Surface protective film

Abstract

The present invention provides a surface protection film that exhibits excellent curl suppression ability, and preferably, further exhibits excellent easy peelability and excellent low-contamination 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), and a light release agent (C), the base polymer (A) comprises a urethane prepolymer, and the low-speed shear force against a glass plate at a peeling speed of 3 mm / min after being left at a temperature of 23°C for 30 minutes is 1000 gf / 100 mm 2 The following applies:

Description

[Technical Field]

[0001] This invention relates to a surface protective film. [Background technology]

[0002] In the manufacturing process of optical and electronic components, a surface protection film having a base material and an adhesive layer is generally attached to the exposed surface of the optical or electronic component to prevent damage to its surface during processing, assembly, inspection, and transportation. Such a surface protection film is peeled off from the optical or electronic component when surface protection is no longer needed (Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 6613516 [Overview of the project] [Problems that the invention aims to solve]

[0004] When bonding a surface protective film to an object such as an optical or electronic component, bonding tension is sometimes applied to the surface protective film to suppress bubbles, wrinkles, etc. Typically, the surface protective film is stretched and fixed so that a certain tension is applied to it, and then bonded to the object, and after bonding, the stretching and fixing are released.

[0005] However, as described above, if the surface protective film is stretched and fixed to the substrate so that a certain tension is applied to it, and then the stretching and fixing is released, the surface protective film will shrink due to the residual stress from the tension that was applied to it, causing curling to occur in the substrate to which the surface protective film is attached.

[0006] The object of the present invention is to provide a surface protection film that exhibits excellent curl suppression ability, and preferably, further exhibits excellent easy peelability and excellent low-contamination properties. Another object of the present invention is to provide optical components and electronic components that include such a surface protection film. [Means for solving the problem]

[0007] To solve the above problems, the inventors conducted thorough research. They discovered that the degree to which the surface protective film shrinks due to residual stress from the tension applied to the surface protective film during bonding can be appropriately reflected by a very slow shear force applied to the glass plate. They then conceived that the above problems could be solved by controlling such a slow shear force applied to the glass plate to a predetermined magnitude, and thus completed the present invention.

[0008] [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), and a light release agent (C). The base polymer (A) contains a urethane prepolymer, The low-speed shear force against the glass plate at a peeling speed of 3 mm / min after being left at 23°C for 30 minutes was 1000 gf / 100 mm. 2 The following applies: [2] In the surface protective film described in [1] 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 2.00 or more. [3] In the surface protective film described in [1] or [2] 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. [4] In the surface protective film described in any of [1] to [3] above, the light release agent (C) may be at least one selected from the group consisting of silicone compounds and fluorine compounds. [5] In the surface protective film described in any of [1] to [4] 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). [6] In the surface protective film described in any of [1] to [5] above, the content of the light release agent (C) in the urethane adhesive composition may be less than 0.60 parts by weight per 100 parts by weight of the base polymer (A). [7] In the surface protective film described in any of [1] to [6] above, the base polymer (A) may contain a low molecular weight polyol. [8] An optical component according to an embodiment of the present invention includes a surface protective film as described in any of [1] to [7] above. [9] An electronic component according to an embodiment of the present invention includes a surface protective film as described in any of [1] to [7] above. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a surface protective film that exhibits excellent curl suppression ability, and preferably, further exhibits excellent easy peelability and excellent low-contamination 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]

[0010] [Figure 1] This is a schematic cross-sectional view of a surface protective film according to one embodiment of the present invention. [Figure 2] This is a schematic diagram illustrating the preparation of evaluation samples for Carl's evaluation. [Modes for carrying out the invention]

[0011] When the term "weight" is used in this specification, it may be read as "mass", which is the SI unit customarily used to indicate weight.

[0012] When the term "(meth)acryl" is used in this specification, it means "acryl and / or methacryl"; when the term "(meth)acrylate" is used, it means "acrylate and / or methacrylate"; when the term "(meth)allyl" is used, it means "allyl and / or methallyl"; when the term "(meth)acrolein" is used, it means "acrolein and / or methacrolein".

