Surface protective film

Abstract

Provided is a surface protective film including an adhesive layer. The surface protective film exhibits sufficiently strong adhesiveness to an adherend before ultraviolet irradiation, and once being subjected to ultraviolet irradiation, demonstrates excellent effortless peelability, allowing easy separation from the adherend. Furthermore, the surface protective film has superior storage stability.　A surface protective film according to an embodiment of the present invention includes an adhesive layer. An adhesive constituting the adhesive layer is formed from an adhesive composition. The adhesive composition contains a urethane prepolymer (A), a crosslinking agent (B), a photopolymerization initiator (C), and an antioxidant (D). The urethane prepolymer (A) includes: an alkylene oxide skeleton including two groups, each of which being at least one type selected from the group consisting of a methylene group and a methine group; and an alkylene oxide skeleton including three or more groups, each of which being at least one type selected from the group consisting of a methylene group and a methine group.

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 are required to exhibit sufficiently strong adhesive strength so as not to peel off easily while surface protection is required. On the other hand, once surface protection is no longer required, excellent easy releasability is required so that the surface protection film can be smoothly peeled off from the optical or electronic component without causing contamination or damage. In other words, a combination of sufficiently strong adhesive strength while surface protection is required and excellent easy releasability once surface protection is no longer required is required.

[0004] As a technology for adjusting adhesive strength, a surface protection sheet for optical components whose adhesive strength is reduced by irradiation with ultraviolet light has been reported (Patent Document 2). Also, a surface protection sheet for optical components whose adhesive strength is reduced by irradiation with ultraviolet light, thereby exhibiting easy releasability, has been reported (Patent Document 3). However, the adhesive reported in Patent Document 2 does not have a sufficiently high adhesive strength before ultraviolet light irradiation, nor does it have a sufficiently low adhesive strength after ultraviolet light irradiation. Furthermore, the adhesive reported in Patent Document 3 does not have a sufficiently low adhesive strength. Therefore, it is not possible to achieve both sufficiently strong adhesive strength while surface protection is necessary and excellent easy releasability when surface protection is no longer necessary.

[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 4). However, the pressure-sensitive adhesive reported in Patent Document 4 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 5). However, the pressure-sensitive adhesive reported in Patent Document 5 also has the problem that its adhesive strength before UV irradiation is low and it is prone to peeling while surface protection is required.

[0007] Furthermore, the conventional adhesives mentioned above have the problem that their adhesive performance deteriorates during storage.

[0008] Japanese Patent No. 6613516 Japanese Patent Application Laid-Open No. 2019-116609 Japanese Patent Application Laid-Open No. 2019-116610 Japanese Patent No. 6769503 Japanese Patent No. 7285072

[0009] An object of the present invention is to provide a surface protection film including a pressure-sensitive adhesive layer, which is primarily used for attachment to exposed surfaces of optical or electronic components to prevent scratches on the surfaces during processing, assembly, inspection, transportation, etc. in the manufacturing process of optical or electronic devices, and which exhibits sufficiently strong adhesion to an adherend before ultraviolet irradiation, exhibits excellent easy releasability allowing smooth release from the adherend after ultraviolet irradiation, and further exhibits excellent storage stability.Another object of the present invention is to provide an optical device or electronic device including such a surface protection film.

[0010] [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 photopolymerization initiator (C), and an antioxidant (D), wherein the urethane prepolymer (A) includes an alkylene oxide skeleton including two groups of at least one type selected from the group consisting of methylene groups and methine groups, and an alkylene oxide skeleton including three or more groups of at least one type selected from the group consisting of methylene groups and methine groups. [2] In the surface protection film according to the above [1], the amount of the antioxidant (D) per 100 parts by weight of the urethane prepolymer (A) may be 0.10 parts by weight or more. [3] In the surface protective film according to the above [1] or [2], the ratio of the amount of the antioxidant (D) to the amount of the photopolymerization initiator (C) (antioxidant (D) / photopolymerization initiator (C)) may be 0.25 or more by weight. [4] In the surface protective film according to any one of the above [1] to [3], the ratio of the amount of the antioxidant (D) to the amount of the photopolymerization initiator (C) (antioxidant (D) / photopolymerization initiator (C)) may be less than 3.00 by weight. [5] In the surface protective film according to any one of the above [1] to [4], the amount of the photopolymerization initiator (C) may exceed 0.1 parts by weight per 100 parts by weight of the urethane prepolymer (A). [6] In the surface protective film according to any one of the above [1] to [5], the pressure-sensitive adhesive composition may contain urethane (meth)acrylate. [7] An optical device according to an embodiment of the present invention includes the surface protection film according to any one of the above items [1] to [6]. [8] An electronic device according to an embodiment of the present invention includes the surface protection film according to any one of the above items [1] to [6].

[0011] According to the present invention, there is provided 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 attach to exposed surfaces of optical or electronic components to prevent the surfaces from being scratched during processing, assembly, inspection, transportation, etc., and which exhibits sufficiently strong adhesion to an adherend before ultraviolet irradiation, exhibits excellent easy releasability that allows smooth release from the adherend after ultraviolet irradiation, and further exhibits excellent storage stability. Furthermore, there can be provided optical devices and electronic devices including such a surface protection film.

[0012] 1 is a schematic cross-sectional view of a surface protection film according to one embodiment of the present invention.

[0013] When the expression "weight" appears in this specification, it may be read as "mass," which is commonly used as an SI unit indicating weight.

[0014] 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".

[0015] 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.

[0016] 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.

[0017] 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).

[0018] 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.

[0019] 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.

[0020] The surface protection film according to the embodiment of the present invention has an adhesive strength (hereinafter sometimes referred to as "initial adhesive strength to glass plate before UV irradiation") when an adhesive layer contained in the surface protection film is attached to the surface of a glass plate, 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 adhesive strength is preferably 100 gf / 25 mm or more, 300 gf / 25 mm or more, 500 gf / 25 mm or more, 1000 gf / 25 mm or more, 1300 gf / 25 mm or more, 1500 gf / 25 mm or more, 1800 gf / 25 mm or more, or 2000 gf / 25 mm or more. The higher the initial adhesive strength before UV irradiation to the glass plate, the better, but if it is too high, there is a risk that sufficient easy peelability will not be exhibited even when irradiated with ultraviolet rays. Therefore, the upper limit value is preferably, for example, 5000 gf / 25 mm or less, and may be 4000 gf / 25 mm or less, or may be 3500 gf / 25 mm or less. If the initial adhesive strength before UV irradiation to the glass plate is within the above range, the surface protective film according to the embodiment of the present invention can exhibit, for example, sufficiently strong adhesive strength to the adherend. If the initial adhesive strength before UV irradiation to the glass plate is too low outside the above range, there is a risk that the surface protective film will peel off from the adherend while surface protection is required. Note that details of the method for measuring the initial adhesive strength before UV irradiation to the glass plate will be described later.

