Surface protective film

Abstract

The present invention provides a surface protection film that exhibits excellent ultraviolet absorption capabilities, and preferably, further exhibits excellent peelability and excellent low-stain properties. It also provides optical and electronic components containing such a surface protection film. [Solution] The surface protection film according to an embodiment of the present invention is a surface protection film comprising a substrate and an adhesive layer, wherein the adhesive layer is composed of a urethane-based adhesive, the urethane-based adhesive is formed from a urethane-based adhesive composition, the urethane-based adhesive composition comprises a base polymer (A), a polyfunctional isocyanate compound (B), a light release agent (C), and an ultraviolet absorber (D), the base polymer (A) comprises a urethane prepolymer, and the content of the ultraviolet absorber (D) in the urethane-based adhesive composition is 0.50 parts by weight or more per 100 parts by weight of the base polymer (A).

Description

Technical Field

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

Background Art

[0002] In the manufacturing process of optical members and electronic members, in order to prevent the surfaces of the optical members and the electronic members from being damaged during processing, assembly, inspection, transportation, etc., generally, a surface protection film having a base material and an adhesive layer is attached to the exposed surfaces of the optical members and the electronic members. Such a surface protection film is peeled off from the optical member or the electronic member when the need for surface protection disappears (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Many optical members and electronic members protected by the surface protection film are inferior in durability and stability against ultraviolet rays. For this reason, there is a problem that ultraviolet rays transmitted through the surface protection film damage the optical members and the electronic members.

[0005] Therefore, the present inventors have studied whether the above problems can be avoided by imparting ultraviolet ray absorption ability to the surface protection film. As a result, when various ultraviolet absorbers were contained in the adhesive layer of the surface protection film, it was found that the ultraviolet ray absorption ability could or could not be exhibited depending on the composition in the adhesive layer, and furthermore, excellent light peelability and excellent low contamination property, which are preferable as the surface protection film, could not be exhibited.

[0006] The object of the present invention is to provide a surface protective film that can exhibit excellent ultraviolet absorption ability, and preferably, further exhibit excellent peelability and excellent low-stain properties. Another object of the present invention is to provide optical components and electronic components that include such a surface protective film. [Means for solving the problem]

[0007] [1] The surface protective film according to an embodiment of the present invention is A surface protective film comprising a substrate and an adhesive layer, The adhesive layer is composed of a urethane-based adhesive. The urethane-based adhesive is formed from a urethane-based adhesive composition, The urethane adhesive composition comprises a base polymer (A), a polyfunctional isocyanate compound (B), a light release agent (C), and an ultraviolet absorber (D). The base polymer (A) contains a urethane prepolymer, The amount of the ultraviolet absorber (D) in the urethane adhesive composition is 0.50 parts by weight or more per 100 parts by weight of the base polymer (A). [2] In the surface protective film described in [1] above, the amount of the ultraviolet absorber (D) in the urethane adhesive composition may be 1.00 part by weight or more per 100 parts by weight of the base polymer (A). [3] In the surface protective film described in [1] or [2] above, the amount of the ultraviolet absorber (D) in the urethane adhesive composition may be 6.00 parts by weight or less per 100 parts by weight of the base polymer (A). [4] In the surface protective film described in any of [1] to [3] above, the ultraviolet absorber (D) may be at least one selected from the group consisting of benzotriazole-based ultraviolet absorbers and triazine-based ultraviolet absorbers. [5] In the surface protective film described in any of [1] to [4] above, the equivalent ratio ([NCO] / [OH]) of the NCO group of the polyfunctional isocyanate compound (B) to the OH group of the base polymer (A) may be 1.00 or more. [6] In the surface protective film described in any of [1] to [5] above, the equivalent ratio ([NCO] / [OH]) of the NCO group of the polyfunctional isocyanate compound (B) to the OH group of the base polymer (A) may be 4.60 or less. [7] In the surface protective film described in any of [1] to [6] above, the content of the light release agent (C) in the urethane adhesive composition may be 0.20 parts by weight or more per 100 parts by weight of the base polymer (A). [8] In the surface protective film described in any of [1] to [7] above, the content of the light release agent (C) in the urethane adhesive composition may be 0.70 parts by weight or less per 100 parts by weight of the base polymer (A). [9] An optical component according to an embodiment of the present invention includes a surface protective film as described in any of [1] to [8] above.

[10] An electronic component according to an embodiment of the present invention includes a surface protective film as described in any of [1] to [8] above. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a surface protective film that exhibits excellent ultraviolet absorption ability, and preferably, further exhibits excellent peelability and excellent low-stain properties. According to the present invention, it is possible to provide optical components and electronic components that include such a surface protective film. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view of a surface protective film according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] Where the term "weight" appears in this specification, it may be interpreted as "mass," which is the commonly used SI unit for weight.

[0011] In this specification, the expression "(meth)acrylic" means "acrylic and / or methacrylic," the expression "(meth)acrylate" means "acrylate and / or methacrylate," the expression "(meth)allyl" means "allyl and / or methallyl," and the expression "(meth)acrolein" means "acrolein and / or metacrolein."

[0012] A. Surface protective film The surface protection film according to an embodiment of the present invention includes a substrate and an adhesive layer. The surface protection film according to an embodiment of the present invention may include any other suitable member (any other suitable layer, etc.) as long as it includes a substrate and an adhesive layer, without impairing the effects of the present invention.

[0013] One embodiment of the surface protection film of the present invention comprises a substrate, an adhesive layer, and a release liner (sometimes referred to as a release sheet or separator) provided on the surface of the adhesive layer opposite to the substrate. Another embodiment of the surface protection film of the present invention comprises a substrate and an adhesive layer.

[0014] Figure 1 is a schematic cross-sectional view of a surface protection film according to one embodiment of the present invention. In Figure 1, the surface protection film 10 comprises a base material 1, an adhesive layer 2, and a release liner 3. In Figure 1, the base material 1, the adhesive layer 2, and the release liner 3 are directly laminated.

[0015] The thickness of the surface protective film according to the embodiments of the present invention can be any appropriate thickness as long as it does not impair the effects of the present invention. The thickness of the surface protective film according to the embodiments of the present invention is preferably 5 μm to 500 μm, but may also be 10 μm to 450 μm, 15 μm to 400 μm, or 20 μm to 300 μm.

[0016] The surface protection film according to an embodiment of the present invention can exhibit excellent ultraviolet absorption ability. The transmittance of ultraviolet light with a wavelength of 365 nm is preferably 50% or less, and may be 0% to 30%, may be 0% to 20%, may be 0% to 10%, or may be 0% to 5.0%. The lower the transmittance of ultraviolet light with a wavelength of 365 nm, the more excellent ultraviolet absorption ability the surface protection film according to an embodiment of the present invention can exhibit.

[0017] The peel strength (I) of the surface protection film according to an embodiment of the present invention against a glass plate after being left at a temperature of 23 °C for 30 minutes is preferably 30.0 gf / 25 mm or less, and may be 10.0 gf / 25 mm or less, may be 5.00 gf / 25 mm or less, may be 3.00 gf / 25 mm or less, may be 2.00 gf / 25 mm or less, may be 1.70 gf / 25 mm or less, may be 1.50 gf / 25 mm or less, may be 1.20 gf / 25 mm or less, or may be 1.00 gf / 25 mm or less. If the peel strength (I) against the glass plate is within the above range, the surface protection film according to an embodiment of the present invention can exhibit excellent easy-peelability. In order to prevent unintended peeling from occurring in the manufacturing process or the like, the lower limit value of the peel strength (I) against the glass plate is, for example, 0.10 gf / 25 mm or more, and may be 0.50 gf / 25 mm or more.

[0018] The peel strength (I) against the glass plate is the peel strength when the adhesive layer contained in the surface protection film is bonded to the surface of the glass plate, left at a temperature of 23 °C for 30 minutes, and then the surface protection film is peeled from the surface of the glass plate at a peeling angle of 180 degrees and a peeling speed of 300 mm / min at a temperature of 23 °C. A more detailed measurement method will be described later.

