Surface Protection Film

Abstract

To provide a surface protective film capable of preventing a surface protective film from breaking in a hot press during a process of hot-pressing, by a metal mold, a resin substrate with the surface protective film adhered thereon, and preventing a surface of the resin substrate from becoming orange peel-like after the hot press, the surface protective film having appropriate softness that allows the process of hot-pressing to operate smoothly, and capable of being adhered onto the resin substrate.SOLUTION: A surface protective film includes a substrate layer (A) and an adhesive layer (B). The substrate layer (A) includes a substrate layer (A1). The substrate layer (A1) is an outermost layer opposite to the adhesive layer (B) of the substrate layer (A). In the substrate layer (A1), a friction force at 130°C is 4.5 N or less, and a storage elastic modulus at 120°C is 50 MPa or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a surface protection film. Typically, the present invention relates to a surface protection film used in the manufacture of a member provided in a mobile device. [Background technology]

[0002] In recent years, the performance of mobile communications in so-called mobile devices such as smartphones, tablet terminals, and laptops has been rapidly improving. In particular, new high-performance mobile communications standards (e.g., 5G standards) that enable ultra-high speed, ultra-large capacity, ultra-low latency, and ultra-massive connections are being adopted.

[0003] In order to fully utilize the performance of these new high-performance mobile communications, the housings of mobile devices need to be made of materials that are less susceptible to the effects of radio waves. For this reason, there is a need to replace the metal housings that have traditionally been used for mobile device housings with plastic housings and other materials that are less susceptible to the effects of radio waves.

[0004] On the other hand, in recent years, the design of mobile devices has improved significantly, and typically, mobile devices having housings with three-dimensional curved structures have become common.

[0005] When the housing of a mobile device is made of metal, established metal processing technology makes it possible to create housings with a variety of three-dimensional curved structures.

[0006] On the other hand, when the housing of a mobile device is made of resin, three-dimensional curved surface processing technology for the resin substrate is required, but there are currently many problems with this.

[0007] In general, a heat press is used to process a resin substrate. In this heat press, the resin substrate is sandwiched between dies designed to form a desired shape and pressed at high temperature. At this time, surface protection films are attached to both surfaces of the resin substrate to protect the surface of the resin substrate.

[0008] However, when conventional surface protection films are used in hot pressing of resin substrates, there is a problem in that the surface protection film cannot smoothly conform to the mold during curved processing by pressing at high temperatures, making the surface protection film prone to tearing.

[0009] Furthermore, when a conventional surface protection film (Patent Document 1) is used for hot pressing of a resin substrate, the surface protection film is prone to shifting in position due to pressing at high temperatures, resulting in the problem of orange peel (marks) on the surface of the resin substrate after pressing.

[0010] Furthermore, in order to process a resin substrate into a three-dimensional curved surface by heat pressing, the surface protection films attached to both surfaces of the resin substrate must have an appropriate softness. That is, if the surface protection films attached to both surfaces of the resin substrate are too hard, it becomes difficult for them to follow the three-dimensional curved shape of the mold, and if the surface protection films attached to both surfaces of the resin substrate are too soft, the surface protection films will be displaced or wrinkled (Patent Document 1). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 5-302068 Summary of the Invention [Problem to be solved by the invention]

[0012] The object of the present invention is to provide a surface protection film that can be adhered to a resin substrate, which can suppress tearing of the surface protection film during heat pressing in a mold to which the resin substrate has been adhered, can suppress orange peel on the surface of the resin substrate after the heat pressing, and has appropriate softness to allow the heat pressing process to be carried out smoothly. [Means for solving the problem]

[0013] The surface protective film in an embodiment of the present invention is A surface protection film having a base layer (A) and a pressure-sensitive adhesive layer (B), The substrate layer (A) includes a substrate layer (A1), the base layer (A1) is the outermost layer of the base layer (A) on the opposite side to the pressure-sensitive adhesive layer (B), The frictional force of the base layer (A1) at 130°C is 4.5 N or less, The storage modulus at 120°C is 50 MPa or less.

[0014] In one embodiment, the surface protection film according to the embodiment of the present invention has a total thickness of 20 μm to 180 μm.

[0015] In one embodiment, the entire thickness of the base layer (A) is 10 μm to 150 μm.

[0016] In one embodiment, the thickness of the base layer (A1) is 1 μm to 60 μm.

[0017] In one embodiment, the substrate layer (A1) has a maximum peak temperature of 130° C. or higher as measured by DSC.

[0018] In one embodiment, the substrate layer (A1) contains a release agent.

[0019] In one embodiment, the content of the release agent in the base layer (A1) is 0.1% by weight to 30% by weight.

[0020] In one embodiment, the release agent comprises a silicone-based release agent.

[0021] In one embodiment, the silicone release agent comprises a silylated polyolefin.

[0022] In one embodiment, the substrate layer (A1) contains at least one resin selected from the group consisting of ethylene-based resins and propylene-based resins.

[0023] In one embodiment, the ethylene-based resin comprises high density polyethylene.

[0024] In one embodiment, the propylene-based resin includes at least one selected from random polypropylene, block polypropylene, and homopolypropylene.

[0025] In one embodiment, the substrate layer (A1) contains a pentene resin.

[0026] In one embodiment, the substrate layer (A) includes the substrate layer (A1) and the substrate layer (A2) in this order.

[0027] In one embodiment, the base layer (A2) contains an ethylene-based resin.

[0028] In one embodiment, the ethylene-based resin includes at least one selected from low-density polyethylene and ethylene-vinyl acetate copolymer.

[0029] In one embodiment, the base layer (A2) contains a propylene-based resin.

[0030] In one embodiment, the propylene-based resin comprises homopolypropylene.

[0031] In one embodiment, the substrate layer (A) includes the substrate layer (A1), the substrate layer (A2), and the auxiliary substrate layer (A3) in this order.

[0032] In one embodiment, the error between the thickness of the auxiliary substrate layer (A3) and the thickness of the substrate layer (A1) is ±50% or less.

[0033] In one embodiment, the main component resin contained in the auxiliary substrate layer (A3) is the same as the main component resin contained in the substrate layer (A1).

[0034] In one embodiment, the surface protection film according to the embodiment of the present invention is used in the manufacture of a member provided in a mobile device.

[0035] In one embodiment, the surface protection film according to the embodiment of the present invention is used to protect the surface of a resin board when the resin board is subjected to hot press processing.

[0036] In one embodiment, the heating temperature during the hot press processing is 50°C to 250°C. Effect of the Invention

[0037] According to the present invention, in a process of hot pressing a resin substrate to which a surface protection film is attached in a mold, it is possible to provide a surface protection film that can be attached to a resin substrate, which can suppress tearing of the surface protection film during the hot pressing, can suppress orange peel on the surface of the resin substrate after the hot pressing, and has an appropriate softness to allow the hot pressing process to be carried out smoothly. [Brief description of the drawings]

[0038] [Figure 1] 1 is a schematic cross-sectional view of a surface protection film according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a surface protection film according to another embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic cross-sectional view of a surface protection film according to yet another embodiment of the present invention. [Figure 4] FIG. 2 is an explanatory diagram showing a method for evaluating high-temperature slipperiness. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] ≪≪1. Surface protection film≫≫ The surface protection film in an embodiment of the present invention is a surface protection film having a substrate layer (A) and a pressure-sensitive adhesive layer (B), the substrate layer (A) includes a substrate layer (A1), and the substrate layer (A1) is the outermost layer of the substrate layer (A) on the side opposite the pressure-sensitive adhesive layer (B).

[0040] The surface protective film in the embodiment of the present invention may include any appropriate other layer as long as the effect of the present invention is not impaired.

[0041] The substrate layer (A) preferably consists of two or more layers.

[0042] The substrate layer (A) preferably includes a substrate layer (A1) and a substrate layer (A2) in this order.

[0043] The substrate layer (A) more preferably includes a substrate layer (A1), a substrate layer (A2) and an auxiliary substrate layer (A3) in this order.

[0044] The pressure-sensitive adhesive layer (B) may be a pressure-sensitive adhesive layer consisting of only one layer, or may be a pressure-sensitive adhesive layer consisting of a laminate of two or more layers.

[0045] The total thickness of the surface protection film in the embodiment of the present invention is preferably 20 μm to 180 μm. When the total thickness of the surface protection film in the embodiment of the present invention is within the above range, the effects of the present invention can be more effectively achieved. If the total thickness of the surface protection film in the embodiment of the present invention is too thin, when used in hot pressing of a resin substrate, the surface protection film may not be able to fully perform its role, and for example, the surface protection film may be easily displaced or wrinkled due to pressing at high temperatures. If the total thickness of the surface protection film in the embodiment of the present invention is too thick, when used in hot pressing of a resin substrate, the surface protection film may not be able to fully perform its role, and for example, it may be difficult to follow the shape of a mold.

[0046] In an embodiment of the present invention, when a thin thickness is required, the total thickness of the surface protection film is preferably 20 μm to 150 μm, more preferably 20 μm to 120 μm, even more preferably 20 μm to 100 μm, still more preferably 20 μm to 80 μm, particularly preferably 20 μm to 60 μm, and most preferably 30 μm to 50 μm.

[0047] In an embodiment of the present invention, when an appropriate thickness is required, the total thickness of the surface protection film is preferably 60 μm to 180 μm, more preferably 70 μm to 170 μm, even more preferably 80 μm to 160 μm, particularly preferably 85 μm to 150 μm, and most preferably 90 μm to 140 μm.

[0048] The total thickness of the substrate layer (A) is preferably 10 μm to 150 μm. When the total thickness of the substrate layer (A) is within the above range, the effects of the present invention can be more effectively achieved. If the total thickness of the substrate layer (A) is too thin, when used for hot pressing of a resin substrate, the role of the surface protection film may not be fully achieved, and for example, the surface protection film may be easily displaced or wrinkled due to pressing at high temperatures. If the total thickness of the substrate layer (A) is too thick, when used for hot pressing of a resin substrate, the role of the surface protection film may not be fully achieved, and for example, it may be difficult to follow the shape of a mold.

[0049] When a thin thickness is required, the total thickness of the base layer (A) is preferably 10 μm to 120 μm, more preferably 10 μm to 100 μm, even more preferably 10 μm to 80 μm, still more preferably 10 μm to 60 μm, particularly preferably 15 μm to 50 μm, and most preferably 20 μm to 40 μm.

[0050] When an appropriate thickness is required, the total thickness of the base layer (A) is preferably 50 μm to 150 μm, more preferably 65 μm to 140 μm, even more preferably 75 μm to 140 μm, particularly preferably 80 μm to 135 μm, and most preferably 85 μm to 135 μm.

[0051] In the embodiment of the present invention, the surface protective film has a frictional force of the slip heat resistant base layer (A1) at 130 ° C. of preferably 4.5 N or less, more preferably 4.0 N or less, even more preferably 3.5 N or less, particularly preferably 3.0 N or less, and most preferably 2.5 N or less. The lower limit of the frictional force is the smaller the better, and in reality, it is 0.1 N or more. If the frictional force of the slip heat resistant base layer (A1) at 130 ° C. in the embodiment of the present invention is within the above range, the effect of the present invention can be more effectively exhibited. In particular, if the frictional force of the slip heat resistant base layer (A1) at 130 ° C. in the embodiment of the present invention is within the above range, in the step of hot pressing the resin substrate to which the surface protective film is attached with a mold, the breakage of the surface protective film during the hot pressing can be more effectively suppressed. If the frictional force of the slip-resistant heat-resistant base layer (A1) in an embodiment of the present invention at 130°C is too large, when used in hot pressing of a resin substrate, the surface protection film may not be able to smoothly follow the mold during curved processing by pressing at high temperatures, and the surface protection film may be torn.

[0052] The surface protective film according to the embodiment of the present invention has a storage modulus at 120°C of preferably 50 MPa or less, more preferably 50 MPa to 0.5 MPa, even more preferably 50 MPa to 1 MPa, particularly preferably 45 MPa to 1.5 MPa, and most preferably 40 MPa to 2 MPa. If the storage modulus at 120°C of the surface protective film according to the embodiment of the present invention is within the above range, the surface protective film has appropriate softness, and when used in hot pressing of a resin substrate, good three-dimensional curved processing can be achieved. If the storage modulus at 120°C of the surface protective film according to the embodiment of the present invention is too low, the surface protective film is too soft, and there is a risk of the surface protective film being displaced or wrinkled. If the storage modulus at 120°C of the surface protective film according to the embodiment of the present invention is too high, the surface protective film is too hard, and there is a risk of it being difficult to follow the three-dimensional curved shape of a mold.

[0053] Fig. 1 is a schematic cross-sectional view of a surface protection film according to one embodiment of the present invention. In Fig. 1, a surface protection film 100 has a base layer (A) 10 and a pressure-sensitive adhesive layer (B) 20, and the outermost layer of the base layer (A) on the side opposite to the pressure-sensitive adhesive layer (B) is a base layer (A1) 11.

[0054] Fig. 2 is a schematic cross-sectional view of a surface protection film according to another embodiment of the present invention. In Fig. 2, the surface protection film 100 has a base material layer (A) 10 and a pressure-sensitive adhesive layer (B) 20, the outermost layer of the base material layer (A) opposite the pressure-sensitive adhesive layer (B) is a base material layer (A1) 11, and a base material layer (A2) 12 is provided between the base material layer (A1) 11 and the pressure-sensitive adhesive layer (B) 20. That is, the surface protection film 100 shown in Fig. 2 has the base material layer (A1) 11, the base material layer (A2) 12, and the pressure-sensitive adhesive layer (B) 20 in this order.

[0055] Fig. 3 is a schematic cross-sectional view of a surface protection film according to yet another embodiment of the present invention. In Fig. 3, the surface protection film 100 has a base layer (A) 10 and a pressure-sensitive adhesive layer (B) 20, the outermost layer of the base layer (A) opposite to the pressure-sensitive adhesive layer (B) is a base layer (A1) 11, a base layer (A2) 12 is between the base layer (A1) 11 and the pressure-sensitive adhesive layer (B) 20, and an auxiliary base layer (A3) 13 is between the base layer (A2) 12 and the pressure-sensitive adhesive layer (B) 20. That is, the surface protection film 100 shown in Fig. 3 has the base layer (A1) 11, the base layer (A2) 12, the auxiliary base layer (A3) 13, and the pressure-sensitive adhesive layer (B 20) in this order.

