JP2013142138A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protective film capable of achieving good conformability to a rugged level difference of an adherend and easy releasability in a good balance.SOLUTION: The surface protective film has a base material layer and a pressure sensitive adhesive layer formed on at least one surface of the base material layer. In the surface protective film: the tensile strength at 10% elongation is 14 N/20 mm or lower at 23°C; the adhesive force in peeling, as measured at 30 minutes after application to an SUS430BA plate and at 23°C, a pulling speed of 0.3 m/min, and a peel angle of 180°, is 1.0 N/20 mm or higher; and the adhesive force in peeling, as measured at 30 minutes after application to an SUS430BA plate and at 23°C, a pulling speed of 10 m/min, and a peel angle of 180°, is 4.0 N/20 mm or lower.

Description

  The present invention relates to a surface protective film. The surface protective film of this invention can be used suitably for surface protection, such as a member which has an unevenness | corrugation, for example.

  There are cases where decorative boards of various colors are affixed to the surface of home interior materials and furniture. When manufacturing such a decorative board, it is necessary to carry out processing such as thermoforming, vacuum forming, bending, cutting, etc. In that case, in order to prevent the decorative board surface from being scratched, a surface protective film is applied. It is common to stick. Thus, the surface protection film is used in order to prevent the surface of various goods and members from being damaged.

  When the shape of the adherend has uneven steps, the surface protective film to be attached to the surface of the adherend is required to have a performance capable of following the uneven steps.

  A protective sheet having improved followability to uneven steps has been reported (see Patent Document 1). However, this protective sheet has good followability to small uneven steps (for example, uneven steps up to the order of 10 μm), but it can follow large uneven steps (for example, uneven steps around the order of 1 mm). Is not enough. For this reason, even if it adheres to the adherend which has a large unevenness | corrugation level | step, it will float completely without following, and there exists a problem that a clearance gap will arise between a surface protection film and an adherend. In addition, even if it is able to follow immediately after sticking to an adherend having a large uneven step, the corner of the uneven step gradually rises over time, and a gap is created between the surface protective film and the adherend. There is a problem that it ends up. When such a gap occurs, scraps and foreign matter generated during various productions enter the gap, and irregularities are formed on the surface of the adherend, resulting in poor appearance, There is a problem that the merchandise value is lowered.

  In order to solve such a problem, for example, a means for increasing the adhesive force of the surface protective film and improving the followability to the uneven step can be considered. However, if the adhesive strength of the surface protection film is increased too much, it will not be easy to peel off after use, the peeling will become heavy and a large peeling force will be required, or the surface protection film will break during peeling. There is a problem that.

  From the above, there is a need for a surface protective film that can achieve a good balance between good followability to uneven steps of an adherend and light releasability in a well-balanced manner.

JP 2010-150498 A

  The subject of this invention is providing the surface protection film which can balance favorable followable | trackability to the uneven | corrugated level | step difference of a to-be-adhered body, and light peelability with sufficient balance.

The surface protective film of the present invention is
A surface protective film having a base material layer and an adhesive layer on at least one side of the base material layer,
Tensile strength at 10% tension is 14 N / 20 mm or less at 23 ° C.,
The peel adhesive strength to the SUS430BA plate is 1.0 N / 20 mm or more after 23 ° C., a pulling speed of 0.3 m / min, a peeling angle of 180 °, and 30 minutes after sticking.
The peeling adhesive strength to the SUS430BA plate is 4.0 N / 20 mm or less after 23 ° C., a tensile speed of 10 m / min, a peeling angle of 180 °, and 30 minutes after sticking.

  In preferable embodiment, the gel fraction of the said adhesive layer is 80 to 99%.

  In preferable embodiment, the said base material layer contains polyolefin resin.

  In a preferred embodiment, the polyolefin resin contains polyethylene.

  In preferable embodiment, the thickness of the said base material layer is 10-80 micrometers.

  ADVANTAGE OF THE INVENTION According to this invention, the surface protection film which can balance favorable followable | trackability to the uneven | corrugated level | step difference of a to-be-adhered body, and light peelability with sufficient balance can be provided.

It is a schematic sectional drawing which shows an example of preferable embodiment of the surface protection film of this invention.

≪A. Surface protection film >>
The surface protective film of the present invention has a base material layer and an adhesive layer on at least one side of the base material layer. The surface protective film of the present invention may have a form having a pressure-sensitive adhesive layer on one surface of the base material layer and the base material layer, or a pressure-sensitive adhesive layer on both surfaces of the base material layer and the base material layer. The form which has this may be sufficient. The preferable form of the surface protection film of this invention has an adhesive layer in the one surface of a base material layer and this base material layer.

  FIG. 1 is a schematic cross-sectional view of a surface protective film according to a preferred embodiment of the present invention. The surface protective film 10 includes a base material layer 1 and an adhesive layer 2. The surface protective film of the present invention may further have any appropriate other layer as required (not shown).

  For the purpose of forming a wound body that can be easily rewound on the surface of the base material layer 1 that is not provided with the pressure-sensitive adhesive layer 2, for example, the base material layer includes a fatty acid amide, polyethyleneimine, and a long-chain alkyl series. A mold release treatment may be performed by adding an additive or the like, or a coating layer formed from any appropriate release agent such as a silicone release agent, a long-chain alkyl release agent, a fluorine release agent may be provided. it can. Moreover, you may affix the release liner which has a mold release property on the surface which does not attach the adhesive layer 2 of the base material layer 1. FIG.

  The thickness of the surface protective film of the present invention can be set to any appropriate thickness depending on the application. From the viewpoint of scratch prevention and adhesive strength, the thickness is preferably 10 to 300 μm, more preferably 15 to 250 μm, still more preferably 20 to 200 μm, and particularly preferably 25 to 150 μm. In addition, since the surface protective film of this invention has favorable light peelability, even if it makes thickness thin, a fracture | rupture does not occur easily at the time of peeling. For this reason, the surface protective film of the present invention has a good balance between good followability to uneven steps of the adherend and light releasability in a balanced manner even if the thickness is thinner than conventional surface protective films. it can. Specifically, for example, the surface protective film of the present invention can exhibit the effects of the present invention even if the thickness is preferably 100 μm or less, and the thickness is more preferably 90 μm or less, and still more preferably. 80 μm or less, particularly preferably 70 μm or less.

