JP7236366B2 - surface protection film - Google Patents

Description

The present invention relates to a surface protection film. Typically, the present invention relates to a surface protective film used for manufacturing members provided in mobile devices.

In recent years, the mobile communication performance of so-called mobile devices such as smart phones, tablet terminals, and notebook computers has been rapidly improving. In particular, recently, new high-performance mobile communication standards (such as the 5G standard) that can enable ultra-high speed, ultra-large capacity, ultra-low delay, and ultra-mass connections are being adopted.

In order to fully realize the performance of such new high-performance mobile communications, it is necessary to use a material that is less susceptible to radio waves for the housing of mobile devices. For this reason, there is a need to replace metal housings, which have hitherto been widely used as housings for mobile devices, with resin housings that are less susceptible to radio waves.

On the other hand, in recent years, the designability of mobile devices has been greatly improved, and mobile devices having a casing having a three-dimensional curved surface structure have become common.

When the housing of the mobile device is a metal housing, it is possible to make the housing having various three-dimensional curved surface structures by the established metal processing technology.

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

A heat press is generally employed to process a resin substrate. In this hot press, the resin substrate is sandwiched between molds designed to have a desired shape and pressed at a high temperature. At this time, in order to protect the surface of the resin substrate, surface protective films are attached to both surfaces of the resin substrate.

However, when a conventional surface protective film is used for hot pressing of a resin substrate, the surface protective film tends to adhere to the mold due to melting or the like. If such a surface protective film adheres to the mold, there are problems such as a low yield in the hot press process.

In addition, when a conventional surface protective film (Patent Document 1) is used for hot pressing of a resin substrate, the position of the surface protective film is likely to occur due to the pressing at high temperature, and the surface of the resin substrate after pressing has a citrus peel. There is a problem that traces) occur.

Furthermore, in order to process the three-dimensional curved surface of the resin substrate by heat pressing, the surface protective films attached to both surfaces of the resin substrate must have appropriate softness. That is, if the surface protective films adhered to both surfaces of the resin substrate are too hard, it becomes difficult to follow the three-dimensional curved shape of the mold, and the surface protective films adhered to both surfaces of the resin substrate are too soft. If it is too large, the surface protective film may be misaligned or wrinkled (Patent Document 1).

JP-A-5-302068

An object of the present invention is to suppress adhesion of the surface protective film to the mold after the hot pressing in a process of hot-pressing a resin substrate to which a surface protective film is adhered with a mold. To provide a surface protective film which can be adhered to a resin substrate, which can suppress the subsequent citrus peel on the surface of the resin substrate, has appropriate softness for smoothly performing the hot pressing process.

The surface protection film in the embodiment of the present invention is
A surface protective film having a substrate layer (A) and an adhesive layer (B),
The substrate layer (A) comprises a heat-resistant substrate layer (A1),
The heat-resistant substrate layer (A1) is the outermost layer on the opposite side of the adhesive layer (B) of the substrate layer (A) and has a maximum peak temperature of 130° C. or higher by DSC measurement,
The storage elastic modulus at 120°C is 50 MPa or less.

In one embodiment, the surface protective film in the embodiment of the invention has a total thickness of 80 μm to 180 μm.

In one embodiment, the total thickness of the substrate layer (A) is 70 μm to 150 μm.

In one embodiment, the heat-resistant substrate layer (A1) has a thickness of 2 μm to 60 μm.

In one embodiment, the heat-resistant substrate layer (A1) contains a propylene-based resin as a main component.

In one embodiment, the propylene-based resin is at least one selected from random polypropylene, block polypropylene, and homopolypropylene.

In one embodiment, the substrate layer (A) includes the heat-resistant substrate layer (A1) and the soft substrate layer (A2) in this order.

In one embodiment, the soft base material layer (A2) contains an ethylene-based resin as a main component.

In one embodiment, the ethylene-based resin (A2) is at least one selected from low-density polyethylene and ethylene-vinyl acetate copolymer.

In one embodiment, the substrate layer (A) includes the heat-resistant substrate layer (A1), the soft substrate layer (A2), and the auxiliary substrate layer (A3) in this order.

In one embodiment, the error between the thickness of the auxiliary base layer (A3) and the thickness of the heat-resistant base layer (A1) is ±50% or less.

In one embodiment, the main component resin contained in the auxiliary base layer (A3) is the same as the main component resin contained in the heat resistant base layer (A1).

In one embodiment, the surface protective film in the embodiment of the present invention is used for manufacturing members provided in mobile devices.

In one embodiment, the surface protection film in the embodiment of the present invention is used to protect the surface of a resin plate when the resin substrate is heat-pressed.

In one embodiment, the heating temperature during the hot pressing is 50°C to 180°C.

According to the present invention, in a step of hot-pressing a resin substrate to which a surface protective film is adhered with a mold, the adhesion of the surface protective film to the mold after the hot-pressing can be suppressed, and the hot-pressing can be performed. It is possible to provide a surface protective film that can be adhered to a resin substrate, and that can suppress citrus peel on the surface of the resin substrate afterward, and has appropriate softness to facilitate the hot-pressing step.

1 is a schematic cross-sectional view of a surface protection film according to one embodiment of the present invention; FIG.

FIG. 4 is a schematic cross-sectional view of a surface protection film according to another embodiment of the present invention;

FIG. 4 is a schematic cross-sectional view of a surface protection film according to still another embodiment of the present invention;

<<<1. Surface protection film>>>>
A surface protective film in an embodiment of the present invention is a surface protective film having a substrate layer (A) and an adhesive layer (B), wherein the substrate layer (A) comprises a heat-resistant substrate layer (A1). , the heat-resistant substrate layer (A1) is the outermost layer of the substrate layer (A) on the side opposite to the pressure-sensitive adhesive layer (B).

The surface protection film in the embodiment of the invention may have any suitable other layer within a range that does not impair the effects of the invention.

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

The substrate layer (A) preferably includes a heat-resistant substrate layer (A1) and a soft substrate layer (A2) in this order.

The substrate layer (A) more preferably comprises a heat resistant substrate layer (A1), a soft substrate layer (A2) and an auxiliary substrate layer (A3) in this order.

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.

The total thickness of the surface protection film in the embodiment of the invention is preferably 80 μm to 180 μm, more preferably 80 μm to 160 μm, still more preferably 85 μm to 150 μm, and particularly preferably 90 μm to 140 μm. If the total thickness of the surface protective film in the embodiment of the present invention is within the above range, the effects of the present invention can be exhibited more effectively. If the total thickness of the surface protective film in the embodiment of the present invention is too thin, when it is used for heat-pressing a resin substrate, it may not be able to fully function as a surface protective film. There is a risk that the surface protective film may be easily misaligned or wrinkled. If the total thickness of the surface protective film in the embodiment of the present invention is too thick, when it is used for hot pressing of a resin substrate, it may not be able to sufficiently fulfill its role as a surface protective film. It may be difficult to

The thickness of the entire substrate layer (A) is preferably 70 μm to 150 μm, more preferably 75 μm to 140 μm, even more preferably 80 μm to 135 μm, particularly preferably 85 μm to 135 μm. If the thickness of the entire base material layer (A) is within the above range, the effect of the present invention can be exhibited more effectively. If the thickness of the entire substrate layer (A) is too thin, when it is used for heat-pressing a resin substrate, it may not fully function as a surface protective film. positional deviation and wrinkles may easily occur. If the total thickness of the base layer (A) is too thick, when used for hot pressing of a resin substrate, the role of the surface protection film may not be sufficiently exhibited. It can be difficult.

The surface protective film in the embodiment of the present invention has a maximum peak temperature measured by DSC of preferably 130° C. or higher, more preferably 130° C. to 250° C., still more preferably 130° C. to 220° C., especially It is preferably 130°C to 200°C, most preferably 130°C to 180°C. If the highest peak temperature measured by DSC of the surface protection film in the embodiment of the invention is within the above range, the heat resistance can be excellent, and the effects of the invention can be more manifested. If the maximum peak temperature measured by DSC of the surface protective film in the embodiment of the present invention is too low, the heat resistance is poor, and when the resin substrate is hot pressed, the surface protective film adheres to the mold due to melting or the like. In addition, there is a risk that the surface protective film may be easily misaligned or wrinkled by pressing at a high temperature. If the maximum peak temperature measured by DSC of the surface protective film in the embodiment of the present invention is too high, it becomes difficult for the surface protective film to follow the three-dimensional curved shape of the mold when used for hot pressing of a resin substrate. There is a risk.

The surface protective film in the embodiment of the present invention preferably has a storage modulus at 120° C. of 50 MPa or less, more preferably 50 MPa to 0.5 MPa, even more preferably 50 MPa to 1 MPa, and particularly preferably 45 MPa. ˜1.5 MPa, most preferably 40 MPa to 2 MPa. If the storage elastic modulus at 120° C. of the surface protective film in the embodiment of the present invention is within the above range, the surface protective film has appropriate softness, and when used for heat pressing of a resin substrate, a good three-dimensional Curved surface processing can be achieved. If the storage elastic modulus at 120° C. of the surface protective film in the embodiment of the present invention is too low, the surface protective film is too soft, which may cause misalignment or wrinkles. If the storage elastic modulus at 120° C. of the surface protective film in the embodiment of the present invention is too high, the surface protective film is too hard and may become difficult to follow the three-dimensional curved shape of the mold.