[0056] ≪1-1. Base material layer (A)≫ As shown in Figs. 1 to 3, the base layer (A) includes a base layer (A1) as the outermost layer on the side opposite to the pressure-sensitive adhesive layer (B).

[0057] The base layer (A) preferably includes a base layer (A1) and a base layer (A2) in this order, as shown in Figs. 2 and 3.

[0058] More preferably, the substrate layer (A) includes a substrate layer (A1), a substrate layer (A2) and an auxiliary substrate layer (A3) in this order, as shown in FIG.

[0059] The substrate layer (A) as a whole preferably contains an olefin resin as a main component. Specifically, the content of the olefin resin in the substrate layer (A) as a whole is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, even more preferably 95% by weight to 100% by weight, particularly preferably 98% by weight to 100% by weight, and most preferably substantially 100% by weight. When the substrate layer (A) as a whole contains an olefin resin as a main component, the effects of the present invention can be more effectively exhibited.

[0060] In this specification, the term "substantially 100% by weight" means that trace amounts of impurities and the like may be contained within a range that does not impair the effects of the present invention, and it is usually acceptable to refer to it as "100% by weight."

[0061] The olefin-based resin contained in the entire substrate layer (A) may be of one kind or of two or more kinds.

[0062] As the olefin resin, any suitable olefin resin may be adopted as long as it does not impair the effects of the present invention. In terms of being able to more effectively exhibit the effects of the present invention, such an olefin resin may be, for example, at least one selected from ethylene resin, propylene resin, butene resin, and pentene resin, and preferably at least one selected from ethylene resin, propylene resin, and pentene resin.

[0063] As the ethylene-based resin, any suitable ethylene-based resin may be adopted within a range that does not impair the effects of the present invention. Examples of such ethylene-based resins include at least one selected from low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene, medium-density polyethylene (MDPE), high-density polyethylene (HDPE), very high-density polyethylene, and copolymers of ethylene and other monomers (e.g., ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid ester copolymer, ethylene / butene-1 copolymer, ethylene / propylene / butene-1 copolymer, ethylene / α-olefin copolymer having 5 to 12 carbon atoms, ethylene / non-conjugated diene copolymer, etc.), and preferably at least one selected from high-density polyethylene, low-density polyethylene, and ethylene / vinyl acetate copolymer.

[0064] The ethylene-based resin may be a Ziegler-Natta ethylene-based resin obtained by using a Ziegler-Natta catalyst.

[0065] The ethylene-based resin may be a metallocene-based ethylene-based resin obtained by using a metallocene catalyst. Examples of such metallocene-based ethylene-based resins include at least one selected from metallocene-based low-density polyethylene and metallocene-based ethylene / vinyl acetate copolymers.

[0066] As the propylene-based resin, any appropriate propylene-based resin may be used as long as it does not impair the effects of the present invention. Examples of such propylene-based resins include at least one selected from random polypropylene, block polypropylene, homopolypropylene, and copolymers of propylene and other monomers.

[0067] The propylene-based resin may be a Ziegler-Natta propylene-based resin obtained by using a Ziegler-Natta catalyst.

[0068] The propylene-based resin may be a metallocene-based propylene-based resin obtained by using a metallocene catalyst. Examples of such metallocene-based propylene-based resins include at least one selected from metallocene-based random polypropylene, metallocene-based block polypropylene, metallocene-based homopolypropylene, and metallocene-based copolymers of propylene and other monomers.

[0069] As the butene-based resin, any appropriate butene-based resin may be used as long as it does not impair the effects of the present invention. Examples of such butene-based resins include at least one selected from polybutene-1 and copolymers of butene-1 and α-olefins.

[0070] The butene resin may be a Ziegler-Natta butene resin obtained by using a Ziegler-Natta catalyst.

[0071] The butene resin may be a metallocene-based butene resin obtained by using a metallocene catalyst.

[0072] As the pentene resin, any suitable pentene resin may be adopted within a range that does not impair the effects of the present invention. Examples of such pentene resins include at least one selected from poly(4-methylpentene-1), a copolymer of 4-methylpentene-1 and other monomers, poly(3-methylpentene-1), and a copolymer of 3-methylpentene-1 and other monomers. In terms of being able to further exhibit the effects of the present invention, the pentene resin may be at least one selected from poly(4-methylpentene-1) and a copolymer of 4-methylpentene-1 and other monomers, and a representative example is the product name "TPX (registered trademark)" manufactured by Mitsui Chemicals, Inc., which is a crystalline pentene resin made mainly from 4-methylpentene-1.

[0073] The pentene resin may be a Ziegler-Natta pentene resin obtained by using a Ziegler-Natta catalyst.

[0074] The pentene resin may be a metallocene-based pentene resin obtained by using a metallocene catalyst.

[0075] The substrate layer (A) may contain any other appropriate resin component as long as the effects of the present invention are not impaired.

[0076] <1-1-1. Base material layer (A1)> The base layer (A1) is the outermost layer of the base layer (A) on the opposite side to the pressure-sensitive adhesive layer (B).

[0077] The thickness of the substrate layer (A1) is preferably 1 μm to 60 μm. When the thickness of the substrate layer (A1) is within the above range, the effects of the present invention can be more effectively achieved. If the substrate layer (A1) is too thin, the heat resistance is poor, and when used for hot pressing of a resin substrate, the surface protection film may easily adhere to a mold due to melting or the like, and the surface protection film may easily become displaced or wrinkled due to pressing at high temperatures. If the substrate layer (A1) is too thick, when used for hot pressing of a resin substrate, for example, it may be difficult to follow the shape of a mold.

[0078] When a thin thickness is required, the thickness of the base layer (A1) is preferably 1 μm to 50 μm, more preferably 1 μm to 40 μm, even more preferably 1 μm to 30 μm, still more preferably 1 μm to 20 μm, particularly preferably 2 μm to 10 μm, and most preferably 3 μm to 8 μm.

[0079] When an appropriate thickness is required, the thickness of the base layer (A1) is preferably 2 μm to 60 μm, more preferably 3 μm to 50 μm, further preferably 4 μm to 40 μm, and particularly preferably 5 μm to 30 μm.

[0080] The substrate layer (A1) may consist of only one layer, or may consist of two or more layers. When the substrate layer (A1) consists of two or more layers, each layer may have the same composition, or at least one layer may be a different layer.

[0081] The substrate layer (A1) preferably has 1 to 5 layers, more preferably 1 to 3 layers, further preferably 1 or 2 layers, and particularly preferably 1 layer.

[0082] The maximum peak temperature of the substrate layer (A1) measured by DSC is preferably 130° C. or higher. If the maximum peak temperature of the substrate layer (A1) measured by DSC is within the above range, the substrate layer (A1) can have excellent heat resistance, and therefore the effects of the present invention can be more effectively achieved. If the maximum peak temperature of the substrate layer (A1) measured by DSC is too low, the substrate layer (A1) has poor heat resistance, and when used for hot pressing of a resin substrate, the surface protection film may easily adhere to a mold due to melting or the like, and the surface protection film may easily shift or wrinkle due to pressing at high temperatures. If the maximum peak temperature of the substrate layer (A1) measured by DSC is too high, the surface protection film may have difficulty following the three-dimensional curved shape of the mold when used for hot pressing of a resin substrate.

[0083] The maximum peak temperature of the base layer (A1) measured by DSC is preferably 150° C. or higher, more preferably 160° C. or higher, even more preferably 180° C. or higher, particularly preferably 200° C. or higher, and most preferably 220° C. or higher, in terms of improving heat resistance to hot pressing and thereby enabling the effects of the present invention to be more effectively exhibited. The upper limit of the maximum peak temperature of the base layer (A1) measured by DSC is preferably 500° C. or lower, more preferably 400° C. or lower, even more preferably 350° C. or lower, particularly preferably 300° C. or lower, and most preferably 250° C. or lower, in terms of preventing problems in processing.

[0084] The maximum peak temperature of the base layer (A1) as measured by DSC is preferably 130°C to 300°C, more preferably 130°C to 250°C, even more preferably 130°C to 220°C, particularly preferably 130°C to 200°C, and most preferably 130°C to 180°C, in terms of maintaining heat resistance to hot press while facilitating processing.

[0085] The substrate layer (A1) may contain any appropriate resin within the range that does not impair the effects of the present invention. The substrate layer (A1) preferably contains at least one selected from ethylene-based resins, propylene-based resins, butene-based resins, and pentene-based resins. If the substrate layer (A1) does not contain at least one selected from ethylene-based resins, propylene-based resins, butene-based resins, and pentene-based resins, the heat resistance of the outermost surface of the substrate layer (A) may be poor, and when the surface protection film in the embodiment of the present invention is used for hot pressing of a resin substrate, the surface protection film may be easily adhered to a mold due to melting, etc., and the surface protection film may be easily displaced or wrinkled due to pressing at high temperatures.

[0086] 1-1-1-1. Preferred embodiment 1 of the substrate layer (A1) In a preferred embodiment 1 of the substrate layer (A1), the substrate layer (A1) more preferably contains at least one selected from an ethylene-based resin and a propylene-based resin. When the substrate layer (A1) contains at least one selected from an ethylene-based resin and a propylene-based resin, the effects of the present invention can be more effectively exhibited. In particular, when the substrate layer (A1) contains at least one selected from an ethylene-based resin and a propylene-based resin, the outermost surface of the substrate layer (A) can have excellent heat resistance, so that the effects of the present invention can be more effectively exhibited.

[0087] The content ratio of at least one selected from ethylene-based resins and propylene-based resins that can be contained in the base layer (A1) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, even more preferably 95% by weight to 100% by weight, particularly preferably 98% by weight to 100% by weight, and most preferably substantially 100% by weight. If the content ratio of at least one selected from ethylene-based resins and propylene-based resins in the base layer (A1) is within the above range, the effects of the present invention can be more effectively exhibited. In particular, if the content ratio of at least one selected from ethylene-based resins and propylene-based resins in the base layer (A1) is within the above range, the outermost surface of the base layer (A) can have excellent heat resistance, so that the effects of the present invention can be more effectively exhibited. If the content ratio of at least one selected from ethylene-based resins and propylene-based resins in the base layer (A1) is outside the above range, the heat resistance of the outermost surface of the base layer (A) may be poor. When the surface protection film in the embodiment of the present invention is used for hot pressing of a resin substrate, the surface protection film may be more likely to adhere to the mold due to melting, etc., and the surface protection film may be more likely to shift in position or wrinkle when pressed at high temperatures.

[0088] As the ethylene-based resin that can be contained in the base layer (A1), any suitable ethylene-based resin can be adopted within the scope that does not impair the effects of the present invention. Examples of such ethylene-based resins include at least one selected from low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene, medium-density polyethylene (MDPE), high-density polyethylene (HDPE), very high-density polyethylene, and copolymers of ethylene and other monomers (e.g., ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid ester copolymer, ethylene / butene-1 copolymer, ethylene / propylene / butene-1 copolymer, ethylene / α-olefin copolymer having 5 to 12 carbon atoms, ethylene / non-conjugated diene copolymer, etc.), preferably at least one selected from high-density polyethylene, low-density polyethylene, and ethylene / vinyl acetate copolymer, more preferably high-density polyethylene.

[0089] The ethylene-based resin that may be contained in the substrate layer (A1) may be a Ziegler-Natta ethylene-based resin obtained by using a Ziegler-Natta catalyst.

[0090] The ethylene-based resin that can be contained in the substrate layer (A1) may be a metallocene-based ethylene-based resin obtained by using a metallocene catalyst. Examples of such metallocene-based ethylene-based resins include at least one selected from metallocene-based low-density polyethylene and metallocene-based ethylene / vinyl acetate copolymers.

[0091] The ethylene-based resin that can be contained in the substrate layer (A1) may be a single type or a blend of two or more types.

[0092] As the ethylene-based resin that can be contained in the substrate layer (A1), a commercially available product may be used.

[0093] The propylene-based resin that can be contained in the base layer (A1) can be any suitable propylene-based resin within the scope that does not impair the effects of the present invention. Examples of such propylene-based resins include at least one selected from random polypropylene, block polypropylene, homopolypropylene, and copolymers of propylene and other monomers.

[0094] The propylene-based resin that can be contained in the substrate layer (A1) may be a single type or a blend of two or more types.

[0095] Representative examples of homopolypropylene include isotactic homopolypropylene, atactic homopolypropylene, and syndiotactic homopolypropylene.

[0096] As the copolymer of propylene and other monomers, any appropriate copolymer can be adopted within the scope that does not impair the effects of the present invention. Examples of such copolymers of propylene and other monomers include propylene / ethylene copolymer, propylene / ethylene / 1-butene copolymer, and propylene / α-olefin copolymer having 5 to 12 carbon atoms.

[0097] The propylene-based resin that may be contained in the substrate layer (A1) may be a Ziegler-Natta propylene-based resin obtained by using a Ziegler-Natta catalyst.

[0098] The propylene-based resin that can be contained in the substrate layer (A1) may be a metallocene-based propylene-based resin obtained by using a metallocene catalyst. Examples of such metallocene-based propylene-based resins include at least one selected from metallocene-based random polypropylenes, metallocene-based block polypropylenes, metallocene-based homopolypropylenes, and copolymers of metallocene-based propylene and other monomers.

[0099] As the propylene-based resin that can be contained in the substrate layer (A1), commercially available products may be used.

[0100] The base layer (A1) preferably contains a release agent. When the base layer (A1) contains a release agent, the surface protection film can easily and smoothly conform to a mold during curved processing by pressing at high temperatures, and the surface protection film is less likely to tear.

[0101] The base layer (A1) may contain only one type of release agent, or two or more types.

[0102] As a means for incorporating a release agent into the base layer (A1), any appropriate means may be adopted as long as the effects of the present invention are not impaired. Examples of such means include a method of incorporating a release agent into the material (resin composition) for forming the base layer (A1) (by kneading, etc.), and a method of applying a coating liquid containing a release agent.

[0103] The content of the release agent in the base layer (A1) is preferably 0.1% by weight to 30% by weight, more preferably 0.1% by weight to 20% by weight, even more preferably 0.1% by weight to 15% by weight, particularly preferably 0.1% by weight to 10% by weight, and most preferably 0.1% by weight to 7.5% by weight. When the content of the release agent in the base layer (A1) is within the above range, the surface protection film can more smoothly conform to the mold during curved surface processing by pressing at high temperature, and the surface protection film is less likely to break.

