TW202302685A - Surface-protective film - Google Patents

Abstract

The purpose of the present invention is to provide a surface-protective film which has high adhesive force (initial adhesive force) and which, after having been applied to an adherend, is less apt to increase in adhesive force with the lapse of time or even at high temperatures and can be removed therefrom without leaving an adhesive residue. This surface-protective film comprises a substrate layer and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer, when examined by a CPMG method at 60 DEG C using pulsed NMR, has an L-component content of 10% or less and a relaxation time of 25-80 msec and, when examined by a solid echo method at 25 DEG C using pulsed NMR, has an L-component content of 30-65% and a relaxation time of 0.2-0.4 msec.

Description

surface protection film

The present invention relates to a surface protection film having high adhesive force (initial adhesive force), after being attached to an adherend, the adhesive force does not easily increase over time or under high temperature, and can be peeled off without paste residue.

In the past, in order to protect the surface of components such as optical devices, metal plates, coated metal plates, resin plates, and glass plates, surface protection films (generally It may also be called a protective tape, etc.) (eg, Patent Documents 1 to 3). Among these, in order to protect the surface of the optical member for liquid crystal displays, a surface protection film is used. Optical components include those with concavo-convex shapes on one or both sides of the surface, such as flakes and diffusion films. In order not to damage the concavo-convex shapes, the surface of the optical components is treated with a surface protection film before use. Protect.

The surface protection film requires high adhesion according to the application. For example, in the case of bonding to an adherend having a concave-convex surface, a large contact area cannot be obtained, and peeling tends to occur at the interface between the adherend and the surface protection film. In such applications, particularly high adhesion is required for surface protection films.

Generally, in order to improve the adhesive force, it is more effective to control the composition or structure of the base resin used in the adhesive layer to make a soft base resin, or to increase the blending amount of the tackifying resin in the adhesive layer. However, it is known that such an adhesive layer, especially when the adherend has a concave-convex shape on the surface, increases the adhesive force over time or at high temperature due to the increase in the contact area between the adherend and the adhesive layer, That is, a problem of so-called hyperadhesion occurs, and peeling becomes difficult or paste residue occurs. prior art literature patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 1-129085 Patent Document 2: Japanese Patent Application Laid-Open No. 6-1958 Patent Document 3: Japanese Patent Application Laid-Open No. 8-12952

[Problem to be Solved by the Invention]

The object of the present invention is to provide a surface protection film which has a high adhesive force (initial adhesive force), and after being attached to an adherend, the adhesive force is not easy to increase over time or under high temperature, and can be formed without paste residue. peel off. [Technical means to solve the problem]

The present invention 1 is a surface protection film comprising a base material layer and an adhesive layer, wherein the adhesive layer has a component ratio of L component measured by the CPMG method at 60° C. using pulsed NMR of 10% or less, The relaxation time is not less than 25 milliseconds and not more than 80 milliseconds, the composition ratio of the L component measured by the Solid Echo method at 25°C using pulsed NMR is not less than 30% and not more than 65%, and the relaxation time is not less than 0.2 milliseconds and 0.4 milliseconds or less.

Invention 2 is the surface protection film according to Invention 1, wherein the above-mentioned adhesive layer has a component ratio of S component measured by the CPMG method at 60°C using pulsed NMR of 45% or more, and a relaxation time of 0.4 milliseconds Above and below 0.8 milliseconds.

The present invention 3 is the surface protection film according to the present invention 1 or 2, wherein the adhesive layer contains a styrene-based elastomer.

The present invention 4 is the surface protective film according to the present invention 3, wherein the above-mentioned styrene-based elastomer system styrene-based elastomer (I), the styrene-based elastomer (I) contains benzene having a structure represented by the general formula AB Ethylene block copolymer or its hydrogenated product (1), and styrene block copolymer or its hydrogenated product (2) having a structure represented by general formula ABA or general formula (AB) _n C, the above-mentioned styrene block The content of the copolymer or its hydrogenated product (1) in 100% by weight of the above-mentioned styrene-based elastomer (I) is 15% by weight or more and 50% by weight or less, and the above-mentioned styrene block copolymer or its hydrogenated product (2 ) to 100% by weight of the above-mentioned styrene-based elastomer (I) is 50% by weight or more and 85% by weight or less, A: aromatic alkenyl polymer block, B: conjugated diene polymer block , C: a component derived from a coupling agent, n: an integer of 2 or more.

Invention 5 is the surface protection film according to Invention 3 or 4, wherein the adhesive layer further contains a tackifying resin, and the content of the tackifying resin is 12 parts by weight or more relative to 100 parts by weight of the styrene-based elastomer and 45 parts by weight or less.

This invention 6 is the surface protection film of this invention 4 whose n is 4 in the said styrene-type elastomer (I).

The present invention 7 is the surface protection film according to the present invention 1, 2, 3, 4, 5 or 6, wherein the composition ratio of the L component measured by the CPMG method at 60°C using pulsed NMR in the adhesive layer is: 6.5% or less, and the relaxation time is not less than 30 milliseconds and not more than 70 milliseconds. The present invention will be described in detail below.

The inventors of the present invention analyzed an adhesive layer having a substrate layer and a surface protection film of an adhesive layer using pulsed NMR for measuring ¹ H nuclei. In pulsed NMR, the free induction decay curve waveform of spin-spin relaxation of ¹ H nuclei obtained can be separated into multiple components, and the "relaxation time" of each component can be obtained, and the component can be evaluated. molecular mobility. The inventors of the present invention conducted the following studies: the component ratio and relaxation time of the L component measured by the CPMG method using pulsed NMR at 60°C on the adhesive layer, and the measurement of the L component by the pulsed NMR at 25°C by Solid The component ratio and relaxation time of the L component measured by the Echo method were adjusted to a specific range. The inventors of the present invention have found that by using such an adhesive layer, the adhesive force (initial adhesive force) at the time of attachment can be improved, and on the other hand, it is possible to suppress the increase of the adhesive force over time or at high temperature, and to suppress the paste residue, thereby The present invention has been accomplished.

The surface protection film of the present invention is a surface protection film having a base material layer and an adhesive layer. The above-mentioned pressure-sensitive adhesive layer has a component ratio of the L component measured by the CPMG method at 60° C. using pulsed NMR of 10% or less, and a relaxation time of 25 milliseconds to 80 milliseconds.

Here, the "L component" measured by pulsed NMR refers to the free induction decay curve of spin-spin relaxation of ¹ H nuclei measured by pulsed NMR in order of relaxation time from short to long The component with the longest relaxation time when the sequential waveform is separated into three components. The waveform separation of the three components (S component, M component, and L component in order of relaxation time from short to long) was performed by analyzing the free induction decay curve using the least square method.

