Surface protective film

Abstract

Provided is a surface protective film which includes an adhesive layer, the surface protective film being capable of exhibiting sufficiently strong adhesive force to an adherend before ultraviolet irradiation, capable of exhibiting excellent easy separability that enables smooth separation from the adherend after ultraviolet irradiation, is capable of maintaining the sufficiently strong adhesive force before ultraviolet irradiation even if used after long-term storage after the production of the surface protective film, and is capable of suppressing the generation of static electricity when separated from the adherend after ultraviolet irradiation. Also provided are an optical device and an electronic device each of which comprising such surface protective film.　A surface protective film according to an embodiment of the present invention includes an adhesive layer. The adhesive that constitutes the adhesive layer is formed of an adhesive composition. The adhesive composition includes a urethane prepolymer (A), a crosslinking agent (B), a photopolymerization initiator (C), and an ionic compound (D). The urethane prepolymer (A) has a polymerizable unsaturated double bond. The ionic compound (D) is composed of: a cationic species selected from the group consisting of onium cations and metal cations; and an anionic species that is not a borate anion.

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] In the manufacturing process of optical and electronic components, it is also important to prevent damage due to static electricity. For example, techniques for adding an antistatic agent to a pressure-sensitive adhesive have been reported (Patent Documents 5 to 7). However, the addition of an antistatic agent may prevent the adhesive from achieving sufficient adhesive strength while surface protection is required. In particular, when a surface protection film is manufactured and then stored for a long period of time, the adhesive strength while surface protection is required may be significantly reduced.

[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 Japanese Patent No. 6896927 Japanese Patent Application Laid-Open No. 9-165460

[0009] The present invention provides a surface protection film including a pressure-sensitive adhesive layer, which is primarily used in the manufacturing process of optical and electronic devices to adhere to exposed surfaces of optical and electronic components to prevent scratches during processing, assembly, inspection, transportation, etc., and which exhibits sufficiently strong adhesion to the adherend before UV irradiation, exhibits excellent easy releasability that allows smooth peeling from the adherend after UV irradiation, and further maintains the sufficiently strong adhesion before UV irradiation even when used after long-term storage after production and can suppress the generation of static electricity when peeled from the adherend after UV irradiation. Another object of the present invention is to provide an optical device and an electronic device that include 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 ionic compound (D), wherein the urethane prepolymer (A) has a polymerizable unsaturated double bond, and the ionic compound (D) is an ionic compound composed of a cation species selected from the group consisting of an onium cation and a metal cation and an anion species other than a borate anion. [2] In the surface protection film according to [1] above, the ionic compound (D) may be liquid at 23°C and atmospheric pressure. [3] In the surface protection film according to [1] or [2] above, the content of the ionic compound (D) per 100 parts by weight of the urethane prepolymer (A) may be 0.1 to 3.0 parts by weight. [4] In the surface protection film according to any one of the above [1] to [3], the pressure-sensitive adhesive composition may contain a urethane (meth)acrylate (E). [5] An optical device according to an embodiment of the present invention includes the surface protection film according to any one of the above [1] to [4]. [6] An electronic device according to an embodiment of the present invention includes the surface protection film according to any one of the above [1] to [4].

[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 and electronic devices to adhere to exposed surfaces of optical and electronic components to prevent scratches on the surfaces during processing, assembly, inspection, transportation, etc., and which exhibits sufficiently strong adhesion to an adherend before UV irradiation, exhibits excellent easy releasability that allows smooth peeling from the adherend after UV irradiation, and further, even when used after long-term storage after production, the surface protection film maintains the sufficiently strong adhesion before UV irradiation and can suppress the generation of static electricity when peeled from the adherend after UV irradiation. Furthermore, optical devices and electronic devices including such surface protection films can be provided.

[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 pressure-sensitive adhesive layer consisting of two or more layers.

[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] In the surface protection film according to an embodiment of the present invention, the 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 23°C and 55% RH, and then the surface protection film is peeled from the glass plate surface at a peel angle of 180° and a peel rate of 300 mm / min in an environment of 23°C and 55% RH. The adhesive strength (hereinafter sometimes referred to as "initial adhesive strength to glass plate before UV irradiation") is preferably 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 releasability will not be exhibited even when irradiated with ultraviolet light. Therefore, the upper limit is preferably, for example, 5000 gf / 25 mm or less, and may be 4000 gf / 25 mm or less, 3500 gf / 25 mm or less, or 3000 gf / 25 mm or less. If the initial adhesive strength to the glass plate before UV irradiation is within the above range, the surface protective film according to an embodiment of the present invention can exhibit, for example, sufficiently strong adhesive strength to the adherend before UV irradiation. If the initial adhesive strength to the glass plate before UV irradiation is too low outside the above range, there is a risk of peeling from the adherend before UV irradiation. Details of the method for measuring the initial adhesive strength to the glass plate before UV irradiation 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, optionally 5.00 gf / 25 mm or less, or optionally less than 5.00 gf / 25 mm. 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 2.00 gf / 25 mm or more, 2.50 gf / 25 mm or more, or even 3.00 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, and therefore the surface protective film according to an embodiment of the present invention can exhibit excellent easy releasability, for example, allowing smooth peeling from the adherend after UV irradiation. 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 from the adherend after UV irradiation. 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 above-mentioned change ratio is within the above-mentioned range, the effects of the present invention can be more effectively exhibited, for example, a sufficiently strong adhesive strength to the adherend can be exhibited before ultraviolet irradiation, and an excellent easy releasability that allows smooth peeling from the adherend can be exhibited after ultraviolet irradiation.