[0021] 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. 2and then leaving it in an environment of a temperature of 23°C and a humidity of 55% RH for 30 minutes, and then peeling the surface protective film from the surface of the glass plate at a peel angle of 180° 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 (hereinafter sometimes referred to as "initial adhesive strength to glass plate after UV irradiation") when peeled off is preferably 20.00 gf / 25 mm or less, optionally 16.00 gf / 25 mm or less, optionally 12.00 gf / 25 mm or less, optionally 10.00 gf / 25 mm or less, optionally 8.00 gf / 25 mm or less, optionally 7.00 gf / 25 mm or less, optionally 6.00 gf / 25 mm or less, optionally 5.50 gf / 25 mm or less, or optionally 5.00 gf / 25 mm or less. The lower the initial adhesive strength after UV irradiation to the glass plate, the better; however, if it is too low, there is a risk of spontaneous peeling from the adherend in unintended circumstances. Therefore, the lower limit is preferably, for example, 1.00 gf / 25 mm or more, and may be 1.50 gf / 25 mm or more. If the initial adhesive strength after UV irradiation to the 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, for example, when it is necessary to peel it off. If the initial adhesive strength after UV irradiation to the 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. Details of the method for measuring the initial adhesive strength after UV irradiation to the glass plate will be described later.

[0022] In the surface protective film according to an embodiment of the present invention, the change ratio of the initial adhesive strength to the glass plate before UV irradiation relative to the initial adhesive strength to the glass plate after UV irradiation (initial adhesive strength to the glass plate before UV irradiation / initial adhesive strength to the glass plate after UV irradiation) (sometimes referred to as the "change ratio of the initial adhesive strength to the glass plate before UV irradiation / after UV irradiation") is preferably 5 times or more, may be 10 times or more, 100 times or more, 200 times or more, 300 times or more, or may be 400 times or more. The higher the change ratio, the better, but considering ease of handling, etc., the upper limit is preferably 10,000 times or less, and may be 5,000 times or less, 2,000 times or less, 1,500 times or less, or 1,000 times or less. If the change ratio is within the above range, for example, the effects of the present invention can be more effectively exhibited, a sufficiently strong adhesive force to the adherend can be exhibited, and when it is necessary to peel the adhesive from the adherend, superior easy peelability can be exhibited, allowing for smoother peeling from the adherend.

[0023] The surface protection film according to an embodiment of the present invention is produced and then stored under fluorescent light in an environment of a temperature of 23°C and a humidity of 55% RH for one day. Then, the pressure-sensitive adhesive layer contained in the surface protection film is attached to the surface of a glass plate, and the film is left for 30 minutes in an environment of a temperature of 23°C and a humidity of 55% RH. After that, the surface protection film is peeled from the glass plate surface 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 (hereinafter, " This is sometimes referred to as "initial adhesive strength to glass plate before UV irradiation after one day of storage under fluorescent lamp." The initial adhesive strength is preferably 100 gf / 25 mm or more, and may be 300 gf / 25 mm or more, 500 gf / 25 mm or more, 1000 gf / 25 mm or more, 1300 gf / 25 mm or more, 1500 gf / 25 mm or more, 1800 gf / 25 mm or more, or 2000 gf / 25 mm or more. The higher the initial adhesive strength to glass plate before UV irradiation, the better, but if it is too high, there is a risk that sufficient easy peelability will not be exhibited even when irradiated with ultraviolet rays. For this reason, the upper limit is preferably 5000 gf / 25 mm or less, and may be 4000 gf / 25 mm or less, or 3500 gf / 25 mm or less. If the initial adhesive strength to a glass plate before UV irradiation after storage under fluorescent light for one day is within the above range, the surface protective film according to an embodiment of the present invention has, for example, excellent storage stability. Details of the method for measuring the initial adhesive strength to a glass plate before UV irradiation after storage under fluorescent light for one day will be described later.

[0024] In the surface protective film according to an embodiment of the present invention, the rate of change from the initial adhesive strength to the glass plate before UV irradiation after storage for 1 day under fluorescent lamp ((initial adhesive strength to glass plate before UV irradiation / initial adhesive strength to glass plate before UV irradiation after storage for 1 day under fluorescent lamp) × 100(%)) (sometimes referred to as the "rate of change in initial adhesive strength to glass plate before UV irradiation before storage / after storage") is preferably 1000% or less, or may be 500% or less, 200% or less, 150% or less, 130% or less, 120% or less, or 110% or less. The lower limit of the rate of change in initial adhesive strength to glass plate before UV irradiation before storage / after storage is, for example, 80% or more, 90% or more, 95% or more, or 100% or more. When the rate of change is within the above range, the surface protective film according to an embodiment of the present invention has excellent storage stability, for example.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The above heating and drying conditions can be appropriately selected from methods commonly known for forming a pressure-sensitive adhesive layer.

[0029] <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.

[0030] 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.

[0031] 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.

[0032] <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.

[0033] 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.

[0034] The pressure-sensitive adhesive composition contains a urethane prepolymer (A), a crosslinking agent (B), a photopolymerization initiator (C), and an antioxidant (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 photopolymerization initiator (C), and the antioxidant (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.

[0035] <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.

[0036] The urethane prepolymer (A) may be used alone or in combination of two or more kinds.

[0037] The content of the urethane prepolymer (A) in the PSA composition is preferably 50% by weight to 99.9% by weight, or alternatively 55% by weight to 97% by weight, or alternatively 60% by weight to 95% by weight, in terms of solid content. When the content of the urethane prepolymer (A) in the PSA composition is within the above range in terms of solid content, the effects of the present invention can be more effectively exhibited.