"Relaxation time" refers to the time until the electron spin returns from the excited state to the ground state after applying a magnetic field. The longer the "relaxation time", the higher the mobility of the molecule. That is, the S component is a relatively low-mobility hard component whose relaxation time is the shortest and whose magnetization immediately decays. The L component is a relatively high molecular mobility soft component with the longest relaxation time and time-consuming decay of magnetization. The M component is a component having a relaxation time and molecular mobility intermediate between the S component and the L component.

If the component ratio of the above-mentioned L component at 60°C is 10% or less, it means that there are relatively few components with relatively high molecular mobility at high temperatures, and the adhesive force of the above-mentioned adhesive layer is not easy to increase over time or at high temperatures. Peel off without paste residue. The preferable upper limit of the component ratio of the above-mentioned L component at 60° C. is 8%, and the more preferable upper limit is 6.5%. The lower limit of the component ratio of the L component at 60° C. is not particularly limited, but the lower limit is preferably 0.1%, and more preferably 0.3%.

If the relaxation time of the above-mentioned L component at 60°C is 25 milliseconds or more, it means that the molecular mobility of the L component with relatively high molecular mobility at 60°C is above a certain level, which can prevent the above-mentioned adhesive layer from being stored at high temperature The modulus of elasticity becomes too high to cause peeling. If the relaxation time of the above-mentioned L component at 60°C is 80 milliseconds or less, it means that the molecular mobility of the L component with relatively high molecular mobility at 60°C is suppressed below a certain level, and the above-mentioned adhesive layer can be prevented. Therefore, the adhesive force of the above-mentioned adhesive layer is not easy to increase over time or under high temperature, and it can be peeled off without paste residue. The lower limit of the relaxation time of the above-mentioned L component at 60°C is preferably 26 milliseconds, more preferably 28 milliseconds, and further preferably 30 milliseconds, and a better upper limit is 75 milliseconds, more preferably 70 milliseconds.

In the adhesive layer, it is preferable that the component ratio of the S component measured by the CPMG method at 60° C. using pulsed NMR is 45% or more, and the relaxation time is 0.4 milliseconds or more and 0.8 milliseconds or less. When the component ratio of the S component at 60° C. is 45% or more, the adhesive force of the adhesive layer is less likely to increase over time or at high temperature, and can be peeled off without paste residue. The more preferable lower limit of the component ratio of the S component at 60° C. is 48%. The upper limit of the component ratio of the S component at 60°C is not particularly limited, but the upper limit is preferably 65%, and the upper limit is more preferably 60%.

If the relaxation time of the S component at 60° C. is within the above range, the adhesive layer is less likely to increase in adhesive force over time or at high temperature, and can be peeled off with no paste residue. The lower limit of the relaxation time of the S component at 60°C is preferably 0.45 milliseconds, the upper limit is 0.75 milliseconds, the lower limit is 0.50 milliseconds, and the upper limit is 0.70 milliseconds.

The adhesive layer has a composition ratio of the L component measured by the Solid Echo method at 25° C. using pulsed NMR of 30% to 65%, and a relaxation time of 0.2 milliseconds to 0.4 milliseconds. If the component ratio of the L component at 25° C. is within the above range, the adhesive layer can exhibit sufficient adhesive force to be attached to an adherend having an uneven surface. The lower limit of the ratio of the L component at 25°C is preferably 35%, the upper limit is 63%, the lower limit is 40%, the upper limit is 60%, and the lower limit is 45%.

If the relaxation time of the above-mentioned L component at 25°C is 0.2 milliseconds or more, it means that the molecular mobility of the L component with relatively high molecular mobility at 25°C is above a certain level, and the above-mentioned adhesive layer can also sufficiently follow the The surface of the adherend with unevenness on the surface has sufficient adhesion to the adherend. If the relaxation time of the above-mentioned L component at 25°C is 0.4 milliseconds or less, it means that the molecular mobility of the L component with relatively high molecular mobility at 25°C is suppressed below a certain level, which can prevent the above-mentioned adhesive layer from being released at room temperature. The storage elastic modulus is excessively reduced to prevent excessively following the bonded body and showing excessively high adhesive force. The lower limit of the relaxation time of the L component at 25°C is preferably 0.21 milliseconds, the upper limit is 0.38 milliseconds, the lower limit is 0.22 milliseconds, the upper limit is 0.35 milliseconds, and the lower limit is 0.24 milliseconds.

Furthermore, the measurement of pulsed NMR can use a pulsed NMR device (for example, the minispec mq20, manufactured by BRUKER, etc.) and analysis software (for example, TD-NMRA, manufactured by BRUKER, etc.), at a specified temperature for the preparation of the adhesive layer The resulting assay samples were carried out. The measurement sample can be prepared by dissolving part of the adhesive layer in toluene, allowing it to dry naturally, and vacuum drying it at 30° C. to remove the toluene.

There are no particular limitations on the method of adjusting the above-mentioned component ratio and relaxation time of the L component at 60°C, and the above-mentioned component ratio and relaxation time of the L component at 25°C to the above-mentioned ranges, for example, the following methods, etc. : A method of using a styrene-based elastomer as the base resin of the adhesive layer; a method of adjusting the structure, composition, weight average molecular weight (Mw), etc. of the styrene-based elastomer. Moreover, the following method etc. can also be mentioned: The method of mixing an tackifying resin in the said adhesive agent layer; The method of adjusting the kind, physical property (for example, softening point), blending amount, etc. of this tackifying resin. Furthermore, the method etc. which adjust the molding conditions of the said adhesive layer can also be mentioned.

The base resin constituting the adhesive layer is not particularly limited, and examples thereof include styrene-based elastomers, acrylic elastomers, urethane-based elastomers, and olefin-based elastomers. Among them, it is easy to adjust to the adhesion (initial adhesion) required by the surface protection film, and it is easy to adjust the molecular mobility of the above-mentioned adhesive layer relatively freely by selecting molecular structures such as styrene content or additives such as tackifiers. From a viewpoint, a styrene-based elastomer is preferable.

The above-mentioned styrene-based elastomer is not particularly limited, for example, styrene-ethylene propylene-styrene block copolymer (SEPS), hydrogenated styrene-butadiene rubber (HSBR), styrene-ethylene-butylene- Styrene Block Copolymer (SEBS), Styrene-Ethylene Propylene Block Copolymer (SEP), Styrene-Ethylene Butene Block Copolymer (SEB), Styrene-Isoprene Block Copolymer (SI ), styrene-isoprene-styrene block copolymer (SIS), styrene-butadiene block copolymer (SB), styrene-butadiene-styrene block copolymer (SBS) wait.