[0104] As the release agent that can be contained in the base layer (A1), any appropriate release agent can be adopted as long as it does not impair the effects of the present invention. In order to further exhibit the effects of the present invention, it is preferable to select a release agent that has good miscibility and adhesion with the resin component contained in the base layer (A1).

[0105] Examples of release agents that may be contained in the substrate layer (A1) include ethylene-vinyl alcohol copolymers, fatty acid amide-based additives, low molecular weight polyolefin waxes, long-chain alkyl-based additives, polymethylpentene, and silicone-based release agents.

[0106] Examples of the ethylene-vinyl alcohol copolymer include ethylene-vinyl alcohol copolymers obtained by saponifying copolymers of ethylene with vinyl acetate, vinyl formate, vinyl propionate, and vinyl acetate.

[0107] Examples of the fatty acid amide additives include saturated fatty acid bisamides, unsaturated fatty acid bisamides, aromatic bisamides, and substituted ureas.Specific examples of the fatty acid amide additives include methylene bisstearic acid amide, ethylene bisstearic acid amide, ethylene bisoleic acid amide, N,N-dioleyl adipic acid amide, and N-stearyl-N'-stearyl urea, etc.

[0108] Examples of the low molecular weight polyolefin wax include low molecular weight waxes such as polyethylene wax and polypropylene wax.

[0109] Examples of the long-chain alkyl additive include low molecular weight additives having alkyl chains, such as Peloil (registered trademark) 1010 and Peloil (registered trademark) 1010S (both manufactured by Ipposha Yushi Kogyo Co., Ltd.).

[0110] Examples of the polymethylpentene include crystalline olefin polymers made mainly from 4-methylpentene-1, such as TPX (registered trademark) MX001 and TPX (registered trademark) MX004 (both manufactured by Mitsui Chemicals, Inc.).

[0111] Examples of the silicone-based release agent include silylated polyolefin, silicone resin, silicone alkoxy oligomer, silicone oligomer, silicone master pellet, silicone rubber powder, silicone emulsion, etc. Examples of the silylated polyolefin include silylated polyolefin prepared by the method shown in the examples of JP2011-26448A.

[0112] As the release agent, at least one selected from long-chain alkyl additives and silicone-based release agents is preferred, and silicone-based release agents are more preferred, in that this allows the surface protection film to conform more smoothly to the mold during curved surface processing by pressing at high temperatures and makes the surface protection film less likely to tear.

[0113] Among silicone-based release agents, silylated polyolefins are preferred because they enable the surface protection film to conform more smoothly to the mold during curved surface processing by pressing at high temperatures and make the surface protection film less susceptible to tearing.

[0114] The substrate layer (A1) may contain any other appropriate resin component as long as the effects of the present invention are not impaired.

[0115] The substrate layer (A1) may contain any suitable additive as necessary. Examples of additives that may be contained in the substrate layer (A1) include ultraviolet absorbers, heat resistance stabilizers, fillers, lubricants, colorants (dyes, etc.), antioxidants, eye plug inhibitors, antiblocking agents, foaming agents, and polyethyleneimines. These may be used alone or in combination of two or more. The content of the additives in the substrate layer (A1) is preferably 10% by weight or less, more preferably 7% by weight or less, even more preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

[0116] Examples of the ultraviolet absorbing agent include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. The content of the ultraviolet absorbing agent may be any appropriate content as long as it does not bleed out during molding. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably propylene-based resin) in the base layer (A1).

[0117] Examples of the heat resistance stabilizer include hindered amine compounds, phosphorus compounds, and cyanoacrylate compounds. The content of the heat resistance stabilizer may be any appropriate content as long as it does not bleed out during molding. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably propylene resin) in the base layer (A1).

[0118] Examples of the filler include inorganic fillers such as talc, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, silica, clay, mica, barium sulfate, whiskers, and magnesium hydroxide. The average particle size of the filler is preferably 0.1 μm to 20 μm. The content of the filler may be any appropriate content. Typically, the content is preferably 1% by weight to 200% by weight based on the resin component (preferably a propylene-based resin) in the base layer (A1).

[0119] 1-1-1-2. Preferred embodiment 2 of the substrate layer (A1) In the second preferred embodiment of the substrate layer (A1), the substrate layer (A1) more preferably contains a pentene resin. The substrate layer (A1) contains a pentene resin, which can further enhance the effects of the present invention. In particular, the substrate layer (A1) contains a pentene resin, which can further enhance the effects of the present invention, since the outermost surface of the substrate layer (A) has better heat resistance. In particular, the substrate layer (A1) contains a pentene resin, which can sufficiently suppress the breakage of the surface protective film during the heat press in the step of heat pressing the resin substrate to which the surface protective film according to the embodiment of the present invention is attached in a mold, even if the thickness of the substrate layer (A1) is thin, and can also sufficiently suppress the orange peel on the surface of the resin substrate after the heat press. Furthermore, since the thickness of the substrate layer (A1) can be thinned, the surface protective film according to the embodiment of the present invention can be given an appropriate softness that allows the heat press step to be smoothly performed.

[0120] The content of the pentene resin in the base layer (A1) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, even more preferably 95% by weight to 100% by weight, particularly preferably 98% by weight to 100% by weight, and most preferably substantially 100% by weight. When the content of the pentene resin in the base layer (A1) is within the above range, the effects of the present invention can be more effectively exhibited. In particular, when the content of the pentene resin in the base layer (A1) is within the above range, the outermost surface of the base layer (A) can have better heat resistance, so that the effects of the present invention can be more effectively exhibited. If the content of the pentene resin in the base layer (A1) is outside the above range, the heat resistance of the outermost surface of the base layer (A) may be poor. When the surface protection film in the embodiment of the present invention is used for hot pressing of a resin substrate, the surface protection film may be more likely to adhere to a mold due to melting, etc., and the surface protection film may be more likely to shift in position or wrinkle when pressed at high temperatures.

[0121] As the pentene resin that may be contained in the base layer (A1), any suitable pentene resin may be adopted within a range that does not impair the effects of the present invention. Examples of such pentene resins include at least one selected from poly(4-methylpentene-1), copolymers of 4-methylpentene-1 and other monomers, poly(3-methylpentene-1), and copolymers of 3-methylpentene-1 and other monomers. In terms of being able to further exhibit the effects of the present invention, the pentene resin may be at least one selected from poly(4-methylpentene-1) and copolymers of 4-methylpentene-1 and other monomers, and a representative example is the product name "TPX (registered trademark)" manufactured by Mitsui Chemicals, Inc., which is a crystalline pentene resin made mainly from 4-methylpentene-1.

[0122] The pentene resin may be a Ziegler-Natta pentene resin obtained by using a Ziegler-Natta catalyst.

[0123] The pentene resin may be a metallocene-based pentene resin obtained by using a metallocene catalyst.

[0124] The substrate layer (A1) may contain any other appropriate resin component as long as the effects of the present invention are not impaired.

[0125] In embodiment 2, the base layer (A1) preferably does not contain a release agent. In embodiment 2, even if the base layer (A1) does not contain a release agent, the surface protection film can smoothly follow the mold during curved processing by pressing at high temperature, and the surface protection film is less likely to break.

[0126] In embodiment 2, the content of the release agent in the base layer (A1) is preferably 0 wt % to 10 wt %, more preferably 0 wt % to 1 wt %, even more preferably 0 wt % to 0.1 wt %, particularly preferably 0 wt % to 0.01 wt %, and most preferably substantially 0 wt %.

[0127] In this specification, the term "substantially 0% by weight" means that a very small amount may be contained within a range that does not impair the effects of the present invention, and may usually be referred to as "0% by weight".

[0128] In embodiment 2, the base layer (A1) may contain only one type of release agent, or two or more types.

[0129] In embodiment 2, the types of release agents that can be contained in the base layer (A1) and the means for incorporating the release agents can be referenced in the explanation in [1-1-1-1. A preferred embodiment 1 of base layer (A1)].

[0130] The base layer (A1) may contain any suitable additives, if necessary, in addition to the release agent. Examples of additives that may be contained in the base layer (A1) include ultraviolet absorbers, heat resistance stabilizers, fillers, lubricants, colorants (dyes, etc.), antioxidants, eye plug inhibitors, antiblocking agents, foaming agents, and polyethyleneimines. These may be used alone or in combination of two or more. The content of the additives in the base layer (A1) is preferably 10% by weight or less, more preferably 7% by weight or less, even more preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

[0131] Examples of the ultraviolet absorbing agent include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. The content of the ultraviolet absorbing agent may be any appropriate content as long as it does not bleed out during molding. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably propylene-based resin) in the base layer (A1).

[0132] Examples of the heat resistance stabilizer include hindered amine compounds, phosphorus compounds, and cyanoacrylate compounds. The content of the heat resistance stabilizer may be any appropriate content as long as it does not bleed out during molding. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably propylene resin) in the base layer (A1).

[0133] Examples of the filler include inorganic fillers such as talc, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, silica, clay, mica, barium sulfate, whiskers, and magnesium hydroxide. The average particle size of the filler is preferably 0.1 μm to 20 μm. The content of the filler may be any appropriate content. Typically, the content is preferably 1% by weight to 200% by weight based on the resin component (preferably a propylene-based resin) in the base layer (A1).

[0134] <1-1-2. Base material layer (A2)> The substrate layer (A) preferably includes a substrate layer (A1) and a substrate layer (A2) in this order, that is, the substrate layer (A2) is disposed between the substrate layer (A1) and the pressure-sensitive adhesive layer (B).

[0135] The thickness of the substrate layer (A2) is preferably 10 μm to 125 μm. When the thickness of the substrate layer (A2) is within the above range, the effects of the present invention can be more effectively achieved. If the thickness of the substrate layer (A2) is too thin, the surface protection film is too hard, and it may be difficult to follow the three-dimensional curved shape of the mold. If the thickness of the substrate layer (A2) is too thick, the surface protection film is too soft, and there is a risk of the surface protection film being displaced or wrinkled.

[0136] When a thin thickness is required, the thickness of the base layer (A2) is preferably 10 μm to 100 μm, more preferably 10 μm to 80 μm, even more preferably 10 μm to 60 μm, still more preferably 10 μm to 50 μm, particularly preferably 15 μm to 40 μm, and most preferably 20 μm to 30 μm.

[0137] When an appropriate thickness is required, the thickness of the base layer (A2) is preferably 25 μm to 125 μm, more preferably 30 μm to 120 μm, still more preferably 40 μm to 105 μm, and particularly preferably 50 μm to 90 μm.

[0138] The substrate layer (A2) may consist of only one layer, or may consist of two or more layers. When the substrate layer (A2) consists of two or more layers, each layer may have the same composition, or at least one layer may be a different layer.

[0139] The base layer (A2) preferably has 1 to 5 layers, more preferably 1 to 3 layers, further preferably 1 or 2 layers, and particularly preferably 1 layer.

[0140] The substrate layer (A2) may contain any appropriate resin as long as the effects of the present invention are not impaired.

[0141] The base layer (A2) preferably contains at least one selected from an ethylene-based resin and a propylene-based resin. The effects of the present invention can be more effectively achieved by the base layer (A2) containing at least one selected from an ethylene-based resin and a propylene-based resin. If the base layer (A2) does not contain at least one selected from an ethylene-based resin and a propylene-based resin, the surface protection film according to the embodiment of the present invention may not have an appropriate softness, and the surface protection film may be displaced or wrinkled, and may be difficult to follow the three-dimensional curved shape of the mold.

[0142] 1-1-2-1. Preferred embodiment 1 of the substrate layer (A2) In a preferred embodiment 1 of the substrate layer (A2), the substrate layer (A2) preferably contains an ethylene-based resin. When the substrate layer (A2) contains an ethylene-based resin, the effects of the present invention can be more effectively achieved. In particular, when the substrate layer (A2) contains an ethylene-based resin, the surface protection film in the embodiment of the present invention has appropriate softness, and when used in the heat pressing of a resin substrate, good three-dimensional curved surface processing can be achieved.

[0143] The content of the ethylene-based resin that can be contained in the base layer (A2) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, particularly preferably 95% by weight to 100% by weight, and most preferably substantially 100% by weight. When the content of the ethylene-based resin in the base layer (A2) is within the above range, the effects of the present invention can be more effectively exhibited. In particular, when the content of the ethylene-based resin in the base layer (A2) is within the above range, the surface protection film in the embodiment of the present invention has appropriate softness, and when used in the heat pressing of a resin substrate, good three-dimensional curved processing can be achieved. When the content of the ethylene-based resin in the base layer (A2) is out of the above range, the surface protection film in the embodiment of the present invention may not have appropriate softness, and the surface protection film may be displaced or wrinkled, and it may be difficult to follow the three-dimensional curved shape of a mold.

[0144] As the ethylene-based resin that can be contained in the base layer (A2), any suitable ethylene-based resin can be adopted within the scope that does not impair the effects of the present invention. Examples of such ethylene-based resins include at least one selected from low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene, medium-density polyethylene (MDPE), high-density polyethylene (HDPE), very high-density polyethylene, and copolymers of ethylene and other monomers (e.g., ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid ester copolymer, ethylene / butene-1 copolymer, ethylene / propylene / butene-1 copolymer, ethylene / α-olefin copolymer having 5 to 12 carbon atoms, ethylene / non-conjugated diene copolymer, etc.), and preferably at least one selected from low-density polyethylene and ethylene-vinyl acetate copolymer.

[0145] The ethylene-based resin that may be contained in the substrate layer (A2) may be a Ziegler-Natta ethylene-based resin obtained by using a Ziegler-Natta catalyst.

[0146] The ethylene-based resin that can be contained in the substrate layer (A2) may be a metallocene-based ethylene-based resin obtained by using a metallocene catalyst. Examples of such metallocene-based ethylene-based resins include at least one selected from metallocene-based low-density polyethylene and metallocene-based ethylene / vinyl acetate copolymers.

[0147] As the ethylene-based resin, a commercially available product may be used.

[0148] The substrate layer (A2) may contain any other appropriate resin component as long as the effects of the present invention are not impaired.

