CN116457203A

CN116457203A - Surface protective film

Info

Publication number: CN116457203A
Application number: CN202180074315.9A
Authority: CN
Inventors: 武田公平; 山下健太; 森大地
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2020-10-30
Filing date: 2021-10-05
Publication date: 2023-07-18

Abstract

Provided is a surface protection film which can be adhered to a resin substrate, wherein in a process of hot-pressing the resin substrate to which the surface protection film is adhered by a mold, breakage of the surface protection film during the hot-pressing can be suppressed, orange peel on the surface of the resin substrate after the hot-pressing can be suppressed, and the resin substrate has proper softness for enabling the hot-pressing process to be smoothly performed. The surface protection film according to an embodiment of the present invention has a base layer (a) and an adhesive layer (B), wherein the base layer (a) includes a base layer (A1), the base layer (A1) is the outermost layer on the opposite side of the base layer (a) from the adhesive layer (B), the friction force of the base layer (A1) at 130 ℃ is 4.5N or less, and the storage modulus of the surface protection film at 120 ℃ is 50MPa or less.

Description

Surface protective film

Technical Field

The present invention relates to a surface protective film. Typically, the present invention relates to a surface protective film used for manufacturing a member provided in a mobile device.

Background

Mobile communication performance of so-called mobile devices such as smartphones, tablet terminals, and notebook computers has been rapidly improved in recent years. In particular, recently, new high-performance mobile communication standards (e.g., 5G standards, etc.) capable of ultra-high speed, ultra-large capacity, ultra-low latency, and ultra-large volume connections are being increasingly adopted.

In order to sufficiently exhibit the performance of such a novel high-performance mobile communication, a case of a mobile device needs to employ a material that is not susceptible to electric waves. Therefore, as a case of a mobile device, there is a need to gradually replace a metal case that has been used in many cases in the past with a resin case or the like that is not easily affected by radio waves.

On the other hand, in recent years, the external appearance of mobile devices has also been greatly improved, and typically, mobile devices having a case with a three-dimensional curved surface structure are becoming common devices.

When the housing of the mobile device is a metal housing, the housing having various three-dimensional curved surface structures can be manufactured by using established metal processing techniques.

On the other hand, when the casing of the mobile device is a resin casing, a three-dimensional curved surface processing technique of the resin substrate is required, but there are a large number of problems in the present situation.

In order to process the resin substrate, hot pressing is generally used. In this hot press, the resin substrate is held in a mold designed to a desired shape and pressed at a high temperature. At this time, surface protection films are attached to both surfaces of the resin substrate in order to protect the surfaces of the resin substrate.

However, when the conventional surface protective film is used for hot pressing of a resin substrate, there are the following problems: in curved surface processing by pressing at high temperature, the surface protective film cannot smoothly follow the mold, and cracking of the surface protective film is likely to occur.

In addition, when the conventional surface protective film (patent document 1) is used for hot pressing of a resin substrate, there is a problem that positional displacement of the surface protective film is likely to occur due to pressing at high temperature, and orange peel (with marks) is likely to occur on the surface of the resin substrate after pressing.

Further, the surface protective films to be adhered to both surfaces of the resin substrate are required to have an appropriate softness in order to perform three-dimensional curved surface processing on the resin substrate by hot pressing. That is, when the surface protection films adhered to both surfaces of the resin substrate are too hard, it is difficult to follow the three-dimensional curved shape of the mold, and when the surface protection films adhered to both surfaces of the resin substrate are too soft, positional displacement and wrinkles of the surface protection films are likely to occur (patent document 1).

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 5-302068

Disclosure of Invention

Problems to be solved by the invention

The invention provides a surface protection film which can be adhered to a resin substrate, wherein in a process of hot-pressing the resin substrate adhered with the surface protection film by using a mould, the breakage of the surface protection film during the hot-pressing can be restrained, orange peel on the surface of the resin substrate after the hot-pressing can be restrained, and the resin substrate has proper softness which enables the hot-pressing process to be smoothly carried out.

Solution for solving the problem

The surface protection film in the embodiment of the present invention has a base material layer (A) and an adhesive layer (B),

the substrate layer (A) comprises a substrate layer (A1),

the base material layer (A1) is the outermost layer on the opposite side of the base material layer (A) from the adhesive layer (B),

the friction force of the base material layer (A1) at 130 ℃ is below 4.5N,

the storage modulus of the surface protection film at 120 ℃ is below 50 MPa.

In one embodiment, the total thickness of the surface protective film in the embodiment of the present invention is 20 μm to 180 μm.

In one embodiment, the thickness of the entire base material layer (A) is 10 μm to 150. Mu.m.

In one embodiment, the thickness of the base material layer (A1) is 1 μm to 60. Mu.m.

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

In one embodiment, the base material layer (A1) contains a release agent.

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

In one embodiment, the release agent includes a silicone release agent.

In one embodiment, the silicone-based release agent includes a silylated polyolefin.

In one embodiment, the base material layer (A1) includes at least 1 selected from the group consisting of vinyl resins and propylene resins.

In one embodiment, the vinyl resin includes high-density polyethylene.

In one embodiment, the propylene-based resin comprises at least 1 selected from the group consisting of random polypropylene, block polypropylene and homo-polypropylene.

In one embodiment, the base material layer (A1) includes a pentene resin.

In one embodiment, the base material layer (a) includes the base material layer (A1) and the base material layer (A2) in this order.

In one embodiment, the base material layer (A2) includes a vinyl resin.

In one embodiment, the vinyl resin includes at least 1 selected from the group consisting of low density polyethylene and ethylene-vinyl acetate copolymer.

In one embodiment, the base material layer (A2) includes a propylene resin.

In one embodiment, the propylene resin comprises a homopolypropylene.

In one embodiment, the base material layer (a) includes the base material layer (A1), the base material layer (A2), and an auxiliary base material layer (A3) in this order.

In one embodiment, the thickness of the auxiliary base material layer (A3) and the thickness of the base material layer (A1) have an error of ±50% or less.

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

In one embodiment, the surface protective film according to the embodiment of the present invention is used for manufacturing a member provided in a mobile device.

In one embodiment, the surface protection film according to the embodiment of the present invention is used for protecting the surface of a resin substrate when the resin substrate is subjected to hot press processing.

In one embodiment, the heating temperature at the time of the hot press is 50 to 250 ℃.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a surface protective film that can be adhered to a resin substrate, wherein in a step of hot-pressing the resin substrate to which the surface protective film is adhered by using a mold, breakage of the surface protective film during the hot-pressing can be suppressed, orange peel on the surface of the resin substrate after the hot-pressing can be suppressed, and the resin substrate has a proper softness that enables the hot-pressing step to be smoothly performed.

Drawings

Fig. 1 is a schematic cross-sectional view of a surface protective film according to an embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of a surface protective film according to another embodiment of the present invention.

Fig. 3 is a schematic cross-sectional view of a surface protective film according to still another embodiment of the present invention.

Fig. 4 is an explanatory diagram showing a method of evaluating high-temperature sliding properties.

Detailed Description

Surface protective film 1

The surface protection film according to the embodiment of the present invention has a base material layer (a) and an adhesive layer (B), wherein the base material layer (a) includes a base material layer (A1), and the base material layer (A1) is the outermost layer on the opposite side of the base material layer (a) from the adhesive layer (B).

The surface protective film according to the embodiment of the present invention may be provided with any suitable other layer within a range that does not impair the effects of the present invention.

The base material layer (a) is preferably formed of 2 or more layers.

The base material layer (a) preferably includes a base material layer (A1) and a base material layer (A2) in this order.

The base material layer (a) more preferably includes a base material layer (A1), a base material layer (A2), and an auxiliary base material layer (A3) in this order.

The pressure-sensitive adhesive layer (B) may be a pressure-sensitive adhesive layer formed of only 1 layer, or may be a pressure-sensitive adhesive layer formed of a laminate of 2 or more layers.

The total thickness of the surface protective film in the embodiment of the present invention is preferably 20 μm to 180 μm. When the total thickness of the surface protective film in the embodiment of the present invention is within the above range, the effect of the present invention can be further exhibited. When the total thickness of the surface protective film in the embodiment of the present invention is too small, there is a concern that the film may not sufficiently exhibit the function as the surface protective film when used for the hot pressing of the resin substrate, and for example, there is a concern that positional displacement and wrinkles of the surface protective film may be easily generated by the pressing at high temperature. When the total thickness of the surface protective film according to the embodiment of the present invention is too thick, there is a concern that the film may not sufficiently exhibit the function as the surface protective film when used for hot pressing of a resin substrate, and for example, it becomes difficult to follow the shape of a mold.

The total thickness of the surface protective film in the embodiment of the present invention is preferably 20 μm to 150 μm, more preferably 20 μm to 120 μm, still more preferably 20 μm to 100 μm, still more preferably 20 μm to 80 μm, particularly preferably 20 μm to 60 μm, and most preferably 30 μm to 50 μm when the thickness is required to be thin.

The total thickness of the surface protective film in the embodiment of the present invention is preferably 60 μm to 180 μm, more preferably 70 μm to 170 μm, still more preferably 80 μm to 160 μm, particularly preferably 85 μm to 150 μm, and most preferably 90 μm to 140 μm when an appropriate thickness is required.

The thickness of the entire base material layer (A) is preferably 10 μm to 150. Mu.m. When the thickness of the entire base material layer (a) is within the above range, the effect of the present invention can be further exhibited. When the thickness of the entire base material layer (a) is too small, there is a concern that the resin substrate may not sufficiently exhibit the function as a surface protective film when used for hot pressing, and for example, there is a concern that positional displacement and wrinkles of the surface protective film may easily occur due to pressing at high temperature. When the thickness of the entire base material layer (a) is too large, there is a concern that the resin substrate may not sufficiently exhibit the function as a surface protective film when used for hot pressing of the resin substrate, and that it becomes difficult to follow the shape of a mold, for example.

When the thickness of the entire base material layer (a) is required to be small, the thickness is preferably 10 μm to 120 μm, more preferably 10 μm to 100 μm, still more preferably 10 μm to 80 μm, still more preferably 10 μm to 60 μm, particularly preferably 15 μm to 50 μm, and most preferably 20 μm to 40 μm.

The thickness of the entire base material layer (A) is preferably 50 μm to 150 μm, more preferably 65 μm to 140 μm, still more preferably 75 μm to 140 μm, particularly preferably 80 μm to 135 μm, and most preferably 85 μm to 135 μm when an appropriate thickness is required.

The sliding heat resistant substrate layer (A1) of the surface protective film in the embodiment of the present invention preferably has a friction force at 130 ℃ of 4.5N or less, more preferably 4.0N or less, still more preferably 3.5N or less, particularly preferably 3.0N or less, and most preferably 2.5N or less. The lower limit value of the friction force is preferably 0.1N or more in reality. When the friction force at 130 ℃ of the sliding heat resistant base material layer (A1) in the embodiment of the present invention is within the above range, the effect of the present invention can be further exhibited. In particular, when the friction force of the sliding heat resistant base material layer (A1) at 130 ℃ is within the above range in the embodiment of the present invention, the cracking of the surface protective film at the time of hot pressing can be further suppressed in the step of hot pressing the resin substrate to which the surface protective film is adhered by using the mold. When the friction force of the sliding heat resistant base material layer (A1) at 130 ℃ is too large in the embodiment of the present invention, there is a concern that the surface protective film may not smoothly follow the mold during curved surface processing by pressing at high temperature in the case of hot pressing for a resin substrate, and there is a concern that breakage of the surface protective film may occur.

The storage modulus of the surface protective film in the embodiment of the present invention at 120℃is preferably 50MPa or less, more preferably 50MPa to 0.5MPa, still more preferably 50MPa to 1MPa, particularly preferably 45MPa to 1.5MPa, and most preferably 40MPa to 2MPa. When the storage modulus at 120 ℃ of the surface protective film according to the embodiment of the present invention is within the above range, the surface protective film has an appropriate softness, and can realize good three-dimensional curved surface processing when used for hot pressing of a resin substrate. When the storage modulus of the surface protective film according to the embodiment of the present invention is too low at 120 ℃, the surface protective film is too soft, and therefore there is a concern that positional displacement and wrinkles of the surface protective film may occur. When the storage modulus at 120 ℃ is too high, the surface protective film of the embodiment of the present invention is too hard, and therefore, it is likely that it becomes difficult to follow the three-dimensional curved shape of the mold.

Fig. 1 is a schematic cross-sectional view of a surface protective film according to an embodiment of the present invention. In fig. 1, the surface protective film 100 includes a base material layer (a) 10 and an adhesive layer (B) 20, and the outermost layer of the base material layer (a) on the opposite side of the adhesive layer (B) is a base material layer (A1) 11.

Fig. 2 is a schematic cross-sectional view of a surface protective film according to another embodiment of the present invention. In fig. 2, the surface protection film 100 includes a base layer (a) 10 and an adhesive layer (B) 20, wherein the outermost layer of the base layer (a) on the opposite side of the adhesive layer (B) is a base layer (A1) 11, and a base layer (A2) 12 is provided between the base layer (A1) 11 and the adhesive layer (B) 20. That is, the surface protection film 100 shown in fig. 2 has a base material layer (A1) 11, a base material layer (A2) 12, and an adhesive layer (B) 20 in this order.

