KR20240011658A - surface protection film - Google Patents

Abstract

The purpose of the present invention is to provide a surface protection film that has high adhesive strength (initial adhesive strength), is unlikely to increase in adhesive strength over time or at high temperatures after being attached to an adherend, and can be peeled off without glue remaining. The present invention is a surface protection film having a base material layer and an adhesive layer, wherein the adhesive layer has a component ratio of the L component obtained by measurement by CPMG method at 60°C using pulse NMR and a relaxation time of 25%. Millisecond or more and 80 millisecond or less, the component ratio of the L component obtained by measurement with the Solid Echo method at 25°C using pulse NMR is 30% or more and 65% or less, and the relaxation time is 0.2 millisecond or more and 0.4 millisecond. The following is a surface protection film.

Description

surface protection film

The present invention relates to a surface protection film that has high adhesion (initial adhesion) and, after being attached to an adherend, is unlikely to increase in adhesion over time or at high temperatures, and can be peeled off without glue remaining.

Conventionally, in order to protect the surface of members such as optical devices, metal plates, painted metal plates, resin plates, and glass plates, a surface protection film (generally referred to as a protection tape) has a base material layer and an adhesive layer laminated on one side of the material. etc.) is widely used (for example, Patent Documents 1 to 3). Among them, a surface protection film is used to protect the surface of the optical member for liquid crystal display. There are optical members, such as prism sheets, diffusion films, etc., that have an uneven shape on one or both surfaces. In order to avoid damaging the uneven shape, the surface is protected with a surface protection film before use of the optical member. there is.

Surface protection films are required to have high adhesive strength depending on the application. For example, when adhering to an adherend whose surface has an uneven shape, a large contact area cannot be obtained and peeling is likely to occur at the interface between the adherend and the surface protection film. In such applications, particularly high adhesive strength is required for the surface protection film.

Generally, in order to improve adhesive strength, it is effective to control the composition or structure of the base resin used in the adhesive layer to make it a flexible base resin, or to increase the compounding amount of the tackifier resin in the adhesive layer. However, such an adhesive layer, especially when the adherend has an uneven shape on the surface, suffers from the problem of an increase in adhesive force due to an increase in the contact area between the adherend and the adhesive layer over time or under high temperature, or so-called adhesion growth. It is known that this occurs, making peeling difficult or causing residual glue.

Japanese Patent Publication No. 1-129085 Japanese Patent Publication No. 6-1958 Japanese Patent Publication No. 8-12952

The purpose of the present invention is to provide a surface protection film that has high adhesive strength (initial adhesive strength), is unlikely to increase in adhesive strength over time or at high temperatures after being attached to an adherend, and can be peeled off without glue remaining.

This disclosure 1 is a surface protection film having a base material layer and an adhesive layer, wherein the adhesive layer has a component ratio of the L component obtained by measurement by CPMG method at 60°C using pulse NMR and a relaxation time of 25%. Millisecond or more and 80 millisecond or less, the component ratio of the L component obtained by measurement with the Solid Echo method at 25°C using pulse NMR is 30% or more and 65% or less, and the relaxation time is 0.2 millisecond or more and 0.4 millisecond. The following is a surface protection film.

In the present disclosure 2, the surface of the present disclosure 1 has a component ratio of the S component of 45% or more and a relaxation time of 0.4 millisecond or more and 0.8 millisecond or less, obtained by measuring the pressure-sensitive adhesive layer by CPMG method at 60°C using pulse NMR. It is a protective film.

This disclosure 3 is the surface protection film of this disclosure 1 or 2 in which the adhesive layer contains a styrene-based elastomer.

This disclosure 4 provides that the styrene-based elastomer is a styrene block copolymer having a structure represented by the general formula AB or a hydrogenated product thereof (1), and a styrene block having a structure represented by the general formula ABA or general formula (AB) _n C A styrene-based elastomer (I) containing a copolymer or its hydrogenated product (2), wherein the content of the styrene block copolymer or its hydrogenated product (1) in 100% by weight of the styrene-based elastomer (I) is 15% by weight. % or more and 50% by weight or less, and the content of the styrene block copolymer or its hydrogenated substance (2) in 100% by weight of the styrene-based elastomer (I) is 50% by weight or more and 85% by weight or less. It is a surface protection film.

A: Aromatic alkenyl polymer block

B: Conjugated diene polymer block

C: Component derived from coupling agent

n: integer of 2 or more

This disclosure 5 is the present disclosure 3, wherein the adhesive layer further contains a tackifying resin, and the content of the tackifying resin is 12 parts by weight or more and 45 parts by weight or less with respect to 100 parts by weight of the styrene-based elastomer. 4 It is a surface protection film.

This disclosure 6 is the surface protection film of this disclosure 4 in which n is 4 in the styrene-based elastomer (I).

This disclosure 7 is the present disclosure 1, wherein the pressure-sensitive adhesive layer has a component ratio of the L component obtained by measurement by the CPMG method at 60°C using pulse NMR and a relaxation time of 30 milliseconds or more and 70 milliseconds or less. It is a surface protection film of 2, 3, 4, 5 or 6.

The present invention is described in detail below.

The present inventors analyzed the adhesive layer of a surface protection film having a base material layer and an adhesive layer using pulse NMR that measures ¹ H nuclei. In pulse NMR, the obtained free-induction decay curve of spin-spin relaxation of the ¹ H nucleus is separated into a plurality of components, and the “relaxation time” of each component is obtained, thereby evaluating the molecular mobility of the component.

The present inventors, for the adhesive layer, measured the component ratio and relaxation time of the L component obtained by measuring by the CPMG method at 60°C using pulse NMR, and the L obtained by measuring by the Solid Echo method at 25°C using pulse NMR. We reviewed adjusting the component ratio and relaxation time to a specific range. The present inventors found that by using such an adhesive layer, the adhesive strength (initial adhesive strength) at the time of sticking can be increased, while the adhesive strength can be suppressed from increasing over time or under high temperatures, and glue residue can be suppressed. The present invention has been completed.