[0149] The substrate layer (A2) may contain any suitable additive as necessary. Examples of additives that may be contained in the substrate layer (A2) include a release agent, an ultraviolet absorber, a heat resistance stabilizer, a filler, a lubricant, a colorant (dye, etc.), an antioxidant, an anti-dye agent, an anti-blocking agent, a foaming agent, and polyethyleneimine. These may be used alone or in combination of two or more. The content of the additive in the substrate layer (A2) is preferably 10% by weight or less, more preferably 7% by weight or less, even more preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

[0150] Examples of the release agent include fatty acid amide-based release agents, silicone-based release agents, fluorine-based release agents, and long-chain alkyl-based release agents. From the viewpoint of forming a release layer with an excellent balance between releasability and contamination caused by bleed-out, fatty acid amide-based release agents are preferred, and saturated fatty acid bisamides are more preferred. The content of the release agent may be any appropriate content. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably an ethylene-based resin) in the base layer (A2).

[0151] Examples of the ultraviolet absorbing agent include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. The content of the ultraviolet absorbing agent may be any appropriate content as long as it does not bleed out during molding. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably an ethylene-based resin) in the base layer (A2).

[0152] Examples of the heat resistance stabilizer include hindered amine compounds, phosphorus compounds, and cyanoacrylate compounds. The content of the heat resistance stabilizer may be any appropriate content as long as it does not bleed out during molding. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably an ethylene resin) in the base layer (A2).

[0153] Examples of the filler include inorganic fillers such as talc, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, silica, clay, mica, barium sulfate, whiskers, and magnesium hydroxide. The average particle size of the filler is preferably 0.1 μm to 20 μm. The content of the filler may be any appropriate content. Typically, the content is preferably 1% by weight to 200% by weight based on the resin component (preferably an ethylene-based resin) in the base layer (A2).

[0154] 1-1-2-2. Preferred embodiment 2 of the substrate layer (A2) In a preferred embodiment 2 of the substrate layer (A2), the substrate layer (A2) preferably contains a propylene-based resin. When the substrate layer (A2) contains a propylene-based resin, the effects of the present invention can be more effectively achieved. In particular, when the substrate layer (A2) contains a propylene-based resin, the surface protection film in the embodiment of the present invention has appropriate softness and heat resistance, and when used in hot pressing of a resin substrate, good three-dimensional curved surface processing can be achieved.

[0155] The content of the propylene-based resin that can be contained in the base layer (A2) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, particularly preferably 95% by weight to 100% by weight, and most preferably substantially 100% by weight. When the content of the propylene-based resin in the base layer (A2) is within the above range, the effect of the present invention can be more effectively exhibited. In particular, when the content of the propylene-based resin in the base layer (A2) is within the above range, the surface protection film in the embodiment of the present invention has appropriate softness and heat resistance, and when used in hot pressing of a resin substrate, good three-dimensional curved processing can be achieved. When the content of the propylene-based resin in the base layer (A2) is out of the above range, the surface protection film in the embodiment of the present invention may not have appropriate softness, and the surface protection film may be displaced or wrinkled, and it may be difficult to follow the three-dimensional curved shape of a mold.

[0156] The propylene-based resin that can be contained in the base layer (A2) can be any suitable propylene-based resin within the scope that does not impair the effects of the present invention. For example, the propylene-based resin can be at least one selected from random polypropylene, block polypropylene, homopolypropylene, and copolymers of propylene and other monomers, and homopolypropylene is preferred in terms of being able to more effectively exhibit the effects of the present invention.

[0157] The propylene-based resin that may be contained in the substrate layer (A2) may be a Ziegler-Natta propylene-based resin obtained by using a Ziegler-Natta catalyst.

[0158] The propylene-based resin that can be contained in the base layer (A2) may be a metallocene-based propylene-based resin obtained by using a metallocene catalyst. Examples of such metallocene-based propylene-based resins include at least one selected from metallocene-based random polypropylenes, metallocene-based block polypropylenes, metallocene-based homopolypropylenes, and copolymers of metallocene-based propylene and other monomers.

[0159] As the propylene-based resin, a commercially available product may be used.

[0160] The substrate layer (A2) may contain any other appropriate resin component as long as the effects of the present invention are not impaired.

[0161] The substrate layer (A2) may contain any suitable additive as necessary. Examples of additives that may be contained in the substrate layer (A2) include a release agent, an ultraviolet absorber, a heat resistance stabilizer, a filler, a lubricant, a colorant (dye, etc.), an antioxidant, an anti-dye agent, an anti-blocking agent, a foaming agent, and polyethyleneimine. These may be used alone or in combination of two or more. The content of the additive in the substrate layer (A2) is preferably 10% by weight or less, more preferably 7% by weight or less, even more preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

[0162] Examples of the release agent include fatty acid amide-based release agents, silicone-based release agents, fluorine-based release agents, and long-chain alkyl-based release agents. From the viewpoint of forming a release layer with an excellent balance between releasability and contamination caused by bleed-out, fatty acid amide-based release agents are preferred, and saturated fatty acid bisamides are more preferred. The content of the release agent may be any appropriate content. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably an ethylene-based resin) in the base layer (A2).

[0163] Examples of the ultraviolet absorbing agent include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. The content of the ultraviolet absorbing agent may be any appropriate content as long as it does not bleed out during molding. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably an ethylene-based resin) in the base layer (A2).

[0164] Examples of the heat resistance stabilizer include hindered amine compounds, phosphorus compounds, and cyanoacrylate compounds. The content of the heat resistance stabilizer may be any appropriate content as long as it does not bleed out during molding. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably an ethylene resin) in the base layer (A2).

[0165] Examples of the filler include inorganic fillers such as talc, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, silica, clay, mica, barium sulfate, whiskers, and magnesium hydroxide. The average particle size of the filler is preferably 0.1 μm to 20 μm. The content of the filler may be any appropriate content. Typically, the content is preferably 1% by weight to 200% by weight based on the resin component (preferably an ethylene-based resin) in the base layer (A2).

[0166] <1-1-3. Auxiliary base material layer (A3)> The substrate layer (A) preferably includes a substrate layer (A1), a substrate layer (A2) and an auxiliary substrate layer (A3) in this order, that is, the auxiliary substrate layer (A3) is disposed between the substrate layer (A2) and the pressure-sensitive adhesive layer (B).

[0167] The thickness of the auxiliary base layer (A3) is preferably 2 μm to 60 μm, more preferably 3 μm to 60 μm, even more preferably 5 μm to 55 μm, even more preferably 5 μm to 50 μm, even more preferably 5 μm to 40 μm, particularly preferably 5 μm to 30 μm, and most preferably 5 μm to 20 μm. When the thickness of the auxiliary base layer (A3) is within the above range, the effects of the present invention can be more effectively exhibited.

[0168] The thickness error between the auxiliary base layer (A3) and the base layer (A1) is preferably ±150% or less, more preferably ±100% or less, even more preferably ±50% or less, even more preferably ±30% or less, even more preferably ±10% or less, particularly preferably ±5% or less, and most preferably substantially 0%. If the error between the thickness of the auxiliary base layer (A3) and the thickness of the base layer (A1) is within the above range, the laminated structure of the base layer in the surface protection film in the embodiment of the present invention is close to vertical symmetry, so that curling of the surface protection film can be suppressed. In particular, when the surface protection film in the embodiment of the present invention is used for heat pressing of a resin substrate, curling due to heat history can be effectively suppressed.

[0169] The auxiliary substrate layer (A3) may consist of only one layer, or may consist of two or more layers. When the auxiliary substrate layer (A3) consists of two or more layers, each layer may have the same composition, or at least one layer may be a different layer.

[0170] The auxiliary substrate layer (A3) preferably has 1 to 5 layers, more preferably 1 to 3 layers, further preferably 1 to 2 layers, and particularly preferably 1 layer.

[0171] The auxiliary substrate layer (A3) may contain any appropriate resin within a range that does not impair the effects of the present invention. The main component resin contained in the auxiliary substrate layer (A3) is preferably the same as the main component resin contained in the substrate layer (A1). If the main component resin contained in the auxiliary substrate layer (A3) is the same as the main component resin contained in the substrate layer (A1), the composition distribution of the substrate layer in the surface protective film according to the embodiment of the present invention becomes close to vertical symmetry, so that curling of the surface protective film can be suppressed. In particular, when the surface protective film according to the embodiment of the present invention is used for heat pressing of a resin substrate, curling due to heat history can be effectively suppressed. Here, the "main component" means that the content ratio in the whole is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, particularly preferably 95% by weight to 100% by weight, and most preferably substantially 100% by weight.

[0172] The auxiliary substrate layer (A3) may contain any suitable resin within the scope of the present invention. The auxiliary substrate layer (A3) contains at least one selected from ethylene resin, propylene resin, butene resin, and pentene resin. The auxiliary substrate layer (A3) contains at least one selected from ethylene resin, propylene resin, butene resin, and pentene resin, so that the effects of the present invention can be more effectively exhibited. In particular, the auxiliary substrate layer (A3) contains at least one selected from ethylene resin, propylene resin, butene resin, and pentene resin, so that the outermost surface of the auxiliary substrate layer (A3) can have excellent heat resistance, so that the effects of the present invention can be more effectively exhibited. If the auxiliary base layer (A3) does not contain at least one selected from ethylene-based resins, propylene-based resins, butene-based resins, and pentene-based resins, the heat resistance of the outermost surface of the base layer (A) may be poor. When the surface protection film in an embodiment of the present invention is used for hot pressing of a resin substrate, the surface protection film may be more likely to adhere to the mold due to melting, etc., and the surface protection film may be more likely to shift in position or wrinkle when pressed at high temperatures.

[0173] The content ratio of at least one selected from ethylene resin, propylene resin, butene resin, and pentene resin in the auxiliary substrate layer (A3) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 90% by weight to 100% by weight, particularly preferably 95% by weight to 100% by weight, and most preferably substantially 100% by weight. If the content ratio of at least one selected from ethylene resin, propylene resin, butene resin, and pentene resin in the auxiliary substrate layer (A3) is within the above range, the effect of the present invention can be more effectively exhibited. In particular, if the content ratio of at least one selected from ethylene resin, propylene resin, butene resin, and pentene resin in the auxiliary substrate layer (A3) is within the above range, the outermost surface of the substrate layer (A) can have excellent heat resistance, so that the effect of the present invention can be more effectively exhibited. If the content ratio of at least one selected from ethylene-based resins, propylene-based resins, butene-based resins, and pentene-based resins in the auxiliary base layer (A3) is outside the above range, the heat resistance of the outermost surface of the base layer (A) may be poor, and when the surface protection film in an embodiment of the present invention is used for hot pressing of a resin substrate, the surface protection film may be more likely to adhere to the mold due to melting, etc., and the surface protection film may be more likely to shift in position or wrinkle when pressed at high temperatures.

[0174] As the ethylene-based resin that can be contained in the auxiliary base layer (A3), any suitable ethylene-based resin can be adopted within the scope that does not impair the effects of the present invention. Such ethylene-based resins include, for example, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), very low-density polyethylene, medium-density polyethylene (MDPE), high-density polyethylene (HDPE), very high-density polyethylene, and copolymers of ethylene and other monomers (for example, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / methacrylic acid copolymer, ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid ester copolymer, ethylene / butene-1 copolymer, ethylene / propylene / butene-1 copolymer, ethylene / α-olefin copolymer having 5 to 12 carbon atoms, ethylene / non-conjugated diene copolymer, etc.), preferably, at least one selected from high-density polyethylene, low-density polyethylene, and ethylene / vinyl acetate copolymer, more preferably, high-density polyethylene.

[0175] The ethylene-based resin that may be contained in the auxiliary substrate layer (A3) may be a Ziegler-Natta ethylene-based resin obtained by using a Ziegler-Natta catalyst.

[0176] The ethylene-based resin that can be contained in the auxiliary substrate layer (A3) may be a metallocene-based ethylene-based resin obtained by using a metallocene catalyst. Examples of such metallocene-based ethylene-based resins include at least one selected from metallocene-based low-density polyethylene and metallocene-based ethylene / vinyl acetate copolymers.

[0177] The ethylene-based resin that can be contained in the auxiliary substrate layer (A3) may be a single type, or a blend of two or more types.

[0178] As the ethylene-based resin that can be contained in the auxiliary substrate layer (A3), a commercially available product may be used.

[0179] The propylene-based resin that can be contained in the auxiliary substrate layer (A3) can be any suitable propylene-based resin within the scope that does not impair the effects of the present invention. Examples of such propylene-based resins include at least one selected from random polypropylene, block polypropylene, homopolypropylene, and copolymers of propylene and other monomers.

[0180] The propylene-based resin that can be contained in the auxiliary substrate layer (A3) may be a single type or a blend of two or more types.

[0181] Representative examples of homopolypropylene include isotactic homopolypropylene, atactic homopolypropylene, and syndiotactic homopolypropylene.

[0182] As the copolymer of propylene and other monomers, any appropriate copolymer can be adopted within the scope that does not impair the effects of the present invention. Examples of such copolymers of propylene and other monomers include propylene / ethylene copolymer, propylene / ethylene / 1-butene copolymer, and propylene / α-olefin copolymer having 5 to 12 carbon atoms.

[0183] The propylene-based resin that may be contained in the auxiliary substrate layer (A3) may be a Ziegler-Natta propylene-based resin obtained by using a Ziegler-Natta catalyst.

[0184] The propylene-based resin that can be contained in the auxiliary substrate layer (A3) may be a metallocene-based propylene-based resin obtained by using a metallocene catalyst. Such a metallocene-based propylene-based resin may be, for example, at least one selected from metallocene-based random polypropylene, metallocene-based block polypropylene, metallocene-based homopolypropylene, and a copolymer of metallocene-based propylene and other monomers.

[0185] As the propylene-based resin that can be contained in the auxiliary substrate layer (A3), a commercially available product may be used.

[0186] As the pentene resin that can be contained in the auxiliary substrate layer (A3), any suitable pentene resin can be adopted within the scope that does not impair the effects of the present invention. Examples of such pentene resins include at least one selected from poly(4-methylpentene-1), copolymers of 4-methylpentene-1 and other monomers, poly(3-methylpentene-1), and copolymers of 3-methylpentene-1 and other monomers. In terms of being able to further express the effects of the present invention, the pentene resin includes at least one selected from poly(4-methylpentene-1) and copolymers of 4-methylpentene-1 and other monomers, and a representative example is the product name "TPX (registered trademark)" manufactured by Mitsui Chemicals, Inc., which is a crystalline pentene resin made mainly from 4-methylpentene-1.