Fig. 3 is a schematic cross-sectional view of a surface protective film according to still another embodiment of the present invention. In fig. 3, the surface protective film 100 includes a base layer (a) 10 and an adhesive layer (B) 20, wherein the outermost layer of the base layer (a) on the opposite side of the adhesive layer (B) is a base layer (A1) 11, a base layer (A2) 12 is provided between the base layer (A1) 11 and the adhesive layer (B) 20, and an auxiliary base layer (A3) 13 is provided between the base layer (A2) 12 and the adhesive layer (B) 20. That is, the surface protection film 100 shown in fig. 3 has a base material layer (A1) 11, a base material layer (A2) 12, an auxiliary base material layer (A3) 13, and an adhesive layer (B) 20 in this order.

1-1 substrate layer (A)

As shown in fig. 1 to 3, the base material layer (a) includes a base material layer (A1) as an outermost layer on the opposite side of the adhesive layer (B).

The base material layer (a) preferably includes a base material layer (A1) and a base material layer (A2) in this order as shown in fig. 2 to 3.

The base material layer (a) more preferably includes a base material layer (A1), a base material layer (A2), and an auxiliary base material layer (A3) in this order as shown in fig. 3.

The entire base material layer (a) preferably contains an olefin resin as a main component. Specifically, the content ratio of the olefin resin contained in the entire base material layer (a) is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, still more preferably 90 to 100% by weight, still more preferably 95 to 100% by weight, particularly preferably 98 to 100% by weight, and most preferably substantially 100% by weight. The effect of the present invention can be further exhibited by including the olefinic resin as a main component in the entire base material layer (a).

In the present specification, the expression "substantially 100 wt%" means that a trace amount of impurities or the like may be contained within a range that does not impair the effect of the present invention, and may be generally referred to as "100 wt%".

The number of the olefin-based resins contained in the entire base material layer (a) may be 1 or 2 or more.

Any suitable olefin resin may be used as the olefin resin within a range that does not impair the effects of the present invention. In view of the further effect of the present invention, examples of such olefin resins include at least 1 selected from the group consisting of vinyl resins, propylene resins, butene resins and pentene resins, and preferably at least 1 selected from the group consisting of vinyl resins, propylene resins and pentene resins.

Any suitable vinyl resin may be used as the vinyl resin within a range that does not impair the effects of the present invention. Examples of such ethylene resins include at least one selected from Low Density Polyethylene (LDPE), linear Low Density Polyethylene (LLDPE), ultra low density polyethylene (LLDPE), medium Density Polyethylene (MDPE), high Density Polyethylene (HDPE), ultra high density polyethylene, and copolymers of ethylene and other monomers (for example, ethylene/vinyl acetate copolymer, ethylene/acrylic acid copolymer, ethylene/methacrylic acid copolymer, ethylene/acrylic acid ester copolymer, ethylene/methacrylic acid ester copolymer, ethylene/butene-1 copolymer, ethylene/propylene/butene-1 copolymer, ethylene/alpha-olefin copolymer having 5 to 12 carbon atoms, ethylene/nonconjugated diene copolymer, and the like), and at least 1 selected from high density polyethylene, low density polyethylene, and ethylene/vinyl acetate copolymer is preferable.

The ethylene resin may be a Ziegler-Natta ethylene resin obtained by using a Ziegler-Natta catalyst.

The vinyl resin may be a metallocene vinyl resin obtained by using a metallocene catalyst. Examples of such metallocene-based vinyl resins include at least 1 selected from the group consisting of metallocene-based low-density polyethylene and metallocene-based ethylene/vinyl acetate copolymers.

Any suitable propylene resin may be used as the propylene resin within a range that does not impair the effects of the present invention. Examples of such propylene resins include at least 1 selected from the group consisting of random polypropylene, block polypropylene, homo-polypropylene, and copolymers of propylene and other monomers.

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

The propylene-based resin may be a metallocene propylene-based resin obtained by using a metallocene catalyst. Examples of such a metallocene-based propylene resin include at least 1 selected from the group consisting of metallocene-based random polypropylene, metallocene-based block polypropylene, metallocene-based homo-polypropylene, and copolymers of metallocene-based propylene and other monomers.

Any suitable butene resin may be used as the butene resin within a range that does not impair the effects of the present invention. Examples of such butene-based resins include at least 1 selected from polybutene-1 and copolymers of butene-1 and an α -olefin.

The butene-based resin may be a Ziegler-Natta butene-based resin obtained by using a Ziegler-Natta catalyst.

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

Any suitable pentene-based resin may be used as the pentene-based resin within a range that does not impair the effects of the present invention. Examples of such a pentene-based resin include at least 1 selected from the group consisting of poly (4-methylpentene-1), copolymers of 4-methylpentene-1 and other monomers, poly (3-methylpentene-1), and copolymers of 3-methylpentene-1 and other monomers. From the viewpoint of further exhibiting the effect of the present invention, at least 1 selected from the group consisting of poly (4-methylpentene-1) and copolymers of 4-methylpentene-1 and other monomers is exemplified as the pentene-based resin, and a trade name "TPX (registered trademark)" manufactured by mitsunobu chemical company, which is a crystalline pentene-based resin using 4-methylpentene-1 as a main raw material, is typically exemplified.

The pentene-based resin may be a Ziegler-Natta-pentene-based resin obtained using a Ziegler-Natta catalyst.

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

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

<1-1-1. Substrate layer (A1) >

The base material layer (A1) is the outermost layer on the opposite side of the base material layer (a) from the adhesive layer (B).

The thickness of the base material layer (A1) is preferably 1 μm to 60. Mu.m. When the thickness of the base material layer (A1) is within the above range, the effect of the present invention can be further exhibited. When the thickness of the base material layer (A1) is too small, the heat resistance is poor, and when the resin substrate is used for hot pressing, there is a concern that adhesion of the surface protective film to a mold due to melting or the like is likely to occur, and there is a concern that positional displacement and wrinkles of the surface protective film are likely to occur due to pressing at high temperature. When the thickness of the base material layer (A1) is too large, for example, when the resin substrate is used for hot pressing, it is difficult to follow the shape of the mold.

When the thickness of the base material layer (A1) is required to be small, the thickness is preferably 1 μm to 50. Mu.m, more preferably 1 μm to 40. Mu.m, still more preferably 1 μm to 30. Mu.m, still more preferably 1 μm to 20. Mu.m, particularly preferably 2 μm to 10. Mu.m, and most preferably 3 μm to 8. Mu.m.

The thickness of the base material layer (A1) is preferably 2 μm to 60 μm, more preferably 3 μm to 50 μm, still more preferably 4 μm to 40 μm, particularly preferably 5 μm to 30 μm when an appropriate thickness is required.

The base material layer (A1) may be formed of only 1 layer or 2 or more layers. When the substrate layer (A1) is 2 or more layers, each layer may be formed of the same composition or may be at least 1 layer different from the other layers.

The base material layer (A1) is preferably 1 to 5 layers, more preferably 1 to 3 layers, still more preferably 1 to 2 layers, particularly preferably 1 layer.

The substrate layer (A1) preferably has a maximum peak temperature of 130℃or higher as measured by DSC. When the maximum peak temperature of the base material layer (A1) measured by DSC is within the above range, the heat resistance can be made excellent, and therefore the effect of the present invention can be further exhibited. When the maximum peak temperature of the base material layer (A1) measured by DSC is too low, the heat resistance is poor, and when the base material layer is used for hot pressing of a resin substrate, there is a concern that adhesion of the surface protective film to a mold due to melting or the like is likely to occur, and there is a concern that positional displacement and wrinkles of the surface protective film are likely to occur due to pressing at high temperature. When the maximum peak temperature of the base material layer (A1) measured by DSC is too high, there is a concern that the surface protective film is difficult to follow the three-dimensional curved shape of the mold when used for hot pressing of a resin substrate.

The maximum peak temperature of the base material layer (A1) measured by DSC is preferably 150 ℃ or higher, more preferably 160 ℃ or higher, still more preferably 180 ℃ or higher, particularly preferably 200 ℃ or higher, and most preferably 220 ℃ or higher, from the viewpoint that heat resistance against hot pressing can be improved and the effect of the present invention can be further exhibited. The upper limit value of the maximum peak temperature of the base material layer (A1) measured by DSC is preferably 500 ℃ or less, more preferably 400 ℃ or less, further preferably 350 ℃ or less, particularly preferably 300 ℃ or less, and most preferably 250 ℃ or less, in view of difficulty in processing, etc.

The maximum peak temperature of the base material layer (A1) measured by DSC is preferably 130 to 300 °, more preferably 130 to 250 ℃, still more preferably 130 to 220 ℃, particularly preferably 130 to 200 ℃, and most preferably 130 to 180 ℃ in terms of maintaining heat resistance to hot pressing and facilitating processing.

The base material layer (A1) may contain any suitable resin within a range that does not impair the effects of the present invention. The base material layer (A1) preferably contains at least 1 selected from the group consisting of vinyl resins, propylene resins, butene resins, and pentene resins. When the base material layer (A1) does not contain at least 1 selected from the group consisting of vinyl resins, acrylic resins, butene resins, and pentene resins, there is a concern that the heat resistance of the outermost surface of the base material layer (a) is poor, and when the surface protective film according to the embodiment of the present invention is used for hot pressing of a resin substrate, there is a concern that adhesion of the surface protective film to a mold due to melting or the like is likely to occur, and there is a concern that positional displacement and wrinkles of the surface protective film are likely to occur due to pressing at high temperature.

[ 1-1-1-1. Substrate layer (A1) preferred embodiment 1 ]

In one preferred embodiment 1 of the base material layer (A1), the base material layer (A1) more preferably contains at least 1 selected from the group consisting of vinyl resins and propylene resins. The effect of the present invention can be further exhibited by including at least 1 selected from the group consisting of vinyl resins and propylene resins in the base material layer (A1). In particular, when the base material layer (A1) contains at least 1 selected from the group consisting of vinyl resins and propylene resins, the outermost surface of the base material layer (a) can have excellent heat resistance, and thus the effects of the present invention can be further exhibited.

The content ratio of at least 1 selected from the group consisting of the vinyl resin and the propylene resin which can be contained in the base material layer (A1) is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, further preferably 90 to 100% by weight, further preferably 95 to 100% by weight, particularly preferably 98 to 100% by weight, and most preferably substantially 100% by weight. The substrate layer (A1) can further exhibit the effect of the present invention when the content ratio of at least 1 selected from the group consisting of vinyl resins and propylene resins falls within the above-described range. In particular, when the content ratio of at least 1 selected from the group consisting of the vinyl-based resin and the propylene-based resin in the base layer (A1) falls within the above range, the outermost surface of the base layer (a) can have excellent heat resistance, and thus the effect of the present invention can be further exhibited. When the content ratio of at least 1 selected from the vinyl-based resin and the propylene-based resin in the base material layer (A1) is out of the above range, there is a concern that the heat resistance of the outermost surface of the base material layer (a) is poor, and when the surface protective film according to the embodiment of the present invention is used for hot pressing of a resin substrate, there is a concern that adhesion of the surface protective film to a mold due to melting or the like is likely to occur, and there is a concern that positional displacement and wrinkles of the surface protective film are likely to occur due to pressing at high temperature.

Any suitable vinyl resin may be used as the vinyl resin that can be contained in the base layer (A1) within a range that does not impair the effects of the present invention. Examples of such an ethylene resin include at least one selected from 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 (for example, ethylene/vinyl acetate copolymer, ethylene/acrylic acid copolymer, ethylene/methacrylic acid copolymer, ethylene/acrylic acid ester copolymer, ethylene/methacrylic acid ester copolymer, ethylene/butene-1 copolymer, ethylene/propylene/butene-1 copolymer, ethylene/alpha-olefin copolymer having 5 to 12 carbon atoms, ethylene/nonconjugated diene copolymer, and the like), and at least 1 selected from high density polyethylene, low density polyethylene, and ethylene/vinyl acetate copolymer, and more preferably high density polyethylene.

The ethylene resin that can be contained in the base layer (A1) may be a ziegler-natta ethylene resin obtained using a ziegler-natta catalyst.

The vinyl resin that can be contained in the base material layer (A1) may be a metallocene vinyl resin obtained by using a metallocene catalyst. Examples of such metallocene-based vinyl resins include at least 1 selected from the group consisting of metallocene-based low-density polyethylene and metallocene-based ethylene/vinyl acetate copolymers.

The vinyl resin that can be contained in the base material layer (A1) may be 1 or 2 or more.

The vinyl resin that can be contained in the base layer (A1) may be a commercially available resin.

The propylene resin that can be contained in the base layer (A1) may be any suitable propylene resin as long as the effect of the present invention is not impaired. Examples of such propylene resins include at least 1 selected from the group consisting of random polypropylene, block polypropylene, homo-polypropylene, and copolymers of propylene and other monomers.

The propylene resin that can be contained in the base material layer (A1) may be 1 or 2 or more.

Typical examples of the homo-polypropylene include isotactic homo-polypropylene, atactic homo-polypropylene and syndiotactic homo-polypropylene.

As the copolymer of propylene with other monomers, any suitable copolymer may be used within a range that does not impair the effects of the present invention. Examples of such a copolymer of propylene and another monomer include a propylene/ethylene copolymer, a propylene/ethylene/1-butene copolymer, and a propylene/C5-12 alpha-olefin copolymer.

The propylene-based resin that can be contained in the base material layer (A1) may be a ziegler-natta propylene-based resin obtained using a ziegler-natta catalyst.

The propylene resin that can be contained in the base material layer (A1) may be a metallocene propylene resin obtained by using a metallocene catalyst. Examples of such a metallocene-based propylene resin include at least 1 selected from the group consisting of metallocene-based random polypropylene, metallocene-based block polypropylene, metallocene-based homo-polypropylene, and copolymers of metallocene-based propylene and other monomers.