The surface protection film of this invention is a surface protection film which has a base material layer and an adhesive layer. The pressure-sensitive adhesive layer has a component ratio of the L component of 10% or less, and a relaxation time of 25 milliseconds or more and 80 milliseconds or less, as measured by CPMG method at 60°C using pulse NMR.

Here, the “L component” obtained by measurement using pulse NMR refers to the free induction decay curve of spin-spin relaxation of ^{the 1} H nucleus obtained by measurement using pulse NMR, which is a waveform divided into three components in the order of shortest relaxation time. It refers to the component with the longest relaxation time when separated. Separation of the waveform into three components (S component, M component, and L component, respectively, in order of decreasing relaxation time) is performed by analyzing the free induction decay curve using the least squares method.

“Relaxation time” is the time it takes for the electron spin to return from the excited state to the ground state after applying a magnetic field, and the longer the “relaxation time”, the higher the molecular mobility. In other words, the S component is a hard component with relatively low molecular mobility, with the shortest relaxation time and immediate attenuation of magnetization intensity. The L component has the longest relaxation time, takes time to decay in magnetization intensity, and is a soft component with relatively high molecular mobility. The M component is a component that has a relaxation time and molecular mobility intermediate between the S component and the L component.

If the component ratio of the L component at 60°C is 10% or less, it means that there are few components with relatively high molecular mobility at high temperatures, and the adhesive strength of the adhesive layer is difficult to increase over time or even at high temperatures, so that there is no glue remaining. It can be peeled off. The preferable upper limit of the component ratio of the 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 a preferable lower limit is 0.1% and a more preferable lower limit is 0.3%.

If the relaxation time of the L component at 60°C is 25 milliseconds or more, it means that the molecular mobility of the L component, which has relatively high molecular mobility at 60°C, is above a certain level, and the storage modulus of the adhesive layer at high temperature becomes too high. This can prevent it from leading to peeling. If the relaxation time of the L component at 60°C is 80 milliseconds or less, it means that the molecular mobility of the L component, which has relatively high molecular mobility at 60°C, is suppressed below a certain level, and the pressure-sensitive adhesive layer is not exposed to excessive blood pressure. Since application and diffusion to the complex surface can be prevented, the adhesive layer is unlikely to increase in adhesive strength over time or at high temperatures, and can be peeled off without glue remaining. The preferable lower limit of the relaxation time of the L component at 60°C is 26 milliseconds, the more preferable lower limit is 28 milliseconds, the more preferable lower limit is 30 milliseconds, the preferable upper limit is 75 milliseconds, and the more preferable upper limit is 70 milliseconds. .

The pressure-sensitive adhesive layer preferably has a component ratio of the S component obtained by measuring by CPMG method at 60°C using pulse NMR and has a relaxation time of 0.4 millisecond or more and 0.8 millisecond or less.

If the component ratio of the S component at 60°C is 45% or more, the adhesive strength of the adhesive layer is less likely to increase over time or even at high temperatures, and can be peeled off without glue remaining. A 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 preferable upper limit is 65% and the more preferable upper limit is 60%.

If the relaxation time of the S component at 60°C is within the above range, the adhesive strength of the adhesive layer is less likely to increase over time or even at high temperatures, and can be peeled off without glue remaining. The more preferable lower limit of the relaxation time of the S component at 60°C is 0.45 milliseconds, the more preferable upper limit is 0.75 milliseconds, the more preferable lower limit is 0.50 milliseconds, and the more preferable upper limit is 0.70 milliseconds.

The pressure-sensitive adhesive layer has a component ratio of the L component of 30% or more and 65% or less, and a relaxation time of 0.2 millisecond or more and 0.4 millisecond or less, as measured by the Solid Echo method at 25°C using pulse NMR.

If the component ratio of the L component at 25°C is within the above range, the adhesive layer can develop sufficient adhesive strength to adhere even to an adherend having an uneven shape on the surface. The preferable lower limit of the component ratio of the L component at 25°C is 35%, the preferable upper limit is 63%, the more preferable lower limit is 40%, the more preferable upper limit is 60%, and the more preferable lower limit is 45%.

If the relaxation time of the L component at 25°C is 0.2 milliseconds or more, it means that the molecular mobility of the L component, which has relatively high molecular mobility at 25°C, is above a certain level, and the pressure-sensitive adhesive layer has a surface having an uneven shape. It can sufficiently follow the surface of the complex and have sufficient adhesion to the adherend. If the relaxation time of the L component at 25°C is 0.4 milliseconds or less, it means that the molecular mobility of the L component, which has relatively high molecular mobility at 25°C, is suppressed below a certain level, and the storage at room temperature of the pressure-sensitive adhesive layer By preventing the elastic modulus from being excessively lowered, it is possible to prevent excessively high adhesive force from being developed by following the adherend more than necessary. The preferable lower limit of the relaxation time of the L component at 25°C is 0.21 milliseconds, the preferable upper limit is 0.38 milliseconds, the more preferable lower limit is 0.22 milliseconds, the more preferable upper limit is 0.35 milliseconds, and the more preferable lower limit is 0.24 milliseconds. am.

In addition, pulse NMR measurement is performed using a pulse NMR device (e.g., the minispec mq20, manufactured by BRUKER, etc.) and analysis software (e.g., TD-NMRA, manufactured by BRUKER, etc.) prepared from the adhesive layer. The measurement can be performed on the sample at a predetermined temperature. The measurement sample can be prepared by dissolving a part of the adhesive layer in toluene, drying it naturally, and then vacuum drying it at 30°C to remove toluene.