[0023] The surface protection film according to an embodiment of the present invention preferably has an adhesive strength (hereinafter sometimes referred to as "initial adhesive strength to glass plate after one-week storage before UV irradiation") of 500 gf / 25 mm or more, optionally 1000 gf / 25 mm or more, optionally 1300 gf / 25 mm or more, optionally 1500 gf / 25 mm or more, optionally 1800 gf / 25 mm or more, optionally 2000 gf / 25 mm or more, optionally 2100 gf / 25 mm or more, optionally 2200 gf / 25 mm or more, optionally 2300 gf / 25 mm or more, optionally 2500 gf / 25 mm or more, optionally 2600 gf / 25 mm or more, optionally 2700 gf / 25 mm or more, optionally 2800 gf / 25 mm or more, optionally 2900 gf / 25 mm or more, optionally 3000 gf / 25 mm or more, optionally 3100 gf / 25 mm or more, optionally 3200 gf / 25 mm or more, optionally 3300 gf / 25 mm or more, optionally 3400 gf / 25 mm or more, optionally 3500 gf / 25 mm or more, optionally 3600 gf / 25 mm or more, optionally 3700 gf / 25 mm or more, optionally 3800 gf / 25 mm or more, optionally 3900 gf / 25 mm or more, optionally 4000 gf / 25 mm or more, optionally 4100 gf / 25 mm or more, optionally 4200 gf / 25 mm or more, optionally 4300 gf / 25 mm or more, optionally 4400 gf / 25 mm or more, optionally 4500 gf / 25 mm or more, optionally 4600 gf / 25 mm or more, optionally 4700 g The higher the initial adhesive strength before UV irradiation to the glass plate after one week of storage, the better; however, if it is too high, sufficient easy peelability may not be exhibited even when irradiated with ultraviolet light. Therefore, the upper limit is preferably, for example, 5000 gf / 25 mm or less, and may be 4000 gf / 25 mm or less, 3500 gf / 25 mm or less, or 3000 gf / 25 mm or less. If the initial adhesive strength before UV irradiation to the glass plate after one week of storage is within the above range, the surface protective film according to an embodiment of the present invention can maintain a sufficiently strong adhesive strength before ultraviolet light irradiation, for example, even when used after long-term storage of the surface protective film after production. If the initial adhesive strength before UV irradiation to the glass plate after one week of storage is too low outside the above range, for example, when the surface protective film is used after long-term storage of the surface protective film after production, the surface protective film may peel off from the adherend before ultraviolet light irradiation. Note that details of the method for measuring the initial adhesive strength before UV irradiation to the glass plate after one week of storage will be described later.

[0024] In the surface protective film according to an embodiment of the present invention, the rate of increase in the initial adhesive strength to the glass plate before UV irradiation after one week of storage relative to the initial adhesive strength to the glass plate before UV irradiation ((initial adhesive strength to the glass plate before UV irradiation after one week of storage / initial adhesive strength to the glass plate before UV irradiation) × 100%) (sometimes referred to as the "rate of increase in adhesive strength to the glass plate before UV irradiation") is preferably 110% or less, or may be 108% or less, 106% or less, 104% or less, or 102% or less. The lower the rate of increase, the better, but if it is excessively lower than 100%, there is a risk of the film peeling off spontaneously from the adherend in unintended circumstances. For this reason, the lower limit is, for example, preferably 95% or more, or may be 98% or more, 99% or more, or 100% or more. If the rate of increase is within the above range, for example, the surface protective film can maintain a sufficiently strong adhesive strength before UV irradiation even when used after being produced and stored for a long period of time. If the rate of increase is too high and outside the above range, for example, when the surface protection film is produced and then stored for a long period of time before use, the surface protection film may peel off from the adherend before being irradiated with ultraviolet light.

[0025] The surface protective film according to an embodiment of the present invention has a residual adhesion rate after UV irradiation of a glass plate, measured and calculated in an environment of a temperature of 23°C and a humidity of 55% RH, of preferably 50% or more, 70% or more, 80% or more, 85% or more, 90% or more, or even 95% or more. The upper limit of the residual adhesion rate after UV irradiation of a glass plate is, for example, 100% or less. If the residual adhesion rate after UV irradiation of a glass plate is within the above range, the surface protective film according to an embodiment of the present invention can, for example, suppress contamination of the adherend. Details of the method for measuring and calculating the residual adhesion rate after UV irradiation of a glass plate will be described later.

[0026] The surface protection film according to the embodiment of the present invention has an integrated light intensity of 700 mJ / cm 2 when exposed to an LED light source with a wavelength of 365 nm. 2 After the pressure-sensitive adhesive layer is photo-cured by irradiating it with ultraviolet light of 1.0×10, the release liner is peeled off to expose the pressure-sensitive adhesive layer, and the surface resistance of the pressure-sensitive adhesive layer measured under an environment of a temperature of 23° C. and a humidity of 55% RH is preferably 1.0×1011 Ω less than 5.0 × 10 10 Ω or less, and may be 1.0×10 10 Ω or less, and may be 5.0×10 9 Ω or less, and may be 3.0 × 10 9 The smaller the surface resistance value, the better. The lower limit is, for example, 1.0×10 4 When the surface resistance value is within the above range, the surface protection film according to the embodiment of the present invention can, for example, suppress the generation of static electricity when peeled from an adherend.