  The surface protective film of the present invention has a tensile strength at 10% tension of 14 N / 20 mm or less at 23 ° C., preferably 13.8 N / 20 mm or less, more preferably 13.5 N / 20 mm or less. More preferably, it is 13.3 N / 20 mm or less, and particularly preferably 13.0 N / 20 mm or less. If the tensile strength at the time of 10% tension of the surface protective film of the present invention is 14 N / 20 mm or less at 23 ° C., good followability to the uneven step of the adherend can be exhibited. Good followability to large uneven steps (for example, uneven steps around the order of 1 mm) can be expressed. In addition, although the lower limit of the tensile strength at the time of 10% tension of the surface protective film of the present invention is better, it is preferably 1.0 N / 20 mm or more at 23 ° C. in practice.

  The surface protective film of the present invention has a peel adhesive strength to a SUS430BA plate of 23 ° C., a tensile speed of 0.3 m / min, a peel angle of 180 °, and a sticking strength of 1.0 N / 20 mm or more after 30 minutes. , Preferably 1.1 N / 20 mm or more, more preferably 1.2 N / 20 mm or more, further preferably 1.3 N / 20 mm or more, particularly preferably 1.4 N / 20 mm or more, most preferably 1. .5 N / 20 mm or more. If the peel adhesive strength of the surface protective film of the present invention to the SUS430BA plate is 1.0 N / 20 mm or more after 23 ° C., a tensile speed of 0.3 m / min, a peeling angle of 180 °, and 30 minutes after sticking In addition, since an appropriate adhesive force can be maintained, good followability to the uneven step of the adherend can be maintained. In addition, the upper limit of the peeling adhesive strength with respect to the SUS430BA board after 23 minutes at 23 ° C., a tensile rate of 0.3 m / min, a peeling angle of 180 °, and 30 minutes after sticking is practically the surface protective film of the present invention. It is preferably 6.0 N / 20 mm or less.

  The surface protective film of the present invention has a peeling adhesive strength to a SUS430BA plate of 4.0 N / 20 mm or less at 23 ° C., a tensile speed of 10 m / min, a peeling angle of 180 °, and 30 minutes after being applied. Is 3.8 N / 20 mm or less, more preferably 3.6 N / 20 mm or less, still more preferably 3.4 N / 20 mm or less, and particularly preferably 3.2 N / 20 mm or less. If the peel strength of the surface protective film of the present invention on the SUS430BA plate is 4.0 N / 20 mm or less after 23 ° C., a tensile speed of 10 m / min, a peeling angle of 180 °, and 30 minutes after sticking, high speed It is excellent in a feeling of peeling at the time of peeling, does not require a large peeling force, and can be easily peeled off after use, and can prevent the surface protective film from being broken during peeling. In addition, the lower limit of the peeling adhesive strength with respect to the SUS430BA plate after 23 minutes at 23 ° C., a tensile speed of 10 m / min, a peeling angle of 180 °, and 30 minutes after sticking is practically preferable. Is 0.1 N / 20 mm or more.

  The surface protective film of the present invention has the above-mentioned 10% tensile strength and the peel-off adhesive strength to the SUS430BA plate (when the tensile speed is 0.3 m / min and when the tensile speed is 10 m / min). In any case, by being within the above range, good followability to the uneven surface of the adherend can be expressed, and in particular, the large uneven surface of the adherend (for example, the uneven step around the 1 mm order level) ) Can be expressed in a good manner, and can be easily peeled off after use because it is lightly peeled and does not require a large peeling force, and the surface protective film breaks during peeling. This can be suppressed.

<A-1. Base material layer>
Any appropriate thickness can be adopted as the thickness of the base material layer depending on the application. However, since the surface protective film of the present invention has good light releasability, even when the thickness is reduced, the surface protection film does not easily break during peeling. For this reason, the surface protective film of the present invention has good followability to the uneven surface of the adherend and light peelability even if the thickness of the base material layer is thin compared to the conventional surface protective film, Can be balanced. Specifically, the thickness of the base material layer is preferably 10 to 80 μm, more preferably 15 to 70 μm, still more preferably 20 to 60 μm, and particularly preferably 25 to 55 μm.

  The base material layer may be a single layer or a laminate of two or more layers.

  The base material layer may be stretched.

  Any appropriate material can be adopted as the material of the base material layer depending on the application. For example, a plastic, paper, a metal film, a nonwoven fabric, etc. are mentioned. Preferably, it is a plastic. The base material layer may be composed of one kind of material, or may be composed of two or more kinds of materials. For example, you may be comprised from 2 or more types of plastics.

  When the base material layer contains a plastic, the content ratio is preferably 50% by weight or more, more preferably 70% by weight or more, further preferably 90% by weight or more, particularly preferably in the base material layer. Is 95% by weight or more, and most preferably 98% by weight or more. The upper limit of the content is preferably 100% by weight or less.

  Examples of the plastic include a polyester resin, a polyamide resin, and a polyolefin resin. Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Examples of the polyamide-based resin include various nylons. Examples of the polyolefin resin include olefin monomer homopolymers, olefin monomer copolymers, and the like.

  The plastic is preferably a polyolefin resin. Specific examples of the polyolefin-based resin include, for example, homopolypropylene; propylene-based copolymers such as block-type polypropylene, random-type polypropylene, and graft-type polypropylene using an ethylene component as a copolymerization component; reactor TPO; low-density polyethylene, Ethylene polymers such as medium density polyethylene, high density polyethylene, linear low density polyethylene, and ultra low density polyethylene; ethylene / propylene copolymer, ethylene / vinyl acetate copolymer, ethylene / methyl acrylate copolymer, ethylene And ethylene copolymers such as ethyl acrylate copolymer, ethylene / butyl acrylate copolymer, ethylene / methacrylic acid copolymer, and ethylene / methyl methacrylate copolymer.

  The polyolefin resin is preferably an ethylene polymer such as low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, and ultra low density polyethylene. The polyolefin resin may include only one of these ethylene polymers, or may include two or more of these ethylene polymers.

  The base material layer may contain any appropriate additive as required. Examples of the additive that can be contained in the base material layer include an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a filler, and a pigment. The kind, number, and amount of additives that can be contained in the base material layer can be appropriately set according to the purpose. In particular, when the material of the base material layer is plastic, it is preferable to contain some of the above additives for the purpose of preventing deterioration. From the viewpoint of improving weather resistance and the like, particularly preferred additives include antioxidants, ultraviolet absorbers, light stabilizers, and fillers.

  Any appropriate antioxidant can be adopted as the antioxidant. Examples of such antioxidants include phenol-based antioxidants, phosphorus-based processing heat stabilizers, lactone-based processing heat stabilizers, sulfur-based heat-resistant stabilizers, phenol-phosphorus-based antioxidants, and the like. The content of the antioxidant is preferably 1 part by weight or less with respect to 100 parts by weight of the base resin of the base layer (when the base layer is a blend, the blend is the base resin), More preferably, it is 0.5 weight part or less, More preferably, it is 0.01-0.2 weight part.