The propylene resin that can be contained in the base layer (A1) may be commercially available ones.

The base material layer (A1) preferably contains a release agent. By including the release agent in the base material layer (A1), the surface protective film can easily follow the mold smoothly during curved surface processing by pressing at high temperature, and cracking of the surface protective film is less likely to occur.

The number of the release agents that can be contained in the base material layer (A1) may be 1 or 2 or more.

As means for incorporating the release agent into the base material layer (A1), any suitable means may be employed within a range that does not impair the effects of the present invention. Examples of such means include: a method of containing a release agent (contained by kneading or the like) in a material (resin composition) for forming the base material layer (A1), a method of applying a coating liquid containing a release agent, and the like.

The content ratio of the release agent in the base material layer (A1) is preferably 0.1 to 30 wt%, more preferably 0.1 to 20 wt%, still more preferably 0.1 to 15 wt%, particularly preferably 0.1 to 10 wt%, and most preferably 0.1 to 7.5 wt%. When the content ratio of the release agent in the base material layer (A1) is within the above range, the surface protective film can follow the mold more easily and smoothly during curved surface processing by pressing at high temperature, and cracking of the surface protective film is less likely to occur.

Any suitable release agent may be used as the release agent that can be contained in the base material layer (A1) within a range that does not impair the effects of the present invention. In order to further exhibit the effects of the present invention, a release agent having excellent mixing properties and adhesion with the resin component contained in the base layer (A1) is preferable.

Examples of the release agent that can be contained in the base layer (A1) include ethylene-vinyl alcohol copolymer, fatty acid amide-based additive, low molecular weight polyolefin wax, long chain alkyl-based additive, polymethylpentene, and silicone-based release agent.

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

Examples of the fatty acid amide-based additive include saturated fatty acid bisamides, unsaturated fatty acid bisamides, aromatic bisamides, and substituted ureas. Specific examples of the fatty acid amide-based additive include N-stearyl-N '-stearamide such as methylene distearamide, ethylene dioleate amide, N-dioleyladipamide, and N-stearyl-N' -stearyl urea.

Examples of the low molecular weight polyolefin wax include low molecular weight materials such as polyethylene wax and polypropylene wax.

Examples of the long-chain alkyl-based additive include low-molecular-weight additives having an alkyl chain such as PEELOIL (registered trademark) 1010 and PEELOIL (registered trademark) 1010S (both of which are manufactured by oil and fat industries, ltd).

Examples of the polymethylpentene include crystalline olefin-based polymer containing 4-methylpentene-1 as a main material, such as TPX (registered trademark) MX001 and TPX (registered trademark) MX004 (all of which are manufactured by mitsunobu chemical Co., ltd.).

Examples of the silicone-based release agent include silylated polyolefin, silicone resin, silicone alkoxy oligomer, silicone master batch pellet, silicone rubber powder, silicone emulsion, and the like. Examples of the silylated polyolefin include a silylated polyolefin produced by the method shown in the example of Japanese patent application laid-open No. 2011-26448.

The release agent is preferably at least 1 selected from a long-chain alkyl-based additive and a silicone-based release agent, and more preferably a silicone-based release agent, in view of the ease with which the surface protective film follows the mold further smoothly and the less likely breakage of the surface protective film occurs during curved surface processing by pressing at high temperature.

Among the silicone-based release agents, a silylated polyolefin is preferred in terms of ease of following the mold further smoothly and less likely to cause cracking of the surface protective film during curved surface processing by pressing at high temperature.

The base material layer (A1) may contain any suitable other resin component within a range that does not impair the effects of the present invention.

The base material layer (A1) may contain any appropriate additive as required. Examples of the additive that can be contained in the base material layer (A1) include ultraviolet absorbers, heat-resistant stabilizers, fillers, lubricants, colorants (dyes, etc.), antioxidants, die build-up (Die drool) inhibitors, antiblocking agents, foaming agents, polyethyleneimine, and the like. These may be 1 kind or 2 or more kinds. The content ratio of the additive in the base material layer (A1) is preferably 10% by weight or less, more preferably 7% by weight or less, further preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

Examples of the ultraviolet absorber include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. The ultraviolet absorber may be used in any suitable amount as long as it does not bleed out during molding. Typically, the resin component (preferably, propylene resin) in the base material layer (A1) is preferably 0.01 to 5 wt%.

Examples of the heat-resistant stabilizer include hindered amine compounds, phosphorus compounds, and cyanoacrylate compounds. As for the content of the heat-resistant stabilizer, any suitable content may be used as long as it does not bleed out at the time of molding. Typically, the resin component (preferably, propylene resin) in the base material layer (A1) is preferably 0.01 to 5 wt%.

Examples of the filler include inorganic fillers such as talc, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, silica, clay, mica, barium sulfate, whiskers, and magnesium hydroxide. The average particle diameter of the filler is preferably 0.1 μm to 20. Mu.m. The filler may be present in any suitable amount. Typically, the resin component (preferably, propylene resin) in the base material layer (A1) is preferably 1 to 200 wt%.

[ 1-1-1-2. Substrate layer (A1) preferred embodiment 2 ]

In one preferred embodiment 2 of the base material layer (A1), the base material layer (A1) more preferably contains a pentene-based resin. The effect of the present invention can be further exhibited by including a pentene-based resin in the base material layer (A1). In particular, when the substrate layer (A1) contains a pentene-based resin, the outermost surface of the substrate layer (a) can have more excellent heat resistance, and thus the effect of the present invention can be further exhibited. In particular, by including the pentene-based resin in the base material layer (A1), even when the thickness of the base material layer (A1) is reduced, in the step of hot-pressing the resin substrate to which the surface protective film according to the embodiment of the present invention is attached by using a mold, cracking of the surface protective film during the hot-pressing can be sufficiently suppressed, and orange peel on the surface of the resin substrate after the hot-pressing can be sufficiently suppressed. Further, since the thickness of the base material layer (A1) can be reduced, the surface protective film according to the embodiment of the present invention can be given an appropriate softness that enables the hot pressing process to be performed smoothly.

The content ratio of the pentene resin which can be contained in the base layer (A1) is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, still more preferably 90 to 100% by weight, still more preferably 95 to 100% by weight, particularly preferably 98 to 100% by weight, and most preferably substantially 100% by weight. When the content ratio of the pentene-based resin in the base material layer (A1) falls within the above range, the effect of the present invention can be further exhibited. In particular, when the content ratio of the pentene-based resin in the base material layer (A1) falls within the above range, the outermost surface of the base material layer (a) can have more excellent heat resistance, and thus the effect of the present invention can be further exhibited. When the content ratio of the pentene-based resin in the base material layer (A1) is deviated from the above range, there is a concern that the heat resistance of the outermost surface of the base material layer (a) is poor, and when the surface protective film in the embodiment of the present invention is used for hot pressing of a resin substrate, there is a concern that adhesion of the surface protective film to a mold due to melting or the like is likely to occur, and there is a concern that positional deviation and wrinkles of the surface protective film are likely to occur due to pressing at high temperature.

The pentene resin that can be contained in the base layer (A1) may be any suitable pentene resin as long as the effect of the present invention is not impaired. Examples of such a pentene-based resin include at least 1 selected from the group consisting of poly (4-methylpentene-1), copolymers of 4-methylpentene-1 and other monomers, poly (3-methylpentene-1), and copolymers of 3-methylpentene-1 and other monomers. From the viewpoint of further exhibiting the effect of the present invention, at least 1 selected from the group consisting of poly (4-methylpentene-1) and copolymers of 4-methylpentene-1 and other monomers is exemplified as the pentene-based resin, and a trade name "TPX (registered trademark)" manufactured by mitsunobu chemical company, which is a crystalline pentene-based resin using 4-methylpentene-1 as a main raw material, is typically exemplified.

In embodiment 2, the base material layer (A1) preferably contains no release agent. In embodiment 2, even when the base material layer (A1) does not contain a release agent, the surface protective film can smoothly follow the mold during curved surface processing by pressing at high temperature, and breakage of the surface protective film is less likely to occur.

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

In the present specification, the term "substantially 0 wt%" means that the composition may be contained in an extremely small amount within a range that does not impair the effect of the present invention, and may be generally referred to as "0 wt%".

In embodiment 2, the number of release agents that can be contained in the base material layer (A1) may be 1 or 2 or more.

In embodiment 2, the description of one preferred embodiment 1 of the substrate layer (A1) can be cited as to the kind of the release agent that can be contained in the substrate layer (A1) and the means for containing the release agent.

In addition to the release agent described above, the base material layer (A1) may contain any appropriate additive as required. Examples of the additive that can be contained in the base material layer (A1) include ultraviolet absorbers, heat-resistant stabilizers, fillers, lubricants, colorants (dyes, etc.), antioxidants, die build-up (Die drool) inhibitors, antiblocking agents, foaming agents, polyethyleneimine, and the like. These may be 1 kind or 2 or more kinds. The content ratio of the additive in the base material layer (A1) is preferably 10% by weight or less, more preferably 7% by weight or less, further preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

<1-1-2. Substrate layer (A2) >

The base material layer (a) preferably includes a base material layer (A1) and a base material layer (A2) in this order. That is, the base material layer (A2) is disposed between the base material layer (A1) and the adhesive layer (B).

The thickness of the base material layer (A2) is preferably 10 μm to 125. Mu.m. When the thickness of the base material layer (A2) is within the above range, the effect of the present invention can be further exhibited. When the thickness of the base material layer (A2) is too small, the surface protective film is too hard, and therefore, it may become difficult to follow the three-dimensional curved shape of the mold. When the thickness of the base material layer (A2) is too large, the surface protective film is too soft, and there is a concern that positional displacement and wrinkles of the surface protective film occur.

When the thickness of the base material layer (A2) is required to be small, the thickness is preferably 10 μm to 100 μm, more preferably 10 μm to 80 μm, still more preferably 10 μm to 60 μm, still more preferably 10 μm to 50 μm, particularly preferably 15 μm to 40 μm, and most preferably 20 μm to 30 μm.

The thickness of the base material layer (A2) is preferably 25 μm to 125 μm, more preferably 30 μm to 120 μm, still more preferably 40 μm to 105 μm, particularly preferably 50 μm to 90 μm when an appropriate thickness is required.

The base material layer (A2) may be formed of only 1 layer or 2 or more layers. When the substrate layer (A2) is 2 or more layers, each layer may be formed of the same composition or may be at least 1 layer different from the other layers.

The base material layer (A2) is preferably 1 to 5 layers, more preferably 1 to 3 layers, still more preferably 1 to 2 layers, particularly preferably 1 layer.

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

The base material layer (A2) preferably contains at least 1 selected from the group consisting of vinyl resins and propylene resins. The effect of the present invention can be further exhibited by including at least 1 selected from the group consisting of vinyl resins and propylene resins in the base material layer (A2). When the base material layer (A2) does not contain at least 1 selected from the group consisting of vinyl resins and acrylic resins, there is a concern that the surface protective film in the embodiment of the present invention cannot have adequate softness, that positional displacement and wrinkles of the surface protective film are likely to occur, and that it becomes difficult to follow the three-dimensional curved shape of the mold.

[ 1-1-2-1. Substrate layer (A2) preferred embodiment 1 ]

In one preferred embodiment 1 of the base material layer (A2), the base material layer (A2) preferably contains a vinyl resin. The effect of the present invention can be further exhibited by including the vinyl resin in the base material layer (A2). In particular, by including the vinyl resin in the base material layer (A2), the surface protective film according to the embodiment of the present invention has an appropriate softness, and can realize a good three-dimensional curved surface processing when used for hot pressing of a resin substrate.

The content ratio of the vinyl resin that can be contained in the base material layer (A2) is preferably 50 to 100 wt%, more preferably 70 to 100 wt%, even more preferably 90 to 100 wt%, particularly preferably 95 to 100 wt%, and most preferably substantially 100 wt%. When the content ratio of the vinyl resin in the base material layer (A2) falls within the above range, the effect of the present invention can be further exhibited. In particular, when the content ratio of the vinyl resin in the base material layer (A2) is within the above range, the surface protective film according to the embodiment of the present invention has an appropriate softness, and can realize good three-dimensional curved surface processing when used for hot pressing of a resin substrate. When the content ratio of the vinyl resin in the base material layer (A2) is out of the above range, there is a concern that the surface protective film in the embodiment of the present invention cannot have an appropriate softness, that positional displacement and wrinkles of the surface protective film are likely to occur, and that it becomes difficult to follow the three-dimensional curved shape of the mold.

Any suitable vinyl resin may be used as the vinyl resin that can be contained in the base layer (A2) within a range that does not impair the effects of the present invention. Examples of such ethylene resins include at least one selected from Low Density Polyethylene (LDPE), linear Low Density Polyethylene (LLDPE), ultra low density polyethylene (LLDPE), medium Density Polyethylene (MDPE), high Density Polyethylene (HDPE), ultra high density polyethylene, and copolymers of ethylene and other monomers (for example, ethylene/vinyl acetate copolymer, ethylene/acrylic acid copolymer, ethylene/methacrylic acid copolymer, ethylene/acrylic acid ester copolymer, ethylene/methacrylic acid ester copolymer, ethylene/butene-1 copolymer, ethylene/propylene/butene-1 copolymer, ethylene/alpha-olefin copolymer having 5 to 12 carbon atoms, ethylene/nonconjugated diene copolymer, and the like), and at least 1 selected from low density polyethylene and ethylene-vinyl acetate copolymer is preferable.

