Surface protective film

Abstract

Provided is a surface protective film which includes an adhesive layer, which has a sufficient adhesive force with respect to an adherend but can be smoothly peeled from the adherend without causing contamination or breakage to the adherend when the surface protective film needs to be peeled from the adherend, and which has excellent cutting properties during processing.　A surface protective film according to an embodiment of the present invention comprises an adhesive layer. An adhesive which constitutes the adhesive layer is formed from an adhesive composition. The adhesive composition contains a urethane prepolymer (A), a crosslinking agent (B), a urethane (meth)acrylate (C), and a photopolymerization initiator (D). The urethane prepolymer (A) has a polymerizable unsaturated double bond.

Description

Surface protection film

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

[0002] In the manufacturing process of optical devices or electronic devices, 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 necessary (Patent Document 1).

[0003] Surface protection films attached to the exposed surfaces of such optical or electronic components must have sufficient adhesion so that they do not easily peel off while surface protection is required, but it is also important that the surface protection film can be smoothly peeled off from the optical or electronic component without causing contamination or damage once surface protection is no longer required.

[0004] As a technique for adjusting adhesive strength, a surface protection film has been reported that includes a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive composition in which a urethane acrylate oligomer having a weight-average molecular weight of 1,000 to 15,000 is added to a specific acrylic copolymer (Patent Document 2). However, the surface protection film reported in Patent Document 2 has a problem in that it has poor cuttability during processing.

[0005] As another technique for adjusting adhesive strength, a pressure-sensitive adhesive obtained by adding a specific radically polymerizable monomer containing a (meth)acryloyl group and an active hydrogen group to a specific urethane prepolymer has been reported (Patent Document 3). However, the pressure-sensitive adhesive reported in Patent Document 3 has a problem in that it has low adhesive strength before UV irradiation and is prone to peeling while surface protection is required.

[0006] As yet another technique for adjusting adhesive strength, a pressure-sensitive adhesive obtained from an adhesive composition obtained by adding a polyfunctional (meth)acrylate to a urethane prepolymer having two or more hydroxyl groups and a (meth)acryloyloxy group has been reported (Patent Document 4). However, the pressure-sensitive adhesive reported in Patent Document 4 also has the problem that the adhesive strength before UV irradiation is low and it is prone to peeling while surface protection is required.

[0007] Patent No. 6613516 Patent No. 6092161 Patent No. 6769503 Patent No. 7285072

[0008] An object of the present invention is to provide a surface protection film including a pressure-sensitive adhesive layer, which is primarily used in the manufacturing process of optical devices or electronic devices to be attached to exposed surfaces to prevent scratches on the surfaces of optical or electronic components during processing, assembly, inspection, transportation, etc., and which ensures sufficient adhesion to the adherend, while allowing smooth release without contaminating or damaging the adherend when it is necessary to release it from the adherend, and which has excellent cutting properties during processing.Another object of the present invention is to provide an optical device or electronic device including such a surface protection film.

[0009] [1] A surface protection film according to an embodiment of the present invention is a surface protection film including a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition including a urethane prepolymer (A), a crosslinking agent (B), a urethane (meth)acrylate (C), and a photopolymerization initiator (D), and the urethane prepolymer (A) has a polymerizable unsaturated double bond. [2] In the surface protection film described in [1] above, the urethane (meth)acrylate (C) may have three or more functional groups. [3] In the surface protection film described in [1] or [2] above, the urethane (meth)acrylate (C) may have a structure represented by the following general formula (1): [4] In the surface protective film according to any one of [1] to [3] above, the urethane (meth)acrylate (C) may have a structure represented by the following general formula (2), where X is a divalent aromatic group or a divalent aliphatic group: [5] In the surface protective film according to any one of [1] to [4] above, the molecular weight of the urethane (meth)acrylate (C) may be less than 1000. [6] In the surface protective film according to any one of [1] to [5] above, the pressure-sensitive adhesive layer included in the surface protective film may be attached to the surface of a glass plate, left for 30 minutes in an environment at a temperature of 23°C and a humidity of 55% RH, and then the surface protective film may have an adhesive strength of 500 gf / 25 mm or more when peeled from the glass plate surface at a peel angle of 180° and a peel rate of 300 mm / min in an environment at a temperature of 23°C and a humidity of 55% RH. [7] In the surface protective film according to any one of [1] to [6] above, the pressure-sensitive adhesive layer included in the surface protective film may be attached to the surface of a glass plate, and left for 30 minutes in an environment at a temperature of 23°C and a humidity of 55% RH. 2 and leaving it for 30 minutes in an environment of a temperature of 23°C and a humidity of 55% RH, and then peeling the surface protection film from the surface of the glass plate at a peel angle of 180 degrees and a peel rate of 300 mm / min in an environment of a temperature of 23°C and a humidity of 55% RH, the adhesive strength may be 20.00 gf / 25 mm or less. [8] An optical device according to an embodiment of the present invention includes the surface protection film described in any of [1] to [7] above. [9] An electronic device according to an embodiment of the present invention includes the surface protection film described in any of [1] to [7] above.

[0010] According to the present invention, it is possible to provide a surface protection film including a pressure-sensitive adhesive layer, which is primarily used in the manufacturing process of optical devices or electronic devices to be attached to exposed surfaces to prevent scratches on the surfaces of optical or electronic components during processing, assembly, inspection, transportation, etc., and which ensures sufficient adhesion to an adherend, while allowing smooth peeling without contaminating or damaging the adherend when peeling from the adherend is required, and which has excellent cutting properties during processing.It is also possible to provide optical devices and electronic devices including such a surface protection film.

[0011] 1 is a schematic cross-sectional view of a surface protection film according to one embodiment of the present invention.

[0012] When the expression "weight" appears in this specification, it may be read as "mass," which is commonly used as an SI unit indicating weight.

[0013] In this specification, the expression "(meth)acrylic" means "acrylic and / or methacrylic", the expression "(meth)acrylate" means "acrylate and / or methacrylate", the expression "(meth)acryloyl" means "acryloyl and / or methacryloyl", the expression "(meth)allyl" means "allyl and / or methallyl", and the expression "(meth)acrolein" means "acrolein and / or methacrolein".

[0014] A. Surface Protection Film The surface protection film according to an embodiment of the present invention includes a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer may be a single-layer pressure-sensitive adhesive layer, or may be a two or more-layer pressure-sensitive adhesive layer.