[0019] The surface protection film according to an embodiment of the present invention preferably has a peel strength (II) against a glass plate of 30.0 gf / 25 mm or less, may be 10.0 gf / 25 mm or less, may be 7.00 gf / 25 mm or less, may be 5.00 gf / 25 mm or less, may be 4.00 gf / 25 mm or less, may be 3.00 gf / 25 mm or less, may be 2.50 gf / 25 mm or less, or may be 2.00 gf / 25 mm or less after being left at 50°C for one day. If the peel strength (II) against the glass plate is within the above range, the surface protection film according to the embodiment of the present invention can suppress the decrease in light peelability over time. For example, the lower limit value of the peel strength (II) against the glass plate is 0.10 gf / 25 mm or more, and may be 0.50 gf / 25 mm or more, so that unintended peeling does not occur during the manufacturing process or the like.

[0020] The peel strength (II) against the glass plate is the peel strength when the adhesive layer contained in the surface protection film is bonded to the surface of the glass plate, left at 50°C for one day, and then the surface protection film is peeled from the surface of the glass plate at a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 23°C. A more detailed measurement method will be described later.

[0021] The surface protection film according to an embodiment of the present invention preferably has a rate of increase in peel strength over time from the peel strength (I) against the glass plate to the peel strength (II) against the glass plate (rate of increase in peel strength over time (%) = (peel strength (II) against the glass plate / peel strength (I) against the glass plate) × 100 (%)) of 250% or less, may be 220% or less, may be 200% or less, may be 180% or less, may be 160% or less, may be 140% or less, may be 130% or less, may be 120% or less, or may be 115% or less. If the rate of increase in peel strength over time is within the above range, the surface protection film according to the embodiment of the present invention can more effectively suppress the decrease in light peelability over time. The lower limit value of the rate of increase in peel strength over time is preferably as small as possible, for example, 100% or more.

[0022] The surface protection film according to the embodiment of the present invention preferably has a residual adhesion rate to the glass plate of 70% or more, but may be 80% or more, 85% or more, 90% or more, 93% or more, or 95% or more. This residual adhesion rate to the glass plate is an indicator of the extent to which the components of the adhesive layer of the surface protection film are transferred to the surface of the adherend and contaminate it. A lower value for this residual adhesion rate to the glass plate indicates that the adherend is contaminated, and a higher value for this residual adhesion rate to the glass plate indicates that the surface protection film exhibits excellent low-contamination properties that do not contaminate the adherend. The upper limit of the above residual adhesion rate to the glass plate is preferably as high as possible, for example, 100% or less.

[0023] The above residual adhesion rate to the glass plate was determined by applying the adhesive layer contained in the surface protective film to the surface of the glass plate, leaving it at 23°C for 24 hours, then peeling the surface protective film from the surface of the glass plate at a peeling angle of 180 degrees and a peeling speed of 300 mm / min at 23°C, applying adhesive tape (product name "No. 31B", manufactured by Nitto Denko Corporation, base material thickness = 25 μm, total thickness = 53 μm) to the peeled surface of the glass plate, leaving it at 23°C for 30 minutes, and then peeling at a peeling angle of 180 degrees and a peeling speed of 300 mm / min. The peeling force (A) when peeling is measured, and separately, adhesive tape (product name "No.31B", manufactured by Nitto Denko Corporation, base material thickness = 25 μm, total thickness = 53 μm) is similarly applied to the peeling surface of a glass plate that has not undergone the above-mentioned bonding and peeling of surface protective film, and after being left at a temperature of 23°C for 30 minutes, the peeling force (B) is measured when peeling is performed at a peeling angle of 180 degrees and a peeling speed of 300 mm / min, and the residual adhesion rate to the glass plate (%) is calculated as (peeling force (A) / peeling force (B)) × 100 (%). A more detailed measurement method will be described later.

[0024] The surface protective film according to the embodiment of the present invention can be manufactured by any suitable method. Such a manufacturing method is, for example, (1) A method of applying an adhesive layer forming material onto a substrate, heating and drying as necessary, and curing as necessary. (2) A method of applying an adhesive layer forming material onto a release liner, heating and drying as necessary, and curing as necessary to form an adhesive layer, and then transferring the resulting adhesive layer onto a substrate. (3) A method of forming and coating an adhesive layer by extruding the adhesive layer forming material onto a substrate, (4) A method of extruding a substrate and an adhesive layer in two or multiple layers, (5) A method of laminating an adhesive layer onto a substrate as a single layer, or a method of laminating an adhesive layer together with a laminate layer as a double layer. (6) A method of laminating an adhesive layer and a substrate forming material such as a film or laminate layer in two or multiple layers. This can be carried out in accordance with any suitable manufacturing method. Any suitable method can be used for the coating method described above. For example, roll coater, comma coater, die coater, reverse coater, silkscreen, and gravure coater methods can be used.

[0025] ≪A-1. Base material≫ The base material may consist of only one layer or two or more layers. The base material may also be stretched.

[0026] The thickness of the substrate is preferably 4 μm to 450 μm, but may also be 8 μm to 400 μm, 12 μm to 350 μm, or 16 μm to 250 μm.

[0027] For surfaces of the substrate that do not have an adhesive layer, a release treatment can be performed by adding, for example, fatty acid amides, polyethyleneimines, long-chain alkyl additives, etc., to the substrate for the purpose of forming a winding body that is easy to unwind, or a coating layer made of any suitable release agent such as silicone-based, long-chain alkyl-based, or fluorine-based can be provided.

[0028] Any suitable material can be used for the base material, depending on the application. Examples include plastics, paper, metal films, and nonwoven fabrics. Preferably, it is plastic. That is, the base material is preferably a plastic film. The base material may be composed of one type of material or two or more types of materials. For example, it may be composed of two or more types of plastics.

[0029] Examples of the above-mentioned plastics include polyester resins, polyamide resins, and polyolefin resins. Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

[0030] The substrate may contain any suitable additives as needed. Examples of additives that may be included in the substrate include antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, fillers, and pigments. The type, number, and amount of additives that may be included in the substrate can be appropriately set according to the purpose. In particular, when the material of the substrate is plastic, it is preferable to include some of the above-mentioned additives for purposes such as preventing degradation. From the viewpoint of improving weather resistance, antioxidants, ultraviolet absorbers, light stabilizers, and fillers are particularly preferred as additives.

[0031] ≪A-2. Adhesive Layer≫ The adhesive layer is composed of a urethane-based adhesive. The urethane-based adhesive is formed from a urethane-based adhesive composition. In other words, the adhesive layer is composed of a urethane-based adhesive, and the urethane-based adhesive is formed from a urethane-based adhesive composition. Typically, the urethane-based adhesive formed from the urethane-based adhesive composition forms a layered structure, thus creating the adhesive layer.

[0032] The adhesive layer can be formed by any suitable method. Such methods include, for example, applying a urethane-based adhesive composition onto any suitable substrate, heating and drying as necessary, and curing as necessary to form an adhesive layer on the substrate; or applying a urethane-based adhesive composition onto a release liner, heating and drying as necessary, and curing as necessary to transfer the adhesive layer formed on the release liner onto the substrate. The application method, heating and drying conditions, curing conditions, etc., can be appropriately adopted from methods commonly known for forming adhesive layers.

[0033] The thickness of the adhesive layer can be appropriately set according to the purpose of the present invention, as long as it does not impair the effects of the present invention. The thickness of the adhesive layer is preferably 5 μm to 150 μm, but may also be 10 μm to 120 μm, 20 μm to 110 μm, 30 μm to 100 μm, or 40 μm to 90 μm.

[0034] In the surface protective film according to embodiments of the present invention, the urethane adhesive typically includes a urethane polymer. The urethane polymer in the urethane adhesive may be one type or two or more types.

[0035] Generally, urethane polymers are known as "prepolymer-type urethane polymers," which are manufactured using urethane prepolymers, and "one-shot type urethane polymers," which are manufactured using polyols (polyols other than urethane prepolymers) without using urethane prepolymers.