[0027] The surface protection film according to the embodiment of the present invention is stored for one week in an environment of a temperature of 23°C and a humidity of 55% RH after production, and then exposed to an LED light source with a wavelength of 365 nm and an integrated light amount of 700 mJ / cm 2 After the pressure-sensitive adhesive layer is photo-cured by irradiating it with ultraviolet light of 1.0×10, the release liner is peeled off to expose the pressure-sensitive adhesive layer, and the surface resistance of the pressure-sensitive adhesive layer measured under an environment of a temperature of 23° C. and a humidity of 55% RH is preferably 1.0×10 11 Ω less than 5.0 × 10 10 Ω or less, and may be 1.0×10 10 Ω or less, and may be 5.0×10 9 Ω or less, and may be 3.0 × 10 9 The smaller the surface resistance value, the better. The lower limit is, for example, 1.0×10 4 When the surface resistance value is within the above range, the surface protection film according to the embodiment of the present invention can, for example, suppress the generation of static electricity when peeled from an adherend.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The above heating and drying conditions can be appropriately selected from methods commonly known for forming a pressure-sensitive adhesive layer.

[0032] <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.

[0033] 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.

[0034] 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.

[0035] <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.

[0036] 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.

[0037] The pressure-sensitive adhesive composition contains a urethane prepolymer (A), a crosslinking agent (B), and a photopolymerization initiator (C). In an embodiment of the present invention, by using the urethane prepolymer (A), the crosslinking agent (B), and the photopolymerization initiator (C) in combination as described above 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, the effects of the present invention can be achieved.

[0038] <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.

[0039] The urethane prepolymer (A) may be used alone or in combination of two or more kinds.

[0040] 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.

[0041] 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.

[0042] 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."

[0043] The number average molecular weight Mn of the urethane prepolymer (A) is preferably 3,000 to 1,000,000.

[0044] 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.

[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 1.8, but may also be 0.2 to 1.6, 0.3 to 1.4, 0.3 to 1.2, 0.4 to 1.1, or 0.4 to 0.8. When the equivalent ratio of NCO groups / OH groups is within the above range, the effects of the present invention can be more effectively exhibited.

[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 0.4 to 13 parts by weight, alternatively 0.5 to 11 parts by weight, 0.6 to 9.0 parts by weight, 0.7 to 7.0 parts by weight, 0.8 to 5.0 parts by weight, or 0.9 to 3.0 parts by weight, relative to 100 parts by weight of the urethane prepolymer (A). When the content of the crosslinking agent (B) relative to 100 parts by weight of the urethane prepolymer (A) is within the above range, the effects of the present invention can be more effectively exhibited.

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

[0106] Examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, and anisole methyl ether. Examples of acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzyl-based photopolymerization initiators include benzil. Examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexyl phenyl ketone. Examples of ketal-based photopolymerization initiators include benzil dimethyl ketal. Examples of thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

[0107] The content of the photopolymerization initiator (C) in the pressure-sensitive adhesive composition may be any appropriate amount as long as the effects of the present invention are not impaired. The content of such photopolymerization initiator (C) is preferably 0.001 to 20 parts by weight, or may be 0.01 to 10 parts by weight, or may be 0.1 to 5 parts by weight, relative to 100 parts by weight of the urethane prepolymer (A).

[0108] <A-2-4. Ionic Compound (D)> The PSA composition contains an ionic compound (D). The ionic compound (D) may be one type only, or two or more types may be used.

[0109] The ionic compound (D) is typically an ionic compound composed of a cation species selected from the group consisting of onium cations and metal cations and an anion species other than a borate anion.

[0110] The ionic compound (D) is preferably liquid at 23° C. and atmospheric pressure, from the viewpoint of being able to further exhibit the effects of the present invention. If the ionic compound (D) is not liquid at 23° C. and atmospheric pressure (for example, if it is in a powder form), the effects of the present invention may not be fully exhibited, for example, there is a risk that the ionic compound (D) may not exhibit sufficiently strong adhesive strength to the adherend before ultraviolet irradiation, may not exhibit excellent easy releasability that allows smooth peeling from the adherend after ultraviolet irradiation, and there is a risk that the sufficiently strong adhesive strength before ultraviolet irradiation may not be maintained when the surface protection film is used after being produced and stored for a long period of time.

[0111] The ionic compound (D) may preferably employ, as the cationic species, a cationic species selected from the group consisting of onium cations and metal cations, in that the effects of the present invention can be more effectively exhibited.

[0112] As the onium cation, any appropriate onium cation can be used as long as it does not impair the effects of the present invention. In terms of further exhibiting the effects of the present invention, such onium cation can be, for example, at least one selected from the group consisting of nitrogen-containing onium cations, sulfur-containing onium cations, and phosphorus-containing onium cations.

[0113] Representative embodiments of the onium cation include onium cations represented by general formulas (A) to (E).

[0114]

[0115] In formula (A), R a represents a hydrocarbon group having 4 to 20 carbon atoms, and R b , R c Each of R independently represents hydrogen or a hydrocarbon group having 1 to 16 carbon atoms. a , R b , R c may contain a heteroatom. When the nitrogen atom is bonded to the nitrogen atom through a double bond, R c There is no.

[0116] In formula (B), R d represents a hydrocarbon group having 2 to 20 carbon atoms, and R e , R f , R g R each independently represents hydrogen or a hydrocarbon group having 1 to 16 carbon atoms. d , R e , R f , R g may contain heteroatoms.

[0117] In formula (C), R h represents a hydrocarbon group having 2 to 20 carbon atoms, and R i , R j , R k R each independently represents hydrogen or a hydrocarbon group having 1 to 16 carbon atoms. h , R i , R j , R k may contain heteroatoms.