[0015] The surface protection film according to an embodiment of the present invention may include any appropriate other layer (member) as long as it includes a pressure-sensitive adhesive layer and does not impair the effects of the present invention. Such other layer may be a single layer or two or more layers. Examples of such other layers include a substrate layer and a release liner (sometimes referred to as a release sheet or separator). Typically, the surface protection film of the present invention includes a substrate layer and a pressure-sensitive adhesive layer.

[0016] 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 base layer 1 and a pressure-sensitive adhesive layer 2. In Fig. 1, the base layer 1 and the pressure-sensitive adhesive layer 2 are directly laminated together. In Fig. 1, any appropriate release liner (sometimes referred to as a release sheet or separator) may be provided on the surface of the pressure-sensitive adhesive layer 2 opposite the base layer 1 for protection until use, etc. (not shown).

[0017] As described above, a surface protection film according to one embodiment of the present invention has a laminate structure in which a base layer, a pressure-sensitive adhesive layer, and a release liner are laminated in this order, with the release liner being the outermost layer.A surface protection film according to another embodiment of the present invention has a laminate structure in which a base layer and a pressure-sensitive adhesive layer are laminated in this order, with the pressure-sensitive adhesive layer being the outermost layer.

[0018] The thickness of the surface protection film according to the embodiment of the present invention is preferably 5 μm to 500 μm, and may be 10 μm to 450 μm, 15 μm to 400 μm, or 20 μm to 300 μm.

[0019] The surface protection film according to an embodiment of the present invention has an adhesive strength (hereinafter sometimes referred to as "initial adhesive strength to glass plate before UV irradiation") of preferably 500 gf / 25 mm or more, optionally 550 gf / 25 mm or more, optionally 600 gf / 25 mm or more, or optionally 650 gf / 25 mm or more when the adhesive layer contained in the surface protection film is attached to the surface of a glass plate and left for 30 minutes in an environment of a temperature of 23°C and a humidity of 55% RH, and then the surface protection film is peeled from the surface of the glass plate at a peel angle of 180 degrees and a peel rate of 300 mm / min in an environment of a temperature of 23°C and a humidity of 55% RH. The higher the adhesive strength to the glass plate before UV irradiation, the better. However, if it is too high, sufficient easy peelability may not be exhibited even when irradiated with ultraviolet light. Therefore, the upper limit is preferably, for example, 5000 gf / 25 mm or less, and may be 4000 gf / 25 mm or less, 3500 gf / 25 mm or less, or 3000 gf / 25 mm or less. If the initial adhesive strength to the glass plate before UV irradiation is within the above range, the surface protective film according to an embodiment of the present invention can ensure sufficient adhesion to the adherend. If the initial adhesive strength to the glass plate before UV irradiation is too low outside the above range, the surface protective film may peel off from the adherend while surface protection is required. Details of the method for measuring the initial adhesive strength to the glass plate before UV irradiation will be described later.

[0020] The surface protection film according to the embodiment of the present invention is a surface protection film in which an adhesive layer included in the surface protection film is attached to the surface of a glass plate, and an integrated light amount of 700 mJ / cm is emitted from an LED light source with a wavelength of 365 nm. 2The adhesive strength (hereinafter sometimes referred to as "initial adhesive strength after UV irradiation to glass plate") when the surface protective film is irradiated with ultraviolet light of 100 nm or less, left for 30 minutes in an environment at a temperature of 23°C and a humidity of 55% RH, and then peeled from the glass plate surface at a peel angle of 180° and a peel rate of 300 mm / min in an environment at a temperature of 23°C and a humidity of 55% RH is preferably 20.00 gf / 25 mm or less, or may be 16.00 gf / 25 mm or less, 12.00 gf / 25 mm or less, 10.00 gf / 25 mm or less, 8.00 gf / 25 mm or less, or 7.00 gf / 25 mm or less. The lower the initial adhesive strength after UV irradiation to glass plate, the better, but if it is too low, there is a risk of spontaneous peeling from the adherend in unintended circumstances. Therefore, the lower limit is preferably 1.00 gf / 25 mm or more, and may be 2.00 gf / 25 mm or more, 2.50 gf / 25 mm or more, or 3.00 gf / 25 mm or more. If the initial adhesive strength after UV irradiation to glass plate is within the above range, the adhesive strength is very low, so that the surface protective film according to an embodiment of the present invention can be smoothly peeled off from the adherend without causing contamination or damage to the adherend when it needs to be peeled off. If the initial adhesive strength after UV irradiation to glass plate is too high outside the above range, there is a risk of contamination or damage to the adherend when attempting to peel it off from the adherend. Details of the method for measuring the initial adhesive strength after UV irradiation to glass plate will be described later.

[0021] The surface protection film according to the embodiment of the present invention can be produced by any suitable method, for example, a known method for producing a surface protection film including a substrate layer and a pressure-sensitive adhesive layer.

[0022] The pressure-sensitive adhesive layer included in the surface protection film according to an embodiment of the present invention may be formed by a formation method generally referred to as a "direct method" or a formation method generally referred to as a "transfer method." The direct method is a method in which a pressure-sensitive adhesive composition is applied to a base layer, and if necessary, heating or the like, irradiation with active energy rays (such as ultraviolet rays), drying, etc. are performed to form a pressure-sensitive adhesive layer. The transfer method is a method in which a pressure-sensitive adhesive composition is applied to a release paper or the like, and if necessary, heating or the like, irradiation with active energy rays (such as ultraviolet rays), drying, etc. are performed to form a pressure-sensitive adhesive layer, and the formed pressure-sensitive adhesive layer is transferred to the base layer.

[0023] Examples of the application method include a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, air knife coater, spray coater, comma coater, direct coater, and roll brush coater.

[0024] The above heating and drying conditions can be appropriately selected from methods commonly known for forming a pressure-sensitive adhesive layer.

[0025] <A-1. Release Liner> Any appropriate release liner can be used as the release liner as long as it does not impair the effects of the present invention. Examples of such release liners include known release liners that are bonded to the surface of a pressure-sensitive adhesive layer included in a surface protection film. Examples of such 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.

[0026] 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.

[0027] The thickness of the release liner is preferably 1 μm to 500 μm, and may be 3 μm to 450 μm, 5 μm to 400 μm, or 10 μm to 300 μm.

[0028] <A-2. Pressure-sensitive adhesive layer> The pressure-sensitive adhesive layer is composed of a pressure-sensitive adhesive. The pressure-sensitive adhesive is formed from a pressure-sensitive adhesive composition. That is, the pressure-sensitive adhesive layer is composed of a pressure-sensitive adhesive, and the pressure-sensitive adhesive is formed from a pressure-sensitive adhesive composition. In other words, the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition forms a layer shape to become the pressure-sensitive adhesive layer.