[0038] 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.

[0039] 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 corresponds 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 a polyfunctional isocyanate in the "one-shot method."

[0040] The number average molecular weight Mn of the urethane prepolymer (A) is preferably 3,000 to 1,000,000.

[0041] In terms of being able to exert the effects of the present invention, the urethane prepolymer (A) preferably contains an alkylene oxide skeleton containing two of at least one group selected from the group consisting of methylene groups and methine groups, and an alkylene oxide skeleton containing three or more of at least one group selected from the group consisting of methylene groups (-CH-) and methine groups (-CH(CH)-). By employing a urethane prepolymer (A) having such a specific alkylene oxide skeleton as the urethane prepolymer (A), the effects of the present invention can be exerted, such as being able to exert sufficiently strong adhesive strength to an adherend before UV irradiation and exhibiting excellent easy releasability that allows smooth releasability from the adherend after UV irradiation.

[0042] The urethane prepolymer (A) may have 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 commonly known polymerizable unsaturated double bonds, such as vinyl groups, (meth)allyl groups, and (meth)acryloyl groups. The (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.

[0043] When the urethane prepolymer (A) has a polymerizable unsaturated double bond, the content of the polymerizable unsaturated double bond in the urethane prepolymer (A) is preferably 0.10 mol / kg to 0.50 mol / kg, or may be 0.15 mol / kg to 0.45 mol / kg, 0.20 mol / kg to 0.40 mol / kg, or 0.25 mol / kg to 0.35 mol / kg. When the content of the polymerizable unsaturated double bond in the urethane prepolymer (A) is within the above range, the effects of the present invention can be more effectively exhibited. If the content of the polymerizable unsaturated double bond in the urethane prepolymer (A) is too low outside the above range, it may be impossible to exhibit sufficiently strong adhesive strength to the adherend, and for example, the initial adhesive strength to a glass plate before UV irradiation may be low. If the content of polymerizable unsaturated double bonds in the urethane prepolymer (A) is too high and deviates from the above range, there is a risk that the tearing force may be too high in a tearing step, which may be carried out, for example, in the manufacturing process of optical devices or electronic devices, in which a portion of a surface protective film attached to an adherend is torn off to expose a portion of the adherend.

[0044] The hydroxyl value of the urethane prepolymer (A) is preferably 2.0 KOHmg / g to 11.0 KOHmg / g, or may be 4.0 KOHmg / g to 9.0 KOHmg / g, 5.0 KOHmg / g to 8.0 KOHmg / g, or 6.2 KOHmg / g to 7.0 KOHmg / g, in terms of being able to more effectively exhibit the effects of the present invention.

[0045] The urethane prepolymer (A) is preferably a polyurethane polyol.

[0046] 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.

[0047] In the description of the embodiments of the present invention, the term "polyol" refers to a polyol that does not contain a polymerizable unsaturated double bond. Therefore, in the description of the embodiments of the present invention, a compound having a polymerizable unsaturated double bond and a plurality of hydroxyl groups is considered to be a "compound having a polymerizable unsaturated double bond" rather than a "polyol."

[0048] The polyol preferably includes at least one selected from the group consisting of polyester polyols (a1) and polyether polyols (a2).

[0049] The polyester polyol (a1) may be used alone or in combination of two or more kinds.

[0050] The polyether polyol (a2) may be used alone or in combination of two or more kinds.

[0051] 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 55% by weight to 95% by weight, or alternatively 60% by weight to 90% by weight, calculated as solid content.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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 (sometimes referred to as polytetramethylene ether 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.

[0056] 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.

[0057] 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.

[0058] One embodiment of the polyol is embodiment (A) which includes both a polyester polyol (a1) and a polyether polyol (a2).

[0059] In embodiment (A), the polyether polyol (a2) is typically a polyether polyol containing two or more of at least one type of group selected from the group consisting of methylene groups and methine groups, and may be, for example, one or more polyether polyols (a2-1) containing two of at least one type of group selected from the group consisting of methylene groups and methine groups, or one or more polyether polyols (a2-2) containing three or more of at least one type of group selected from the group consisting of methylene groups and methine groups, or a mixture of one or more polyether polyols (a2-1) and one or more polyether polyols (a2-2).

[0060] In embodiment (A), when the polyether polyol (a2) is a mixture of one or more polyether polyols (a2-1) and one or more polyether polyols (a2-2), the weight ratio of the polyether polyol (a2-2) to 100 parts by weight of the polyether polyol (a2-1) is preferably 1 to 10,000 parts by weight, alternatively 5 to 1,000 parts by weight, 8 to 150 parts by weight, or 10 to 100 parts by weight, in terms of being able to further exhibit the effects of the present invention.

[0061] Examples of the polyether polyol (a2-1) containing two groups of at least one kind selected from the group consisting of a methylene group and a methine group include polyethylene glycol and polypropylene glycol.

[0062] An example of the polyether polyol (a2-2) containing three or more groups of at least one kind selected from the group consisting of methylene groups and methine groups is polytetramethylene glycol.

[0063] In embodiment (A), when the polyether polyol (a2) is one or more polyether polyols (a2-1), the urethane prepolymer (A) typically contains an alkylene oxide skeleton containing two of at least one group selected from the group consisting of a methylene group and a methine group.

[0064] In embodiment (A), when the polyether polyol (a2) is one or more polyether polyols (a2-2), the urethane prepolymer (A) typically contains an alkylene oxide skeleton containing three or more groups of at least one type selected from the group consisting of methylene groups and methine groups.

[0065] In embodiment (A), when the polyether polyol (a2) is a mixture of one or more polyether polyols (a2-1) and one or more polyether polyols (a2-2), the urethane prepolymer (A) typically contains an alkylene oxide skeleton containing two of at least one type of group selected from the group consisting of methylene groups and methine groups, and an alkylene oxide skeleton containing three or more of at least one type of group selected from the group consisting of methylene groups and methine groups.

[0066] 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 1% by weight to 80% by weight, 5% by weight to 60% by weight, 10% by weight to 55% by weight, 20% by weight to 50% by weight, or 25% by weight to 45% by weight.

[0067] In embodiment (A), the content of polyether polyol (a2) in the polyol is preferably 0.1% by weight to 99.9% by weight, and may be 20% by weight to 99% by weight, 40% by weight to 95% by weight, 45% by weight to 90% by weight, 50% by weight to 80% by weight, or 55% by weight to 75% by weight.