The ethylene resin that can be contained in the base layer (A2) may be a ziegler-natta ethylene resin obtained using a ziegler-natta catalyst.

The vinyl resin that can be contained in the base layer (A2) may be a metallocene vinyl resin obtained by using a metallocene catalyst. Examples of such metallocene-based vinyl resins include at least 1 selected from the group consisting of metallocene-based low-density polyethylene and metallocene-based ethylene/vinyl acetate copolymers.

As the vinyl resin, a commercially available product can be used.

The 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 base material layer (A2) may contain any appropriate additive as required. Examples of the additive that can be contained in the base layer (A2) include a release agent, an ultraviolet absorber, a heat-resistant stabilizer, a filler, a lubricant, a colorant (dye, etc.), an antioxidant, a die build-up inhibitor, an antiblocking agent, a foaming agent, and polyethyleneimine. These may be 1 kind or 2 or more kinds. The content ratio of the additive in the base material layer (A2) is preferably 10% by weight or less, more preferably 7% by weight or less, further preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

Examples of the release agent include fatty acid amide release agents, silicone release agents, fluorine release agents, and long-chain alkyl release agents. From the viewpoint of enabling formation of a release layer having a more excellent balance between releasability and staining caused by bleeding, a fatty acid amide-based release agent is preferred, and a saturated fatty acid bisamide is more preferred. The release agent may be present in any suitable amount. Typically, the resin component (preferably, vinyl resin) in the base material layer (A2) is preferably 0.01 to 5 wt%.

Examples of the ultraviolet absorber include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. The ultraviolet absorber may be used in any suitable amount as long as it does not bleed out during molding. Typically, the resin component (preferably, vinyl resin) in the base material layer (A2) is preferably 0.01 to 5 wt%.

Examples of the heat-resistant stabilizer include hindered amine compounds, phosphorus compounds, and cyanoacrylate compounds. As for the content of the heat-resistant stabilizer, any suitable content may be used as long as it does not bleed out at the time of molding. Typically, the resin component (preferably, vinyl resin) in the base material layer (A2) is preferably 0.01 to 5 wt%.

Examples of the filler include inorganic fillers such as talc, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, silica, clay, mica, barium sulfate, whiskers, and magnesium hydroxide. The average particle diameter of the filler is preferably 0.1 μm to 20. Mu.m. The filler may be present in any suitable amount. Typically, the resin component (preferably, vinyl resin) in the base material layer (A2) is preferably 1 to 200 wt%.

[ 1-1-2-2. Substrate layer (A2) preferred embodiment 2 ]

In one preferred embodiment 2 of the base material layer (A2), the base material layer (A2) preferably contains an acryl-based resin. The effect of the present invention can be further exhibited by including the propylene resin in the base material layer (A2). In particular, by including the acrylic resin in the base material layer (A2), the surface protective film according to the embodiment of the present invention has appropriate softness and heat resistance, and can realize excellent three-dimensional curved surface processing when used for hot pressing of a resin substrate.

The content ratio of the propylene resin that can be contained in the base material layer (A2) is preferably 50 to 100 wt%, more preferably 70 to 100 wt%, even more preferably 90 to 100 wt%, particularly preferably 95 to 100 wt%, and most preferably substantially 100 wt%. When the content ratio of the propylene resin in the base material layer (A2) falls within the above range, the effect of the present invention can be further exhibited. In particular, when the content ratio of the propylene resin in the base material layer (A2) is within the above range, the surface protective film according to the embodiment of the present invention has appropriate softness and heat resistance, and can realize good three-dimensional curved surface processing when used for hot pressing of a resin substrate. When the content ratio of the propylene resin in the base material layer (A2) is out of the above range, there is a concern that the surface protective film in the embodiment of the present invention cannot have an appropriate softness, there is a concern that positional displacement and wrinkles of the surface protective film are likely to occur, and there is a concern that it becomes difficult to follow the three-dimensional curved shape of the mold.

The propylene resin that can be contained in the base layer (A2) may be any suitable propylene resin as long as the effect of the present invention is not impaired. Examples of such propylene resins include at least 1 selected from the group consisting of random polypropylene, block polypropylene, homo-polypropylene, and copolymers of propylene and other monomers, and homo-polypropylene is preferable in view of further exhibiting the effects of the present invention.

The propylene-based resin that can be contained in the base material layer (A2) may be a ziegler-natta propylene-based resin obtained using a ziegler-natta catalyst.

The propylene resin that can be contained in the base material layer (A2) may be a metallocene propylene resin obtained by using a metallocene catalyst. Examples of such a metallocene-based propylene resin include at least 1 selected from the group consisting of metallocene-based random polypropylene, metallocene-based block polypropylene, metallocene-based homo-polypropylene, and copolymers of metallocene-based propylene and other monomers.

As the propylene resin, commercially available ones can be used.

<1-1-3. Auxiliary base layer (A3) >

The base material layer (a) preferably includes a base material layer (A1), a base material layer (A2), and an auxiliary base material layer (A3) in this order. That is, the auxiliary base material layer (A3) is disposed between the base material layer (A2) and the adhesive layer (B).

The thickness of the auxiliary base material layer (A3) is preferably 2 μm to 60. Mu.m, more preferably 3 μm to 60. Mu.m, still more preferably 5 μm to 55. Mu.m, still more preferably 5 μm to 50. Mu.m, still more preferably 5 μm to 40. Mu.m, particularly preferably 5 μm to 30. Mu.m, and most preferably 5 μm to 20. Mu.m. When the thickness of the auxiliary base material layer (A3) is within the above range, the effect of the present invention can be further exhibited.

The difference between the thickness of the auxiliary base material layer (A3) and the thickness of the base material layer (A1) is preferably ±150% or less, more preferably ±100% or less, further preferably ±50% or less, further preferably ±30% or less, further preferably ±10% or less, particularly preferably ±5% or less, and most preferably substantially 0%. If the error between the thickness of the auxiliary base material layer (A3) and the thickness of the base material layer (A1) falls within the above-described range, the laminated structure of the base material layers in the surface protective film according to the embodiment of the present invention becomes close to up-down symmetry, and therefore curling of the surface protective film can be suppressed. Particularly, when the surface protective film according to the embodiment of the present invention is used for hot pressing of a resin substrate, curling due to thermal history can be effectively suppressed.

The auxiliary base material layer (A3) may be formed of only 1 layer or 2 or more layers. When the auxiliary base material layer (A3) is 2 or more layers, each layer may be formed of the same composition or may be at least 1 layer different from each other.

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

The auxiliary base material layer (A3) may contain any suitable resin within a range that does not impair the effects of the present invention. The resin of the main component contained in the auxiliary base material layer (A3) is preferably the same as the resin of the main component contained in the base material layer (A1). If the resin of the main component contained in the auxiliary base material layer (A3) is the same as the resin of the main component contained in the base material layer (A1), the composition distribution of the base material layer in the surface protective film according to the embodiment of the present invention becomes close to up-down symmetry, and therefore curling of the surface protective film can be suppressed. Particularly, when the surface protective film according to the embodiment of the present invention is used for hot pressing of a resin substrate, curling due to thermal history can be effectively suppressed. The term "main component" as used herein means that the content ratio of the whole is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, still more preferably 90 to 100% by weight, particularly preferably 95 to 100% by weight, and most preferably substantially 100% by weight.

The auxiliary base material layer (A3) may contain any suitable resin within a range that does not impair the effects of the present invention. The auxiliary base material layer (A3) contains at least 1 selected from the group consisting of vinyl resins, propylene resins, butene resins and pentene resins. The effect of the present invention can be further exhibited by including at least 1 selected from the group consisting of vinyl resins, propylene resins, butene resins, and pentene resins in the auxiliary base material layer (A3). In particular, the effect of the present invention can be further exhibited by the fact that the outermost surface of the auxiliary base material layer (A3) is excellent in heat resistance by including at least 1 selected from the group consisting of vinyl resins, propylene resins, butene resins and pentene resins in the auxiliary base material layer (A3). When the auxiliary base material layer (A3) does not contain at least 1 selected from the group consisting of vinyl resins, acrylic resins, butene resins, and pentene resins, there is a concern that the heat resistance of the outermost surface of the base material layer (a) is poor, and when the surface protective film according to the embodiment of the present invention is used for hot pressing of a resin substrate, there is a concern that adhesion of the surface protective film to a mold due to melting or the like is likely to occur, and there is a concern that positional displacement and wrinkles of the surface protective film are likely to occur due to pressing at high temperature.

The content ratio of at least one selected from the group consisting of vinyl resins, propylene resins, butene resins, and pentene resins 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, particularly preferably 95 to 100% by weight, and most preferably substantially 100% by weight. The auxiliary base layer (A3) can further exhibit the effect of the present invention if the content ratio of at least 1 selected from the group consisting of vinyl resins, propylene resins, butene resins and pentene resins falls within the above-described range. In particular, when the content ratio of at least 1 selected from the group consisting of the vinyl resin, the propylene resin, the butene resin and the pentene resin in the auxiliary base layer (A3) falls within the above range, the outermost surface of the base layer (a) can be excellent in heat resistance, and therefore the effect of the present invention can be further exhibited. When the content ratio of at least 1 selected from the group consisting of the vinyl resin, the propylene resin, the butene resin, and the pentene resin in the auxiliary base material layer (A3) is out of the above range, there is a concern that the heat resistance of the outermost surface of the base material layer (a) is poor, and when the surface protective film in the embodiment of the present invention is used for hot pressing of a resin substrate, there is a concern that adhesion of the surface protective film to a mold due to melting or the like is likely to occur, and there is a concern that positional displacement and wrinkles of the surface protective film are likely to occur due to pressing at high temperature.

Any suitable vinyl resin may be used as the vinyl resin that can be contained in the auxiliary base material layer (A3) within a range that does not impair the effects of the present invention. Examples of such an ethylene resin include at least one selected from 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 (for example, ethylene/vinyl acetate copolymer, ethylene/acrylic acid copolymer, ethylene/methacrylic acid copolymer, ethylene/acrylic acid ester copolymer, ethylene/methacrylic acid ester copolymer, ethylene/butene-1 copolymer, ethylene/propylene/butene-1 copolymer, ethylene/alpha-olefin copolymer having 5 to 12 carbon atoms, ethylene/nonconjugated diene copolymer, and the like), and at least 1 selected from high density polyethylene, low density polyethylene, and ethylene/vinyl acetate copolymer, and more preferably high density polyethylene.

The ethylene resin that can be contained in the auxiliary base material layer (A3) may be a ziegler-natta ethylene resin obtained using a ziegler-natta catalyst.

The vinyl resin that can be contained in the auxiliary base material layer (A3) may be a metallocene vinyl resin obtained by using a metallocene catalyst. Examples of such metallocene-based vinyl resins include at least 1 selected from the group consisting of metallocene-based low-density polyethylene and metallocene-based ethylene/vinyl acetate copolymers.

The vinyl resin that can be contained in the auxiliary base material layer (A3) may be 1 or 2 or more.

The vinyl resin that can be contained in the auxiliary base material layer (A3) may be a commercially available resin.

The propylene resin that can be contained in the auxiliary base material layer (A3) may be any suitable propylene resin as long as the effect of the present invention is not impaired. Examples of such propylene resins include at least 1 selected from the group consisting of random polypropylene, block polypropylene, homo-polypropylene, and copolymers of propylene and other monomers.

The propylene resin that can be contained in the auxiliary base material layer (A3) may be 1 or 2 or more.

As the copolymer of propylene and other monomers, any suitable copolymer may be used within a range that does not impair the effects of the present invention. Examples of such a copolymer of propylene and another monomer include a propylene/ethylene copolymer, a propylene/ethylene/1-butene copolymer, and a propylene/C5-12 alpha-olefin copolymer.

The propylene-based resin that can be contained in the auxiliary substrate layer (A3) may be a ziegler-natta propylene-based resin obtained using a ziegler-natta catalyst.

The propylene-based resin that can be contained in the auxiliary substrate layer (A3) may be a metallocene propylene-based resin obtained using a metallocene catalyst. Examples of such a metallocene-based propylene resin include at least 1 selected from the group consisting of metallocene-based random polypropylene, metallocene-based block polypropylene, metallocene-based homo-polypropylene, and copolymers of metallocene-based propylene and other monomers.

The propylene resin that can be contained in the auxiliary base material layer (A3) may be commercially available ones.

The pentene-based resin that can be contained in the auxiliary base material layer (A3) may be any suitable pentene-based resin as long as the effect of the present invention is not impaired. Examples of such a pentene-based resin include at least 1 selected from the group consisting of poly (4-methylpentene-1), copolymers of 4-methylpentene-1 and other monomers, poly (3-methylpentene-1), and copolymers of 3-methylpentene-1 and other monomers. From the viewpoint of further exhibiting the effect of the present invention, at least 1 selected from the group consisting of poly (4-methylpentene-1) and copolymers of 4-methylpentene-1 and other monomers is exemplified as the pentene-based resin, and a trade name "TPX (registered trademark)" manufactured by mitsunobu chemical company, which is a crystalline pentene-based resin using 4-methylpentene-1 as a main raw material, is typically exemplified.

The pentene-based resin that can be contained in the auxiliary base material layer (A3) may be a ziegler-natta-based pentene-based resin obtained using a ziegler-natta catalyst.

The pentene-based resin that can be contained in the auxiliary base material layer (A3) may be a metallocene-based pentene-based resin obtained using a metallocene catalyst.

