Surface protective film

Abstract

The present invention provides a surface protection film that exhibits stable peelability even with fluctuations in time, temperature, and humidity from application to peeling, and that also reduces contamination of the adherend. The present invention also provides optical devices and electronic devices that include such a surface protection film. [Solution] The surface protective film according to an embodiment of the present invention is a surface protective film having a substrate and an adhesive layer, wherein the adhesive layer is composed of an acrylic adhesive, the acrylic adhesive is formed from an acrylic adhesive composition, and the acrylic adhesive composition contains an acrylic polymer and a surfactant (A). Here, the surfactant (A) has (1) no aromatic ring and (2) -(CH2CH2O) n It has a polyethylene oxide skeleton represented by -(where 5≦n<20).

Description

[Technical Field]

[0001] This invention relates to a surface protection film. It also relates to optical devices and electronic devices incorporating such a surface protection film. [Background technology]

[0002] In the manufacturing process of optical and electronic devices, surface protection films are generally applied to the exposed surfaces of optical and electronic components to prevent damage to their surfaces during processing, assembly, inspection, and transportation. Such surface protection films are removed from the optical and electronic components when surface protection is no longer needed (Patent Document 1).

[0003] Such surface protection films require excellent peelability in order to smoothly peel off only at the interface between the surface protection film and optical or electronic components, and to avoid damaging expensive and easily damaged optical or electronic components during peeling. One way to provide such excellent peelability is to add a light peeling agent, for example, a silicone compound such as polyorganosiloxane (Patent Document 2) is used.

[0004] On the other hand, in the case of such surface protection films, when they are attached to an object such as an optical component or an electronic component, components of the adhesive layer may migrate to the surface of the object. For example, additives such as light release agents that may be contained in the adhesive layer may segregate towards the object side of the adhesive layer, and when the surface protection film is peeled off the object, these additives may migrate to the surface of the object, thereby contaminating the surface of the object. If the surface of the object is contaminated in this way, problems such as peeling may occur when another component is attached to the contaminated surface of the object. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 6613516 [Patent Document 2] Patent No. 7058815 [Overview of the project] [Problems that the invention aims to solve]

[0006] Our research has revealed that the peelability of surface protective films is prone to instability due to fluctuations in time between application and removal, as well as temperature and humidity. When the peelability of surface protective films is unstable due to fluctuations in time between application and removal, as well as temperature and humidity, problems arise, such as the inability to achieve stable peelability throughout the manufacturing process of optical devices and electronic devices.

[0007] The object of the present invention is to provide a surface protection film that can exhibit stable peelability even with fluctuations in time from application to peeling, temperature, and humidity, and can also reduce contamination of the adherend, and to provide optical devices and electronic devices that include such a surface protection film. [Means for solving the problem]

[0008] The inventors diligently conducted research to solve the above problems. As a result, they focused on the surfactant to be included in the acrylic adhesive composition that forms the acrylic adhesive, and after continuing to investigate various surfactants, they found that by selecting and adopting a specific surfactant (A), the above problems could be successfully solved, thus completing the present invention.

[0009] [1] The surface protective film according to an embodiment of the present invention is A surface protective film having a base material and an adhesive layer, The adhesive layer is composed of an acrylic adhesive, and the acrylic adhesive is formed from an acrylic adhesive composition. The acrylic adhesive composition comprises an acrylic polymer and a surfactant (A). Here, surfactant (A) is (1) It does not have an aromatic ring, (2)-(CH2CH2O) n - (However, it has a polyethylene oxide skeleton represented by 5 ≦ n < 20). [2] In the surface protection film according to [1] above, the amount of the surfactant (A) with respect to 100 parts by weight of the acrylic polymer may be 0.001 part by weight to 10 parts by weight. [3] The optical device according to an embodiment of the present invention includes the surface protection film according to [1] or [2] above. [4] The electronic device according to an embodiment of the present invention includes the surface protection film according to [1] or [2] above. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a surface protection film that can exhibit stable peelability even due to variations in time, temperature, and humidity from pasting to peeling, and can also reduce the contamination of the adherend. According to the present invention, it is also possible to provide an optical device and an electronic device including such a surface protection film. [Brief Description of the Drawings]