[0013] ≪≪A. Surface Protection Film≫≫ The surface protection film according to an embodiment of the present invention includes a base material and an adhesive layer. As long as the surface protection film according to an embodiment of the present invention includes a base material and an adhesive layer, it may include any other appropriate member (any other appropriate layer, etc.) within a range that does not impair the effects of the present invention.

[0014] One embodiment of the surface protection film of the present invention consists of a base material, 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 base material. Another embodiment of the surface protection film of the present invention consists of a base material and an adhesive layer.

[0015] FIG. 1 is a schematic cross-sectional view of a surface protection film according to an embodiment of the present invention. In FIG. 1, the surface protection film 10 includes a base material 1, an adhesive layer 2, and a release liner 3. In FIG. 1, the base material 1, the adhesive layer 2, and the release liner 3 are directly laminated.

[0016] The thickness of the surface protection film according to an embodiment of the present invention can adopt any appropriate thickness within a range that does not impair the effects of the present invention. The thickness of the surface protection film according to an embodiment of the present invention is preferably 5 μm to 5OO μm, and may be 10 μm to 450 μm, may be 15 μm to 400 μm, or may be 20 μm to 300 μm.

[0017] The surface protection film according to an embodiment of the present invention has a low-speed shear force against a glass plate at a peeling speed of 3 mm / min after being left at a temperature of 23°C for 30 minutes, typically 1000 gf / 100 mm 2 or less, 900 gf / 100 mm 2 or less may also be acceptable, 800 gf / 100 mm 2 or less may also be acceptable, 700 gf / 100 mm 2 or less may also be acceptable, 650 gf / 100 mm 2 or less may also be acceptable, 600 gf / 100 mm 2 or less may also be acceptable. The low-speed shear force at a very slow speed against the adherend reflects the degree of slow sliding in the shear direction over time at the interface between the adherend and the adhesive layer of the surface protection film. Such slow sliding over time is presumed to be an appropriate indicator showing the degree of curl of the surface protection film. By controlling the low-speed shear force against the glass plate within the above range, the surface protection film according to an embodiment of the present invention can effectively exhibit excellent curl suppression ability. The lower limit of the low-speed shear force against the glass plate is, from the viewpoint of suppressing the lifting of the surface protection film against the adherend, for example, 100 gf / 100 mm 2 or more, 250 gf / 100 mm 2 or more may also be acceptable, 400 gf / 100 mm 2 or more may also be acceptable.

[0018] The low-speed shear force against the glass plate is the shear force 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 peeled from the surface of the glass plate at a peeling angle of 180 degrees and a peeling speed of 3 mm / min at a temperature of 23°C. A more detailed measurement method will be described later.

[0019] The surface protective film according to the embodiment of the present invention has a peel force (I) against the glass plate after being left at a temperature of 23°C for 30 minutes, preferably 30.0 gf / 25 mm or less, but may also be 10.0 gf / 25 mm or less, 5.00 gf / 25 mm or less, 3.00 gf / 25 mm or less, 2.00 gf / 25 mm or less, 1.70 gf / 25 mm or less, 1.50 gf / 25 mm or less, 1.20 gf / 25 mm or less, 1.10 gf / 25 mm or less, or 1.00 gf / 25 mm or less. As long as the above peel force (I) against the glass plate is within the above range, the surface protective film according to the embodiment of the present invention can exhibit excellent easy peelability. To prevent unintended delamination during the manufacturing process, etc., the lower limit of the above-mentioned delamination force (I) against the glass plate is, for example, 0.10 gf / 25 mm or more, and may also be 0.50 gf / 25 mm or more.

[0020] The above peeling force (I) against the glass plate is the peeling force obtained when the adhesive layer contained in the surface protective film is bonded to the surface of the glass plate, left at a temperature of 23°C for 30 minutes, and then peeled off 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.