FIG. 1 is a schematic cross-sectional view of a surface protection film according to one embodiment of the invention. In FIG. 1, the surface protection film 100 has a substrate layer (A) 10 and an adhesive layer (B) 20, and the outermost layer on the side opposite to the adhesive layer (B) of the substrate layer (A) is a heat-resistant layer. It is the base material layer (A1) 11 .

FIG. 2 is a schematic cross-sectional view of a surface protection film according to another embodiment of the invention. In FIG. 2, the surface protection film 100 has a base layer (A) 10 and an adhesive layer (B) 20, and the outermost layer on the opposite side of the base layer (A) to the adhesive layer (B) is a heat-resistant layer. It is a substrate layer (A1) 11 and has a soft substrate layer (A2) 12 between the heat-resistant substrate layer (A1) 11 and the adhesive layer (B) 20 . That is, the surface protective film 100 shown in FIG. 2 has a heat-resistant substrate layer (A1) 11, a soft substrate layer (A2) 12, and an adhesive layer (B) 20 in this order.

FIG. 3 is a schematic cross-sectional view of a surface protection film according to yet another embodiment of the invention. In FIG. 3, the surface protection film 100 has a substrate layer (A) 10 and an adhesive layer (B) 20, and the outermost layer on the side opposite to the adhesive layer (B) of the substrate layer (A) is a heat-resistant layer. It is a base layer (A1) 11, has a soft base layer (A2) 12 between the heat-resistant base layer (A1) 11 and the adhesive layer (B) 20, and has a soft base layer (A2) 12 It has an auxiliary substrate layer (A3) 13 between the adhesive layers (B) 20 . That is, the surface protection film 100 shown in FIG. 3 has a heat-resistant substrate layer (A1) 11, a soft substrate layer (A2) 12, an auxiliary substrate layer (A3) 13, and an adhesive layer (B) 20 in this order. .

<<1-1. Base layer (A)>>
As shown in FIGS. 1 to 3, the substrate layer (A) includes a heat-resistant substrate layer (A1) as the outermost layer opposite to the pressure-sensitive adhesive layer (B).

The substrate layer (A) preferably includes a heat-resistant substrate layer (A1) and a soft substrate layer (A2) in this order, as shown in FIGS.

The substrate layer (A) more preferably comprises a heat resistant substrate layer (A1), a soft substrate layer (A2) and an auxiliary substrate layer (A3) in this order, as shown in FIG.

The base material layer (A) as a whole preferably contains an olefin resin as a main component. Specifically, the content of the olefin-based resin contained in the entire substrate layer (A) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, and further Preferably 90% to 100% by weight, particularly preferably 95% to 100% by weight, most preferably substantially 100% by weight. When the substrate layer (A) as a whole contains an olefin-based resin as a main component, the effect of the present invention can be further exhibited.

In the present specification, the term "substantially 100% by weight" means that a trace amount of impurities may be contained within a range that does not impair the effects of the present invention, and usually may be referred to as "100% by weight".

The olefin resin contained in the entire substrate layer (A) may be of only one type, or may be of two or more types.

As the olefin resin, any suitable olefin resin can be adopted as long as the effects of the present invention are not impaired. From the point of view that the effects of the present invention can be more expressed, such olefin-based resins include, for example, at least one selected from ethylene-based resins, propylene-based resins, and butene-based resins, preferably ethylene-based resins. At least one selected from resins and propylene-based resins is included.

As the ethylene-based resin, any appropriate ethylene-based resin can be adopted as long as the effects of the present invention are not impaired. Such ethylene-based resins include, for example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra low density polyethylene, medium density polyethylene (MDPE), high density polyethylene (HDPE), ultra 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 low-density polyethylene and ethylene/vinyl acetate copolymer.

The ethylene-based resin may be a metallocene-based ethylene-based resin obtained using a metallocene catalyst.

As the propylene-based resin, any appropriate propylene-based resin can be adopted as long as the effects of the present invention are not impaired. Such propylene-based resins include, for example, at least one selected from random polypropylene, block polypropylene, homopolypropylene, and copolymers of propylene and other monomers.

The propylene-based resin may be a metallocene-based propylene-based resin obtained using a metallocene catalyst.

As the butene-based resin, any suitable butene-based resin can be adopted as long as the effects of the present invention are not impaired. Examples of such butene-based resins include at least one selected from polybutene-1 and copolymers of butene-1 and α-olefins.

The butene-based resin may be a metallocene-based butene-based resin obtained using a metallocene catalyst.

The base material layer (A) may contain any appropriate other resin component within a range that does not impair the effects of the present invention.

<1-1-1. Heat-resistant substrate layer (A1)>
The heat-resistant substrate layer (A1) is the outermost layer of the substrate layer (A) on the side opposite to the adhesive layer (B).

The thickness of the heat-resistant substrate layer (A1) is preferably 2 μm to 60 μm, more preferably 3 μm to 50 μm, even more preferably 4 μm to 40 μm, particularly preferably 5 μm to 30 μm. If the thickness of the heat-resistant substrate layer (A1) is within the above range, the effects of the present invention can be exhibited more effectively. If the thickness of the heat-resistant substrate layer (A1) is too thin, the heat resistance is poor, and when used for hot pressing of a resin substrate, the surface protective film may easily adhere to the mold due to melting or the like. Pressing at a high temperature may cause the surface protective film to be easily misaligned or wrinkled. If the thickness of the heat-resistant substrate layer (A1) is too thick, it may become difficult to follow the shape of a mold, for example, when it is used for hot pressing of a resin substrate.

The heat-resistant substrate layer (A1) may consist of only one layer, or may consist of two or more layers. When the heat-resistant substrate layer (A1) has two or more layers, each layer may have the same composition, or at least one layer may be a different layer.

The heat-resistant substrate layer (A1) preferably has 1 to 5 layers, more preferably 1 to 3 layers, still more preferably 1 to 2 layers, and particularly preferably 1 layer.

The heat-resistant substrate layer (A1) may contain any appropriate resin within a range that does not impair the effects of the present invention. The heat-resistant substrate layer (A1) preferably contains a propylene-based resin as a main component. When the heat-resistant substrate layer (A1) contains a propylene-based resin as a main component, the effects of the present invention can be further exhibited. In particular, since the heat-resistant substrate layer (A1) contains a propylene-based resin as a main component, the outermost surface of the substrate layer (A) can have excellent heat resistance, so that the effects of the present invention can be further exhibited. If the heat-resistant substrate layer (A1) does not contain a propylene-based resin as a main component, the heat resistance of the outermost surface of the substrate layer (A) may deteriorate. When used for hot press, the surface protective film may easily adhere to the mold due to melting, etc., and the surface protective film may be easily misaligned or wrinkled by pressing at high temperatures. .

The content of the propylene-based resin in the heat-resistant substrate layer (A1) is preferably 50% to 100% by weight, more preferably 70% to 100% by weight, and still more preferably 90% to 100% by weight. % by weight, particularly preferably 95% to 100% by weight, most preferably substantially 100% by weight. If the content of the propylene-based resin in the heat-resistant substrate layer (A1) is within the above range, the effects of the present invention can be more exhibited. In particular, when the content of the propylene-based resin in the heat-resistant substrate layer (A1) is within the above range, the outermost surface of the substrate layer (A) can have excellent heat resistance, so that the effects of the present invention are exhibited more. obtain. If the content of the propylene-based resin in the heat-resistant substrate layer (A1) is out of the above range, the heat resistance of the outermost surface of the substrate layer (A) may deteriorate. When is used for heat pressing of a resin substrate, the surface protective film may easily adhere to the mold due to melting, etc., and the surface protective film may be easily misaligned or wrinkled by pressing at high temperatures. may become

As the propylene-based resin, any appropriate propylene-based resin can be adopted as long as the effects of the present invention are not impaired. Such propylene-based resins include, for example, at least one selected from random polypropylene, block polypropylene, homopolypropylene, and copolymers of propylene and other monomers.

The propylene-based resin may be used alone or in a blend of two or more.

Homopolypropylene typically includes isotactic homopolypropylene, atactic homopolypropylene, syndiotactic homopolypropylene and the like.

As the copolymer of propylene and other monomers, any appropriate copolymer can be adopted as long as the effects of the present invention are not impaired. Examples of such copolymers of propylene and other monomers include propylene/ethylene copolymers, propylene/ethylene/1-butene copolymers, and propylene/α-olefins having 5 to 12 carbon atoms. A copolymer etc. are mentioned.

The propylene-based resin may be a metallocene-based propylene-based resin obtained using a metallocene catalyst. Such metallocene-based propylene-based resins include, for example, at least one selected from metallocene-based random polypropylene, metallocene-based block polypropylene, metallocene-based homopolypropylene, and copolymers of metallocene-based propylene and other monomers. is mentioned.

A commercially available product may be used as the propylene-based resin.