[0011] [Figure 1] It is a schematic cross-sectional view of an adhesive film according to one embodiment of the present invention. [Modes for Carrying Out the Invention]

[0012] In this specification, when there is an expression such as "(meth)acryl", it means "acryl and / or methacryl", when there is an expression such as "(meth)acrylate", it means "acrylate and / or methacrylate", when there is an expression such as "(meth)allyl", it means "allyl and / or methallyl", and when there is an expression such as "(meth)acrolein", it means "acrolein and / or methacrolein". Further, in this specification, when there is an expression such as "acid (salt)", it means "acid and / or its salt". Examples of the salt include alkali metal salts and alkaline earth metal salts, and specifically, for example, sodium salts, potassium salts, etc. are included.

[0013] <<1. Overall Structure>> The surface protection film according to an embodiment of the present invention has a base material and an adhesive layer. As long as the surface protection film according to an embodiment of the present invention has a base material and an adhesive layer, it may have any appropriate other member (any appropriate other layer, etc.) within a range that does not impair the effects of the present invention. Examples of such other layers include an easy-adhesion layer, an easy-sliding layer, an anti-blocking layer, an antistatic layer, an antireflection layer, and an oligomer prevention layer. Such other layers may be only one layer or two or more layers.

[0014] For the surface protection film according to an embodiment of the present invention, a release liner (which may also be referred to as a release sheet or a separator) may be provided on the surface of the adhesive layer opposite to the base material for protecting the adhesive layer. This release liner is typically peeled off when the surface protection film according to an embodiment of the present invention is used.

[0015] 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.

[0016] Examples of the plastic film as the liner base material include a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, a vinyl chloride copolymer film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, and an ethylene-vinyl acetate copolymer film.

[0017] The thickness of the release liner is, for example, 1 μm to 500 μm, and may be 3 μm to 350 μm, may be 5 μm to 200 μm, or may be 10 μm to 150 μm.

[0018] 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.

[0019] The thickness of the surface protection 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 protection 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, 20 μm to 300 μm, 20 μm to 200 μm, or 30 μm to 170 μm.

[0020] ≪≪2. Surface Protection Film≫≫ The surface protection film according to the embodiment of the present invention can exhibit stable peelability even with variations in the time from application to peeling, as well as temperature and humidity. This stable peelability can be evaluated using the coefficient of variation (standard deviation / mean) of multiple measurements obtained by applying the surface protection film according to the embodiment of the present invention to a predetermined substrate and peeling it off, while varying the time from application to peeling, temperature, and humidity.

[0021] The surface protective film according to the embodiment of the present invention preferably has a coefficient of variation of four peeling forces (a1) to (a4) measured after being attached to an acrylic plate, which is preferably 0.150 or less, but may also be 0.130 or less, 0.120 or less, 0.110 or less, or 0.100 or less. Details of the measurement will be described later.

[0022] Peeling force (a1): After being stored for one day in an environment of 23°C and 50% relative humidity, the peeling force was measured after being left to stand for 30 minutes in the same environment of 23°C and 50% relative humidity, and then measured at a peeling angle of 180 degrees and a tensile speed of 300 mm / min in the same environment of 23°C and 50% relative humidity. Peeling force (a2): After being stored for 5 days at a temperature of 23°C and a relative humidity of 50%, the material was left to stand for 30 minutes at a temperature of 23°C and a relative humidity of 50%, and then the peeling force was measured at a peeling angle of 180 degrees and a tensile speed of 300 mm / min at a temperature of 23°C and a relative humidity of 50%. Peeling force (a3): After storage for 5 days at a temperature of 50°C and a relative humidity of 17%, the material was left to stand for 30 minutes at a temperature of 23°C and a relative humidity of 50%, and then the peeling force was measured at a peeling angle of 180 degrees and a tensile speed of 300 mm / min at a temperature of 23°C and a relative humidity of 50%. Peeling force (a4): After being stored for 5 days at a temperature of 40°C and a relative humidity of 92%, the material was left to stand for 30 minutes at a temperature of 23°C and a relative humidity of 50%, and then measured at a peeling angle of 180 degrees and a tensile speed of 300 mm / min at a temperature of 23°C and a relative humidity of 50%.