The method of 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 range is not particularly limited, for example, of the pressure-sensitive adhesive layer. Examples include a method of using a styrene-based elastomer as a base resin, a method of adjusting the structure, composition, weight average molecular weight (Mw), etc. of the styrene-based elastomer. In addition, a method of mixing a tackifying resin into the adhesive layer, a method of adjusting the type, physical properties (for example, softening point), and mixing amount of the tackifying resin can also be mentioned. In addition, a method of adjusting the molding conditions of the adhesive layer can also be mentioned.

The base resin constituting the adhesive layer is not particularly limited, and examples include styrene-based elastomer, acrylic-based elastomer, urethane-based elastomer, and olefin-based elastomer. Among them, it is easy to adjust the adhesive force (initial adhesive force) obtained as a surface protection film, and the molecular mobility of the adhesive layer can be relatively freely adjusted by selecting the molecular structure such as styrene content or additives such as tackifier. In this regard, styrene-based elastomer is preferable.

The styrene-based elastomer is not particularly limited and includes, for example, styrene-ethylenepropylene-styrene block copolymer (SEPS), hydrogenated styrene butadiene rubber (HSBR), styrene-ethylenebutylene-styrene block copolymer (SEBS), styrene. -Ethylenepropylene block copolymer (SEP), styrene-ethylenebutylene 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), etc.

The weight average molecular weight (Mw) of the styrene-based elastomer is not particularly limited, but the preferred lower limit is 50,000 and the preferred upper limit is 400,000. If the weight average molecular weight (Mw) is 50,000 or more, the storage modulus of the adhesive layer at high temperature becomes higher, the adhesive strength is less likely to increase over time or even at high temperature, and peeling can be performed without glue remaining. If the weight average molecular weight (Mw) is 400,000 or less, the storage elastic modulus of the pressure-sensitive adhesive layer at room temperature does not become too high, the adhesion when sticking to an adherend becomes higher, and the adhesive force (initial adhesive force) becomes higher. The more preferable lower limit of the weight average molecular weight (Mw) is 80,000, and the more preferable upper limit is 350,000.

In addition, the weight average molecular weight (Mw) can be measured by the following method.

The sample solution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 ㎛). The obtained filtrate was supplied to a gel permeation chromatograph (e.g., 2690 Separations Model, manufactured by Waters), GPC measurement was performed under the conditions of a sample flow rate of 1 milliliter/min and a column temperature of 40°C, and the polystyrene equivalent molecular weight of the sample was determined. is measured to obtain the weight average molecular weight (Mw). As a column, for example, GPC KF-806L (manufactured by Showa Denko) is used, and as a detector, a differential refractometer is used.

In addition, the styrene-based elastomer includes a styrene block copolymer having a structure represented by the general formula AB or a hydrogenated product thereof (1), and a styrene block copolymer having a structure represented by the general formula ABA or general formula (AB) _n C. Alternatively, styrene-based elastomer (I) containing the hydrogenated substance (2) is also preferable. By using the styrene-based elastomer (I), it becomes 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 range.

A: Aromatic alkenyl polymer block

B: Conjugated diene polymer block

C: Component derived from coupling agent

n: integer greater than or equal to 2

The styrene block copolymer having the structure represented by the general formula A-B or its hydrogenated product (1) is a linear styrene block copolymer having an aromatic alkenyl polymer block represented by the above A and a conjugated diene polymer block represented by the above B, or It's the hydrogen additive.

The styrene block copolymer having a structure represented by the general formula ABA or its hydrogenated product (2) is a linear styrene block copolymer having an aromatic alkenyl polymer block represented by A and a conjugated diene polymer block represented by B. It is a hydrogen additive. The styrene block copolymer having a structure represented by the general formula (AB) _n C or a hydrogenated product thereof (2) is a styrene block copolymer having a structure represented by the general formula AB or a hydrogenated product thereof centered on a coupling agent. (1) This is a branched (radial) styrene block copolymer having multiple radially protruding structures or a hydrogenated product thereof. However, when n = 2, it becomes linear.

The aromatic alkenyl polymer block represented by A has a repeating unit derived from an aromatic alkenyl compound.

Examples of the aromatic alkenyl compounds include styrene, tert-butylstyrene, α-methylstyrene, p-methylstyrene, p-ethylstyrene, divinylbenzene, 1,1-diphenylethylene, vinylnaphthalene, and vinyl. Anthracene, N,N-diethyl-p-aminoethylstyrene, vinylpyridine, etc. can be mentioned. Among them, styrene is preferable because it is easy to obtain industrially.

The content of the repeating unit derived from the aromatic alkenyl compound in the aromatic alkenyl polymer block represented by A is not particularly limited, but the preferable lower limit is 50% by weight, the preferable upper limit is 100% by weight, and the more preferable lower limit is 70% by weight. It is weight%.

When the aromatic alkenyl polymer block represented by A contains repeating units derived from compounds other than the repeating units derived from the aromatic alkenyl compound, blocks containing repeating units derived from such other compounds are specifically limited. Examples include conjugated diene polymer, ethylene polymer, and propylene polymer.

The conjugated diene polymer block represented by B has a repeating unit derived from a conjugated diene compound.

Examples of the conjugated diene compounds 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 individually, or may use 2 or more types together. Among them, 1,3-butadiene and isoprene are preferable because they have high polymerization reactivity and are easy to obtain industrially.

The content of the repeating unit derived from the conjugated diene compound in the conjugated diene polymer block represented by B is not particularly limited, but the preferable lower limit is 50% by weight, the preferable upper limit is 100% by weight, and the more preferable lower limit is 70% by weight. am.