[0118] In formula (D), Z represents a nitrogen, sulfur, or phosphorus atom; R l , R m , R n , R o each independently represents a hydrocarbon group having 1 to 20 carbon atoms, which may contain a heteroatom. However, when Z is a sulfur atom, R o There is no.

[0119] In formula (E), Rp represents a hydrocarbon group having 1 to 18 carbon atoms, which may contain a heteroatom.

[0120] Examples of the cation represented by formula (A) include a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a cation having a pyrroline skeleton, and a cation having a pyrrole skeleton.

[0121] Specific examples of the pyridinium cation include a 1-ethylpyridinium cation, a 1-butylpyridinium cation, a 1-hexylpyridinium cation, a 1-butyl-3-methylpyridinium cation, a 1-ethyl-3-methylpyridinium cation, a 1-butyl-4-methylpyridinium cation, a 1-hexyl-3-methylpyridinium cation, a 1-octyl-4-methylpyridinium cation, and a 1-butyl-3,4-dimethylpyridinium cation.

[0122] Specific examples of piperidinium cations include 1-propylpiperidinium cation, 1-pentylpiperidinium cation, 1,1-dimethylpiperidinium cation, 1-methyl-1-ethylpiperidinium cation, 1-methyl-1-propylpiperidinium cation, 1-methyl-1-butylpiperidinium cation, 1-methyl-1-pentylpiperidinium cation, 1-methyl-1-hexylpiperidinium cation, 1-methyl-1-heptylpiperidinium cation, 1-ethyl-1-propylpiperidinium cation, 1-ethyl-1-butylpiperidinium cation, 1-ethyl-1-pentylpiperidinium cation, 1-ethyl-1-hexylpiperidinium cation, 1-ethyl-1-heptylpiperidinium cation, 1,1-dipropylpiperidinium cation, 1-propyl-1-butylpiperidinium cation, and 1,1-dibutylpiperidinium cation.

[0123] Specific examples of the pyrrolidinium cation include a 1,1-dimethylpyrrolidinium cation, a 1-methyl-1-ethylpyrrolidinium cation, a 1-methyl-1-propylpyrrolidinium cation, a 1-methyl-1-butylpyrrolidinium cation, a 1-methyl-1-pentylpyrrolidinium cation, a 1-methyl-1-hexylpyrrolidinium cation, a 1-methyl-1-heptylpyrrolidinium cation, a 1-ethyl-1-propylpyrrolidinium cation, a 1-ethyl-1-butylpyrrolidinium cation, a 1-ethyl-1-pentylpyrrolidinium cation, a 1-ethyl-1-hexylpyrrolidinium cation, a 1-ethyl-1-heptylpyrrolidinium cation, a 1,1-dipropylpyrrolidinium cation, a 1-propyl-1-butylpyrrolidinium cation, and a 1,1-dibutylpyrrolidinium cation.

[0124] Examples of the cation represented by formula (B) include an imidazolium cation, a tetrahydropyrimidinium cation, and a dihydropyrimidinium cation.

[0125] Specific examples of the imidazolium cation include 1,3-dimethylimidazolium cation, 1,3-diethylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-decyl-3-methylimidazolium cation, 1-dodecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1,2-dimethyl-3-propylimidazolium cation, 1-ethyl-2,3-dimethylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, and 1-hexyl-2,3-dimethylimidazolium cation.

[0126] Specific examples of the tetrahydropyrimidinium cation include a 1,3-dimethyl-1,4,5,6-tetrahydropyrimidinium cation, a 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidinium cation, a 1,2,3,4-tetramethyl-1,4,5,6-tetrahydropyrimidinium cation, and a 1,2,3,5-tetramethyl-1,4,5,6-tetrahydropyrimidinium cation.

[0127] Specific examples of the dihydropyrimidinium cation include a 1,3-dimethyl-1,4-dihydropyrimidinium cation, a 1,3-dimethyl-1,6-dihydropyrimidinium cation, a 1,2,3-trimethyl-1,4-dihydropyrimidinium cation, a 1,2,3-trimethyl-1,6-dihydropyrimidinium cation, a 1,2,3,4-tetramethyl-1,4-dihydropyrimidinium cation, and a 1,2,3,4-tetramethyl-1,6-dihydropyrimidinium cation.

[0128] Examples of the cation represented by formula (C) include a pyrazolium cation and a dihydropyrazolium cation.

[0129] Specific examples of the cation represented by formula (C) include a 1-methylpyrazolium cation, a 3-methylpyrazolium cation, and a 1-ethyl-2-methyldihydropyrazolium cation.

[0130] Examples of the cation represented by formula (D) include a tetraalkylammonium cation, a trialkylsulfonium cation, and a tetraalkylphosphonium cation. In addition, cations in which some of the alkyl groups in these cations have been substituted with alkenyl groups, alkoxyl groups, or epoxy groups can also be used. l , R m , R n , R o As described above, R is a hydrocarbon group having 1 to 20 carbon atoms, and is preferably an alkyl group having 1 to 20 carbon atoms. l , R m , R n , R omay be an aromatic ring group or an aliphatic ring group.