The heat-resistant substrate layer (A1) may contain any appropriate other resin component within a range that does not impair the effects of the present invention.

The heat-resistant substrate layer (A1) may contain any appropriate additive as necessary. Additives that may be contained in the heat-resistant substrate layer (A1) include, for example, release agents, ultraviolet absorbers, heat-resistant stabilizers, fillers, lubricants, coloring agents (dyes, etc.), antioxidants, and anti-staining agents. agents, antiblocking agents, foaming agents, polyethyleneimines, and the like. These may be one kind or two or more kinds. The content of the additive in the heat-resistant substrate layer (A1) is preferably 10% by weight or less, more preferably 7% by weight or less, still more preferably 5% by weight or less, and particularly preferably 2% by weight. % or less, and most preferably 1 wt % or less.

Examples of release agents include fatty acid amide-based release agents, silicone-based release agents, fluorine-based release agents, and long-chain alkyl-based release agents. From the standpoint of forming a release layer with an excellent balance between releasability and contamination resistance due to bleeding out, fatty acid amide release agents are preferred, and saturated fatty acid bisamides are more preferred. Any appropriate content can be adopted as the content of the release agent. Typically, it is preferably 0.01% by weight to 5% by weight with respect to the resin component (preferably propylene-based resin) in the heat-resistant substrate layer (A1).

Examples of ultraviolet absorbers include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. Any appropriate content can be adopted as the content of the ultraviolet absorber as long as it does not bleed out during molding. Typically, it is preferably 0.01% by weight to 5% by weight with respect to the resin component (preferably propylene-based resin) in the heat-resistant substrate layer (A1).

Examples of heat-resistant stabilizers include hindered amine-based compounds, phosphorus-based compounds, and cyanoacrylate-based compounds. Any appropriate content can be adopted as the content of the heat stabilizer as long as it does not bleed out during molding. Typically, it is preferably 0.01% by weight to 5% by weight with respect to the resin component (preferably propylene-based resin) in the heat-resistant substrate layer (A1).

Examples of fillers 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 between 0.1 μm and 20 μm. Any appropriate content can be adopted as the content of the filler. Typically, it is preferably 1% by weight to 200% by weight with respect to the resin component (preferably propylene-based resin) in the heat-resistant substrate layer (A1).

<1-1-2. Soft substrate layer (A2)>
The substrate layer (A) preferably includes a heat-resistant substrate layer (A1) and a soft substrate layer (A2) in this order. That is, the soft substrate layer (A2) is arranged between the heat-resistant substrate layer (A1) and the adhesive layer (B).

The thickness of the soft substrate layer (A2) is preferably 25 μm to 125 μm, more preferably 30 μm to 120 μm, even more preferably 40 μm to 105 μm, and particularly preferably 50 μm to 90 μm. If the thickness of the soft base material layer (A2) is within the above range, the effects of the present invention can be exhibited more effectively. If the thickness of the soft base material layer (A2) is too thin, the surface protection film is too hard, and it may become difficult to follow the three-dimensional curved shape of the mold. If the thickness of the soft base material layer (A2) is too thick, the surface protective film is too soft, and the surface protective film may be misaligned or wrinkled.

The soft base material layer (A2) may consist of only one layer, or may consist of two or more layers. When the soft base material layer (A2) is two or more layers, each layer may be a layer having the same composition, or at least one layer may be a different layer.

The soft substrate layer (A2) preferably has 1 to 5 layers, more preferably 1 to 3 layers, still more preferably 1 to 2 layers, and particularly preferably 1 layer.

The flexible base material layer (A2) may contain any suitable resin as long as the effects of the present invention are not impaired. The soft base material layer (A2) preferably contains an ethylene-based resin as a main component. When the soft base material layer (A2) contains an ethylene-based resin as a main component, the effects of the present invention can be exhibited more. In particular, since the flexible base material layer (A2) contains an ethylene-based resin as a main component, the surface protective film in the embodiment of the present invention has appropriate softness, and when used for heat-pressing a resin substrate, Good three-dimensional curved surface machining can be achieved. If the flexible base material layer (A2) does not contain an ethylene-based resin as a main component, the surface protective film in the embodiment of the present invention may not have appropriate softness, and misalignment and wrinkles of the surface protective film may occur. In addition, it may become difficult to follow the three-dimensional curved shape of the mold.

The content of the ethylene-based resin in the soft base material layer (A2) is preferably 50 wt% to 100 wt%, more preferably 70 wt% to 100 wt%, still more preferably 90 wt% to 100 wt%. % by weight, particularly preferably 95% to 100% by weight, most preferably substantially 100% by weight. If the content of the ethylene-based resin in the soft base material layer (A2) is within the above range, the effects of the present invention can be exhibited more effectively. In particular, when the content of the ethylene-based resin in the flexible base layer (A2) is within the above range, the surface protective film in the embodiment of the present invention has appropriate softness, and is suitable for heat pressing of the resin substrate. When used, good three-dimensional curved surface processing can be achieved. If the content of the ethylene-based resin in the flexible substrate layer (A2) is out of the above range, the surface protective film in the embodiment of the present invention may not have appropriate softness. There is a risk of misalignment or wrinkles, and it may be difficult to follow the three-dimensional curved shape of the mold.

As the ethylene-based resin, any appropriate ethylene-based resin can be adopted as long as the effects of the present invention are not impaired. Such ethylene-based resins include, for example, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra low density polyethylene, medium density polyethylene (MDPE), high density polyethylene (HDPE), ultra 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 low-density polyethylene and ethylene-vinyl acetate copolymer.

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

A commercially available product may be used as the ethylene-based resin.

The flexible base material layer (A2) may contain any appropriate other resin component within a range that does not impair the effects of the present invention.

The soft base material layer (A2) may contain any appropriate additive as necessary. Additives that can be contained in the soft base layer (A2) include, for example, mold release agents, ultraviolet absorbers, heat stabilizers, fillers, lubricants, colorants (dyes, etc.), antioxidants, and anti-staining agents. agents, antiblocking agents, foaming agents, polyethyleneimines, and the like. These may be one kind or two or more kinds. The content of the additive in the soft substrate layer (A2) is preferably 10% by weight or less, more preferably 7% by weight or less, still more preferably 5% by weight or less, and particularly preferably 2% by weight. % or less, and most preferably 1 wt % or less.

Examples of release agents include fatty acid amide-based release agents, silicone-based release agents, fluorine-based release agents, and long-chain alkyl-based release agents. From the standpoint of forming a release layer with an excellent balance between releasability and contamination resistance due to bleeding out, fatty acid amide release agents are preferred, and saturated fatty acid bisamides are more preferred. Any appropriate content can be adopted as the content of the release agent. Typically, it is preferably 0.01% by weight to 5% by weight with respect to the resin component (preferably ethylene-based resin) in the soft base material layer (A2).

Examples of ultraviolet absorbers include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. Any appropriate content can be adopted as the content of the ultraviolet absorber as long as it does not bleed out during molding. Typically, it is preferably 0.01% by weight to 5% by weight with respect to the resin component (preferably ethylene-based resin) in the soft base material layer (A2).

Examples of heat-resistant stabilizers include hindered amine-based compounds, phosphorus-based compounds, and cyanoacrylate-based compounds. Any appropriate content can be adopted as the content of the heat stabilizer as long as it does not bleed out during molding. Typically, it is preferably 0.01% by weight to 5% by weight with respect to the resin component (preferably ethylene-based resin) in the soft base material layer (A2).

Examples of fillers 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 between 0.1 μm and 20 μm. Any appropriate content can be adopted as the content of the filler. Typically, it is preferably 1% by weight to 200% by weight with respect to the resin component (preferably ethylene-based resin) in the soft base material layer (A2).

<1-1-3. Auxiliary base material layer (A3)>
The substrate layer (A) preferably comprises a heat resistant substrate layer (A1), a soft substrate layer (A2) and an auxiliary substrate layer (A3) in this order. That is, the auxiliary base layer (A3) is arranged between the soft base layer (A2) and the adhesive layer (B).

The thickness of the auxiliary base material layer (A3) is preferably 2 μm to 60 μm, more preferably 3 μm to 60 μm, even more preferably 5 μm to 55 μm, particularly preferably 5 μm to 50 μm. If the thickness of the auxiliary base material layer (A3) is within the above range, the effect of the present invention can be exhibited more effectively.

The error in the thickness of the auxiliary base layer (A3) from the thickness of the heat-resistant base layer (A1) is preferably ±50% or less, more preferably ±30% or less, and still 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 heat-resistant base layer (A1) is within the above range, the laminate structure of the base layers in the surface protection film in the embodiment of the present invention is vertically symmetrical. Since it becomes close, curling of the surface protection film can be suppressed. In particular, when the surface protection 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.

The auxiliary base material layer (A3) may consist of only one layer, or may consist of two or more layers. When the auxiliary base material layer (A3) has two or more layers, each layer may have the same composition, or at least one layer may be a different layer.

The auxiliary base material layer (A3) is preferably 1 to 5 layers, more preferably 1 to 3 layers, even more preferably 1 to 2 layers, particularly preferably 1 layer.