[0068] 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).

[0069] 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.

[0070] In embodiment (B), the polyether polyol (a2) is typically a polyether polyol containing two or more of at least one type of group selected from the group consisting of methylene groups and methine groups, and may be, for example, one or more polyether polyols (a2-1) containing two of at least one type of group selected from the group consisting of methylene groups and methine groups, or one or more polyether polyols (a2-2) containing three or more of at least one type of group selected from the group consisting of methylene groups and methine groups, or a mixture of one or more polyether polyols (a2-1) and one or more polyether polyols (a2-2).

[0071] Examples of the polyether polyol (a2-1) containing two groups of at least one kind selected from the group consisting of a methylene group and a methine group include polyethylene glycol and polypropylene glycol.

[0072] An example of the polyether polyol (a2-2) containing three or more groups of at least one kind selected from the group consisting of methylene groups and methine groups is polytetramethylene glycol.

[0073] In embodiment (B), when the polyether polyol (a2) is one or more polyether polyols (a2-1), the urethane prepolymer (A) typically contains an alkylene oxide skeleton containing two of at least one group selected from the group consisting of a methylene group and a methine group.

[0074] In embodiment (B), when the polyether polyol (a2) is one or more polyether polyols (a2-2), the urethane prepolymer (A) typically contains an alkylene oxide skeleton containing three or more groups of at least one type selected from the group consisting of methylene groups and methine groups.

[0075] In embodiment (B), when the polyether polyol (a2) is a mixture of one or more polyether polyols (a2-1) and one or more polyether polyols (a2-2), the urethane prepolymer (A) typically contains an alkylene oxide skeleton containing two of at least one group selected from the group consisting of a methylene group and a methine group, and an alkylene oxide skeleton containing three or more of at least one group selected from the group consisting of a methylene group and a methine group.

[0076] As the compound having a polymerizable unsaturated double bond, any appropriate compound can be used 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 one type or two or more types.

[0077] Examples of the 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, and the compound having a (meth)acryloyl group is preferred in that it can further exhibit the effects of the present invention. The compound having a polymerizable unsaturated double bond may have only one polymerizable unsaturated double bond, or may have two or more polymerizable unsaturated double bonds.

[0078] The content of the compound having a polymerizable unsaturated double bond in the composition (a composition containing a polyol, a compound having a polymerizable unsaturated double bond, and a crosslinking agent) is preferably 0.01 to 50 parts by weight, alternatively 0.1 to 30 parts by weight, alternatively 0.5 to 25 parts by weight, alternatively 1.0 to 20 parts by weight, or alternatively 1.5 to 15 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.

[0079] 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.

[0080] 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.

[0081] Among 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. Preferred hydroxyl group-containing (meth)acrylic acid esters having two or more hydroxyl groups include glycerin mono(meth)acrylate and glycerin di(meth)acrylate, and examples of commercially available products include those sold under the trade names "Blemmer GLM" (manufactured by NOF Corporation), "Blemmer GLM-R" (manufactured by NOF Corporation), "Blemmer GMR-M" (manufactured by NOF Corporation), and "Blemmer GMR-R" (manufactured by NOF Corporation).

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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 40 parts by weight, 0.1 to 35 parts by weight, 1 to 35 parts by weight, 5 to 35 parts by weight, or 10 to 35 parts by weight, relative to 100 parts by weight of the polyol.

[0090] 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.

[0091] Examples of tertiary amine compounds include triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7 (DBU).

[0092] 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.

[0093] 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.

[0094] 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.

[0095] The urethane prepolymer (A) may be prepared without using a catalyst, in which case the reaction temperature may be 100° C. or higher.

[0096] 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.

[0097] 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.

[0098] When preparing the urethane prepolymer (A), any suitable other components can be used in any suitable amount as long as they do not impair the effects of the present invention.Other components include, for example, crosslinking accelerators, silane coupling agents, antistatic agents, antioxidants, UV absorbers, light stabilizers, other resin components, tackifiers, crosslinking retarders, inorganic fillers, organic fillers, 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.Other components may be one type only, or two or more types.

[0099] <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.

[0100] 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.

[0101] 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).

[0102] 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 2.9, and may be 0.2 to 2.5, 0.2 to 2.0, 0.3 to 1.5, 0.3 to 1.3, 0.3 to 1.1, 0.3 to 0.9, or 0.3 to 0.7. 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.

[0103] 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 0.3 to 13 parts by weight, or may be 0.3 to 11 parts by weight, 0.5 to 9.0 parts by weight, 0.5 to 7.0 parts by weight, 0.7 to 5.0 parts by weight, 0.7 to 3.0 parts by weight, 0.9 to 2.0 parts by weight, or 1.0 to 1.5 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.

[0104] <A-2-3. Photopolymerization initiator (C)> The pressure-sensitive adhesive composition contains a photopolymerization initiator (C). The photopolymerization initiator (C) may be one type only, or two or more types may be used.

[0105] Photopolymerization initiators are generally classified into intramolecular cleavage-type photopolymerization initiators and hydrogen abstraction-type photopolymerization initiators depending on the reaction that occurs after absorbing light. Intramolecular cleavage-type photopolymerization initiators are photopolymerization initiators that generate radicals by intramolecular cleavage. For example, by absorbing light of a specific wavelength, a bond at a specific site in the molecule is cleaved, generating radicals at the cleaved site, which then serve as polymerization initiation species and initiate polymerization. Hydrogen abstraction-type photopolymerization initiators are photopolymerization initiators that generate radicals by exchanging hydrogen between two molecules. For example, by absorbing light of a specific wavelength, they become excited, and the excited species undergo a hydrogen abstraction reaction from a surrounding hydrogen donor, generating active radical species, which then serve as polymerization initiation species and initiate polymerization.

[0106] Examples of the intramolecular cleavage type photopolymerization initiator include alkylphenone-based photopolymerization initiators, aminoalkylphenone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, and oxime ester-based photopolymerization initiators.

[0107] Examples of the alkylphenone-based radical photopolymerization initiator include a benzyl methyl ketal-based photopolymerization initiator and an α-hydroxyalkylphenone-based photopolymerization initiator.