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 required. Examples of the additive that can be contained in the auxiliary base material layer (A3) include a release agent, an ultraviolet absorber, a heat-resistant stabilizer, a filler, a lubricant, a colorant (dye, etc.), an antioxidant, a die build-up inhibitor, an antiblocking agent, a foaming agent, and polyethyleneimine. These may be 1 kind or 2 or more kinds. The content ratio of the additive in the auxiliary base material layer (A3) is preferably 10% by weight or less, more preferably 7% by weight or less, further preferably 5% by weight or less, particularly preferably 2% by weight or less, and most preferably 1% by weight or less.

Examples of the release agent include fatty acid amide release agents, silicone release agents, fluorine release agents, and long-chain alkyl release agents. From the viewpoint of enabling formation of a release layer having a more excellent balance between releasability and staining caused by bleeding, a fatty acid amide-based release agent is preferred, and a saturated fatty acid bisamide is more preferred. The release agent may be present in any suitable amount. Typically, the resin component (preferably, propylene resin) in the auxiliary base material layer (A3) is preferably 0.01 to 5 wt%.

Examples of the ultraviolet absorber include benzotriazole-based compounds, benzophenone-based compounds, and benzoate-based compounds. The ultraviolet absorber may be used in any suitable amount as long as it does not bleed out during molding. Typically, the resin component (preferably, propylene resin) in the auxiliary base material layer (A3) is preferably 0.01 to 5 wt%.

Examples of the heat-resistant stabilizer include hindered amine compounds, phosphorus compounds, and cyanoacrylate compounds. As for the content of the heat-resistant stabilizer, any suitable content may be used as long as it does not bleed out at the time of molding. Typically, the resin component (preferably, propylene resin) in the auxiliary base material layer (A3) is preferably 0.01 to 5 wt%.

Examples of the filler include inorganic fillers such as talc, titanium oxide, calcium oxide, magnesium oxide, zinc oxide, titanium oxide, calcium carbonate, silica, clay, mica, barium sulfate, whiskers, and magnesium hydroxide. The average particle diameter of the filler is preferably 0.1 μm to 20. Mu.m. The filler may be present in any suitable amount. Typically, the resin component (preferably, propylene resin) in the auxiliary base material layer (A3) is preferably 1 to 200 wt%.

1-2 adhesive layer (B)

The thickness of the pressure-sensitive adhesive layer (B) is preferably 5 μm to 50. Mu.m, more preferably 5 μm to 40. Mu.m, still more preferably 5 μm to 30. Mu.m, particularly preferably 5 μm to 20. Mu.m. The thickness of the adhesive layer (B) can further exhibit the effect of the present invention if it is within the above range. If the thickness of the adhesive layer (B) is too small, the adhesive effect may not be sufficiently exhibited. If the thickness of the adhesive layer (B) is too thick, the surface protective film becomes too thick, and therefore, it may become difficult to follow the three-dimensional curved shape of the mold.

The adhesive layer (B) may be formed of only 1 layer or 2 or more layers. When the pressure-sensitive adhesive layer (B) is 2 or more layers, each layer may be formed of the same composition or may be at least 1 layer different from the other layers.

The adhesive layer (B) may be an adhesive layer formed of any suitable adhesive. Examples of such a binder include thermoplastic resin-based binders containing a base polymer containing a thermoplastic resin as a main component (preferably 50 to 100 wt%, more preferably 70 to 100 wt%, still more preferably 80 to 100 wt%, particularly preferably 90 to 100 wt%, and most preferably 95 to 100 wt%). The thermoplastic resin that may be contained in the base polymer may be 1 or 2 or more.

As the thermoplastic resin, any suitable thermoplastic resin may be used. Examples of the thermoplastic resin include at least 1 selected from the group consisting of styrene resins, olefin resins, aromatic group-containing olefin/diene copolymers, ester resins, acrylic resins, and rubber resins. Among these thermoplastic resins, at least 1 selected from the group consisting of styrene-based resins and olefin-based resins is preferable.

The styrene-based resin is preferably a styrene-based elastomer.

The olefinic resin is preferably an olefinic elastomer.

By using at least 1 selected from the group consisting of styrene-based resins and olefin-based resins as the thermoplastic resin, good adhesion after storage with time, low contamination after peeling, and the like can be uniformly exhibited.

The styrene-based elastomer may preferably be a hydrogenated styrene/butadiene rubber (HSBR), a styrene-based block copolymer or a hydrogenated product thereof.

Examples of the hydrogenated styrene/butadiene rubber (HSBR) include JSR, dynaron1320P, 1321P, 2324P, and the like.

Examples of the styrenic block copolymer include: styrene ABA-based block copolymers (triblock copolymers) such as styrene/butadiene/styrene copolymers (SBS) and styrene/isoprene/styrene copolymers (SIS); styrene-based ABAB-type block copolymers (tetrablock copolymers) such as styrene/butadiene/styrene/butadiene copolymers (SBSB) and styrene/isoprene/styrene/isoprene copolymers (SISI); styrene-based ABABA-type block copolymers (pentablock copolymers) such as styrene/butadiene/styrene copolymer (sbsbsbs), styrene/isoprene/styrene copolymer (sis); a styrenic block copolymer having an AB repeating unit above that; etc.

Examples of the hydrogenated product of the styrene block copolymer include styrene/ethylene-butene copolymer/styrene copolymer (SEBS), styrene/ethylene-propylene copolymer/styrene copolymer (SEPS), and styrene/ethylene-butene copolymer/styrene/ethylene-butene copolymer (sebeb).

The styrene thermoplastic elastomer is particularly preferably a styrene/ethylene-butene copolymer/styrene copolymer (SEBS). By using a styrene/ethylene-butylene copolymer/styrene copolymer (SEBS) as the styrene-based elastomer, good adhesion after storage with time, low contamination after peeling, and the like can be uniformly exhibited.

Examples of the styrene/ethylene-butene copolymer/styrene copolymer (SEBS) include JSR, dynaron 8601P, 9901P, and the like.

The styrene-based elastomer may be used in an amount of 1 or 2 or more.

The styrene content (styrene block content in the case of a styrene block copolymer) in the styrene-based elastomer is preferably 1 to 40% by weight, more preferably 5 to 40% by weight, further preferably 7 to 30% by weight, further preferably 9 to 20% by weight, particularly preferably 9 to 15% by weight, and most preferably 9 to 13% by weight. The above-mentioned styrene content becomes small, and there is a concern that the residual glue is liable to occur due to insufficient cohesive force of the adhesive layer. When the styrene content is increased, the pressure-sensitive adhesive layer becomes hard, and there is a concern that good adhesion to the roughened surface cannot be obtained. When the styrene block content is within the above range, good adhesion after storage with time, low contamination after peeling, and the like can be uniformly exhibited.

The styrene-based elastomer is preferably a hydrogenated product (SEBS, SEBSEB, SEBSEBS, etc.) of a styrene-based block copolymer having a repeating structure (ABA type, ABAB type, ABABA type, etc.) of a triblock copolymer composed of styrene (a) and butadiene (B). By using such a styrene-based elastomer, it is possible to exhibit good adhesion with good balance, good adhesion after storage with time, low contamination after peeling, and the like.

When the styrene-based elastomer is a hydrogenated product (SEBS, SEBSEB, SEBSEBS, etc.) of a styrene-based block copolymer having a repeating structure (ABA type, ABAB type, ABABA type, etc.) of a triblock copolymer composed of styrene (a) and butadiene (B), the ratio of the butene structure to the ethylene-butene copolymer block is preferably 60% by weight or more, more preferably 70% by weight or more, still more preferably 75% by weight or more. When the ratio of the butene structure to the ethylene-butene copolymer block is within the above range, good adhesion after storage with time, low contamination after peeling, and the like can be exhibited with good balance. The ratio of the butene structure to the ethylene-butene copolymer block is preferably 90% by weight or less.

For the purpose of adjusting the adhesiveness and the like, the base polymer may contain other styrene-based elastomers within a range not impairing the object of the present invention.

The other styrene-based elastomer may be: a styrenic block copolymer other than the above; AB-type block polymers such as styrene/butadiene copolymer (SB), styrene/isoprene copolymer (SI), styrene/ethylene-butene copolymer (SEB), and styrene/ethylene-propylene copolymer (SEP); styrene random copolymers such as styrene/butadiene rubber (SBR); a-B-C type styrene/olefin crystalline block polymer such as styrene/ethylene-butene copolymer/olefin crystalline copolymer (SEBC); their hydrides; etc.

The olefin elastomer is preferably an amorphous polyolefin elastomer.

Examples of the amorphous polyolefin elastomer include ethylene propylene rubber, an elastomer composed of ethylene and an α -olefin, and an amorphous polypropylene resin (atactic polypropylene, etc.) exhibiting adhesiveness. Amorphous polypropylene resins are preferably used. The amorphous polypropylene resin may be any suitable amorphous polypropylene resin as long as it has rubber elasticity in a use temperature range.

Here, the amorphous polyolefin elastomer has an amorphous property without containing a crystal structure. Examples of the method for confirming the non-crystallinity include a solubility test in n-heptane. Specifically, the solubility of the amorphous polyolefin elastomer was measured by dissolving the elastomer in n-heptane at a concentration of 10 wt%, and when the solubility was found to be 100% in this case, the solubility was found to be 90% or more.

Examples of the amorphous polypropylene resin include propylene- α -olefin copolymer and propylene-ethylene- α -olefin copolymer.

Examples of the α -olefin include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, and 4-methyl-1-hexene. Of these, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene are preferable. The number of α -olefins may be 1 or 2 or more.

The amorphous polypropylene resin is preferably an amorphous propylene- (1-butene) copolymer. The amorphous propylene- (1-butene) copolymer can be preferably obtained by copolymerizing propylene with 1-butene using a metallocene catalyst. The amorphous propylene- (1-butene) copolymer obtained by copolymerization using a metallocene catalyst exhibits a narrow molecular weight distribution (e.g., 2 or less). If such an amorphous propylene- (1-butene) copolymer exhibiting a narrow molecular weight distribution is used, exudation of low molecular weight components can be prevented.

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

The content of the 1-butene-derived structural unit in the amorphous propylene- (1-butene) copolymer is preferably 1 to 15 mol%, more preferably 1 to 10 mol%. When the content of the 1-butene-derived structural unit in the amorphous propylene- (1-butene) copolymer is in such a range, an adhesive layer having an excellent balance between toughness and flexibility can be obtained, and the effect of the present invention can be more effectively exhibited.

As the copolymerization structure of the amorphous propylene- (1-butene) copolymer, any suitable copolymerization structure may be employed. Examples of such a copolymerization structure include a block copolymer and a random copolymer.

The weight average molecular weight (Mw) of the amorphous propylene- (1-butene) copolymer is preferably 200000 or more, more preferably 200000 ～ 500000, and still more preferably 200000 ～ 300000. When the weight average molecular weight (Mw) of the amorphous propylene- (1-butene) copolymer is in such a range, an adhesive layer having an appropriate adhesive force can be obtained, and the effect of the present invention can be more effectively exhibited.

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

Examples of the pressure-sensitive adhesive layer (B) include an acrylic pressure-sensitive adhesive containing a base polymer containing an acrylic resin as a main component (preferably 50 to 100 wt%, more preferably 70 to 100 wt%, still more preferably 80 to 100 wt%, particularly preferably 90 to 100 wt%, and most preferably 95 to 100 wt%). The acrylic resin that may be contained in the base polymer may be 1 or 2 or more.

Any suitable acrylic resin may be used as the acrylic resin within a range that does not impair the effects of the present invention. Such an acrylic resin is preferably obtained by polymerization of the monomer component (m).

The monomer component (m) may be any suitable monomer component within a range that does not impair the effects of the present invention.

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 1 or 2 or more.

Specific examples of the alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms at the ester end include: alkyl (meth) acrylates having a linear alkyl group having 4 to 18 carbon atoms at the ester end, such as n-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, n-nonyl (meth) acrylate, n-decyl (meth) acrylate, n-undecyl (meth) acrylate, 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; t-butyl (meth) acrylate, isobutyl (meth) acrylate, isopentyl (meth) acrylate, t-amyl (meth) acrylate, neopentyl (meth) acrylate, isohexyl (meth) acrylate, isoheptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, isodecyl (meth) acrylate, 2-propylheptyl (meth) acrylate, isoundecyl (meth) acrylate, isododecyl (meth) acrylate, isotridecyl (meth) acrylate, isomyristyl (meth) acrylate, isopentadecyl (meth) acrylate, isohexadecyl (meth) acrylate, isoheptadecyl (meth) acrylate, isostearyl (meth) acrylate, and the like having a branched alkyl group having 4 to 18 carbon atoms at the ester end; etc. 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 preferable, alkyl (meth) acrylates having a linear alkyl group having 4 to 8 carbon atoms at the ester end are more preferable, and specifically, n-butyl (meth) acrylate is particularly preferable.

The content ratio 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 to 100% by weight, more preferably 70 to 99.5% by weight, still more preferably 90 to 99% by weight, particularly preferably 91 to 98% by weight, and most preferably 92 to 97% by weight.

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

The monomer component (m) may contain other monomers. Such other monomers may be 1 or 2 or more.

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

Examples of the other monomer include an alicyclic structure-containing acrylic monomer, an alkyl (meth) acrylate having an alkyl group having 1 to 3 carbon atoms at the ester end, a hydroxyl group-containing monomer, a carboxyl group-containing monomer other than (meth) acrylic acid, a nitrogen-containing cyclic structure-containing monomer, a cyclic ether group-containing monomer, a diol-based acrylate monomer, a styrene-based monomer, an amide group-containing monomer, an amino group-containing monomer, an imide group-containing monomer, a vinyl ether monomer, a silane-based monomer, and a polyfunctional monomer.