[0029] The thickness of the pressure-sensitive adhesive layer is preferably 5 μm to 150 μm, may be 10 μm to 130 μm, may be 30 μm to 120 μm, may be 50 μm to 100 μm, or may be 60 μm to 90 μm, in terms of being able to further exhibit the effects of the present invention.

[0030] The pressure-sensitive adhesive composition contains a urethane prepolymer (A), a crosslinking agent (B), a urethane (meth)acrylate (C), and a photopolymerization initiator (D). In an embodiment of the present invention, the effects of the present invention can be achieved by using the urethane prepolymer (A), the crosslinking agent (B), the urethane (meth)acrylate (C), and the photopolymerization initiator (D) in combination as components contained in the pressure-sensitive adhesive composition, preferably by selecting the type of each component as described below or adjusting the amount used.

[0031] <A-2-1. Urethane prepolymer (A)> The urethane prepolymer (A) corresponds to a polymer component generally called a base polymer as a component of a pressure-sensitive adhesive composition. The urethane prepolymer (A) may be of one type only, or may be of two or more types.

[0032] The content of the urethane prepolymer (A) in the pressure-sensitive adhesive composition is preferably 50% by weight to 99.9% by weight, or may be 55% by weight to 95% by weight, or may be 60% by weight to 90% by weight, in terms of solid content. When the content of the urethane prepolymer (A) in the pressure-sensitive adhesive composition is within the above range in terms of solid content, the effects of the present invention can be more effectively exhibited.

[0033] The urethane prepolymer (A) can typically react with a crosslinking agent (B) (preferably a polyfunctional isocyanate compound) to form a urethane resin. More specifically, the urethane resin can be formed from a pressure-sensitive adhesive composition containing the urethane prepolymer (A) and the crosslinking agent (B). More specifically, the urethane resin can be formed by curing a pressure-sensitive adhesive composition containing the urethane prepolymer (A) and the crosslinking agent (B). As a method for forming a urethane resin by curing a pressure-sensitive adhesive composition containing the urethane prepolymer (A) and the crosslinking agent (B), any appropriate method can be used as long as it does not impair the effects of the present invention, such as a urethanization reaction method using bulk polymerization or solution polymerization.

[0034] As is generally well known, there are two types of manufacturing methods for urethane resins: the "one-shot method," in which a urethane resin is manufactured by directly reacting a polyol with a crosslinking agent (preferably a polyfunctional isocyanate compound) without using a urethane prepolymer, and the "prepolymer method," in which a urethane resin is manufactured by reacting a urethane prepolymer with a crosslinking agent (preferably a polyfunctional isocyanate compound). In the present invention, the urethane prepolymer (A) as the base polymer refers to the urethane prepolymer that is reacted with a crosslinking agent (preferably a polyfunctional isocyanate compound) in the "prepolymer method," and is different from the polyol that is reacted with the polyfunctional isocyanate in the "one-shot method."

[0035] The urethane prepolymer (A) may be used alone or in combination of two or more kinds.

[0036] The number average molecular weight Mn of the urethane prepolymer (A) is preferably 3,000 to 1,000,000.

[0037] In an embodiment of the present invention, the urethane prepolymer (A) has a polymerizable unsaturated double bond. The urethane prepolymer (A) having a polymerizable unsaturated double bond can further enhance the effects of the present invention. Examples of the polymerizable unsaturated double bond include a vinyl group, a (meth)allyl group, and a (meth)acryloyl group. A (meth)acryloyl group is preferred because it can further enhance the effects of the present invention. The (meth)acryloyl group is at least one selected from the group consisting of an acryloyl group and a methacryloyl group.

[0038] The urethane prepolymer (A) is preferably a polyurethane polyol.

[0039] The urethane prepolymer (A) is preferably a polymer obtained by reacting a composition containing a polyol, a compound having a polymerizable unsaturated double bond, and a crosslinking agent (preferably a polyfunctional isocyanate compound). This reaction may be carried out in the presence or absence of a catalyst.

[0040] In the description of the embodiments of the present invention, the "polyol" refers to a polyol that does not contain a polymerizable unsaturated double bond. Therefore, a compound having a polymerizable unsaturated double bond and multiple hydroxyl groups is considered to be a "compound having a polymerizable unsaturated double bond" rather than a "polyol" in the embodiments of the present invention.

[0041] The polyol preferably includes at least one selected from the group consisting of polyester polyol (a1) and polyether polyol (a2). The polyester polyol (a1) may be used alone or in combination of two or more. The polyether polyol (a2) may be used alone or in combination of two or more.

[0042] The content of the polyol in the composition for preparing the urethane prepolymer (A) (a composition containing a polyol, a compound having a polymerizable unsaturated double bond, and a crosslinking agent) is preferably 50% by weight to 99% by weight, alternatively 60% by weight to 98% by weight, 70% by weight to 97% by weight, 80% by weight to 96% by weight, or 85% by weight to 95% by weight, calculated as solid content.

[0043] The content of at least one selected from the group consisting of polyester polyol (a1) and polyether polyol (a2) in the polyol is preferably 50% by weight to 100% by weight, may be 70% by weight to 100% by weight, may be 80% by weight to 100% by weight, may be 90% by weight to 100% by weight, or may be 95% by weight to 100% by weight.

[0044] As the polyester polyol (a1), polyester polyols that can be commonly used in the production of urethane prepolymers can be appropriately used. Examples of such polyester polyols (a1) 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.

[0045] The molecular weight of the polyester polyol (a1) may range from low to high. The number average molecular weight Mn of the polyester polyol (a1) is preferably 100 to 100,000, and may be 100 to 10,000.

[0046] As the polyether polyol (a2), polyether polyols that can be normally used in the production of urethane prepolymers can be appropriately used. Examples of such polyether polyols (a2) include polyether polyols containing two or more functional groups, such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and representative examples include polyether polyols containing two or more groups of at least one type selected from the group consisting of a methylene group (-CH2-) and a methine group (-CH(CH3)-). If necessary, the polyether polyols can be used in combination by replacing a portion thereof with glycols such as ethylene glycol or polyvalent amines such as ethylenediamine.

[0047] The molecular weight of the polyether polyol (a2) may range from low to high. The number average molecular weight Mn of the polyether polyol (a2) is preferably 100 to 100,000, and may be 100 to 10,000.

[0048] As the polyether polyol (a2), only a bifunctional polyether polyol may be used, or a polyether polyol having a number average molecular weight Mn of 100 to 100,000 and at least three hydroxyl groups per molecule may be used in part or in whole.

[0049] One embodiment of the polyol is embodiment (A) which includes both a polyester polyol (a1) and a polyether polyol (a2).

