Surface protective film

Abstract

Provided is a surface protective film including an adhesive layer, wherein the surface protective film, which is affixed to an adherend such as an optical member or an electronic member, is less likely to cause damage to the adherend even when the surface protective film is peeled from the adherend at a high speed.　A surface protective film according to an embodiment of the present invention includes an adhesive layer configured from a urethane-based adhesive, wherein the urethane-based adhesive contains a urethane polymer, the urethane-based adhesive is formed from a urethane-based adhesive composition, the urethane-based adhesive composition contains a base polymer (A) and a silicone-based compound (B), the urethane polymer is a prepolymer-type urethane polymer, the base polymer (A) is a urethane prepolymer, the silicone-based compound (B) contains at least one selected from the group consisting of silicone-based compounds having a polyether structure and silicone-based compounds having a carbinol structure, and the weight-average molecular weight Mw of the silicone-based compound (B) is 2,000 or greater.

Description

Surface protection film

[0001] The present invention relates to a surface protection film.

[0002] In the manufacturing process of optical or electronic components, a surface protection film is generally attached to the exposed surface of the optical or electronic component to prevent the surface of the optical or electronic component from being damaged during processing, assembly, inspection, transportation, etc. Such a surface protection film is peeled off from the optical or electronic component when surface protection is no longer required (Patent Document 1).

[0003] When peeling the surface protection film from an optical or electronic component to which it is attached, the surface protection film must be able to be peeled off smoothly only at the interface between the surface protection film and the optical or electronic component, i.e., it must have easy peelability.

[0004] As a means for imparting easy releasability to a surface protection film, a technique of adding a fluorine-based compound or a silicone-based compound to a pressure-sensitive adhesive composition that forms the pressure-sensitive adhesive that constitutes the pressure-sensitive adhesive layer has been reported (Patent Documents 2 and 3).

[0005] Here, optical components and electronic components are generally expensive and easily damaged. Therefore, it is important that the surface protection film attached to the exposed surface of the optical component or electronic component does not damage the optical component or electronic component when peeled off. In particular, if the surface protection film attached to the exposed surface of the optical component or electronic component is peeled off at high speed in an attempt to increase productivity, there is a risk of damaging the optical component or electronic component.

[0006] Patent No. 6613516 Patent No. 6368810 Patent No. 6648168

[0007] The object of the present invention is to provide a surface protection film including a pressure-sensitive adhesive layer, which is unlikely to cause damage to an adherend, such as an optical component or an electronic component, even when the surface protection film is attached to the adherend and peeled off from the adherend at high speed.

[0008] [1] A surface protection film according to an embodiment of the present invention is a surface protection film including a pressure-sensitive adhesive layer composed of a urethane-based pressure-sensitive adhesive, wherein the urethane-based pressure-sensitive adhesive includes a urethane polymer, and the urethane-based pressure-sensitive adhesive is formed from a urethane-based pressure-sensitive adhesive composition, the urethane-based pressure-sensitive adhesive composition including a base polymer (A) and a silicone-based compound (B), wherein the urethane polymer is a prepolymer-type urethane polymer, the base polymer (A) is a urethane prepolymer, and the silicone-based compound (B) includes at least one selected from the group consisting of silicone-based compounds having a polyether structure and silicone-based compounds having a carbinol structure, and the weight-average molecular weight Mw of the silicone-based compound (B) is 2000 or more. [2] In the surface protection film according to the above [1], the urethane-based pressure-sensitive adhesive composition may include a polyfunctional isocyanate compound, and the equivalent ratio ([NCO] / [OH]) of the NCO groups of the polyfunctional isocyanate compound to the OH groups of the urethane prepolymer may be 1.50 or less. [3] In the surface protective film according to the above [1] or [2], the pressure-sensitive adhesive layer is attached to a glass plate, left for 30 minutes at an ambient temperature of 23°C, and then the surface protective film is peeled from the glass plate at a peel angle of 180° and a peel speed of 1,800 mm / min, where the average peel strength is defined as high-speed adhesive strength (I), and the pressure-sensitive adhesive layer is attached to a glass plate, left for 1 day at an ambient temperature of 50°C, and then the average peel strength is peeled from the glass plate at a peel angle of 180° and a peel speed of 1,800 mm / min, where the high-speed adhesive strength (II) is the average peel strength. [4] In the surface protective film according to any of the above [1] to [3], the silicone-based compound (B) may contain a silicone-based compound having a polyether structure. [5] In the surface protective film described in [4] above, the silicone-based compound having the polyether structure may be at least one selected from the group consisting of reactive silicone oils and non-reactive silicone oils having an HLB value of 15 or less.[6] In the surface protective film according to any one of [1] to [5] above, the weight average molecular weight Mw of the silicone compound (B) may be 10,000 or more. [7] An optical member according to an embodiment of the present invention includes the surface protective film according to any one of [1] to [6] above. [8] An electronic member according to an embodiment of the present invention includes the surface protective film according to any one of [1] to [6] above.

[0009] According to the present invention, it is possible to provide a surface protection film including a pressure-sensitive adhesive layer, which is unlikely to cause damage to an adherend, such as an optical component or an electronic component, even when the surface protection film is attached to the adherend and peeled off from the adherend at high speed.

[0010] 1 is a schematic cross-sectional view of a surface protection film according to one embodiment of the present invention.

[0011] When the expression "weight" appears in this specification, it may be read as "mass," which is commonly used as an SI unit indicating weight.

[0012] In this specification, the term "(meth)acrylic" means "acrylic and / or methacrylic", the term "(meth)acrylate" means "acrylate and / or methacrylate", the term "(meth)allyl" means "allyl and / or methallyl", and the term "(meth)acrolein" means "acrolein and / or methacrolein".

[0013] A. Surface Protection Film The surface protection film according to the embodiment of the present invention includes a pressure-sensitive adhesive layer made of a urethane-based pressure-sensitive adhesive. In the surface protection film according to the embodiment of the present invention, the urethane-based pressure-sensitive adhesive includes a urethane polymer.

[0014] In the surface protection film according to the embodiment of the present invention, the urethane-based pressure-sensitive adhesive is formed from a urethane-based pressure-sensitive adhesive composition, and the urethane-based pressure-sensitive adhesive composition contains a base polymer (A) and a silicone-based compound (B).

[0015] In the surface protection film according to the embodiment of the present invention, the total content of the base polymer (A) and the silicone compound (B) in the urethane-based pressure-sensitive adhesive composition is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 99% by weight, even more preferably 80% by weight to 98% by weight, and particularly preferably 90% by weight to 97% by weight, calculated on a solid content basis.

[0016] In the surface protection film according to the embodiment of the present invention, the content of the base polymer (A) in the urethane-based pressure-sensitive adhesive composition is preferably 60% by weight to 99.9% by weight, more preferably 70% by weight to 99% by weight, even more preferably 80% by weight to 98% by weight, and particularly preferably 90% by weight to 97% by weight, calculated as solids. When the content of the base polymer (A) in the urethane-based pressure-sensitive adhesive composition is within the above range, the effects of the present invention can be more effectively exhibited.

[0017] The surface protection film according to an embodiment of the present invention may include any other appropriate components as long as the effects of the present invention are not impaired, as long as the surface protection film according to an embodiment of the present invention includes a substrate and the above-mentioned pressure-sensitive adhesive layer. Furthermore, as described below, the surface of the pressure-sensitive adhesive layer opposite the substrate may be provided with any appropriate release liner (sometimes referred to as a release sheet or separator) for protection until use, etc.