The weight average molecular weight (Mw) of the styrene-based elastomer is not particularly limited, but the lower limit is preferably 50,000, and the upper limit is 400,000. If the above-mentioned weight average molecular weight (Mw) is 50,000 or more, the storage elastic modulus of the above-mentioned adhesive layer at high temperature becomes higher, and the adhesive force is less likely to increase over time or at high temperature, and it can be more paste-free. peel off. If the above-mentioned weight average molecular weight (Mw) is 400,000 or less, the storage elastic modulus of the above-mentioned adhesive layer at room temperature will not increase excessively, and the adhesiveness when it is attached to the adherend becomes higher, so that the adhesive force (initial adhesion) becomes higher. A more preferable lower limit of the above-mentioned weight average molecular weight (Mw) is 80,000, and a more preferable upper limit is 350,000. In addition, weight average molecular weight (Mw) can be measured by the following method. Filter the sample solution with a filter (material: polytetrafluoroethylene, pore size: 0.2 μm). The obtained filtrate is supplied to a gel permeation chromatograph (for example, manufactured by Waters, 2690 Separations Model), and the GPC measurement is carried out under the conditions of a sample flow rate of 1 ml/min and a column temperature of 40° C., and the polyphenylene content of the sample is measured. Ethylene converted molecular weight was used to obtain the weight average molecular weight (Mw). As a column, for example, GPC KF-806L (manufactured by Showa Denko Co., Ltd.) is used, and as a detector, a differential refractometer is used.

Also, as the above-mentioned styrene-based elastomer, styrene-based elastomer (I) containing a styrene block copolymer having a structure represented by the general formula AB or its The hydride (1), and the styrene block copolymer having the structure represented by the general formula ABA or (AB) _n C or its hydride (2). By using the above-mentioned styrene-based elastomer (I), it is easy to adjust the component ratio and relaxation time of the L component at 60° C. and the component ratio and relaxation time of the L component at 25° C. to the above-mentioned ranges. A: Aromatic alkenyl polymer block B: Conjugated diene polymer block C: Component derived from coupling agent n: Integer of 2 or more

The above-mentioned styrene block copolymer having the structure represented by the general formula AB or its hydrogenated product (1) has an aromatic alkenyl polymer block represented by the above-mentioned A and a conjugated diene polymer represented by the above-mentioned B. Block linear styrene block copolymer or its hydrogenated product. The above-mentioned styrene block copolymer having a structure represented by the general formula ABA or its hydrogenated product (2) has an aromatic alkenyl polymer block represented by the above-mentioned A, and a conjugated diene polymer represented by the above-mentioned B Block linear styrene block copolymer or its hydrogenated product. The above-mentioned styrene block copolymer having the structure represented by the general formula (AB) _n C or its hydrogenated product (2) is a branched (radial) styrene block copolymer or its hydrogenated product having the following structure, The structure is centered on the coupling agent, and is composed of the above-mentioned styrene block copolymer having the structure represented by the general formula AB or its hydrogenated product (1) protruding in a plurality of radial shapes. However, in the case of n=2, it becomes a linear type.

The aromatic alkenyl polymer block represented by the above-mentioned A has a repeating unit derived from an aromatic alkenyl compound. Examples of the aromatic alkenyl compound include styrene, tert-butylstyrene, α-methylstyrene, p-methylstyrene, p-ethylstyrene, divinylbenzene, 1,1- Diphenylethylene, vinylnaphthalene, vinylanthracene, N,N-diethyl-p-aminoethylstyrene, vinylpyridine, etc. Among them, styrene is preferable from the viewpoint of industrial availability.

The content of the above-mentioned repeating unit derived from the aromatic alkenyl compound in the aromatic alkenyl polymer block represented by the above-mentioned A is not particularly limited, the lower limit is preferably 50% by weight, the upper limit is 100% by weight, and more preferably The lower limit is 70% by weight. When the aromatic alkenyl polymer block represented by the above-mentioned A contains repeating units derived from other compounds other than the repeating units derived from the above-mentioned aromatic alkenyl compounds, such a block having repeating units derived from other compounds It does not specifically limit, For example, a conjugated diene polymer, an ethylene polymer, a propylene polymer etc. are mentioned.

The above-mentioned conjugated diene polymer block represented by B has a repeating unit derived from a conjugated diene compound. Examples of the conjugated diene compound include: 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-Methyl-1,3-octadiene, 1,3-hexadiene, 1,3-cyclohexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl -1,3-octadiene, myrcene, chloroprene, etc. These conjugated diene compounds may be used alone or in combination of two or more. Among them, 1,3-butadiene and isoprene are preferable from the viewpoint of high polymerization reactivity and industrial availability.

The content of the above-mentioned repeating units derived from the conjugated diene compound in the conjugated diene polymer block represented by B above is not particularly limited, the lower limit is preferably 50% by weight, the upper limit is 100% by weight, and more preferably The lower limit is 70% by weight. In the case where the conjugated diene polymer block represented by B above contains repeating units derived from other compounds other than the repeating units derived from the above-mentioned conjugated diene compound, such a block having repeating units derived from other compounds It does not specifically limit, For example, an aromatic alkenyl polymer, an ethylene polymer, a propylene polymer etc. are mentioned.

The coupling agent used as a raw material for the component derived from the coupling agent represented by the above-mentioned C is a multifunctional compound that radially bonds the above-mentioned linear styrene block copolymer, that is, the above-mentioned styrene block copolymer or its hydrogenated product (1). Sexual compounds. Examples of the aforementioned coupling agent include silane compounds such as halosilanes and alkoxysilanes, tin compounds such as tin halides, polycarboxylates, epoxy compounds such as epoxidized soybean oil, or neopentylthritol tetraacrylate Acrylic esters, or divinyl compounds such as epoxy silane and divinylbenzene. In more specific examples, for example, trichlorosilane, tribromosilane, tetrachlorosilane, tetrabromosilane, methyltrimethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, vinyl trimethoxysilane, Triethoxysilane, tetramethoxysilane, tetraethoxysilane, tin tetrachloride, diethyl adipate, etc.

n is not particularly limited, as long as it is an integer of 2 or more, preferably 3 or more. When n is 3 or more, even when the molecular weight of the above-mentioned styrene-based elastomer (I) is increased to adjust the relaxation time of the L component at 60°C to the above-mentioned range, it is easy to maintain the above-mentioned adhesive layer of formability. n is particularly preferably 4 from the viewpoint of easily adjusting the component ratio and relaxation time of the L component at 60°C and the component ratio and relaxation time of the L component at 25°C to the above ranges. Furthermore, when n is 3, it is also called a 3-branched type, and when n is 4, it is also called a 4-branched type.