[0023] The surface protection film according to the embodiment of the present invention has a peel force (a1) measured by attaching it to an acrylic plate, which is preferably 0.010N / 25mm to 0.200N / 25mm, but may also be 0.010N / 25mm to 0.150N / 25mm, 0.020N / 25mm to 0.120N / 25mm, 0.030N / 25mm to 0.100N / 25mm, or 0.040N / 25mm to 0.100N / 25mm.

[0024] The surface protection film according to the embodiment of the present invention preferably has a coefficient of variation of 0.260 or less for the four peeling forces measured after being attached to an acrylic film: (a1), (a2) above, and (a5), (a6) below. The coefficient of variation for these four peeling forces may be 0.220 or less, 0.200 or less, 0.180 or less, or 0.160 or less. Details of the measurement will be described later.

[0025] Peeling force (a5): After being stored for 5 days at a temperature of 60°C and a relative humidity of 11%, the material was left to stand for 30 minutes at a temperature of 23°C and a relative humidity of 50%, and then measured at a peeling angle of 180 degrees and a tensile speed of 300 mm / min at a temperature of 23°C and a relative humidity of 50%. Peeling force (a6): After being stored for 5 days in an environment of 60°C and 90% relative humidity, the peeling force was measured after being left to stand for 30 minutes in an environment of 23°C and 50% relative humidity, and then in an environment of 23°C and 50% relative humidity with a peeling angle of 180 degrees and a tensile speed of 300 mm / min.

[0026] The surface protective film according to the embodiment of the present invention has a coefficient of variation of the four peeling forces (a1), (a2), (a5), and (a6) measured after being attached to a reflective polarizing film, which is preferably 0.180 or less, but may also be 0.160 or less, 0.140 or less, 0.130 or less, or 0.120 or less. Details of the measurement will be described later.

[0027] In the embodiment of the present invention, the coefficient of variation of the four peeling forces (a1), (a2), (a5), and (a6) measured after being attached to a hard coat film is preferably 0.180 or less, but may also be 0.170 or less, 0.160 or less, 0.150 or less, or 0.140 or less. Details of the measurement will be described later.

[0028] The surface protection film according to the embodiment of the present invention can reduce the contamination of the adherend. This reduction in the contamination of the adherend can be evaluated using the water contact angle of the peeled surface of the glass plate after the surface protection film according to the embodiment of the present invention has been attached to and peeled off the glass plate as an indicator.

[0029] In the embodiment of the present invention, the water contact angle of the peeled surface of the glass plate after the surface protective film has been attached to and peeled off the glass plate is preferably greater than 5.0°, may be greater than 6.0°, may be greater than 7.0°, may be greater than 8.0°, or may be greater than 9.0°.

[0030] ≪2-1. Base material≫ The base material may consist of a single layer, or it may consist of a laminated structure of two or more layers.

[0031] The thickness of the substrate can be any appropriate thickness as long as it does not impair the effects of the present invention. In order to better express the effects of the present invention, the thickness of the substrate is preferably 5 μm to 1000 μm, but may also be 10 μm to 800 μm, 20 μm to 600 μm, or 30 μm to 400 μm.

[0032] Any suitable material can be used as the base material, depending on the application. Examples include plastics, paper, metal films, and nonwoven fabrics, with plastic being preferred. 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, the base material may be composed of two or more types of plastics.

[0033] Examples of plastics include polyester resins, polyolefin resins, cyclic polyolefin resins, polyamide resins, polyimide resins, polyether ether ketones, polyether sulfones, polyarylate resins, and aramid resins. Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. Examples of polyolefin resins include homopolymers of olefin monomers and copolymers of olefin monomers, specifically, homopolypropylene; propylene copolymers such as block, random, and graft types with ethylene as the copolymer component; reactor TPO; ethylene polymers such as low density, high density, linear low density, and ultra-low density; ethylene copolymers such as ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-butyl acrylate copolymers, ethylene-methacrylic acid copolymers, and ethylene-methyl methacrylate copolymers. Examples of cyclic polyolefin resins include norbornene resins.