When the conjugated diene polymer block represented by B contains repeating units derived from compounds other than the repeating units derived from the conjugated diene compound, the block having repeating units derived from such other compounds is not particularly limited. , for example, aromatic alkenyl polymer, ethylene polymer, propylene polymer, etc.

The coupling agent that serves as the raw material for the component derived from the coupling agent represented by C is a polyfunctional compound that radially bonds the linear styrene block copolymer, that is, the styrene block copolymer or its hydrogenated product (1).

Examples of the coupling agent include silane compounds such as halogenated silanes and alkoxysilanes, tin compounds such as tin halides, epoxy compounds such as polycarboxylic acid esters and epoxidized soybean oil, and acrylic esters such as pentaerythritol tetraacrylate. and divinyl compounds such as epoxysilane and divinylbenzene. More specific examples include, for example, trichlorosilane, tribromosilane, tetrachlorosilane, tetrabromosilane, methyltrimethoxysilane, ethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, tetrabromosilane, Examples include methoxysilane, tetraethoxysilane, tetrachlorotin, and diethyl adipate.

n is not particularly limited as long as it is an integer of 2 or more, but is preferably 3 or more. When n is 3 or more, the moldability of the adhesive layer is easy to maintain even when the molecular weight of the styrene-based elastomer (I) is increased to adjust the relaxation time of the L component at 60°C to the above range. It is particularly preferable that n is 4 because 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 range. Additionally, when n is 3, it is also called a three-branch type, and when n is 4, it is also called a four-branch type.

The styrene-based elastomer (I) 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 range, as follows. It is preferable to have the hydrogenation rate, weight average molecular weight, diblock ratio, styrene content, butylene content, coupling rate, etc. in the ranges described.

When the styrene block copolymer or its hydrogenated product (1) or the styrene block copolymer or its hydrogenated product (2) is a hydrogenated product, the hydrogenated product may be a partially hydrogenated product or a fully hydrogenated product. Among them, preferably 80% or more, more preferably 90% or more, and still more preferably 95% or more of the double bonds (unsaturated bonds) of the repeating unit derived from the conjugated diene compound are converted to saturated bonds by hydrogenation. A converted hydrogenated product is preferred.

In addition, the rate of hydrogen addition (hydrogen addition rate) means the hydrogen addition 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 preferred lower limit is 40,000 and the preferred upper limit is 150,000. When the weight average molecular weight (Mw1) is 40,000 or more, the weight average molecular weight (Mw2) of the styrene block copolymer or its hydrogenated product (2) also increases, and the storage modulus of the adhesive layer at high temperature becomes higher, so the time The adhesive strength is less likely to increase over time or at high temperatures, and can be peeled off without glue remaining. When the weight average molecular weight (Mw1) is 150,000 or less, the weight average molecular weight (Mw2) of the styrene block copolymer or its hydrogenated product (2) does not become too high, and the storage modulus of the adhesive layer at room temperature does not become too high. Since there is no movement, the adhesion when sticking to the adherend becomes higher, and the adhesive force (initial adhesive force) becomes higher. The more preferable lower limit of the weight average molecular weight (Mw1) is 50,000, the more preferable upper limit is 140,000, the more preferable lower limit is 60,000, and the more preferable upper limit is 120,000.

The weight average molecular weight (Mw2) of the styrene block copolymer or its hydrogenated product (2) is preferably 2.5 times or more than the weight average molecular weight (Mw1) of the styrene block copolymer or its hydrogenated product (1). If the weight average molecular weight (Mw2) is 2.5 times or more than the weight average molecular weight (Mw1), the storage modulus of the pressure-sensitive adhesive layer at high temperature becomes higher, the adhesive strength is less likely to increase over time or even at high temperature, and the adhesive layer becomes more adhesive. It can be peeled off without residue. In addition, in this specification, when the weight average molecular weight (Mw2) is 2.5 times or more than the weight average molecular weight (Mw1), the styrene-based elastomer (I) is said to be radial type. When the weight average molecular weight (Mw2) is less than 2.5 times the weight average molecular weight (Mw1), the styrene-based elastomer (I) is said to be linear. The weight average molecular weight (Mw2) is more preferably 2.7 times or more, and even more preferably 3.0 times or more, than the weight average molecular weight (Mw1).

The overall weight average molecular weight of the styrene-based elastomer (I) is not particularly limited, but the preferred lower limit is 50,000 and the preferred upper limit is 400,000. If the weight average molecular weight is 50,000 or more, the storage modulus of the adhesive layer at high temperature becomes higher, the adhesive strength is less likely to increase over time or even at high temperature, and peeling can be performed without glue remaining. If the weight average molecular weight is 400,000 or less, the storage elastic modulus of the pressure-sensitive adhesive layer at room temperature does not become too high, the adhesion when affixed to an adherend becomes higher, and the adhesive force (initial adhesive force) becomes higher. The more preferable lower limit of the weight average molecular weight is 80,000, the more preferable upper limit is 350,000, the more preferable lower limit is 100,000, and the more preferable upper limit is 320,000.

The content (diblock ratio) of the styrene block copolymer or its hydrogenated product (1) in 100% by weight of the styrene-based elastomer (I) has a preferable lower limit of 15% by weight and a preferable upper limit of 50% by weight. If the content of the styrene block copolymer or its hydrogenated product (1) is 15% by weight or more, the storage modulus of the pressure-sensitive adhesive layer at room temperature does not become excessively high, and the adhesion when sticking to the adherend becomes higher, resulting in higher adhesive strength. (Initial adhesion) becomes higher. If the content of the styrene block copolymer or its hydrogenated product (1) is 50% by weight or less, the storage modulus of the adhesive layer at high temperature becomes higher, the adhesive strength is less likely to increase over time or even at high temperature, and the adhesive layer becomes more adhesive. It can be peeled off without residue. The more preferable lower limit of the content of the styrene block copolymer or its hydrogenated product (1) is 18 wt%, the more preferable upper limit is 47 wt%, the more preferable lower limit is 20 wt%, and the more preferable upper limit is 45 wt%.