The auxiliary base material layer (A3) may contain any suitable resin as long as the effects of the present invention are not impaired. The main component resin contained in the auxiliary base layer (A3) is preferably the same as the main component resin contained in the heat-resistant base layer (A1). If the main component resin contained in the auxiliary base layer (A3) is the same as the main component resin contained in the heat-resistant base layer (A1), the composition of the base layer in the surface protective film in the embodiment of the present invention Since the distribution is nearly symmetrical in the vertical direction, curling of the surface protection film can be suppressed. In particular, when the surface protection 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.

The auxiliary base material layer (A3) preferably contains a propylene-based resin as a main component. When the auxiliary base layer (A3) contains a propylene-based resin as a main component, the effects of the present invention can be further exhibited. In particular, when a propylene-based resin is employed as the main component resin contained in the heat-resistant substrate layer (A1), the auxiliary substrate layer (A3) contains the propylene-based resin as a main component, thereby reducing the heat-resistant substrate layer (A1 ), the composition distribution of the substrate layer in the surface protective film in the embodiment of the present invention is nearly symmetrical, and the surface protective film in the embodiment of the present invention can be the same as the resin substrate When used for heat press, curling due to heat history can be effectively suppressed.

The content of the propylene-based resin in the auxiliary base layer (A3) is preferably 50% to 100% by weight, more preferably 70% to 100% by weight, still more preferably 90% to 100% by weight. % by weight, particularly preferably 95% to 100% by weight, most preferably substantially 100% by weight. If the content of the propylene-based resin in the auxiliary base material layer (A3) is within the above range, the effects of the present invention can be exhibited more effectively. In particular, when a propylene-based resin is employed as the main component resin contained in the heat-resistant substrate layer (A1), the auxiliary substrate layer (A3) contains the propylene-based resin as a main component, thereby reducing the heat-resistant substrate layer (A1 ), the composition distribution of the substrate layer in the surface protective film in the embodiment of the present invention is nearly symmetrical, and the surface protective film in the embodiment of the present invention can be the same as the resin substrate When used for heat press, curling due to heat history can be effectively suppressed.

As the propylene-based resin, any appropriate propylene-based resin can be adopted as long as the effects of the present invention are not impaired. Such propylene-based resins include, for example, at least one selected from random polypropylene, block polypropylene, homopolypropylene, and copolymers of propylene and other monomers.

The propylene-based resin may be used alone or in a blend of two or more.

Homopolypropylene typically includes isotactic homopolypropylene, atactic homopolypropylene, syndiotactic homopolypropylene and the like.

As the copolymer of propylene and other monomers, any appropriate copolymer can be adopted as long as the effects of the present invention are not impaired. Examples of such copolymers of propylene and other monomers include propylene/ethylene copolymers, propylene/ethylene/1-butene copolymers, and propylene/α-olefins having 5 to 12 carbon atoms. A copolymer etc. are mentioned.

The propylene-based resin may be a metallocene-based propylene-based resin obtained using a metallocene catalyst. Such metallocene-based propylene-based resins include, for example, at least one selected from metallocene-based random polypropylene, metallocene-based block polypropylene, metallocene-based homopolypropylene, and copolymers of metallocene-based propylene and other monomers. is mentioned.

A commercially available product may be used as the propylene-based resin.

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

The auxiliary base material layer (A3) may contain any appropriate additive as necessary. Additives that may be contained in the auxiliary base material layer (A3) include, for example, mold release agents, ultraviolet absorbers, heat stabilizers, fillers, lubricants, colorants (dyes, etc.), antioxidants, and anti-staining agents. agents, antiblocking agents, foaming agents, polyethyleneimines, and the like. These may be one kind or two or more kinds. The content of the additive in the auxiliary base material layer (A3) is preferably 10% by weight or less, more preferably 7% by weight or less, still more preferably 5% by weight or less, and particularly preferably 2% by weight. % or less, and most preferably 1 wt % or less.

Examples of release agents include fatty acid amide-based release agents, silicone-based release agents, fluorine-based release agents, and long-chain alkyl-based release agents. From the standpoint of forming a release layer with an excellent balance between releasability and contamination resistance due to bleeding out, fatty acid amide release agents are preferred, and saturated fatty acid bisamides are more preferred. Any appropriate content can be adopted as the content of the release agent. Typically, it is preferably 0.01% by weight to 5% by weight with respect to the resin component (preferably propylene-based resin) in the auxiliary base material layer (A3).

Examples of ultraviolet absorbers include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. Any appropriate content can be adopted as the content of the ultraviolet absorber as long as it does not bleed out during molding. Typically, it is preferably 0.01% by weight to 5% by weight with respect to the resin component (preferably propylene-based resin) in the auxiliary base material layer (A3).

Examples of heat-resistant stabilizers include hindered amine-based compounds, phosphorus-based compounds, and cyanoacrylate-based compounds. Any appropriate content can be adopted as the content of the heat stabilizer as long as it does not bleed out during molding. Typically, it is preferably 0.01% by weight to 5% by weight with respect to the resin component (preferably propylene-based resin) in the auxiliary base material layer (A3).

Examples of fillers 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 between 0.1 μm and 20 μm. Any appropriate content can be adopted as the content of the filler. Typically, it is preferably 1% by weight to 200% by weight with respect to the resin component (preferably propylene-based resin) in the auxiliary base layer (A3).

<<1-2. Adhesive layer (B)>>
The thickness of the adhesive layer (B) is preferably 5 μm to 50 μm, more preferably 5 μm to 40 μm, still more preferably 5 μm to 30 μm, and particularly preferably 5 μm to 20 μm. If the thickness of the pressure-sensitive adhesive layer (B) is within the above range, the effects of the present invention can be exhibited more effectively. If the thickness of the pressure-sensitive adhesive layer (B) is too thin, there is a possibility that a sufficient pressure-sensitive adhesive effect cannot be exhibited. If the pressure-sensitive adhesive layer (B) is too thick, the surface protective film will be too thick, which may make it difficult to follow the three-dimensional curved shape of the mold. .

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) is two or more layers, each layer may have the same composition, or at least one layer may be a different layer.

The pressure-sensitive adhesive layer (B) may employ a pressure-sensitive adhesive layer formed from any appropriate pressure-sensitive adhesive. As such an adhesive, for example, a thermoplastic resin as a main component (preferably 50% to 100% by weight, more preferably 70% to 100% by weight, more preferably 80% to 100% by weight) % 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 of only one type, or may be of two or more types.

Any appropriate thermoplastic resin can be adopted as the thermoplastic resin. Examples of such thermoplastic resins include at least one selected from the group consisting of styrene resins, olefin resins, aromatic group-containing olefin/diene copolymers, ester resins, acrylic resins, and rubber resins. is mentioned. Among these thermoplastic resins, at least one selected from the group consisting of styrene-based resins and olefin-based resins is preferred.

Styrene-based resins preferably include styrene-based elastomers.

The olefinic resin preferably includes an olefinic elastomer.

By using at least one selected from the group consisting of styrene-based resins and olefin-based resins as the thermoplastic resin, good adhesive strength, good adhesive strength after long-term storage, low staining after peeling, etc. are balanced. can express well.

Preferable examples of the styrene-based elastomer include hydrogenated styrene-butadiene rubber (HSBR), styrene-based block copolymers, and hydrogenated products thereof.

Hydrogenated styrene-butadiene rubber (HSBR) includes, for example, DYNARON 1320P, 1321P, 2324P manufactured by JSR.

Styrene-based block copolymers include, for example, styrene-butadiene-styrene copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), and other styrene-based ABA block copolymers (triblock copolymers ); styrene-based ABAB type block copolymers (tetrablock copolymers) such as styrene-butadiene-styrene-butadiene copolymer (SBSB) and styrene-isoprene-styrene-isoprene copolymer (SISI); styrene-butadiene Styrene-based ABABA-type block copolymers (pentablock copolymers) such as styrene-butadiene-styrene copolymer (SBSBS), styrene-isoprene-styrene-isoprene-styrene copolymer (SISIS); styrenic block copolymers having repeating units; and the like.

Examples of hydrogenated styrene block copolymers include styrene/ethylene-butylene copolymer/styrene copolymer (SEBS), styrene/ethylene-propylene copolymer/styrene copolymer (SEPS), styrene - Ethylene-butylene copolymer - Copolymer of styrene-ethylene-butylene copolymer (SEBSEB);

Styrene-ethylene-butylene copolymer-styrene copolymer (SEBS) is particularly preferred as the styrene-based thermoplastic elastomer. By adopting styrene/ethylene-butylene copolymer/styrene copolymer (SEBS) as the styrene elastomer, good adhesive strength, good adhesive strength after long-term storage, low staining after peeling, etc. are well balanced. can be expressed.

Examples of styrene/ethylene-butylene copolymer/styrene copolymer (SEBS) include DYNARON 8601P and 9901P manufactured by JSR.

Only one type of styrene-based elastomer may be used, or two or more types may be used.