[0131] Specific examples of the cation represented by formula (D) include N,N-dimethyl-N-ethyl-N-propylammonium cation, N,N-dimethyl-N-ethyl-N-butylammonium cation, N,N-dimethyl-N-ethyl-N-pentylammonium cation, N,N-dimethyl-N-ethyl-N-hexylammonium cation, N,N-dimethyl-N-ethyl-N-heptylammonium cation, N,N-dimethyl-N-ethyl-N-nonylammonium cation, N,N-dimethyl-N,N-dipropylammonium cation, N,N-dimethyl-N-propyl-N-butylammonium cation, N,N-dimethyl-N-propyl-N-pentylammonium cation, N,N-dimethyl-N-propyl-N-hexylammonium cation, N,N-dimethyl-N-propyl-N-heptylammonium cation, N,N-dimethyl-N-butyl-N-hexylammonium cation, N,N-dimethyl-N-butyl ...pentylammonium cation, N,N-dimethyl-N-propyl-N-hexylammonium cation, N,N-dimethyl-N-propyl-N-heptylammonium cation, N,N-dimethyl-N-butyl-N-hexylammonium cation, N,N-dimethyl-N-butyl-N-heptylammonium cation, N,N-dimethyl-N-butyl-N-heptylammonium cation, N,N-dimethyl-N-butyl-N-pentylammonium cation, N,N-dimethyl-N-propyl-N-hexylammonium cation, N,N-dimethyl-N-butyl-N-heptylammonium cation, N,N-dimethyl-N-butyl-N-pentylammonium cation, N,N-dimethyl-N N-butyl-N-pentyl-N-hexylammonium cation, N,N-dimethyl-N,N-dihexylammonium cation, trimethylheptylammonium cation, N,N-diethyl-N-methyl-N-propylammonium cation, N,N-diethyl-N-methyl-N-pentylammonium cation, N,N-diethyl-N-methyl-N-heptylammonium cation, N,N-diethyl-N-propyl-N-pentylammonium cation, triethylmethylammonium cation, triethylpropylammonium cation, triethylpentylammonium cation, triethylheptylammonium cation, N,N-dipropyl-N-methyl-N-ethylammonium cation, N,N-dipropyl-N-methyl-N-pentylammonium cation, N,N-dipropyl-N-butyl-N-hexylammonium cation, N,N-dipropyl-N,N-dihexylammonium cation, N,N-dibutyl-N-methyl-N-pentylammonium cation, N,Tetraalkylammonium cations such as N-dibutyl-N-methyl-N-hexylammonium cation, trioctylmethylammonium cation, N-methyl-N-ethyl-N-propyl-N-pentylammonium cation, tetramethylammonium cation, tetraethylammonium cation, tetrabutylammonium cation, tetrahexylammonium cation, tributylethylammonium cation, trimethyldecylammonium cation, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium cation, glycidyltrimethylammonium cation, and diallyldimethylammonium cation; trialkylsulfonium cations such as trimethylsulfonium cation, triethylsulfonium cation, tributylsulfonium cation, trihexylsulfonium cation, diethylmethylsulfonium cation, dibutylethylsulfonium cation, and dimethyldecylsulfonium cation; and tetraalkylphosphonium cations such as tetramethylphosphonium cation, tetraethylphosphonium cation, tetrabutylphosphonium cation, tetrahexylphosphonium cation, phosphonium cation, triethylmethylphosphonium cation, tributylethylphosphonium cation, and trimethyldecylphosphonium cation.

[0132] Specific examples of the cation represented by formula (E) include, for example, R p Examples of the alkyl group include sulfonium salts having an alkyl group having 1 to 18 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, a tridecyl group, a tetradecyl group, and an octadecyl group.

[0133] As the metal cation, any appropriate metal cation can be used as long as it does not impair the effects of the present invention. In terms of being able to further exhibit the effects of the present invention, such metal cation is preferably an alkali metal cation such as a Li cation, a Na cation, or a K cation.

[0134] The ionic compound (D) may preferably use an anion species other than a borate anion, since this can further enhance the effects of the present invention. Using a borate anion as the anion species may result in the effects of the present invention not being achieved. In particular, even if the generation of static electricity during peeling of a surface protection film from an adherend can be suppressed, when the surface protection film is used after long-term storage after production, it may not maintain sufficient adhesive strength for the duration of surface protection. Examples of such borate anions include bis(oxalate)borate, bis(mandelato)borate, bis(salicylate)borate, bis(malonato)borate, bis(succinato)borate, bis(gluturato)borate, and bis(adipato)borate.

[0135] As the anion species other than the borate anion, any appropriate anion species other than the borate anion may be adopted as long as it does not impair the effects of the present invention. In terms of further exhibiting the effects of the present invention, such anion species other than the borate anion may include, for example, a fluorine-containing anion.

[0136] As the fluorine-containing anion, any appropriate fluorine-containing anion can be adopted as long as it does not impair the effects of the present invention.

[0137] Examples of such fluorine-containing anions include fluorinated arylsulfonates, perfluoroalkanesulfonates, bis(fluorosulfonyl)imides, bis(perfluoroalkanesulfonyl)imides, cyanoperfluoroalkanesulfonylamides, bis(cyano)perfluoroalkanesulfonylmethides, cyano-bis-(perfluoroalkanesulfonyl)methides, tris(perfluoroalkanesulfonyl)methides, trifluoroacetates, perfluoroalkylates, tris(perfluoroalkanesulfonyl)methides, and (perfluoroalkanesulfonyl)trifluoroacetamides. Specific examples include trifluoromethanesulfonate, pentafluoroethanesulfonate, heptafluoropropanesulfonate, nonafluorobutanesulfonate, bis(fluorosulfonyl)imides, and bis(trifluoromethanesulfonyl)imides.