[0187] The pentene resin that may be contained in the auxiliary substrate layer (A3) may be a Ziegler-Natta pentene resin obtained by using a Ziegler-Natta catalyst.

[0188] The pentene resin that can be contained in the auxiliary substrate layer (A3) may be a metallocene-based pentene resin obtained by using a metallocene catalyst.

[0189] The auxiliary substrate layer (A3) may contain any other appropriate resin component within a range that does not impair the effects of the present invention.

[0190] The auxiliary substrate layer (A3) may contain any suitable additive as necessary. Examples of additives that may be contained in the auxiliary substrate layer (A3) include release agents, ultraviolet absorbers, heat resistance stabilizers, fillers, lubricants, colorants (dyes, etc.), antioxidants, eye plug inhibitors, antiblocking agents, foaming agents, and polyethyleneimines. These may be used alone or in combination of two or more. The content of the additives in the auxiliary substrate layer (A3) is preferably 10% by weight or less, more preferably 7% by weight or less, even more preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

[0191] Examples of the release agent include fatty acid amide-based release agents, silicone-based release agents, fluorine-based release agents, and long-chain alkyl-based release agents. From the viewpoint of forming a release layer with an excellent balance between releasability and contamination caused by bleed-out, fatty acid amide-based release agents are preferred, and saturated fatty acid bisamides are more preferred. The content of the release agent may be any appropriate content. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably propylene-based resin) in the auxiliary base layer (A3).

[0192] Examples of the ultraviolet absorbing agent include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. The content of the ultraviolet absorbing agent may be any appropriate content as long as it does not bleed out during molding. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably propylene-based resin) in the auxiliary substrate layer (A3).

[0193] Examples of the heat resistance stabilizer include hindered amine compounds, phosphorus compounds, and cyanoacrylate compounds. The content of the heat resistance stabilizer may be any appropriate content as long as it does not bleed out during molding. Typically, the content is preferably 0.01% by weight to 5% by weight based on the resin component (preferably propylene resin) in the auxiliary base layer (A3).

[0194] Examples of the filler include inorganic fillers such as talc, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, silica, clay, mica, barium sulfate, whiskers, and magnesium hydroxide. The average particle size of the filler is preferably 0.1 μm to 20 μm. The content of the filler may be any appropriate content. Typically, the content is preferably 1 wt % to 200 wt % relative to the resin component (preferably propylene-based resin) in the auxiliary base layer (A3).

[0195] ≪1-2. Adhesive layer (B)≫ The thickness of the pressure-sensitive adhesive layer (B) is preferably 5 μm to 50 μm, more preferably 5 μm to 40 μm, even more preferably 5 μm to 30 μm, and particularly preferably 5 μm to 20 μm. When the thickness of the pressure-sensitive adhesive layer (B) is within the above range, the effects of the present invention can be more effectively exhibited. If the thickness of the pressure-sensitive adhesive layer (B) is too thin, the adhesive effect may not be sufficiently exhibited. If the thickness of the pressure-sensitive adhesive layer (B) is too thick, the surface protection film becomes too thick, and it may become difficult to follow the three-dimensional curved shape of the mold.

[0196] The pressure-sensitive adhesive layer (B) may consist of only one layer, or may consist of two or more layers. When the pressure-sensitive adhesive layer (B) consists of two or more layers, each layer may be a layer having the same composition, or at least one layer may be a layer having a different composition.

[0197] The pressure-sensitive adhesive layer (B) may be an adhesive layer formed from any appropriate pressure-sensitive adhesive. Examples of such pressure-sensitive adhesives include thermoplastic resin-based pressure-sensitive adhesives containing a base polymer containing a thermoplastic resin as a main component (preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 80% by weight to 100% by weight, particularly preferably 90% by weight to 100% by weight, and most preferably 95% by weight to 100% by weight). The thermoplastic resin that can be contained in the base polymer may be only one type or two or more types.

[0198] Any suitable thermoplastic resin may be used as the thermoplastic resin. For example, at least one selected from the group consisting of styrene-based resins, olefin-based resins, aromatic group-containing olefin / diene copolymers, ester-based resins, acrylic resins, and rubber-based resins may be used as the thermoplastic resin. Among these thermoplastic resins, at least one selected from the group consisting of styrene-based resins and olefin-based resins is preferred.

[0199] As the styrene-based resin, preferably, a styrene-based elastomer is used.

[0200] As the olefin-based resin, preferably, an olefin-based elastomer is used.

[0201] By using at least one type selected from the group consisting of styrene-based resins and olefin-based resins as the thermoplastic resin, it is possible to achieve a good balance of good adhesive strength, good adhesive strength after storage over time, and low contamination after peeling.

[0202] The styrene-based elastomer preferably includes hydrogenated styrene-butadiene rubber (HSBR), a styrene-based block copolymer, or a hydrogenated product thereof.

[0203] Examples of hydrogenated styrene-butadiene rubber (HSBR) include Dynaron 1320P, 1321P, and 2324P manufactured by JSR.

[0204] Examples of styrenic block copolymers include styrenic ABA type block copolymers (triblock copolymers) such as styrene-butadiene-styrene copolymer (SBS) and styrene-isoprene-styrene copolymer (SIS); styrenic ABAB type block copolymers (tetrablock copolymers) such as styrene-butadiene-styrene-butadiene copolymer (SBSB) and styrene-isoprene-styrene-isoprene copolymer (SISI); styrenic ABABA type block copolymers (pentablock copolymers) such as styrene-butadiene-styrene-butadiene-styrene copolymer (SBSBS) and styrene-isoprene-styrene-isoprene-styrene copolymer (SISIS); and styrenic block copolymers having more AB repeating units than this.

[0205] Examples of hydrogenated styrene block copolymers include styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-ethylene-propylene-styrene copolymer (SEPS), and styrene-ethylene-butylene-styrene-ethylene-butylene copolymer (SEBSEB).

[0206] As the styrene-based thermoplastic elastomer, styrene-ethylene-butylene copolymer-styrene copolymer (SEBS) is particularly preferred. By adopting styrene-ethylene-butylene copolymer-styrene copolymer (SEBS) as the styrene-based elastomer, it is possible to achieve a good balance of good adhesion, good adhesion after storage over time, and low contamination after peeling.

[0207] Examples of styrene-ethylene-butylene copolymer-styrene copolymer (SEBS) include Dynaron 8601P and 9901P manufactured by JSR.

[0208] The styrene-based elastomer may be used alone or in combination of two or more kinds. good.

[0209] The styrene content in the styrene elastomer (styrene block content in the case of a styrene block copolymer) is preferably 1% by weight to 40% by weight, more preferably 5% by weight to 40% by weight, even more preferably 7% by weight to 30% by weight, even more preferably 9% by weight to 20% by weight, particularly preferably 9% by weight to 15% by weight, and most preferably 9% by weight to 13% by weight. If the styrene content is low, there is a risk that adhesive residue is likely to occur due to insufficient cohesive force of the adhesive layer. If the styrene content is high, there is a risk that the adhesive layer becomes hard and good adhesion to a rough surface cannot be obtained. By keeping the styrene block content within the above range, good adhesion, good adhesion after storage over time, low contamination after peeling, and the like can be expressed in a well-balanced manner.

[0210] As the styrene-based elastomer, a hydrogenated styrene-based block copolymer having a repeating structure of a triblock copolymer or more (ABA type, ABAB type, ABABA type, etc.) consisting of styrene (A) and butadiene (B) (SEBS, SEBSEB, SEBSEBS, etc.) is suitable. By using such a styrene-based elastomer, it is possible to achieve a good balance of good adhesion, good adhesion after storage over time, low contamination after peeling, etc.

[0211] When the styrene elastomer is a hydrogenated styrene block copolymer having a repeating structure of a triblock copolymer or more (ABA type, ABAB type, ABABA type, etc.) consisting of styrene (A) and butadiene (B) (SEBS, SEBSEB, SEBSEBS, etc.), the proportion of butylene structures in the ethylene-butylene copolymer block is preferably 60% by weight or more, more preferably 70% by weight or more, and even more preferably 75% by weight or more. By having the proportion of butylene structures in the ethylene-butylene copolymer block within the above range, good adhesive strength, good adhesive strength after storage over time, low contamination after peeling, etc. can be expressed in a well-balanced manner. The proportion of butylene structures in the ethylene-butylene copolymer block is preferably 90% by weight or less.

[0212] The base polymer may contain other styrene-based elastomers for the purpose of adjusting adhesion, etc., within the scope of the present invention.

[0213] Other styrene-based elastomers include styrene-based block copolymers other than those mentioned above; AB-type block polymers such as styrene-butadiene copolymer (SB), styrene-isoprene copolymer (SI), styrene-ethylene-butylene copolymer (SEB), and styrene-ethylene-propylene copolymer (SEP); styrene-based random copolymers such as styrene-butadiene rubber (SBR); ABC-type styrene-olefin crystalline block polymers such as styrene-ethylene-butylene copolymer-olefin crystalline copolymer (SEBC); and hydrogenated products of these.

[0214] As the olefin-based elastomer, preferably, an amorphous polyolefin-based elastomer is used.

[0215] Examples of the amorphous polyolefin-based elastomer include ethylene propylene rubber, elastomers made of ethylene and α-olefin, and amorphous polypropylene-based resins that exhibit adhesion (such as atactic polypropylene). Preferably, amorphous polypropylene-based resins are used. Any suitable amorphous polypropylene-based resin may be used as the amorphous polypropylene-based resin as long as it has rubber elasticity in the temperature range in which it is used.

[0216] Here, the amorphous polyolefin elastomer is amorphous and does not have a crystal structure. For example, a solubility test in n-heptane can be used as a method for confirming that the elastomer is amorphous. Specifically, the amorphous polyolefin elastomer is dissolved in n-heptane at a concentration of 10% by weight, and its solubility is measured. In this case, the solubility of the elastomer is 90% or more, assuming that the elastomer is substantially completely dissolved as 100%, and the elastomer is considered to be amorphous.

[0217] Examples of the amorphous polypropylene resin include propylene-α-olefin copolymers and propylene-ethylene-α-olefin copolymers.

[0218] Examples of α-olefins include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, and 4-methyl-1-hexene. Among these, 1-butene, 1-hexene, 1-octene, and 4-methyl-1-pentene are preferred. The α-olefin may be one type or two or more types.

[0219] As the amorphous polypropylene-based resin, preferably, an amorphous propylene-(1-butene) copolymer can be mentioned. The amorphous propylene-(1-butene) copolymer can be obtained by copolymerizing propylene and 1-butene preferably using a metallocene catalyst. The amorphous propylene-(1-butene) copolymer obtained by copolymerization using a metallocene catalyst shows a narrow molecular weight distribution (for example, 2 or less). By using an amorphous propylene-(1-butene) copolymer showing such a narrow molecular weight distribution, it is possible to prevent bleeding of low molecular weight components.

[0220] The content of propylene-derived structural units in the amorphous propylene-(1-butene) copolymer is preferably 80 mol% to 99 mol%, more preferably 85 mol% to 99 mol%, and even more preferably 90 mol% to 99 mol%. When the content of propylene-derived structural units in the amorphous propylene-(1-butene) copolymer is within such a range, a pressure-sensitive adhesive layer having an excellent balance between toughness and flexibility can be obtained, and the effects of the present invention can be more effectively exhibited.

[0221] The content of the 1-butene-derived structural units in the amorphous propylene-(1-butene) copolymer is preferably 1 mol% to 15 mol%, more preferably 1 mol% to 10 mol%. When the content of the 1-butene-derived structural units in the amorphous propylene-(1-butene) copolymer is within this range, a pressure-sensitive adhesive layer having an excellent balance between toughness and flexibility can be obtained, and the effects of the present invention can be more effectively exhibited.

[0222] The copolymer structure of the amorphous propylene-(1-butene) copolymer may be any appropriate copolymer structure, such as a block copolymer or a random copolymer.

[0223] The weight average molecular weight (Mw) of the amorphous propylene-(1-butene) copolymer is preferably 200,000 or more, more preferably 200,000 to 500,000, and even more preferably 200,000 to 300,000. When the weight average molecular weight (Mw) of the amorphous propylene-(1-butene) copolymer is within such a range, a pressure-sensitive adhesive layer having appropriate adhesive strength can be obtained, and the effects of the present invention can be more effectively exhibited.

[0224] When the pressure-sensitive adhesive layer (B) contains an amorphous propylene-(1-butene) copolymer, the pressure-sensitive adhesive layer may further contain a crystalline polypropylene resin in order to adjust the adhesive strength of the pressure-sensitive adhesive layer. When the pressure-sensitive adhesive layer contains a crystalline polypropylene resin, the adhesive strength of the pressure-sensitive adhesive layer can be appropriately reduced and the storage modulus can be increased. When the pressure-sensitive adhesive layer further contains a crystalline polypropylene resin, the content of the crystalline polypropylene resin in the pressure-sensitive adhesive layer can be set to any appropriate content depending on the desired adhesive strength and storage modulus. The content of such a crystalline polypropylene resin is preferably 0% by weight to 50% by weight, more preferably 0% by weight to 40% by weight, and even more preferably 0% by weight to 30% by weight, based on the total weight of the amorphous propylene-(1-butene) copolymer and the crystalline polypropylene resin.

[0225] The pressure-sensitive adhesive layer (B) may, for example, be an acrylic pressure-sensitive adhesive containing a base polymer containing an acrylic resin as a main component (preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even more preferably 80% by weight to 100% by weight, particularly preferably 90% by weight to 100% by weight, and most preferably 95% by weight to 100% by weight). The acrylic resin that can be contained in the base polymer may be of only one type, or may be of two or more types.

[0226] As the acrylic resin, any appropriate acrylic resin may be adopted as long as it does not impair the effects of the present invention. Such an acrylic resin is preferably obtained by polymerization of a monomer component (m).

[0227] As the monomer component (m), any appropriate monomer component can be adopted as long as it does not impair the effects of the present invention.

[0228] The monomer component (m) preferably contains an alkyl(meth)acrylate having an alkyl group having 4 to 18 carbon atoms at the ester terminal. The alkyl(meth)acrylate having an alkyl group having 4 to 18 carbon atoms at the ester terminal may be of one type or of two or more types.