  Arbitrary appropriate ultraviolet absorbers can be employ | adopted as a ultraviolet absorber. Examples of such UV absorbers include benzotriazole UV absorbers, triazine UV absorbers, and benzophenone UV absorbers. The content of the ultraviolet absorber is preferably 2 parts by weight or less with respect to 100 parts by weight of the base resin forming the base layer (when the base layer is a blend, the blend is the base resin). More preferably 1 part by weight or less, still more preferably 0.01 to 0.5 part by weight.

  Any appropriate light stabilizer can be adopted as the light stabilizer. Examples of such light stabilizers include hindered amine light stabilizers and benzoate light stabilizers. The content ratio of the light stabilizer is preferably 2 parts by weight or less with respect to 100 parts by weight of the base resin forming the base layer (in the case where the base layer is a blend, the blend is the base resin). More preferably 1 part by weight or less, still more preferably 0.01 to 0.5 part by weight.

  Any appropriate filler can be adopted as the filler. Examples of such fillers include inorganic fillers. Specific examples of the inorganic filler include carbon black, titanium oxide, and zinc oxide. The content of the filler is preferably 20 parts by weight or less with respect to 100 parts by weight of the base resin forming the base layer (when the base layer is a blend, the blend is the base resin). More preferably, it is 10 weight part or less, More preferably, it is 0.01-10 weight part.

  Furthermore, as the additive, for the purpose of imparting antistatic properties, inorganic, low molecular weight and high molecular weight antistatic agents such as surfactants, inorganic salts, polyhydric alcohols, metal compounds, carbon and the like are also preferred. In particular, a high molecular weight antistatic agent and carbon are preferable from the viewpoint of contamination and adhesiveness maintenance.

<A-2. Adhesive layer>
The thickness of the pressure-sensitive adhesive layer is preferably 0.5 to 50 μm, more preferably 0.5 to 30 μm, still more preferably 0.5 to 20 μm, particularly preferably 0.5 to 10 μm, Most preferably, it is 0.5-8 micrometers. When the thickness of the pressure-sensitive adhesive layer is within the above range, the surface protective film of the present invention can achieve both good followability to the uneven surface of the adherend and light releasability in a balanced manner.

  The pressure-sensitive adhesive layer has a gel fraction of preferably 80 to 99%, more preferably 82 to 98%, still more preferably 85 to 97%, and particularly preferably 87 to 96%. The gel fraction of the pressure-sensitive adhesive layer is an index representing the cross-linking density of the pressure-sensitive adhesive contained in the pressure-sensitive adhesive layer. If it falls within the above range, the cross-linking density of the pressure-sensitive adhesive is moderately high, and it is difficult to flow appropriately. Thus, it is possible to keep good followability to the uneven surface of the adherend.

  The pressure-sensitive adhesive layer is composed of a pressure-sensitive adhesive. Only one type of adhesive may be used, or two or more types may be used.

  Arbitrary appropriate adhesives can be employ | adopted for the adhesive which comprises an adhesive layer. Examples of such adhesives include acrylic adhesives, silicone adhesives, rubber adhesives, and the like. As the pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive is particularly preferable.

  In the present invention, the acrylic pressure-sensitive adhesive is preferably a water-dispersed acrylic pressure-sensitive adhesive. By using a water-dispersed acrylic pressure-sensitive adhesive as the acrylic pressure-sensitive adhesive, the surface protective film of the present invention is superior to the uneven step of the adherend even if it is thinner than the conventional surface protective film. Good follow-up and light releasability can be balanced.

  The water-dispersed acrylic pressure-sensitive adhesive preferably contains a (meth) acrylic polymer and a crosslinking agent. Here, in the present invention, “(meth) acryl” means acryl and / or methacryl, and “(meth) acrylate” means acrylate and / or methacrylate.

  The (meth) acrylic polymer is preferably a polymer obtained by polymerizing a monomer component containing a (meth) acrylic monomer as a main component. The monomer in the monomer component may be only one type or two or more types. The content ratio of the (meth) acrylic monomer in the monomer component is preferably 40 to 99.9% by weight, and more preferably 50 to 99% by weight. When the content ratio of the (meth) acrylic monomer in the monomer component exceeds 99.9% by weight, the cohesive force of the pressure-sensitive adhesive may be significantly reduced. There exists a possibility that initial adhesive force may fall that the content rate of the (meth) acrylic-type monomer in the said monomer component is less than 40 weight%.

  The (meth) acrylic monomer preferably includes a (meth) acrylic monomer having an alkyl group. Carbon number of the said alkyl group becomes like this. Preferably it is 1-14, More preferably, it is 1-12, More preferably, it is 1-10, Most preferably, it is 1-4. When the number of carbon atoms of the alkyl group falls within the above range, sufficient initial adhesive strength can be secured and the effects of the present invention can be sufficiently exhibited.

  When the (meth) acrylic monomer includes a (meth) acrylic monomer having an alkyl group, the alkyl group having 1 to 4 carbon atoms with respect to the total amount of the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms. The content ratio of the (meth) acrylic monomer is preferably 40 to 80% by weight, and more preferably 50 to 75% by weight. When the content ratio of the (meth) acrylic monomer having an alkyl group having 1 to 4 carbon atoms with respect to the total amount of the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms falls within the above range, The cohesive force is improved, and the adhesive residue can be effectively prevented when the surface protective film of the present invention is peeled off from the adherend after use.

  Examples of the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth). Acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, 2-ethylhexyl methacrylate, isoamyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, cyclopentyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, cyclooctyl (meth) Chryrate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, isomyristyl (meth) acrylate, n-tridecyl (meth) ) Acrylate, n-tetradecyl (meth) acrylate, and the like. Among these, the (meth) acrylic monomer having an alkyl group having 1 to 14 carbon atoms is preferably ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl ( Examples include meth) acrylate, t-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Only 1 type may be sufficient as the (meth) acrylic-type monomer which has a C1-C14 alkyl group, and 2 or more types may be sufficient as it.