On the other hand, the content of the styrene block copolymer or its hydrogenated product (2) in 100 weight% of the styrene-based elastomer (I) has a preferable lower limit of 50 weight%, a preferable upper limit of 85 weight%, and a more preferable lower limit. 53% by weight, and a more preferable upper limit is 72% by weight.

In addition, 100% by weight of the styrene-based elastomer (I) contains, in addition to the styrene block copolymer or its hydrogenated product (1) and the styrene block copolymer or its hydrogenated product (2), other components. You can stay.

Additionally, the diblock ratio can be calculated from the peak area ratio of each copolymer measured by gel permeation chromatography (GPC) method.

The weight ratio of the aromatic alkenyl polymer block represented by A and the conjugated diene polymer block represented by B in the entire styrene-based elastomer (I) is not particularly limited. The content of the conjugated diene polymer block represented by B in the total of the aromatic alkenyl polymer block represented by A and the conjugated diene polymer block represented by B in the entire styrene-based elastomer (I) has a preferable lower limit. 35% by weight, and the preferred upper limit is 95% by weight. When the content of the conjugated diene polymer block represented by B is within the above range, the moldability of the adhesive layer is further improved, and the adhesiveness when sticking to an adherend is further improved, and the adhesive strength (initial adhesive strength) is increased. , the adhesive strength is less likely to increase over time or at high temperatures, and can be peeled off without glue remaining, and the followability to the adherend is also further improved. The more preferable lower limit of the content of the conjugated diene polymer block represented by B is 45% by weight, and the more preferable upper limit is 87% by weight.

Types of the styrene-based elastomer (I) include styrene-ethylenebutylene-styrene block copolymer (SEBS) type, styrene-ethylenepropylene-styrene block copolymer (SEPS) type, and styrene-isobutylene-styrene block copolymer type. A composite (SIBS) type etc. are mentioned.

In addition, for example, the type of the styrene-based elastomer (I) being SEBS type means that the styrene block copolymer or its hydrogenated product (1) and the styrene block copolymer or its hydrogenated product (2) are styrene. It means having a repeating unit derived from ethylene, a repeating unit derived from ethylene, and a repeating unit derived from butylene. That is, the aromatic alkenyl polymer block represented by A is a block having a repeating unit derived from styrene, and the conjugated diene polymer block represented by B (its hydrogenated product) has a repeating unit derived from ethylene and a repeat derived from butylene. This means that it is a block with a unit.

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, but the preferable lower limit is 5 weight. %, the preferable upper limit is 30% by weight. When the styrene content is within the above range, the moldability of the adhesive layer is further improved, adhesion when attached to an adherend is further improved, and adhesive strength (initial adhesive strength) is increased, while also increasing over time or at high temperature. It is difficult for the adhesive strength to increase, so it can be peeled off without glue remaining, and the followability to the adherend is also improved. The more preferable lower limit of the styrene content is 7% by weight, and the more preferable upper limit is 20% by weight.

When the styrene-based elastomer (I) has a butylene-derived repeating unit, the content (butylene content) of the butylene-derived repeating unit in the entire styrene-based elastomer (I) is not particularly limited, but is preferably a lower limit. Silver is 30% by weight, and the preferred upper limit is 90% by weight. When the butylene content is within the above range, the moldability of the pressure-sensitive adhesive layer is further improved, adhesion when affixed to an adherend is further improved, and adhesive strength (initial adhesive strength) is increased, while also increasing over time or at high temperatures. It is difficult for the adhesive strength to increase under pressure, so it can be peeled off without glue remaining, and the followability to the adherend is also improved. The more preferable lower limit of the butylene content is 35% by weight, and the more preferable upper limit is 80% by weight.

The method for producing the styrene-based elastomer (I) is not particularly limited, and examples include the following methods.

First, step (a) of synthesizing the aromatic alkenyl polymer block represented by A is performed. Next, step (b) of synthesizing styrene block copolymer (1) having a structure represented by general formula AB is performed by polymerizing a conjugated diene compound to the aromatic alkenyl polymer block represented by A. Next, the obtained styrene block copolymer (1) having a structure represented by the general formula AB is subjected to a coupling reaction using a coupling agent to obtain a styrene block copolymer having a structure represented by the general formula ABA or general formula (AB) _n C. (2) Carry out step (c) to obtain. The coupling rate at this time is not particularly limited, but the diblock ratio (content of the styrene block copolymer or its hydrogenated product (1) in 100% by weight of the styrene-based elastomer (I)) is adjusted to the range described above. From this point of view, the preferable lower limit is 50% and the preferable upper limit is 97%. The more preferable lower limit of the coupling ratio is 55%, the more preferable upper limit is 95%, the more preferable lower limit is 58%, the more preferable upper limit is 90%, the still more preferable lower limit is 60%, and the still more preferable upper limit is 85%. If necessary, step (d) of adding hydrogen to the styrene block copolymer (1) and styrene block copolymer (2) is performed.

It is preferable that the adhesive layer further contains a tackifying resin. By adjusting the type, physical properties (e.g., softening point), blending amount, etc. of the tackifying resin, 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. It becomes easy to adjust the time to the above range.

The tackifying resin is not particularly limited, but the softening point is preferably 80°C or higher, and more preferably 90°C or higher and 140°C or lower.