[0018] Fig. 1 is a schematic cross-sectional view of a surface protection film according to one embodiment of the present invention. In Fig. 1, a surface protection film 10 includes a substrate 1 and a pressure-sensitive adhesive layer 2. In Fig. 1, the substrate 1 and the pressure-sensitive adhesive layer 2 are directly laminated together.

[0019] In Figure 1, any appropriate release liner (sometimes referred to as a release sheet or separator) may be provided (not shown) on the surface of the pressure-sensitive adhesive layer 2 opposite the substrate 1 for protection until use, etc. Examples of release liners include release liners in which the surface of a substrate (liner substrate) such as paper or plastic film is treated with silicone, and release liners in which the surface of a substrate (liner substrate) such as paper or plastic film is laminated with a polyolefin resin.

[0020] Examples of plastic films usable as liner substrates include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, and ethylene-vinyl acetate copolymer films.

[0021] The thickness of the release liner is preferably 1 μm to 500 μm, more preferably 3 μm to 450 μm, even more preferably 5 μm to 400 μm, and particularly preferably 10 μm to 300 μm.

[0022] The thickness of the surface protection film according to the embodiment of the present invention may be any appropriate thickness as long as the effects of the present invention are not impaired. Such a thickness is preferably 5 μm to 500 μm, more preferably 10 μm to 450 μm, even more preferably 15 μm to 400 μm, and particularly preferably 20 μm to 300 μm.

[0023] In the surface protection film according to an embodiment of the present invention, the pressure-sensitive adhesive layer is attached to a glass plate, left for 30 minutes at an ambient temperature of 23°C, and then the surface protection film is peeled from the glass plate at a peel angle of 180° and a peel speed of 1800 mm / min. The high-speed adhesive strength (I), which is the average peel strength, is preferably 10.0 gf / 25 mm or less, more preferably 8.0 gf / 25 mm or less, even more preferably 6.0 gf / 25 mm or less, even more preferably 5.5 gf / 25 mm or less, particularly preferably 5.0 gf / 25 mm or less, and most preferably 4.5 gf / 25 mm or less. From the viewpoint of ensuring proper function as a surface protection film, the lower limit of the high-speed adhesive strength (I) is preferably 0.5 gf / 25 mm or more in practice. If the high-speed adhesive strength (I) is within the above range, a surface protection film can be provided that is less likely to damage the adherend even when the surface protection film attached to the exposed surface of the adherend is peeled off at high speed. If the high-speed adhesive strength (I) is too large and outside the above range, for example, when a surface protective film attached to the exposed surface of an adherend is peeled off at high speed, the adherend may be damaged. The method for measuring the high-speed adhesive strength (I) will be described in detail later.

[0024] In the surface protection film according to an embodiment of the present invention, when the pressure-sensitive adhesive layer is attached to a glass plate, left for one day at an ambient temperature of 50° C., and then the surface protection film is peeled from the glass plate at a peel angle of 180° and a peel speed of 1,800 mm / min, the average peel strength is defined as the high-speed adhesive strength (II), and the degree of increase in adhesive strength from the high-speed adhesive strength (I), i.e., the rate of increase in high-speed adhesive strength to glass plate over time, defined as [high-speed adhesive strength (II) / high-speed adhesive strength (I)]×100(%), is preferably 300% or less, more preferably 250% or less, even more preferably 200% or less, even more preferably 180% or less, even more preferably 170% or less, even more preferably 160% or less, even more preferably 150% or less, particularly preferably 140% or less, and most preferably 130% or less. The lower limit of the rate of increase in adhesive strength to glass plate over time is preferably 100% or more. If the rate of increase in high-speed adhesive strength to glass plate over time is within the above range, the increase in high-speed adhesive strength to the adherend over time is suppressed, and a surface protective film can be provided that is less likely to damage the adherend even if the surface protective film attached to the exposed surface of the adherend is peeled off at high speed after a certain period of time after being attached to the adherend. If the rate of increase in high-speed adhesive strength to glass plate over time is too large outside the above range, the adhesive strength to the adherend will increase over time, and for example, if the surface protective film attached to the exposed surface of the adherend is peeled off at high speed after a certain period of time after being attached to the adherend, the adherend may be damaged. Details of the method for measuring the high-speed adhesive strength (II) will be described later.

[0025] The surface protection film according to an embodiment of the present invention can be manufactured by any suitable method. Examples of such manufacturing methods include: (1) a method of applying a solution or a hot-melt liquid of a material for forming a pressure-sensitive adhesive layer onto a substrate; (2) a method of applying a solution or a hot-melt liquid of a material for forming a pressure-sensitive adhesive layer onto a release liner to form a pressure-sensitive adhesive layer, and then transferring the resulting layer onto a substrate; (3) a method of extruding a material for forming a pressure-sensitive adhesive layer onto a substrate to form a coating; (4) a method of extruding a substrate and a pressure-sensitive adhesive layer in a two-layer or multi-layer configuration; (5) a method of laminating a single-layer pressure-sensitive adhesive layer onto a substrate, or a method of laminating a two-layer pressure-sensitive adhesive layer together with a laminate layer; and (6) a method of laminating a pressure-sensitive adhesive layer with a substrate-forming material such as a film or a laminate layer in a two-layer or multi-layer configuration. Any suitable method can be used as the above-mentioned coating method. Examples of the coating method that can be used include roll coater method, comma coater method, die coater method, reverse coater method, silk screen method, and gravure coater method.

[0026] <A-1. Pressure-sensitive adhesive layer> The pressure-sensitive adhesive layer is composed of a urethane-based pressure-sensitive adhesive. The urethane-based pressure-sensitive adhesive is formed from a urethane-based pressure-sensitive adhesive composition. That is, the pressure-sensitive adhesive layer is composed of a urethane-based pressure-sensitive adhesive, and the urethane-based pressure-sensitive adhesive is formed from a urethane-based pressure-sensitive adhesive composition. Typically, the urethane-based pressure-sensitive adhesive formed from the urethane-based pressure-sensitive adhesive composition forms a layer shape to become the pressure-sensitive adhesive layer.

[0027] The pressure-sensitive adhesive layer can be formed by any appropriate method. For example, a method can be mentioned in which a urethane-based pressure-sensitive adhesive composition is applied to any appropriate substrate, heated and dried as necessary, and cured as necessary to form a pressure-sensitive adhesive layer on the substrate. The application method, heating and drying conditions, curing conditions, etc. can be appropriately selected from methods commonly known for forming pressure-sensitive adhesive layers.

[0028] The thickness of the pressure-sensitive adhesive layer can be appropriately set depending on the purpose of the present invention, as long as the effects of the present invention are not impaired. The thickness of the pressure-sensitive adhesive layer is typically 5 μm to 150 μm, preferably 10 μm to 120 μm, more preferably 20 μm to 110 μm, even more preferably 30 μm to 100 μm, and particularly preferably 40 μm to 90 μm.

[0029] In the surface protection film according to the embodiment of the present invention, the urethane-based pressure-sensitive adhesive contains a urethane polymer. The urethane polymer in the urethane-based pressure-sensitive adhesive may be of one type or two or more types.