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

Specific examples of the alkyl (meth) acrylate 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, and isopropyl (meth) acrylate.

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

Examples of the carboxyl group-containing monomer other than (meth) acrylic acid include carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

Specific examples of the monomer having a nitrogen-containing ring structure include: lactam vinyl monomers such as N-vinylpyrrolidone, N-vinyl-epsilon-caprolactam and methyl vinylpyrrolidone; vinyl monomers having nitrogen-containing heterocyclic rings such as vinylpyridine, vinylpiperidone, vinylpyridine, vinylpiperazine, vinylpyrzine, vinylpyrrole, vinylimidazole, vinyloxazole, and vinylmorpholine; (meth) acryl monomers containing a heterocyclic ring such as morpholine ring, piperidine ring, pyrrolidine ring, piperazine ring (for example, N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine, etc.); etc.

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

Specific examples of the glycol-based acrylate monomer include polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate.

Specific examples of the styrene monomer include styrene and α -methylstyrene.

Specific examples of the amide group-containing monomer include: acrylamide, methacrylamide, diethylacrylamide, N-vinylpyrrolidone, N-dimethylacrylamide, N-diethylacrylamide, N, N-diethyl methacrylamide, N' -methylenebisacrylamide, N-dimethylaminopropyl acrylamide, N-dimethylaminopropyl methacrylamide, diacetone acrylamide, N-hydroxyethyl acrylamide, and the like.

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

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

Specific examples of the silane monomer include: 3-acryloxypropyl triethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyl trimethoxysilane, 4-vinylbutyl triethoxysilane, 8-vinyloctyl trimethoxysilane, 8-vinyloctyl triethoxysilane, 10-methacryloxydecyl trimethoxysilane, 10-acryloxydecyl trimethoxysilane, 10-methacryloxydecyl triethoxysilane, 10-acryloxydecyl triethoxysilane, and the like.

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

The acrylic resin can be obtained by polymerization of the monomer component (m).

As a method for producing the acrylic resin, any suitable production method may be employed within a range that does not impair the effects of the present invention. Examples of such a production method include various radical polymerization such as solution polymerization, active energy ray polymerization such as UV polymerization, bulk polymerization, and emulsion polymerization. As the polymerization conditions, any suitable polymerization conditions may be employed within a range that does not impair the effects of the present invention.

Any suitable polymerization structure may be used as the polymerization structure of the obtained acrylic resin within a range that does not impair the effects of the present invention. Examples of such a polymer structure include random copolymers, block copolymers, and graft copolymers.

As the additive for the radical polymerization, such as a polymerization initiator, a chain transfer agent, and an emulsifier, any suitable additive may be used within a range that does not impair the effects of the present invention.

Examples of the polymerization solvent that can be used for solution polymerization include ethyl acetate and toluene. The polymerization solvent may be 1 or 2 or more.

The solution polymerization is usually carried out under a reaction condition of about 50 to 70℃and about 5 to 30 hours by adding a polymerization initiator under an inert gas flow such as nitrogen.

As the polymerization initiator that can be used for solution polymerization or the like, any suitable thermal polymerization initiator can be used within a range that does not impair the effects of the present invention. The polymerization initiator may be 1 or 2 or more. Examples of such a polymerization initiator include: 2,2 '-azobisisobutyronitrile, 2' -azobis-2-methylbutyronitrile, dimethyl 2,2 '-azobis (2-methylpropionate), 4' -azobis-4-cyanovaleric acid, azobisisovaleronitrile 2,2 '-azobis (2-amidinopropane) dihydrochloride, 2' -azobis [2- (5-methyl-2-imidazolin-2-yl) propane ] dihydrochloride, 2 '-azobis (2-methylpropionamidine) disulfate, 2' -azobis (N, azo initiators such as N '-dimethylene isobutyl amidine) and 2,2' -azobis [ N- (2-carboxyethyl) -2-methylpropionamidine ] hydrate (VA-057, manufactured by Wako pure chemical industries, ltd.); peroxide-based initiators such as potassium persulfate, persulfate such as ammonium persulfate, bis (2-ethylhexyl) peroxydicarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1, 3-tetramethylbutyl peroxide, bis (4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1-bis (t-hexylperoxy) cyclohexane, t-butyl hydroperoxide, hydrogen peroxide, and the like; redox initiators comprising a combination of a persulfate and sodium bisulfite, a combination of a peroxide and sodium ascorbate, and a combination of a peroxide and a reducing agent; etc.

The amount of the polymerization initiator used is preferably 1 part by weight or less, more preferably 0.005 to 1 part by weight, still more preferably 0.01 to 0.7 part by weight, particularly preferably 0.02 to 0.5 part by weight, based on 100 parts by weight of the total amount of the monomer component (m), from the viewpoint that the polymerization reaction can be efficiently performed.

Any suitable chain transfer agent may be used as long as the effect of the present invention is not impaired. The chain transfer agent may be 1 or 2 or more. Examples of such chain transfer agents include lauryl mercaptan, glycidyl mercaptan, thioglycolic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2, 3-dimercapto-1-propanol.

The amount of the chain transfer agent used is preferably 0.1 part by weight or less based on 100 parts by weight of the total amount of the monomer component (m) in order to effectively carry out polymerization reaction or the like.

As the emulsifier, any suitable emulsifier may be used within a range that does not impair the effects of the present invention. The number of the emulsifying agents may be 1 or 2 or more. Examples of such emulsifiers include: anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, ammonium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, and the like; nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene-polyoxypropylene block polymer, and the like; etc.

The amount of the emulsifier used is preferably 5 parts by weight or less, more preferably 0.3 to 5 parts by weight, still more preferably 0.4 to 3 parts by weight, particularly preferably 0.5 to 1 part by weight, based on 100 parts by weight of the total amount of the monomer component (m) from the viewpoints of polymerization stability and mechanical stability.

In the case of performing UV polymerization, a photopolymerization initiator is preferably used.

As the photopolymerization initiator, any appropriate photopolymerization initiator may be used within a range that does not impair the effects of the present invention. The photopolymerization initiator may be 1 or 2 or more. Examples of such photopolymerization initiators include: benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α -ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactive oxime photopolymerization initiator, benzoin photopolymerization initiator, benzil photopolymerization initiator, benzophenone photopolymerization initiator, ketal photopolymerization initiator, thioxanthone photopolymerization initiator, and acylphosphine oxide photopolymerization initiator.

Specific examples of the benzoin ether photopolymerization initiator include: benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-dimethoxy-1, 2-diphenylethane-1-one (commercially available as, for example, trade name "Irgacure 651", manufactured by BASF corporation), anisoin methyl ether, and the like.

Specific examples of the acetophenone photopolymerization initiator include: 1-hydroxycyclohexyl phenyl ketone (as a commercial product, for example, trade name "Irgacure 184", manufactured by BASF corporation), 4-phenoxydichloroacetophenone, 4-tert-butyl-dichloroacetophenone, 1- [4- (2-hydroxyethoxy) -phenyl ] -2-hydroxy-2-methyl-1-propan-1-one (as a commercial product, for example, trade name "Irgacure 2959", manufactured by BASF corporation), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (as a commercial product, for example, trade name "Darocure1173", manufactured by BASF corporation), methoxyacetophenone, and the like.

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

Specific examples of the aromatic sulfonyl chloride-based photopolymerization initiator include 2-naphthalenesulfonyl chloride.

Specific examples of the photo-active oxime-based photopolymerization initiator include 1-phenyl-1, 1-propanedione-2- (O-ethoxycarbonyl) -oxime.

Specific examples of the benzoin photopolymerization initiator include benzoin.

Specific examples of the benzil photopolymerization initiator include benzil.

Specific examples of the benzophenone photopolymerization initiator include benzophenone, benzoyl benzoic acid, 3' -dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α -hydroxycyclohexyl phenyl ketone.

Specific examples of the ketal photopolymerization initiator include benzildimethyl ketal.

Specific examples of the thioxanthone photopolymerization initiator include: thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2, 4-dimethylthioxanthone, isopropylthioxanthone, 2, 4-dichlorothioxanthone, 2, 4-diethylthioxanthone, isopropylthioxanthone, 2, 4-diisopropylthioxanthone, dodecylthioxanthone, and the like.

Specific examples of the acylphosphine photopolymerization initiator include: bis (2, 6-dimethoxybenzoyl) phenylphosphine oxide, bis (2, 6-dimethoxybenzoyl) (2, 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-dibutoxybenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2, 4-dimethoxybenzoyl) (2-methylpropan-1-yl) phosphine oxide, bis (2, 4, 6-trimethylbenzoyl) (2, 4-dimethoxybenzoyl) phosphine oxide, bis (2, 6-dimethoxybenzoyl) benzyl phosphine oxide, bis (2, 6-dimethoxybenzoyl) -2-phenylpropyl phosphine oxide, bis (2, 6-dimethoxybenzoyl) -2-phenylethylphosphine oxide, 2, 6-dimethoxybenzoyl-butyl phosphine oxide, 2, 6-dimethoxybenzoyl-octyl phosphine oxide, bis (2, 4, 6-trimethylbenzoyl) -2, 5-diisopropylphenyl phosphine oxide, bis (2, 4, 6-trimethylbenzoyl) -2-methylphenyl phosphine oxide, bis (2, 4, 6-trimethylbenzoyl) -4-methylphenyl phosphine oxide, bis (2, 4, 6-trimethylbenzoyl) -2-dimethylbenzene phosphine oxide, bis (2, 6-dimethoxybenzoyl) -2-phenylphosphine oxide, 2, 6-dimethoxybenzoyl-2-dimethylbenzyl phosphine oxide, bis (2, 6-dimethoxybenzoyl) -2-dimethylbenzyl phosphine oxide, 2, 4-dimethoxybenzoyl-2-isopropylphosphine oxide, bis (2, 6-dimethoxybenzoyl) -2, 5-diisopropylphosphine oxide, bis (2, 4, 6-trimethylbenzoyl) -2-diisopropylphosphine oxide, bis (2, 6-trimethylbenzoyl) -2-diisopropylphosphine oxide, 4-trimethylbenzoyl-2-4-trimethylphosphine 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, tris (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 to 5 parts by weight, still more preferably 0.05 to 3 parts by weight, particularly preferably 0.05 to 1.5 parts by weight, and most preferably 0.1 to 1 part by weight, based on 100 parts by weight of the total amount of the monomer component (m), from the viewpoint of exhibiting good polymerizability.

In the case of carrying out the UV polymerization, a polyfunctional (meth) acrylate is preferably used.

As the polyfunctional (meth) acrylate, any suitable polyfunctional (meth) acrylate may be used within a range that does not impair the effects of the present invention. The number of the polyfunctional (meth) acrylates may be 1 or 2 or more. Specific examples of such a polyfunctional (meth) acrylate include: ester compounds of polyhydric alcohols such as (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1, 2-ethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 12-dodecanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and tetramethylolmethane tri (meth) acrylate with (meth) acrylic acid; allyl (meth) acrylate; vinyl (meth) acrylate; divinylbenzene; epoxy acrylate; a polyester acrylate; a urethane acrylate; butyl di (meth) acrylate; hexyl di (meth) acrylate; etc.

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

As for the UV polymerization method, any suitable UV polymerization method may be employed within a range that does not impair the effects of the present invention. As such a UV polymerization method, for example, a photopolymerization initiator, and if necessary, a polyfunctional (meth) acrylate are blended into the monomer component (m) and irradiated with ultraviolet rays.

The weight average molecular weight of the acrylic resin is preferably 10 to 300, more preferably 30 to 200, still more preferably 50 to 150, particularly preferably 50 to 100. The weight average molecular weight is a value calculated by conversion to polystyrene, measured by Gel Permeation Chromatography (GPC). In the acrylic resin obtained by active energy ray polymerization, it may be difficult to measure the weight average molecular weight.

The adhesive layer (B) may contain any appropriate other component as required. Examples of the other components include: a tackifier; a softening agent; an anti-aging agent; a polyolefin resin; a silicone resin; a liquid acrylic copolymer; a polyethyleneimine; fatty acid amides; a phosphate ester; light stabilizers such as hindered amine light stabilizers; an ultraviolet absorber; a heat-resistant stabilizer; fillers or pigments such as calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide; a cross-linking agent; a surface lubricant, a leveling agent; a plasticizer; a low molecular polymer; an antioxidant; an anti-corrosion agent; polymerization inhibitor; a silane coupling agent; a conductive agent; metal powder; a colorant; a foil; a lubricant; a solvent; a catalyst; other additives; etc. The kind and amount of other components that may be contained in the adhesive layer may be appropriately set according to the purpose.

The surface of the adhesive layer (B) may be subjected to surface treatments for the purpose of controlling adhesion, attaching workability, and the like, such as corona discharge treatment, ultraviolet irradiation treatment, flame treatment, plasma treatment, sputter etching treatment, and the like, as needed.

The adhesive layer (B) preferably contains a tackifier. By including the tackifier in the adhesive layer (B), the adhesive force can be improved. Among them, in order to avoid the problem of residual glue caused by occurrence of a decrease in cohesion, the compounding amount of the tackifier is appropriately determined according to the adherend to which the surface protective sheet is to be applied. The blending 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 with respect to the base polymer of the adhesive layer (B).