From the viewpoint of being easy to adjust the component ratio and relaxation time of the L component at 60°C and the component ratio and relaxation time of the L component at 25°C to the above ranges, the above-mentioned styrene-based elastomer (I ) preferably have a hydrogenation rate, weight average molecular weight, diblock ratio, styrene content, butene content, coupling rate, etc. within the following ranges.

When the above-mentioned styrene block copolymer or its hydrogenated product (1), or the above-mentioned styrene block copolymer or its hydrogenated product (2) is a hydrogenated product, the hydrogenated product may be partially hydrogenated or may be complete hydride. Among them, the above-mentioned repeating units derived from conjugated diene compounds are preferably more than 80%, more preferably more than 90%, and more preferably more than 95% of the double bonds (unsaturated bonds) are hydrogenated into saturated bonds by hydrogenation Things are better. In addition, the rate of hydrogenation (hydrogenation rate) means the hydrogenation rate calculated from the ¹ H-NMR spectrum at 270 MHz using carbon tetrachloride as a solvent.

The weight average molecular weight (Mw1) of the styrene block copolymer or its hydrogenated product (1) is not particularly limited, but the lower limit is preferably 40,000, and the upper limit is 150,000. If the above-mentioned weight average molecular weight (Mw1) is 40,000 or more, the weight average molecular weight (Mw2) of the above-mentioned styrene block copolymer or its hydrogenated product (2) will also increase, and the storage elastic modulus of the above-mentioned adhesive layer at high temperature It becomes higher, so the adhesive force is less likely to increase over time or under high temperature, and it can be peeled off more without paste residue. If the above-mentioned weight average molecular weight (Mw1) is 150,000 or less, the weight average molecular weight (Mw2) of the above-mentioned styrene block copolymer or its hydrogenated product (2) will not increase excessively, and the storage elasticity of the above-mentioned adhesive layer at room temperature The modulus does not increase excessively, so the adhesiveness when attached to the adherend becomes higher, and the adhesive force (initial adhesive force) becomes higher. The lower limit of the weight average molecular weight (Mw1) is preferably 50,000, the upper limit is 140,000, the lower limit is 60,000, and the upper limit is 120,000.

The weight average molecular weight (Mw2) of the styrene block copolymer or its hydrogenated product (2) is preferably at least 2.5 times the weight average molecular weight (Mw1) of the above styrene block copolymer or its hydrogenated product (1). If the above-mentioned weight average molecular weight (Mw2) is more than 2.5 times the above-mentioned weight average molecular weight (Mw1), the storage elastic modulus of the above-mentioned adhesive layer at high temperature will become higher, and the adhesion will be less easy over time or at high temperature It can be exfoliated more without paste residue. In addition, in this specification, when the said weight average molecular weight (Mw2) is 2.5 times or more of the said weight average molecular weight (Mw1), the styrene-type elastomer (I) is called radial type. When the above weight average molecular weight (Mw2) is less than 2.5 times the above weight average molecular weight (Mw1), the styrene-based elastomer (I) is called a linear type. The above weight average molecular weight (Mw2) is more preferably 2.7 times or more, further preferably 3.0 times or more of the above weight average molecular weight (Mw1).

The overall weight-average molecular weight of the styrene-based elastomer (I) is not particularly limited, but the lower limit is preferably 50,000, and the upper limit is 400,000. If the weight average molecular weight is more than 50,000, the storage elastic modulus of the adhesive layer at high temperature becomes higher, and the adhesive force is less likely to increase over time or at high temperature, and can be peeled off without adhesive residue. If the above-mentioned weight average molecular weight is 400,000 or less, the storage elastic modulus of the above-mentioned adhesive layer at room temperature will not increase excessively, and the adhesiveness when it is attached to the adherend becomes higher, so that the adhesive force (initial Adhesion) becomes higher. The lower limit of the weight average molecular weight is preferably 80,000, the upper limit is 350,000, the lower limit is 100,000, and the upper limit is 320,000.

The preferable lower limit of the content (diblock ratio) of the above-mentioned styrene block copolymer or its hydrogenated product (1) in 100% by weight of the above-mentioned styrene-based elastomer (I) is 15% by weight, and the preferable upper limit is 50% by weight. If the content of the above-mentioned styrene block copolymer or its hydrogenated product (1) is 15% by weight or more, the storage elastic modulus of the above-mentioned adhesive layer at room temperature will not increase excessively, and the adhesiveness when attached to the adherend will not be too high. The compatibility becomes higher, and thus the adhesion (initial adhesion) becomes higher. If the content of the above-mentioned styrene block copolymer or its hydrogenated product (1) is 50% by weight or less, the storage elastic modulus of the above-mentioned adhesive layer at high temperature becomes higher, and the adhesive force becomes weaker over time or at high temperature. It is easy to exfoliate and can be peeled off without paste residue. A more preferable lower limit of the content of the above-mentioned styrene block copolymer or its hydrogenated product (1) is 18% by weight, a more preferable upper limit is 47% by weight, a more preferable lower limit is 20% by weight, and a more preferable upper limit is 45% by weight . On the other hand, the preferred lower limit of the content of the above-mentioned styrene block copolymer or its hydrogenated product (2) in 100 wt% of the above-mentioned styrene-based elastomer (I) is 50 wt%, and the preferred upper limit is 85 wt%. %, a better lower limit is 53% by weight, and a better upper limit is 72% by weight.

In addition, in 100% by weight of the above-mentioned styrene-based elastomer (I), in addition to the above-mentioned styrene block copolymer or its hydrogenated product (1) and the above-mentioned styrene block copolymer or its hydrogenated product (2) , may further contain other ingredients. Furthermore, the diblock ratio can be calculated from the peak area ratio of each copolymer measured by gel permeation chromatography (GPC).

The weight ratio of the aromatic alkenyl polymer block represented by the above-mentioned A to the conjugated diene polymer block represented by the above-mentioned B in the above-mentioned styrene-based elastomer (I) as a whole is not particularly limited. In the above-mentioned styrene-based elastomer (I) as a whole, the conjugated diene polymer block represented by the above-mentioned B is polymerized with the conjugated diene represented by the above-mentioned B in the aromatic alkenyl polymer block represented by the above-mentioned A The preferable lower limit of the content of the total amount of the substance blocks is 35% by weight, and the preferable upper limit is 95% by weight. If the content of the conjugated diene polymer block represented by the above-mentioned B is within the above-mentioned range, the formability of the above-mentioned adhesive layer will be further improved, and the adhesiveness when it is attached to the adherend will be further improved, making the adhesive The strength (initial adhesion) becomes higher, and on the other hand, the adhesion is not easy to increase over time or under high temperature, and it can be peeled off without paste residue, and furthermore, the followability to the adherend is further improved. The more preferable lower limit of the content of the conjugated diene polymer block represented by B above is 45% by weight, and the more preferable upper limit is 87% by weight.