[0034] The substrate layer may contain any suitable additives as needed. Examples of additives that may be included in the substrate layer include antioxidants, UV absorbers, light stabilizers, antistatic agents, fillers, and pigments. The type, number, and amount of additives that may be included in the substrate layer can be appropriately determined depending on the purpose.

[0035] For surfaces of the substrate that do not have an adhesive layer, an antistatic layer containing any suitable antistatic agent, such as conductive polymers, carbon nanotubes, or ion-conducting polymers, can be provided to suppress the generation of static electricity. Furthermore, for purposes such as forming a winding body that is easy to unwind, the substrate can be treated by adding fatty acid amides, polyethyleneimines, long-chain alkyl additives, etc., or a coating layer consisting of any suitable release agent, such as silicone-based release agents, long-chain alkyl-based release agents, or fluorine-based release agents, can be provided.

[0036] ≪2-2. Adhesive Layer≫ The adhesive layer may consist of a single layer or a laminated structure of two or more layers.

[0037] The thickness of the adhesive layer is preferably 0.5 μm to 150 μm, but may also be 1 μm to 100 μm, 2 μm to 80 μm, 3 μm to 50 μm, 4 μm to 30 μm, or 5 μm to 25 μm, in order to better exhibit the effects of the present invention.

[0038] The adhesive layer can be formed by any suitable method. Such methods include, for example, applying an adhesive composition that forms the adhesive constituting the adhesive layer onto any suitable substrate, heating and drying as necessary, and curing as necessary to form an adhesive layer on the substrate; or applying an adhesive composition that forms the adhesive constituting the adhesive layer onto any suitable film such as a release liner, heating and drying as necessary, and curing as necessary to form an adhesive layer on the film, and then forming an adhesive layer on the substrate by laminating and transferring any suitable substrate onto the adhesive layer.

[0039] Any suitable means can be used to apply the adhesive composition, as long as it does not impair the effects of the present invention. Examples of such application methods include the roll coating method, gravure roll coating method, reverse roll coating method, kiss roll coating method, dip roll coating method, bar coating method, roll brush coating method, spray coating method, knife coating method, air knife coating method, comma coating method, direct coating method, and die coating method.

[0040] The heating and drying of the adhesive composition can be carried out by any suitable means, as long as it does not impair the effects of the present invention. Examples of such heating and drying methods include heating to 60°C to 180°C, or performing an aging treatment at a temperature of approximately room temperature.

[0041] The curing of the adhesive composition can be carried out by any suitable means, as long as it does not impair the effects of the present invention. Examples of such curing means include heat, ultraviolet irradiation, laser irradiation, alpha irradiation, beta irradiation, gamma irradiation, X-ray irradiation, and electron beam irradiation.

[0042] The adhesive layer is composed of an acrylic adhesive, and the acrylic adhesive is formed from an acrylic adhesive composition.

[0043] Acrylic adhesives can thus be defined as those formed from acrylic adhesive compositions. This is because acrylic adhesives are formed when acrylic adhesive compositions undergo crosslinking reactions such as heating or ultraviolet irradiation, making it impossible and impractical to directly identify acrylic adhesives by their structure. Therefore, the definition "formed from acrylic adhesive compositions" appropriately identifies acrylic adhesives as a "substance."

[0044] The acrylic adhesive composition contains an acrylic polymer and a surfactant (A). The acrylic polymer is sometimes referred to as the base polymer.

[0045] <2-2-1. Acrylic polymers> The acrylic polymer may be of one type or two or more types.

[0046] The content of the acrylic polymer in the acrylic adhesive composition is preferably 60% to 99.9% by weight in terms of solid content, but may also be 65% to 99.9% by weight, 70% to 99.9% by weight, 75% to 99.9% by weight, or 80% to 99.9% by weight.

[0047] As the acrylic polymer, any suitable acrylic polymer can be used, as long as it does not impair the effects of the present invention.