The styrene content in the styrene-based elastomer (styrene block content in the case of a styrene-based block copolymer) is preferably 1 wt% to 40 wt%, more preferably 5 wt% to 40 wt%, still more preferably 7% to 30% by weight, more preferably 9% to 20% by weight, particularly preferably 9% to 15% by weight, and most preferably 9% to 13% by weight. If the styrene content is too low, there is a risk that adhesive deposits will tend to occur due to insufficient cohesive strength of the pressure-sensitive adhesive layer. If the styrene content is too high, the pressure-sensitive adhesive layer will become hard, and it may not be possible to obtain good adhesion to rough surfaces. When the styrene block content is within the above range, good adhesive strength, good adhesive strength after long-term storage, low staining property after peeling, and the like can be exhibited in a well-balanced manner.

Examples of styrene-based elastomers include hydrogenated styrene-based block copolymers ( SEBS, SEBSEB, SEBSEBS, etc.) are preferred. By adopting such a styrene-based elastomer, good adhesive strength, good adhesive strength after long-term storage, low staining property after peeling, and the like can be exhibited in a well-balanced manner.

The styrene elastomer is a hydrogenated styrene block copolymer (SEBS , SEBSEB, SEBSEBS, etc.), the ratio of the butylene structure in the ethylene-butylene copolymer block is preferably 60% by weight or more, more preferably 70% by weight or more, and still more preferably 75% by weight. That's it. When the ratio of the butylene structure in the ethylene-butylene copolymer block is within the above range, good adhesive strength, good adhesive strength after storage over time, low staining property after peeling, etc. can be exhibited in a well-balanced manner. The ratio of the butylene structure in the ethylene-butylene copolymer block is preferably 90% by weight or less.

The base polymer may contain other styrenic elastomers for the purpose of adjusting adhesiveness, etc., within the scope not impairing the object of the present invention.

Examples of other styrene-based elastomers include styrene-based block copolymers other than those described above; styrene/butadiene copolymer (SB), styrene/isoprene copolymer (SI), and styrene/ethylene-butylene copolymer. AB type block polymers such as (SEB) and styrene/ethylene-propylene copolymer (SEP); styrene-based random copolymers such as styrene/butadiene rubber (SBR); styrene/ethylene-butylene copolymers ABC-type styrene/olefin crystal block polymers such as copolymers of olefin crystals (SEBC); hydrogenated products thereof; and the like.

The olefinic elastomer preferably includes an amorphous polyolefinic elastomer.

Examples of amorphous polyolefin-based elastomers include ethylene propylene rubber, elastomers composed of ethylene and α-olefin, and amorphous polypropylene-based resins exhibiting stickiness (such as atactic polypropylene). Amorphous polypropylene resins are preferred. Any appropriate amorphous polypropylene-based resin can be adopted as the amorphous polypropylene-based resin as long as it has rubber elasticity in the operating temperature range.

Here, the amorphous polyolefin-based elastomer has amorphous properties without a crystal structure. Examples of methods for confirming the presence of amorphous properties include a solubility test in n-heptane. Specifically, the amorphous polyolefin elastomer is dissolved in n-heptane at a concentration of 10% by weight, and the solubility is measured. Those having 90% or more are defined as having amorphous properties.

Examples of amorphous polypropylene resins include propylene-α-olefin copolymers and propylene-ethylene-α-olefin copolymers.

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

Amorphous polypropylene-based resins preferably include amorphous propylene-(1-butene) copolymers. Amorphous propylene-(1-butene) copolymers can be obtained by copolymerizing propylene and 1-butene, preferably using a metallocene catalyst. Amorphous propylene-(1-butene) copolymers obtained by copolymerization using metallocene catalysts exhibit a narrow molecular weight distribution (eg, 2 or less). By using an amorphous propylene-(1-butene) copolymer exhibiting such a narrow molecular weight distribution, bleeding of low molecular weight components can be prevented.

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 further It is preferably 90 mol % to 99 mol %. If the content of the propylene-derived structural unit 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. The effect of the present invention can be exhibited more effectively.

The content of 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%. . If the content of the 1-butene-derived structural unit in the amorphous propylene-(1-butene) copolymer is within such a range, it is possible to obtain a pressure-sensitive adhesive layer having an excellent balance between toughness and flexibility. Therefore, the effects of the present invention can be exhibited more effectively.

Any appropriate copolymer structure can be adopted as the copolymer structure of the amorphous propylene-(1-butene) copolymer. Examples of such a copolymer structure include block copolymers and random copolymers.

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, still more preferably 200,000 to 300,000. If 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 further enhanced. It can be expressed more effectively.

When the pressure-sensitive adhesive layer (B) contains an amorphous propylene-(1-butene) copolymer, the pressure-sensitive adhesive layer further contains a crystalline polypropylene resin in order to adjust the adhesive strength of the pressure-sensitive adhesive layer. Also good. By containing the crystalline polypropylene-based resin in the pressure-sensitive adhesive layer, it is possible to moderately reduce the adhesive strength of the pressure-sensitive adhesive layer and increase the storage elastic modulus. When the pressure-sensitive adhesive layer further contains a crystalline polypropylene-based resin, the content of the crystalline polypropylene-based resin in the pressure-sensitive adhesive layer is set to any appropriate content according to the desired adhesive strength and storage elastic modulus. obtain. The content of such a crystalline polypropylene resin is preferably from 0% by weight to the total weight of the amorphous propylene-(1-butene) copolymer and the crystalline polypropylene resin. 50% by weight, more preferably 0% to 40% by weight, and even more preferably 0% to 30% by weight.

As the adhesive layer (B), for example, an acrylic resin as a main component (preferably 50 wt% to 100 wt%, more preferably 70 wt% to 100 wt%, still more preferably 80 wt% to 100% by weight, particularly preferably 90% to 100% by weight, and most preferably 95% to 100% by weight). Only one kind of acrylic resin may be contained in the base polymer, or two or more kinds thereof may be used.

As the acrylic resin, any appropriate acrylic resin can be adopted as long as the effects of the present invention are not impaired. Such an acrylic resin can preferably be obtained by polymerization of the monomer component (m).

Any appropriate monomer component can be adopted as the monomer component (m) as long as the effect of the present invention is not impaired.

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

Specific examples of the alkyl (meth)acrylate having an alkyl group having 4 to 18 carbon atoms at the ester end include n-butyl (meth)acrylate, n-pentyl (meth)acrylate, and n-hexyl (meth)acrylate. Acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate , n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-heptadecyl (meth)acrylate, n-octadecyl (meth)acrylate, etc. , Alkyl (meth)acrylates having a linear alkyl group having 4 to 18 carbon atoms at the ester end; t-butyl (meth)acrylate, isobutyl (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-propyl Heptyl (meth)acrylate, isoundecyl (meth)acrylate, isododecyl (meth)acrylate, isotridecyl (meth)acrylate, isomystyryl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate Alkyl (meth)acrylates having a branched chain alkyl group having 4 to 18 carbon atoms at the ester end, such as acrylates and isostearyl (meth)acrylates; Among these alkyl (meth)acrylates having an alkyl group having 4 to 18 carbon atoms at the ester end, alkyl (meth)acrylates having a linear alkyl group having 4 to 12 carbon atoms at the ester end are preferred, and Alkyl (meth)acrylates having ∼8 linear alkyl groups at the ester end are more preferred, and n-butyl (meth)acrylate is particularly preferred.

The content of the alkyl (meth)acrylate having an alkyl group having 4 to 18 carbon atoms at the ester end in the monomer component (m) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 99% by weight. .5% by weight, more preferably 90% to 99% by weight, particularly preferably 91% to 98% by weight, and most preferably 92% to 97% by weight.

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

The monomer component (m) may contain other monomers. Only one kind of such other monomers may be used, or two or more kinds thereof may be used.

The content of other monomers in the total amount of the monomer component (m) is preferably 0 wt% to 10 wt%, more preferably 0 wt% to 8 wt%, still more preferably 0 wt% to 6 wt%. %, particularly preferably 0 wt % to 4 wt %, most preferably 0 wt % to 2 wt %.

Other monomers include, for example, alicyclic structure-containing acrylic monomers, alkyl (meth)acrylates having an alkyl group having 1 to 3 carbon atoms at the ester end, hydroxyl group-containing monomers, and carboxyl groups other than (meth)acrylic acid. group-containing monomers, 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, Examples include functional monomers.

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 6-24, still more preferably 6-18, and particularly preferably 6-12. 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, dicyclopentanyl (meth)acrylate and the like.

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

Specific examples of hydroxyl group-containing monomers include 2-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6 - hydroxyalkyl (meth)acrylates such as hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate; Hydroxyalkylcycloalkane (meth)acrylates such as xyl)methyl (meth)acrylate; Other hydroxyl group-containing monomers such as hydroxyethyl (meth)acrylamide, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether ; and the like. Among these hydroxyl group-containing monomers, hydroxyalkyl (meth)acrylates are preferable, and hydroxyalkyl (meth)acrylates having a hydroxyalkyl group having 2 to 6 carbon atoms are more preferable, and 2-hydroxyethyl (meth)acrylate, 4-hydroxy Butyl (meth)acrylate is more preferred.

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. is mentioned.