Examples of the tackifier include, but not particularly limited to, petroleum resins such as aliphatic copolymers, aromatic copolymers, aliphatic/aromatic copolymers and alicyclic copolymers, coumarone-indene resins, terpene phenolic resins, rosin resins such as polymerized rosin, (alkyl) phenolic resins, xylene resins, and hydrogenated products thereof, which are generally used in adhesives. The tackifier may be used in an amount of 1 or 2 or more. Among these tackifiers, hydrogenated tackifiers are preferred from the viewpoints of releasability, weather resistance, and the like. The tackifier may be a commercially available tackifier in the form of a blend with an olefin resin.

The softening point of the tackifier is preferably 100℃or higher, more preferably 105℃or higher, still more preferably 110℃or higher, particularly preferably 115℃or higher. The upper limit of the softening point is, for example, preferably 300℃or lower, more preferably 250℃or lower, and still more preferably 200℃or lower.

Compounding of the softener is effective for improving adhesion. Examples of the softener include low-molecular-weight diene polymers, polyisobutylenes, hydrogenated polyisoprenes, hydrogenated polybutadienes, and derivatives thereof. Examples of such derivatives include derivatives having an OH group and a COOH group at one or both ends, and specifically, hydrogenated polybutadiene diol, hydrogenated polybutadiene monol, hydrogenated polyisoprene diol, hydrogenated polyisoprene monol, and the like. In particular, hydrogenated polybutadiene, hydrogenated polyisoprene and other diene polymers, olefin softeners and the like are preferable for the purpose of suppressing the improvement of the adhesion to an adherend. As such a softener, specifically, a trade name "KURAPREN LIR-200" manufactured by Kagaku Co., ltd, or the like, can be obtained. These softeners may be used in an amount of 1 or 2 or more.

The molecular weight of the softener may be appropriately set to any appropriate amount, but if the molecular weight is reduced, there is a concern that the substance transfer from the pressure-sensitive adhesive layer (B) to the adherend, the re-peeling, and the like may be caused, and if the molecular weight is increased, the effect of improving the adhesive force tends to be insufficient, so that the number average molecular weight of the softener is preferably 5000 to 10 ten thousand, more preferably 1 to 5 ten thousand.

When the softener is used, the amount of the softener to be added may be appropriately set to any appropriate amount, but when the amount to be added is increased, the amount of the residual gum tends to increase at high temperature and in outdoor exposure, and therefore, the amount is preferably 100% by weight or less, more preferably 60% by weight or less, and further preferably 40% by weight or less, relative to the base polymer of the adhesive layer (B). In the case where the adherend is a metal plate, it is preferable that no softener is added at the time of forming the adhesive layer (B).

The polyolefin resin may be added to the pressure-sensitive adhesive layer (B) for the purpose of suppressing an increase in adhesion or the like. The polyolefin resin may be 1 or 2 or more. 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, relative to the base polymer of the adhesive layer.

Method for producing surface protective film 2

The surface protective film of the embodiments of the present invention may be manufactured by any suitable method. Such a manufacturing method may be, for example, according to the following

(1) A method of applying a solution of a material for forming the adhesive layer (B) and a hot melt to the base material layer (A);

(2) A method of applying a solution or hot melt of a material for forming the adhesive layer (B) to the release film and transferring the formed adhesive layer (B) to the base material layer (A);

(3) A method of extruding and coating a material for forming the adhesive layer (B) onto the base material layer (A);

(4) A method of extruding the base material layer (A) and the adhesive layer (B) in 2 or more layers;

(5) A method of laminating the adhesive layer (B) on the substrate layer (a) as a single layer, or a method of laminating the adhesive layer (B) with the laminate layer for 2 layers;

(6) A method of laminating 2 or more layers of the adhesive layer (B) with a base layer forming material such as a film or a laminate layer;

and the like by any suitable manufacturing method.

Examples of the coating method include a roll coater method, a comma coater method, a die coater method, a reverse coater method, a screen printing method, and a gravure coater method.

The substrate layer (a) may be manufactured by any suitable method. Examples of such a production method include a method of extrusion molding a material of each layer constituting the base material layer (a). For example, when the base material layer (a) is 3 layers of the base material layer (A1)/the base material layer (A2)/the auxiliary base material layer (A3), extrusion molding of 3 layers is exemplified. In the case of 3 layers of the base material layer (A1)/the base material layer (A2)/the auxiliary base material layer (A3), the material of the base material layer (A1) is the same as that of the auxiliary base material layer (A3), 2 kinds of extrusion molding of 3 layers are exemplified.

"3. Use

The surface protective film of the present invention may be used for any suitable purpose. In view of the effects of the present invention, the surface protective film of the present invention is preferably used for manufacturing a member provided in a mobile device, and more preferably used for protecting the surface of a resin substrate when the resin substrate is subjected to hot press processing. In this case, the heating temperature in the hot press is preferably 50 to 250 ℃, more preferably 120 to 250 ℃.

Examples

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

< maximum Peak temperature measured based on DSC >

Melting point measurements were performed on the surface protective films of examples and comparative examples using a temperature-modulated DSC (trade name "Q-2000", manufactured by TA Instruments Co.). As a sample piece, about 1 to 2mg was weighed into an aluminum open cell, and Reversing Heat Flow (specific heat component) behavior of the sample piece was obtained at a temperature rising rate of 10℃per minute under a nitrogen atmosphere of 50 ml/min. With reference to JIS-K-7121, the temperature at the point at which a straight line at equal distance in the longitudinal axis direction from a straight line obtained by extending the low-temperature side base line and the high-temperature side base line of Reversing Heat Flow and a curve of a step-like change portion accompanying melting intersect was taken as the "peak temperature (°c)" of each sample. When more than 2 peaks occur, the peak temperature at a higher temperature is referred to as the "highest peak temperature (DEG C)". When the melting point of the surface protective film is measured by DSC, a plurality of peak temperatures derived from the composition of each layer included in the surface protective film may be measured, and in this case, the "highest peak temperature" among the plurality of peak temperatures corresponds to the highest peak temperature of the heat-resistant base material layer (A1) included in the surface protective film in the embodiment of the present invention.

< high temperature storage modulus >

The surface protective films of examples and comparative examples were measured for tensile storage modulus (MPa) by dynamic viscoelasticity measurement using a dynamic viscoelasticity measuring device (trade name "RSA-G3", manufactured by TA Instruments). In this measurement, the dimensions of the surface protective film to be measured were 10mm wide by 40mm long, the initial inter-chuck distance of the chuck for holding the sample sheet was 10mm, the measurement mode was a stretching mode, the measurement temperature range was 25 to 170 ℃, the frequency was 1Hz, and the temperature rise rate was 5 ℃/min. The measurement result at 120℃was used as the high-temperature storage modulus. The high-temperature storage modulus (storage modulus at 120 ℃) is an index indicating the hardness of the surface protective film itself, and when the value is high, damage (orange peel) to the surface of the resin substrate to which the surface protective film is attached is likely to occur.

< evaluation of high-temperature sliding Property >

The evaluation was performed as shown in fig. 4. The surface protective films of examples and comparative examples were cut to a size of 100mm wide by 200mm long, and a double-sided tape (manufactured by Nito electric Co., ltd., no. 5610) having the same shape as the surface protective film was used to attach the adhesive surface side to a standard test plate (JISG 3141: nippon Test Panel Co., ltd.) to prepare a test sample 200. Further, a polyester film (Mitsubishi resin Co., ltd., MRF#38) having a thickness of 38 μm, on one surface of which a silicone-based peeling treatment was performed, was cut into a size of 100mm wide by 100mm long, and a double-sided tape (manufactured by Nito electric Co., ltd., no. 5610) having the same shape as the polyester film was used to attach a non-peeled surface side (300 in FIG. 4) to three sides of a surface protection film on a standard test plate. The slide sheet 400 was placed on the polyester film, and after standing at 130℃for 5 minutes, the kinetic friction force (N) of the outermost layer was measured in accordance with JIS K7125. The contact area of the slide sheet was 20mm×20mm, a SUS430BA plate having a thickness of 0.4mm×20mm was used on the surface to be in contact with the surface protective film, the total mass of the slide sheet was set to 100g (0.98N) including the SUS430BA plate, the slide sheet was stretched at a sliding speed of 300mm/min until the slide sheet was moved by 50mm on the surface protective film by using a 50N load cell 500, and the detected maximum stress was used as a friction value to evaluate Gao Wenhua flowability.

< orange peel resistance >

After the test piece was peeled from the PMMA plate after the vacuum pressure molding in the same manner as in the above-described measurement method of the mold adhesion prevention property, the peeled surface was marked as "x" when the transfer roughness on the surface of the SUS304 plate polished with sandpaper No.360 was visually confirmed, and the case where the transfer roughness was not confirmed was marked as good.

< Forming Condition >

In examples and comparative examples, 3 kinds of 3-layer (layer a/layer B/layer C) extrusion T-die molding machines were used to mold substrates. The extrusion temperature was carried out under the following conditions.

Layer A: 200 DEG C

Layer B: 200 DEG C

And C layer: 200 DEG C

Mold temperature: 200 DEG C

The obtained base material was sufficiently cured by coextrusion molding from a T die and was wound into a roll shape, whereby a roll was produced.

Example 1

A propylene resin (trade name: WINTEC WFW, propylene/ethylene random polymer obtained by polymerization using a metallocene catalyst, manufactured by Japanese polypropylene Co., ltd.) and a silylated polyolefin master batch were mixed, and an A1 layer-forming material was prepared (the mixing ratio of the silylated polyolefin master batch was 10% by weight, and the content of the silylated polyolefin in the A1 layer-forming material was 3% by weight). The silylated polyolefin masterbatch is a masterbatch containing a silylated polyolefin as a release agent (produced by a method shown in examples of japanese patent application laid-open No. 2011-26448): 30 parts of low-density polyethylene resin: 70 parts of the mixture.

The above-mentioned A1 layer forming material was put into A1 layer of an extruder, low Density Polyethylene (LDPE) (trade name: novatec LD LC720, manufactured by japan polyethylene co., ltd.) was put into A2 layer of the extruder, low Density Polyethylene (LDPE) (trade name: novatec LD LC720, manufactured by japan polyethylene co., ltd.) was put into A3 layer of the extruder, and A1 layer/A2 layer/A3 layer = 5 μm/25 μm, total thickness laminate of 55 μm was extruded and thinned to obtain a base material layer (1).

As the adhesive, a styrene-ethylene-butylene-styrene block copolymer (SEBS) (trade name: kraton G1657, manufactured by Kraton Co., ltd.) was prepared: 100 parts by weight of a tackifier (Arkon P-100, manufactured by Kagaku chemical Co., ltd.): 40 parts of the mixture was dissolved in a diluting solvent (toluene), and the mixture was applied to the surface of the A3 layer of the base layer (1) and dried to form an adhesive layer having a thickness of 5. Mu.m.

According to the above, the surface protection film (1) is obtained.

The results are shown in Table 1.

Example 2

A surface protective film (2) was obtained in the same manner as in example 1, except that the compounding ratio of the silylated polyolefin masterbatch was changed to 25% by weight (the content ratio of the silylated polyolefin in the A1 layer forming material was 7.5% by weight).

The results are shown in Table 1.

Example 3

A surface protective film (3) was obtained in the same manner as in example 1 except that the thickness of A1 layer/A2 layer/A3 layer=10 μm/50 μm and the total thickness was 110 μm.

The results are shown in Table 1.

Example 4

A surface protective film (4) was obtained in the same manner as in example 1, except that an adhesive layer having a thickness of 15 μm was formed.

The results are shown in Table 1.

Example 5

A surface protective film (5) was obtained in the same manner as in example 1, except that polypropylene (PP) (trade name: WINTEC WFW, manufactured by japan polypropylene corporation) was used for the A3 layer of the extruder, and the thickness of the A1 layer/A2 layer/A3 layer=2.5 μm/50 μm/2.5 μm was set to 55 μm in total.

The results are shown in Table 1.

Example 6

A surface-protecting film (6) was obtained in the same manner as in example 1, except that a high-density polyethylene (HDPE) (trade name: nipolon Hard 4000, manufactured by Tosoh Co., ltd.) was used in the A1 layer of the extruder instead of the propylene-based resin (trade name: WINTEC WFW, manufactured by Japanese Polypropylene Co., ltd.).

The results are shown in Table 1.

Example 7

A surface protective film (7) was obtained in the same manner as in example 1, except that a propylene resin (trade name: WINTEC WFW, manufactured by sumitomo chemical Co., ltd., nobrene FL6737, propylene/ethylene random polymer) was used in place of the propylene resin (trade name: WINTEC WFW, manufactured by japan polypropylene Co., ltd.) in the A1 layer of the extruder, and the thickness of 60 μm was set to be A1 layer/A2 layer/A3 layer=10 μm/25 μm.

The results are shown in Table 1.

Example 8

A surface protective film (8) was obtained in the same manner as in example 7, except that the compounding ratio of the silylated polyolefin masterbatch was 5% by weight (the content ratio of the silylated polyolefin in the a layer forming material was 1.5% by weight).

The results are shown in Table 2.

Example 9

A surface protective film (9) was obtained in the same manner as in example 1, except that a propylene-based resin (trade name: novatec PP SA06GA, propylene homopolymer obtained by polymerization using ziegler catalyst) and a silylated polyolefin masterbatch were mixed, and an A1 layer-forming material was prepared (the mixing ratio of the silylated polyolefin masterbatch was 25% by weight, and the content of the silylated polyolefin in the A1 layer-forming material was 7.5% by weight).

The results are shown in Table 2.