[0048] The weight-average molecular weight of the acrylic polymer is preferably 300,000 to 2,500,000, but may also be 350,000 to 2,000,000, 400,000 to 1,800,000, or 500,000 to 1,500,000, in order to better exhibit the effects of the present invention.

[0049] The glass transition temperature (Tg) of the acrylic polymer may preferably be 0°C or lower, or -10°C or lower, in order to better exhibit the effects of the present invention.

[0050] The glass transition temperature (Tg) of an acrylic polymer can be determined by the following FOX formula, where Tgn (°C) is the glass transition temperature of the homopolymer obtained from each of the monomers constituting the acrylic polymer. The theoretical glass transition temperature obtained from the FOX formula can be consistent with the measured glass transition temperature obtained by methods such as differential scanning calorimetry (DSC) or dynamic viscoelasticity measurement. If a theoretical value cannot be calculated, the measured glass transition temperature can be used.

[0051] 1 / (Tg+273)=Σ〔Wn / (Tgn+273)〕

[0052] In the formula, Tg(°C) is the glass transition temperature of the copolymer, Wn(-) is the weight fraction of monomer n in the acrylic polymer, Tgn(°C) is the glass transition temperature of the homopolymer obtained from monomer n, and n represents the type of monomer.

[0053] The glass transition temperature of the homopolymer used to calculate Tg can be any value found in any appropriate source. For example, for the monomers listed below, the following values ​​are used as the glass transition temperatures of the homopolymers of those monomers. n-butyl acrylate (BA): -55℃ Lauryl acrylate (LA): -23℃ 2-Ethylhexyl acrylate (2EHA): -70℃ Acrylic acid (AA): 106℃ Methacrylic acid (MA): 228℃ 2-Hydroxyethyl acrylate (2HEA): -15℃ 4-Hydroxybutyl acrylate (4HBA): -40℃ N-vinyl-2-pyrrolidone (NVP): 80℃ Methyl methacrylate (MMA): 105℃

[0054] For the glass transition temperatures of monomer homopolymers other than those exemplified above, values ​​listed in, for example, the "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 ​​of the monomer manufacturers should be adopted. For monomer homopolymers not listed in the "Polymer Handbook" and for which no catalog values ​​are provided by monomer manufacturers, the Tg value obtained by the measurement method described in Japanese Patent Publication No. 2007-51271 should be used. Specifically, 100 parts by weight of monomer, 0.2 parts by weight of azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as a polymerization solvent are added to a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, and the mixture is stirred for 1 hour while circulating nitrogen gas. After removing oxygen from the polymerization system in this way, the temperature is raised to 63°C and the reaction is carried out for 10 hours. Next, the mixture is cooled to room temperature to obtain a homopolymer solution with a solid content of 33% by weight. Then, this homopolymer solution is cast onto a release liner and dried to prepare a test sample (sheet-like homopolymer) with a thickness of approximately 2 mm. This test sample is punched out into a disc shape with a diameter of 7.9 mm, sandwiched between parallel plates, and the viscoelasticity is measured using a viscoelasticity tester (ARES, Rheometrics) in shear mode while applying a shear strain at a frequency of 1 Hz, in a temperature range of -70°C to 150°C, at a heating rate of 5°C / min. The peak top temperature of tanδ is taken as the Tg of the homopolymer.

[0055] Examples of acrylic polymers include acrylic polymers formed by polymerization from a composition (M) comprising an alkyl (meth)acrylate (component a) having 4 to 12 carbon atoms in the alkyl group of the alkyl ester portion, and at least one (component b) selected from the group consisting of (meth)acrylate esters having an OH group and (meth)acrylic acid. Component a and component b may each be independent of one type or two or more types.

[0056] Examples of alkyl (meth)acrylate esters in which the alkyl group of the alkyl ester portion has 4 to 12 carbon atoms include n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate. Among these, n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred in terms of being able to better exhibit the effects of the present invention, and more preferably n-butyl acrylate and 2-ethylhexyl acrylate.

[0057] Examples of (meth)acrylic acid esters having an OH group include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate. Among these, hydroxyethyl (meth)acrylate is preferred, and more preferably, hydroxyethyl acrylate, in terms of being able to better express the effects of the present invention.