Specific examples of nitrogen-based cyclic structure-containing monomers include lactam-based vinyl monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and methylvinylpyrrolidone; vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinyl-based monomers having a nitrogen-containing heterocyclic ring such as vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine; For example, N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine, etc.);

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

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. mentioned.

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

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, N,N-hydroxyethylacrylamide and the like. .

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

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

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, 10-acryloyloxydecyltriethoxysilane, etc. is mentioned.

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) Acrylates, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth) Ester compounds of polyhydric alcohols such as acrylates, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate and (meth)acrylic acid; ) acrylate; vinyl (meth)acrylate; divinylbenzene; epoxy acrylate; polyester acrylate; urethane acrylate;

The acrylic resin is obtained by polymerizing the monomer component (m).

As a method for producing the acrylic resin, any suitable production method can be adopted as long as the effects of the present invention are not impaired. Examples of such a production method include solution polymerization, active energy ray polymerization such as UV polymerization, and various radical polymerizations such as bulk polymerization and emulsion polymerization. As polymerization conditions, any suitable polymerization conditions can be adopted as long as the effects of the present invention are not impaired.

As the polymerized structure of the obtained acrylic resin, any appropriate polymerized structure can be adopted as long as the effects of the present invention are not impaired. Examples of such polymer structures include random copolymers, block copolymers, and graft copolymers.

Any appropriate additive can be employed as additives such as a polymerization initiator, a chain transfer agent, and an emulsifier used for radical polymerization, as long as the effects of the present invention are not impaired.

Examples of polymerization solvents that can be used for solution polymerization include ethyl acetate and toluene. The polymerization solvent may be of only one type, or may be of two or more types.

The solution polymerization is carried out, for example, under a stream of inert gas such as nitrogen, adding a polymerization initiator, and generally at a temperature of about 50° C. to 70° C. under reaction conditions of about 5 hours to 30 hours.

As the polymerization initiator that can be used for solution polymerization, any appropriate thermal polymerization initiator can be adopted as long as the effects of the present invention are not impaired. Only one polymerization initiator may be used, or two or more polymerization initiators may be used. Such polymerization initiators include, for example, 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′-dimethyleneisobutyramidine), 2, Azo initiators such as 2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (VA-057, manufactured by Wako Pure Chemical Industries, Ltd.); potassium persulfate, ammonium persulfate, etc. persulfate of, di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate , di(4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, hydrogen peroxide, etc. peroxide-based initiators; redox-based initiators that combine peroxides and reducing agents, such as combinations of persulfate and sodium hydrogen sulfite, and combinations of peroxides and sodium ascorbate;

The amount of the polymerization initiator to be used is preferably 1 part by weight or less, more preferably 0.1 part by weight, based on 100 parts by weight of the total amount of the monomer component (m), in order to allow the polymerization reaction to proceed effectively. 005 to 1 part by weight, more preferably 0.01 to 0.7 part by weight, and particularly preferably 0.02 to 0.5 part by weight.

As the chain transfer agent, any suitable chain transfer agent can be adopted as long as the effects of the present invention are not impaired. Only one type of chain transfer agent may be used, or two or more types may be used. Examples of such chain transfer agents include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol and the like.

The amount of the chain transfer agent to be used is preferably 0.1 parts by weight or less with respect to 100 parts by weight of the total amount of the monomer component (m) in order to allow the polymerization reaction to proceed effectively.

As the emulsifier, any appropriate emulsifier can be adopted as long as the effects of the present invention are not impaired. Only one emulsifier may be used, or two or more emulsifiers may be used. 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 alkylphenyl ether sulfate; nonionic emulsifiers such as oxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene-polyoxypropylene block polymers;

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

When carrying out UV polymerization, preferably a photoinitiator is used.

As the photopolymerization initiator, any appropriate photopolymerization initiator can be employed as long as the effects of the present invention are not impaired. Only one type of photopolymerization initiator may be used, or two or more types may be used. 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, and photoactive oxime-based photopolymerization initiators. Photoinitiators, benzoin photoinitiators, benzyl photoinitiators, benzophenone photoinitiators, ketal photoinitiators, thioxanthone photoinitiators, acylphosphine oxide photoinitiators, etc. is mentioned.

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-diphenylethane- 1-one (commercially available, for example, trade name "Irgacure 651", manufactured by BASF), anisole methyl ether, and the like.

Specific examples of the acetophenone-based photopolymerization initiator include, for example, 1-hydroxycyclohexylphenyl ketone (commercially available products such as 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 (commercially available, for example, trade name "Irgacure 2959 ”, manufactured by BASF), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (commercially available products include, for example, trade name “Darocure 1173”, manufactured by BASF), methoxyacetophenone, and the like. .

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

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

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

Specific examples of benzoin-based photopolymerization initiators include benzoin.

Specific examples of benzyl-based photopolymerization initiators include benzyl.

Specific examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone.

Specific examples of ketal-based photopolymerization initiators include benzyl dimethyl ketal.

Specific examples of thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, and 2,4-diethyl thioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, and the like.

Specific examples of acylphosphine-based photopolymerization initiators include bis(2,6-dimethoxybenzoyl)phenylphosphine oxide and 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, bis(2,6-dimethoxybenzoyl)-t-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-1-yl)phosphine oxide, bis(2,6-di butoxybenzoyl)(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-trimethyl Benzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)isobutylphosphine oxide, 2,6-dimethoxybenzoyl-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 and the like.

The amount of the photopolymerization initiator used is preferably 5 parts by weight or less, more preferably 0.01 parts by weight, based on 100 parts by weight of the total amount of the monomer component (m), from the viewpoint of expressing good polymerizability. parts by weight to 5 parts by weight, more preferably 0.05 parts by weight to 3 parts by weight, particularly preferably 0.05 parts by weight to 1.5 parts by weight, most preferably 0.1 parts by weight to 1 part by weight.

When carrying out UV polymerization, preferably polyfunctional (meth)acrylates are used.

Any appropriate polyfunctional (meth)acrylate can be employed as the polyfunctional (meth)acrylate as long as the effects of the present invention are not impaired. Only one kind of polyfunctional (meth)acrylate may be used, or two or more kinds thereof may be used. Specific examples of such polyfunctional (meth)acrylates include, for example, (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- Polyhydric alcohol such as hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate and (meth)acrylic acid vinyl (meth)acrylate; divinylbenzene; epoxy acrylate; polyester acrylate; urethane acrylate; butyl di(meth)acrylate; hexyl di(meth)acrylate;

The amount of the polyfunctional (meth)acrylate used is preferably 5 parts by weight or less, more preferably 0 parts by weight, based on 100 parts by weight of the total amount of the monomer component (m), from the viewpoint of expressing good crosslinkability. 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, particularly preferably 0.05 to 1.5 parts by weight, most preferably 0.1 part by weight part to 1 part by weight.

Any appropriate UV polymerization method can be adopted as long as the effects of the present invention are not impaired. As such a UV polymerization method, for example, the monomer component (m) is blended with a photopolymerization initiator and, if necessary, a polyfunctional (meth)acrylate, and irradiated with ultraviolet rays.

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, still more preferably 500,000 to 1,500,000, and particularly preferably 500,000 to 1,000,000. be. In addition, a weight average molecular weight is measured by a gel permeation chromatography (GPC), and says the value calculated by polystyrene conversion. In addition, it may be difficult to measure the weight average molecular weight of the acrylic resin obtained by active energy ray polymerization.

The pressure-sensitive adhesive layer (B) may contain any appropriate other component as needed. Other components include, for example, tackifiers; softeners; anti-aging agents; polyolefin resins; silicone resins; liquid acrylic copolymers; light stabilizer; ultraviolet absorber; heat stabilizer; filler or pigment such as calcium oxide, magnesium oxide, silica, zinc oxide, titanium oxide; cross-linking agent; surface lubricant, leveling agent; Antioxidant; Corrosion inhibitor; Polymerization inhibitor; Silane coupling agent; Conductive agent; The type, number and amount of other components that can be contained in the pressure-sensitive adhesive layer can be appropriately set according to the purpose.

The surface of the adhesive layer (B) requires surface treatment, such as corona discharge treatment, ultraviolet irradiation treatment, flame treatment, plasma treatment, sputter etching treatment, etc., for the purpose of controlling adhesiveness and attaching workability. It can also be applied according to

The adhesive layer (B) preferably contains a tackifier. By including a tackifier in the pressure-sensitive adhesive layer (B), the pressure-sensitive adhesive strength can be improved. However, the amount of the tackifier is appropriately determined according to the adherend to which the surface protection sheet is applied, in order to avoid the problem of adhesive deposits 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 still more preferably 20% by weight or less, relative to the base polymer of the adhesive layer (B).

Examples of tackifiers include aliphatic copolymers, aromatic copolymers, petroleum resins such as aliphatic/aromatic copolymers and alicyclic copolymers, and coumarone-indene resins. , terpene-based resins, terpene-phenolic resins, rosin-based resins such as polymerized rosin, (alkyl)phenol-based resins, xylene-based resins, hydrogenated products of these, etc., which are generally used for adhesives You can use anything without any restrictions. Only one type of tackifier may be used, or two or more types may be used. Among these tackifiers, hydrogenated tackifiers are preferable from the viewpoint of peelability and weather resistance. As the tackifier, one commercially available as a blend with an olefin resin can also be used.