[0036] Prepolymer-type urethane polymers can be produced by any suitable method, as long as it does not impair the effects of the present invention, using a method employing a urethane reaction between a urethane prepolymer and, if necessary, a polyol (a polyol other than the urethane prepolymer) and a polyfunctional isocyanate compound. One-shot-type urethane polymers can be produced by any suitable method, as long as it does not impair the effects of the present invention, using a method employing a urethane reaction between a polyol (a polyol other than the urethane prepolymer) and a polyfunctional isocyanate compound.

[0037] In embodiments of the present invention, the urethane polymer contained in the urethane adhesive is typically a prepolymer-type urethane polymer. The prepolymer-type urethane polymer may be one type or two or more types.

[0038] In embodiments of the present invention, the content of urethane polymer in the urethane adhesive is preferably 60% to 99.9% by weight on a solid content basis, but may also be 70% to 99.9% by weight, 80% to 99.9% by weight, 85% to 99.9% by weight, or 90% to 99.9% by weight. The effects of the present invention can be more fully expressed when the content of urethane polymer in the urethane adhesive is within the above range on a solid content basis.

[0039] In embodiments of the present invention, the urethane adhesive composition comprises a base polymer (A), a polyfunctional isocyanate compound (B), a light release agent (C), and an ultraviolet absorber (D).

[0040] The base polymer (A) contains a urethane prepolymer. The urethane prepolymer may be one type or two or more types.

[0041] The content of the urethane prepolymer in the base polymer (A) is preferably 50% to 100% by weight, but may be 60% or more and less than 100% by weight, 70% to 99.999% by weight, 80% to 99.99% by weight, 85% to 99.9% by weight, 90% to 99% by weight, or 95% to 98% by weight.

[0042] The base polymer (A) may contain a low molecular weight polyol. Here, "low molecular weight polyol" refers to a low molecular weight polyol other than a urethane prepolymer. The low molecular weight polyol may be one type or two or more types.

[0043] The content of low molecular weight polyol in the base polymer (A) is preferably 0% to 50% by weight, but may be greater than 0% and 40% or less by weight, 0.001% to 30% by weight, 0.01% to 20% by weight, 0.1% to 15% by weight, 1% to 10% by weight, or 2% to 8% by weight.

[0044] The total content of urethane prepolymer and low molecular weight polyol in the base polymer (A) is preferably 50% to 100% by weight, but may be 60% to 100% by weight, 70% to 100% by weight, 80% to 100% by weight, 90% to 100% by weight, 95% to 100% by weight, 98% to 100% by weight, or substantially 100% by weight.

[0045] The base polymer (A) may contain any other suitable base polymer, as long as it does not impair the effects of the present invention.

[0046] The preparation of the prepolymer-type urethane polymer can be carried out by curing a urethane-based adhesive composition containing a urethane prepolymer and, optionally, a polyol (a polyol other than the urethane prepolymer) and a polyfunctional isocyanate compound, as long as it does not impair the effects of the present invention. For example, such a method involves applying a urethane-based adhesive composition containing a urethane prepolymer and, optionally, a polyol (a polyol other than the urethane prepolymer) and a polyfunctional isocyanate compound onto any suitable substrate, heating and drying as necessary, and curing as necessary, to prepare the polymer in the adhesive layer formed on the substrate. The application method, heating and drying conditions, curing conditions, etc., can be appropriately adopted from methods commonly known for forming adhesive layers.

[0047] <A-2-1.ウレタンプレポリマー> Urethane prepolymers can react with polyfunctional isocyanate compounds to form prepolymer-type urethane polymers.

[0048] The urethane prepolymer may be of one type or two or more types.

[0049] The urethane prepolymer is preferably a polyurethane polyol, and more preferably obtained by reacting a polyol with a polyfunctional isocyanate compound.

[0050] The number-average molecular weight (Mn) of urethane prepolymers is, for example, between 3,000 and 1,000,000.

[0051] The polyol comprises at least one selected from the group consisting of polyester polyols and polyether polyols. Typically, the polyol consists of at least one selected from the group consisting of polyester polyols and polyether polyols. The polyester polyol may consist of only one type or two or more types. The polyether polyol may consist of only one type or two or more types.

[0052] As the polyester polyol, any polyester polyol that can be commonly used in the preparation of urethane prepolymers may be used as appropriate. Examples of such polyester polyols include those obtained by reacting an acid component with a glycol component. Examples of acid components include terephthalic acid, adipic acid, azelaic acid, sebatic acid, phthalic anhydride, isophthalic acid, and trimellitic acid. Examples of glycol components 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. Other examples of polyester polyols include those obtained by ring-opening polymerization of lactones such as polycaprolactone, poly(β-methyl-γ-valerolactone), and polyvalerolactone.

[0053] Polyester polyols can be used with molecular weights ranging from low to high. The number-average molecular weight (Mn) of the polyester polyol is, for example, 100 to 100,000, preferably 100 to 10,000.

[0054] As the polyether polyol, any polyether polyol that can be commonly used in the preparation of urethane prepolymers may be used as appropriate. Examples of such polyether polyols include those containing two or more functional groups, such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Typically, polyether polyols containing two or more of at least one group selected from the group consisting of methylene groups and methine groups are used. The polyether polyol can be used in combination with glycols such as ethylene glycol or polyhydric amines such as ethylenediamine, as needed, by substituting a portion of it.

[0055] The polyether polyol can be used with a molecular weight ranging from low to high. The number-average molecular weight (Mn) of the polyether polyol is, for example, 100 to 100,000, preferably 100 to 10,000.

[0056] One embodiment of the polyol is embodiment (A), which includes both polyester polyol and polyether polyol. In embodiment (A), typically, the polyol consists of both polyester polyol and polyether polyol.

[0057] In embodiment (A), the content of polyester polyol in the polyol is preferably 0.1% to 99.9% by weight, but may be 1% to 99% by weight, 5% to 95% by weight, 10% to 90% by weight, 20% to 80% by weight, or 30% to 70% by weight.

[0058] In embodiment (A), the content of polyether polyol in the polyol is preferably 0.1% to 99.9% by weight, but may be 1% to 99% by weight, 5% to 95% by weight, 10% to 90% by weight, 20% to 80% by weight, or 30% to 70% by weight.

[0059] In embodiment (A), the polyether polyol is typically a polyether polyol containing two or more groups of at least one type selected from the group consisting of methylene groups and methine groups. For example, it may consist only of a polyether polyol containing two groups of at least one type selected from the group consisting of methylene groups and methine groups, or it may consist of a polyether polyol containing two groups of at least one type selected from the group consisting of methylene groups and methine groups and a polyether polyol containing three or more groups of at least one type selected from the group consisting of methylene groups and methine groups. Examples of polyether polyols containing two groups of at least one type selected from the group consisting of methylene groups and methine groups include polyethylene glycol and polypropylene glycol. An example of a polyether polyol containing three or more groups of at least one type selected from the group consisting of methylene groups and methine groups is polytetramethylene glycol.

[0060] Another embodiment of the polyol is embodiment (B), which includes a polyether polyol but does not include a polyester polyol. In embodiment (B), the polyol typically consists of a polyether polyol.

[0061] In embodiment (B), the polyether polyol is typically a polyether polyol containing two or more groups of at least one type selected from the group consisting of methylene groups and methine groups. For example, it may consist only of a polyether polyol containing two or more groups of at least one type selected from the group consisting of methylene groups and methine groups, or it may consist of a polyether polyol containing two or more groups of at least one type selected from the group consisting of methylene groups and methine groups and a polyether polyol containing three or more groups of at least one type selected from the group consisting of methylene groups and methine groups. Examples of polyether polyols containing two or more groups of at least one type selected from the group consisting of methylene groups and methine groups include polyethylene glycol and polypropylene glycol. An example of a polyether polyol containing three or more groups of at least one type selected from the group consisting of methylene groups and methine groups is polytetramethylene glycol.

[0062] To obtain a urethane prepolymer, the polyfunctional isocyanate compound reacted with the polyol may be one type or two or more types.

