/or ethylene-methacrylic acid copolymer with an acid content of 6 to 15% by mass as determined by FT-IR measurement, and more preferably 80% by mass or less.

By setting the content of polyolefin resins containing carboxylic acid groups and/or polyolefin resins containing carboxylic acid metal bases in the base layer and resin layer B to the above-mentioned preferred range, when the laminated film of the present invention is used as a surface protective film, good adhesion with the low-melting-point alloy cast on the base layer and resin layer B is maintained, while blocking with resin layer A is suppressed when wound into a roll, allowing for easy unwinding. This is also preferable from the viewpoint of achieving uniform stretchability of the laminated film.

Furthermore, the base layer and resin layer B in this invention may contain other olefin resins from the viewpoint of adjusting adhesion to low-melting-point alloys, tackiness with resin layer A when wound into a roll, and obtaining good transportability and handling during use.

Examples of other olefin resins mentioned above include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, low-crystalline or amorphous ethylene-α-olefin copolymers, crystalline polypropylene, low-crystalline polypropylene, amorphous polypropylene, propylene-ethylene copolymers (random copolymers and/or block copolymers), propylene-α-olefin copolymers, propylene-ethylene-α-olefin copolymers, polybutene, and 4-methyl-1-pentene-α-olefin copolymers. These may be used individually or in combination. The α-olefin is not particularly limited as long as it can copolymerize with ethylene or propylene. For example, ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-pentene, and 1-heptene are preferred.

Among the olefin resins mentioned above, one or more selected from low-density polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, polybutene, crystalline polypropylene, low-crystalline polypropylene, amorphous polypropylene, and 4-methyl-1-pentene-α-olefin copolymer are preferably used.

When an olefin resin is used in the layer including the surface opposite to the surface of resin layer A in this invention, its content is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 20% by mass or less, when the resin content of the base layer and resin layer B is taken as 100% by mass.

The melt flow rate (measured under MFR, 190°C, 2.16 kg) of the olefin resin is preferably 0.5 g/10 min or higher, more preferably 1.0 g/10 min or higher, and even more preferably 2.0 g/10 min or higher, from the viewpoint of productivity and stability during lamination with adjacent layers. Furthermore, the MFR of the olefin resin is preferably 30 g/10 min or lower, more preferably 25 g/10 min or lower, and even more preferably 20 g/10 min or lower, from the same viewpoint as above.

Furthermore, when the laminated film of the present invention is wound into a roll, it is preferable to include an olefin resin containing a 4-methyl-1-pentene copolymer, in order to suppress blocking with the resin layer A and to further suppress contamination during the processing steps.

Examples of olefin resins containing the above-mentioned 4-methyl-1-pentene units include Mitsui Chemicals' "TPX®" DX310, "TPX®" DX231, "TPX®" MX004, "Absortomer®" EP-1013, and "Absortomer®" EP-1001, among others. In particular, a 4-methyl-1-pentene/α-olefin copolymer as disclosed in Japanese Patent Application Publication No. 2013-194132 is preferably used. The content of the above-mentioned olefin resin containing the 4-methyl-1-pentene units is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on 100% by mass of the resin in the base layer and resin layer B. Furthermore, from the viewpoint of ensuring adhesion with the low-melting-point alloy, the content of the 4-methyl-1-pentene/α-olefin copolymer is preferably 30% by mass or less, and more preferably 20% by mass or less, of 100% by mass of the resin in the base layer and resin layer B. By including an olefin resin containing the 4-methyl-1-pentene copolymer in the base layer and resin layer B, when the laminated film of the present invention is used as a surface protective film, good adhesion with the low-melting-point alloy cast on the base layer and resin layer B is maintained, while blocking with resin layer A is suppressed when wound into a roll, allowing for easy unwinding.