Examples of the above-mentioned styrene-based elastomer (I) include: styrene-ethylene-butylene-styrene block copolymer (SEBS) type, styrene-ethylene-propylene-styrene block copolymer (SEPS) Type, styrene-isobutylene-styrene block copolymer (SIBS) type, etc. Furthermore, for example, the type of the above-mentioned styrene-based elastomer (I) is SEBS type, which refers to the above-mentioned styrene block copolymer or its hydrogenated product (1), and the above-mentioned styrene block copolymer or its hydrogenated product (2) It has repeating units derived from styrene, repeating units derived from ethylene, and repeating units derived from butene. That is, it means that the aromatic alkenyl polymer block represented by the above-mentioned A is a block having a repeating unit derived from styrene, and the conjugated diene polymer block (its hydrogenated product) represented by the above-mentioned B is a block having a repeating unit derived from Repeating units of ethylene, and blocks of repeating units derived from butene.

When the styrene-based elastomer (I) has a repeating unit derived from styrene, the content of the repeating unit derived from styrene (styrene content) in the entire styrene-based elastomer (I) is not particularly limited. , the preferred lower limit is 5% by weight, and the preferred upper limit is 30% by weight. If the above-mentioned styrene content is within the above-mentioned range, the formability of the above-mentioned adhesive layer will be further improved, and the adhesiveness when it is attached to an adherend will be further improved, so that the adhesive force (initial adhesive force) becomes higher, and another On the one hand, the adhesive force is not easy to increase over time or under high temperature, and it can be peeled off without paste residue, and further, the followability to the adherend is further improved. The more preferable lower limit of the above-mentioned styrene content is 7% by weight, and the more preferable upper limit is 20% by weight.

When the above-mentioned styrene-based elastomer (I) has a butene-derived repeating unit, the content (butene content) of the butene-derived repeating unit in the above-mentioned styrene-based elastomer (I) as a whole is not particularly limited. The preferred lower limit is 30% by weight, and the upper limit is preferably 90% by weight. If the above-mentioned butene content is within the above-mentioned range, the formability of the above-mentioned adhesive layer will be further improved, and the adhesiveness when it is attached to an adherend will be further improved, so that the adhesive force (initial adhesive force) becomes higher. On the one hand, the adhesive force is not easy to increase over time or under high temperature, and it can be peeled off without paste residue, and furthermore, the followability to the adherend is further improved. The more preferable lower limit of the said butene content rate is 35 weight%, and the more preferable upper limit is 80 weight%.

The method for producing the above-mentioned styrene-based elastomer (I) is not particularly limited, and examples thereof include the following methods. First, step (a) is carried out, that is, the aromatic alkenyl polymer block represented by the above-mentioned A is synthesized. Then, step (b) is carried out, that is, by block polymerizing the conjugated diene compound and the aromatic alkenyl polymer represented by the above-mentioned A, a styrene block copolymer having a structure represented by the general formula AB is synthesized. thing (1). Next, carry out step (c), that is, by using a coupling agent to make the obtained styrene block copolymer (1) having the structure represented by the general formula AB undergo a coupling reaction to obtain the general formula ABA or the general formula (AB) A styrene block copolymer (2) having a structure represented by _n C. The coupling ratio at this time is not particularly limited, but the above-mentioned diblock ratio (the content of the above-mentioned styrene block copolymer or its hydrogenated product (1) in 100% by weight of the above-mentioned styrene-based elastomer (I) ) to adjust to the above-mentioned range, the better lower limit is 50%, and the better upper limit is 97%. The more preferable lower limit of the coupling rate is 55%, the more preferable upper limit is 95%, the more preferable lower limit is 58%, the more preferable upper limit is 90%, the more preferable lower limit is 60%, and the more preferable upper limit is 85%. Step (d), ie, hydrogenation of the styrenic block copolymer (1) and styrenic block copolymer (2), is optionally carried out.

It is preferable that the said adhesive agent layer further contains an tackifying resin. By adjusting the type, physical properties (such as softening point), and blending amount of the above-mentioned tackifying resin, it is easy to adjust the above-mentioned component ratio and relaxation time of the L component at 60°C, and the above-mentioned component ratio of the L component at 25°C And the relaxation time is adjusted to the above range.

The softening point of the tackifying resin is not particularly limited, but is preferably 80°C or higher, more preferably 90°C or higher and 140°C or lower. Examples of the tackifying resin include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic aromatic copolymers, and alicyclic copolymers, coumarone-indene-based resins, and terpene-based resins. , terpene-phenol resins, rosin-based resins such as polymerized rosin, (alkyl)phenol-based resins, xylene-based resins, and their hydrogenated products. Moreover, the tackifying resin marketed as a mixture with a polyolefin resin can be used. These tackifying resins may be used alone or in combination of two or more. Among them, the above-mentioned tackifying resin is preferably a hydrogenated product from the viewpoint that the adhesive force of the above-mentioned adhesive agent layer does not easily increase over time or at high temperature, and can be peeled off more without paste residue.

The content of the tackifying resin is not particularly limited, but the lower limit is preferably 12 parts by weight, and the upper limit is 45 parts by weight relative to 100 parts by weight of the base resin such as the above-mentioned styrene-based elastomer. If the content of the above-mentioned tackifying resin is 12 parts by weight or more, the followability to the adherend can be improved by reducing the storage elastic modulus of the above-mentioned adhesive layer, and the above-mentioned component ratio of the S component at 25°C can be prevented. As a result, the molecular mobility of the above-mentioned adhesive layer is inhibited, so that it follows the adherend excessively and increases the adhesive force. If the content of the above-mentioned tackifying resin is 45 parts by weight or less, the relaxation time of the above-mentioned L component at 60°C will not become too long, and the adhesive force of the above-mentioned adhesive layer will not be easy to increase over time or at high temperature, and can be Peel off even more without paste residue. The more preferable lower limit of the content of the above-mentioned tackifying resin is 15 parts by weight, the more preferable upper limit is 40 parts by weight, the more preferable lower limit is 18 parts by weight, and the more preferable upper limit is 35 parts by weight.

The above-mentioned adhesive layer may further contain known additives such as adhesion modifiers, plasticizers, emulsifiers, softeners, fine particles, fillers, pigments, dyes, silane coupling agents, antioxidants, surfactants, waxes, etc., if necessary.