[0138] As the ionic compound (D), in terms of being able to more effectively exhibit the effects of the present invention, preferred are 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 trifluoromethanesulfonate, 1-butyl-3-methylpyridinium bis(fluorosulfonyl)imide, 1-ethyl-3-methylpyridinium trifluoromethanesulfonate, 1-ethyl-3-methylpyridinium heptafluoropropanesulfonate, 1-ethyl-3-methylpyridinium nonafluorobutanesulfonate, 1-butyl-3-methylpyridinium trifluoromethane ... 1-octyl-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-methylimidazo ammonium trifluoromethanesulfonate, 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, Examples of suitable bis(fluorosulfonyl)imides include trimethylpropylammonium 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.

[0139] The content ratio of the ionic compound (D) relative to 100 parts by weight of the urethane prepolymer (A) is preferably 0.01 to 10 parts by weight, alternatively 0.03 to 7.0 parts by weight, 0.05 to 5.0 parts by weight, 0.1 to 3.0 parts by weight, 0.3 to 2.5 parts by weight, 0.5 to 2.0 parts by weight, or 0.5 to 1.5 parts by weight, in order to further exhibit the effects of the present invention. If the content of the ionic compound (D) relative to 100 parts by weight of the urethane prepolymer (A) is too low and outside the above range, the effects of the present invention may not be achieved, for example, the film may not be able to exhibit sufficiently strong adhesive strength to the adherend before UV irradiation, or it may not be able to exhibit excellent easy releasability that allows smooth peeling from the adherend after UV irradiation, or when the surface protection film is used after being produced and stored for a long period of time, the sufficiently strong adhesive strength before UV irradiation may not be maintained, or static electricity may be noticeable when peeling from the adherend. If the content of the ionic compound (D) relative to 100 parts by weight of the urethane prepolymer (A) is too high and outside the above range, the adherend may be contaminated.

[0140] 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).

[0141] <A-2-5. Urethane (meth)acrylate (E)> The pressure-sensitive adhesive composition may contain a urethane (meth)acrylate (E). When the pressure-sensitive adhesive composition contains a urethane (meth)acrylate (E), 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 more excellent easy releasability that allows smooth peeling from the adherend after UV irradiation.

[0142] The urethane (meth)acrylate (E) may be used alone or in combination of two or more kinds.

[0143] The content of the urethane (meth)acrylate (E) 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.

[0144] The number of functional groups of the urethane (meth)acrylate (E) 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 further exhibit the effects of the present invention. When the number of functional groups of the urethane (meth)acrylate (E) is within the above range, the effects of the present invention can be further exhibited.

[0145] The urethane (meth)acrylate (E) 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 (E) 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 ultraviolet irradiation, and more excellent easy releasability that allows smooth peeling from the adherend can be exhibited after ultraviolet irradiation.

[0146] The urethane (meth)acrylate (E) 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 (E) 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 an adherend can be exhibited before ultraviolet irradiation, and more excellent easy releasability that allows smooth peeling from an adherend can be exhibited after ultraviolet irradiation.

[0147] The urethane (meth)acrylate (E) 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 (E) 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 ultraviolet irradiation, and more excellent easy releasability that allows smooth peeling from the adherend can be exhibited after ultraviolet irradiation.

[0148] In general formula (2), X is a divalent aromatic group or a divalent aliphatic group.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] In order to further exhibit the effects of the present invention, the urethane (meth)acrylate (E) preferably has a molecular weight of less than 1000. If the molecular weight of the urethane (meth)acrylate (E) is 1000 or more, the effects of the present invention may not be exhibited.

[0154] Examples of the urethane (meth)acrylate (E) include compounds having a structure represented by the following general formula (4).

[0155] In the general formula (4), X is as defined above.

[0156] <A-2-6. Other Components> The pressure-sensitive adhesive composition may contain any appropriate other components as long as they do not impair the effects of the present invention. Examples of such other components include solvents, catalysts, crosslinking accelerators, silane coupling agents, antioxidants, UV absorbers, light stabilizers, 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.

[0157] <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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] <<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.

[0165] 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.

[0166] <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.

[0167] <Initial Adhesion Strength to Glass Plate After 1 Week of Storage and Before UV Irradiation> After producing the surface protection film, it was stored for 1 week in an environment of 23°C and 55% RH. The release liner was then removed and the surface protection film (25 mm wide x 140 mm long) 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. 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. The evaluation sample was set in the tensile tester, and the tensile test was then started. 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 one week of storage and before UV irradiation.

[0168] <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.

[0169] <Increase in adhesive strength to glass plate before UV irradiation> The increase in adhesive strength to glass plate before UV irradiation after one week of storage relative to the initial adhesive strength to glass plate before UV irradiation was defined as the increase in adhesive strength to glass plate before UV irradiation, and was calculated using the following formula: Increase in adhesive strength to glass plate before UV irradiation (%) = (initial adhesive strength to glass plate before UV irradiation after one week of storage / initial adhesive strength to glass plate before UV irradiation) × 100 (%)