[0030] In the surface protection film according to the embodiment of the present invention, the content of the urethane polymer in the urethane-based pressure-sensitive adhesive is preferably 60% by weight to 99.9% by weight, more preferably 70% by weight to 99.9% by weight, even more preferably 80% by weight to 99.9% by weight, particularly preferably 85% by weight to 99.9% by weight, and most preferably 90% by weight to 99.9% by weight. When the content of the urethane polymer in the urethane-based pressure-sensitive adhesive is within the above range, calculated as solid content, the effects of the present invention can be more effectively exhibited.

[0031] In the surface protection film according to the embodiment of the present invention, the urethane polymer contained in the urethane-based pressure-sensitive adhesive is typically a prepolymer-type urethane polymer. The prepolymer-type urethane polymer may be of only one type or of two or more types.

[0032] Generally, known urethane polymers include "prepolymer-type urethane polymers" produced by reacting a urethane prepolymer with a polyfunctional isocyanate compound, and "one-shot-type urethane polymers" produced by directly reacting a polyol with a polyfunctional isocyanate compound without using a urethane prepolymer. Urethane prepolymers are typically obtained by reacting a polyol with an excess of a polyfunctional isocyanate compound, and have isocyanate groups at the molecular terminals. Therefore, in the surface protection film according to an embodiment of the present invention, the prepolymer-type urethane polymer, which is the urethane polymer contained in the urethane-based pressure-sensitive adhesive, is different from the one-shot-type urethane polymer.

[0033] Here, the prepolymer-type urethane polymer is obtained by reacting a urethane prepolymer as the base polymer (A) contained in a urethane-based pressure-sensitive adhesive composition with a polyfunctional isocyanate compound. Therefore, in the surface protection film according to an embodiment of the present invention, the urethane-based pressure-sensitive adhesive composition forming the urethane-based pressure-sensitive adhesive typically contains a urethane prepolymer as the base polymer (A), a polyfunctional isocyanate compound, and a silicone-based compound (B). Note that the prepolymer-type urethane polymer can be prepared by any appropriate method that is used in the urethane reaction between a urethane prepolymer as the base polymer (A) and a polyfunctional isocyanate compound, as long as the effects of the present invention are not impaired.

[0034] <A-1-1. Urethane Prepolymer as Base Polymer (A)> The urethane prepolymer as the base polymer (A) can react with a polyfunctional isocyanate compound to form a prepolymer-type urethane polymer.

[0035] The urethane prepolymer may be of one type only, or of two or more types.

[0036] The urethane prepolymer is preferably a polyurethane polyol, more preferably obtained by reacting a polyol with a polyfunctional isocyanate compound. The number average molecular weight Mn of the urethane prepolymer is, for example, 3,000 to 1,000,000.

[0037] The polyol includes at least one selected from the group consisting of polyester polyols and polyether polyols. Typically, the polyol is at least one selected from the group consisting of polyester polyols and polyether polyols. The polyester polyol may be of only one type, or may be of two or more types. The polyether polyol may be of only one type, or may be of two or more types.

[0038] As the polyester polyol, polyester polyols that can be commonly used in preparing urethane prepolymers can be appropriately used. Examples of such polyester polyols include polyester polyols obtained by reacting an acid component with a glycol component. Examples of the acid component include terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, and trimellitic acid. Examples of the glycol component include ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexane glycol, 3-methyl-1,5-pentanediol, 3,3'-dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, glycerin, trimethylolpropane, and pentaerythritol. In addition to these, examples of polyester polyols include polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, poly(β-methyl-γ-valerolactone), and polyvalerolactone.

[0039] The molecular weight of the polyester polyol may range from low to high, and the number average molecular weight Mn of the polyester polyol is, for example, 100 to 100,000, and preferably 100 to 10,000.

[0040] As the polyether polyol, polyether polyols that can be normally used in preparing urethane prepolymers can be appropriately adopted.Such polyether polyols include polyether polyols that contain two or more functional groups, such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., and typically include polyether polyols that contain two or more of at least one group selected from the group consisting of methylene groups and methine groups.If necessary, polyether polyols can be partially replaced with glycols such as ethylene glycol, polyamines such as ethylenediamine, etc.

[0041] The molecular weight of the polyether polyol may range from low to high, and the number average molecular weight Mn of the polyether polyol is, for example, 100 to 100,000, and preferably 100 to 10,000.

[0042] One embodiment of the polyol is embodiment (A) which includes both a polyester polyol and a polyether polyol. In embodiment (A), typically the polyol comprises both a polyester polyol and a polyether polyol.

[0043] In embodiment (A), the content of the polyester polyol in the polyol is preferably 0.1% by weight to 99.9% by weight, more preferably 0.1% by weight to 80% by weight, even more preferably 0.2% by weight to 60% by weight, still more preferably 0.2% by weight to 40% by weight, particularly preferably 0.3% by weight to 30% by weight, and most preferably 0.3% by weight to 20% by weight.

[0044] In embodiment (A), the content of the polyether polyol in the polyol is preferably 0.1% by weight to 99.9% by weight, more preferably 20% by weight to 99.9% by weight, even more preferably 40% by weight to 99.8% by weight, still more preferably 60% by weight to 99.8% by weight, particularly preferably 70% by weight to 99.7% by weight, and most preferably 80% by weight to 99.7% by weight.

[0045] In embodiment (A), the polyether polyol is typically a polyether polyol containing two or more of at least one group selected from the group consisting of methylene groups and methine groups. For example, it may be only a polyether polyol containing two of at least one group selected from the group consisting of methylene groups and methine groups, or it may be composed of a polyether polyol containing two of at least one group selected from the group consisting of methylene groups and methine groups and a polyether polyol containing three or more of at least one group selected from the group consisting of methylene groups and methine groups. Examples of polyether polyols containing two of at least one group selected from the group consisting of methylene groups and methine groups include polyethylene glycol and polypropylene glycol. Examples of polyether polyols containing three or more of at least one group selected from the group consisting of methylene groups and methine groups include polytetramethylene glycol.

[0046] Another embodiment of the polyol is embodiment (B) which does not include a polyester polyol but includes a polyether polyol. In embodiment (B), the polyol typically consists of a polyether polyol.

[0047] In embodiment (B), the polyether polyol is typically a polyether polyol containing two or more of at least one group selected from the group consisting of methylene groups and methine groups. For example, it may be only a polyether polyol containing two of at least one group selected from the group consisting of methylene groups and methine groups, or it may be composed of a polyether polyol containing two of at least one group selected from the group consisting of methylene groups and methine groups and a polyether polyol containing three or more of at least one group selected from the group consisting of methylene groups and methine groups. Examples of polyether polyols containing two of at least one group selected from the group consisting of methylene groups and methine groups include polyethylene glycol and polypropylene glycol. Examples of polyether polyols containing three or more of at least one group selected from the group consisting of methylene groups and methine groups include polytetramethylene glycol.

[0048] The polyfunctional isocyanate compound to be reacted with the polyol to obtain the urethane prepolymer may be one kind or two or more kinds.

[0049] The polyfunctional isocyanate compound may be any suitable polyfunctional isocyanate compound that can be used to prepare a urethane prepolymer, such as a polyfunctional aliphatic isocyanate compound, a polyfunctional alicyclic isocyanate compound, a polyfunctional aromatic isocyanate compound, or a polyfunctional araliphatic isocyanate compound.

[0050] Examples of polyfunctional aliphatic isocyanate compounds include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, 2,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0051] Examples of polyfunctional alicyclic isocyanate compounds include 3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanatemethyl)cyclohexane, 1,4-bis(isocyanatemethyl)cyclohexane, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0052] Examples of polyfunctional aromatic isocyanate compounds include 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 4,4',4"-triphenylmethane triisocyanate, dianisidine diisocyanate, and xylylene diisocyanate.