[0050] In embodiment (A), the polyether polyol (a2) 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.

[0051] In embodiment (A), the content of polyester polyol (a1) in the polyol is preferably 0.1% by weight to 99.9% by weight, and may be 0.1% by weight to 80% by weight, 0.2% by weight to 60% by weight, 0.2% by weight to 40% by weight, 0.3% by weight to 30% by weight, or 0.3% by weight to 20% by weight.

[0052] In embodiment (A), the content of polyether polyol (a2) in the polyol is preferably 0.1% by weight to 99.9% by weight, may be 20% by weight to 99.9% by weight, may be 40% by weight to 99.8% by weight, may be 60% by weight to 99.8% by weight, may be 70% by weight to 99.7% by weight, or may be 80% by weight to 99.7% by weight.

[0053] Another embodiment of the polyol is embodiment (B) which does not contain polyester polyol (a1) but contains polyether polyol (a2). In embodiment (B), the polyol typically consists of polyether polyol (a2).

[0054] In embodiment (B), the content of the polyether polyol (a2) in the polyol is preferably 50% by weight to 100% by weight, may be 70% by weight to 100% by weight, may be 90% by weight to 100% by weight, may be 95% by weight to 100% by weight, or may be 98% by weight to 100% by weight.

[0055] 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.

[0056] As the compound having a polymerizable unsaturated double bond, any appropriate compound can be adopted as long as it has a polymerizable unsaturated double bond and does not impair the effects of the present invention. The compound having a polymerizable unsaturated double bond may be only one type, or may be two or more types. Examples of such a compound having a polymerizable unsaturated double bond include a compound having a vinyl group, a compound having a (meth)allyl group, and a compound having a (meth)acryloyl group. In terms of being able to further exhibit the effects of the present invention, a compound having a (meth)acryloyl group is preferred. The number of polymerizable unsaturated double bonds possessed by the compound having a polymerizable unsaturated double bond may be only one, or may be two or more.

[0057] The content of the compound having a polymerizable unsaturated double bond in the composition is preferably 0.01 parts by weight to 50 parts by weight, and may be 0.1 parts by weight to 30 parts by weight, relative to 100 parts by weight of the polyol, in terms of being able to further exhibit the effects of the present invention.

[0058] Examples of the compound having a (meth)acryloyl group include (meth)acrylic acid esters. Examples of the (meth)acrylic acid ester include (meth)acrylic acid alkyl esters, hydroxyl group-containing (meth)acrylic acid esters, and nitrogen atom-containing (meth)acrylic acid esters. Hydroxyl group-containing (meth)acrylic acid esters are preferred in that they can further exhibit the effects of the present invention.

[0059] Examples of hydroxyl group-containing (meth)acrylic acid esters include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2,3-hydroxypropyl (meth)acrylate, glycerin mono(meth)acrylate, glycerin di(meth)acrylate, cyclohexanedimethanol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and isocyanamides. Examples thereof include nuric acid EO- or PO-modified (meth)acrylate, isocyanuric acid EO- or PO-modified di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, polypentaerythritol penta(meth)acrylate, dipentaerythritol EO- or PO-modified penta(meth)acrylate, dipentaerythritol caprolactone-modified penta(meth)acrylate, and epoxy (meth)acrylate obtained by reacting the epoxy group of an epoxy compound with the carboxyl group of (meth)acrylic acid.

[0060] Among the hydroxyl group-containing (meth)acrylic acid esters, hydroxyl group-containing (meth)acrylic acid esters having two or more hydroxyl groups are preferred in that they can further exert the effects of the present invention.

[0061] As the crosslinking agent, any appropriate crosslinking agent that can be used in the production of a urethane prepolymer can be used as long as it does not impair the effects of the present invention. Such a crosslinking agent is preferably a polyfunctional isocyanate compound. The polyfunctional isocyanate compound may be used alone or in combination of two or more types.

[0062] As the polyfunctional isocyanate compound, any appropriate polyfunctional isocyanate compound can be used as long as it does not impair the effects of the present invention. Examples of such polyfunctional isocyanate compounds include polyfunctional aliphatic isocyanate compounds, polyfunctional alicyclic isocyanate compounds, polyfunctional aromatic isocyanate compounds, and polyfunctional aromatic-aliphatic isocyanate compounds.

[0063] 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.

[0064] 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, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] The amount of the crosslinking agent that can be used to obtain the urethane prepolymer (A) is preferably 0.001 to 50 parts by weight, and may be 0.01 to 30 parts by weight, 0.1 to 20 parts by weight, 1 to 15 parts by weight, or 4 to 12 parts by weight, relative to 100 parts by weight of the polyol.

[0069] A catalyst may be used when preparing the urethane prepolymer (A). Any appropriate catalyst may be used when preparing the urethane prepolymer (A). Examples of such catalysts include tertiary amine compounds and organometallic compounds. Only one type of catalyst may be used, or two or more types may be used.

[0070] Examples of tertiary amine compounds include triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7 (DBU).

[0071] Examples of organometallic compounds 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.

[0072] When a catalyst is used in preparing the urethane prepolymer (A), the amount of the catalyst used is preferably 0.0001 to 1.0% by weight, alternatively 0.001 to 1.0% by weight, alternatively 0.003 to 1.0% by weight, or alternatively 0.005 to 1.0% by weight, based on the total amount of the polyol, the compound having a polymerizable unsaturated double bond, and the crosslinking agent.

[0073] When a catalyst is used in preparing the urethane prepolymer (A), the reaction temperature is preferably less than 100° C., and may be from 60 to 90° C. If the temperature is 100° C. or higher, it may be difficult to control the reaction rate and the crosslinked structure.

[0074] The urethane prepolymer (A) may be prepared without using a catalyst, in which case the reaction temperature may be preferably 100° C. or higher.

[0075] Methods for preparing the urethane prepolymer (A) include, for example, 1) a method in which a polyol, a compound having a polymerizable unsaturated double bond, a crosslinking agent, and a catalyst are charged into a volumetric flask, and 2) a method in which a part or all of the polyol, a part or all of the compound having a polymerizable unsaturated double bond, and a catalyst are charged into a flask, and a part or all of the crosslinking agent is added. In method 2), after a part or all of the crosslinking agent has been added, the remainder of the polyol, the remainder of the compound having a polymerizable unsaturated double bond, and the remainder of the crosslinking agent may be additionally added.

[0076] When preparing the urethane prepolymer (A), any suitable solvent can be used. Examples of such solvents include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone. Among these solvents, toluene is preferred.