[0170] <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

[0171] <Residual Adhesion Rate After UV Irradiation to Glass Plate> 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, an LED light source with a wavelength of 365 nm was used to apply an integrated light intensity of 700 mJ / cm 2The adhesive layer was photocured by irradiating ultraviolet light of 1000 nm to prepare an evaluation sample. The obtained evaluation sample was left for 24 hours in an environment of 23 ° C. and 55% RH, and then the surface protective film was peeled off using a tensile tester under the conditions of a peel angle of 180 degrees and a peel speed (pulling speed): 300 mm / min. Then, a 19 mm wide No. 31B tape (manufactured by Nitto Denko Corporation, substrate thickness = 25 μm, total thickness = 53 μm) cut to a length of 150 mm was attached to the peel surface of the glass plate using a 2 kg hand roller once in an environment of 23 ° C. and 55% RH, and then left for 30 minutes in an environment of 23 ° C. and 55% RH. Then, the No. 31B tape was peeled off using a tensile tester under the conditions of a peel angle of 180 degrees and a peel speed (pulling speed): 300 mm / min, and the peel strength (A) was measured. Separately, a 19 mm wide No. 31B tape (manufactured by Nitto Denko Corporation, substrate thickness = 25 μm, total thickness = 53 μm) cut to a length of 150 mm was similarly applied to a glass plate to which the surface protective film had not been attached or peeled as described above, and the glass plate was left for 30 minutes in an environment of 23°C temperature and 55% RH. After that, the No. 31B tape was peeled off using a tensile tester under the conditions of a peel angle of 180° and a peel rate (pulling rate): 300 mm / min in an environment of 23°C temperature and 55% RH, and the peel force (B) was measured. The residual adhesion rate to the glass plate was calculated using the following formula. Residual adhesion rate to glass plate (%) = (peel force (A) / peel force (B)) × 100 (%). The tensile tester used was an "Autograph AG-Xplus HS 6000 mm / min high-speed model (AG-50NX plus)" manufactured by Shimadzu Corporation. The residual adhesion rate to glass plate after UV irradiation is an indicator of the extent to which the components contained in the pressure-sensitive adhesive layer of the surface protective film are transferred to the surface of the adherend and contaminate it. The higher the value of the residual adhesion rate to glass plate after UV irradiation, the less likely the surface protective film is to contaminate the surface of the adherend, and the lower the value of the residual adhesion rate, the more likely the surface protective film is to contaminate the surface of the adherend.

[0172] <Surface resistance value of adhesive surface after UV irradiation> The surface protection film was cut into a size of 50 mm length x 50 mm width. Then, it was irradiated with an LED light source with a wavelength of 365 nm with an integrated light amount of 700 mJ / cm2 The adhesive layer was photocured by irradiating ultraviolet light of 1000 W at 1000 W at 23°C and 55% RH to obtain a sample for evaluation. The release liner was peeled off from the obtained sample for evaluation to expose the adhesive layer, and a terminal was pressed against the adhesive layer at 10 V for 10 seconds using a Trek Japan "Model 152P-2P" to measure the surface resistance. The surface resistance was expressed as "x x 10 y (Ω)" may be written as "xE+y(Ω)".

[0173] <Surface resistance of adhesive surface after UV irradiation after 1 week of storage> After production, the surface protection film was stored for 1 week in an environment of 23°C and 55% RH, and then cut into a size of 50 mm length x 50 mm width. After that, it was irradiated with an LED light source with a wavelength of 365 nm at an integrated light intensity of 700 mJ / cm 2 The adhesive layer was photocured by irradiating ultraviolet light of 1000 W at 1000 W at 23°C and 55% RH to obtain a sample for evaluation. The release liner was peeled off from the obtained sample for evaluation to expose the adhesive layer, and a terminal was pressed against the adhesive layer at 10 V for 10 seconds using a Trek Japan "Model 152P-2P" to measure the surface resistance. The surface resistance was expressed as "x x 10 y (Ω)" may be written as "xE+y(Ω)".

[0174] <Ionic compounds and abbreviations used in the examples and comparative examples> EMI-FSI: 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide HMI-FSI: 1-hexyl-3-methylimidazolium bis(fluorosulfonyl)imide OMI-FSI: 1-octyl-3-methylimidazolium bis(fluorosulfonyl)imide BMP-TFMSI: 1-butyl-3-methylpyridinium bis(trifluoromethanesulfonyl)imide Li-TFSI: lithium bis(trifluoromethanesulfonyl)imide HMI-BOB: 1-hexyl-3-methylimidazolium bis(oxalate)borate OMI-BOB: 1-octyl-3-methylimidazolium bis(oxalate)borate Li-BOB: lithium bis(oxalate)borate

[0175] 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%.

[0176] [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 Co., Ltd.) as a crosslinking agent, 0.05 parts by weight of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide as an ionic compound, 1.0 parts by weight of Irganox 1010 (manufactured by BASF) as an antioxidant, 1.0 parts by weight of Omnirad 651 (manufactured by IGM Resins B.V.) as a photopolymerization initiator, 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 (product name "MRF25", manufactured by Mitsubishi Chemical Corporation, thickness 25 μm) having one side silicone-treated 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 1.