[0058] As the (meth)acrylic acid, acrylic acid is preferred in that it can better exhibit the effects of the present invention.

[0059] Composition (M) may contain copolymerizable monomers other than components a and b. The copolymerizable monomer may be one type or two or more types.Examples of such copolymerizable monomers include carboxyl group-containing monomers such as itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and their acid anhydrides (e.g., acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride) (excluding (meth)acrylic acid); (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide. ) Amide group-containing monomers such as acrylamide; amino group-containing monomers such as (meth)aminoethyl acrylate, (meth)dimethylaminoethyl acrylate, and (meth)t-butylaminoethyl acrylate; epoxy group-containing monomers such as (meth)glycidyl acrylate and (meth)methylglycidyl acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; N-vinyl-2-pyrrolidone, (meth)acryloylmorpholine, N-vinylpiperidone, N-vinylpiperazine, N-vinylpyrrole, N-vinyl Examples include heterocyclic vinyl monomers such as imidazole, vinylpyridine, vinylpyrimidine, and vinyloxazole; sulfonic acid group-containing monomers such as sodium vinylsulfonate; phosphate group-containing monomers such as 2-hydroxyethyl acryloyl phosphate; imide group-containing monomers such as cyclohexyl maleimide and isopropyl maleimide; isocyanate group-containing monomers such as 2-methacryloyloxyethyl isocyanate; (meth)acrylic acid esters having alicyclic hydrocarbon groups such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; (meth)acrylic acid esters having aromatic hydrocarbon groups such as phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, and benzyl (meth)acrylate; vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene and vinyltoluene; olefins and dienes such as ethylene, butadiene, isoprene, and isobutylene; vinyl ethers such as vinyl alkyl ethers; and vinyl chloride.

[0060] Polyfunctional monomers can also be used as copolymerizable monomers. A polyfunctional monomer is a monomer having two or more ethylenically unsaturated groups in one molecule. Any suitable ethylenically unsaturated group can be used as the ethylenically unsaturated group, as long as it does not impair the effects of the present invention. Examples of such ethylenically unsaturated groups include radical polymerizable functional groups such as vinyl groups, propenyl groups, isopropenyl groups, vinyl ether groups (vinyloxy groups), and allyl ether groups (allyloxy groups). Examples of polyfunctional monomers include hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl(meth)acrylate, vinyl(meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, and urethane acrylate. Such polyfunctional monomers may be present individually or in combination of two or more types.

[0061] As copolymerizable monomers, alkoxyalkyl (meth)acrylates may also be used. Examples of alkoxyalkyl (meth)acrylates include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate. There may be only one alkoxyalkyl (meth)acrylate or two or more.

[0062] The content of the alkyl (meth)acrylate (component a) in which the alkyl group of the alkyl ester portion has 4 to 12 carbon atoms is preferably 30% by weight or more relative to the total amount (100% by weight) of the monomer components constituting the acrylic polymer, and may be 40% to 99.9% by weight, 50% to 99% by weight, 50% to 99% by weight, 60% to 98% by weight, 70% to 98% by weight, 80% to 97% by weight, or 90% to 97% by weight.

[0063] The content of at least one component (b) selected from the group consisting of (meth)acrylic acid esters having an OH group and (meth)acrylic acid is preferably 0.1% by weight or more, and may be 1% to 30% by weight, 1.5% to 20% by weight, 2% to 10% by weight, or 2.5% to 5% by weight, relative to the total amount of monomer components constituting the acrylic polymer, in order to better express the effects of the present invention.

[0064] The content of copolymerizable monomers other than components a and b is preferably 69.9% by weight or less relative to the total amount of monomer components constituting the acrylic polymer (100% by weight), and may be 0% to 50% by weight, 0% to 30% by weight, 0% to 20% by weight, 0% to 10% by weight, or 0% to 5% by weight, in order to better exhibit the effects of the present invention.

[0065] Composition (M) may contain any other suitable components, as long as they do not impair the effects of the present invention. Examples of such other components include polymerization initiators, chain transfer agents, and solvents. The content of these other components may be any suitable amount, as long as they do not impair the effects of the present invention.