Examples of the tackifying resin include petroleum resins such as aliphatic copolymers, aromatic copolymers, aliphatic aromatic copolymers, and alicyclic copolymers, coumarone-indene resins, terpene resins, terpene phenol resins, and polymerized rosin. rosin-based resins, (alkyl)phenol-based resins, xylene-based resins, and hydrogenated products thereof. Moreover, you may use a commercially available tackifying resin as a mixture with polyolefin resin. These tackifying resins may be used individually, or two or more types may be used together. Among these, it is preferable that the tackifying resin is a hydrogenated substance because the adhesive strength of the adhesive layer is unlikely to increase over time or even under high temperatures, and can be peeled off without glue remaining.

The content of the tackifying resin is not particularly limited, but the preferable lower limit is 12 parts by weight and the preferable upper limit is 45 parts by weight relative to 100 parts by weight of the base resin such as the styrene-based elastomer. When the content of the tackifying resin is 12 parts by weight or more, the storage modulus of the pressure-sensitive adhesive layer is lowered, thereby improving followability to the adherend, and the component ratio of the S component at 25° C. is increased, thereby improving the elasticity of the pressure-sensitive adhesive layer. Molecular mobility is suppressed, preventing the adhesion from following the adherend more than necessary and increasing the adhesion. If the content of the tackifying resin is 45 parts by weight or less, the relaxation time of the L component at 60°C does not become excessively large, the adhesive strength of the adhesive layer is unlikely to increase over time or even at high temperatures, and peeling occurs without glue remaining. can do. The more preferable lower limit of the content of the 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 adhesive layer may further contain known additives such as adhesion regulators, plasticizers, emulsifiers, softeners, fine particles, fillers, pigments, dyes, silane coupling agents, antioxidants, surfactants, and waxes, if necessary.

The thickness of the adhesive layer is not particularly limited, but the preferred lower limit is 1.5 μm and the preferred upper limit is 30 μm. If the thickness of the adhesive layer is 1.5 μm or more, the adhesive strength is sufficiently high. If the thickness of the adhesive layer is 30 μm or less, it can be peeled off 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 polyolefin resin. The polyolefin resin is not particularly limited, and conventionally known polyolefin resins can be used, for example, polypropylene (PP) resin, polyethylene (PE) resin, etc.

Examples of the polypropylene resin include homopolypropylene, random polypropylene, and block polypropylene. Examples of the polyethylene resin include high-pressure low-density polyethylene, linear low-density polyethylene, and high-density polyethylene. Among them, polypropylene resin is preferable from the viewpoint of transparency, rigidity, and heat resistance, and homopolypropylene is preferable. Additionally, a mixture of polypropylene and polyethylene is also preferred.

The base material layer may contain additives such as antistatic agents, mold release agents, antioxidants, weathering agents, and crystal nucleating agents, and resin modifiers such as polyolefins, polyesters, polyamides, and elastomers, within the range that does not impair the effect of the present invention. do.

The thickness of the base layer is not particularly limited, but the preferred lower limit is 20 μm and the preferred upper limit is 200 μm. When the thickness of the base layer is within the above range, the handleability of the surface protection film improves. A more preferable lower limit of the thickness of the base layer is 25 μm, and a more preferable upper limit is 188 μm.

The method for producing the surface protection film of the present invention is not particularly limited. For example, an adhesive layer is formed by a known laminating method such as extrusion lamination or extrusion coating on a base layer previously obtained by T-die molding or inflation molding. A laminating method may be mentioned. In addition, the base material layer and the adhesive layer are independently formed into films, and then each obtained film is laminated by dry lamination, and the resin constituting the base layer and the resin constituting the adhesive layer are co-extruded using the T-die method. Methods for doing so can also be mentioned. Among them, the method of co-extrusion molding is preferable.

By adjusting the molding conditions of the adhesive layer (surface protection film), 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 are adjusted to the above range. It gets easier. Specifically, in the case of co-extrusion molding, it is preferable to prepare compound pellets (adhesive composition) by mixing the raw materials for the adhesive layer in advance using a twin screw extruder. Then, it is preferable to feed the prepared adhesive composition into a single-screw extruder set to gradually increase the temperature from the cylinder's base temperature of 100 to 150°C to the tip temperature of 200 to 230°C to mold the adhesive layer. Moreover, it is preferable that the flow paths of the mold, feed block, etc. are adjusted to 200 to 230°C. If a process that increases the heat history more than necessary is added or, conversely, a process in which the raw materials are not sufficiently kneaded (for example, a process of extruding the raw materials in a dry blend state at low temperature, etc.) is performed, the L component at 60 ° C. The component ratio and relaxation time, and the component ratio and relaxation time of the L component at 25°C may not be adjusted to the above range.

The surface protection film of the present invention has high adhesive strength (initial adhesive strength), and the adhesive strength is unlikely to increase over time or at high temperatures, and can be peeled off without glue remaining. The surface protection film of the present invention may be used to protect the surface of an adherend with a smooth surface, but it is particularly effective when used to protect the surface of an adherend having an uneven surface.

The surface protection film of the present invention is preferably used to protect the surfaces of members such as optical devices, metal plates, painted metal plates, resin plates, and glass plates. Among them, it is particularly suitable for protecting optical members having uneven shapes on one or both surfaces, such as prism sheets, diffusion films, etc.

According to the present invention, it is possible to provide a surface protection film that has high adhesive strength (initial adhesive strength), is unlikely to increase in adhesive strength over time or at high temperatures after being attached to an adherend, and can be peeled off without glue remaining.

The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Styrene-based elastomer>

In the examples and comparative examples, resins 1 to 4 shown in Table 1 were used as styrene-based elastomers.

In addition, the synthesis method of Resins 1 to 3 is as follows.