[0108] An example of the benzyl methyl ketal photopolymerization initiator is 2,2-dimethoxy-2-phenylacetophenone (commercially available products include Omnirad 651 (manufactured by IGM RESINS BV)).

[0109] Examples of the α-hydroxyalkylphenone-based photoradical polymerization initiator include 1-hydroxycyclohexyl phenyl ketone (commercially available products include Omnirad 184 (manufactured by IGM RESINS B.V.)), 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one.

[0110] Examples of the aminoalkylphenone photopolymerization initiator include 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one and 2-benzylmethyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone.

[0111] Examples of the acylphosphine oxide photopolymerization initiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (commercially available products include Omnirad 819 (manufactured by IGM RESINS B.V.)), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, and ethyl(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

[0112] An example of the oxime ester photopolymerization initiator is (2E)-2-(benzoyloxyimino)-1-[4-(phenylthio)phenyl]octan-1-one.

[0113] Examples of the hydrogen abstraction photopolymerization initiator include a benzophenone-based photopolymerization initiator and a thioxanthone-based photopolymerization initiator.

[0114] Examples of the benzophenone-based photopolymerization initiator include benzophenone, 4-phenylbenzophenone, methyl o-benzoylbenzoate, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone, and 4,4'-bis(dimethylamino)benzophenone.

[0115] Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, and methylbenzoylformate.

[0116] Examples of the hydrogen abstraction photopolymerization initiator include methyl benzoyl formate (commercially available products include Omnirad MBF (manufactured by IGM RESINS B.V.)).

[0117] The photopolymerization initiator (C) preferably has a maximum absorption wavelength between 310 nm and 370 nm, in order to further exhibit the effects of the present invention. When the photopolymerization initiator (C) has a maximum absorption wavelength between 310 nm and 370 nm, the effects of the present invention can be further exhibited, for example, the photopolymerization initiator (C) can exhibit more sufficiently strong adhesive strength to the adherend before UV irradiation, and can exhibit more excellent easy releasability that allows smooth peeling from the adherend after UV irradiation.

[0118] In order to further exert the effects of the present invention, the photopolymerization initiator (C) preferably has a maximum absorbance of 0.007 or more, or may have a maximum absorbance of 0.008 or more, or may have a maximum absorbance of 0.009 or more, or may have a maximum absorbance of 0.010 or more, in a wavelength range of 310 nm to 350 nm when the photopolymerization initiator (C) is dissolved in acrylonitrile at a concentration of 0.0001 g / mL. The upper limit of the maximum absorbance is, for example, 0.100 or less, or may be 0.050 or less.

[0119] The content of the photopolymerization initiator (C) 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 photopolymerization initiator (C) is preferably 0.001 parts by weight or more, may be 0.01 parts by weight or more, may be 0.05 parts by weight or more, may be 0.1 parts by weight or more, may be more than 0.1 parts by weight, may be more than 0.1 parts by weight but not more than 20 parts by weight, may be more than 0.1 parts by weight but not more than 10 parts by weight, may be more than 0.1 parts by weight but not more than 5 parts by weight, may be more than 0.1 parts by weight but not more than 3 parts by weight, may be more than 0.1 parts by weight but not more than 2 parts by weight, may be more than 0.1 parts by weight but not more than 1.5 parts by weight, or may be more than 0.1 parts by weight but not more than 1.0 parts by weight, relative to 100 parts by weight of the urethane prepolymer (A).

[0120] <A-2-4. Antioxidant (D)> The pressure-sensitive adhesive composition contains an antioxidant (D). The antioxidant (D) may be one type, or two or more types.

[0121] When the PSA composition contains the antioxidant (D), the effects of the present invention can be more effectively exhibited, and for example, the storage stability can be excellent.

[0122] The content of the antioxidant (D) in the pressure-sensitive adhesive composition may be any appropriate amount as long as it does not impair the effects of the present invention. In order to further exhibit the effects of the present invention, the content of such antioxidant (D) is preferably 0.001 parts by weight or more, may be 0.01 parts by weight or more, may be 0.05 parts by weight or more, may be 0.10 parts by weight or more, may be 0.10 parts by weight to 10.00 parts by weight, may be 0.20 parts by weight to 5.00 parts by weight, may be 0.30 parts by weight to 3.00 parts by weight, or may be 0.40 parts by weight to 2.00 parts by weight, relative to 100 parts by weight of the urethane prepolymer (A).

[0123] The surface protective film according to an embodiment of the present invention uses a photopolymerization initiator (C) and an antioxidant (D) in combination, and the ratio (weight ratio) of the content of the antioxidant (D) in the pressure-sensitive adhesive composition to the content of the photopolymerization initiator (C) in the pressure-sensitive adhesive composition (hereinafter sometimes referred to as the "antioxidant (D) / photopolymerization initiator (C) content ratio") is preferably 0.10 or more, or may be 0.15 or more, 0.20 or more, 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, or 0.50 or more, in order to further exhibit the effects of the present invention. The upper limit of the antioxidant (D) / photopolymerization initiator (C) content ratio is, for example, less than 10.00, or may be less than 5.00, or may be less than 4.00, or may be less than 3.00, or may be less than 2.70, or may be less than 2.50.

[0124] Any appropriate antioxidant can be used as the antioxidant (D) as long as it does not impair the effects of the present invention. Examples of such antioxidant (D) include hindered phenol-based antioxidants, hindered amine-based antioxidants, phosphite-based antioxidants, phenol-based antioxidants, and thioether-based antioxidants.

[0125] The hindered phenol-based antioxidant may have a structure in which a tertiary butyl group is bonded to at least one carbon atom adjacent to a carbon atom on an aromatic ring to which a phenolic OH group is bonded. Examples of the hindered phenol-based antioxidant include dibutylhydroxytoluene (BHT) and products under the trade names Irganox 1010, Irganox 1010FF, Irganox 1035, Irganox 1035FF, Irganox 1076, Irganox 1076FD, Irganox 1076DWJ, and Irganox 1076FF. 98, Irganox 1135, Irganox 1330, Irganox 1726, Irganox 1425WL, Irganox 1520L, Irganox 245, Irganox 245FF, Irganox 259, Irganox 3114, Irganox 565, and Irganox 295 (all manufactured by BASF).