[0053] Examples of polyfunctional aromatic aliphatic isocyanate compounds include ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate.

[0054] Examples of the polyfunctional isocyanate compound include trimethylolpropane adducts of the above-mentioned various polyfunctional isocyanate compounds, biuret compounds obtained by reacting with water, and trimers having an isocyanurate ring. These may also be used in combination.

[0055] To prepare the urethane prepolymer, the polyfunctional isocyanate compound is preferably used in an equivalent ratio such that the isocyanate groups (NCO groups) of the polyol are in excess over the hydroxyl groups (OH groups) of the polyol. The NCO group / OH group equivalent ratio ([NCO] / [OH]) is preferably 1.01 to 5.0, more preferably 1.1 to 3.0, even more preferably 1.1 to 2.0, particularly preferably 1.1 to 1.8, and most preferably 1.2 to 1.6.

[0056] A catalyst may be used when preparing the urethane prepolymer. Any appropriate catalyst may be used as long as it does not impair the effects of the present invention. Examples of such catalysts include tertiary amine catalysts and organometallic catalysts. Only one type of catalyst may be used, or two or more types may be used.

[0057] Examples of the tertiary amine catalyst include triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7 (DBU).

[0058] Examples of the organometallic catalyst include bismuth-based catalysts such as bismuth octoate, bismuth neodecanoate, bismuth naphthenate, and bismuth rosinate; tin-based catalysts such as dibutyltin dilaurate (DBTDL) and dioctyltin dilaurate (DOTDL); titanium-based catalysts such as dibutyltitanium dichloride, tetrabutyl titanate, butoxytitanium trichloride, and titanium tetraacetylacetonate; iron-based catalysts such as iron 2-ethylhexanoate and iron acetylacetonate; cobalt-based catalysts such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc-based catalysts such as zinc octoate, zinc naphthenate, and zinc 2-ethylhexanoate; and zirconium-based catalysts such as zirconium naphthenate.

[0059] When a catalyst is used in preparing the urethane prepolymer, the amount of the catalyst used is preferably 0.0001 to 1.0% by weight, more preferably 0.001 to 1.0% by weight, even more preferably 0.003 to 1.0% by weight, and particularly preferably 0.005 to 1.0% by weight, based on the total amount of the polyol (a) and the polyfunctional isocyanate compound.

[0060] When a catalyst is used in preparing the urethane prepolymer, the reaction temperature is preferably less than 100° C., and more preferably 85° C. to 95° C. If the temperature is 100° C. or higher, it may become difficult to control the reaction rate and crosslinked structure.

[0061] When preparing the urethane prepolymer, it is not necessary to use a catalyst. In this case, the reaction temperature is preferably 100° C. or higher, more preferably 110° C. or higher. When preparing the urethane prepolymer without a catalyst, it is preferable to carry out the reaction for 3 hours or longer.

[0062] Any suitable method can be used to prepare the urethane prepolymer as long as it does not impair the effects of the present invention. Examples of such methods include 1) a method in which the entire amount of a polyol, a catalyst, and a polyfunctional isocyanate compound is charged into a reaction vessel, and 2) a method in which the polyol and a catalyst are charged into a reaction vessel and the polyfunctional isocyanate compound is added dropwise. In method 2), after the polyfunctional isocyanate compound has been added dropwise, additional polyol and polyfunctional isocyanate compound may be added.

[0063] Any suitable solvent may be used in preparing the urethane prepolymer, including, for example, methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone.

[0064] When preparing the urethane prepolymer, any appropriate other components may be used as long as they do not impair the effects of the present invention. Examples of other components include antioxidants, UV absorbers, light stabilizers, resin components, tackifiers, crosslinking retarders, inorganic fillers, organic fillers, metal powders, pigments, foil-like materials, softeners, antioxidants, conductive agents, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, and lubricants. The other components may be one type only or two or more types. Among the other components, antioxidants, UV absorbers, and light stabilizers are preferred embodiments.

[0065] Examples of antioxidants include radical chain inhibitors and peroxide decomposers. Examples of radical chain inhibitors include phenol-based antioxidants and amine-based antioxidants. Examples of peroxide decomposers include sulfur-based antioxidants and phosphorus-based antioxidants.

[0066] Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, oxalic acid anilide-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and triazine-based ultraviolet absorbers.

[0067] Examples of the light stabilizer include hindered amine light stabilizers.

[0068] <A-1-2. Polyfunctional Isocyanate Compound> The urethane-based pressure-sensitive adhesive composition typically contains a polyfunctional isocyanate compound. The polyfunctional isocyanate compound reacts with the base polymer (A) to form a urethane polymer. Specifically, the polyfunctional isocyanate compound can react with the urethane prepolymer serving as the base polymer (A) to form a prepolymer-type urethane polymer.

[0069] The polyfunctional isocyanate compound that reacts with the base polymer (A) may be one kind or two or more kinds.

[0070] The polyfunctional isocyanate compound to be reacted with the base polymer (A) may be any suitable polyfunctional isocyanate compound that can be used in a urethane-forming reaction, such as the polyfunctional isocyanate compounds that can be used in the preparation of the urethane prepolymer described above.

[0071] When a prepolymer-type urethane polymer is prepared by reacting a polyfunctional isocyanate compound with a urethane prepolymer as the base polymer (A), the equivalent ratio ([NCO] / [OH]) of the isocyanate groups (NCO groups) of the polyfunctional isocyanate compound to the hydroxyl groups (OH groups) of the urethane prepolymer is preferably 3.50 or less, more preferably 2.50 or less, even more preferably 2.00 or less, still more preferably 1.70 or less, still more preferably 1.00 to 1.70, still more preferably 1.10 to 1.65, particularly preferably 1.15 to 1.62, most preferably 1.15 to 1.60, or even 1.20 to 1.60, 1.25 to 1.60, 1.30 to 1.60, 1.35 to 1.60, 1.40 to 1.60, or 1.45 to 1.60. When the equivalent ratio ([NCO] / [OH]) of the isocyanate groups (NCO groups) of the polyfunctional isocyanate compound to the hydroxyl groups (OH groups) of the urethane prepolymer is within the above range, the effects of the present invention can be more effectively exhibited and the generation of glue residue when the resulting surface protection film is cut can be suppressed. If such glue residue occurs, the problem of process defects can occur easily.

[0072] When a prepolymer-type urethane polymer is prepared by reacting a polyfunctional isocyanate compound with a urethane prepolymer as the base polymer (A), the proportion of the polyfunctional isocyanate compound used relative to 100 parts by weight of the urethane prepolymer is preferably 0.5 to 15 parts by weight, more preferably 1.0 to 10 parts by weight, even more preferably 1.5 to 8.0 parts by weight, particularly preferably 1.7 to 6.0 parts by weight, and most preferably 2.0 to 5.0 parts by weight.

[0073] The urethane polymer can be prepared by any suitable method as long as it is a method of curing a urethane-based pressure-sensitive adhesive composition containing a base polymer (A) and a polyfunctional isocyanate compound to form a urethane polymer, as long as the effects of the present invention are not impaired. For example, such a method includes a method in which a urethane-based pressure-sensitive adhesive composition containing a base polymer (A) and a polyfunctional isocyanate compound is applied to any suitable substrate, heated and dried as necessary, and cured as necessary, to form a pressure-sensitive adhesive layer on the substrate. The application method, heating and drying conditions, curing conditions, etc., can be appropriately selected from methods commonly known for forming pressure-sensitive adhesive layers.