The softening point of the tackifier is preferably 100° C. or higher, more preferably 105° C. or higher, still 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.

Addition of a softening agent is effective in improving adhesive strength. Examples of softening agents 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. Specifically, hydrogenated polybutadiene diol, hydrogenated polybutadiene monool, hydrogenated polyisoprene diol, water Added polyisoprene monool and the like can be mentioned. In particular, hydrogenated products of diene polymers such as hydrogenated polybutadiene and hydrogenated polyisoprene, olefinic softeners, and the like are preferable for the purpose of suppressing the improvement of adhesiveness to adherends. As such a softening agent, specifically, trade name "Kuraprene LIR-200" manufactured by Kuraray Co., Ltd. is available. Only one of these softeners may be used, or two or more thereof may be used.

The molecular weight of the softening agent can be appropriately set to any appropriate amount. The number average molecular weight of the softening agent is preferably 5,000 to 100,000, more preferably 10,000 to 50,000, because the effect of improving adhesive strength tends to be poor as the molecular weight increases.

When a softening agent is used, the amount to be added can be appropriately set to any appropriate amount. ) is preferably 100% by weight or less, more preferably 60% by weight or less, and still more preferably 40% by weight or less, relative to the base polymer. When the adherend is a metal plate, it is preferable not to add a softening agent in forming the pressure-sensitive adhesive layer (B).

A polyolefin resin may be added to the pressure-sensitive adhesive layer (B) for the purpose of suppressing an increase in adhesive strength. Only one kind of polyolefin resin may be used, or two or more kinds thereof may be used. The blending amount of the polyolefin resin is preferably 50% by weight or less, more preferably 30% by weight or less, and still more preferably 20% by weight or less based on the base polymer of the adhesive layer.

<<<2. Method for producing surface protective film>>>>
Surface protective films in embodiments of the present invention can be produced by any appropriate method. As such a manufacturing method, for example,
(1) A method of applying a solution or hot melt of the material for forming the pressure-sensitive adhesive layer (B) onto the substrate layer (A),
(2) A method of transferring the pressure-sensitive adhesive layer (B) formed by applying a solution or hot melt of the material for forming the pressure-sensitive adhesive layer (B) onto the separator onto the substrate layer (A);
(3) A method of extruding and coating the forming material of the pressure-sensitive adhesive layer (B) onto the substrate layer (A),
(4) A method of extruding the substrate layer (A) and the pressure-sensitive adhesive layer (B) in two layers or multiple layers,
(5) A method of laminating a single layer of the adhesive layer (B) on the base layer (A) or a method of laminating two layers of the adhesive layer (B) together with the laminate layer,
(6) A method of two-layer or multi-layer lamination of the adhesive layer (B) and a substrate layer-forming material such as a film or laminate layer,
It can be performed according to any appropriate manufacturing method such as.

Examples of coating methods 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.

A base material layer (A) can be manufactured by arbitrary appropriate methods. Such a production method includes, for example, a method of extruding the material of each layer constituting the substrate layer (A). For example, when the substrate layer (A) is a three-layered structure of heat-resistant substrate layer (A1)/soft substrate layer (A2)/auxiliary substrate layer (A3), extrusion of three types and three layers is performed. mentioned. In the case of three layers of heat-resistant substrate layer (A1) / soft substrate layer (A2) / auxiliary substrate layer (A3), the material of the heat-resistant substrate layer (A1) and the auxiliary substrate layer (A3 ) are made of the same material, a two-kind, three-layer extrusion may be used.

<<<3. Application≫≫
The surface protective film of the present invention can be used for any suitable purpose. In view of the effects of the present invention, the surface protection film of the present invention is preferably used for manufacturing members provided in mobile devices, and more preferably used for the surface of the resin plate when the resin substrate is heat-pressed. Used for protection. In this case, the heating temperature for hot pressing is preferably 50°C to 180°C, more preferably 120°C to 170°C.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. The tests and evaluation methods used in Examples and the like are as follows. "Parts" means "parts by weight" unless otherwise specified, and "%" means "% by weight" unless otherwise specified.

<Maximum peak temperature by DSC measurement>
The melting points of the surface protective films of Examples and Comparative Examples were measured using a temperature-modulated DSC (trade name “Q-2000”, manufactured by TA Instruments). About 1 to 2 mg of sample was collected and weighed in an aluminum open cell as a test piece, and the reversing heat flow (specific heat component) behavior of the test piece was obtained at a temperature increase rate of 10°C/min under a nitrogen atmosphere of 50 ml/min. . With reference to JIS-K-7121, a straight line equidistant in the vertical axis direction from the straight line extending the baseline on the low temperature side and the baseline on the high temperature side of the obtained Reversing Heat Flow, and a stepwise change accompanying melting The temperature at the point of intersection with the partial curve was taken as the "peak temperature (°C)" of each sample. When two or more peaks appeared, the higher peak temperature was taken as the "maximum peak temperature (°C)". When the maximum peak temperature by DSC measurement is high, it means that the heat resistance of the surface protection film (especially the heat-resistant substrate layer (A1)) is high.

<High temperature storage modulus>
For the surface protection films of Examples and Comparative Examples, the tensile storage modulus (MPa ) was measured. In the measurement, the size of the surface protection film, which is the object to be measured, is 10 mm in width × 40 mm in length, the initial distance between the chucks for holding the sample piece is 10 mm, the measurement mode is the tension mode, and the measurement temperature range is 25 ° C. The temperature was 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 representing the hardness of the surface protective film itself. more likely to occur.

<Mold adhesion prevention>
After cutting a test piece with a size of 120 mm in width and 120 mm in length from the surface protective film, PMMA plate (trade name "Acrylite", thickness 2 mm × width 100 mm × length 100 mm, manufactured by Mitsubishi Rayon Co., Ltd.) Then, the test piece was press-bonded to the pressure-sensitive adhesive layer by one reciprocation of a 2-kg hand roller. Then, the surplus portion (the portion not attached to the PMMA plate) was cut off with a utility knife, and the test piece was left for 30 minutes in an environment of 23° C. and 50% RH. 360 polished SUS304 plate (thickness 1.5 mm x width 100 mm x length 100 mm) and SUS430BA plate (thickness 1.5 mm x width 100 mm x length 100 mm) sandwiched from the top, vacuum pressure forming machine ( using a product name "Vacuum Compressed Air Forming Machine NGF-0406-S" manufactured by Fuse Vacuum Co., Ltd.), left on the lower press plate at a temperature of 120 ° C. for 1 minute, and then pressed with the upper press plate at a temperature of 30 ° C. Vacuum pressure molding was performed at a vacuum pressure of 1.5 MPa, a vacuum time of 1 second, and a molding time of 120 seconds. After leaving the test piece in an environment of 23°C and 50% RH for 1 minute, no adhesion was observed between the SUS304 plate and the test piece, and the SUS304 plate and test piece were separated without peeling off the tape from the PMMA plate. The result was evaluated as ◯, and the test piece peeled off from the PMMA plate when the SUS304 plate was separated was evaluated as x. The mold adhesion prevention property is to suppress adhesion (fusion) of the surface protective film to the mold after hot pressing in the process of hot-pressing the resin substrate to which the surface protective film is adhered with the mold. It is an indicator of whether or not it is possible.

<Anti-citron skin resistance>
After performing vacuum and pressure molding in the same manner as in the measurement method for <Mold adhesion prevention property>, the test piece was peeled off from the PMMA plate, and sandpaper No. 2 was applied to the peeled surface. When transfer roughness on the surface of the SUS304 plate polished by 360 was visually confirmed, it was evaluated as x, and when it was not confirmed, it was evaluated as ◯.

<Molding conditions>
In Examples and Comparative Examples, substrates were molded using a three-kind, three-layer (A layer/B layer/C layer) extrusion T-die molding machine. The extrusion temperature was carried out under the following conditions.
Layer A: 200°C
Layer B: 200°C
Layer C: 200°C
Die temperature: 200°C
After co-extrusion molding from a T-die and integration, the resulting base material was sufficiently solidified, it was wound into a roll shape to obtain a roll body.

[Example 1]
As a base resin, a propylene-based resin (manufactured by Japan Polypropylene Corporation, trade name: Novatec PP SA06GA, a propylene homopolymer obtained by polymerization with a Ziegler catalyst) was placed in the A layer of the extruder, and an ethylene/vinyl acetate copolymer (EVA ) (manufactured by DuPont Mitsui Polychemical Co., Ltd., trade name: Evaflex EV550) is put into the B layer of the extruder, and PP (manufactured by Japan Polypro Co., Ltd., trade name: Novatec PP SA06GA) is put into the C layer of the extruder, and A Layer/B layer/C layer=25 μm/50 μm/25 μm, a laminate having a total thickness of 100 μm was extruded into a film to obtain a substrate layer (1).
As an adhesive, styrene-ethylene-butylene-styrene block copolymer (SEBS) (manufactured by Kraton, trade name: Kraton G1657): 100 parts, and a tackifier (manufactured by Arakawa Chemical Industries, Ltd.: Alcon P-100): A mixture of 40 parts was prepared, dissolved in a diluent solvent (toluene), applied to the surface of layer C of the substrate layer (1), and dried to form a pressure-sensitive adhesive layer having a thickness of 15 μm.
As described above, a surface protection film (1) was obtained. Table 1 shows the results.