  The monomer component may contain a hydroxyl group-containing monomer. When the monomer component contains a hydroxyl group-containing monomer, the crosslinkability with the crosslinking agent is increased, and the adhesive residue is more effectively prevented when the surface protective film of the present invention is peeled off from the adherend after use. Can do. The content ratio of the hydroxyl group-containing monomer in the monomer component is preferably 1 to 30% by weight, more preferably 2 to 20% by weight. When the content ratio of the hydroxyl group-containing monomer in the monomer component exceeds 30% by weight, the initial adhesive strength may be reduced. When the content ratio of the hydroxyl group-containing monomer in the monomer component is less than 1% by weight, the cohesive force of the pressure-sensitive adhesive may be significantly reduced.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyhexyl (meth) acrylate, and 6-hydroxyhexyl ( (Meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate, N-methylol (meth) acrylamide , N-hydroxy (meth) acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl Ether and the like. Among these, the hydroxyl group-containing monomer is preferably 2-hydroxyethyl (meth) acrylate or 2-hydroxyhexyl (meth) acrylate. Only one type of hydroxyl group-containing monomer may be used, or two or more types may be used.

  The monomer component may contain any appropriate other monomer. Examples of such other monomers include sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl ester monomers, aromatic vinyl monomers, carboxyl group-containing monomers, acid anhydride group-containing monomers, and amides. Examples thereof include a group-containing monomer, an amino group-containing monomer, an imide group-containing monomer, an epoxy group-containing monomer, and a vinyl ether monomer. Such other monomer may be only one kind or two or more kinds. The content ratio of the other monomer in the monomer component is preferably 1 to 50% by weight, and more preferably 5 to 40% by weight. When the content of other monomers in the monomer component exceeds 50% by weight, the initial adhesive strength may be reduced. When the content ratio of the other monomer in the monomer component is less than 1% by weight, the cohesive force of the pressure-sensitive adhesive may be significantly reduced.

  A sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, a cyano group-containing monomer, a vinyl ester monomer, an aromatic vinyl monomer, and the like are effective components for improving the cohesive force and heat resistance of an adhesive, for example.

  Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, and (meth). Examples include acryloyloxynaphthalene sulfonic acid.

  Examples of the phosphoric acid group-containing monomer include 2-hydroxyethylacryloyl phosphate.

  Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

  Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl laurate, vinyl pyrrolidone and the like.

  Examples of the aromatic vinyl monomer include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and benzyl (meth) acrylate.

  A carboxyl group-containing monomer, an acid anhydride group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, an imide group-containing monomer, an epoxy group-containing monomer, a vinyl ether monomer, etc. are effective components for improving the adhesive strength of the pressure-sensitive adhesive, or It is a component having a functional group that serves as a crosslinking base point.

  Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among these, preferable examples of the carboxyl group-containing monomer include acrylic acid and methacrylic acid.

  Examples of the acid anhydride group-containing monomer include maleic anhydride and itaconic anhydride.

  Examples of the amide group-containing monomer include acrylamide, methacrylamide, diethyl (meth) acrylamide, N-vinylpyrrolidone, N-vinyl-2-pyrrolidone, N- (meth) acryloylpyrrolidone, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylamide, N, N′-methylenebisacrylamide, N, N-dimethylaminopropylacrylamide, N, N-dimethylaminopropylmethacrylamide and the like Can be mentioned.

  Examples of the amino group-containing monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N- (meth) acryloylmorpholine, (meth) acrylic acid aminoalkyl ester, and the like. Is mentioned.

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

  Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate and allyl glycidyl ether.

  Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, and the like.

  The glass transition temperature (Tg) of the (meth) acrylic polymer is preferably −100 to 0 ° C., more preferably −100 to −10 ° C., from the viewpoint that the balance of adhesive performance can be improved. More preferably, it is −100 to −20 ° C. When the glass transition temperature (Tg) of the (meth) acrylic polymer exceeds 0 ° C., the (meth) acrylic polymer is difficult to flow, and the wettability to the adherend becomes insufficient, and the surface protection of the present invention. There is a risk of swelling between the film and the adherend. In addition, the glass transition temperature (Tg) of a (meth) acrylic-type polymer can be adjusted in the said range by changing the monomer component and composition ratio to be used suitably. The glass transition temperature (Tg) (° C.) may be a general value. For example, Polymer Handbook Fourth Edition (edited by J. Brandup et al., 1999 John Wiley & Sons, Inc), Chapter VI, 198-253. The numerical value etc. which are described in the term can be used. In the case of a novel polymer, the peak temperature of loss tangent (tan δ) in a viscoelasticity measurement method (shear method, measurement frequency: 1 Hz) may be adopted as the glass transition temperature (Tg).

  The (meth) acrylic polymer can be preferably produced by any suitable aqueous dispersion polymerization. Specifically, such water dispersion polymerization preferably includes emulsion polymerization. Such a polymerization reaction is usually performed at about 60 to 80 ° C. for about 4 to 10 hours under an inert gas stream such as nitrogen. After the emulsion polymerization, a stable water-dispersed (meth) acrylic polymer can be usually obtained by neutralizing with a neutralizing agent such as ammonia and adjusting to a predetermined pH.

  Examples of the polymerization initiator that can be used when the (meth) acrylic polymer is produced by emulsion polymerization include 2,2′-azobisisobutyronitrile and 2,2′-azobis (2-amidinopropane) dihydro. Chloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2 ′ -Azobis (N, N'-dimethyleneisobutylamidine), 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate (for example, VA-057 manufactured by Wako Pure Chemical Industries, Ltd.) Azo-based initiators such as potassium persulfate and ammonium persulfate; di (2-ethylhexyl) peroxydicarbonate, di (4-t Butylcyclohexyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di -N-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di (4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butylperoxyisobuty Peroxide initiators such as rate, 1,1-di (t-hexylperoxy) cyclohexane, t-butyl hydroperoxide, hydrogen peroxide; combination of persulfate and sodium bisulfite, peroxide and ascorbine Peroxide and reducing agent such as sodium acid combination Look at the combined redox initiator, and the like. These polymerization initiators may be used alone or in combination of two or more. The content of the polymerization initiator is preferably 0.005 to 1% by weight, more preferably 0.02 to 0.5% by weight, based on the monomer component.

  A surfactant can be used when the (meth) acrylic polymer is produced by emulsion polymerization. Examples of such surfactants include nonionic surfactants and anionic surfactants.

  Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, oxyethylene-oxypropylene block polymer, sorbitan fatty acid ester, polyoxyethylene fatty acid and the like. Only one kind of such nonionic surfactant may be used, or two or more kinds thereof may be used. The content ratio of such a nonionic surfactant is preferably 0.2 to 4% by weight with respect to the monomer component.

  Examples of the anionic surfactant include alkyl sulfates, alkylbenzene sulfonic acids, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl phosphates, and the like. Only one kind of such an anionic surfactant may be used, or two or more kinds thereof may be used. The content ratio of such an anionic surfactant is preferably 0.1 to 2% by weight with respect to the monomer component.