[0074] <A-1-3. Catalyst> The urethane-based pressure-sensitive adhesive composition may contain a catalyst to promote the reaction between the base polymer (A) and the polyfunctional isocyanate compound. Any appropriate catalyst may be used as the catalyst as long as it does not impair the effects of the present invention. Examples of such catalysts include the catalysts that can be used in preparing the urethane prepolymer described above.

[0075] When a catalyst is used in preparing the urethane polymer, the content of the catalyst in the urethane-based pressure-sensitive adhesive composition is, in terms of solid content, preferably 0.0001 to 1.0 part by weight, more preferably 0.001 to 1.0 part by weight, still more preferably 0.003 to 1.0 part by weight, and particularly preferably 0.005 to 1.0 part by weight, relative to 100 parts by weight of the base polymer (A).

[0076] <A-1-4. Silicone Compound (B)> The urethane-based pressure-sensitive adhesive composition contains a silicone-based compound (B). The silicone-based compound (B) may be of one type only, or may be of two or more types.

[0077] The content of the silicone compound (B) in the urethane pressure-sensitive adhesive composition, calculated as solid content, relative to 100 parts by weight of the base polymer (A), is preferably 0.001 to 20 parts by weight, more preferably 0.005 to 10 parts by weight, even more preferably 0.01 to 7 parts by weight, even more preferably 0.01 to 4 parts by weight, still more preferably 0.01 to 2 parts by weight, particularly preferably 0.01 to 1 part by weight, and most preferably 0.01 to 0.80 parts by weight. When the content of the silicone compound (B) in the urethane pressure-sensitive adhesive composition is within the above range, the effects of the present invention can be more effectively exhibited.

[0078] The silicone compound (B) typically contains at least one selected from the group consisting of reactive silicone oils and non-reactive silicone oils. The content of the at least one selected from the group consisting of reactive silicone oils and non-reactive silicone oils in the silicone compound (B) is preferably 50% to 100% by weight, more preferably 70% to 100% by weight, even more preferably 90% to 100% by weight, particularly preferably 95% to 100% by weight, and most preferably 98% to 100% by weight.

[0079] The silicone-based compound (B) may contain at least one type selected from the group consisting of reactive silicone oils and non-reactive silicone oils, as well as any other appropriate silicone-based compound within a range that does not impair the effects of the present invention.

[0080] Examples of reactive silicone oils include side-chain reactive silicone oils in which organic groups are bonded as side chains to Si atoms that participate in siloxane bonds, double-end reactive silicone oils in which organic groups are bonded to Si atoms located at both ends of the structure, single-end reactive silicone oils in which an organic group is bonded to only one of the Si atoms located at both ends of the structure, and side-chain double-end reactive silicone oils in which organic groups are bonded as side chains to Si atoms that participate in siloxane bonds and organic groups are bonded to Si atoms located at both ends of the structure.

[0081] Examples of side-chain reactive silicone oils include amino-modified side-chain reactive silicone oils, epoxy-modified side-chain reactive silicone oils, carbinol-modified side-chain reactive silicone oils, mercapto-modified side-chain reactive silicone oils, carboxyl-modified side-chain reactive silicone oils, and methylhydrogen silicone oil-type side-chain reactive silicone oils. Examples of these commercially available products include various silicone oils available on the market as side-chain reactive silicone oils manufactured by Shin-Etsu Chemical Co., Ltd.

[0082] As the double-end reactive silicone oil, for example, can be enumerated amino-modified double-end reactive silicone oil, epoxy-modified double-end reactive silicone oil, carbinol-modified double-end reactive silicone oil, methacrylic-modified double-end reactive silicone oil, polyether-modified double-end reactive silicone oil, mercapto-modified double-end reactive silicone oil, carboxyl-modified double-end reactive silicone oil, phenol-modified double-end reactive silicone oil, silanol-end double-end reactive silicone oil, acrylic-modified double-end reactive silicone oil, carboxylic anhydride-modified double-end reactive silicone oil.These commercially available products can be enumerated, for example, various silicone oils that are commercially available as double-end reactive silicone oil manufactured by Shin-Etsu Chemical Co., Ltd.

[0083] The single-end reactive silicone oil may be, for example, a single-end reactive modified type silicone oil, an average single-end carboxyl modified type silicone oil, or a specific example may be a carbinol modified type silicone oil. Examples of commercially available products of these include various silicone oils available as single-end reactive silicone oils manufactured by Shin-Etsu Chemical Co., Ltd.

[0084] Examples of the side chain both-end reactive silicone oil include side chain both-end reactive silicone oils with amino and methoxy modified side chains and epoxy modified side chain both-end reactive silicone oils. Examples of commercially available products of these include various silicone oils available as side chain both-end reactive silicone oils manufactured by Shin-Etsu Chemical Co., Ltd.

[0085] Examples of non-reactive silicone oils include side-chain type non-reactive silicone oils in which organic groups are bonded as side chains to Si atoms that contribute to siloxane bonds, and double-end type non-reactive silicone oils in which organic groups are bonded to Si atoms located at both ends of the structure.

[0086] As the side-chain type non-reactive silicone oil, for example, can be enumerated polyether-modified side-chain type non-reactive silicone oil, aralkyl-modified side-chain type non-reactive silicone oil, fluoroalkyl-modified side-chain type non-reactive silicone oil, long-chain alkyl-modified side-chain type non-reactive silicone oil, higher fatty acid ester-modified side-chain type non-reactive silicone oil, higher fatty acid-containing side-chain type non-reactive silicone oil, phenyl-modified side-chain type non-reactive silicone oil.These commercially available products can be enumerated, for example, various silicone oils that are commercially available as side-chain type non-reactive silicone oil manufactured by Shin-Etsu Chemical Co., Ltd.

[0087] Examples of the dual-end non-reactive silicone oil include polyether-modified dual-end non-reactive silicone oils, such as those commercially available as dual-end non-reactive silicone oils manufactured by Shin-Etsu Chemical Co., Ltd.

[0088] A preferred embodiment of the silicone compound (B) comprises at least one selected from the group consisting of silicone compounds having a polyether structure and silicone compounds having a carbinol structure. The content of the at least one selected from the group consisting of silicone compounds having a polyether structure and silicone compounds having a carbinol structure in the silicone compound (B) is preferably 50% to 100% by weight, more preferably 70% to 100% by weight, even more preferably 90% to 100% by weight, particularly preferably 95% to 100% by weight, and most preferably 98% to 100% by weight.

[0089] A more preferred embodiment of the silicone-based compound (B) comprises a silicone-based compound having a polyether structure. The content of the silicone-based compound having a polyether structure in the silicone-based compound (B) is preferably 50 wt % to 100 wt %, more preferably 70 wt % to 100 wt %, even more preferably 90 wt % to 100 wt %, particularly preferably 95 wt % to 100 wt %, and most preferably 98 wt % to 100 wt %. When the silicone-based compound (B) comprises a silicone-based compound having a polyether structure, it is possible to provide a surface protection film that is less likely to damage the adherend even when the surface protection film attached to the exposed surface of the adherend is peeled off at high speed.

[0090] Examples of silicone compounds having a polyether structure include the above-mentioned polyether-modified both-end reactive silicone oil, polyether-modified side-chain non-reactive silicone oil, and polyether-modified both-end non-reactive silicone oil.