[Example 2]
A surface protective film (2) was obtained in the same manner as in Example 1, except that the layer A/layer B/layer C was 8 µm/84 µm/8 µm and the total thickness was 100 µm. Table 1 shows the results.

[Example 3]
As a base resin, a propylene resin (manufactured by Japan Polypropylene Co., Ltd., trade name: Wintec WFW4, propylene/ethylene random polymer obtained by polymerization with a metallocene catalyst) was used for the A layer and the C layer of the extruder. A surface protective film (3) was obtained in the same manner as in Example 1 except for the above. Table 1 shows the results.

[Example 4]
Surface protection was performed in the same manner as in Example 1 except that ethylene / vinyl acetate copolymer (EVA) (Mitsui DuPont Polychemicals, trade name: EVAFLEX EV250) was used as the base resin for the B layer of the extruder. A film (4) was obtained. Table 1 shows the results.

[Example 5]
A surface protective film (5) was prepared in the same manner as in Example 1, except that low-density polyethylene (LDPE) (manufactured by Nippon Polyethylene Co., Ltd., trade name: Novatec LDLC720) was used as the base resin for the B layer of the extruder. Obtained. Table 1 shows the results.

[Example 6]
Surface protection was performed in the same manner as in Example 1 except that ethylene / vinyl acetate copolymer (EVA) (Mitsui DuPont Polychemicals, trade name: EVAFLEX EV250) was used as the base resin for the C layer of the extruder. A film (6) was obtained. Table 1 shows the results.

[Example 7]
A surface protective film (7) was prepared in the same manner as in Example 1 except that low-density polyethylene (LDPE) (manufactured by Japan Polyethylene Co., Ltd., trade name: Novatec LDLC720) was used as the base resin for the C layer of the extruder. Obtained. Table 1 shows the results.

[Example 8]
As the base resin, low-density polyethylene (LDPE) (manufactured by Nippon Polyethylene Co., Ltd., product name: Novatec LDLC720) is used as the B layer of the extruder, and ethylene / vinyl acetate copolymer (EVA) (manufactured by Mitsui DuPont Polychemical Co., Ltd., product A surface protective film (8) was obtained in the same manner as in Example 1, except that the C layer of the extruder was used (name: Evaflex EV550). Table 1 shows the results.

[Example 9]
A surface protective film was prepared in the same manner as in Example 1 except that low-density polyethylene (LDPE) (manufactured by Japan Polyethylene Co., Ltd., trade name: Novatec LDLC720) was used as the base resin for the B and C layers of the extruder. (9) was obtained. Table 1 shows the results.

[Example 10]
As an adhesive, a cooling tube, a nitrogen inlet tube, a thermometer, a reaction vessel equipped with a stirring device, n-butyl acrylate (BA): 58 parts, n-butyl methacrylate: 40 parts, and acrylic acid (AA): 2 Monomer mixture consisting of parts: 100 parts, polyoxyethylene alkylpropenyl phenyl ether ammonium sulfate as an emulsifier (Daiichi Kogyo Seiyaku Co., Ltd., trade name "Aquaron BC-2020"): 2 parts, polyoxyethylene dialkylphenyl ether Phosphoric acid (manufactured by Toho Chemical Industry Co., Ltd., trade name "Phosphanol RE-410", pKa = 2.7 (mixture of monoester and diester)): 2.4 parts, 2,2' as a polymerization initiator -Azobis(2-amidinopropane) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., trade name V-50): 0.03 part was added, water was added to obtain the desired solid content, and Emulsion polymerized for hours. After the polymerization was completed, 10% aqueous ammonia (manufactured by Kishida Chemical Co., Ltd., trade name: 10% aqueous ammonia) was added to the reaction solution to adjust the pH to 8.0, thereby obtaining an acrylic polymer emulsion. The obtained acrylic polymer had an SP value of 9.32 and a Tg of -28.6°C. 2 parts of an oxazoline cross-linking agent (trade name “Epocross WS-500” manufactured by Nippon Shokubai Co., Ltd.) were mixed with 100 parts of the solid content of this acrylic polymer emulsion to obtain an acrylic adhesive melt. A surface protection film (10) was obtained in the same manner as in Example 1, except that this acrylic pressure-sensitive adhesive solution was used as the pressure-sensitive adhesive. Table 1 shows the results.

[Comparative Example 1]
As a base resin, a propylene-based resin (manufactured by Japan Polypropylene Co., Ltd., trade name: Wintech WXK1233, propylene/ethylene random polymer obtained by polymerization with a metallocene catalyst) was used for the A layer and the C layer of the extruder. A surface protection film (C1) was obtained in the same manner as in Example 1 except for the above. Table 1 shows the results.

[Comparative Example 2]
As a base resin, a propylene-based resin (manufactured by Japan Polypropylene Co., Ltd., trade name: Wintech WXK1233, propylene/ethylene random polymer obtained by polymerization with a metallocene catalyst) was used for the A layer and the C layer of the extruder. A surface protection film (C2) was obtained in the same manner as in Example 2 except for the above. Table 1 shows the results.

[Comparative Example 3]
A surface protection film (C3) was obtained in the same manner as in Example 1, except that a polyethylene terephthalate (PET) film (Mitsubishi Plastics Co., Ltd., Diafoil T100, thickness: 100 μm) was used as the base resin. Table 1 shows the results.

[Comparative Example 4]
Example 1 except that a propylene-based resin (manufactured by Japan Polypropylene Corporation, trade name: Novatec PP SA06GA, a propylene homopolymer obtained by polymerization with a Ziegler catalyst) was used as the base resin for the B layer of the extruder. A surface protective film (C4) was obtained in the same manner. Table 1 shows the results.

[Comparative Example 5]
A surface protection film (C5) was obtained in the same manner as in Example 1 except that a polypropylene-polyethylene (PE-PP) blend film (manufactured by Futamura Chemical Co., Ltd., FBKW-BT, thickness 100 μm) was used as the base layer. rice field. Table 1 shows the results.

[Comparative Example 6]
Same as Example 1 except that low-density polyethylene (LDPE) (Nippon Polyethylene Co., Ltd., trade name: Novatec LDLC720) was used as the base resin for the A layer, B layer, and C layer of the extruder. to obtain a surface protective film (C6). Table 1 shows the results.

The surface protection film of the present invention can be used, for example, in the manufacture of members provided in mobile devices.

100 Surface protection film 10 Base layer (A)
11 Heat-resistant substrate layer (A1)
12 Soft substrate layer (A2)
13 Auxiliary substrate layer (A3)
20 Adhesive layer (B)

Claims (11)

A surface protective film having a substrate layer (A) and an adhesive layer (B),
The substrate layer (A) includes a heat-resistant substrate layer (A1) and a soft substrate layer (A2) in this order ,
The heat-resistant substrate layer (A1) is the outermost layer on the opposite side of the adhesive layer (B) of the substrate layer (A) and has a maximum peak temperature of 130° C. or higher by DSC measurement,
Storage elastic modulus at 120 ° C. is 50 MPa or less,
The heat-resistant substrate layer (A1) contains a propylene-based resin as a main component,
Used to protect the surface of the resin substrate when the resin plate is heat-pressed during the manufacture of a member provided in a mobile device,
surface protection film. 2. The surface protection film according to claim 1, having a total thickness of 80 μm to 180 μm. 3. The surface protection film according to claim 1, wherein the base layer (A) has a total thickness of 70 μm to 150 μm. 4. The surface protection film according to any one of claims 1 to 3, wherein the heat-resistant substrate layer (A1) has a thickness of 2 µm to 60 µm. 2. The surface protective film according to claim 1 , wherein said propylene-based resin is at least one selected from random polypropylene, block polypropylene, and homopolypropylene. 2. The surface protection film according to claim 1 , wherein the soft base material layer (A2) contains an ethylene-based resin as a main component. 7. The surface protection film according to claim 6 , wherein the ethylene-based resin (A2) is at least one selected from low-density polyethylene and ethylene-vinyl acetate copolymer. 8. Any one of claims 1 to 7 , wherein the substrate layer (A) comprises the heat resistant substrate layer (A1), the soft substrate layer (A2) and the auxiliary substrate layer (A3) in this order. surface protection film. 9. The surface protection film according to claim 8 , wherein the difference between the thickness of said auxiliary base layer (A3) and the thickness of said heat resistant base layer (A1) is ±50% or less. The surface protection according to claim 8 or 9 , wherein the main component resin contained in the auxiliary base layer (A3) is the same type of resin as the main component resin contained in the heat resistant base layer (A1). the film. 2. The surface protective film according to claim 1 , wherein the heating temperature during the hot press processing is 50.degree. C. to 180.degree.

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