  When producing the (meth) acrylic polymer by emulsion polymerization, a chain transfer agent may be used. By using a chain transfer agent, the molecular weight of the resulting (meth) acrylic polymer can be adjusted as appropriate.

  Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. Such chain transfer agent may be only one kind, or two or more kinds. The content ratio of such a chain transfer agent is preferably 0.01 to 0.1% by weight with respect to the monomer component.

  The water-dispersed acrylic pressure-sensitive adhesive preferably contains a (meth) acrylic polymer and a crosslinking agent. By including a crosslinking agent, a crosslinked structure is constructed by a crosslinking reaction, and the effects of the present invention can be expressed more effectively.

  Examples of the crosslinking agent include isocyanate compounds, epoxy compounds, oxazoline compounds, melamine resins, aziridine derivatives, and metal chelate compounds. Of these, the cross-linking agent is preferably an oxazoline compound. Only one type of crosslinking agent may be used, or two or more types may be used.

  Examples of the isocyanate compound include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate; and emulsified isocyanates. Only one type of isocyanate compound may be used, or two or more types may be used.

  More specifically, as the isocyanate compound, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; -Aromatic diisocyanates such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; trimethylolpropane / tolylene diisocyanate trimer adduct (product name: Coronate L, manufactured by Nippon Polyurethane Industry), trimethylolpropane / Hexamethylene diisocyanate trimer adduct (product name: Coronate HL, manufactured by Nippon Polyurethane Industry) Cyanurate body (manufactured by Nippon Polyurethane Industry Co., trade name: Coronate HX) isocyanate adducts such as; self-emulsifying type polyisocyanate (Nippon Polyurethane Industry Co., Ltd., trade name AQUANATE 200); and the like.

  Examples of the oxazoline compound include 2-oxazoline, 3-oxazoline, 4-oxazoline, 5-keto-3-oxazoline, and Epocros (manufactured by Nippon Shokubai). Only one oxazoline compound may be used, or two or more oxazoline compounds may be used.

  Examples of the epoxy compound include N, N, N ′, N′-tetraglycidyl-m-xylenediamine (for example, trade name “TETRAD-X”, manufactured by Mitsubishi Gas Chemical), 1,3-bis (N, N -Diglycidylaminomethyl) cyclohexane (for example, trade name “TETRAD-C”, manufactured by Mitsubishi Gas Chemical), tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, diglycidylaniline, diglycidyl-o-toluidine, etc. Can be mentioned. Only one type of epoxy compound may be used, or two or more types may be used.

  Examples of melamine resins include hexamethylol melamine and water-soluble melamine resins. Only one type of melamine resin may be used, or two or more types may be used.

Examples of the aziridine derivative include commercially available product names HDU (manufactured by Mutual Yakuko), brand names TAZM (manufactured by Mutual Yakuko), and trade names TAZO (manufactured by Mutual Yakuko). Only one type of aziridine derivative may be used, or two or more types may be used.

  Examples of the metal chelate compound include aluminum, iron, tin, titanium, and nickel as metal components, and acetylene, methyl acetoacetate, and ethyl lactate as chelate components. Only one metal chelate compound may be used, or two or more metal chelate compounds may be used.

  In the water-dispersed acrylic pressure-sensitive adhesive, the content of the crosslinking agent is preferably 0.1 to 10% by weight, more preferably 0.1 to 8% by weight with respect to the (meth) acrylic polymer. More preferably, it is 0.1 to 6% by weight, particularly preferably 0.2 to 4% by weight, and most preferably 0.4 to 3% by weight. When the content of the cross-linking agent is less than 0.1% by weight, cross-linking by the cross-linking agent is insufficient, the cohesive force of the pressure-sensitive adhesive is reduced, good followability to unevenness of the adherend, and light weight. There is a possibility that the peelability cannot be balanced in a balanced manner. When the content of the cross-linking agent exceeds 10% by weight, the initial adhesive strength of the pressure-sensitive adhesive is insufficient, and the cohesive strength of the pressure-sensitive adhesive is increased and the fluidity is lowered, so that the adherend is not wet. This is sufficient, and there is a possibility that good followability to uneven steps of the adherend and light releasability cannot be achieved in a balanced manner.

  The water-dispersed acrylic pressure-sensitive adhesive may contain an ultraviolet absorber or an antioxidant in order to impart weather resistance. Only one type of ultraviolet absorber may be used, or two or more types may be used. Only one type of antioxidant may be used, or two or more types may be used.

  Examples of the UV absorber include benzotriazole UV absorbers, triazine UV absorbers, benzophenone UV absorbers, salicylate UV absorbers, and cyanoacrylate UV absorbers.

  Specific examples of the ultraviolet absorber include, for example, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2 -(2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl]- 2H-benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetrabutyl) -6- (2H-benzotriazole)], 2- (4,6-diphenyl-1,3,5 -Triazin-2-yl) -5-[(hexyl) oxy] -phenol, 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxy Examples include benzoate, 4-t-butylphenyl salicylate, and ethyl-2-cyano-3,3-diphenyl acrylate.

  The content ratio of the ultraviolet absorber is preferably 0.05 to 2% by weight, more preferably 0.1 to 1.5% by weight, based on the resin solid content of the water-dispersed acrylic pressure-sensitive adhesive. There exists a possibility that the effect which improves weather resistance cannot be acquired as the said content rate of a ultraviolet absorber is less than 0.05 weight%. If the content of the ultraviolet absorber exceeds 2% by weight, the ultraviolet absorber may bleed.

  Examples of the antioxidant include hindered phenol-based antioxidants, phosphorus-based processing heat stabilizers, lactone-based processing heat stabilizers, sulfur-based heat stabilizers, and the like.

  The content of the antioxidant is preferably 0.01 to 3% by weight, more preferably 0.01 to 1% by weight, based on the resin solid content of the water-dispersed acrylic pressure-sensitive adhesive.

  The water-dispersed acrylic pressure-sensitive adhesive may contain a tackifier. Only one type of tackifier may be used, or two or more types may be used.

  Examples of the tackifier include xylene resin; rosin resin such as rosin, polymerized rosin, hydrogenated rosin, rosin ester; terpene resin such as terpene resin, terpene phenol resin, rosin phenol resin; aliphatic, aromatic And alicyclic petroleum resins; coumarone resins; styrene resins; alkylphenol resins; Among these, the tackifier is preferably a rosin resin, a terpene phenol resin, or an aromatic petroleum resin.

  The content of the tackifier is preferably 1 to 100% by weight, more preferably 5 to 50% by weight, based on the resin solid content of the water-dispersed acrylic pressure-sensitive adhesive.