The materials constituting the resin of the base layer and resin layer B are preferably lubricants such as silicone resins, fluororesins, fatty acid metal salts, fatty acid amides, inorganic particles, and organic particles, from the viewpoint of suppressing blocking with resin layer A. In particular, from the viewpoint of improving transportability and unwinding from a roll state, it is preferable to use inorganic particles or organic particles. For example, the materials constituting the resin of the base layer and resin layer B preferably contain 0.5 to 5% by mass of organic particles made of ultra-high molecular weight polyethylene, when the entire resin layer having a surface opposite to the surface on the side of resin layer A is considered as 100% by mass. When organic particles made of ultra-high molecular weight polyethylene are used, they have higher compatibility with the base layer and resin layer B compared to other particles, making them easy to disperse, and reducing the likelihood of particle detachment during transport and customer use processes. In particular, from the viewpoint of improving transportability, unwinding from a roll state, and suppressing blocking with resin layer A, the average particle size of the organic particles is preferably 1 to 20 μm. From a similar viewpoint, 5 to 20 μm is more preferable, and 9 to 20 μm is even more preferable. If the average particle size is less than 1 μm, the surface roughness of the base layer and resin layer B becomes small, which may result in insufficient transportability and unwinding from a roll. If the average particle size exceeds 20 μm, when wound into a roll, the protrusions of the base layer and resin layer B may bite into the resin layer A, worsening blocking and making unwinding difficult, or the protrusions may be transferred to the resin layer A, reducing the adhesive strength of the resin layer A. From a similar viewpoint, when the entire base layer and resin layer B is considered as 100% by mass, the content of the above particles is more preferably 0.5 to 4% by mass, and even more preferably 1 to 2% by mass. If the content is less than 0.5% by mass, the surface roughness becomes small, which may reduce transportability and unwinding from a roll. Furthermore, if it exceeds 5% by mass, the protrusions of the base layer and resin layer B may bite into the resin layer A, causing blocking and making unwinding difficult, or the protrusion shape of the particles may be transferred to the surface of the resin layer A, increasing the surface roughness of the resin layer A and reducing the adhesive strength.

Here, the average particle size of inorganic and organic particles is measured using the equivalent circle diameter obtained by image processing from transmission electron microscope images of the particles. The equivalent circle diameter is measured for 50 particles, and the average value is taken as the average particle size. Here, "ultra-high molecular weight polyethylene" refers to polyethylene with a weight-average molecular weight of 1 million or more, as measured by gel permeation chromatography.

Furthermore, in this invention, fine particles of "Mipelon®" PM-200 can preferably be used as the ultra-high molecular weight polyethylene.

Next, the method for manufacturing the laminated film of the present invention will be described.

The method for manufacturing the laminated film of the present invention is not particularly limited. For example, in the case of a three-layer laminated structure having a resin layer A, a base layer, and a layer (resin layer B) containing the surface opposite to the surface on the side of resin layer A, examples include a so-called co-extrusion method in which the resin compositions constituting each layer are melt-extruded from separate extruders and laminated together in a die, or a method in which the resin layer A, base layer, and the layer (resin layer B) containing the surface opposite to the surface on the side of resin layer A are melt-extruded individually and then laminated by a lamination method. However, from the viewpoint of productivity, it is preferable to manufacture by co-extrusion. The materials constituting each layer may be purchased materials used as is, or mixed using a Henschel mixer or the like, or all or part of the materials for each layer may be kneaded in advance. Regarding co-extrusion, known methods such as the inflation method and the T-die method can be used, but from the viewpoint of excellent thickness accuracy and surface shape control, the T-die method of hot-melt co-extrusion is particularly preferred.

When manufactured by co-extrusion, the components of resin layer A, the base layer, and the layer (resin layer B) including the surface opposite to the surface of resin layer A are each extruded from a melt extruder, laminated and integrated inside a T-die, and co-extruded. The film is then cooled and solidified with a metal cooling roll, formed into a film, and wound into a roll to obtain a laminated film. The form of winding into a roll is not particularly limited; the laminated film alone may be wound, or a release liner may be attached separately to the resin layer A side of the laminated film before winding into a roll. However, from the viewpoint of cost and productivity, it is more preferable to wind only the laminated film of the present invention into a roll with the base layer and resin layer B in contact with the surface of the layer including the surface with resin layer A and the opposite surface (in this case, the surface opposite to the surface of resin layer A).

The laminated film of the present invention can be used as a surface protection film to prevent scratches and dirt from adhering during the manufacturing, processing, and transportation of synthetic resin plates, metal plates, glass plates, etc. It is particularly preferable to use it as a surface protection film for adherends with curved shapes, such as optical instruments and eyeglass lenses, and is most preferably used as a surface protection film for eyeglass lenses.

In this invention, from the viewpoint of preventing damage and contamination during manufacturing, processing, and transportation, it is preferable that the molded body has the laminated film of the present invention. Examples of the molded body include synthetic resin plates, metal plates, and glass plates.