[0077] When preparing the urethane prepolymer (A), any suitable other component can be used in any suitable amount as long as it does not impair the effects of the present invention. Examples of other components include antioxidants, ultraviolet 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 or two or more types. Among the other components, antioxidants, ultraviolet absorbers, and light stabilizers are preferred embodiments.

[0078] Any appropriate antioxidant may be used as long as it does not impair the effects of the present invention. Examples of such antioxidants include radical chain inhibitors and peroxide decomposers. Examples of radical chain inhibitors include phenolic antioxidants and amine antioxidants. Examples of peroxide decomposers include sulfur-based antioxidants and phosphorus-based antioxidants.

[0079] Any suitable ultraviolet absorber may be used as long as it does not impair the effects of the present invention. Examples of such ultraviolet absorbers 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.

[0080] Any appropriate light stabilizer can be used as long as it does not impair the effects of the present invention. Examples of such light stabilizers include hindered amine light stabilizers and ultraviolet stabilizers.

[0081] <A-2-2. Crosslinking agent (B)> The urethane prepolymer (A) typically reacts with the crosslinking agent (B) to form a urethane resin. The crosslinking agent (B) may be one type or two or more types.

[0082] As the crosslinking agent (B), any appropriate crosslinking agent can be used as long as it is usable for producing a urethane resin and does not impair the effects of the present invention. Such a crosslinking agent is preferably a polyfunctional isocyanate compound. The polyfunctional isocyanate compound may be used alone or in combination of two or more types.

[0083] As the polyfunctional isocyanate compound, any appropriate polyfunctional isocyanate compound that can be used in a urethanization reaction can be used. For example, the polyfunctional isocyanate compounds described above as polyfunctional isocyanate compounds that can be reacted with a polyol to obtain the urethane prepolymer (A) can be used. The polyfunctional isocyanate compound that reacts with the urethane prepolymer (A) to form a urethane resin may be the same as or different from the polyfunctional isocyanate compound described above as polyfunctional isocyanate compounds that can be reacted with a polyol to obtain the urethane prepolymer (A).

[0084] The equivalent ratio of the NCO groups of the polyfunctional isocyanate compound to the OH groups of the urethane prepolymer (A), expressed as NCO groups / OH groups, is preferably 0.2 to 1.8, and may be 0.2 to 1.6, 0.3 to 1.4, 0.3 to 1.2, 0.4 to 1.1, 0.4 to 1.0, 0.4 to 0.9, 0.4 to 0.8, or 0.5 to 0.8. When the equivalent ratio of NCO groups / OH groups is within the above range, the effects of the present invention can be more effectively exhibited.

[0085] The content of the crosslinking agent (B) in the pressure-sensitive adhesive composition can be any appropriate amount as long as it does not impair the effects of the present invention. The content of such crosslinking agent (B) is preferably 0.4 to 13 parts by weight, alternatively 0.5 to 11 parts by weight, 0.6 to 9.0 parts by weight, 0.7 to 7.0 parts by weight, 0.8 to 5.0 parts by weight, or 0.9 to 3.0 parts by weight, relative to 100 parts by weight of the urethane prepolymer (A). When the content of the crosslinking agent (B) relative to 100 parts by weight of the urethane prepolymer (A) is within the above range, the effects of the present invention can be more effectively exhibited.

[0086] <A-2-3. Urethane (meth)acrylate (C)> The pressure-sensitive adhesive composition contains a urethane (meth)acrylate (C). The urethane (meth)acrylate (C) may be of one type, or may be of two or more types.

[0087] The content of the urethane (meth)acrylate (C) in the pressure-sensitive adhesive composition is preferably 1 to 70 parts by weight, alternatively 5 to 60 parts by weight, alternatively 10 to 50 parts by weight, or alternatively 15 to 45 parts by weight, relative to 100 parts by weight of the urethane prepolymer (A).

[0088] The number of functional groups of the urethane (meth)acrylate (C) is preferably 2 or more, more preferably 3 or more, from the viewpoint of further exhibiting the effects of the present invention, and may be 3 to 20, 4 to 10, 4 to 8, or even 6. In the surface protection film according to an embodiment of the present invention, if the number of functional groups of the urethane (meth)acrylate (C) is within the above-mentioned preferred range, the anchoring strength of the pressure-sensitive adhesive layer (anchoring strength at the interface between the pressure-sensitive adhesive layer and the base layer) can be satisfactorily exhibited, particularly even if the adhesive strength after UV irradiation becomes very low.

[0089] The urethane (meth)acrylate (C) preferably has a structure represented by the following general formula (1) in order to further exhibit the effects of the present invention. When the urethane (meth)acrylate (C) has a structure represented by the following general formula (1), the surface protection film according to an embodiment of the present invention can exhibit good anchoring strength of the pressure-sensitive adhesive layer (anchoring strength at the interface between the pressure-sensitive adhesive layer and the base layer), particularly even if the adhesive strength after UV irradiation becomes very low. Furthermore, when the urethane (meth)acrylate (C) has a structure represented by the following general formula (1), the surface protection film according to an embodiment of the present invention can exhibit better cuttability during processing.

[0090] The urethane (meth)acrylate (C) preferably has a structure represented by the following general formula (1a), in order to further exhibit the effects of the present invention. When the urethane (meth)acrylate (C) has a structure represented by the following general formula (1a), the surface protection film according to an embodiment of the present invention can exhibit good anchoring strength of the pressure-sensitive adhesive layer (anchoring strength at the interface between the pressure-sensitive adhesive layer and the base layer), particularly even if the adhesive strength after UV irradiation becomes very low. Furthermore, when the urethane (meth)acrylate (C) has a structure represented by the following general formula (1a), the surface protection film according to an embodiment of the present invention can exhibit better cuttability during processing.

[0091] The urethane (meth)acrylate (C) preferably has a structure represented by the following general formula (2), in order to further exhibit the effects of the present invention. When the urethane (meth)acrylate (C) has a structure represented by the following general formula (2), the surface protection film according to an embodiment of the present invention can exhibit good anchoring strength of the pressure-sensitive adhesive layer (anchoring strength at the interface between the pressure-sensitive adhesive layer and the base layer), particularly even if the adhesive strength after UV irradiation becomes very low.

[0092] In general formula (2), X is a divalent aromatic group or a divalent aliphatic group.