The thickness of the adhesive layer is not particularly limited, the lower limit is preferably 1.5 μm, and the upper limit is 30 μm. When the thickness of the said adhesive layer is 1.5 micrometers or more, adhesive force will fully improve. When the thickness of the said adhesive layer is 30 micrometers or less, it can peel more easily. A more preferable lower limit of the thickness of the adhesive layer is 2.0 μm, and a more preferable upper limit is 20 μm.

The base material layer is not particularly limited, but preferably contains a polyolefin resin. The above-mentioned polyolefin resin is not particularly limited, and conventionally known polyolefin resins can be used, for example, polypropylene (PP) resin, polyethylene (PE) resin, and the like can be used. As said polypropylene resin, a homopolypropylene, atactic polypropylene, a block polypropylene etc. are mentioned, for example. As said polyethylene resin, high-pressure method low-density polyethylene, linear low-density polyethylene, high-density polyethylene etc. are mentioned, for example. Among them, from the viewpoint of transparency, rigidity, and heat resistance, polypropylene resin is preferable, and homopolypropylene is preferable. Also, a mixture of polypropylene and polyethylene is also preferred.

Within the range that does not impair the effect of the present invention, the above-mentioned base layer may contain additives such as antistatic agent, release agent, antioxidant, weather resistance agent, nucleating agent, polyolefin, polyester, polyamide, elastomer, etc. Resin modifier.

The thickness of the base material layer is not particularly limited, the lower limit is preferably 20 μm, and the upper limit is 200 μm. When the thickness of the said base material layer exists in the said range, the handleability of a surface protection film will improve. A more preferable lower limit of the thickness of the base material layer is 25 μm, and a more preferable upper limit is 188 μm.

The production method of the surface protection film of the present invention is not particularly limited, for example, the following methods can be mentioned: Extrusion lamination, extrusion coating on the substrate layer obtained by T-die forming or inflation forming The adhesive layer is laminated by a known lamination method. In addition, the following methods can also be exemplified: a method of laminating the obtained films by dry lamination after the base material layer and an adhesive layer are independently formed into films; A method of co-extruding the resin and the resin constituting the adhesive layer. Among them, the method of performing co-extrusion molding is preferable. By adjusting the forming conditions of the above-mentioned adhesive layer (surface protection film), it is easy to adjust the composition ratio and relaxation time of the above-mentioned L component at 60°C, and the above-mentioned composition ratio and relaxation time of the L component at 25°C to the above range. Specifically, in the case of performing co-extrusion molding, it is preferable to knead the raw materials of the above-mentioned adhesive layer using a twin-screw extruder in advance to prepare composite pellets (adhesive composition). Then, it is preferable to put the prepared adhesive composition into a single-screw extruder to form the above-mentioned adhesive layer. The single-screw extruder is set so that the temperature is gradually increased from the end temperature of the cylinder to 100-150°C. Increase to the front temperature 200 ~ 230 ℃. Also, it is preferable to adjust the flow path of the mold, feed block, etc. to 200-230°C. If a step of excessively increasing the heat history is added, or on the contrary, a step of insufficiently kneading the raw materials (for example, a step of extruding the raw materials in a dry blended state at a low temperature, etc.), there are components that cannot be combined with the above-mentioned L component at 60°C Ratio and relaxation time, and the ratio and relaxation time of the above-mentioned L component at 25°C are adjusted to the above-mentioned range.

The adhesive force (initial adhesive force) of the surface protection film of the present invention is high, and the adhesive force is not easy to increase over time or under high temperature, and can be peeled off without paste residue. The surface protection film of the present invention can be used to protect the surface of an adherend with a smooth surface, but it exhibits a particularly high effect when used to protect the surface of an adherend with uneven surfaces.

The surface protection film of the present invention is suitable for protecting the surface of components such as optical devices, metal plates, coated metal plates, resin plates, and glass plates. Among them, it is particularly suitable for protecting optical members having concavo-convex shapes on one or both sides of the surface, such as a sheet, a diffusion film, and the like. [Effect of Invention]

According to the present invention, it is possible to provide a surface protection film which has high adhesive force (initial adhesive force), does not easily increase in adhesive force over time or at high temperature after being attached to an adherend, and can be formed without paste residue. peel off.

Hereinafter, the embodiments of the present invention will be described in more detail, but the present invention is not limited to these embodiments.

＜Styrenic Elastomer＞ In Examples and Comparative Examples, resins 1 to 4 shown in Table 1 were used as styrene-based elastomers. In addition, the synthesis method of resin 1-3 is as follows.

(Synthesis of Resin 1) (Synthesis Example 1) 500 parts by weight of degassed and dehydrated cyclohexane, 10 parts by weight of styrene and 5 parts by weight of tetrahydrofuran were placed in a reaction vessel replaced with nitrogen, and 0.13 parts by weight of n-butyllithium was added at a temperature of 40° C. to perform temperature-rising polymerization to obtain an aromatic alkenyl polymer block (block A). After the polymerization conversion rate of the aromatic alkenyl polymer block reaches approximately 100%, the reaction liquid is cooled to 15°C, and then 85 parts by weight of 1,3-butadiene is added, and then the temperature rises to polymerize to obtain a conjugated diene Polymer block (block B). Thereby, a styrene block copolymer (1) having a structure represented by the general formula AB is obtained. After the polymerization conversion rate reaches approximately 100%, tetrachlorosilane is added as a coupling agent to perform a coupling reaction. The coupling rate at this time was 70%. After the reaction was completed, hydrogen gas was supplied at a pressure of 0.4 MPa-Gauge and left to stand for 10 minutes. Thereby, a styrene block copolymer (2) having a structure represented by the general formula (AB) ₄ C is obtained.

Thereafter, 0.03 parts by weight of diethylaluminum chloride and 0.06 parts by weight of bis(cyclopentadienyl)furfuryloxytitanium chloride were added to the reaction container and stirred. The hydrogenation reaction was started at a hydrogen supply pressure of 0.7 MPa-Gauge and a reaction temperature of 80°C, and when the absorption of hydrogen was completed, the reaction solution was returned to normal temperature and pressure, and was extracted from the reaction vessel. Thereby, the hydride (1) containing the styrene block copolymer having the structure represented by the general formula AB having the styrene content and the diblock ratio shown in Table 1, and the hydride (1) having the general formula (AB) ₄ A styrene-based elastomer that is a hydrogenated product (2) of a styrene block copolymer having a structure represented by C. A part of the polymer was taken out, and the taken out polymer was subjected to GPC analysis to obtain the weight average molecular weight (Mw).