[0229] Specific examples of alkyl (meth)acrylates having an alkyl group having 4 to 18 carbon atoms at the ester terminal include n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-undecyl (meth)acrylate, and n-dodecyl (meth)acrylate. alkyl (meth)acrylates having a linear alkyl group having 4 to 18 carbon atoms at the ester end, such as n-butyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-heptadecyl (meth)acrylate, and n-octadecyl (meth)acrylate; t-butyl (meth)acrylate, isobutyl (meth)acrylate, and the like; Examples of the alkyl (meth)acrylate include alkyl (meth)acrylates having a branched alkyl group having 4 to 18 carbon atoms at the ester terminal, such as t-pentyl (meth)acrylate, isopentyl (meth)acrylate, t-pentyl (meth)acrylate, neopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, 2-propylheptyl (meth)acrylate, isoundecyl (meth)acrylate, isododecyl (meth)acrylate, isotridecyl (meth)acrylate, isomistyryl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, and isostearyl (meth)acrylate. Among these alkyl(meth)acrylates having an alkyl group having 4 to 18 carbon atoms at the ester terminal, alkyl(meth)acrylates having a linear alkyl group having 4 to 12 carbon atoms at the ester terminal are preferred, alkyl(meth)acrylates having a linear alkyl group having 4 to 8 carbon atoms at the ester terminal are more preferred, and specifically, n-butyl(meth)acrylate is particularly preferred.

[0230] The content of alkyl (meth)acrylate having an alkyl group having 4 to 18 carbon atoms at the ester terminal in the monomer component (m) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 99.5% by weight, even more preferably 90% by weight to 99% by weight, particularly preferably 91% by weight to 98% by weight, and most preferably 92% by weight to 97% by weight.

[0231] The monomer component (m) preferably contains (meth)acrylic acid, more preferably contains acrylic acid. The content of (meth)acrylic acid in the total amount of the monomer component (m) is preferably 1 to 10% by weight, more preferably 1 to 8% by weight, even more preferably 2 to 7% by weight, particularly preferably 2 to 6% by weight, and most preferably 2.5 to 5.5% by weight.

[0232] The monomer component (m) may contain other monomers. Such other monomers may be of only one type, or of two or more types.

[0233] The content of other monomers in the total amount of monomer component (m) is preferably 0% by weight to 10% by weight, more preferably 0% by weight to 8% by weight, even more preferably 0% by weight to 6% by weight, particularly preferably 0% by weight to 4% by weight, and most preferably 0% by weight to 2% by weight.

[0234] Examples of the other monomers include alicyclic structure-containing acrylic monomers, alkyl (meth)acrylates having an alkyl group having 1 to 3 carbon atoms at the ester terminal, hydroxyl group-containing monomers, carboxyl group-containing monomers other than (meth)acrylic acid, nitrogen-based cyclic structure-containing monomers, cyclic ether group-containing monomers, glycol-based acrylic ester monomers, styrene-based monomers, amide group-containing monomers, amino group-containing monomers, imide group-containing monomers, vinyl ether monomers, silane-based monomers, and polyfunctional monomers.

[0235] The alicyclic structure-containing acrylic monomer is preferably an acrylic monomer having a cyclic aliphatic hydrocarbon structure. The number of carbon atoms in the cyclic aliphatic hydrocarbon structure is preferably 3 or more, more preferably 6 to 24, further preferably 6 to 18, and particularly preferably 6 to 12. Specific examples of such alicyclic structure-containing acrylic monomers include cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate.

[0236] Specific examples of alkyl(meth)acrylates having an alkyl group having 1 to 3 carbon atoms at the ester terminal include methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, and isopropyl(meth)acrylate.

[0237] Specific examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; hydroxyalkyl cycloalkane (meth)acrylates such as (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; and other hydroxyl group-containing monomers such as hydroxyethyl (meth)acrylamide, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. Among these hydroxyl group-containing monomers, hydroxyalkyl (meth)acrylates are preferred, hydroxyalkyl (meth)acrylates having a hydroxyalkyl group having 2 to 6 carbon atoms are more preferred, and 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are even more preferred.

[0238] Specific examples of carboxyl group-containing monomers other than (meth)acrylic acid include carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0239] Specific examples of the nitrogen-based cyclic structure-containing monomer include lactam-based vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; vinyl monomers having a nitrogen-containing heterocycle such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine; and (meth)acrylic monomers having a heterocycle such as a morpholine ring, a piperidine ring, a pyrrolidine ring, and a piperazine ring (for example, N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine).

[0240] Specific examples of the cyclic ether group-containing monomer include epoxy group-containing monomers such as glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, methyl glycidyl (meth)acrylate, and allyl glycidyl ether; and oxetane group-containing monomers such as 3-oxetanylmethyl (meth)acrylate, 3-methyl-oxetanylmethyl (meth)acrylate, 3-ethyl-oxetanylmethyl (meth)acrylate, 3-butyl-oxetanylmethyl (meth)acrylate, and 3-hexyl-oxetanylmethyl (meth)acrylate.

[0241] Specific examples of glycol-based acrylic ester monomers include polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate.

[0242] Specific examples of styrene-based monomers include styrene and α-methylstyrene.

[0243] Specific examples of amide group-containing monomers include acrylamide, methacrylamide, diethylacrylamide, N-vinylpyrrolidone, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, diacetoneacrylamide, and N,N-hydroxyethylacrylamide.

[0244] Specific examples of amino group-containing monomers include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

[0245] Specific examples of imide group-containing monomers include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

[0246] Specific examples of silane-based monomers include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane.

[0247] Specific examples of polyfunctional monomers include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, and 1,6-hexanediol. Examples of the polyhydric alcohol include ester compounds of polyhydric alcohols and (meth)acrylic acid, such as allyl di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate; vinyl (meth)acrylate; divinylbenzene; epoxy acrylate; polyester acrylate; urethane acrylate; butyl di(meth)acrylate; and hexyl di(meth)acrylate.

[0248] The acrylic resin is obtained by polymerization of the monomer component (m).

[0249] As a method for producing the acrylic resin, any suitable production method can be adopted as long as it does not impair the effects of the present invention. Examples of such production methods include active energy ray polymerization such as solution polymerization, UV polymerization, and various radical polymerizations such as bulk polymerization and emulsion polymerization. As a polymerization condition, any suitable polymerization condition can be adopted as long as it does not impair the effects of the present invention.

[0250] The polymerization structure of the resulting acrylic resin may be any appropriate polymerization structure as long as it does not impair the effects of the present invention. Examples of such polymerization structures include random copolymers, block copolymers, and graft copolymers.

[0251] As additives used in radical polymerization, such as a polymerization initiator, a chain transfer agent, and an emulsifier, any appropriate additives can be used as long as they do not impair the effects of the present invention.

[0252] Examples of the polymerization solvent that can be used in solution polymerization include ethyl acetate, toluene, etc. The polymerization solvent may be one type only, or two or more types may be used.

[0253] The solution polymerization is carried out, for example, under a stream of an inert gas such as nitrogen, by adding a polymerization initiator, usually at about 50° C. to 70° C., for about 5 hours to 30 hours.

[0254] As a polymerization initiator that can be used for solution polymerization, any appropriate thermal polymerization initiator can be adopted within a range that does not impair the effects of the present invention. The polymerization initiator may be one type only or two or more types. Examples of such polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid) dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl) propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (VA-057, Wako Pure Chemical Industries, Ltd.), and other azo initiators; persulfates such as potassium persulfate and ammonium persulfate, and di(2-ethylhexyl) Examples of the initiator include peroxide initiators such as peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, and hydrogen peroxide; and redox initiators which combine a peroxide and a reducing agent, such as a combination of a persulfate and sodium hydrogen sulfite, or a combination of a peroxide and sodium ascorbate.

[0255] The amount of the polymerization initiator used is preferably 1 part by weight or less, more preferably 0.005 to 1 part by weight, still more preferably 0.01 to 0.7 parts by weight, and particularly preferably 0.02 to 0.5 parts by weight, relative to 100 parts by weight of the total amount of the monomer components (m), in terms of being able to effectively proceed with the polymerization reaction, etc.

[0256] As the chain transfer agent, any suitable chain transfer agent may be used as long as it does not impair the effects of the present invention. The chain transfer agent may be one type or two or more types. Examples of such chain transfer agents include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol.

[0257] The amount of the chain transfer agent used is preferably 0.1 part by weight or less based on 100 parts by weight of the total amount of the monomer components (m), in order to effectively advance the polymerization reaction.

[0258] As the emulsifier, any suitable emulsifier may be adopted as long as it does not impair the effects of the present invention. The emulsifier may be one type or two or more types. Examples of such emulsifiers include anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, ammonium polyoxyethylene alkyl ether sulfate, and sodium polyoxyethylene alkyl phenyl ether sulfate; nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene-polyoxypropylene block polymer; and the like.

[0259] From the viewpoint of polymerization stability and mechanical stability, the amount of the emulsifier used is preferably 5 parts by weight or less, more preferably 0.3 to 5 parts by weight, even more preferably 0.4 to 3 parts by weight, and particularly preferably 0.5 to 1 part by weight, relative to 100 parts by weight of the total amount of the monomer components (m).

[0260] When UV polymerization is carried out, a photopolymerization initiator is preferably used.

[0261] As the photopolymerization initiator, any appropriate photopolymerization initiator may be adopted as long as it does not impair the effects of the present invention. The photopolymerization initiator may be only one type, or may be two or more types. Examples of such photopolymerization initiators include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators.

[0262] Specific examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one (a commercially available product is, for example, the trade name "Irgacure 651" manufactured by BASF), and anisole methyl ether.

[0263] Specific examples of acetophenone-based photopolymerization initiators include 1-hydroxycyclohexyl phenyl ketone (a commercially available product is, for example, the trade name "Irgacure 184" manufactured by BASF), 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (a commercially available product is, for example, the trade name "Irgacure 2959" manufactured by BASF), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (a commercially available product is, for example, the trade name "Darocur 1173" manufactured by BASF), and methoxyacetophenone.

[0264] Specific examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)-phenyl]-2-hydroxy-2-methylpropan-1-one, and the like.

[0265] Specific examples of aromatic sulfonyl chloride photopolymerization initiators include 2-naphthalenesulfonyl chloride.

[0266] Specific examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime.

[0267] Specific examples of benzoin-based photopolymerization initiators include benzoin.

[0268] Specific examples of benzyl-based photopolymerization initiators include benzyl.

[0269] Specific examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexyl phenyl ketone.

[0270] Specific examples of the ketal-based photopolymerization initiator include benzyl dimethyl ketal.

[0271] Specific examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

[0272] Specific examples of the acylphosphine photopolymerization initiator include bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-n-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-(1-methylpropan-1-yl)phosphine oxide, and bis(2,6-dimethoxybenzoyl)-(1-methylpropan-1-yl)phosphine oxide. tert-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)cyclohexylphosphine oxide, bis(2,6-dimethoxybenzoyl)octylphosphine oxide, bis(2-methoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2-methoxybenzoyl)(1-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(1-methylpropan Bis(2,6-dibutoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4-dimethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)(2,4-dipentoxyphenyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylpropylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2 -phenylethylphosphine oxide, bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylpropylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 2,6-dimethoxybenzoylbenzyloctylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diisopropylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-4-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,3,5,6-tetramethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)isobutylphosphine oxide, 2,6-dimethytoxybenzoyl-2,4,6-trimethylbenzoyl-n-butylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-dibutoxyphenylphosphine oxide, 1,10-bis[bis(2,4,6-trimethylbenzoyl)phosphine oxide]decane, tri(2-methylbenzoyl)phosphine oxide, etc.

[0273] From the viewpoint of exhibiting good polymerizability, the amount of the photopolymerization initiator used is preferably 5 parts by weight or less, more preferably 0.01 to 5 parts by weight, even more preferably 0.05 to 3 parts by weight, particularly preferably 0.05 to 1.5 parts by weight, and most preferably 0.1 to 1 part by weight, relative to 100 parts by weight of the total amount of the monomer components (m).

[0274] When UV polymerization is carried out, it is preferable to use a polyfunctional (meth)acrylate.

[0275] As the polyfunctional (meth)acrylate, any appropriate polyfunctional (meth)acrylate may be adopted as long as the effects of the present invention are not impaired. The polyfunctional (meth)acrylate may be of only one type or of two or more types. Specific examples of such polyfunctional (meth)acrylates include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexa(meth)acrylate, 1,2-hexa(meth)acrylate, 1,6 ... Examples of the polyhydric alcohol include ester compounds of polyhydric alcohol and (meth)acrylic acid, such as xanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl (meth)acrylate; vinyl (meth)acrylate; divinylbenzene; epoxy acrylate; polyester acrylate; urethane acrylate; butyl di(meth)acrylate; and hexyl di(meth)acrylate.

[0276] From the viewpoint of exhibiting good crosslinking properties, the amount of the polyfunctional (meth)acrylate used is preferably 5 parts by weight or less, more preferably 0.01 to 5 parts by weight, even more preferably 0.05 to 3 parts by weight, particularly preferably 0.05 to 1.5 parts by weight, and most preferably 0.1 to 1 part by weight, relative to 100 parts by weight of the total amount of the monomer components (m).

[0277] Any suitable UV polymerization method can be adopted as long as it does not impair the effects of the present invention. For example, the UV polymerization method includes mixing a photopolymerization initiator and, if necessary, a polyfunctional (meth)acrylate with the monomer component (m), and irradiating the mixture with ultraviolet light.

[0278] The weight-average molecular weight of the acrylic resin is preferably 100,000 to 3,000,000, more preferably 300,000 to 2,000,000, further preferably 500,000 to 1,500,000, and particularly preferably 500,000 to 1,000,000. The weight-average molecular weight is a value measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene. It may be difficult to measure the weight-average molecular weight of an acrylic resin obtained by active energy ray polymerization.