[0021] The surface protective film according to the embodiment of the present invention has a peel force (II) against the glass plate after being left at a temperature of 50°C for one day, preferably 30.0 gf / 25 mm or less, but may be 10.0 gf / 25 mm or less, 7.00 gf / 25 mm or less, 5.00 gf / 25 mm or less, 4.00 gf / 25 mm or less, 3.00 gf / 25 mm or less, 2.50 gf / 25 mm or less, 2.00 gf / 25 mm or less, or 1.50 gf / 25 mm or less. As long as the above peel force (II) against the glass plate is within the above range, the surface protective film according to the embodiment of the present invention can suppress the deterioration of light peelability over time. In order to prevent unintended peeling in the manufacturing process, etc., the lower limit of the above peel force (II) against the glass plate may be, for example, 0.10 gf / 25 mm or more, or 0.50 gf / 25 mm or more.

[0022] The above peeling force against the glass plate (II) is the peeling force obtained when the adhesive layer contained in the surface protective film is bonded to the surface of the glass plate, left at a temperature of 50°C for one day, and then peeled off at a temperature of 23°C at a peeling angle of 180 degrees and a peeling speed of 300 mm / min. A more detailed measurement method will be described later.

[0023] The surface protective film according to the embodiment of the present invention has a peeling force over time increase rate from the peeling force against the glass plate (I) to the peeling force against the glass plate (II) (peeling force over time increase rate (%) = (peeling force against the glass plate (II) / peeling force against the glass plate (I)) × 100 (%)) which is preferably 250% or less, but may be 220% or less, 200% or less, 180% or less, 160% or less, 140% or less, 130% or less, 120% or less, or 115% or less. If the peeling force over time increase rate is within the above range, the surface protective film according to the embodiment of the present invention can further suppress the decrease in light peelability over time. The lower limit of the peeling force over time increase rate is preferably as small as possible, for example, 100% or more.

[0024] 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, 94% 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.

[0025] 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.

[0026] The surface protective film according to the embodiment of the present invention preferably has a haze of 50% or less, but may also be 30% or less, 20% or less, 10% or less, 5% or less, 3% or less, 2.5% or less, or 2% or less, from the viewpoint of inspectability and the like.

[0027] 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.

[0028] ≪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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] ≪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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] In embodiments of the present invention, the urethane adhesive composition comprises a base polymer (A), a polyfunctional isocyanate compound (B), and a light release agent (C).

[0043] The base polymer (A) contains a urethane prepolymer. The urethane prepolymer may be one type or two or more types.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] The base polymer (A) may contain any other suitable base polymer, as long as it does not impair the effects of the present invention.

[0049] 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.

[0050] <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.

[0051] The urethane prepolymer may be of one type or two or more types.

[0052] The urethane prepolymer is preferably a polyurethane polyol, and more preferably obtained by reacting a polyol with a polyfunctional isocyanate compound.

[0053] The number-average molecular weight (Mn) of urethane prepolymers is, for example, between 3,000 and 1,000,000.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] Polyether polyols can be used with molecular weights 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] To obtain a urethane prepolymer, the polyfunctional isocyanate compound reacted with the polyol may be one type or two or more types.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] Examples of tertiary amine catalysts include triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7(DBU).

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] Any suitable solvent can be used when preparing the urethane prepolymer. Examples of such solvents include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] Examples of the light stabilizer include, for example, hindered amine light stabilizers.

[0085] <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, may be 1300 or less, may be 1200 or less, may be 1100 or less, or may be 1000 or less. The lower limit of the number average molecular weight Mn of the low molecular weight polyol is preferably 50 or more, may be 100 or more, may be 150 or more, may be 200 or more, or may be 250 or more.

[0086] 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.

[0087] 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.), dihydroxybenzenes (such as catechol, resorcinol, hydroquinone, etc.) as initiators. Specifically, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxypropylene glyceryl ether, etc. are included.

[0088] The number of OH groups in the low molecular weight polyol is preferably from 2 to 6, more preferably from 3 to 5, still more preferably from 3 to 4, and particularly preferably 3.