[0093] As the divalent aromatic group, any appropriate divalent aromatic group can be adopted as long as it does not impair the effects of the present invention. Examples of the divalent aromatic group include a benzene-1,4-diyl group, a benzene-1,3-diyl group, a benzene-1,2-diyl group, a toluene-2,4-diyl group, a toluene-2,5-diyl group, a toluene-2,6-diyl group, a 4,6-dimethylbenzene-1,3-diyl group, a 2,5-dimethylbenzene-1,4-diyl group, a 2,6-dimethylbenzene-1,4-diyl group, a 2,4,6-trimethylbenzene-1,3-diyl group, and a 2, Examples thereof include 3,5,6-tetramethylbenzene-1,4-diyl group, m-xylylene-diyl group, p-xylylene-diyl group, naphthalene-1,2-diyl group, naphthalene-1,3-diyl group, naphthalene-1,4-diyl group, naphthalene-1,5-diyl group, naphthalene-1,6-diyl group, naphthalene-1,7-diyl group, naphthalene-1,8-diyl group, naphthalene-2,3-diyl group, and naphthalene-2,6-diyl group.

[0094] As the divalent aliphatic group, any appropriate divalent aliphatic group can be adopted as long as the effects of the present invention are not impaired. Examples of the divalent aliphatic group include a divalent chain aliphatic group and a divalent cyclic structure-containing aliphatic group.

[0095] The divalent chain aliphatic group may be linear or branched. Examples of the divalent chain aliphatic group include a methylene group, an ethane-1,1-diyl group, an ethane-1,2-diyl group, a propane-1,1-diyl group, a propane-1,3-diyl group, a propane-2,2-diyl group, a pentane-1,5-diyl group, and a hexane-1,6-diyl group.

[0096] Examples of the divalent cyclic structure-containing aliphatic group include divalent aliphatic groups having a cycloalkane ring structure (e.g., a cyclohexyl ring structure). Examples of the divalent cyclic structure-containing aliphatic group include groups represented by the following general formula (3). Note that the two bonds marked with * in general formula (3) are bonds that function as a divalent group.

[0097] In order to further enhance the effects of the present invention, the urethane (meth)acrylate (C) preferably has a molecular weight of less than 1000. If the molecular weight of the urethane (meth)acrylate (C) is 1000 or more, the effects of the present invention may not be exhibited.

[0098] Examples of the urethane (meth)acrylate (C) include compounds having a structure represented by the following general formula (4).

[0099] In the general formula (4), X is as defined above.

[0100] <A-2-4. Photopolymerization initiator (D)> The pressure-sensitive adhesive composition contains a photopolymerization initiator (D). The photopolymerization initiator (D) may be used alone or in combination of two or more types.

[0101] Any appropriate photopolymerization initiator can be used as the photopolymerization initiator (D) as long as it does not impair the effects of the present invention. Examples of such photopolymerization initiator (D) include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators.

[0102] Examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, and anisole methyl ether. Examples of acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzyl-based photopolymerization initiators include benzil. Examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexyl phenyl ketone. Examples of ketal-based photopolymerization initiators include benzil dimethyl ketal. Examples of thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

[0103] The content of the photopolymerization initiator (D) in the pressure-sensitive adhesive composition may be any appropriate amount as long as the effects of the present invention are not impaired. The content of such photopolymerization initiator (D) is preferably 0.001 to 20 parts by weight, may be 0.01 to 10 parts by weight, or may be 0.1 to 5 parts by weight, relative to 100 parts by weight of the urethane prepolymer (A).

[0104] <A-2-5. Other Components> The pressure-sensitive adhesive composition may contain any appropriate other components as long as they do not impair the effects of the present invention. Examples of such other components include solvents, catalysts, 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.

[0105] <A-3. Base Material Layer> The base material layer may be a single layer or may be two or more layers. The base material layer may be a stretched layer.

[0106] The thickness of the substrate layer is preferably 4 μm to 450 μm, and may be 8 μm to 400 μm, 12 μm to 350 μm, or 16 μm to 250 μm.

[0107] For the surface of the base layer 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 base layer, 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 is easy to unwind.

[0108] An antistatic layer may be provided on the side of the substrate layer on which the pressure-sensitive adhesive layer is not provided. Any appropriate antistatic layer may be used as the antistatic layer as long as the effects of the present invention are not impaired. Such an antistatic layer may contain, for example, an antistatic agent. Any appropriate antistatic agent may be used as the antistatic agent as long as the effects of the present invention are not impaired. Examples of such antistatic agents include conductive polymers, carbon nanotubes, ionic compounds, carbon, surfactants, alkali metal salts, metal oxides, and metal fine particles.

[0109] Any appropriate material may be used as the material for the substrate layer depending on the application. Examples include plastic, paper, metal film, nonwoven fabric, etc. Plastic is preferred. That is, the substrate layer is preferably a plastic film. The substrate layer may be made of one material or two or more materials. For example, it may be made of two or more plastics.

[0110] 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.

[0111] The substrate layer may contain any appropriate additives as needed. Examples of additives that may be contained in the substrate layer 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 layer may be appropriately set depending on the purpose. In particular, when the material of the substrate layer is 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.

[0112] <<B. Uses>> The surface protection film according to an embodiment of the present invention is typically attached to the exposed surface of an optical or electronic component to prevent the surface of the optical or electronic component from being scratched during processing, assembly, inspection, transportation, etc. in the manufacturing process of an optical or electronic device, and can be suitably used for surface protection of the optical or electronic component. The optical device according to an embodiment of the present invention includes an adhesive film according to an embodiment of the present invention. The electronic device according to an embodiment of the present invention includes an adhesive film according to an embodiment of the present invention.

[0113] 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.

[0114] <Initial Adhesion Strength to Glass Plate Before UV Irradiation> The surface protection film (25 mm wide x 140 mm long) from which the release liner had been removed was adhered to a glass plate (soda lime glass, manufactured by Matsunami Glass Industry Co., Ltd.) using a 2 kg hand roller in one stroke. The film was then left for 30 minutes in an environment of 23°C and 55% RH to obtain an evaluation sample. The obtained evaluation sample was measured using a tensile tester in an environment of 23°C and 55% RH. The tensile tester used was an "Autograph AG-Xplus HS 6000 mm / min High-Speed ​​Model (AG-50NX plus)" manufactured by Shimadzu Corporation. After the evaluation sample was placed in the tensile tester, the tensile test was initiated. The tensile test conditions were a peel angle of 180° and a peel speed (pulling speed) of 300 mm / min. The load when peeling the surface protective film from the glass plate was measured, and the average load was taken as the initial adhesive strength of the surface protective film to the glass plate before UV irradiation.