[0091] Commercially available polyether-modified, dual-end reactive silicone oils include, for example, "X-22-4952," "X-22-4272," and "KF-6123" manufactured by Shin-Etsu Chemical Co., Ltd.

[0092] Commercially available polyether-modified side chain non-reactive silicone oils include, for example, "KF-351A," "KF-352A," "KF-353," "KF-354L," "KF-355A," "KF-615A," "KF-945," "KF-640," "KF-642," "KF-643," "KF-644," "KF-6020," "KF-6204," "X-22-4515," "KF-6011," "KF-6012," "KF-6015," "KF-6017," and "X-22-2516," manufactured by Shin-Etsu Chemical Co., Ltd.

[0093] An example of a commercially available polyether-modified, dual-end non-reactive silicone oil is "KF-6004" manufactured by Shin-Etsu Chemical Co., Ltd.

[0094] Examples of silicone compounds having a carbinol structure include the above-mentioned carbinol-modified side chain reactive silicone oil, carbinol-modified both terminal reactive silicone oil, and carbinol-modified one terminal reactive silicone oil.

[0095] Commercially available carbinol-modified side-chain reactive silicone oils include, for example, "X-22-4039" and "X-22-4015" manufactured by Shin-Etsu Chemical Co., Ltd.

[0096] Commercially available carbinol-modified, dual-end reactive silicone oils include, for example, "KF-6000," "KF-6001," "KF-6002," and "KF-6003" manufactured by Shin-Etsu Chemical Co., Ltd.

[0097] Commercially available carbinol-modified single-end reactive silicone oils include, for example, "X-22-170BX" and "X-22-170DX" manufactured by Shin-Etsu Chemical Co., Ltd.

[0098] One preferred embodiment of the silicone compound (B) is a silicone compound having a weight average molecular weight Mw of at least 2000. The weight average molecular weight Mw of such a silicone compound is preferably 3000 to 1000000, more preferably 4000 to 500000, even more preferably 5000 to 100000, even more preferably 8000 to 50000, even more preferably 10000 to 50000, even more preferably 12000 to 50000, even more preferably 14000 to 50000, even more preferably 16000 to 40000, even more preferably 18000 to 40000, and even more preferably 20000 to 40000. When the weight average molecular weight Mw of the silicone-based compound (B) is within the above range, the increase in high-speed adhesive strength to the adherend over time is further suppressed, and a surface protection film can be provided that is less likely to damage the adherend even if the surface protection film attached to the exposed surface of the adherend is peeled off at high speed after a period of time has passed since the surface protection film was attached to the adherend.

[0099] The silicone compound having a polyether structure that can be used as the silicone compound (B) is preferably at least one selected from the group consisting of reactive silicone oils and non-reactive silicone oils having an HLB value of not more than 15. If the silicone compound (B) is a silicone compound having a polyether structure and at least one selected from the group consisting of reactive silicone oils and non-reactive silicone oils having an HLB value of not more than 15, it is possible to provide a surface protection film that is less likely to damage the adherend even when the surface protection film attached to the exposed surface of the adherend is peeled off at high speed, and it is also possible to provide a surface protection film that is more inhibited from increasing in high-speed adhesive strength to the adherend over time, and is less likely to damage the adherend even when the surface protection film attached to the exposed surface of the adherend is peeled off at high speed after a period of time has passed since being attached to the adherend.

[0100] Among the silicone-based compounds (B) as described above, for example, non-reactive silicone oils which are silicone-based compounds having a polyether structure and have an HLB value of 15 or less are more preferred in that they can provide a surface protection film that is even less likely to damage the adherend even when the surface protection film attached to the exposed surface of the adherend is peeled off at high speed, and in that they can provide a surface protection film that is even less likely to damage the adherend even when the surface protection film attached to the exposed surface of the adherend is peeled off at high speed after a period of time has elapsed after being attached to the adherend, by further suppressing an increase in high-speed adhesive strength to the adherend over time.

[0101] Examples of silicone compounds that have a polyether structure and are reactive silicone oils include the aforementioned polyether-modified, dual-end reactive silicone oils.

[0102] As mentioned above, examples of commercially available polyether-modified dual-end reactive silicone oils include "X-22-4952," "X-22-4272," and "KF-6123" manufactured by Shin-Etsu Chemical Co., Ltd.

[0103] Examples of non-reactive silicone oils that are silicone compounds having a polyether structure and have an HLB value of 15 or less include the above-mentioned polyether-modified side-chain non-reactive silicone oils with an HLB value of 15 or less, and the above-mentioned polyether-modified double-end non-reactive silicone oils with an HLB value of 15 or less.

[0104] Examples of polyether-modified side-chain non-reactive silicone oils with an HLB value of 15 or less include "KF-351A" (HLB=12), "KF-352A" (HLB=7), "KF-353" (HLB=10), "KF-355A" (HLB=12), "KF-615A" (HLB=10), "KF-945" (HLB=4), "KF-640" (HLB=14), and "KF-642" manufactured by Shin-Etsu Chemical Co., Ltd. (HLB=12), "KF-643" (HLB=14), "KF-644" (HLB=11), "KF-6020" (HLB=4), "KF-6204" (HLB=10), "X-22-4515" (HLB=5), "KF-6011" (HLB=12), "KF-6012" (HLB=7), "KF-6015" (HLB=5), "KF-6017" (HLB=5), and "X-22-2516" (HLB=1).

[0105] An example of a polyether-modified, dual-terminal non-reactive silicone oil having an HLB value of 15 or less is "KF-6004" (HLB=9) manufactured by Shin-Etsu Chemical Co., Ltd.

[0106] <A-1-5. Other Components> The urethane-based pressure-sensitive adhesive composition may contain any appropriate other components as long as the effects of the present invention are not impaired. Examples of such other components include ionic compounds, fatty acid esters, solvents, crosslinking accelerators, silane coupling agents, antioxidants, UV absorbers, light stabilizers, resin components, tackifiers, crosslinking retarders, inorganic fillers, organic fillers, metal powders, colorants (pigments, dyes, etc.), chain transfer agents, plasticizers, softeners, antioxidants, conductive agents, foil-like materials, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, and lubricants. The other components may be of only one type, or may be of two or more types.

[0107] <A-2. Substrate> The substrate may be a single layer or may be two or more layers. The substrate may be stretched.

[0108] The thickness of the substrate is preferably 4 μm to 450 μm, more preferably 8 μm to 400 μm, still more preferably 12 μm to 350 μm, and particularly preferably 16 μm to 250 μm.

[0109] For the surface of the substrate on which the pressure-sensitive adhesive layer is not applied, a release treatment can be performed by adding a fatty acid amide, polyethyleneimine, a long-chain alkyl additive, or the like to the substrate, or a coating layer made of any appropriate release agent such as a silicone-based, long-chain alkyl-based, or fluorine-based release agent can be provided, for example, in order to form a roll that can be easily unwound.

[0110] Any appropriate material can be used as the substrate material depending on the application. Examples include plastic, paper, metal film, nonwoven fabric, etc. Plastic is preferred. That is, the substrate is preferably a plastic film. The substrate may be made of one type of material, or may be made of two or more types of materials. For example, it may be made of two or more types of plastic.

[0111] Examples of the plastic include polyester resins, polyamide resins, polyolefin resins, etc. Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.