[0126] The hindered amine antioxidant may have at least one hindered piperidine group in one molecule, and examples of the hindered amine antioxidant include trade names such as Adeka STAB LA-63, Adeka STAB LA-63P, Adeka STAB LA-52, and Adeka STAB LA-57 (all manufactured by ADEKA Corporation).

[0127] Examples of phosphite antioxidants include triphenyl phosphite, diphenyl isodecyl phosphite, and phenyl diisodecyl phosphite; trade names include Adeka STAB 2112, Adeka STAB 2112RG, Adeka STAB 1178, and Adeka STAB 3010 (all manufactured by ADEKA Corporation).

[0128] Examples of the phenolic antioxidant include monophenolic antioxidants, bisphenolic antioxidants, and polymeric phenolic antioxidants, such as 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, and stearin-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate. Examples of bisphenol-based antioxidants include 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), and 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane. Examples of polymeric phenolic antioxidants include 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, and tocophenol.

[0129] Examples of thioether-based antioxidants include those under the trade names Adekastab AO-503 and Adekastab AO-26 (both manufactured by ADEKA Corporation).

[0130] <A-2-5. Urethane (meth)acrylate> The pressure-sensitive adhesive composition may contain urethane (meth)acrylate. When the pressure-sensitive adhesive composition contains urethane (meth)acrylate, the effects of the present invention can be more effectively exhibited, for example, the pressure-sensitive adhesive composition can exhibit more sufficiently strong adhesive strength to the adherend before UV irradiation, and can exhibit excellent easy releasability that allows smooth release from the adherend after UV irradiation.

[0131] The urethane (meth)acrylate may be used alone or in combination of two or more kinds.

[0132] The content of the urethane (meth)acrylate in the pressure-sensitive adhesive composition is preferably 0.5 to 50 parts by weight, alternatively 1.0 to 40 parts by weight, alternatively 1.5 to 30 parts by weight, alternatively 2.0 to 20 parts by weight, alternatively 2.5 to 15 parts by weight, alternatively 3.0 to 10 parts by weight, or alternatively 3.0 to 8.0 parts by weight, relative to 100 parts by weight of the urethane prepolymer (A), in terms of being able to further exhibit the effects of the present invention.

[0133] The number of functional groups of the urethane (meth)acrylate is preferably 2 or more, and may be 3 or more, 3 to 20, 4 to 10, 4 to 8, or 6, in terms of being able to better exhibit the effects of the present invention. When the number of functional groups of the urethane (meth)acrylate is within the above range, the effects of the present invention can be better exhibited.

[0134] The urethane (meth)acrylate preferably has a structure represented by the following general formula (1), in that the effects of the present invention can be more effectively exhibited. When the urethane (meth)acrylate has a structure represented by the following general formula (1), the effects of the present invention can be more effectively exhibited, for example, more sufficiently strong adhesive strength to the adherend can be exhibited before UV irradiation, and more excellent easy releasability can be exhibited, allowing smooth release from the adherend after UV irradiation.

[0135] The urethane (meth)acrylate preferably has a structure represented by the following general formula (1a), in that the effects of the present invention can be more effectively exhibited. When the urethane (meth)acrylate has a structure represented by the following general formula (1a), the effects of the present invention can be more effectively exhibited, for example, more sufficiently strong adhesive strength to the adherend can be exhibited before UV irradiation, and more excellent easy releasability can be exhibited, allowing smooth release from the adherend after UV irradiation.

[0136] The urethane (meth)acrylate preferably has a structure represented by the following general formula (2), in that the effects of the present invention can be more effectively exhibited. When the urethane (meth)acrylate has a structure represented by the following general formula (2), the effects of the present invention can be more effectively exhibited, for example, more sufficiently strong adhesive strength to the adherend can be exhibited before UV irradiation, and more excellent easy releasability, allowing smooth release from the adherend after UV irradiation, can be exhibited.

[0137] In general formula (2), X is a divalent aromatic group or a divalent aliphatic group.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] In order to further enhance the effects of the present invention, the urethane (meth)acrylate preferably has a molecular weight of less than 1000. If the molecular weight of the urethane (meth)acrylate (D) is 1000 or more, the effects of the present invention may not be achieved.

[0143] Examples of urethane (meth)acrylates include compounds having a structure represented by the following general formula (4).

[0144] In the general formula (4), X is as defined above.

[0145] <A-2-6. Ionic Compound> The pressure-sensitive adhesive composition may contain an ionic compound. The ionic compound may be one type only, or two or more types.

[0146] Examples of the ionic compound include 1-hexylpyridinium bis(fluorosulfonyl)imide, 1-ethyl-3-methylpyridinium trifluoromethanesulfonate, 1-ethyl-3-methylpyridinium pentafluoroethanesulfonate, 1-ethyl-3-methylpyridinium heptafluoropropanesulfonate, 1-ethyl-3-methylpyridinium nonafluorobutanesulfonate, 1-butyl-3-methylpyridinium trifluoromethanesulfonate, 1-butyl-3-methylpyridinium bis( trifluoromethanesulfonyl)imide, 1-octyl-4-methylpyridinium bis(fluorosulfonyl)imide, 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide, 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-propylpiperidinium bis(fluorosulfonyl)imide, 1-ethyl-3-methylimidazolium trifluorometh fluoropropanesulfonate, 1-ethyl-3-methylimidazolium heptafluoropropanesulfonate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-hexyl-3-methylimidazolium bis(fluorosulfonyl)imide, 1-octyl-3-methylimidazolium bis(fluorosulfonyl)imide, methyltrioctylammonium bis(trifluoromethanesulfonyl)imide, trimethylpropanesulfonate, propyl ammonium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methyl-imidazolium trifluoromethanesulfonate, 1-allyl-3-methyl-imidazolium heptafluoropropanesulfonate, 1-allyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-methyl-imidazolium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0147] The content ratio of the ionic compound relative to 100 parts by weight of the urethane prepolymer (A) is, for example, 0.01 to 10 parts by weight, optionally 0.03 to 7.0 parts by weight, optionally 0.05 to 5.0 parts by weight, optionally 0.1 to 3.0 parts by weight, optionally 0.3 to 2.5 parts by weight, optionally 0.5 to 2.0 parts by weight, or optionally 0.5 to 1.5 parts by weight.