[0115] <Initial Adhesion Strength to Glass Plate After UV Irradiation> A surface protection film (25 mm wide x 140 mm long) from which the release liner had been removed was attached to a glass plate (soda lime glass, manufactured by Matsunami Glass Industry Co., Ltd.) using a 2 kg hand roller in one stroke. Thereafter, the surface protection film was irradiated with an LED light source having a wavelength of 365 nm at an integrated light intensity of 700 mJ / cm. 2 The adhesive layer was photocured by irradiating it with ultraviolet light, and then left for 30 minutes in an environment of 23°C and 55% RH to obtain an evaluation sample. The obtained evaluation sample was measured using a tensile tester in an environment of 23°C and 55% RH. The tensile tester used was an "Autograph AG-Xplus HS 6000 mm / min High-Speed ​​Model (AG-50NX plus)" manufactured by Shimadzu Corporation. After the evaluation sample was set in the tensile tester, the tensile test was started. The tensile test conditions were a peel angle of 180 degrees and a peel rate (pulling rate) of 300 mm / min. The load when peeling the surface protective film from the glass plate was measured, and the average load at that time was defined as the initial adhesive strength of the surface protective film to the glass plate after UV irradiation.

[0116] <Cuttability during processing> A surface protection film (width 25 mm × length 140 mm) from which the release liner had been peeled was cut 1 cm into the center of the adhesive layer side with a cutter blade at a 90° angle. When adhesive residue of 1 mm or more was visually confirmed, it was rated as ×, when adhesive residue of less than 1 mm was visually confirmed, it was rated as ◯, and when no adhesive residue was confirmed, it was rated as ⊚.

[0117] <Anchoring strength after UV irradiation> The surface protection film was cut into a size of 50 mm x 50 mm. Then, an LED light source with a wavelength of 365 nm was used to irradiate the surface protection film with an integrated light intensity of 700 mJ / cm. 2 The adhesive layer was photocured by irradiating it with ultraviolet light of 1000 kJ / cm², and the adhesive layer was used as an evaluation sample. After the release liner was peeled off from the obtained evaluation sample, the adhesive side was rubbed with a finger from the edge and evaluated according to the following criteria: ◎: Did not peel off even when rubbed hard. ○: Peeled off when rubbed hard. ×: Peeled off without rubbing hard.

[0118] Production Example 1 Urethane Prepolymer A 328.5 g of polytetramethylene glycol (product name "PTMG3000" manufactured by Mitsubishi Chemical Corporation), 8.8 g of polyester polyol (product name "Kuraray Polyol P-2010" manufactured by Kuraray Co., Ltd.), 8.8 g of a compound having a polymerizable unsaturated double bond (product name "Blenmer GLM" manufactured by NOF Corporation), and 150 g of toluene (manufactured by Tosoh Corporation) as a solvent were charged into a polymerization experimental apparatus equipped with a 1 L round-bottom separable flask, a separable cover, a separatory funnel, a thermometer, a dry air inlet tube, a Liebig condenser, a vacuum seal, a stirring rod, and a stirring blade. While stirring, 0.05 g of bismuth octylate (manufactured by Nippon Chemical Industry Co., Ltd.) was charged as a catalyst, and the mixture was then purged with dry air at room temperature for 2 hours. Thereafter, 26.9 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and while inflowing dry air, the solution temperature in the experimental apparatus was controlled in a water bath to 70±2°C, and the mixture was maintained for 2 hours. Thereafter, 65.7 g of polypropylene glycol (product name "Sannyx GP-1500", manufactured by Sanyo Chemical Industries, Ltd.) was added, and the mixture was maintained for 2 hours. 12.0 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was further added, and while stirring with an inflow of dry air, the solution temperature in the experimental apparatus was controlled in a water bath to 70±2°C, and the mixture was maintained for 3 hours to obtain a solution of urethane prepolymer A. Note that during the polymerization, toluene was added dropwise as appropriate 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 300 g. The solids concentration of the urethane prepolymer A solution was 50 wt%.

[0119] [Production Example 2] Urethane Prepolymer B A polymerization experiment 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 180 g of polypropylene glycol (product name "Sanix PP-2000" manufactured by Sanyo Chemical Industries, Ltd.), 43 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 octylate (manufactured by Nippon Chemical Industry Co., Ltd.) as a catalyst, and the atmosphere was replaced with nitrogen at room temperature for 1 hour with stirring. Thereafter, under nitrogen flow and stirring, 30.5 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and the solution temperature in the experimental apparatus was maintained at 90±2°C in a water bath while maintaining the temperature for 4 hours. Thereafter, 180 g of polypropylene glycol (product name "GP-1000", manufactured by Sanyo Chemical Industries, Ltd.) was added, and the solution temperature in the experimental apparatus was maintained at 90±2°C in a water bath while maintaining the temperature for 2 hours. Thereafter, 16.5 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and the solution temperature 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 B. 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 340 g. The solids concentration of the urethane prepolymer B solution was 50 wt %.