(Synthesis of Resin 1)

(Synthesis Example 1)

Into a nitrogen-substituted reaction vessel, 500 parts by weight of degassed and dehydrated cyclohexane, 10 parts by weight of styrene, and 5 parts by weight of tetrahydrofuran were charged, 0.13 parts by weight of n-butyllithium was added at 40° C., the polymerization start temperature, and polymerization was carried out at elevated temperature. was performed 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, then 85 parts by weight of 1,3-butadiene is added, and polymerization is further performed at elevated temperature to obtain a conjugated diene polymer. A block (block B) was obtained. As a result, styrene block copolymer (1) having a structure represented by general formula A-B was obtained.

After the polymerization conversion ratio reached nearly 100%, tetrachlorosilane was added as a coupling agent, and a coupling reaction was performed. 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 for 10 minutes. As a result, styrene block copolymer (2) having a structure represented by the general formula (AB) ₄ C was obtained.

Then, 0.03 parts by weight of diethylaluminum chloride and 0.06 parts by weight of bis(cyclopentadienyl)titanium furfuryloxychloride were added into the reaction vessel and stirred. The hydrogenation reaction was started at a hydrogen gas supply pressure of 0.7 MPa-Gauge and a reaction temperature of 80°C, and when hydrogen absorption was completed, the reaction solution was returned to room temperature and pressure and extracted from the reaction container. As a result, the hydrogenated product (1) of the styrene block copolymer having a structure represented by the general formula AB and the styrene content and diblock ratio shown in Table 1, and the styrene block copolymer having the structure represented by the general formula (AB) _4C A styrene-based elastomer containing the polymerized hydrogenated substance (2) was obtained.

GPC analysis was performed on some of the taken out polymers, and the weight average molecular weight (Mw) was determined.

(Synthesis of Resins 2 to 6)

(Synthesis Examples 2 to 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, coupling rate in the coupling reaction, diblock ratio, etc. were changed as shown in Table 1.

Additionally, the coupling rate can be adjusted depending on the type of coupling agent, addition amount, etc. As a result, in Resins 2 to 6, radial-type styrene-based elastomers were obtained.

In addition, the following commercial product was used as Resin 7. Resin 7 was a linear styrene-based elastomer.

DYNARON8300P (DR8300P) (styrene-ethylenebutylene-styrene block copolymer (SEBS), manufactured by JSR)

(Example 1)

(1) Manufacturing of surface protection film

As a raw material for the base layer, 100 parts by weight of block polypropylene resin (J715M, manufactured by Prime Polymer) was blended to obtain a resin composition.

As raw materials for the adhesive layer, 100 parts by weight of Resin 1 as a styrene-based elastomer, and 15 parts by weight of an alicyclic saturated hydrocarbon resin (P125, manufactured by Arakawa Chemical Industries, Ltd., softening point of 125°C, hydrogenation rate exceeding 95%) as a tackifying resin. By submixing, a mixture was obtained. The obtained mixture was extruded using a twin screw extruder, and the extruded strand was cooled in water and cut to obtain a compound adhesive composition of about Φ3 mm.

The resin composition obtained above was used as a raw material for the base material layer, and the adhesive composition obtained above was used as a raw material for the adhesive layer, and co-extrusion molding was performed by the T-die method. The adhesive composition was put into an extruder of Φ65 mm adjusted to a root temperature of 150°C and a tip temperature of 230°C, and the resin composition was put into an extruder of Φ115 mm and Φ75 mm adjusted to a root temperature of 200°C and a tip temperature of 230°C, and polymer Co-extrusion was performed in three layers from a multi-manifold type mold through a filter and feed block. The extruded resin is cooled by a cast roll adjusted to 30°C, and the base material layer is 35 ㎛ (the extrusion amount is adjusted to about 8 ㎛ thickness of the layer derived from the Φ75 mm extruder and 27 ㎛ thickness of the layer derived from the Φ115 mm extruder). , it was molded as a film with an adhesive layer of 3 μm. The film was wound to obtain a roll-shaped surface protection film.

(2) Pulse NMR measurement

A portion of the adhesive layer of the surface protection film was dissolved in toluene, dried naturally, and vacuum dried at 30°C to remove toluene to prepare 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 installed in a pulse NMR device (the minispec mq20, manufactured by BRUKER) and held at 25°C for 10 minutes, and then subjected to the Solid Echo method. Additionally, after measuring at 25°C, the temperature was raised, and then held at 60°C for 10 minutes, and then the CPMG method was performed at 60°C.

The obtained free-induction decay curve of spin-spin relaxation of the ^1H nucleus was separated into three curves originating from the three components of S component, M component, and L component, and the component ratio and relaxation time of S component and L component were calculated as Saved. Waveform separation was performed by fitting using both the Gaussian type and the exponential type.

In addition, using the analysis software "TD-NMRA (Version 4.3 Rev 0.8)" manufactured by BRUKER and following the product manual, in the Solid Echo method at 25°C, the S component is Gaussian type, and the M and L components are exponene type. Fitting was performed using a spherical type. In the CPMG method at 60°C, fitting was performed using the exponential type for all of the S, M, and L components. In addition, in the Solid Echo method, fitting was performed using points up to 0.6 milliseconds of the obtained relaxation curve, and in the CPMG method, fitting was performed using all points. The following equation was used for fitting.

Here, w1 to w3 are Weibull coefficients. In the Solid Echo method, w1 takes the value of 2, w2 and w3 take the value of 1, and in the CPMG method, w1 to w3 take the value of 1. A1 is the component ratio of the S component, B1 is the M component, and C1 is the L component, T2A is the S component, T2B is the M component, and T2C is the relaxation time of the L component. t is time.