  The water-dispersed acrylic pressure-sensitive adhesive may contain any appropriate other additive. Examples of such other additives include softeners, surface lubricants, leveling agents, corrosion inhibitors, light stabilizers, heat stabilizers, polymerization inhibitors, silane coupling agents, lubricants, inorganic or organic fillers. Agents, metal powders, pigments, solvents and the like.

  The surface of the pressure-sensitive adhesive layer may be subjected to surface treatment such as corona treatment, plasma treatment, or ultraviolet treatment.

≪B. Manufacturing method of surface protective film >>
The surface protective film of the present invention can be produced by any appropriate method. As a manufacturing method of the surface protection film of this invention, Preferably, the method of forming an adhesive layer on a base material layer is mentioned. As such a method, for example, (1) a method in which a pressure-sensitive adhesive layer formed by drying and removing moisture after applying a water-dispersed acrylic pressure-sensitive adhesive to a release-treated separator or the like is adhered to a base material layer. (2) A method of forming a pressure-sensitive adhesive layer on a base material layer by applying a water-dispersed acrylic pressure-sensitive adhesive on the base material layer, drying and removing moisture and the like. Thereafter, curing (aging treatment) may be performed for the purpose of adjusting the component transfer of the pressure-sensitive adhesive layer or adjusting the crosslinking reaction.

  As a method for forming the pressure-sensitive adhesive layer, any appropriate method that can be used for producing a surface protective film can be adopted. Specifically, as such a method, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, die coater, etc. Extrusion coating method by, etc. are mentioned.

  On the surface of the pressure-sensitive adhesive layer, for example, a release treatment sheet (for example, a release sheet, a separator, a release liner) may be provided until it is put to practical use.

  Examples of the constituent material of the release treatment sheet include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films; porous materials such as paper, cloth, and nonwoven fabric; nets; foamed sheets; metal foils; Is mentioned.

  The thickness of the release treatment sheet is preferably 5 to 200 μm, more preferably 5 to 30 μm.

  The release treatment sheet may contain a release agent such as silicone, fluorine, long chain alkyl, and fatty acid amide. The release treatment sheet may be subjected to release treatment or antifouling treatment with silica powder or the like. The release treatment sheet may be subjected to an antistatic treatment such as a coating type, a kneading type, or a vapor deposition type.

≪C. Application of surface protection film >>
Even if the surface protective film of the present invention is thinner than the conventional surface protective film, it is possible to achieve both good followability to the uneven surface of the adherend and light releasability in a balanced manner. For this reason, the surface protective film of the present invention can be used for any appropriate application. For example, a member such as a metal plate, a painted plate, an aluminum sash, a resin plate, a decorative steel plate, a vinyl chloride laminated steel plate, a glass plate; When carrying, processing or curing an optical member such as a sheet or a liquid crystal panel; an electronic member; etc., it can be preferably used for applications such as attaching to the surface of these members to protect the surface. The surface protective film of the present invention can be suitably used for surface protection of a member having unevenness, and can be particularly suitably used for surface protection of a member having a large unevenness level of 1 mm to 5 mm.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples at all. In addition, the test and evaluation method in an Example etc. are as follows.

(Adhesive force)
A surface protection film cut to a size of 20 mm in width and 100 mm in length was laminated on a stainless steel plate finished with SUS430BA under pressure bonding conditions of 0.25 MPa and a speed of 0.3 m / min to prepare an evaluation sample.
After leaving the laminate for 30 minutes, the adhesive strength when peeled at a peeling angle of 180 ° was measured with a universal tensile tester at a tensile speed of 0.3 m / min and 10 m / min.
Separately, after standing for 1 day after laminating, the adhesive strength when peeled at a peeling angle of 180 ° at a tensile speed of 0.3 m / min and 10 m / min was measured with a universal tensile tester.
The measurement was performed in an environment of 23 ° C. × 50% RH.

(Tensile strength at 10% tension)
A strip-shaped test piece (MD test piece) was cut out along the longitudinal direction (MD) of the surface protective film, and after holding the test piece for 30 minutes or more in an environment of 23 ° C. × 50% RH, JIS-Z Based on −0237, the tensile strength when stretched by 10% was measured. In addition, it measured using the three test pieces cut out from the different location (n = 3), and made those average values into the measured value. The measurement conditions are as follows.
Measurement temperature and humidity: 23 ° C x 50% RH
Specimen width: 20 mm
Tensile speed: 300 mm / min Distance between chucks: 50 mm

(Unevenness tracking)
Two pieces of SUS430BA having a thickness of 5 mm were displaced and fixed to form an adherend. A surface protective film having a width of 20 mm was bonded to this surface. As the evaluation of the unevenness followability, in the environment of 23 ° C. × 50% RH, after 30 minutes and 1 day, the gap was less than 1 mm, and the gap was 1 mm or more.

(Peeling feeling)
In the evaluation of adhesive strength, after being left for 30 minutes after lamination or after being left for 1 day after lamination, the adhesive strength when peeled at a peeling angle of 180 ° at a tensile speed of 10 m / min with a universal tensile tester. Was 4.0 N / 20 mm or less, and it was rated as x when it exceeded 4.0 N / 20 mm.

(Gel fraction)
The pressure-sensitive adhesive layer was collected by scraping a predetermined amount (about 500 mg) from the obtained surface protective film, and a porous tetrafluoroethylene sheet (trade name “NTF1122”, manufactured by Nitto Denko Corporation) having an average pore diameter of 0.2 μm was collected. After wrapping, it was tied with a kite string, the weight at that time was measured, and this weight was taken as the weight before immersion. The weight before immersion is the total weight of the pressure-sensitive adhesive layer, the tetrafluoroethylene sheet, and the kite string. Moreover, the weight of the porous tetrafluoroethylene sheet | seat to be used and a kite string was also measured, and this weight was made into the wrapping weight.
Next, the pressure-sensitive adhesive layer wrapped with a porous tetrafluoroethylene sheet and tied with a kite string (sample) is placed in a pre-weighed 50 ml container, filled with ethyl acetate, and 7% at room temperature (23 ° C.). Let stand for days.
Thereafter, the sample was taken out from the container, dried in a dryer at 130 ° C. for 2 hours to remove ethyl acetate, the sample weight was measured, and this weight was defined as the weight after immersion.
The gel fraction was calculated from the following formula. In addition, A is a weight after immersion, B is a wrapping weight, and C is a weight before immersion.
Gel fraction (% by weight) = (A−B) / (C−B) × 100