[0112] The substrate may contain any appropriate additives as needed. Examples of additives that may be contained in the substrate include antioxidants, UV absorbers, light stabilizers, antistatic agents, fillers, and pigments. The type, number, and amount of additives that may be contained in the substrate may be appropriately set depending on the purpose. In particular, when the substrate is made of plastic, it is preferable to contain some of the above-mentioned additives for the purpose of preventing deterioration, etc. From the viewpoint of improving weather resistance, etc., particularly preferred additives include antioxidants, UV absorbers, light stabilizers, and fillers.

[0113] <<B. Uses>> The surface protective film according to an embodiment of the present invention is typically attached to an exposed surface of an optical or electronic component in the manufacturing process of the optical or electronic component to prevent the surface of the optical or electronic component from being scratched during processing, assembly, inspection, transportation, etc., and can be suitably used for surface protection of the optical or electronic component. The optical component of the present invention has the surface protective film of the present invention attached thereto. The electronic component of the present invention has the surface protective film of the present invention attached thereto.

[0114] The present invention will be specifically described below using examples, but the present invention is not limited to these examples. The test and evaluation methods used in the examples are as follows. The term "parts" means "parts by weight" unless otherwise specified, and the term "%" means "% by weight" unless otherwise specified.

[0115] <Measurement of high-speed adhesive strength (I) to glass plate (after leaving at 23°C for 30 minutes)> In an environment of 23°C and 50% RH, the release liner was peeled off from the surface protective film, and the surface protective film was cut to a width of 25 mm and a length of 140 mm. The surface protective film was then pressed against the surface of a glass plate (soda-lime glass, manufactured by Matsunami Glass Industry Co., Ltd.) using a 2 kg hand roller in one stroke to obtain a sample. After leaving the sample at an environmental temperature of 23°C for 30 minutes, the sample was placed in a tensile tester and a tensile test was initiated. The tensile test conditions were a peel angle of 180° and a peel rate (pulling rate) of 1800 mm / min in an environment of 23°C and 50% RH. The peel force (load) when the surface protective film was peeled from the glass plate was measured, and the average peel force (average load) at this time was taken as the high-speed adhesive strength (I) to glass plate (sometimes simply referred to as high-speed adhesive strength (I)). The tensile tester used was a Shimadzu Autograph AG-Xplus HS 6000 mm / min high-speed model (AG-50NX plus) manufactured by Shimadzu Corporation.

[0116] <Measurement of high-speed adhesive strength to glass plate (II) (after leaving at 50°C for 1 day)> In an environment of 23°C and 50% RH, the release liner was peeled off from the surface protective film, and the surface protective film was cut to a width of 25 mm and a length of 140 mm. The surface protective film was then pressed against the surface of a glass plate (soda-lime glass, manufactured by Matsunami Glass Industry Co., Ltd.) using a 2 kg hand roller in one stroke to obtain a sample. After leaving the sample at an environmental temperature of 50°C for 1 day, the sample was placed in a tensile tester and a tensile test was initiated. The tensile test conditions were a peel angle of 180° and a peel rate (pulling rate) of 1800 mm / min in an environment of 23°C and 50% RH. The peel force (load) when the surface protective film was peeled from the glass plate was measured, and the average peel force (average load) at this time was taken as the high-speed adhesive strength to glass plate (II) (sometimes simply referred to as high-speed adhesive strength (II)). The tensile tester used was a Shimadzu Autograph AG-Xplus HS 6000 mm / min high-speed model (AG-50NX plus) manufactured by Shimadzu Corporation.

[0117] <Calculation of the rate of increase over time in high-speed adhesive strength to glass plate> Calculation was performed using the formula [high-speed adhesive strength (II) / high-speed adhesive strength (I)]×100(%).

[0118] <Cutting ability> The release liner had been peeled off from the surface protection film (width 25 mm × length 140 mm), and the pressure-sensitive adhesive layer side of the film was cut by 1 cm using a cutter blade at a 90 degree angle. When adhesive residue was visually observed, the film was rated G (good), and when no adhesive residue was observed, the film was rated B (better).

[0119] [Production Example 1]: Production of urethane prepolymer A An experimental apparatus equipped with a 1 L round-bottom separable flask, a separable cover, a separatory funnel, a thermometer, a nitrogen inlet tube, a Liebig condenser, a vacuum seal, a stirring rod, and a stirring blade was charged with 347 g of polypropylene glycol (product name "Sanix PP-2000" manufactured by Sanyo Chemical Industries, Ltd.), 47 g of polyester polyol (product name "Kuraray Polyol P-2010" manufactured by Kuraray Co., Ltd.), 110 g of toluene (manufactured by Tosoh Corporation) as a solvent, and 0.041 g of bismuth octoate (manufactured by Nippon Chemical Industry Co., Ltd.) as a catalyst, and the mixture was purged with nitrogen at room temperature for 1 hour with stirring. Thereafter, under nitrogen flow and stirring, 33.5 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and the temperature of the solution in the experimental apparatus was maintained at 90±2°C in a water bath while maintaining the temperature for 4 hours. Thereafter, 44 g of polypropylene glycol (product name "GP1000", manufactured by Sanyo Chemical Industries, Ltd.) was added, and the temperature of the solution in the experimental apparatus was maintained at 90±2°C in a water bath while maintaining the temperature for 2 hours. Thereafter, 25.4 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and the temperature of the solution in the experimental apparatus was maintained at 90±2°C in a water bath while maintaining the temperature for 2 hours, thereby obtaining a solution of urethane prepolymer A. Note that toluene was added dropwise as needed during the polymerization to control the temperature during polymerization and to prevent a decrease in stirrability due to an increase in viscosity. The total amount of toluene added was 380 g. The solids concentration of the urethane prepolymer A solution was 50 wt%.

[0120] Example 1 100 parts by weight of urethane prepolymer A, 3.0 parts by weight of a polyfunctional isocyanate compound (Coronate HX (C / HX), manufactured by Nippon Polyurethane Industries Co., Ltd.) as a crosslinking agent, 0.10 parts by weight of KF-354L (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silicone compound, 0.50 parts by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, and 0.20 parts by weight of Nikka Octix Zinc 18% (manufactured by Nippon Chemical Industry Co., Ltd.) as a catalyst were blended and diluted with ethyl acetate to a total solids content of 50% by weight to obtain a urethane-based pressure-sensitive adhesive composition (1). The urethane-based pressure-sensitive adhesive composition (1) was applied to a polyester resin substrate (product name "T100-75S", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) to a thickness of 75 μm after drying, and cured and dried at a drying temperature of 150° C. for 3 minutes to produce a pressure-sensitive adhesive layer (1). Next, the silicone-treated surface of a release liner (trade name "MRF25", thickness 25 μm, manufactured by Mitsubishi Chemical Corporation) made of a 25 μm thick polyester resin with one side silicone-treated was laminated to the surface of the obtained pressure-sensitive adhesive layer (1) to obtain a surface protection film (1). Aging was carried out at room temperature for 5 days, and various evaluations were carried out. The results are shown in Tables 1 and 2.

[0121] Example 2 100 parts by weight of urethane prepolymer A, 3.0 parts by weight of a polyfunctional isocyanate compound (Coronate HX (C / HX), manufactured by Nippon Polyurethane Industries Co., Ltd.) as a crosslinking agent, 0.10 parts by weight of KF-6001 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silicone compound, 0.50 parts by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, and 0.20 parts by weight of Nikka Octix Zinc 18% (manufactured by Nippon Chemical Industry Co., Ltd.) as a catalyst were blended and diluted with ethyl acetate to a total solids content of 50% by weight to obtain a urethane-based pressure-sensitive adhesive composition (2). The same procedure as in Example 1 was carried out, except that the urethane-based pressure-sensitive adhesive composition (2) was used instead of the urethane-based pressure-sensitive adhesive composition (1), to obtain a pressure-sensitive adhesive layer (2) and a surface protective film (2). Aging was carried out at room temperature for 5 days, and various evaluations were performed. The results are shown in Tables 1 and 2.