[0063] As the polyfunctional isocyanate compound, any suitable polyfunctional isocyanate compound that can be used in the preparation of urethane prepolymers can be employed. 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.

[0064] 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.

[0065] Examples of polyfunctional alicyclic isocyanate compounds include 3-isocyanate methyl-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(isocyanate methyl)cyclohexane, 1,4-bis(isocyanate methyl)cyclohexane, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

[0066] Examples of polyfunctional aromatic isocyanate compounds include 1,3-phenylenediisocyanate, 1,4-phenylenediisocyanate, 2,4-tolylenediisosoanate, 2,6-tolylenediisocyanate, 2,2'-diphenylmethanediisocyanate, 4,4'-diphenylmethanediisocyanate, 4,4'-toluidinediisocyanate, 2,4,6-triisocyanatetoluene, 1,3,5-triisocyanatebenzene, 4,4'-diphenyletherdiisocyanate, 4,4'-diphenyldiisocyanate, 1,5-naphthalenediisocyanate, 4,4',4"-triphenylmethanetriisocyanate, dianisidinediisocyanate, and xylylenediisocyanate.

[0067] 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-tetramethylxylylenediisocyanate, and 1,3-tetramethylxylylenediisocyanate.

[0068] Examples of polyfunctional isocyanate compounds include the trimethylolpropane adduct derivatives of the various polyfunctional isocyanate compounds mentioned above, the biuret derivatives obtained by reaction with water, and trimers having an isocyanurate ring. These may also be used in combination.

[0069] Examples of polyfunctional isocyanate compounds include the trimethylolpropane adduct derivatives of the various polyfunctional isocyanate compounds mentioned above, the biuret derivatives obtained by reaction with water, and trimers having an isocyanurate ring. These may also be used in combination.

[0070] In preparing urethane prepolymers, it is preferable to use a polyfunctional isocyanate compound and a polyol in an equivalent ratio such that the isocyanate groups (NCO groups) of the polyfunctional isocyanate compound are fewer than the hydroxyl groups (OH groups) of the polyol. The equivalent ratio ([NCO] / [OH]) of the NCO groups of the polyfunctional isocyanate compound to the OH groups of the polyol is preferably 0.10 to 0.99, but may also be 0.20 to 0.95 or 0.30 to 0.90.

[0071] A catalyst may be used when preparing the urethane prepolymer. Any suitable catalyst can be used as such, as long as it does not impair the effects of the present invention. Examples of such catalysts include tertiary amine catalysts and organometallic catalysts. One catalyst may be used, or two or more catalysts may be used.

[0072] Examples of tertiary amine catalysts include triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7(DBU).

[0073] Examples of organometallic catalysts 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, tetrabutyltitanate, 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.

[0074] When a catalyst is used in preparing the urethane prepolymer, the amount of catalyst used is preferably 0.0001% to 1.0% by weight relative to the total amount of the polyol and the polyfunctional isocyanate compound, and may also be 0.001% to 1.0% by weight, 0.003% to 1.0% by weight, or 0.005% to 1.0% by weight.

[0075] When a catalyst is used in preparing urethane prepolymers, the reaction temperature is preferably below 100°C, but may be between 85°C and 95°C. Above 100°C, controlling the reaction rate and crosslinking structure may become difficult.

[0076] When preparing urethane prepolymers, a catalyst may not be used. In this case, the reaction temperature is preferably 100°C or higher, and may also be 110°C or higher. Furthermore, when preparing urethane prepolymers without a catalyst, it is preferable to allow the reaction to proceed for 3 hours or more.

[0077] Any suitable method can be used to prepare the urethane prepolymer, as long as it does not impair the effects of the present invention. Examples of such methods include 1) a method of charging the polyol, catalyst, and polyfunctional isocyanate compound into a reaction vessel, and 2) a method of charging the polyol and catalyst into a reaction vessel and then adding the polyfunctional isocyanate compound. In method 2), the polyol and polyfunctional isocyanate compound may be added in addition after the polyfunctional isocyanate compound has been added.

[0078] Any suitable solvent can be used when preparing urethane prepolymers. Examples of such solvents include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone.

[0079] When preparing the urethane prepolymer, any other suitable components may be used as long as they do not impair the effects of the present invention. Examples of other components include antioxidants, UV absorbers, light stabilizers, resin components, tackifiers, crosslinking retarders, inorganic fillers, organic fillers, metal powders, pigments, foils, softeners, anti-aging agents, conductive agents, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, and lubricants. There may be only one or more of these other components. Among the other components, antioxidants, UV absorbers, and light stabilizers are among the preferred embodiments.

[0080] Examples of antioxidants include radical chain inhibitors and peroxide decomposers. Examples of radical chain inhibitors include phenolic antioxidants and amine-based antioxidants. Examples of peroxide decomposers include sulfur-based antioxidants and phosphorus-based antioxidants.

[0081] Examples of UV absorbers include benzophenone-based UV absorbers, benzotriazole-based UV absorbers, salicylic acid-based UV absorbers, oxalic acid anilide-based UV absorbers, cyanoacrylate-based UV absorbers, and triazine-based UV absorbers.

[0082] Examples of the light stabilizer include, for example, hindered amine light stabilizers.

[0083] <A-2-2. Low molecular weight polyol> Any suitable low molecular weight polyol can be employed as long as it does not impair the effects of the present invention. Examples of such low molecular weight polyols preferably include polyols having a number average molecular weight Mn of 1500 or less. The number average molecular weight Mn of the low molecular weight polyol is preferably 1400 or less and may be 1300 or less, 1200 or less, 1100 or less, or 1000 or less. The lower limit of the number average molecular weight Mn of the low molecular weight polyol is preferably 50 or more and may be 100 or more, 150 or more, 200 or more, or 250 or more.

[0084] Examples of the low molecular weight polyol preferably include, for example, polyester polyol, polyether polyol, polycaprolactone polyol, polycarbonate polyol, and castor oil-based polyol. More preferably, the low molecular weight polyol is a polyether polyol.

[0085] Examples of the polyether polyol include polyether polyols obtained by addition polymerization of alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide using water, low molecular weight polyols (such as propylene glycol, ethylene glycol, glycerin, trimethylolpropane, pentaerythritol, etc.), bisphenols (such as bisphenol A, etc.), dihydroxybenzene (such as catechol, resorcinol, hydroquinone, etc.) as initiators. Specifically, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxypropylene glyceryl ether, etc. can be mentioned.

[0086] The number of OH groups in the low molecular weight polyol is preferably 2 to 6, more preferably 3 to 5, still more preferably 3 to 4, and particularly preferably 3.

[0087] <A-2-3. Polyfunctional Isocyanate Compound (B)> The urethane-based adhesive composition typically contains a polyfunctional isocyanate compound (B). The polyfunctional isocyanate compound (B) can react with the base polymer (A) to form a prepolymer-type urethane polymer.

[0088] The polyfunctional isocyanate compound (B) may be only one kind or two or more kinds.

[0089] As the polyfunctional isocyanate compound (B), any suitable polyfunctional isocyanate compound that can be used in the urethanization reaction can be adopted. As such a polyfunctional isocyanate compound (B), for example, the polyfunctional isocyanate compound that can be used in the preparation of the urethane prepolymer described above can be adopted.

[0090] The equivalent ratio ([NCO] / [OH]) of the NCO groups (isocyanate groups) in the polyfunctional isocyanate compound (B) to the OH groups (hydroxyl groups) in the base polymer (A) has a lower limit that is preferably 0.50 or more, and may be 1.00 or more, 1.50 or more, 2.00 or more, 2.50 or more, 3.00 or more, 3.10 or more, 3.20 or more, 3.30 or more, 3.40 or more, 3.50 or more. If the lower limit of the above equivalent ratio ([NCO] / [OH]) is within the above range, the surface protection film according to the embodiment of the present invention can exhibit excellent light peelability. If the lower limit of the above equivalent ratio ([NCO] / [OH]) is too small, there is a risk that the light peelability will decrease, for example, there is a risk that the light peelability will decrease over time.