Furthermore, in the present invention, it is preferable that the manufacturing process of the molded article includes, in this order, a step of attaching the laminated film of the present invention, a step of processing the molded article, and a step of peeling off the laminated film.

Examples of the aforementioned processing methods include cutting, punching, bending, polishing, surface modification, bonding, and lamination.

When the laminated film of the present invention is used as a surface protection film for eyeglass lenses, it can be used in processes such as the following. In eyeglass lenses, polishing is performed as necessary for surface finishing. This polishing process involves casting a low-melting-point alloy to the back of the lens polishing surface, integrating it with the lens. This block-shaped low-melting-point alloy is then mounted on a fixed shaft, and the rotating polishing surface is pressed against it for polishing. In this process, a removable surface protection film is applied to the back surface before casting the low-melting-point alloy to protect the lens surface and ensure adhesion with the alloy. The adhesive side of the surface protection film stretches when it adheres to the back surface of the lens during polishing, and has the effect of cutting the stretched film. After the polishing process, it can be easily peeled off. Furthermore, the surface opposite the adhesive side of the surface protection film has heat resistance that allows the low-melting-point alloy to be cast at a temperature above the alloy's melting point, and it has the effect of adhering to the cooled and solidified alloy.

The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. The measurement and evaluation of various physical properties were carried out by the following methods; unless otherwise specified, these were performed in a room at 23°C.

(1) Thickness Using the microtome method, ultrathin sections with a width of 5 mm and a cross-section in the width-thickness direction of the laminated film were prepared, and these sections were coated with platinum to serve as observation samples. Next, the cross-section of the laminated film was observed at an acceleration voltage of 2.5 kV using a Hitachi S-4800 field emission differential electron microscope, and the thickness of the substrate layer, resin layer A, and the layer including the surface opposite to the surface on the side of resin layer A (resin layer B) was measured from an arbitrary point in the observation image. The observation magnification was 5,000x when measuring the thickness of resin layer A and the layer including the surface opposite to the surface on the side of resin layer A (resin layer B), and 1,000x when measuring the thickness of the substrate layer. Furthermore, the same measurement was performed a total of 10 times, and the arithmetic mean was used as the thickness of the substrate layer, resin layer A, and the layer including the surface opposite to the surface on the side of resin layer A (resin layer B), respectively.

(2) Melt flow rate (MFR)
Using a melt indexer manufactured by Toyo Seiki Seisakusho, the MFR of the raw materials used in the examples and comparative examples was measured in accordance with JIS K7210-1 (2014) under conditions of a temperature of 230°C and a load of 2.16 kg, or a temperature of 190°C and a load of 2.16 kg.

(3) Shear Storage Modulus Samples were obtained by melt-molding pellets made from the styrene-based elastomer and olefin-based elastomer used in the examples and comparative examples to a thickness of 1 mm. Measurements were performed using a TA Instruments AR2000ex rheometer. The temperature was lowered from 200°C to -20°C at a rate of 20°C/min, and then dynamically sheared at a frequency of 1 Hz and strain of 0.01% while raising the temperature from -20°C to 40°C at a rate of 10°C/min. The storage modulus G'(25) at 25°C during the heating process was evaluated.

(4) Maximum tensile modulus at 20% to 100% tension Using a tensile testing machine (Orientec universal testing machine "Tensilon®"), in accordance with JIS K 7113-1995, five tensile tests were performed on the laminated film in the extrusion direction (MD direction) at a temperature of 23°C and a speed of 300 mm/min. The maximum tensile modulus at 20% to 100% tension was calculated for each, and the average value was taken as the maximum tensile modulus of the laminated film at 20% to 100% tension. The test specimens used for measurement were strips with a width of 10 mm and a length of 100 mm, and the measurement was performed with a chuck distance of 50 mm.

(5) Tear strength (Trouser method)
In accordance with JIS K7128-1:1998, laminated film was cut to a width of 50 mm x length of 150 mm. A half-cut was made in the center of the cut film width, and the tear strength was measured using a tensile testing machine (Orientec universal testing machine "Tensilon®"). The measurement was performed five times in the extrusion direction (MD direction) of the laminated film, and the average value was taken as the tear strength of the laminated film.