[0122] Example 3 100 parts by weight of urethane prepolymer A, 3.0 parts by weight of a polyfunctional isocyanate compound (Coronate HX (C / HX), manufactured by Nippon Polyurethane Industries Co., Ltd.) as a crosslinking agent, 0.10 parts by weight of X-22-4272 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silicone compound, 0.50 parts by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, and 0.20 parts by weight of Nikka Octix Zinc 18% (manufactured by Nippon Chemical Industry Co., Ltd.) as a catalyst were blended and diluted with ethyl acetate to a total solids content of 50% by weight to obtain a urethane-based pressure-sensitive adhesive composition (3). The same procedure as in Example 1 was carried out, except that the urethane-based pressure-sensitive adhesive composition (3) was used instead of the urethane-based pressure-sensitive adhesive composition (1), to obtain a pressure-sensitive adhesive layer (3) and a surface protective film (3). Aging was carried out at room temperature for 5 days, and various evaluations were performed. The results are shown in Tables 1 and 2.

[0123] Example 4 100 parts by weight of urethane prepolymer A, 3.0 parts by weight of a polyfunctional isocyanate compound (Coronate HX (C / HX), manufactured by Nippon Polyurethane Industries Co., Ltd.) as a crosslinking agent, 0.10 parts by weight of KF-615A (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silicone compound, 0.50 parts by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, and 0.20 parts by weight of Nikka Octix Zinc 18% (manufactured by Nippon Chemical Industry Co., Ltd.) as a catalyst were blended and diluted with ethyl acetate to a total solids content of 50% by weight to obtain a urethane-based pressure-sensitive adhesive composition (4). The procedure of Example 1 was repeated except that the urethane-based pressure-sensitive adhesive composition (4) was used instead of the urethane-based pressure-sensitive adhesive composition (1), to obtain a pressure-sensitive adhesive layer (4) and a surface protection film (4). Aging was performed at room temperature for 5 days, and various evaluations were performed. The results are shown in Tables 1 and 2.

[0124] Example 5 100 parts by weight of urethane prepolymer A, 6.0 parts by weight of a polyfunctional isocyanate compound (Coronate HX (C / HX), manufactured by Nippon Polyurethane Industries Co., Ltd.) as a crosslinking agent, 0.10 parts by weight of KF-615A (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silicone compound, 0.50 parts by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, and 0.20 parts by weight of Nikka Octix Zinc 18% (manufactured by Nippon Chemical Industry Co., Ltd.) as a catalyst were blended and diluted with ethyl acetate to a total solids content of 50% by weight to obtain a urethane-based pressure-sensitive adhesive composition (5). The procedure of Example 1 was repeated except that the urethane-based pressure-sensitive adhesive composition (5) was used instead of the urethane-based pressure-sensitive adhesive composition (1), to obtain a pressure-sensitive adhesive layer (5) and a surface protective film (5). Aging was performed at room temperature for 5 days, and various evaluations were performed. The results are shown in Tables 1 and 2.

[0125] Comparative Example 1 100 parts by weight of urethane prepolymer B, 3.0 parts by weight of a polyfunctional isocyanate compound (Coronate HX (C / HX), manufactured by Nippon Polyurethane Industries Co., Ltd.) as a crosslinking agent, 0.10 parts by weight of KF-640 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a silicone compound, 0.50 parts by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, and 0.20 parts by weight of Nikka Octix Zinc 18% (manufactured by Nippon Chemical Industry Co., Ltd.) as a catalyst were blended and diluted with ethyl acetate to a total solids content of 50% by weight to obtain a urethane-based pressure-sensitive adhesive composition (C1). The same procedure as in Example 1 was carried out, except that the urethane-based pressure-sensitive adhesive composition (C1) was used instead of the urethane-based pressure-sensitive adhesive composition (1), to obtain a pressure-sensitive adhesive layer (C1) and a surface protective film (C1). Aging was carried out at room temperature for 5 days, and various evaluations were performed. The results are shown in Tables 1 and 2.

[0126]

[0127]

[0128] [Examples 6 to 10] For each of the surface protection films (1) to (5) obtained in Examples 1 to 5, the release liner was peeled off, and the pressure-sensitive adhesive layer side was attached to a polarizing plate (manufactured by Nitto Denko Corporation, product name "TEG1465DUHC"), which is an optical member, to obtain an optical member with the surface protection film attached.

[0129] [Examples 11 to 15] For each of the surface protection films (1) to (5) obtained in Examples 1 to 5, the release liner was peeled off, and the pressure-sensitive adhesive layer side was attached to a conductive film (manufactured by Nitto Denko Corporation, product name "ELECRYSTA V270L-TFMP"), which is an electronic component, to obtain an electronic component with a surface protection film attached thereto.

[0130] The surface protective film of the present invention can be used for any suitable application, and is preferably used in the fields of optical members and electronic members.

Claims

1. A surface protection film comprising an adhesive layer composed of a urethane-based adhesive, the urethane-based adhesive comprising a urethane polymer, the urethane-based adhesive being formed from a urethane-based adhesive composition, the urethane-based adhesive composition comprising a base polymer (A) and a silicone-based compound (B), the urethane polymer being a prepolymer-type urethane polymer, the base polymer (A) being a urethane prepolymer, the silicone-based compound (B) comprising at least one selected from the group consisting of silicone-based compounds having a polyether structure and silicone-based compounds having a carbinol structure, and the weight-average molecular weight Mw of the silicone-based compound (B) being 2000 or more.

2. The surface protection film according to claim 1, wherein the urethane-based adhesive composition contains a polyfunctional isocyanate compound, and the equivalent ratio ([NCO] / [OH]) of the NCO group of the polyfunctional isocyanate compound to the OH group of the urethane prepolymer is 1.50 or less.

3. The surface protection film according to claim 1, wherein the adhesive layer is attached to a glass plate, left for 30 minutes at an environmental temperature of 23°C, and then the surface protection film is peeled off from the glass plate at a peel angle of 180° and a peel speed of 1800 mm / min, the average peel force being defined as high-speed adhesive strength (I), and the adhesive layer is attached to a glass plate, left for 1 day at an environmental temperature of 50°C, and then the average peel force being peeled off from the glass plate at a peel angle of 180° and a peel speed of 1800 mm / min, the high-speed adhesive strength (II), wherein the rate of increase over time in the high-speed adhesive strength to the glass plate, defined as [high-speed adhesive strength (II) / high-speed adhesive strength (I)] x 100 (%), is 200% or less.

4. The surface protective film according to claim 1, wherein the silicone compound (B) comprises a silicone compound having a polyether structure.

5. The surface protective film according to claim 4, wherein the silicone compound having a polyether structure is at least one selected from the group consisting of reactive silicone oils and non-reactive silicone oils having an HLB value of 15 or less.

6. The surface protective film according to claim 1, wherein the weight average molecular weight Mw of the silicone compound (B) is 10,000 or more.

7. An optical member comprising the surface protective film according to any one of claims 1 to 6.

8. An electronic component comprising the surface protection film according to any one of claims 1 to 6.

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