[0091] The equivalent ratio ([NCO] / [OH]) of the NCO groups (isocyanate groups) of the polyfunctional isocyanate compound (B) to the OH groups (hydroxyl groups) of the base polymer (A) has an upper limit that is preferably 5.00 or less, and may be 4.80 or less, 4.70 or less, 4.60 or less, 4.50 or less, 4.40 or less, 4.30 or less. If the upper limit of the equivalent ratio ([NCO] / [OH]) is within the above range, the surface protection film according to the embodiment of the present invention can exhibit excellent easy peelability. If the upper limit of the equivalent ratio ([NCO] / [OH]) is too large, there is a risk of adhesive residue from the adhesive layer.

[0092] The equivalent ratio ([NCO] / [OH]) of the NCO groups (isocyanate groups) of the polyfunctional isocyanate compound (B) to the OH groups (hydroxyl groups) of the base polymer (A) is preferably in the range of 0.50 to 5.00, and may be 1.00 to 4.80, 1.00 to 4.70, 1.00 to 4.60, 1.50 to 4.60, 2.00 to 4.60, 2.50 to 4.60, 3.00 to 4.60, 3.10 to 4.60, 3.20 to 4.60, 3.30 to 4.50, 3.40 to 4.40, 3.50 to 4.30. If the equivalent ratio ([NCO] / [OH]) is within the above range, the surface protection film according to the embodiment of the present invention can exhibit excellent easy peelability. If the equivalent ratio ([NCO] / [OH]) is too small, there is a risk of a decrease in easy peelability, for example, a risk of a decrease in easy peelability over time. If the equivalent ratio ([NCO] / [OH]) is too large, there is a risk of adhesive residue from the adhesive layer.

[0093] <A-2-4. Catalyst> For the urethane-based adhesive composition, a catalyst may be used to promote the reaction between the base polymer (A) and the polyfunctional isocyanate compound (B). As such a catalyst, any suitable catalyst can be used as long as the effects of the present invention are not impaired. Examples of such a catalyst include the catalysts that can be used for the preparation of the urethane prepolymer described above.

[0094] When a catalyst is used for the reaction between the base polymer (A) and the polyfunctional isocyanate compound (B), the content of the catalyst in the urethane-based adhesive composition is preferably 0.0001 parts by weight to 1.0 parts by weight, may be 0.001 parts by weight to 1.0 parts by weight, may be 0.003 parts by weight to 1.0 parts by weight, or may be 0.005 parts by weight to 1.0 parts by weight, based on 100 parts by weight of the base polymer (A).

[0095] <A-2-5. Light release agent (C)> The urethane-based adhesive composition contains a light release agent (C). The light release agent (C) may be only one kind or two or more kinds.

[0096] The content of the light release agent (C) in the urethane-based adhesive composition is preferably 1.00 parts by weight or less, may be 0.90 parts by weight or less, may be 0.80 parts by weight or less, may be 0.70 parts by weight or less, may be 0.01 parts by weight to 0.60 parts by weight, may be 0.10 parts by weight to 0.55 parts by weight, or may be more than 0.20 parts by weight and less than 0.50 parts by weight, based on 100 parts by weight of the base polymer (A). If the content of the light release agent (C) is within the above range, the surface protection film according to the embodiment of the present invention can exhibit excellent light release property and excellent low contamination property. If the content of the light release agent (C) is too small, there is a possibility that excellent light release property cannot be exhibited. If the content of the light release agent (C) is too large, there is a possibility that excellent low contamination property cannot be exhibited.

[0097] As the light release agent (C), any suitable light release agent (C) can be used, provided that it does not impair the effects of the present invention, as long as it can be added to the urethane adhesive to impart light release properties. From the viewpoint of providing the surface protective film according to the embodiment of the present invention with even better light release properties and even better low-stain properties, the light release agent (C) can be at least one selected from the group consisting of silicone compounds, fluorine compounds, and surfactants.

[0098] As for the silicone compound, any suitable silicone compound can be used as long as it functions as a light release agent that can exhibit light release properties when included in an adhesive, as long as it does not impair the effects of the present invention. Examples of such silicone compounds include the silicone compound described in Japanese Patent Application Publication No. 2024-84496.

[0099] As for the fluorine-based compound, any suitable fluorine-based compound can be used, as long as it functions as a light release agent that exhibits light release properties when included in an adhesive, as long as it does not impair the effects of the present invention. Examples of such fluorine-based compounds include the fluorine-based compound described in Japanese Patent Application Publication No. 2024-84496.

[0100] As a surfactant, any suitable surfactant can be used as long as it functions as a light peeling agent that can exhibit light peelability when included in the adhesive, as long as it does not impair the effects of the present invention. Examples of such surfactants include the surfactant described in Japanese Patent Application Publication No. 2024-111800.

[0101] From the viewpoint of providing both excellent peelability and even better low-stain properties with the surface protective film according to the embodiments of the present invention, a silicone-based compound is preferred as the peeling agent (C), and in particular, a silicone-based compound (C1) having a skeleton derived from monomer (a) whose corresponding homopolymer Tg (glass transition temperature) is 80°C or higher is preferred.

[0102] The silicone compound (C1) has a skeleton derived from monomer (a), whose corresponding homopolymer has a glass transition temperature (Tg) of 80°C or higher, thus incorporating a high-Tg polymer skeleton. This results in a compound with both a silicone skeleton and a high-Tg skeleton. The introduction of the silicone skeleton provides excellent easy peelability, and the introduction of the high-Tg polymer skeleton increases the hardness near the interface between the adhesive layer and the adherend. It is presumed that these combined effects enable the achievement of both excellent easy peelability and excellent low-stain properties.

[0103] For homopolymers, the Tg values ​​listed in publicly available documents should be used. For example, the values ​​listed in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. If multiple values ​​are listed in the "Polymer Handbook," the conventional value should be adopted. For monomers not listed in the "Polymer Handbook," the catalog values ​​from the monomer manufacturers should be used. For homopolymers of monomers not listed in the "Polymer Handbook" and for which the monomer manufacturers do not provide catalog values, the values ​​obtained by the measurement method described in Japanese Patent Publication No. 2007-51271 should be used.

[0104] Examples of monomers (a) whose corresponding homopolymer Tg is 80°C or higher include (meth)acrylic acid and (meth)acrylic acid esters whose corresponding homopolymer Tg is 80°C or higher. Examples of (meth)acrylic acid esters whose corresponding homopolymer Tg is 80°C or higher include methyl methacrylate, t-butyl methacrylate, and cyclohexyl methacrylate.

[0105] The silicone compound (C1) may further contain monomer (b) of the corresponding homopolymer having a Tg of 60°C or higher and less than 80°C. The effects of the present invention can be further expressed by the silicone compound (C1) further containing such monomer (b).

[0106] Examples of monomers (b) whose corresponding homopolymer Tg is 60°C or higher and less than 80°C include (meth)acrylic acid esters whose corresponding homopolymer Tg is 60°C or higher and less than 80°C. Examples of (meth)acrylic acid esters whose corresponding homopolymer Tg is 60°C or higher and less than 80°C include ethyl methacrylate.

[0107] The silicone compound (C1) may include at least one selected from the group consisting of M units (R3Si-O-) (a unit in which three of the four bonds of Si are bonded to organic groups R (typically a methyl group) and one to an oxygen atom), D units (R2Si(-O-)2) (a unit in which two of the four bonds of Si are bonded to organic groups R (typically a methyl group) and two to an oxygen atom), T units (R-Si(-O-)3) (a unit in which one of the four bonds of Si is bonded to an organic group R (typically a methyl group) and three to an oxygen atom), and Q units (Si(-O-)4) (a unit in which all four of the four bonds of Si are bonded to an oxygen atom). One preferred embodiment of the silicone compound (C1) includes M units, D units, and T units as basic units containing silicon atoms.

[0108] The silicone compound (C1) may have an alkylene oxide structure. Examples of such alkylene oxide structures include ethylene oxide structures and propylene oxide structures. There may be only one alkylene oxide structure or two or more structures. The effects of the present invention can be more fully expressed when the silicone compound (C1) contains an alkylene oxide structure.