[Measuring conditions]

[CPMG Act]

Scans: 256 times

Recycle Delay: 0.5 sec or 5 times the value of T1

90 - 180 plus searation: 0.4

Total number of acquired echoes: 1000

[Solid Echo Method]

Scans : 128 times

Recycle Delay: 0.5 sec or 5 times the value of T1

Acquisition scale: 1 ms

(Examples 2 to 8, Comparative Examples 1 to 6)

As shown in Table 2, 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. In Example 7, the styrene-based elastomer and tackifier resin were the same as in Example 2, but the extruder for feeding the adhesive composition was changed to an extruder with a diameter of Φ45 mm, the root temperature of the extruder was set to 190°C, the tip temperature was set to 230°C, and the cast roll was used. The temperature was changed to 40°C.

<Evaluation>

The following evaluation was performed about the surface protection films obtained in Examples 1 to 8 and Comparative Examples 1 to 6. The results are shown in Table 2.

(1) Measurement of initial adhesion

A 25 mm wide surface protection film was affixed to cover the adherend (a prism sheet with a peak-to-peak distance of 24 μm) to prepare a test piece. The sticking was performed by pressing at a speed of 300 mm/min using a 2 kg compression rubber roller in an environment of 23°C and 50% RH relative humidity.

The obtained test piece was left in an environment of 23°C and a relative humidity of 50% RH for 30 minutes. After leaving, the surface protection film was peeled from the adherend in a 180° direction at a tensile speed of 300 mm/min, and the initial adhesive force was measured.

However, in Comparative Example 3, the surface protection film was lifted from the adherend, and the initial adhesive force could not be measured.

(2) Measurement of adhesion after 1 week (1 W) at 50℃

The test piece obtained in the same manner as in (1) above was left in a temperature environment of 50°C for 1 week (1 W). After leaving, the test piece was taken out at room temperature and left for 60 minutes. Then, the surface protection film was peeled from the adherend in a 180° direction at a tensile speed of 300 mm/min, and the adhesive force was measured after 1 week (1 W) at 50°C. did.

However, in Comparative Examples 1 and 3, the surface protection film was lifted from the adherend, and the adhesive force could not be measured after 1 week (1 W) at 50°C.

(3) Determination of adhesion

From the initial adhesion measurement results, judgment was made based on the following criteria.

◎: 6 gf/25 ㎜ or more and 8 gf/25 ㎜ or less

○: 5 gf/25 ㎜ or more and less than 6 gf/25 ㎜, or greater than 8 gf/25 ㎜ and 12.5 gf/25 ㎜ or less.

△: 4 gf/25 ㎜ or more and less than 5 gf/25 ㎜, or greater than 12.5 gf/25 ㎜ and less than 15 gf/25 ㎜

×: less than 4 gf/25 mm, or greater than 15 gf/25 mm

In addition, from the measurement results of adhesive force after 1 week (1 W) at 50°C, judgment was made based on the following criteria.

◎ : 6 gf/25 ㎜ or more and 10 gf/25 ㎜ or less

○: 5 gf/25 ㎜ or more and less than 6 gf/25 ㎜, or greater than 10 gf/25 ㎜ and less than 15 gf/25 ㎜

△: 4 gf/25 ㎜ or more and less than 5 gf/25 ㎜, or greater than 15 gf/25 ㎜ and less than 20 gf/25 ㎜

×: less than 4 gf/25 mm, or greater than 20 gf/25 mm

(4) Evaluation of pool remaining

In (2) above, after peeling the surface protection film from the adherend, the adherend was confirmed and the presence or absence of glue residue was evaluated using a laser microscope (VK-X100, manufactured by Keyence). Evaluation was made according to the following criteria.

○: No remaining grass was seen.

×: Remains of grass was seen

According to the present invention, it is possible to provide a surface protection film that has high adhesive strength (initial adhesive strength), is unlikely to increase in adhesive strength over time or at high temperatures after being attached to an adherend, and can be peeled off without glue remaining.

Claims (7)

A surface protective film having a base layer and an adhesive layer,
The pressure-sensitive adhesive layer has a component ratio of the L component of 10% or less, a relaxation time of 25 milliseconds or more and 80 milliseconds or less, and was measured by CPMG method at 60°C using pulse NMR, and was measured at 25°C using pulse NMR. A surface protection film characterized in that the component ratio of the L component obtained by measuring by the Solid Echo method is 30% or more and 65% or less, and the relaxation time is 0.2 milliseconds or more and 0.4 milliseconds or less. According to claim 1,
The pressure-sensitive adhesive layer has a component ratio of the S component of 45% or more, and a relaxation time of 0.4 millisecond or more and 0.8 millisecond or less, as measured by CPMG method at 60°C using pulse NMR. A surface protection film characterized by the above-mentioned. The method of claim 1 or 2,
A surface protection film characterized in that the adhesive layer contains a styrene-based elastomer. According to claim 3,
The styrene-based elastomer includes a styrene block copolymer having a structure represented by the general formula AB or a hydrogenated product thereof (1), and a styrene block copolymer having a structure represented by the general formula ABA or general formula (AB) _n C or a hydrogenated product thereof. It is a styrene-based elastomer (I) containing additive (2),
The content of the styrene block copolymer or its hydrogenated product (1) in 100% by weight of the styrene-based elastomer (I) is 15% by weight or more and 50% by weight or less,
A surface protection film, wherein the content of the styrene block copolymer or its hydrogenated product (2) relative to 100 weight% of the 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: Component derived from coupling agent
n: integer greater than or equal to 2 According to claim 3 or 4,
The adhesive layer further contains a tackifying resin, and the content of the tackifying resin is 12 parts by weight or more and 45 parts by weight or less with respect to 100 parts by weight of the styrene-based elastomer. According to claim 4,
A surface protection film characterized in that n is 4 in the styrene-based elastomer (I). The method of claim 1, 2, 3, 4, 5 or 6,
The pressure-sensitive adhesive layer is measured by CPMG method at 60°C using pulse NMR, and the component ratio of the L component is 6.5% or less, and the relaxation time is 30 milliseconds or more and 70 milliseconds or less. A surface protection film.