Example 10

As the binder, butyl Acrylate (BA) was contained in a reaction vessel including a cooling tube, a nitrogen inlet tube, a thermometer, and a stirring device: 58 parts of n-butyl methacrylate: 40 parts of Acrylic Acid (AA): 2 parts of a monomer mixture 100 parts, and polyoxyethylene alkylpropenyl phenyl ether ammonium sulfate (trade name "Aqualon BC-2020", manufactured by first industry pharmaceutical co., ltd.) as an emulsifier was added: 2 parts of polyoxyethylene dialkyl phenyl ether phosphoric acid (trade name "Phosphanol RE-410", pKa:2, 7 (mixture of monoester and diester)): 2.4 parts of 2,2' -azobis (2-amidinopropane) dihydrochloride (manufactured by Wako pure chemical industries, ltd., trade name V-50) as a polymerization initiator: 0.03 part of water was added so as to form a desired solid component, and emulsion polymerization was carried out at 60℃for 5 hours. After completion of the polymerization, 10% strength aqueous ammonia (product name "10% aqueous ammonia" manufactured by Kishida Chemical co., ltd.) was added to the reaction solution and adjusted to ph8.0, to obtain an acrylic polymer emulsion. The SP value of the obtained acrylic polymer was 9.32, and Tg was-28.6 ℃. With respect to the solid content of the acrylic polymer emulsion: 100 parts by weight of an oxazoline-based crosslinking agent (trade name "eporos WS-500", manufactured by japan catalyst co.): 2 parts of an acrylic adhesive solution was obtained. A surface protective film (10) was obtained in the same manner as in example 1, except that the binder solution was used as a material for forming the binder layer.

The results are shown in Table 2.

Example 11

Styrene-ethylene-butylene-styrene block copolymer (SEBS) (trade name: kraton G1657, manufactured by Kraton Co., ltd.) was used for the A3 layer: 100 parts by weight of a tackifier (Arkon P-100, manufactured by Kagaku chemical Co., ltd.): a surface protective film (11) was obtained in the same manner as in example 1 except that 40 parts of the mixture was used as the adhesive, and the thickness of the layer A1/layer A2/layer a 3=5 μm/50 μm/5 μm was set to 60 μm in total, and the adhesive was not applied to the surface of the layer A3.

The results are shown in Table 2.

Example 12

A surface protective film (12) was obtained in the same manner as in example 11, except that a polyolefin-based adhesive resin (Tafcelene H5002, manufactured by Sumitomo chemical Co., ltd.) was used for the layer A3.

The results are shown in Table 2.

Example 13

A surface protective film (13) was obtained in the same manner as in example 1, except that an ethylene/vinyl acetate copolymer (EVA) (Mitsui DuPont Polychemical co., manufactured by ltd., trade name: evafelex EV 550) was used for the A2 layer and the A3 layer of the extruder.

The results are shown in Table 2.

Example 14

A propylene resin (trade name: WINTEC WFW, propylene/ethylene random polymer obtained by polymerization using a metallocene catalyst, manufactured by Japanese polypropylene Co., ltd.) and a silylated polyolefin master batch were mixed, and an A1 layer-forming material was prepared (the mixing ratio of the silylated polyolefin master batch was 10% by weight, and the content of the silylated polyolefin in the A1 layer-forming material was 3% by weight). The silylated polyolefin masterbatch is a masterbatch containing a silylated polyolefin as a release agent (produced by a method shown in examples of japanese patent application laid-open No. 2011-26448): 30 parts of polypropylene resin: 70 parts of the mixture.

A surface protective film (14) was obtained in the same manner as in example 1, except that the A1 layer-forming material was used for the A1 layer of the extruder.

The results are shown in Table 2.

Example 15

Crystalline pentene-based resin (trade name: TPX MX002, manufactured by Mitsui chemical Co., ltd.) using 4-methylpentene-1 as a main material was put into the A1 layer of the extruder, propylene-based resin (trade name: WINTEC WFW4, manufactured by japan polypropylene co., ltd.) was put into the A2 layer of the extruder, propylene-based resin (trade name: WINTEC WFW4, manufactured by japan polypropylene co., ltd.) was put into the A3 layer of the extruder, and a laminate of A1 layer/A2 layer/A3 layer=5 μm/15 μm/10 μm and a total thickness of 30 μm was extruded and thinned to obtain the base material layer (1).

As the adhesive, a styrene-ethylene-butylene-styrene block copolymer (SEBS) (trade name: kraton G1657, manufactured by Kraton Co., ltd.) was prepared: 100 parts by weight of a tackifier (Arkon P-100, manufactured by Kagaku chemical Co., ltd.): 40 parts of the mixture was dissolved in a diluting solvent (toluene), and the mixture was applied to the surface of the A3 layer of the base layer (1) and dried to form an adhesive layer having a thickness of 10. Mu.m.

According to the above, the surface protection film (15) is obtained.

The results are shown in Table 3.

Example 16

A surface protective film (16) was obtained in the same manner as in example 15, except that a crystalline pentene-based resin (trade name: TPX MX002, manufactured by three-well chemical Co., ltd.) using 4-methylpentene-1 as a main material was charged into the A1 layer of the extruder instead of the crystalline pentene-based resin (trade name: TPX DX310, manufactured by three-well chemical Co., ltd.).

The results are shown in Table 3.

Example 17

A surface protective film (17) was obtained in the same manner as in example 15, except that a propylene resin (trade name: WINTEC WFW, manufactured by sumitomo chemical Co., ltd., trade name: nobrene FL6737, propylene/ethylene random polymer) was charged into the A2 layer and the A3 layer of the extruder, respectively, instead of the propylene resin.

The results are shown in Table 3.

Example 18

A surface protective film (18) was obtained in the same manner as in example 15, except that a propylene resin (trade name: WINTEC WFW, manufactured by sumitomo chemical Co., ltd., trade name: nobrene FS2011DG3, homo-polypropylene) was charged into the A2 layer and the A3 layer of the extruder, respectively, instead of the propylene resin.

The results are shown in Table 3.

Example 19

Styrene-ethylene-butylene-styrene block copolymer (SEBS) (trade name: kraton G1657, manufactured by Kraton Co., ltd.) was used for the A3 layer: 100 parts by weight of a tackifier (Arkon P-100, manufactured by Kagaku chemical Co., ltd.): a surface protective film (19) was obtained in the same manner as in example 18 except that 40 parts of the mixture was used as the adhesive, and the thickness of the layer A1/layer A2/layer a 3=5 μm/25 μm/10 μm was set to 40 μm in total, and the adhesive was not applied to the surface of the layer A3.

The results are shown in Table 3.

Example 20

A surface protective film (20) was obtained in the same manner as in example 15 except that the thickness of the A1 layer was changed to 10. Mu.m.

The results are shown in Table 3.

Example 21

As the binder, in a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirring device, the reaction vessel was prepared from Butyl Acrylate (BA): 58 parts of n-butyl methacrylate: 40 parts of Acrylic Acid (AA): 2 parts of the resulting monomer mixture (100 parts) were added polyoxyethylene alkylpropenyl phenyl ether ammonium sulfate (trade name "Aqualon BC-2020", manufactured by first industry pharmaceutical co., ltd.): 2 parts of polyoxyethylene dialkyl phenyl ether phosphoric acid (trade name "Phosphanol RE-410", pKa:2, 7 (mixture of monoester and diester)): 2.4 parts of 2,2' -azobis (2-amidinopropane) dihydrochloride (manufactured by Wako pure chemical industries, ltd., trade name V-50) as a polymerization initiator: 0.03 part of water was added so as to form a desired solid component, and emulsion polymerization was carried out at 60℃for 5 hours. After completion of the polymerization, 10% strength aqueous ammonia (product name "10% aqueous ammonia" manufactured by Kishida Chemical co., ltd.) was added to the reaction solution and adjusted to ph8.0, to obtain an acrylic polymer emulsion. The SP value of the obtained acrylic polymer was 9.32, and Tg was-28.6 ℃. With respect to the solid content of the acrylic polymer emulsion: 100 parts by weight of an oxazoline-based crosslinking agent (trade name "eporos WS-500", manufactured by japan catalyst co.): 2 parts of an acrylic adhesive solution was obtained. A surface protective film (21) was obtained in the same manner as in example 15, except that the binder solution was used as a material for forming the binder layer.

The results are shown in Table 3.

Comparative example 1

A surface protective film (C1) was obtained in the same manner as in example 1, except that the compounding ratio of the silylated polyolefin masterbatch was set to 0 wt%.

The results are shown in Table 4.

Comparative example 2

A surface protective film (C2) was obtained in the same manner as in example 1, except that an A1 layer-forming material including 0 wt% of a Low Density Polyethylene (LDPE) (trade name: novatec LD LC720, manufactured by japan polyethylene co.) and a silylated polyolefin masterbatch was used as the A1 layer of the extruder.

The results are shown in Table 4.

Comparative example 3

A surface protective film (C3) was obtained in the same manner as in example 1, except that an a layer forming material containing 5 wt% of a Low Density Polyethylene (LDPE) (trade name: novatec LD LC720, manufactured by japan polyethylene co.) and a silylated polyolefin masterbatch was used for the A1 layer of the extruder.

The results are shown in Table 4.

Comparative example 4

A surface protective film (C4) was obtained in the same manner as in example 1, except that a propylene resin (trade name: novatec PP SA06GA, manufactured by japan polypropylene corporation) was used as the base resin for the A1 layer, A2 layer and A3 layer of the extruder.

The results are shown in Table 4.

Comparative example 5

A surface protective film (C5) was obtained in the same manner as in example 1, except that a polyethylene terephthalate (PET) film (manufactured by mitsubishi resin corporation, diafile T100, thickness 100 μm) was used as the base material.

The results are shown in Table 4.

TABLE 1

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TABLE 2

TABLE 3

TABLE 4

Industrial applicability

The surface protective film of the present invention can be used for manufacturing a member provided in a mobile device, for example.

Description of the reference numerals

100. Surface protective film

10. Base material layer (A)

11. Base material layer (A1)

12. Base material layer (A2)

13. Auxiliary base material layer (A3)

20. Adhesive layer (B)

200. Test sample obtained by attaching the adhesive layer of the surface protective film to the standard test plate with double-sided tape

300. The non-peeling-treated surface side of the polyester film subjected to the peeling treatment was attached to the portion of the test sample 200

400. Sliding sheet

500 50N load sensor

Claims

1. A surface protective film comprising a base layer (A) and an adhesive layer (B),

the substrate layer (A) comprises a substrate layer (A1),

the friction force of the base material layer (A1) at 130 ℃ is below 4.5N,

the storage modulus of the surface protection film at 120 ℃ is below 50 MPa.

2. The surface protective film according to claim 1, having a total thickness of 20 μm to 180 μm.

3. The surface protective film according to claim 1 or 2, wherein the thickness of the base material layer (a) as a whole is 10 μm to 150 μm.

4. The surface protective film according to any one of claims 1 to 3, wherein the thickness of the base material layer (A1) is 1 μm to 60 μm.

5. The surface protective film according to any one of claims 1 to 4, wherein the substrate layer (A1) has a peak temperature of 130 ℃ or higher as measured by DSC.

6. The surface protective film according to any one of claims 1 to 5, wherein the base material layer (A1) contains a release agent.

7. The surface-protecting film according to claim 6, wherein the content ratio of the release agent in the base material layer (A1) is 0.1 to 30% by weight.

8. The surface-protecting film according to claim 6 or 7, wherein the release agent comprises a silicone-based release agent.

9. The surface-protecting film according to claim 8, wherein the silicone-based release agent comprises a silylated polyolefin.

10. The surface protective film according to any one of claims 1 to 9, wherein the base material layer (A1) contains at least 1 selected from the group consisting of vinyl resins and propylene resins.

11. The surface protective film according to claim 10, wherein the vinyl resin comprises high density polyethylene.

12. The surface-protecting film according to claim 10 or 11, wherein the propylene-based resin comprises at least 1 selected from the group consisting of random polypropylene, block polypropylene and homo-polypropylene.

13. The surface protective film according to any one of claims 1 to 5, wherein the base material layer (A1) contains a pentene-based resin.

14. The surface protection film according to any one of claims 1 to 13, wherein the base material layer (a) sequentially comprises the base material layer (A1) and a base material layer (A2).

15. The surface protective film according to claim 14, wherein the base material layer (A2) comprises a vinyl resin.

16. The surface-protecting film according to claim 15, wherein the vinyl resin contains at least 1 selected from the group consisting of low-density polyethylene and ethylene-vinyl acetate copolymer.

17. The surface protective film according to claim 14, wherein the base material layer (A2) comprises an acryl-based resin.

18. The surface protective film according to claim 17, wherein the propylene-based resin comprises a homo-polypropylene.

19. The surface protection film according to any one of claims 14 to 18, wherein the base material layer (a) comprises the base material layer (A1), the base material layer (A2), and an auxiliary base material layer (A3) in this order.

20. The surface protective film according to claim 19, wherein an error between the thickness of the auxiliary base material layer (A3) and the thickness of the base material layer (A1) is ±50% or less.

21. The surface protective film according to claim 19 or 20, wherein the resin of the main component contained in the auxiliary base material layer (A3) is the same kind of resin as the resin of the main component contained in the base material layer (A1).

22. The surface protective film according to any one of claims 1 to 21, which is used for manufacturing a member provided in a mobile device.

23. The surface protective film according to any one of claims 1 to 22, which is used for protecting a surface of a resin substrate when the resin substrate is subjected to hot press working.

24. The surface protective film according to claim 23, wherein the heating temperature at the time of hot press working is 50 ℃ to 250 ℃.