[0109] One preferred embodiment of the silicone-based compound (C1) has a backbone derived from monomer (a) whose Tg (glass transition temperature) of the corresponding homopolymer is 80°C or higher, and further has a backbone derived from monomer (b) whose Tg of the corresponding homopolymer is 60°C or higher and lower than 80°C. Another preferred embodiment of the silicone-based compound (C1) has a backbone derived from monomer (a) whose Tg (glass transition temperature) of the corresponding homopolymer is 80°C or higher, and further has an alkylene oxide structure. Still another preferred embodiment of the silicone-based compound (C1) has a backbone derived from monomer (a) whose Tg (glass transition temperature) of the corresponding homopolymer is 80°C or higher, further has a backbone derived from monomer (b) whose Tg of the corresponding homopolymer is 60°C or higher and lower than 80°C, and further has an alkylene oxide structure.

[0110] The silicone-based compound (C1) may not contain a fluorine atom. By not containing a fluorine atom, it may be possible to comply with PFAS regulations.

[0111] <A-2-6. Ultraviolet Absorbent (D)> The urethane-based adhesive composition contains an ultraviolet absorbent (D). The ultraviolet absorbent (D) may be only one kind or two or more kinds.

[0112] The content of the ultraviolet absorbent (D) in the urethane-based adhesive composition is preferably 0.50 parts by weight or more, may be 1.00 parts by weight or more, may be 1.50 parts by weight or more, may be 1.80 parts by weight or more, or may be 2.00 parts by weight or more with respect to 100 parts by weight of the base polymer (A). If the lower limit of the above content is within the above range, the surface protection film according to the embodiment of the present invention can exhibit excellent ultraviolet absorption ability. If the lower limit of the above content is too small, there is a possibility that sufficient ultraviolet absorption ability cannot be exhibited.

[0113] The amount of ultraviolet absorber (D) in the urethane adhesive composition is preferably 10.00 parts by weight or less, but may be 8.00 parts by weight or less, 7.00 parts by weight or less, 6.00 parts by weight or less, 5.00 parts by weight or less, 4.50 parts by weight or less, or 4.00 parts by weight or less, per 100 parts by weight of the base polymer (A). As long as the upper limit of the above content is within the above range, the surface protective film according to the embodiment of the present invention can exhibit excellent ultraviolet absorption ability. If the upper limit of the above content is too high, there is a risk that the ultraviolet absorber will precipitate from the urethane adhesive.

[0114] The amount of ultraviolet absorber (D) in the urethane adhesive composition is preferably 0.05 to 10.00 parts by weight per 100 parts by weight of the base polymer (A), but may also be 1.00 to 8.00 parts by weight, 1.00 to 7.00 parts by weight, 1.00 to 6.00 parts by weight, 1.50 to 5.00 parts by weight, 1.80 to 4.50 parts by weight, or 2.00 to 4.00 parts by weight. If the above content is within the above range, the surface protective film according to the embodiment of the present invention can exhibit excellent ultraviolet absorption ability. If the above content is too low, sufficient ultraviolet absorption ability may not be achieved. If the above content is too high, the ultraviolet absorber may precipitate from the urethane adhesive.

[0115] As the ultraviolet absorber (D), any suitable ultraviolet absorber can be used as long as it does not impair the effects of the present invention. Examples of such ultraviolet absorbers (D) include benzotriazole ultraviolet absorbers, triazine ultraviolet absorbers, benzophenone ultraviolet absorbers (including oxybenzophenone ultraviolet absorbers), salicylic acid ester ultraviolet absorbers, and cyanoacrylate ultraviolet absorbers. From the viewpoint of providing excellent ultraviolet absorption ability to the surface protective film according to the embodiment of the present invention, it is preferably at least one selected from the group consisting of benzotriazole ultraviolet absorbers and triazine ultraviolet absorbers.

[0116] As the benzotriazole-based ultraviolet absorber, any suitable benzotriazole-based ultraviolet absorber can be used, as long as it does not impair the effects of the present invention. Examples of such benzotriazole-based ultraviolet absorbers include benzotriazole-based ultraviolet absorbers having one benzotriazole skeleton in one molecule.

[0117] Examples of benzotriazole-based UV absorbers include C7-9 branched and linear alkyl esters of 3-(2H-benzotriazole-2-yl)-5-(1,1-dimethylethyl)-4-hydroxybenzenepropanoic acid (Tinuvin 99-2, manufactured by BASF), 2-(2H-benzotriazole-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (Tinuvin 928, manufactured by BASF), and 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole (Tinuvin PS (BASF), C7-9 branched and linear alkyl esters of 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxybenzenepropanoic acid (Tinuvin 384-2, BASF), 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (Tinuvin 900, BASF), 2-(2H-benzotriazol-2-yl)-6 -(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (Tinuvin 928, manufactured by BASF), reaction product of methyl-3-(3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl)propionate / polyethylene glycol 300 (Tinuvin 1130, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-p-cresol (Tinuvin P, manufactured by BASF), 2(2H-benzotriazol-2-yl)-4-6-bis(1-methyl-1-phenylethyl)phenol (Tinuvin 234, manufactured by BASF), 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol (Tinuvin 326, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (Tinuvin 328, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-4-(1,1,3,BASF's benzotriazole-based "T" compounds include 3-tetramethylbutyl)phenol (Tinuvin 329, manufactured by BASF), the reaction product of methyl 3-(3-(2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate and polyethylene glycol 300 (Tinuvin 213, manufactured by BASF), and 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol (Tinuvin 571, manufactured by BASF). Examples include the "inuvin" series; the "KEMISORB" series of benzotriazole-based drugs manufactured by Chemipro Chemical Co., Ltd., such as KEMISORB71, KEMISORB73, KEMISORB79, and KEMISORB279; and the "Sumisorb" series of benzotriazole-based drugs manufactured by Sumitomo Chemical Co., Ltd., such as 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole (Sumisorb250, manufactured by Sumitomo Chemical Co., Ltd.).

[0118] As the triazine-based ultraviolet absorber, any suitable triazine-based ultraviolet absorber can be used, as long as it does not impair the effects of the present invention. Examples of such triazine-based ultraviolet absorbers include triazine-based ultraviolet absorbers having two or fewer hydroxyl groups in one molecule.

[0119] Examples of triazine-based UV absorbers include BASF's "Tinosorb" series of triazine-based products such as 2,4-bis-[2-hydroxy-4-(2-ethylhexyloxy)phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine (Tinosorb S, manufactured by BASF); 2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (Tinuvin 460 (BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol (Tinuvin 400, BASF), 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-[3-(dodecyloxy)-2-hydroxypropoxy]phenol), reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine and (2-ethylhexyl)-glycidic acid ester (Tinuvin 405, BASF), 2-(4,6-diphenyl Examples include BASF's "Tinuvin" series of triazine-based products such as 2-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol (Tinuvin 1577, manufactured by BASF) and 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine (Tinuvin 479, manufactured by BASF); and ADEKA's "ADEKA Stab" series of triazine-based products such as 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol (ADEKA Stab LA46, manufactured by ADEKA).

[0120] Among triazine-based UV absorbers, those having two hydroxyphenyl structures, such as BASF's "Tinosorb S," are preferred because they can better exhibit the effects of the present invention.

[0121] As the benzophenone-based UV absorber (including oxybenzophenone-based UV absorbers), any suitable benzophenone-based UV absorber can be used, as long as it does not impair the effects of the present invention. Examples of such benzophenone-based UV absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid (anhydrous and trihydrate), 2-hydroxy-4-octyloxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 4-benzyloxy-2-hydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone. Examples of commercially available benzophenone-based UV absorbers include the "KEMISORB" series of benzophenone-based products manufactured by Chemipro Chemical Co., Ltd., such as KEMISORB111.