[Example 1]
(Preparation of water-dispersed acrylic polymer (A-1))
In a reaction vessel equipped with a cooling tube, a nitrogen introducing tube, a thermometer, and a stirring device, 49 parts by weight of 2-ethylhexyl acrylate, 49 parts by weight of butyl methacrylate, 2 parts by weight of acrylic acid, and 2,2′-azobis as a polymerization initiator (2-Amidinopropane) dihydrochloride 0.1 part by weight, polyoxyethylene nonylphenyl ether ammonium sulfate 2.0 part by weight as an emulsifier, and water 100 part by weight were added, emulsion polymerized, pH 8 with 10% by weight ammonia water. To obtain a water-dispersed acrylic polymer (A-1).
(Preparation of water-dispersed acrylic pressure-sensitive adhesive (B-1))
The product name “Epocross WS” manufactured by Nippon Shokubai Co., Ltd. is used as a water-soluble crosslinking agent containing an oxazoline group per 100 parts by weight of the solid (water-dispersed copolymer) in the water-dispersed acrylic polymer (A-1). -500 "(oxazoline group equivalent: 220 g · solid / eq.) 4.0 parts by weight was mixed to obtain a water-dispersed acrylic pressure-sensitive adhesive (B-1).
(Manufacture of surface protective film (1))
A low-density polyethylene resin (Petrocene 180, density: 0.922 g / cm ³ , manufactured by Tosoh Corporation) was used to extrude from a die heated to 160 ° C. by an inflation method to form a polyethylene film having a thickness of 40 μm. One side of this polyethylene film is subjected to corona treatment, and a water-dispersed acrylic pressure-sensitive adhesive (B-1) is applied to the corona-treated surface and dried at 80 ° C. for 1 minute to form a pressure-sensitive adhesive layer having a thickness of 3 μm. A surface protective film (1) was produced.
The results are shown in Table 1.

[Example 2]
A surface protective film (2) was produced in the same manner as in Example 1 except that the thickness of the polyethylene film was 30 μm.
The results are shown in Table 1.

Example 3
(Preparation of water-dispersed acrylic polymer (A-3))
In a reaction vessel equipped with a cooling pipe, a nitrogen introduction pipe, a thermometer, and a stirring device, 58 parts by weight of butyl acrylate, 40 parts by weight of butyl methacrylate, 2 parts by weight of acrylic acid, and 2,2′-azobis (2 -Amidinopropane) dihydrochloride 0.1 part by weight, polyoxyethylene nonylphenyl ether 0.3 part by weight, polyoxyethylene nonylphenyl ether ammonium sulfate 1.0 part by weight as emulsifier, and water 100 part by weight were added to emulsify Polymerized and adjusted to pH 8 with 10 wt% aqueous ammonia to obtain a water-dispersed acrylic polymer (A-3).
(Preparation of water-dispersed acrylic pressure-sensitive adhesive (B-3))
The product name “Epocross WS” manufactured by Nippon Shokubai Co., Ltd. is used as a water-soluble crosslinking agent containing an oxazoline group per 100 parts by weight of the solid content (water-dispersed copolymer) in the water-dispersed acrylic polymer (A-3). -500 "(oxazoline group equivalent: 220 g · solid / eq.) 2.0 parts by weight was mixed to obtain a water-dispersed acrylic pressure-sensitive adhesive (B-3).
(Manufacture of surface protective film (3))
A low-density polyethylene resin (Petrocene 180, density: 0.922 g / cm ³ , manufactured by Tosoh Corporation) was used and extruded from a die heated to 160 ° C. by an inflation method to form a polyethylene film having a thickness of 55 μm. One side of this polyethylene film is subjected to corona treatment, and a water-dispersed acrylic pressure-sensitive adhesive (B-3) is applied to the corona-treated surface and dried at 80 ° C. for 1 minute to form a pressure-sensitive adhesive layer having a thickness of 6 μm. A surface protective film (3) was produced.
The results are shown in Table 1.

Example 4
(Preparation of water-dispersed acrylic pressure-sensitive adhesive (B-4))
The product name “Epocross WS” manufactured by Nippon Shokubai Co., Ltd. is used as a water-soluble crosslinking agent containing an oxazoline group per 100 parts by weight of the solid content (water-dispersed copolymer) in the water-dispersed acrylic polymer (A-3). -500 "(oxazoline group equivalent: 220 g · solid / eq.) Of 4.0 parts by weight was mixed to obtain a water-dispersed acrylic pressure-sensitive adhesive (B-4).
(Manufacture of surface protective film (4))
40 parts by weight of crystalline homopolypropylene (density: 0.905 g / cm ³ ), 40 parts by weight of random polypropylene (density: 0.900 g / cm ³ ), low-density polyethylene resin (petrocene 180, density: 0.922 g / cm ³⁾ 20 parts by weight of Tosoh Co., Ltd.) was extruded from a die heated to 180 ° C. by the T-die method to form a 25 μm thick blend film. One side of this blend film is subjected to corona treatment, and a water-dispersed acrylic pressure-sensitive adhesive (B-4) is applied to the corona-treated surface and dried at 80 ° C. for 1 minute to form a pressure-sensitive adhesive layer having a thickness of 5 μm. A surface protective film (4) was produced.
The results are shown in Table 1.

[Comparative Example 1]
(Preparation of solvent-type acrylic polymer solution (CA-1))
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a condenser, 100 parts by weight of butyl acrylate, 5 parts by weight of acrylic acid, 0.2 part by weight of benzoyl peroxide as a polymerization initiator, and acetic acid 200 parts by weight of ethyl was charged, nitrogen gas was introduced while gently stirring, and the polymerization temperature was kept at around 65 ° C. for about 6 hours, and a solvent-type acrylic polymer solution (CA-1) ( A concentration of 30% by weight) was obtained.
(Preparation of acrylic adhesive solution (CB-1))
A solvent-type acrylic polymer solution (CA-1) (concentration 30% by weight) was diluted to 20% by weight with ethyl acetate, and an epoxy compound (TETRAD-C, 100 parts by weight of acrylic polymer solid content in this solution). 6.0 parts by weight of Mitsubishi Gas Chemical Co., Ltd.) was added and mixed and stirred at 25 ° C. for about 1 minute to obtain an acrylic pressure-sensitive adhesive solution (CB-1).
(Manufacture of surface protective film (C1))
A low-density polyethylene resin (Petrocene 180, density: 0.922 g / cm ³ , manufactured by Tosoh Corporation) was used and extruded from a die heated to 160 ° C. by an inflation method to form a polyethylene film having a thickness of 60 μm. One side of this polyethylene film is subjected to corona treatment, and an acrylic pressure-sensitive adhesive solution (CB-1) is applied to the corona-treated surface and dried at 80 ° C. for 1 minute to form a pressure-sensitive adhesive layer having a thickness of 4 μm. A protective film (C1) was produced.
The results are shown in Table 1.