[0279] The adhesive layer (B) may contain any other appropriate components as necessary. Examples of other components include tackifiers, softeners, antioxidants, polyolefin resins, silicone resins, liquid acrylic copolymers, polyethyleneimines, fatty acid amides, phosphoric esters, light stabilizers such as hindered amine light stabilizers, ultraviolet absorbers, heat resistance stabilizers, fillers or pigments such as calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide, crosslinkers, surface lubricants, leveling agents, plasticizers, low molecular weight polymers, antioxidants, corrosion inhibitors, polymerization inhibitors, silane coupling agents, conductive agents, metal powders, colorants, foil-like materials, lubricants, solvents, catalysts, and other additives. The type, number, and amount of other components that can be contained in the adhesive layer can be appropriately set according to the purpose.

[0280] The surface of the adhesive layer (B) may be subjected to a surface treatment such as corona discharge treatment, ultraviolet irradiation treatment, flame treatment, plasma treatment, or sputter etching treatment, if necessary, for the purpose of controlling adhesion or improving application workability.

[0281] The pressure-sensitive adhesive layer (B) preferably contains a tackifier. The pressure-sensitive adhesive layer (B) contains a tackifier, which can improve the adhesive strength. However, the amount of the tackifier is appropriately determined depending on the adherend to which the surface protection sheet is applied in order to avoid the occurrence of adhesive residue problems due to a decrease in cohesive strength. The amount of the tackifier is preferably 80% by weight or less, more preferably 40% by weight or less, and even more preferably 20% by weight or less, based on the base polymer of the pressure-sensitive adhesive layer (B).

[0282] As the tackifier, for example, petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic-aromatic copolymers, and alicyclic copolymers, coumarone-indene resins, terpene resins, terpene phenol resins, rosin-based resins such as polymerized rosin, (alkyl)phenol resins, xylene resins, and hydrogenated versions of these, which are generally used for adhesives, can be used without any particular restrictions. Only one type of tackifier may be used, or two or more types may be used. Among these tackifiers, hydrogenated tackifiers are preferred from the viewpoints of releasability and weather resistance. In addition, tackifiers that are commercially available as blends with olefin resins can also be used.

[0283] The softening point of the tackifier is preferably 100° C. or higher, more preferably 105° C. or higher, even more preferably 110° C. or higher, and particularly preferably 115° C. or higher. The upper limit of the softening point is, for example, preferably 300° C. or lower, more preferably 250° C. or lower, and even more preferably 200° C. or lower.

[0284] The incorporation of a softener is effective in improving adhesive strength. Examples of softeners include low molecular weight diene polymers, polyisobutylene, hydrogenated polyisoprene, hydrogenated polybutadiene, and derivatives thereof. Examples of such derivatives include those having an OH group or a COOH group at one or both ends, and specifically include hydrogenated polybutadiene diol, hydrogenated polybutadiene monool, hydrogenated polyisoprene diol, and hydrogenated polyisoprene monool. In particular, hydrogenated products of diene polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene, and olefin-based softeners are preferred for the purpose of suppressing the improvement of adhesiveness to the adherend. Specifically, such softeners are available under the trade name "Kurapren LIR-200" manufactured by Kuraray Co., Ltd. These softeners may be used alone or in combination of two or more kinds.

[0285] The molecular weight of the softener can be set to any appropriate amount, but a smaller molecular weight may cause substances to migrate from the adhesive layer (B) to the adherend or cause heavy peeling, while a larger molecular weight tends to result in a poorer effect on improving adhesive strength. Therefore, the number average molecular weight of the softener is preferably 5,000 to 100,000, and more preferably 10,000 to 50,000.

[0286] When a softener is used, the amount of the softener added can be set to any appropriate amount, but since a large amount of the softener added tends to increase adhesive residue at high temperatures or when exposed to the outdoors, the amount of the softener added is preferably 100% by weight or less, more preferably 60% by weight or less, and even more preferably 40% by weight or less relative to the base polymer of the adhesive layer (B). When the adherend is a metal plate, it is preferable not to add a softener when forming the adhesive layer (B).

[0287] A polyolefin resin may be added to the adhesive layer (B) for the purpose of suppressing an increase in adhesive strength. The polyolefin resin may be of only one type or of two or more types. The amount of the polyolefin resin is preferably 50% by weight or less, more preferably 30% by weight or less, and even more preferably 20% by weight or less, based on the base polymer of the adhesive layer.

[0288] 2. Manufacturing method of surface protection film The surface protective film according to the embodiment of the present invention may be produced by any suitable method. Examples of such a production method include (1) A method of applying a solution or a hot melt of a material for forming the adhesive layer (B) onto the base layer (A); (2) A method of applying a solution or a hot melt of a material for forming the adhesive layer (B) onto a separator to form an adhesive layer (B), and transferring the formed adhesive layer (B) onto a base layer (A); (3) A method of forming and coating a material for forming the pressure-sensitive adhesive layer (B) on the base layer (A), (4) A method of extruding a base layer (A) and a pressure-sensitive adhesive layer (B) in two layers or multiple layers, (5) A method of laminating a single layer of a pressure-sensitive adhesive layer (B) on a base layer (A) or a method of laminating two layers of a pressure-sensitive adhesive layer (B) together with a laminate layer, (6) A method of laminating the pressure-sensitive adhesive layer (B) with a base layer-forming material such as a film or a laminate layer in two or more layers, The above-mentioned manufacturing method can be used in accordance with any suitable manufacturing method.

[0289] Examples of the coating method that can be used include a roll coater method, a comma coater method, a die coater method, a reverse coater method, a silk screen method, and a gravure coater method.

[0290] The substrate layer (A) can be manufactured by any suitable method. Examples of such manufacturing methods include extrusion molding of the materials of each layer constituting the substrate layer (A). For example, when the substrate layer (A) is a three-layer substrate layer (A1) / substrate layer (A2) / auxiliary substrate layer (A3), extrusion molding of three kinds of three layers can be exemplified. In addition, when the substrate layer (A1) / substrate layer (A2) / auxiliary substrate layer (A3) is a three-layer substrate layer, and the substrate layer (A1) and the auxiliary substrate layer (A3) are made of the same material, extrusion molding of two kinds of three layers can be exemplified.

[0291] ≪≪3.Applications≫≫ The surface protection film of the present invention can be used for any appropriate purpose. In view of the effects of the present invention, the surface protection film of the present invention is preferably used for manufacturing a member to be provided in a mobile device, and more preferably used for protecting the surface of a resin plate when the resin substrate is subjected to a heat press process. In this case, the heating temperature during the heat press process is preferably 50°C to 250°C, and more preferably 120°C to 250°C. EXAMPLES

[0292] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The test and evaluation methods in the examples and the like are as follows. In addition, when "parts" are described, it means "parts by weight" unless otherwise specified, and when "%" is described, it means "% by weight" unless otherwise specified.

[0293] <Highest peak temperature by DSC measurement> For the surface protection films of the examples and comparative examples, melting point measurement was performed using temperature-modulated DSC (trade name "Q-2000", manufactured by TA Instruments). Approximately 1 to 2 mg was sampled and weighed into an aluminum open cell as a sample piece, and the behavior of the Reversing Heat Flow (specific heat component) of the test piece was obtained at a heating rate of 10 °C / min under a nitrogen atmosphere of 50 ml / min. Referring to JIS-K-7121, the temperature at the point where a straight line equidistant from the vertical axis direction and the curve of the stepped change part accompanying melting intersect with the straight lines extending the baseline on the low-temperature side and the baseline on the high-temperature side of the obtained Reversing Heat Flow was defined as the "peak temperature (°C)" of each sample. When two or more peaks appeared, the higher-temperature peak temperature was defined as the "highest peak temperature (°C)". When measuring the melting point of the surface protection film by DSC, a plurality of peak temperatures derived from the composition of each layer provided in the surface protection film may be measured. In such a case, the "highest peak temperature" among the plurality of peak temperatures corresponds to the highest peak temperature of the heat-resistant base material layer (A1) possessed by the surface protection film in the embodiment of the present invention.

[0294] <High-temperature storage elastic modulus> The surface protection films of the examples and comparative examples were measured for tensile storage modulus (MPa) by dynamic viscoelasticity measurement using a dynamic viscoelasticity measuring device (product name "RSA-G3", manufactured by TA Instruments). In the measurement, the size of the surface protection film to be measured was 10 mm wide x 40 mm long, the initial chuck distance of the chuck for holding the sample piece was 10 mm, the measurement mode was tensile mode, the measurement temperature range was 25°C to 170°C, the frequency was 1 Hz, and the heating rate was 5°C / min. The measurement result at 120°C was taken as the high-temperature storage modulus. The high-temperature storage modulus (storage modulus at 120°C) is an index of the hardness of the surface protection film itself, and if this value is high, damage (yellow orange peel) is likely to occur on the surface of the resin substrate to which the surface protection film is attached.

[0295] <High temperature slipperiness evaluation> The evaluation was carried out as shown in FIG. 4. The surface protection films of the examples and comparative examples were cut to a size of 100 mm wide x 200 mm long, and the adhesive side was attached to a standard test plate (JISG3141: manufactured by Nippon Test Panel Co., Ltd.) using a double-sided tape (manufactured by Nitto Denko, No. 5610) having the same shape as the surface protection film, to obtain a test sample 200. Furthermore, a polyester film (Mitsubishi Plastics, Inc., MRF#38) having a thickness of 38 μm and having a silicone-based release treatment on one side was cut to a size of 100 mm wide x 100 mm long, and the non-release-treated side was attached to the standard test plate by using a double-sided tape (manufactured by Nitto Denko, No. 5610) having the same shape as the polyester film (300 in FIG. 4). A sliding piece 400 was placed on the polyester film, and the film was left to stand in a 130° C. environment for 5 minutes, and the dynamic friction force (N) of the outermost surface layer was measured in accordance with JISK7125. The contact area of ​​the sliding piece was 20 mm x 20 mm, and a SUS430BA plate measuring 0.4 mm thick x 20 mm x 20 mm was used for the surface that came into contact with the surface protective film. The total mass of the sliding piece including this SUS430BA plate was 100 g (0.98 N). Using a 50 N load cell 500, the sliding piece was pulled until it had moved 50 mm on the surface protective film at a sliding speed of 300 mm / min, and measurements were performed. The maximum stress detected was taken as the friction force value to evaluate the high-temperature sliding properties.

[0296] <Yellow peel resistance> After carrying out vacuum and compressed air molding in the same manner as in the measurement method for <mold adhesion prevention> described above, the test piece was peeled off from the PMMA plate. If the peeled surface had a visually confirmed transfer roughness of the surface of the SUS304 plate polished with sandpaper No. 360, it was marked as ×, and if not, it was marked as ◯.

[0297] <Molding conditions> In the examples and comparative examples, the substrates were molded using a three-kind, three-layer (A layer / B layer / C layer) extrusion T-die molding machine under the following extrusion temperature conditions. A layer: 200℃ B layer: 200℃ C layer: 200℃ Die temperature: 200℃ The materials were integrated by coextrusion molding from a T-die, and after the obtained substrate was sufficiently solidified, it was wound up into a roll to form a roll body.

[0298] [Example 1] A propylene-based resin (manufactured by Japan Polypropylene Corporation, product name: Wintec WFW4, a propylene / ethylene random polymer obtained by polymerization with a metallocene catalyst) was mixed with a silylated polyolefin master batch to prepare an A1 layer forming material (the mixing ratio of the silylated polyolefin master batch was 10% by weight, and the content ratio of the silylated polyolefin in the A1 layer forming material was 3% by weight). The silylated polyolefin master batch contained 30 parts of silylated polyolefin (prepared by the method shown in the examples of JP 2011-26448 A) as a release agent and 70 parts of low-density polyethylene resin. The above-mentioned A1 layer forming material was fed into the A1 layer of the extruder, low-density polyethylene (LDPE) (manufactured by Japan Polyethylene Corporation, product name: Novatec LD LC720) into the A2 layer of the extruder, and low-density polyethylene (LDPE) (manufactured by Japan Polyethylene Corporation, product name: Novatec LD LC720) into the A3 layer of the extruder, and a laminate with a total thickness of 55 μm, A1 layer / A2 layer / A3 layer = 5 μm / 25 μm / 25 μm, was extruded into a film to obtain the base layer (1). As an adhesive, a mixture of 100 parts of styrene-ethylene-butylene-styrene block copolymer (SEBS) (manufactured by Kraton, product name: Kraton G1657) and 40 parts of a tackifier (manufactured by Arakawa Chemical Industries, Ltd.: Alcon P-100) was prepared, dissolved in a dilution solvent (toluene), and applied to the surface of layer A3 of the above-mentioned base layer (1) and dried to form an adhesive layer with a thickness of 5 μm. In this manner, a surface protective film (1) was obtained. The results are shown in Table 1.

[0299] [Example 2] A surface protective film (2) was obtained in the same manner as in Example 1, except that the blending ratio of the silylated polyolefin master batch was 25% by weight (the content of silylated polyolefin in the A1 layer forming material was 7.5% by weight). The results are shown in Table 1.

[0300] [Example 3] A surface protective film (3) was obtained in the same manner as in Example 1, except that the thicknesses of the A1 layer / A2 layer / A3 layer were 10 μm / 50 μm / 50 μm, totaling 110 μm. The results are shown in Table 1.

[0301] [Example 4] A surface protection film (4) was obtained in the same manner as in Example 1, except that a pressure-sensitive adhesive layer with a thickness of 15 μm was formed. The results are shown in Table 1.

[0302] [Example 5] A surface protection film (5) was obtained in the same manner as in Example 1, except that polypropylene (PP) (manufactured by Japan Polypropylene Corporation, product name: Wintech WFW4) was used for the A3 layer of the extruder, and the thicknesses of the A1 layer / A2 layer / A3 layer were 2.5 μm / 50 μm / 2.5 μm, totaling 55 μm. The results are shown in Table 1.

[0303] [Example 6] A surface protection film (6) was obtained in the same manner as in Example 1, except that a high-density polyethylene (HDPE) (manufactured by Tosoh Corporation, product name: Nipolon Hard 4000) was used in the A1 layer of the extruder instead of a propylene-based resin (manufactured by Japan Polypropylene Corporation, product name: Wintech WFW4). The results are shown in Table 1.

[0304] [Example 7] A surface protection film (7) was obtained in the same manner as in Example 1, except that a propylene-based resin (manufactured by Japan Polypropylene Corporation, product name: Wintec WFW4) was replaced by a propylene-based resin (manufactured by Sumitomo Chemical, product name: Noblen FL6737, propylene / ethylene random polymer) in the A1 layer of the extruder, and the thicknesses of the A1 layer / A2 layer / A3 layer were 10 μm / 25 μm / 25 μm, totaling 60 μm. The results are shown in Table 1.