[0177] [Example 2] The same procedure as in Example 1 was carried out, except that the amount of the ionic compound was changed to 0.1 parts by weight, to obtain a surface protective film (2) having a configuration of a urethane-based pressure-sensitive adhesive composition (2), a release liner (thickness 25 μm) / a pressure-sensitive adhesive layer (2) (thickness 75 μm) / a substrate (thickness 75 μm). The obtained surface protective film (2) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0178] [Example 3] The same procedure as in Example 1 was carried out, except that the amount of the ionic compound was changed to 0.3 parts by weight, to obtain a surface protective 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 protective film (3) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0179] [Example 4] The same procedure as in Example 1 was carried out, except that the amount of the ionic compound was changed to 1.0 part by weight, to obtain a surface protective film (4) having a configuration of a urethane-based pressure-sensitive adhesive composition (4), a release liner (thickness 25 μm) / a pressure-sensitive adhesive layer (4) (thickness 75 μm) / a substrate (thickness 75 μm). The obtained surface protective film (4) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0180] [Example 5] The same procedure as in Example 1 was carried out, except that the amount of the ionic compound was changed to 5.0 parts by weight, to obtain a surface protective film (5) having a configuration of a urethane-based pressure-sensitive adhesive composition (5), a release liner (thickness 25 μm) / a pressure-sensitive adhesive layer (5) (thickness 75 μm) / a substrate (thickness 75 μm). The obtained surface protective film (5) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0181] Example 6 The same procedure as in Example 1 was carried out, except that 1.0 part by weight of 1-hexyl-3-methylimidazolium bis(fluorosulfonyl)imide was used as the ionic compound instead of 0.05 part by weight of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, to obtain a surface protective 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 protective film (6) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0182] Example 7 The same procedure as in Example 1 was carried out, except that 1.0 part by weight of 1-octyl-3-methylimidazolium bis(fluorosulfonyl)imide was used as the ionic compound instead of 0.05 part by weight of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, to obtain a surface protective 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 protective film (7) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0183] Example 8 The same procedure as in Example 1 was carried out, except that 1.0 part by weight of 1-butyl-3-methylpyridinium bis(trifluoromethanesulfonyl)imide was used as the ionic compound instead of 0.05 part by weight of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide, to obtain a surface protective film (8) having a configuration of urethane-based pressure-sensitive adhesive composition (8), release liner (thickness 25 μm) / pressure-sensitive adhesive layer (8) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protective film (8) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0184] Example 9 The same procedure as in Example 1 was carried out, except that 1.0 part by weight of lithium bis(trifluoromethanesulfonyl)imide was used instead of 0.05 part by weight of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide as the ionic compound, to obtain a surface protective film (9) having a configuration of urethane-based pressure-sensitive adhesive composition (9), release liner (thickness 25 μm) / pressure-sensitive adhesive layer (9) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protective film (9) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0185] [Example 10] 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 Co., Ltd.) as a crosslinking agent, 1.0 parts by weight of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide as an ionic compound, 5.0 parts by weight of UA-1100H (manufactured by Shin-Nakamura Chemical Co., Ltd.) as a urethane (meth)acrylate, 1.0 parts by weight of Irganox 1010 (manufactured by BASF Corporation) as an antioxidant, 1.0 parts by weight of Omnirad 651 (manufactured by IGM Resins B.V.) as a photopolymerization initiator, 0.03 parts by weight of Envirizer OL-1 (manufactured by Tokyo Fine Chemical Co., Ltd.) as a catalyst, diluted with ethyl acetate so that the total solids content was 50% by weight to obtain a urethane-based pressure-sensitive adhesive composition (10). The obtained urethane-based pressure-sensitive adhesive composition (10) was applied to a substrate made of polyester resin (product name "T100-75S", manufactured by Mitsubishi Chemical Corporation, thickness 75 μm) so that the thickness after drying would be 75 μm, and the coating was 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 (10) on the substrate. Next, the silicone-treated surface of a release liner made of polyester resin (product name "MRF25", manufactured by Mitsubishi Chemical Corporation, thickness 25 μm) having one side silicone-treated was laminated to the surface of the obtained pressure-sensitive adhesive layer (10), thereby obtaining a surface protection film (10) consisting of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (10) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protection film (10) was aged at room temperature for 5 days and evaluated. The results are shown in Table 1.

[0186] Comparative Example 1 The same procedure as in Example 1 was carried out, except that 1.0 part by weight of 1-hexyl-3-methylimidazolium bis(oxalate)borate was used instead of 0.05 part by weight of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide as the ionic compound, to obtain a surface protective film (C1) having a configuration of urethane-based pressure-sensitive adhesive composition (C1), release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C1) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protective film (C1) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0187] Comparative Example 2 The same procedure as in Example 1 was carried out, except that 1.0 part by weight of 1-octyl-3-methylimidazolium bis(oxalate)borate was used instead of 0.05 part by weight of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide as the ionic compound, to obtain a urethane-based pressure-sensitive adhesive composition (C2) and a surface protective film (C2) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C2) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protective film (C2) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0188] Comparative Example 3 The same procedure as in Example 1 was carried out, except that 1.0 part by weight of lithium bis(oxalate)borate was used instead of 0.05 part by weight of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide as the ionic compound, to obtain a urethane-based pressure-sensitive adhesive composition (C3) and a surface protective film (C3) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C3) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protective film (C3) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0189] Comparative Example 4 The same procedure as in Example 1 was carried out, except that no ionic compound was used, to obtain a urethane-based pressure-sensitive adhesive composition (C4), and a surface protection film (C4) having a configuration of release liner (thickness 25 μm) / pressure-sensitive adhesive layer (C4) (thickness 75 μm) / substrate (thickness 75 μm). The obtained surface protection film (C4) was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0190]

[0191] 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.

[0192] 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 ionic compound (D), the urethane prepolymer (A) has a polymerizable unsaturated double bond, and the ionic compound (D) is an ionic compound composed of a cation species selected from the group consisting of onium cations and metal cations and an anion species other than a borate anion. The surface protection film.

2. The surface protection film according to claim 1, wherein the ionic compound (D) is liquid at 23 ° C. and atmospheric pressure.

3. The surface protection film according to claim 1, wherein the content of the ionic compound (D) with respect to 100 parts by weight of the urethane prepolymer (A) is 0.1 part by weight to 3.0 parts by weight.

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

5. An optical device including the surface protection film according to any one of claims 1 to 4.

6. An electronic device including the surface protection film according to any one of claims 1 to 4.

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