[0122] As the salicylate ester-based ultraviolet absorber, any suitable salicylate ester-based ultraviolet absorber can be used as long as it does not impair the effects of the present invention. Examples of such salicylate ester-based ultraviolet absorbers include phenyl-2-acryloyloxybenzoate, phenyl-2-acryloyloxy-3-methylbenzoate, phenyl-2-acryloyloxy-4-methylbenzoate, phenyl-2-acryloyloxy-5-methylbenzoate, phenyl-2-acryloyloxy-3-methoxybenzoate, phenyl-2-hydroxybenzoate, phenyl-2-hydroxy-3-methylbenzoate, phenyl-2-hydroxy-4-methylbenzoate, phenyl-2-hydroxy-5-methylbenzoate, phenyl-2-hydroxy-3-methoxybenzoate, and 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate. Examples of commercially available salicylate ester-based UV absorbers include BASF's "Tinuvin" series, such as TINUVIN120.

[0123] As the cyanoacrylate-based ultraviolet absorber, any suitable cyanoacrylate-based ultraviolet absorber can be employed as long as the effects of the present invention are not impaired. Examples of such cyanoacrylate-based ultraviolet absorbers include alkyl-2-cyanoacrylate, cycloalkyl-2-cyanoacrylate, alkoxyalkyl-2-cyanoacrylate, alkenyl-2-cyanoacrylate, and alkynyl-2-cyanoacrylate.

[0124] <A-2-7. Other Components> The urethane-based adhesive composition may contain any suitable other components as long as the effects of the present invention are not impaired. Examples of such other components include solvents, antistatic agents, crosslinking accelerators, silane coupling agents, fatty acid esters, antioxidants, light stabilizers, resin components, tackifiers, crosslinking retarders, inorganic fillers, organic fillers, metal powders, colorants (such as pigments and dyes), chain transfer agents, plasticizers, softeners, anti-aging agents, conductive agents, foils, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, and lubricants. The other components may be only one kind or two or more kinds. The content ratio of the other components in the urethane-based adhesive composition may be set to any appropriate content ratio according to the purpose as long as the effects of the present invention are not impaired.

[0125] ≪A-3. Release Liner≫ The surface protection film of the present invention may include a release liner. As described above, the release liner is usually provided on the surface opposite to the base material of the adhesive layer.

[0126] Examples of the release liner include a release liner in which the surface of a base material (liner base material) such as paper or a plastic film is silicone-treated, and a release liner in which the surface of a base material (liner base material) such as paper or a plastic film is laminated with a polyolefin-based resin.

[0127] Examples of plastic films used as liner substrates include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, and ethylene-vinyl acetate copolymer film.

[0128] The thickness of the release liner is preferably 1 μm to 500 μm, but may also be 3 μm to 450 μm, 5 μm to 400 μm, or 10 μm to 300 μm.

[0129] ≪≪B.Applications≫≫ The surface protection film according to the embodiment of the present invention is typically used in the manufacturing process of optical components and electronic components, by being bonded to the exposed surface of the optical component or electronic component to prevent scratches on the surface during processing, assembly, inspection, transportation, etc., and is suitable for surface protection of optical components and electronic components. The optical component of the present invention includes the surface protection film of the present invention. The electronic component of the present invention includes the surface protection film of the present invention. [Examples]

[0130] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way to these examples. The test and evaluation methods in the examples are as follows. When "parts" is written, it means "parts by weight" unless otherwise specified, and when "%" is written, it means "percent by weight" unless otherwise specified.

[0131] <Transmittance of ultraviolet light at a wavelength of 365nm> The transmittance of 365nm ultraviolet light from the surface protective film after the release liner was removed was measured using a device manufactured by Hitachi High-Tech Corporation, product name "UH-4150".

[0132] <Peel strength against glass plate (I) after being left at 23°C for 30 minutes> A surface protective film (25 mm wide x 140 mm long) with the release liner 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 pass-through motion. The film was then left to stand for 30 minutes at an ambient temperature of 23°C to prepare an evaluation sample. Using the obtained evaluation sample, the peel force (I) against the glass plate after 30 minutes at 23°C was measured using a tensile testing machine. The tensile testing machine used was the "Autograph AG-Xplus HS 6000 mm / min high-speed model (AG-50NX plus)" manufactured by Shimadzu Corporation. After setting the evaluation sample in the tensile testing machine, the tensile test was started. The tensile test conditions were: temperature 23°C, peel angle = 180 degrees, peel speed (tensile speed) = 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 peel force (I) against the glass plate after 30 minutes at 23°C.

[0133] <Peel strength against glass plate (II) after being left at 50°C for one day> A surface protective film (25 mm wide x 140 mm long) with the release liner 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 pass-through. The sample was then left for one day at an ambient temperature of 50°C to prepare an evaluation sample. Using the obtained evaluation sample, the peel force (II) against the glass plate after being left at 50°C for one day was measured using a tensile testing machine. The tensile testing machine used was the "Autograph AG-Xplus HS 6000 mm / min high-speed model (AG-50NX plus)" manufactured by Shimadzu Corporation. After setting the evaluation sample in the tensile testing machine, the tensile test was started. The tensile test conditions were: temperature 23°C, peel angle = 180 degrees, peel speed (tensile speed) = 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 peel force (II) against the glass plate after the surface protective film had been left at 50°C for one day.

[0134] <Percentage increase in peeling force over time> The rate of increase in peeling force over time from peeling force against the glass plate (I) to the above-mentioned peeling force against the glass plate (II) was calculated using the following formula. Rate of increase in peeling force over time (%) = (Peeling force against glass plate (II) / Peeling force against glass plate (I)) × 100 (%)

[0135] <Residual adhesion rate to glass plate> A surface protection film, with the release liner removed, was applied to a glass plate (soda-lime glass, manufactured by Matsunami Glass Industry Co., Ltd.) using a 2kg hand roller in one pass-through motion. After being left at 23°C for 24 hours, the surface protection film was peeled off using a tensile testing machine (Shimadzu Corporation, product name "Autograph AG-Xplus HS 6000mm / min high-speed model (AG-50NX plus)") under the conditions of peel angle = 180 degrees and peel speed (tensile speed) = 300mm / min. Subsequently, a 19mm wide No.31B tape (manufactured by Nitto Denko Corporation, base material thickness = 25μm, total thickness = 53μm), cut to a length of 150mm, was applied to the peeled surface of the glass plate at 23°C using a 2kg hand roller in one pass-through motion. After being left at 23°C for 30 minutes, the material was peeled using a tensile testing machine (Shimadzu Corporation's "Autograph AG-Xplus HS 6000mm / min high-speed model (AG-50NX plus)") at a temperature of 23°C, a peeling angle of 180 degrees, and a tensile speed of 300mm / min, and the peeling force (A) was measured. Separately, adhesive tape (product name "No.31B", manufactured by Nitto Denko Corporation, base material thickness = 25 μm, total thickness = 53 μm) was applied to a glass plate that had not undergone the above-mentioned bonding and peeling of surface protective film. After being left at a temperature of 23°C for 30 minutes, the peeling force (B) was measured when the tape was peeled off at a peeling angle of 180 degrees and a peeling speed of 300 mm / min. The residual adhesion rate to the glass plate was calculated using the following formula. Residual adhesion rate to glass plate (%) = (Peel strength (A) / Peel strength (B)) × 100 (%)

[0136] <Evaluation of cutter glue residue> A 1cm cut was made by inserting a cutter blade at a 90-degree angle into the center of the adhesive layer side of a surface protective film (25mm wide x 140mm long) from which the release liner had been peeled off. The following criteria were used for evaluation. ○: No adhesive residue could be visually confirmed to have fallen off. △: Glue residue detachment was confirmed.

[0137] <Compatibility evaluation of UV absorbers> The surface protective film, with the release liner attached, was stored at a temperature of 20°C and a relative humidity of 98%, and the precipitation of crystals from the adhesive layer was observed. ○: No crystals had precipitated after 240 hours. △: Crystals precipitated within 240 hours.