(Synthesis of Resin 2~6) (Synthesis Examples 2-6) A styrene-based elastomer was obtained in the same manner as the synthesis of resin 1 (synthesis example 1) except that the styrene content, the coupling ratio in the coupling reaction, the diblock ratio, etc. were changed as shown in Table 1. Furthermore, the coupling ratio can be adjusted according to the type and amount of the coupling agent, etc. Thereby, in resin 2-6, the radial type styrene-type elastomer was obtained.

In addition, as the resin 7, the following commercially available products were used. Resin 7 is a linear styrene-based elastomer. DYNARON8300P (DR8300P) (styrene-ethylene-butylene-styrene block copolymer (SEBS), manufactured by JSR Corporation)

[Table 1] Resin 1 Resin 2 Resin 3 Resin 4 Resin 5 Resin 6 Resin 7 Synthesis example (product name) Synthesis Example 1 Synthesis example 2 Synthesis example 3 Synthesis Example 4 Synthesis Example 5 Synthesis Example 6 DR8300P type SEBS SEBS SEBS SEBS SEBS SEBS SEBS Styrene content [wt%] 10 10 15 11 15 10 9 Weight average molecular weight Mw[10,000] 25 twenty two 33 twenty four 13 19 15 Coupling rate[%] 70 58 90 64 100 35 60 Diblock ratio [wt%] 30 42 10 36 0 65 40 Number of branches n 4 4 4 4 4 4 2

(Example 1) (1) Manufacture of surface protection film 100 parts by weight of a block polypropylene resin (J715M, manufactured by Prime Polymer Co., Ltd.) was blended as a raw material for the substrate layer to obtain a resin composition. As a raw material for the adhesive layer, 100 parts by weight of resin 1 as a styrene-based elastomer, 15 parts by weight of an alicyclic saturated hydrocarbon resin (P125, manufactured by Arakawa Chemical Industry Co., Ltd., softening point 125 °C, the hydrogenation rate exceeds 95%) to obtain a mixture. The obtained mixture was extruded by a twin-screw extruder, and the extruded strands were cooled with water and cut to obtain a composite adhesive composition of about ϕ3 mm. Using the above-obtained resin composition as a raw material for the substrate layer, and the above-obtained adhesive composition as a raw material for the adhesive layer, co-extrusion molding was performed by the T-die method. Put the above-mentioned adhesive composition into a ϕ65 mm extruder adjusted to an end temperature of 150°C and a front end temperature of 230°C, and put the above resin composition into a ϕ115 mm extruder adjusted to an end temperature of 200°C and a front end temperature of 230°C. In a ϕ75 mm extruder, co-extrusion is carried out in the form of 3 layers from a multi-manifold die through a polymer filter and a feed block. The extruded resin was cooled by a casting roll adjusted to 30°C to form a substrate layer of 35 μm (the extrusion volume was adjusted to a layer thickness of 8 μm from an extruder of ϕ75 mm, and a thickness of a layer from an extruder of ϕ115 mm The thickness of the exit layer is about 27 μm), and the thickness of the adhesive layer is 3 μm. The film was wound up to obtain a roll-shaped surface protection film.

(2) Measurement of pulsed NMR Dissolve a part of the adhesive layer of the surface protection film in toluene, let it dry naturally, and then vacuum-dry it at 30°C to remove toluene, thereby preparing a measurement sample of about 200 mg. The measurement sample was introduced into a glass sample tube with a diameter of 10 mm (manufactured by BRUKER, product number 1824511, length 180 mm, flat bottom). The sample was set in a pulsed NMR apparatus (the minispec mq20, manufactured by BRUKER), and after being kept at 25° C. for 10 minutes, the Solid Echo method was performed. Also, after measuring at 25°C, the temperature was raised, followed by holding at 60°C for 10 minutes, and then the CPMG method was performed at 60°C. Separate the free induction decay curve waveform of spin-spin relaxation of ¹ H nuclei obtained into three curves from the three components of S component, M component and L component, and obtain the components of S component and L component ratio and relaxation time. Waveform separation was performed by using both the Gaussian type and the exponential type and performing equal fitting. Furthermore, using the analysis software "TD-NMRA (Version 4.3 Rev 0.8)" manufactured by BRUKER, according to the product manual, in the Solid Echo method at 25°C, the S component is fitted using a Gaussian type, and the M component and L component The system uses an exponential type for fitting. In the CPMG method at 60°C, the S component, the M component and the L component are all fitted using an exponential type. In addition, in the Solid Echo method, fitting is performed using a point 0.6 milliseconds before the obtained relaxation curve, and in the CPMG method, fitting is performed using all points. The following formula is used for fitting.

Among them, w1~w3 are Wei Pu modulus. The value of w1 in the Solid Echo method is 2, the values of w2 and w3 are 1, and the values of w1~w3 in the CPMG method are 1. A1 is the component ratio of S component, B1 is the component ratio of M component, C1 is the component ratio of L component, T2A represents the relaxation time of S component, T2B represents the relaxation time of M component, T2C represents the relaxation time of L component . t is time.

[measurement conditions] [CPMG Law] Scans: 256 times Recycle Delay: 0.5 sec or 5 times of T1 90-180 pulse separation: 0.4 Total number of acquired echoes: 1000

[Solid Echo method] Scans: 128 times Recycle Delay: 0.5 sec or 5 times of T1 Acquisition scale: 1 ms

(Examples 2-8, Comparative Examples 1-6) A surface protection film was obtained in the same manner as in Example 1 except that the styrene-based elastomer or tackifying resin was changed as shown in Table 2. In Example 7, although the styrene-based elastomer and tackifying resin are the same as in Example 2, the extruder for feeding the adhesive composition is changed to a ϕ45 mm extruder, and the end of the extruder is The temperature was changed to 190°C, the front end temperature was changed to 230°C, and the temperature of the casting roll was changed to 40°C.

＜Evaluation＞ The following evaluations were performed on the surface protection films obtained in Examples 1-8 and Comparative Examples 1-6. The results are shown in Table 2.

(1) Determination of initial adhesion A surface protection film with a width of 25 mm was attached to cover the adherend (a sheet with a distance between peaks of 24 μm) to prepare a test piece. Attaching is carried out by pressing at a speed of 300 mm/min using a 2 kg pressing rubber roller in an environment of 23°C and a relative humidity of 50%RH. The obtained test piece was placed in an environment of 23° C. and a relative humidity of 50% RH for 30 minutes. After placing, peel off the surface protective film from the adherend along the direction of 180° at a tensile speed of 300 mm/min, and measure the initial adhesion. However, in Comparative Example 3, the surface protection film was in a state of floating from the adherend, and the initial adhesive force could not be measured.