[0148] The ionic compound may be commercially available or synthesized by any suitable method. For example, the ionic liquid may be synthesized by the halide method, hydroxide method, acid ester method, complex formation method, neutralization method, or the like, as described in "Ionic Liquids - The Frontline and Future of Development" (published by CMC Publishing).

[0149] <A-2-7. 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, UV absorbers, light stabilizers, other 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.

[0150] <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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] <<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.

[0158] 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.

[0159] <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.

[0160] <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.

[0161] <Frequency of change in initial adhesive strength to glass plate before / after UV irradiation> The fold change in initial adhesive strength to glass plate before / after UV irradiation relative to the initial adhesive strength to glass plate after UV irradiation was defined as the fold change in initial adhesive strength to glass plate before / after UV irradiation, and was calculated using the following formula: fold change in initial adhesive strength to glass plate before / after UV irradiation = initial adhesive strength to glass plate before / after UV irradiation / initial adhesive strength to glass plate after UV irradiation

[0162] <Initial Adhesion Strength to Glass Plate Before UV Irradiation After Storage Under Fluorescent Light for 1 Day> After production, the surface protection film was stored for 1 day under fluorescent light in an environment of 23°C temperature and 55% RH humidity. Thereafter, 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. This was then left for 30 minutes in an environment of 23°C temperature and 55% RH humidity to obtain an evaluation sample. The obtained evaluation sample was measured using a tensile tester in an environment of 23°C temperature and 55% RH humidity. The tensile tester used was an "Autograph AG-Xplus HS 6000 mm / min High-Speed ​​Model (AG-50NX plus)" manufactured by Shimadzu Corporation. The evaluation sample was set in the tensile tester, and the tensile test was then initiated. The conditions for the tensile test 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 defined as the initial adhesive strength of the surface protective film to the glass plate after storage under a fluorescent lamp for 1 day and before UV irradiation.

[0163] <Rate of change in initial adhesive strength before UV irradiation to glass plate before / after storage> The rate of change from the initial adhesive strength before UV irradiation to the initial adhesive strength before UV irradiation to the glass plate after 1 day of storage under fluorescent lamp was taken as the rate of change in initial adhesive strength before UV irradiation to the glass plate before / after storage, and was calculated using the following formula: Rate of change in initial adhesive strength before UV irradiation to glass plate before / after storage (%) = (initial adhesive strength before UV irradiation to glass plate / initial adhesive strength before UV irradiation to glass plate after 1 day of storage under fluorescent lamp) × 100 (%)

[0164] <Absorbance Measurement> The photopolymerization initiator was diluted 10,000 times with acrylonitrile to prepare an acrylonitrile solution with a concentration of 0.0001 g / mL, and the maximum absorbance and maximum absorption wavelength in the wavelength range of 310 nm to 350 nm were measured using a spectrofluorometer (Hitachi, Ltd., F-7000).

[0165] <Photopolymerization initiators used in Examples and Comparative Examples> Omnirad 184 (manufactured by IGM Resins B.V.): intramolecular cleavage type photopolymerization initiator, 1-hydroxycyclohexyl phenyl ketone, maximum absorption wavelength = 331 nm, maximum absorbance in the wavelength range of 310 nm to 350 nm when made into an acrylonitrile solution at a concentration of 0.0001 g / mL = 0.0068 Omnirad 651 (manufactured by IGM Resins B.V.): intramolecular cleavage type photopolymerization initiator, 2,2-dimethoxy-2-phenylacetophenone, maximum absorption wavelength = 325 nm, maximum absorbance in the wavelength range of 310 nm to 350 nm when made into an acrylonitrile solution at a concentration of 0.0001 g / mL = 0.0111

[0166] Production Example 1 Urethane Prepolymer A 39.1 g of polytetramethylene glycol (product name "PTMG3000" manufactured by Mitsubishi Chemical Corporation), 111.9 g of polyester polyol (product name "Kuraray Polyol P-2010" manufactured by Kuraray Co., Ltd.), 39.1 g of a compound having a polymerizable unsaturated double bond (product name "Blenmer GLM" manufactured by NOF Corporation), and 190 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, 0.09 g of bismuth octoate (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, 60.5 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and while dry air was being introduced, the solution temperature in the experimental apparatus was controlled in a water bath to 80±2°C, and the mixture was maintained for 5 hours. Thereafter, 183.8 g of polypropylene glycol (product name "Sannyx GP-1500", manufactured by Sanyo Chemical Industries, Ltd.) was added, and the solution temperature in the experimental apparatus was controlled in a water bath to 80±2°C, and the mixture was maintained for 2 hours. Thereafter, 15.4 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and the solution temperature in the experimental apparatus was controlled in a water bath to 80±2°C, and the mixture was maintained for 2 hours, thereby obtaining a solution of urethane prepolymer A. Note that toluene was added dropwise as appropriate during the polymerization to control the temperature during polymerization and to prevent a decrease in stirrability due to an increase in viscosity. The solids concentration of the urethane prepolymer A solution was 60 wt%. The formulation and other details are shown in Table 1.

[0167] [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 150.0 g of polypropylene glycol (product name "Sannyx PP-2000", manufactured by Sanyo Chemical Industries, Ltd.), 150.0 g of a polymerizable carbon-double bond-containing diol (product name "Epoxy Ester 200PA", manufactured by Kyoeisha Chemical Co., Ltd.), 272.0 g of toluene (manufactured by Tosoh Corporation) as a solvent, 0.20 g of dibutyltin(IV) dilaurate (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst, and 4.0 g of an antioxidant (product name "Irganox 1010", manufactured by BASF), and the mixture was subjected to dry air replacement at room temperature for 1 hour with stirring. Thereafter, under a dry air inflow and stirring, 76.0 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and the solution temperature in the experimental apparatus was maintained at 65±2°C in a water bath while maintaining the temperature for 8 hours. Then, 22.0 g of a polymerizable carbon-carbon double bond-containing diol (product name "Epoxy Ester 200PA", manufactured by Kyoeisha Chemical Co., Ltd.) and 15.0 g of a polymerizable carbon-carbon double bond-containing triol (product name "Denacol Acrylate DA314", manufactured by Nagase ChemteX Corporation) were added, and the solution temperature in the experimental apparatus was maintained at 65±2°C in a water bath while maintaining the temperature for 8 hours to obtain a solution of urethane prepolymer B. During the polymerization, toluene was added dropwise as needed to control the temperature during polymerization and to prevent a decrease in stirrability due to increased viscosity. The solids concentration of the urethane prepolymer B solution was 60 wt%. The formulation and other details are shown in Table 1.