[0089] <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.

[0090] The polyfunctional isocyanate compound (B) may be only one kind or two or more kinds.

[0091] 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.

[0092] 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) is such that the lower limit 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.

[0093] 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) preferably has an upper limit of 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 light peelability. If the upper limit of the equivalent ratio ([NCO] / [OH]) is too large, there is a risk of generating paste residues from the adhesive layer.

[0094] 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) preferably ranges from 0.50 to 5.00, and may be from 1.00 to 4.80, from 1.00 to 4.70, from 1.00 to 4.60, from 1.50 to 4.60, from 2.00 to 4.60, from 2.50 to 4.60, from 3.00 to 4.60, from 3.10 to 4.60, from 3.20 to 4.60, from 3.30 to 4.50, from 3.40 to 4.40, from 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 light peelability. If the equivalent ratio ([NCO] / [OH]) is too small, there is a risk of deterioration of light peelability, for example, there is a risk of deterioration of light peelability over time. If the equivalent ratio ([NCO] / [OH]) is too large, there is a risk of generating paste residues from the adhesive layer.

[0095] <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 appropriate catalyst can be used as long as it does not impair the effects of the present invention. Examples of such a catalyst include the catalysts that can be used in the preparation of the urethane prepolymer described above.

[0096] When using a catalyst 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 to 1.0 parts by weight, may be 0.001 to 1.0 parts by weight, may be 0.003 to 1.0 parts by weight, or may be 0.005 to 1.0 parts by weight based on 100 parts by weight of the base polymer (A).

[0097] <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.

[0098] The content of the light release agent (C) in the urethane-based adhesive composition, based on 100 parts by weight of the base polymer (A), preferably has a lower limit of 0.01 parts by weight or more, may be 0.10 parts by weight or more, may be 0.20 parts by weight or more, may be 0.25 parts by weight or more, or may be 0.30 parts by weight or more. If the lower limit of 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 properties and excellent low contamination properties. If the content of the light release agent (C) is too small, there is a possibility that excellent light release properties cannot be exhibited.

[0099] The content of the light release agent (C) in the urethane adhesive composition is preferably 1.00 part by weight or less per 100 parts by weight of the base polymer (A), but may be 0.80 parts by weight or less, 0.70 parts by weight or less, 0.60 parts by weight or less, less than 0.60 parts by weight, 0.55 parts by weight or less, or 0.50 parts by weight or less. As long as the upper limit of the content of the light release agent (C) is within the above range, the surface protective film according to the embodiment of the present invention can exhibit excellent light release properties and excellent low-stain properties. If the content of the light release agent (C) is too high, it may not be possible to exhibit excellent low-stain properties.

[0100] The content of the light release agent (C) in the urethane adhesive composition is preferably 0.01 to 1.00 parts by weight, 0.10 to 0.80 parts by weight, 0.20 to 0.70 parts by weight, 0.25 to 0.60 parts by weight, 0.25 to 0.60 parts by weight, 0.25 to 0.60 parts by weight or more and less than 0.60 parts by weight, 0.30 to 0.55 parts by weight, or 0.30 to 0.50 parts by weight, per 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 protective film according to the embodiment of the present invention can exhibit excellent light release properties and excellent low-stain properties. If the content of the light release agent (C) is too low, excellent light release properties may not be exhibited. If the content of the light release agent (C) is too high, excellent low-stain properties may not be exhibited.

[0101] 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.

[0102] From the viewpoint of providing both excellent peelability and superior low-stain properties to the surface protective film according to the embodiments of the present invention, it is preferably at least one selected from the group consisting of silicone compounds and fluorine compounds.

[0103] 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.

[0104] Preferably, the silicone compound is a silicone compound (C1) having a skeleton derived from monomer (a) whose corresponding homopolymer has a Tg (glass transition temperature) of 80°C or higher.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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).

[0109] 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.

[0110] 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.

[0111] 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.