(2) Determination of adhesion after 1 week (1W) at 50°C The test piece obtained in the same manner as in (1) above was left to stand in a temperature environment of 50°C for 1 week (1W). After standing, the test piece was taken out to room temperature, and after standing for 60 minutes, the surface protective film was peeled off from the bonded body along the direction of 180° at a tensile speed of 300 mm/min, and measured after 1 week (1W) at 50°C Adhesion. However, in Comparative Examples 1 and 3, the surface protective film was in a state of floating from the adherend, and the adhesive force after 1 week (1W) at 50°C could not be measured.

(3) Judgment of adhesion Based on the measurement results of the initial adhesive force, judge according to the following criteria. ◎: 6 gf/25 mm or more and 8 gf/25 mm or less ○: More than 5 gf/25 mm and less than 6 gf/25 mm, or more than 8 gf/25 mm and less than 12.5 gf/25 mm △: More than 4 gf/25 mm and less than 5 gf/25 mm, or more than 12.5 gf/25 mm and less than 15 gf/25 mm ×: Less than 4 gf/25 mm or greater than 15 gf/25 mm Moreover, based on the measurement result of the adhesive force after 1 week (1W) at 50 degreeC, it judged according to the following criteria. ◎: 6 gf/25 mm or more and 10 gf/25 mm or less ○: More than 5 gf/25 mm and less than 6 gf/25 mm, or more than 10 gf/25 mm and less than 15 gf/25 mm △: More than 4 gf/25 mm and less than 5 gf/25 mm, or more than 15 gf/25 mm and less than 20 gf/25 mm ×: less than 4 gf/25 mm or greater than 20 gf/25 mm

(4) Evaluation of paste residue After peeling the surface protection film from the adherend in (2) above, the adherend was confirmed, and the presence or absence of paste residue was evaluated using a laser microscope (manufactured by Keyence Corporation, VK-X100). Evaluation was performed according to the following criteria. ○: No paste remains ×: Visible paste residue

[Table 2] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Comparative Example 5 Comparative example 6 Adhesive layer [parts by weight] Styrenic elastomer Resin 1 100 100 100 - - - 100 - 100 100 - - - - Resin 2 - - - 100 100 - - - - - - - - - Resin 3 - - - - - 100 - - - - - - - - Resin 4 - - - - - - - 100 - - - - - - Resin 5 - - - - - - - - - - - - 100 - Resin 6 - - - - - - - - - - - - - 100 Resin 7 - - - - - - - - - - 100 100 - - Tackifying resin P125 15 20 40 20 40 20 20 20 10 50 - 20 20 20 Adhesive layer thickness [μm] 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Pulse NMR measurement 60℃ L component Composition ratio 6.0% 0.6% 0.4% 8.1% 6.9% 1.0% 0.7% 6.5% 10.1% 0.6% 6.4% 2.3% 4.8% 4.3% relaxation time [ms] 28.1 58.4 71.0 43.2 70.7 47.9 43.3 37.6 8.4 84.4 12.0 19.6 21.1 74.1 S component Composition ratio 48.0% 51.1% 58.5% 47.0% 52.1% 53.5% 50.9% 59.4% 36.5% 62.2% 40.6% 44.3% 66.1% 23.2% relaxation time [ms] 0.65 0.65 0.53 0.60 0.51 0.71 0.64 0.69 0.57 0.49 0.56 0.60 0.39 0.36 25°C L component Composition ratio 61.0% 55.9% 40.5% 59.5% 50.6% 43.8% 56.5% 52.8% 67.6% 27.0% 70.7% 72.9% 45.8% 61.4% relaxation time [ms] 0.32 0.30 0.23 0.26 0.23 0.28 0.27 0.37 0.33 0.19 0.37 0.35 0.68 0.81 evaluate Adhesion [gf/25 mm] initial adhesion 5.5 6.2 9.4 8 11 4.3 7.5 5.6 2.1 14 - 2.7 2.9 13.2 determination ○ ◎ ○ ◎ ○ △ ◎ ○ x △ x x x △ Adhesion after 1W at 50℃ 6.2 6.6 11.7 10.9 13.1 6.8 11.3 9.7 - 25 - 7.4 5.9 18 determination ◎ ◎ ○ ○ ○ ◎ ○ ◎ x x x ◎ ○ △ paste residue ○ ○ ○ ○ ○ ○ ○ ○ - x - ○ ○ x [Industrial availability]

According to the present invention, it is possible to provide a surface protection film which has high adhesive force (initial adhesive force), does not easily increase in adhesive force over time or at high temperature after being attached to an adherend, and can be formed without paste residue. peel off.

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Claims (7)

A surface protection film, which has a substrate layer and an adhesive layer, and is characterized in that: The above-mentioned adhesive layer is measured by the CPMG method at 60°C using pulsed NMR. The component ratio of the L component measured by the Echo method is 30% to 65%, and the relaxation time is 0.2 milliseconds to 0.4 milliseconds. The surface protection film according to claim 1, wherein the composition ratio of the S component measured by the CPMG method at 60° C. using the pulsed NMR of the above-mentioned adhesive layer is 45% or more, and the relaxation time is 0.4 milliseconds or more and 0.8 milliseconds the following. The surface protection film according to claim 1 or 2, wherein the adhesive layer contains a styrene-based elastomer. The surface protection film as claimed in item 3, wherein, the above-mentioned styrene-based elastomer system styrene-based elastomer (I), the styrene-based elastomer (I) contains a styrene block copolymer having a structure represented by the general formula AB or its hydrogenated product (1), and a styrene block copolymer or its hydrogenated product (2) having a structure represented by general formula ABA or general formula (AB) _n C, the above-mentioned styrene block copolymer or its The content of the hydrogenated product (1) in 100% by weight of the above-mentioned styrene-based elastomer (I) is not less than 15% by weight and not more than 50% by weight, and the above-mentioned styrene block copolymer or its hydrogenated product (2) is contained in the above-mentioned styrene-based elastomer (I). The vinyl elastomer (I) contains 100% by weight of 50% by weight or more and 85% by weight or less, A: aromatic alkenyl polymer block, B: conjugated diene polymer block, C: from Components of the coupling agent, n: an integer of 2 or more. The surface protection film according to claim 3 or 4, wherein the adhesive layer further contains an tackifying resin, and the content of the tackifying resin is not less than 12 parts by weight and not more than 45 parts by weight relative to 100 parts by weight of the above-mentioned styrene-based elastomer . The surface protection film according to claim 4, wherein n is 4 in the above-mentioned styrene-based elastomer (I). The surface protection film according to claim 1, 2, 3, 4, 5, or 6, wherein the component ratio of the L component measured by the CPMG method using pulsed NMR at 60° C. is 6.5% or less in the adhesive layer, The relaxation time is not less than 30 milliseconds and not more than 70 milliseconds.