[0120] [Example 1] 100 parts by weight of the urethane prepolymer A obtained in Production Example 1, 1.2 parts by weight of an isocyanate compound (Coronate HX:C / HX, manufactured by Nippon Polyurethane Industries, Ltd.) as a crosslinking agent, 30 parts by weight of UA-1138P (manufactured by Shin-Nakamura Chemical Co., Ltd.) as a urethane (meth)acrylate, 1.0 part by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, 1.0 part by weight of Omnirad 651 (manufactured by BASF) as a photopolymerization initiator, and 0.03 parts by weight of Envirizer OL-1 (manufactured by Tokyo Fine Chemicals Co., Ltd.) as a catalyst were diluted with ethyl acetate to a total solids content of 50% by weight, to obtain a urethane-based pressure-sensitive adhesive composition (1). The obtained urethane-based pressure-sensitive adhesive composition (1) was applied to a substrate made of polyester resin (product name "T100-75S", manufactured by Mitsubishi Chemical Corporation, thickness 75 μm) so as to have a thickness of 75 μm after drying, and then cured and dried under conditions of a drying temperature of 130°C and a drying time of 3 minutes, thereby producing a pressure-sensitive adhesive layer (1) on the substrate. Next, the silicone-treated surface of a release liner made of polyester resin with one side silicone-treated (product name "MRF25", manufactured by Mitsubishi Chemical Corporation, thickness 25 μm) was laminated to the surface of the obtained pressure-sensitive adhesive layer (1), thereby obtaining a surface protection film (1) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (1) (thickness 75 μm) / substrate. The obtained surface protection film (1) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0121] Example 2 The same procedure as in Example 1 was carried out, except that 30 parts by weight of UA-7100 (manufactured by Shin-Nakamura Chemical Co., Ltd.) was used as the urethane (meth)acrylate instead of 30 parts by weight of UA-1138P (manufactured by Shin-Nakamura Chemical Co., Ltd.), to obtain a urethane-based pressure-sensitive adhesive composition (2) and a surface protective film (2) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (2) (thickness 75 μm) / substrate. The obtained surface protective film (2) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0122] Example 3 The same procedure as in Example 1 was carried out, except that 30 parts by weight of UA-306T (Kyoeisha Chemical Co., Ltd.) was used as the urethane (meth)acrylate instead of 30 parts by weight of UA-1138P (Shin-Nakamura Chemical Co., Ltd.), to obtain a urethane-based pressure-sensitive adhesive composition (3) and a surface protective film (3) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (3) (thickness 75 μm) / substrate. The obtained surface protective film (3) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0123] Example 4 The same procedure as in Example 1 was carried out, except that 30 parts by weight of UA-1100H (manufactured by Shin-Nakamura Chemical Co., Ltd.) was used as the urethane (meth)acrylate instead of 30 parts by weight of UA-1138P (manufactured by Shin-Nakamura Chemical Co., Ltd.), to obtain a urethane-based pressure-sensitive adhesive composition (4) and a surface protective film (4) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (4) (thickness 75 μm) / substrate. The obtained surface protective film (4) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0124] Example 5 The same procedure as in Example 1 was carried out, except that 30 parts by weight of U-6LPA (manufactured by Shin-Nakamura Chemical Co., Ltd.) was used as the urethane (meth)acrylate instead of 30 parts by weight of UA-1138P (manufactured by Shin-Nakamura Chemical Co., Ltd.), to obtain a urethane-based pressure-sensitive adhesive composition (5) and a surface protective film (5) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (5) (thickness 75 μm) / substrate. The obtained surface protective film (5) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0125] Comparative Example 1 The same procedure as in Example 1 was carried out, except that urethane (meth)acrylate was not used, to obtain a urethane-based pressure-sensitive adhesive composition (C1) and a surface protective film (C1) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C1) (thickness 75 μm) / substrate. The obtained surface protective film (C1) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0126] Comparative Example 2 The same procedure as in Example 1 was carried out, except that 30 parts by weight of trimethylolpropane triacrylate (trade name "A-TMPT", manufactured by Shin-Nakamura Chemical Co., Ltd.) was used as the (meth)acrylate instead of the urethane (meth)acrylate, to obtain a urethane-based pressure-sensitive adhesive composition (C2) and a surface protective film (C2) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C2) (thickness 75 μm) / substrate. The obtained surface protective film (C2) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0127] Comparative Example 3 The same procedure as in Example 1 was carried out, except that 30 parts by weight of dipentaerythritol polyacrylate (trade name "A-DPH", manufactured by Shin-Nakamura Chemical Co., Ltd.) was used as the (meth)acrylate instead of the urethane (meth)acrylate, to obtain a urethane-based pressure-sensitive adhesive composition (C3) and a surface protective film (C3) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C3) (thickness 75 μm) / substrate. The obtained surface protective film (C3) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0128] Comparative Example 4 The same procedure as in Example 4 was carried out, except that 100 parts by weight of the urethane prepolymer B obtained in Production Example 2 was used instead of 100 parts by weight of the urethane prepolymer A obtained in Production Example 1, to obtain a urethane-based pressure-sensitive adhesive composition (C4) and a surface protective film (C4) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C4) (thickness 75 μm) / substrate. The obtained surface protective film (C4) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0129] Comparative Example 5 The same procedure as in Comparative Example 2 was carried out, except that 100 parts by weight of the urethane prepolymer B obtained in Production Example 2 was used instead of 100 parts by weight of the urethane prepolymer A obtained in Production Example 1, to obtain a urethane-based pressure-sensitive adhesive composition (C5) and a surface protective film (C5) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C5) (thickness 75 μm) / substrate. The obtained surface protective film (C5) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0130] Comparative Example 6 The same procedure as in Comparative Example 3 was carried out, except that 100 parts by weight of the urethane prepolymer B obtained in Production Example 2 was used instead of 100 parts by weight of the urethane prepolymer A obtained in Production Example 1, to obtain a urethane-based pressure-sensitive adhesive composition (C6) and a surface protective film (C6) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C6) (thickness 75 μm) / substrate. The obtained surface protective film (C6) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0131]

[0132] The surface protective film of the present invention can be used for any suitable application, and is preferably used in the fields of optical devices and electronic devices.

[0133] 1 Base layer 2 Pressure-sensitive adhesive layer 10 Surface protection film

Claims

1. A surface protection film comprising an adhesive layer, wherein the adhesive constituting the adhesive layer is formed from an adhesive composition, the adhesive composition contains a urethane prepolymer (A), a crosslinking agent (B), a urethane (meth)acrylate (C), and a photopolymerization initiator (D), and the urethane prepolymer (A) has a polymerizable unsaturated double bond, the surface protection film.

2. The surface protection film according to claim 1, wherein the functional group number of the urethane (meth)acrylate (C) is 3 or more.

3. The surface protection film according to claim 1, wherein the urethane (meth) acrylate (C) has a structure represented by the following general formula (1).

4. The surface protection film according to claim 1, wherein the urethane (meth) acrylate (C) has a structure represented by the following general formula (2). However, in the general formula (2), X is a divalent aromatic group or a divalent aliphatic group.

5. The surface protection film according to claim 1, wherein the molecular weight of the urethane (meth)acrylate (C) is less than 1000.

6. After laminating the adhesive layer contained in the surface protection film onto the surface of a glass plate and leaving it for 30 minutes in an environment of a temperature of 23°C and a humidity of 55% RH, in an environment of a temperature of 23°C and a humidity of 55% RH, when the surface protection film is peeled from the surface of the glass plate at a peeling angle of 180 degrees and a peeling speed of 300 mm / min, the adhesive force is 500 gf / 25 mm or more, the surface protection film according to claim 1.

7. The adhesive layer contained in the surface protection film is bonded to the surface of the glass plate, and ultraviolet rays with an integrated light quantity of 700 mJ / cm 2 are irradiated by an LED light source with a wavelength of 365 nm. After leaving it for 30 minutes in an environment of a temperature of 23°C and a humidity of 55% RH, in an environment of a temperature of 23°C and a humidity of 55% RH, when the surface protection film is peeled off from the surface of the glass plate at a peeling angle of 180 degrees and a peeling speed of 300 mm / min, the adhesive force is 20.00 gf / 25 mm or less. The surface protection film according to claim 1.

8. An optical device comprising the surface protection film according to any one of claims 1 to 7.

9. An electronic device comprising the surface protection film according to any one of claims 1 to 7.