[0305] [Example 8] A surface protection film (8) was obtained in the same manner as in Example 7, except that the blending ratio of the silylated polyolefin master batch was 5% by weight (the content of silylated polyolefin in the A layer forming material was 1.5% by weight). The results are shown in Table 2.

[0306] [Example 9] A surface protection film (9) was obtained in the same manner as in Example 1, except that a propylene-based resin (manufactured by Japan Polypropylene Corporation, product name: Novatec PP SA06GA, a propylene homopolymer obtained by polymerization with a Ziegler catalyst) and a silylated polyolefin masterbatch were blended to prepare an A1 layer forming material (the blending ratio of the silylated polyolefin masterbatch was 25% by weight, and the content of the silylated polyolefin in the A1 layer forming material was 7.5% by weight). The results are shown in Table 2.

[0307] [Example 10] As an adhesive, a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirrer was used. To 100 parts of a monomer mixture consisting of 58 parts of butyl acrylate (BA), 40 parts of n-butyl methacrylate, and 2 parts of acrylic acid (AA), 2 parts of polyoxyethylene alkylpropenyl phenyl ether ammonium sulfate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name "Aqualon BC-2020"), 2 parts of polyoxyethylene dialkyl phenyl ether phosphoric acid (manufactured by Toho Chemical Industry Co., Ltd., product name "Phosphanol RE-410", pKa: 2,7 (mixture of monoester and diester)), 2.4 parts of a polymerization initiator, and 0.03 parts of 2,2'-azobis(2-amidinopropane) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., product name V-50) were added, and water was added to the desired solid content, followed by emulsion polymerization at 60 ° C. for 5 hours. After the polymerization was completed, 10% aqueous ammonia (Kishida Chemical Co., Ltd., trade name "10% aqueous ammonia") was added to the reaction solution to adjust the pH to 8.0, and an acrylic polymer emulsion was obtained. The SP value of the obtained acrylic polymer was 9.32, and Tg was -28.6°C. 100 parts of the solid content of this acrylic polymer emulsion was mixed with 2 parts of an oxazoline crosslinking agent (trade name "Epocross WS-500", Nippon Shokubai Co., Ltd.) to obtain an acrylic adhesive solution. A surface protection film (10) was obtained in the same manner as in Example 1, except that this adhesive solution was used as a material for forming the adhesive layer. The results are shown in Table 2.

[0308] [Example 11] A surface protection film (11) was obtained in the same manner as in Example 1, except that a mixture of 100 parts of styrene-ethylene-butylene-styrene block copolymer (SEBS) (manufactured by Kraton, product name: Kraton G1657) and 40 parts of a tackifier (manufactured by Arakawa Chemical Industries, Ltd.: Alcon P-100) was used for the A3 layer as the adhesive, the A1 layer / A2 layer / A3 layer=5 μm / 50 μm / 5 μm, total thickness of 60 μm, and no adhesive was applied to the surface of the A3 layer. The results are shown in Table 2.

[0309] [Example 12] A surface protection film (12) was obtained in the same manner as in Example 11, except that a polyolefin adhesive resin (Tafthren H5002, manufactured by Sumitomo Chemical Co., Ltd.) was used for the A3 layer. The results are shown in Table 2.

[0310] [Example 13] A surface protection film (13) was obtained in the same manner as in Example 1, except that ethylene / vinyl acetate copolymer (EVA) (manufactured by DuPont-Mitsui Polychemicals, product name: Evaflex EV550) was used for the A2 layer and the A3 layer of the extruder. The results are shown in Table 2.

[0311] [Example 14] A propylene-based resin (Japan Polypropylene, product name: Wintec WFW4, propylene / ethylene random polymer obtained by polymerization with a metallocene catalyst) was mixed with a silylated polyolefin master batch to prepare an A1 layer forming material (the mixing ratio of the silylated polyolefin master batch was 10% by weight, and the content of the silylated polyolefin in the A1 layer forming material was 3% by weight). The silylated polyolefin master batch contained 30 parts of silylated polyolefin (prepared by the method shown in the examples of JP 2011-26448 A) as a release agent and 70 parts of polypropylene resin. A surface protection film (14) was obtained in the same manner as in Example 1, except that this A1 layer-forming material was used for the A1 layer of the extruder. The results are shown in Table 2.

[0312] [Example 15] A crystalline pentene resin (manufactured by Mitsui Chemicals, product name: TPX MX002) using 4-methylpentene-1 as the main raw material was fed into the A1 layer of the extruder, a propylene resin (manufactured by Japan Polypropylene, product name: Wintech WFW4) was fed into the A2 layer of the extruder, and a propylene resin (manufactured by Japan Polypropylene, product name: Wintech WFW4) was fed into the A3 layer of the extruder, and a laminate with a total thickness of 30 μm, A1 layer / A2 layer / A3 layer = 5 μm / 15 μm / 10 μm, was extruded into a film to obtain the base layer (1). As an adhesive, a mixture of 100 parts of styrene-ethylene-butylene-styrene block copolymer (SEBS) (manufactured by Kraton Corporation, product name: Kraton G1657) and 40 parts of a tackifier (manufactured by Arakawa Chemical Industries, Ltd.: Alcon P-100) was prepared, dissolved in a dilution solvent (toluene), and applied to the surface of layer A3 of the above-mentioned base layer (1) and dried to form an adhesive layer with a thickness of 10 μm. In this manner, a surface protective film (15) was obtained. The results are shown in Table 3.

[0313] [Example 16] The same procedure as in Example 15 was carried out, except that a crystalline pentene resin mainly made of 4-methylpentene-1 (manufactured by Mitsui Chemicals, product name: TPX DX310) was fed into the A1 layer of the extruder instead of the crystalline pentene resin mainly made of 4-methylpentene-1 (manufactured by Mitsui Chemicals, product name: TPX MX002), to obtain a surface protection film (16). The results are shown in Table 3.

[0314] [Example 17] The same procedure as in Example 15 was carried out, except that a propylene-based resin (manufactured by Japan Polypropylene Corporation, product name: Wintec WFW4) was replaced by a propylene-based resin (manufactured by Sumitomo Chemical, product name: Noblen FL6737, propylene / ethylene random polymer) was fed into each of the A2 layer and A3 layer of the extruder, to obtain a surface protection film (17). The results are shown in Table 3.

[0315] [Example 18] The same procedure as in Example 15 was carried out, except that a propylene-based resin (manufactured by Japan Polypropylene Corporation, product name: Wintec WFW4) was replaced by a propylene-based resin (manufactured by Sumitomo Chemical, product name: Noblen FS2011DG3, homopolypropylene) was fed into each of the A2 layer and A3 layer of the extruder, to obtain a surface protection film (18). The results are shown in Table 3.

[0316] [Example 19] A surface protection film (19) was obtained in the same manner as in Example 18, except that a mixture of 100 parts of styrene-ethylene-butylene-styrene block copolymer (SEBS) (manufactured by Kraton, product name: Kraton G1657) and 40 parts of a tackifier (manufactured by Arakawa Chemical Industries, Ltd.: Alcon P-100) was used for the A3 layer as the adhesive, the A1 layer / A2 layer / A3 layer=5 μm / 25 μm / 10 μm, total thickness of 40 μm, and no adhesive was applied to the surface of the A3 layer. The results are shown in Table 3.

[0317] [Example 20] A surface protection film (20) was obtained in the same manner as in Example 15, except that the thickness of the A1 layer was changed to 10 μm. The results are shown in Table 3.

[0318] [Example 21] As an adhesive, a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirrer was used. To 100 parts of a monomer mixture consisting of 58 parts of butyl acrylate (BA), 40 parts of n-butyl methacrylate, and 2 parts of acrylic acid (AA), 2 parts of polyoxyethylene alkylpropenyl phenyl ether ammonium sulfate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name "Aqualon BC-2020"), 2 parts of polyoxyethylene dialkyl phenyl ether phosphoric acid (manufactured by Toho Chemical Industry Co., Ltd., product name "Phosphanol RE-410", pKa: 2,7 (mixture of monoester and diester)), 2.4 parts of a polymerization initiator, and 0.03 parts of 2,2'-azobis(2-amidinopropane) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., product name V-50) were added, and water was added to the desired solid content, followed by emulsion polymerization at 60 ° C. for 5 hours. After the polymerization was completed, 10% ammonia water (Kishida Chemical Co., Ltd., trade name "10% ammonia water") was added to the reaction solution to adjust the pH to 8.0, and an acrylic polymer emulsion was obtained. The SP value of the obtained acrylic polymer was 9.32, and Tg was -28.6°C. 100 parts of the solid content of this acrylic polymer emulsion was mixed with 2 parts of an oxazoline crosslinking agent (trade name "Epocross WS-500", Nippon Shokubai Co., Ltd.) to obtain an acrylic adhesive solution. A surface protection film (21) was obtained in the same manner as in Example 15, except that this adhesive solution was used as a material for forming the adhesive layer. The results are shown in Table 3.

[0319] [Comparative Example 1] A surface protection film (C1) was obtained in the same manner as in Example 1, except that the blending ratio of the silylated polyolefin masterbatch was 0% by weight. The results are shown in Table 4.

[0320] [Comparative Example 2] A surface protection film (C2) was obtained in the same manner as in Example 1, except that an A1 layer forming material consisting of low-density polyethylene (LDPE) (manufactured by Japan Polyethylene Corporation, product name: Novatec LD LC720) and 0 wt% silylated polyolefin masterbatch was used for the A1 layer of the extruder. The results are shown in Table 4.

[0321] [Comparative Example 3] A surface protection film (C3) was obtained in the same manner as in Example 1, except that an A layer forming material consisting of low-density polyethylene (LDPE) (manufactured by Japan Polyethylene Corporation, product name: Novatec LD LC720) and 5 wt% silylated polyolefin masterbatch was used for the A1 layer of the extruder. The results are shown in Table 4.

[0322] [Comparative Example 4] A surface protection film (C4) was obtained in the same manner as in Example 1, except that a propylene-based resin (manufactured by Japan Polypropylene Corporation, product name: Novatec PP SA06GA) was used as the base resin for the A1 layer, A2 layer, and A3 layer of the extruder. The results are shown in Table 4.

[0323] [Comparative Example 5] A surface protection film (C5) was obtained in the same manner as in Example 1, except that a polyethylene terephthalate (PET) film (manufactured by Mitsubishi Plastics, Inc., Diafoil T100, thickness 100 μm) was used as the substrate. The results are shown in Table 4.

[0324] [Table 1]

[0325] [Table 2]

[0326] [Table 3]

[0327] [Table 4] [Industrial Applicability]

[0328] The surface protective film of the present invention can be used, for example, in the manufacture of members to be provided in mobile devices. [Explanation of symbols]

[0329] 100 Surface protection film 10 Base material layer (A) 11 Base material layer (A1) 12 Base material layer (A2) 13 Auxiliary base material layer (A3) 20 Adhesive layer (B) 200 Test sample with the adhesive layer of the surface protection film attached to a standard test plate with double-sided tape 300: The location where the non-release treated side of the release treated polyester film was attached to the test sample 200 400 Slide 500 50N Load Cell

Claims

1. A surface protection film having a base layer (A) and a pressure-sensitive adhesive layer (B), The substrate layer (A) includes a substrate layer (A1), a substrate layer (A2), and an auxiliary substrate layer (A3) in this order; the base material layer (A1) is an outermost layer on the side opposite to the pressure-sensitive adhesive layer (B) of the base material layer (A); The frictional force of the base layer (A1) at 130°C is 4.5 N or less, The storage modulus at 120°C is 50 MPa or less, The total thickness is 20 μm to 180 μm, The thickness of the substrate layer (A1) is 1 μm to 60 μm, The thickness of the substrate layer (A2) is 10 μm to 125 μm, The thickness of the auxiliary substrate layer (A3) is 2 μm to 60 μm, The thickness of the pressure-sensitive adhesive layer (B) is 5 μm to 50 μm. Surface protection film.

2. The surface protective film according to claim 1, wherein the entire thickness of the substrate layer (A) is 30 μm to 150 μm.

3. The surface protective film according to claim 1 or 2, wherein the substrate layer (A1) has a maximum peak temperature of 130° C. or higher as measured by DSC.

4. The surface protective film according to claim 1 , wherein the base layer (A1) contains a release agent.

5. The surface protective film according to claim 4, wherein the content of the release agent in the base layer (A1) is 0.1% by weight to 30% by weight.

6. The surface protective film according to claim 4 or 5, wherein the release agent comprises a silicone-based release agent.

7. The surface protective film of claim 6 , wherein the silicone-based release agent comprises a silylated polyolefin.

8. The surface protective film according to claim 1 , wherein the base layer (A1) contains at least one resin selected from an ethylene-based resin and a propylene-based resin.

9. The surface protective film according to claim 8 , wherein the ethylene-based resin comprises high density polyethylene.

10. The surface protective film according to claim 8 or 9, wherein the propylene-based resin comprises at least one selected from the group consisting of random polypropylene, block polypropylene, and homopolypropylene.

11. The surface protective film according to claim 1 , wherein the substrate layer (A1) comprises a pentene resin.

12. The surface protective film according to claim 1 , wherein the base layer (A2) comprises an ethylene-based resin.

13. The surface protective film according to claim 12, wherein the ethylene-based resin comprises at least one selected from low-density polyethylene and an ethylene-vinyl acetate copolymer.

14. The surface protective film according to claim 1 , wherein the base layer (A2) comprises a propylene-based resin.

15. The surface protective film according to claim 14 , wherein the propylene-based resin comprises homopolypropylene.

16. 16. The surface protective film according to claim 1, wherein the error between the thickness of the auxiliary base layer (A3) and the thickness of the base layer (A1) is ±50% or less.

17. A surface protective film according to any one of claims 1 to 16, wherein the main component resin contained in the auxiliary substrate layer (A3) is the same type of resin as the main component resin contained in the substrate layer (A1).

18. The surface protection film according to claim 1 , which is used in the manufacture of a member to be provided in a mobile device.

19. 19. The surface protective film according to claim 1, which is used to protect the surface of a resin plate when the resin plate is subjected to hot press processing.

20. The surface protective film according to claim 19, wherein the heating temperature during the hot press processing is 50°C to 250°C.

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