[0168]

[0169] [Example 1] 100 parts by weight of the urethane prepolymer A obtained in Production Example 1, 1.4 parts by weight of an isocyanate compound (Coronate HX:C / HX, manufactured by Nippon Polyurethane Industries, Ltd.) as a crosslinking agent, 0.1 parts by weight of Omnirad 651 (manufactured by IGM Resins B.V.) as a photopolymerization initiator, 0.05 parts by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, 5.0 parts by weight of UA-1100H (manufactured by Shin-Nakamura Chemical Co., Ltd.) as a urethane (meth)acrylate, and 0.03 parts by weight of Envirizer OL-1 (manufactured by Tokyo Fine Chemical 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 110°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) consisting of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (1) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protection film (1) was aged at room temperature for 5 days and evaluated. The results are shown in Table 2.

[0170] Example 2 The same procedure as in Example 1 was carried out, except that 0.1 parts by weight of Omnirad 184 (manufactured by IGM Resins B.V.) was used as the photopolymerization initiator instead of 0.1 parts by weight of Omnirad 651 (manufactured by IGM Resins B.V.), to obtain a surface protective film (2) having a configuration of urethane-based pressure-sensitive adhesive composition (2), release liner (thickness 25 μm) / pressure-sensitive adhesive layer (2) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protective film (2) was aged at room temperature for 5 days and evaluated. The results are shown in Table 2.

[0171] [Example 3] The same procedure as in Example 1 was carried out, except that the amount of antioxidant (Irganox 1010) was changed to 0.10 parts by weight, to obtain a surface protection film (3) having a configuration of urethane-based pressure-sensitive adhesive composition (3), release liner (thickness 25 μm) / pressure-sensitive adhesive layer (3) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protection film (3) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 2.

[0172] [Example 4] The same procedure as in Example 3 was carried out, except that the amount of photopolymerization initiator (Omnirad 651) was changed to 0.5 parts by weight, to obtain a surface protection film (4) having a configuration of urethane-based pressure-sensitive adhesive composition (4), release liner (thickness 25 μm) / pressure-sensitive adhesive layer (4) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protection film (4) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 2.

[0173] [Example 5] The same procedure as in Example 4 was carried out, except that the amount of antioxidant (Irganox 1010) was changed to 0.50 parts by weight, to obtain a surface protection film (5) having a configuration of urethane-based pressure-sensitive adhesive composition (5), release liner (thickness 25 μm) / pressure-sensitive adhesive layer (5) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protection film (5) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 2.

[0174] [Example 6] The same procedure as in Example 5 was carried out, except that the amount of antioxidant (Irganox 1010) was changed to 1.50 parts by weight, to obtain a surface protection film (6) having a configuration of urethane-based pressure-sensitive adhesive composition (6), release liner (thickness 25 μm) / pressure-sensitive adhesive layer (6) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protection film (6) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 2.

[0175] Example 7 The same procedure as in Example 5 was carried out, except that urethane (meth)acrylate (UA-1100H) was not used, to obtain a surface protection film (7) having a configuration of urethane-based pressure-sensitive adhesive composition (7), release liner (thickness 25 μm) / pressure-sensitive adhesive layer (7) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protection film (7) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 2.

[0176] Comparative Example 1 The same procedure as in Example 5 was carried out, except that the antioxidant (Irganox 1010) was not used, to obtain a surface protection film (C1) having a configuration of a urethane-based pressure-sensitive adhesive composition (C1), a release liner (thickness 25 μm) / a pressure-sensitive adhesive layer (C1) (thickness 75 μm) / a substrate (thickness 75 μm). The obtained surface protection film (C1) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 2. Comparative Example 2 The same procedure as in Example 1 was carried out, except that 100 parts by weight of the urethane prepolymer A obtained in Production Example 1 was replaced with 100 parts by weight of the urethane prepolymer B obtained in Production Example 2, the amount of the crosslinking agent (C / HX) was changed to 5.0 parts by weight, the amount of the photopolymerization initiator (Omnirad 651) was changed to 1.0 part by weight, the amount of the antioxidant (Irganox 1010) was changed to 1.00 part by weight, and no urethane (meth)acrylate (UA-1100H) was used. A surface protective film (C2) having a urethane-based pressure-sensitive adhesive composition (C2), a release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C2) (thickness 75 μm) / substrate (thickness 75 μm) was obtained. The obtained surface protective film (C2) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 2.

[0177]

[0178] 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.

[0179] 1 Base layer 2 Pressure-sensitive adhesive layer 10 Surface protection film

Claims

1. A surface protection film including 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 photopolymerization initiator (C), and an antioxidant (D), the urethane prepolymer (A) contains an alkylene oxide skeleton containing two or more of at least one kind of group selected from the group consisting of a methylene group and a methine group, and an alkylene oxide skeleton containing three or more of at least one kind of group selected from the group consisting of a methylene group and a methine group, the surface protection film.

2. The surface protection film according to claim 1, wherein the amount of the antioxidant (D) with respect to 100 parts by weight of the urethane prepolymer (A) is 0.10 parts by weight or more.

3. The surface protection film according to claim 1, wherein the ratio of the amount of the antioxidant (D) to the amount of the photopolymerization initiator (C) (antioxidant (D) / photopolymerization initiator (C)) is 0.25 or more by weight ratio.

4. The surface protection film according to claim 1, wherein the ratio of the amount of the antioxidant (D) to the amount of the photopolymerization initiator (C) (antioxidant (D) / photopolymerization initiator (C)) is less than 3.00 by weight ratio.

5. The surface protection film according to claim 1, wherein the amount of the photopolymerization initiator (C) with respect to 100 parts by weight of the urethane prepolymer (A) exceeds 0.1 part by weight.

6. The surface protection film according to claim 1, wherein the adhesive composition contains urethane (meth)acrylate.

7. An optical device including the surface protection film according to any one of claims 1 to 6.

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

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