(6) MD/TD stress ratio at 100% tensile strength Using a tensile testing machine (Orientec's universal testing machine "Tensilon®"), in accordance with JIS K 7113-1995, five tensile tests were performed on the laminated film in the extrusion direction (MD direction) and width direction (TD direction) at a temperature of 23°C and a speed of 300 mm/min. The average value of the stress at 100% tensile strength was used as the tensile stress of each laminated film, and the MD/TD stress ratio at 100% tensile strength was calculated by dividing the MD tensile stress by the TD tensile stress. The test specimens used for measurement were strip-shaped with a width of 10 mm and a length of 100 mm, and the measurement was performed with a chuck distance of 50 mm.

(7) Water Contact Angle An automatic contact angle meter (DM-501) manufactured by Kyowa Interface Science Co., Ltd. and analysis software FAMAS were used to measure the water contact angle of the surface opposite to the surface of resin layer A. Pure water was used for the measurement, and the amount of pure water dropped was 2 microliters. The measurement was performed five times, and the average value was taken as the water contact angle of the laminated film.

(8) Maximum tack F of polycarbonate probe
The cut samples were aged for 24 hours in an atmosphere of 23°C. Using a Lesca TAC1000 tacking tester, a 5 mm diameter polycarbonate probe was brought into contact with the surface of resin layer A of the laminated film under the following conditions. The maximum load when the probe was peeled off was read, and the stress per unit area was calculated by dividing this by the probe area. The test was performed five times for each type of laminated film, and the average value was defined as the maximum probe tack value F on the resin layer A side of the laminated film.
Temperature: 23℃
Holding time after sample placement: 5 minutes; Contact speed, peeling speed: 2 mm/second; Pressing load: 2.94 N
Contact time: 2 seconds. Probe model number: φ5mm PC probe for tacking test machine (TAC1000).

(9) Peel strength after storage at 23°C The surface of the resin layer A side of a laminated film cut to a size of 150 mm in the MD direction and 25 mm in the TD direction was attached to a stainless steel plate (SUS430BA treated, thickness 0.5 mm) measuring 200 mm vertically and 40 mm horizontally using a roll press machine (special pressure roller manufactured by Yasuda Seiki Seisakusho) at 23°C with a bonding pressure of 0.1 MPa. Next, the surface of the resin layer A side of a laminated film cut to a size of 150 mm in the MD direction and 25 mm in the TD direction was placed on the surface (base layer or resin layer B) opposite to the surface of the bonded sample's resin layer A side, and attached using a roll press machine (special pressure roller manufactured by Yasuda Seiki Seisakusho) at 23°C with a bonding pressure of 0.1 MPa. After that, 50 mm of the laminated film that was not in contact with the stainless steel plate was peeled off. Next, after 24 hours of storage in a 23°C room, a tensile testing machine (Orientec's universal testing machine "Tensilon®") was used. The stainless steel plate was gripped with the lower chuck, and the laminated film was peeled 50 mm away with the upper chuck. A peel test was performed in the MD direction at a tensile speed of 300 mm/min and a peel angle of 180°. Five tests were performed on each type of laminated film, and the arithmetic mean was defined as the peel force of the laminated film after storage at 23°C.

<Raw materials>
- SEBS-1: Commercially available styrene elastomer (SEBS manufactured by Kraton, "Kraton®" G1645, MFR 3.3 g/10 min (measured at 230°C), G'(25) 0.4 MPa)
- SEBS-2: Commercially available styrene elastomer (SEBS manufactured by Asahi Kasei, "ToughTec®" H1052, MFR 13 g/10 min (measured at 230°C), G'(25) 1.8 MPa)
• Terpene phenol resin: Commercially available tackifier (Yasuhara Chemical's Terpene Phenolic YS Polystar U UH115)
PE-1: Commercially available low-density polyethylene (MFR of 5.0 g/10 min (measured at 190°C), density of 931 kg/ ^m³ )
PE-2: Commercially available linear low-density polyethylene (MFR of 0.4/10 min (measured at 190°C), density 928 kg/ ^m³ )
PE-3: Commercially available linear low-density polyethylene (MFR of 3.8 g/10 min (measured at 190°C), density 903 kg/ ^m³ )
PE-4: Commercially available high-density polyethylene (MFR 5.0/10 min (measured at 190°C), density 950 kg/ ^m³ )
• PE-5: Commercially available low-density polyethylene (MFR of 15 g/10 min (measured at 190°C), density 900 kg/ ^m³ ) • Olefin resin-1: Olefin resin containing 4-methyl-1-pentene units (Mitsui Chemicals "Absortomer®" EP-1001, MFR of 10 g/10 min (measured at 230°C))
Pigment MB: A pigment masterbatch consisting of PE-1 95% by mass, phthalocyanine blue 3% by mass, and titanium dioxide 2% by mass. EMAA: Ethylene-methacrylic acid copolymer.
(Nucrel® AN4213C manufactured by Mitsui Dow Polychemicals (acid content of 11% by mass calculated by FT-IR method, MFR of 10 g/10 min (measured at 190°C))
・PE particle MB: A PE particle masterbatch consisting of 90% by mass of PE-1 and 10% by mass of polyethylene particles with an average particle diameter of 10 μm (Mitsui Chemicals'"Mipelon®" PM-200). ・Olefin resin-2: An olefin resin containing 4-methyl-1-pentene units (Mitsui Chemicals'"Absortomer®" EP-1013, MFR of 10 g/10 min (measured at 230°C)).