[0112] One preferred embodiment of the silicone compound (C1) has a skeleton derived from monomer (a) whose corresponding homopolymer has a Tg (glass transition temperature) of 80°C or higher, and further has a skeleton derived from monomer (b) whose corresponding homopolymer has a Tg of 60°C or higher and less than 80°C. Another preferred embodiment of the silicone compound (C1) has a skeleton derived from monomer (a) whose corresponding homopolymer has a Tg (glass transition temperature) of 80°C or higher, and further has an alkylene oxide structure. Yet another preferred embodiment of the silicone compound (C1) has a skeleton derived from monomer (a) whose corresponding homopolymer has a Tg (glass transition temperature) of 80°C or higher, and further has a skeleton derived from monomer (b) whose corresponding homopolymer has a Tg of 60°C or higher and less than 80°C, and further has an alkylene oxide structure.

[0113] 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.

[0114] As the fluorine-based compound, any appropriate fluorine-based compound can be adopted as long as it functions as a light release agent that can exhibit light release properties when contained in the adhesive, without impairing the effects of the present invention. Examples of such fluorine-based compounds include the fluorine-based compounds described in JP-A-2024-84496.

[0115] As the surfactant, any appropriate surfactant can be adopted as long as it functions as a light release agent that can exhibit light release properties when contained in the adhesive, without impairing the effects of the present invention. Examples of such surfactants include the surfactants described in JP-A-2024-111800.

[0116] <A-2-6. Other Components> The urethane-based adhesive composition may contain any appropriate other components as long as the effects of the present invention are not impaired. Examples of such other components include solvents, antistatic agents, crosslinking accelerators, silane coupling agents, fatty acid esters, antioxidants, ultraviolet absorbers, 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.

[0117] ≪A-3. Release Liner≫ The surface protection film of the present invention may contain a release liner. As described above, the release liner is usually provided on the surface opposite to the base material of the adhesive layer.

[0118] Examples of release liners include release liners in which the surface of a substrate (liner substrate) such as paper or plastic film is treated with silicone, and release liners in which the surface of a substrate (liner substrate) such as paper or plastic film is laminated with a polyolefin resin.

[0119] 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.

[0120] 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.

[0121] ≪≪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]

[0122] 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.

[0123] <Low-speed shear force against glass plate at a peeling speed of 3 mm / min after being left at 23°C for 30 minutes> A 10mm x 10mm portion of the surface protective film (10mm wide x 50mm long), from which the release liner had been peeled off, was attached to a glass plate (soda-lime glass, manufactured by Matsunami Glass Industry Co., Ltd.) using a 2kg hand roller in one pass-and-back motion. The sample 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 low-speed shear force against the glass plate was measured using a tensile testing machine at a peeling speed of 3mm / min after being left at 23°C for 30 minutes. The tensile testing machine used was the "Autograph AG-Xplus HS 6000mm / 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: peel angle = 180 degrees, peel speed (tensile speed) = 3 mm / min. The load when peeling the surface protective film from the glass plate was measured, and the maximum load at that time was defined as the low-speed shear force against the glass plate at a peel speed of 3 mm / min after leaving the surface protective film at a temperature of 23°C for 30 minutes.

[0124] <Carl's rating> As shown in Figure 2, the surface protection film (50 mm wide x 200 mm long) 10, from which the release liner had been peeled off, was fixed at both ends in the longitudinal direction using a manual stretching machine (manufactured by Imoto Seisakusho, product name "Manual Uniaxial Stretching Machine") and stretched by 1% (2 mm) in direction A in Figure 2 (i.e., the longitudinal length was 202 mm). The adhesive layer side of the surface protection film was then bonded to a PET film (manufactured by Mitsubishi Chemical Corporation, product name "Dia Foil T100-75S", thickness = 75 μm) (cut to 50 mm wide x 100 mm long) 20, with the longitudinal direction aligned and the midpoints of the longitudinal direction coinciding, to obtain a laminate 30 of the stretched and fixed surface protection film and the adherend 20. Subsequently, the stretching fixation was released, and the laminate 40 of the surface protective film and the adherend 20, from which the stretching fixation had been released, was cut to a length of 80 mm in total, 40 mm in both directions from the middle in the longitudinal direction, to obtain an evaluation sample 50 with a width of 50 mm and a length of 80 mm. A curl evaluation was performed on the 50 evaluation samples that were prepared. Specifically, the evaluation sample 50 was placed on a smooth glass plate with the adherend 20 side facing downwards, and the height (mm) of each corner (4 corners) of the evaluation sample 50 that was lifted from the glass plate was measured, and the average value was calculated.