[0138] <Light stripping agents used in the examples and comparative examples> • EFS-132: Product name "MEGAFACE EFS-132" manufactured by DIC Corporation (a silicone compound having a skeleton derived from methyl methacrylate (a monomer whose corresponding homopolymer has a Tg of 80°C or higher)). • KH-10: Product name "Aqualon KH-10" (polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. • F-571: Product name "Megafac F-571" manufactured by DIC Corporation (Oligomer containing fluorine groups, hydrophilic groups, and lipophilic groups)

[0139] <UV absorbers used in the examples and comparative examples> • Tinuvin99-2: Benzotriazole (BTZ) UV absorber manufactured by BASF • Tinuvin384-2: Benzotriazole (BTZ) UV absorber manufactured by BASF • Tinuvin928: A benzotriazole (BTZ) UV absorber manufactured by BASF. • KEMISORB73: Benzotriazole (BTZ) UV absorber manufactured by Chemipro Chemical Co., Ltd. • Tinuvin400: A triazine-based UV absorber manufactured by BASF. Tinosorb S: A triazine-based UV absorber manufactured by BASF. • KEMISORB111: Benzophenone-based UV absorber manufactured by Chemipro Chemical Co., Ltd.

[0140] [Manufacturing Example 1]: Manufacturing of urethane prepolymer In a polymerization apparatus equipped with a 1L round-bottom separable flask, separable cover, separatory funnel, thermometer, nitrogen inlet tube, Liebig condenser, vacuum seal, stirring rod, and stirring blade, 197g of polypropylene glycol (product name "Sannix PP-2000", manufactured by Sanyo Chemical Industries, Ltd.), 197g of polyester polyol (product name "Kuraray Polyol P-2010", manufactured by Kuraray Co., Ltd.), 110g of toluene (manufactured by Tosoh Corporation) as a solvent, and 0.041g of dibutyltin(IV) dilaurate (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst were added, and nitrogen purging was carried out at room temperature for 1 hour while stirring. Subsequently, under nitrogen inflow and while stirring, 33.5 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and the solution temperature in the experimental apparatus was controlled to 90±2°C using a water bath and held for 4 hours. Then, 44 g of polypropylene glycol (product name "GP1000", manufactured by Sanyo Chemical Industries, Ltd.) was added, and the solution temperature in the experimental apparatus was controlled to 90±2°C using a water bath and held for 2 hours. Then, 25.4 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and the solution temperature in the experimental apparatus was controlled to 90±2°C using a water bath and held for 2 hours to obtain a solution of urethane prepolymer A. During polymerization, toluene was added dropwise as needed to control the temperature during polymerization and to prevent a decrease in stirability due to viscosity increase. The total amount of toluene added dropwise was 380 g. The solid content concentration of the urethane prepolymer A solution was 50% by weight. Furthermore, the number-average molecular weight (Mn) of urethane prepolymer A was 250,000.

[0141] [Example 1] A urethane-based adhesive composition was obtained by diluting 100 parts by weight of urethane prepolymer A, 7.0 parts by weight of a polyfunctional isocyanate compound (Coronate HX:C / HX, manufactured by Nippon Polyurethane Co., Ltd.) as a crosslinking agent, 0.40 parts by weight of a silicone compound (MEGAFACE EFS-132, manufactured by DIC Corporation) having a skeleton derived from methyl methacrylate (a monomer of which the corresponding homopolymer has a Tg of 80°C or higher) as a light release agent, 0.5 parts by weight of "Irganox 1010" (manufactured by BASF) as an antioxidant, and 1.00 part by weight of "Tinuvin 400" (manufactured by BASF) as an ultraviolet absorber with ethyl acetate so that the total solid content was 50% by weight. The obtained urethane-based adhesive composition was applied to a PET film (product name "T100-75S", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) to a dry thickness of 75 μm. The film was cured and dried at a drying temperature of 130°C for 3 minutes to produce an adhesive layer composed of urethane-based adhesive. Next, the silicone-treated side of a release liner made of polyester resin with a thickness of 25 μm (product name "MRF25", thickness 25 μm, manufactured by Mitsubishi Chemical Corporation), which had one side treated with silicone, was laminated to the surface of the obtained adhesive layer to obtain a surface protection film (1). The film was aged at room temperature for 5 days and evaluated. The results are shown in Table 1.

[0142] [Examples 2-29] Surface protective films (2) to (29) were obtained in the same manner as in Example 1, except that the amount of the polyfunctional isocyanate compound, the type and amount of the light release agent, and the type and amount of the ultraviolet absorber were changed as shown in Table 1. The films were aged at room temperature for 5 days and evaluated. The results are shown in Table 1.

[0143] [Comparative Example 1] A surface protective film (C1) was obtained in the same manner as in Example 1, except that an ultraviolet absorber was not used. The film was aged at room temperature for 5 days and then evaluated. The results are shown in Table 1.

[0144] [Comparative Example 2] A surface protective film (C2) was obtained in the same manner as in Example 1, except that the amount of UV absorber was changed to 0.40 parts by weight. The film was aged at room temperature for 5 days and evaluated. The results are shown in Table 1.

[0145] [Table 1]

[0146] [Examples 30-58] For each of the surface protective films (1) to (29) obtained in Examples 1 to 29, the release liner was peeled off, and the adhesive layer side was attached to a polarizing plate (manufactured by Nitto Denko Corporation, product name "TEG1465DUHC"), which is an optical component, to obtain an optical component with the surface protective film attached.

[0147] [Examples 59-87] For each of the surface protective films (1) to (29) obtained in Examples 1 to 29, the release liner was peeled off, and the adhesive layer side was attached to a conductive film (manufactured by Nitto Denko Corporation, product name "Elecrista V270L-TFMP") which is an electronic component, to obtain an electronic component with the surface protective film attached. [Industrial applicability]

[0148] The surface protection film of the present invention can be used in any suitable application. Preferably, the surface protection film of the present invention is used in the fields of optical components and electronic components. [Explanation of Symbols]

[0149] 1 Base material 2. Adhesive layer 3. Peel-off liner 10 Surface protective film

Claims

1. A surface protective film comprising a substrate and an adhesive layer, The adhesive layer is composed of a urethane-based adhesive. The urethane-based adhesive is formed from a urethane-based adhesive composition, The urethane adhesive composition comprises a base polymer (A), a polyfunctional isocyanate compound (B), a light release agent (C), and an ultraviolet absorber (D). The base polymer (A) contains a urethane prepolymer, The amount of the ultraviolet absorber (D) in the urethane adhesive composition is 0.50 parts by weight or more per 100 parts by weight of the base polymer (A). Surface protective film.

2. The surface protective film according to claim 1, wherein the amount of the ultraviolet absorber (D) in the urethane adhesive composition is 1.00 part by weight or more per 100 parts by weight of the base polymer (A).

3. The surface protective film according to claim 1, wherein the amount of the ultraviolet absorber (D) in the urethane adhesive composition is 6.00 parts by weight or less per 100 parts by weight of the base polymer (A).

4. The surface protective film according to claim 1, wherein the ultraviolet absorber (D) is at least one selected from the group consisting of benzotriazole-based ultraviolet absorbers and triazine-based ultraviolet absorbers.

5. The surface protective film according to claim 1, wherein the equivalent ratio ([NCO] / [OH]) of the NCO group of the polyfunctional isocyanate compound (B) to the OH group of the base polymer (A) is 1.00 or more.

6. The surface protective film according to claim 1, wherein the equivalent ratio ([NCO] / [OH]) of the NCO group of the polyfunctional isocyanate compound (B) to the OH group of the base polymer (A) is 4.60 or less.

7. The surface protective film according to claim 1, wherein the content of the light release agent (C) in the urethane adhesive composition is 0.20 parts by weight or more per 100 parts by weight of the base polymer (A).

8. The surface protective film according to claim 1, wherein the content of the light release agent (C) in the urethane adhesive composition is 0.70 parts by weight or less per 100 parts by weight of the base polymer (A).

9. An optical component comprising a surface protective film according to any one of claims 1 to 8.

10. An electronic component comprising a surface protective film according to any one of claims 1 to 8.

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