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

Resin layer A: 80% by mass of G1645 and 20% by mass of UH115 were used, pre-mixed and chipped using a twin-screw extruder.

Substrate layer: 70% by mass of PE-1 and 30% by mass of PE-2 were used.

The layer (resin layer B) including the surface opposite to the surface on side of resin layer A: 85% by mass of EMAA, 10% by mass of PE particles MB, and 5% by mass of olefin-based resin-2 were used.

Next, the constituent resins for each layer were fed into the three extruders of a T-die composite film-forming machine. The discharge rate of each extruder was adjusted so that resin layer A was 15 μm thick, the substrate layer was 95 μm thick, and the layer including the surface opposite to the surface of resin layer A was 10 μm thick. The layers were then laminated in this order and extruded from the composite T-die at an extrusion temperature of 200°C. The resulting film was cast onto a roll with a controlled surface temperature of 40°C, and the formed film was wound onto the roll to obtain a laminated film.

(Examples 2 to 8, Comparative Examples 1 to 4)
A laminated film was obtained in the same manner as in Example 1, except that the compositions were as shown in the table. The evaluation results are shown in the table.

(Example 9)
The composition constituting resin layer A consisted of 80% by mass of G1645 and 20% by mass of UH115, and the composition constituting the base layer consisted of 75% by mass of EMAA, 10% by mass of PE-2, 10% by mass of PE particles MB, and 5% by mass of olefin resin-2. The materials were fed into each extruder of a T-die composite film-making machine having two extruders, and the discharge rate of each extruder was adjusted so that resin layer A was 15 μm thick and the base layer was 105 μm thick. The layers were laminated in this order and extruded from the composite T-die at an extrusion temperature of 200°C. The resulting film was cast onto a roll with a surface temperature controlled to 40°C, molded into a film shape, and wound up to obtain a laminated film. The evaluation results are shown in the table.

The laminated film of the present invention has sufficient adhesion and conformability to the adherend, and therefore can be preferably used as a surface protection film for products made of various materials such as synthetic resins, metals, and glass.

Claims (5)

A laminated film having an adhesive resin layer A and a base layer,
The resin layer A contains 60 to 90% by mass of styrene-based elastomer and 10 to 40% by mass of terpene-based resin in 100% by mass.
The maximum polycarbonate probe tack F on the surface of resin layer A is 0.098 to 0.245 N/ ^mm² .
A laminated film that satisfies (a) and (b) below.
(a) Maximum tensile modulus of elasticity at 20% to 100% elongation in the extrusion direction (MD) is 1.0 to 20 MPa
(b) Tear strength in the extrusion direction (MD) of 4.9 to 49 N/mm The laminated film according to claim 1, wherein the stress ratio (stress in MD / stress in TD) between the extrusion direction (MD) and the width direction (TD) at 100% elongation is 1.0 to 2.0. The laminated film according to claim 1 or 2, wherein the water contact angle of the surface opposite to the surface on the side of resin layer A is 90° or more and 110° or less. A laminated film according to any one of claims 1 to 3, wherein the surface on the side of resin layer A and the surface opposite to the surface on the side of resin layer A are bonded at a pressure of 0.1 MPa, and the 180° peel strength after 24 hours of storage is 5.88 N/ 25 mm or less. A laminated film according to any one of claims 1 to 4 , wherein the base layer contains a coloring agent.