[0125] <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.

[0126] <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.

[0127] <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 (%)

[0128] <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 (%)

[0129] <Hayes's rating> Using a haze measuring instrument (Haze Meter HM-150N, manufactured by Murakami Color Technology Laboratory), the sample was set up so that light entered from the substrate side of the surface protective film after the release liner had been peeled off, and the haze (%) in all light rays was measured.

[0130] <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.

[0131] <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)

[0132] [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.

[0133] [Example 1] A urethane-based adhesive composition was obtained by diluting 100 parts by weight of urethane prepolymer A, 3.0 parts by weight of a polyfunctional isocyanate compound (Coronate HX:C / HX, manufactured by Nippon Polyurethane 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, and 0.5 parts by weight of "Irganox 1010" (manufactured by BASF) as an antioxidant 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.

[0134] [Examples 2-11] Surface protective films (2) to (11) were obtained in the same manner as in Example 1, except that the amount of the polyfunctional isocyanate compound and the type and amount of the light release agent 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.

[0135] [Example 12] A urethane-based adhesive composition was obtained by diluting 100 parts by weight of urethane prepolymer A, 3.0 parts by weight of a polyfunctional isocyanate compound (Coronate HX:C / HX, manufactured by Nippon Polyurethane 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 4.0 parts by weight of a low molecular weight polyol (trade name "Sannix GP250", number average molecular weight Mn=250, manufactured by Sanyo Chemical Industries, Ltd.) 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 (12). The film was aged at room temperature for 5 days and evaluated. The results are shown in Table 1.

[0136] [Comparative Example 1] A surface protective film (C1) was obtained in the same manner as in Example 1, except that the amount of the polyfunctional isocyanate compound was changed to 2.0 parts by weight. The film was aged at room temperature for 5 days and evaluated. The results are shown in Table 1.

[0137] [Table 1]

[0138] [Examples 13-24] For each of the surface protective films (1) to (12) obtained in Examples 1 to 12, 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.

[0139] [Examples 25-36] For each of the surface protective films (1) to (12) obtained in Examples 1 to 12, 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]

[0140] 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]

[0141] 1 Base material 2. Adhesive layer 3. Peel-off liner 10 Surface protective film 20. Adhesion material (PET film) 30 Laminate of stretched and fixed surface protective film and adherend 40 Laminate of surface protective film and adherend after stretching and fixing has been released. 50 evaluation samples A Stretching direction

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), and a light release agent (C). The base polymer (A) contains a urethane prepolymer, After being left at 23°C for 30 minutes, the low-speed shear force against the glass plate at a peeling speed of 3 mm / min was 1000 gf / 100 mm. 2 The following is: Surface protective film.

2. 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 2.00 or more.

3. 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.

4. The surface protective film according to claim 1, wherein the light release agent (C) is at least one selected from the group consisting of silicone compounds and fluorine compounds.

5. 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).

6. The surface protective film according to claim 1, wherein the content of the light release agent (C) in the urethane adhesive composition is less than 0.60 parts by weight per 100 parts by weight of the base polymer (A).

7. The surface protective film according to claim 1, wherein the base polymer (A) comprises a low molecular weight polyol.

8. An optical component comprising a surface protective film according to any one of claims 1 to 7.

9. An electronic component comprising a surface protective film according to any one of claims 1 to 7.

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