[Comparative Example 2]
(Preparation of solvent-type acrylic polymer solution (CA-2))
In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser, 2-ethylhexyl acrylate 30 parts by weight, ethyl acrylate 70 parts by weight, methyl methacrylate 5 parts by weight, acrylic acid 0.2 parts by weight , 0.8 part by weight of hydroxyethyl acrylate, 0.2 part by weight of benzoyl peroxide as a polymerization initiator, and 200 parts by weight of ethyl acetate were introduced, nitrogen gas was introduced while gently stirring, and the liquid temperature in the flask was adjusted to 65. The polymerization reaction was carried out for about 6 hours while maintaining the temperature around 0 ° C. to obtain a solvent-type acrylic polymer solution (CA-2) (concentration 30% by weight).
(Preparation of acrylic adhesive solution (CB-2))
The acrylic pressure-sensitive adhesive solution (CB-1) prepared in Comparative Example 1 (concentration 30) per 100 parts by weight of the acrylic polymer solid content in the solvent-type acrylic polymer solution (CA-2) (concentration 30% by weight). 20% by weight of an acrylic polymer solid content in a solution (by weight), 2.0 parts by weight of an isocyanate compound (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.), and dibutyltin dilaurate (1% by weight ethyl acetate) as a crosslinking catalyst. Solution) 0.2 part by weight was added and mixed and stirred at 25 ° C. for about 1 minute to obtain an acrylic pressure-sensitive adhesive solution (CB-2).
(Manufacture of surface protective film (C2))
A low-density polyethylene resin (Petrocene 180, density: 0.922 g / cm ³ , manufactured by Tosoh Corporation) was used and extruded from a die heated to 160 ° C. by an inflation method to form a 75 μm thick polyethylene film. One side of this polyethylene film is subjected to corona treatment, an acrylic pressure-sensitive adhesive solution (CB-2) is applied to this corona-treated surface, and dried at 80 ° C. for 1 minute to form a pressure-sensitive adhesive layer having a thickness of 10 μm. A protective film (C2) was produced.
The results are shown in Table 1.

[Comparative Example 3]
(Manufacture of surface protective film (C3))
40 parts by weight of crystalline homopolypropylene (density: 0.905 g / cm ³ ), 40 parts by weight of random polypropylene (density: 0.900 g / cm ³ ), low-density polyethylene resin (petrocene 180, density: 0.922 g / cm ³⁾ 20 parts by weight of Tosoh Co., Ltd.) was extruded from a die heated to 180 ° C. by the T-die method to form a 50 μm-thick blend film. One side of this blend film was subjected to corona treatment, and the water-dispersed acrylic pressure-sensitive adhesive (B-3) obtained in Example 3 was applied to this corona-treated surface, dried at 80 ° C. for 1 minute, and a thickness of 10 μm. A surface protective film (C3) was produced.
The results are shown in Table 1.

[Comparative Example 4]
(Manufacture of surface protective film (C4))
The water-dispersed acrylic pressure-sensitive adhesive (B-3) obtained in Example 3 was applied to a 38 μm-thick polyester film (manufactured by Toray Industries, Inc.), dried at 80 ° C. for 1 minute, and a pressure-sensitive adhesive layer having a thickness of 10 μm was formed. The surface protective film (C4) was produced.
The results are shown in Table 1.

  It can be seen that the surface protective films (1) to (4) obtained in Examples 1 to 4 have both good followability to the uneven surface of the adherend and light releasability in a well-balanced manner. . That is, the surface protective films (1) to (4) obtained in Examples 1 to 4 were peeled at a low speed on the SUS430BA plate (23 ° C., tensile speed 0.3 m / min, peeling angle 180 °, 30 minutes after sticking) is 1.0 N / 20 mm or more, and an appropriate adhesive force can be maintained, so that it can be understood that good followability to the uneven step of the adherend can be maintained. Further, the surface protective films (1) to (4) obtained in Examples 1 to 4 were peeled at a high speed on the SUS430BA plate (23 ° C., tensile speed 10 m / min, peeling angle 180 °, sticking) 30 minutes later) is 4.0N / 20mm or less, excellent peeling feeling at the time of high-speed peeling, light peeling and no need for large peeling force, and easy peeling after use. It can be seen that the breakage of the surface protective film can be suppressed during peeling. Furthermore, the surface protection films (1) to (4) obtained in Examples 1 to 4 have a tensile strength at 10% tension of 14 N / 20 mm or less at 23 ° C., to the uneven surface of the adherend. In particular, it is possible to express good followability to large uneven steps (for example, uneven steps around the order of 1 mm) on the adherend.

  Even if the surface protective film of the present invention is thinner than the conventional surface protective film, it is possible to achieve both good followability to the uneven surface of the adherend and light releasability in a balanced manner. For this reason, the surface protective film of the present invention can be used for any appropriate application. For example, a member such as a metal plate, a painted plate, an aluminum sash, a resin plate, a decorative steel plate, a vinyl chloride laminated steel plate, a glass plate; When carrying, processing or curing an optical member such as a sheet or a liquid crystal panel; an electronic member; etc., it can be preferably used for applications such as attaching to the surface of these members to protect the surface. Especially the surface protection film of this invention can be used suitably for surface protection, such as a member which has an unevenness | corrugation.

10 Surface protective film 1 Base material layer 2 Adhesive layer

Claims (5)

A surface protective film having a base material layer and an adhesive layer on at least one side of the base material layer,
Tensile strength at 10% tension is 14 N / 20 mm or less at 23 ° C.,
The peel adhesive strength to the SUS430BA plate is 1.0 N / 20 mm or more after 23 ° C., a pulling speed of 0.3 m / min, a peeling angle of 180 °, and 30 minutes after sticking.
The peeling adhesive strength to the SUS430BA plate is 4.0 N / 20 mm or less after 23 ° C., a tensile speed of 10 m / min, a peeling angle of 180 °, and 30 minutes after being attached.
Surface protective film.   The surface protection film of Claim 1 whose gel fraction of the said adhesive layer is 80 to 99%.   The surface protection film of Claim 1 or 2 in which the said base material layer contains polyolefin resin.   The surface protection film of Claim 3 in which the said polyolefin resin contains polyethylene. The surface protection film in any one of Claim 1 to 4 whose thickness of the said base material layer is 10-80 micrometers.