[0066] Depending on the type of polymerization reaction, the polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator (photoinitiator). There may be only one polymerization initiator or two or more.

[0067] Thermal polymerization initiators can preferably be used when obtaining acrylic polymers by solution polymerization. Examples of such thermal polymerization initiators include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid)dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane)dihydrochloride, and 2,2'-azobis[2-(5-methyl-2-imidazoline-2-yl)pro Azo initiators such as pan-dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethylene isobutylamidine), and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (VA-057, manufactured by Wako Pure Chemical Industries, Ltd.); persulfates such as potassium persulfate and ammonium persulfate, and di(2-ethylhexyl) peroxydicarbonate. Examples include peroxide initiators such as di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butylhydroperoxide, and hydrogen peroxide; redox initiators combining peroxides with reducing agents, such as combinations of persulfates and sodium bisulfite, and combinations of peroxides and sodium ascorbate; substituted ethane initiators such as phenyl-substituted ethane; and aromatic carbonyl compounds.

[0068] Photopolymerization initiators can preferably be used when obtaining acrylic polymers by active energy ray polymerization. Examples of photopolymerization initiators include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, and thioxanthone-based photopolymerization initiators.

[0069] Examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, and anisole methyl ether. Examples of acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. An example of an aromatic sulfonyl chloride-based photopolymerization initiator is 2-naphthalenesulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzyl-based photopolymerization initiators include benzyl. Examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. Examples of ketal-based photopolymerization initiators include benzyldimethylketal. Examples of thioxanthone-based photopolymerization initiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

[0070] The amount of polymerization initiator used can be set to any appropriate amount, as long as it does not impair the effects of the present invention. For example, if the total amount of monomer components constituting the acrylic polymer is 100 parts by weight, the amount of polymerization initiator used may be 0.001 to 5 parts by weight, or it may be 0.01 to 3 parts by weight, or 0.05 to 2 parts by weight.

[0071] <2-2-2. Surfactants> The acrylic adhesive composition contains a surfactant (A). Surfactant (A) may be one type or two or more types.

[0072] Surfactant (A) is, (1) It does not have an aromatic ring, (2)-(CH2CH2O) n It has a polyethylene oxide skeleton represented by -(where 5≦n<20).

[0073] The effects of the present invention can be realized by the inclusion of such a specific surfactant (A) in the acrylic adhesive composition. Regarding (1) above, because surfactant (A) does not have an aromatic ring, in terms of the physical behavior of surfactant (A) in the formed acrylic adhesive, surfactant (A) can move flexibly on its molecular backbone. When the acrylic adhesive composition is coated and aged as necessary to form the acrylic adhesive, an appropriate WBL (Weak Boundary Layer) is formed, which is presumed to contribute to the easy peeling of the acrylic adhesive. Furthermore, regarding (2) above, because surfactant (A) has a polyethylene oxide backbone with a specific chain length range, the phenomenon of being unable to be unevenly distributed near the surface of the acrylic adhesive due to steric hindrance is suppressed, and similar to (1) above, an appropriate WBL is formed, which is presumed to contribute to the easy peeling of the acrylic adhesive. Furthermore, since surfactant (A) has a flexible structure without aromatic rings and a polyethylene oxide backbone with a specific chain length range, as described in (1) and (2) above, it is presumed that it interacts more readily with the base polymer in the acrylic adhesive composition, thereby suppressing the transfer of surfactant (A) to the adherend and contributing to the reduction of the adherend's contamination. As a result of the above, it is presumed that the effects of the present invention can be realized.

[0074] Conventionally, techniques using surfactants in the manufacture of adhesive layers for surface protective films have been reported. For example, Japanese Patent Publication No. 6302233 reports an adhesive layer containing an acrylic polymer and a surfactant having an aromatic ring. However, the surfactant used in the invention described in Japanese Patent Publication No. 6302233 is an aromatic ring surfactant used to improve wettability to other layers when other layers are applied to the surface of the adherend to which the adhesive layer was attached, and to improve curl adjustment when attached to the adherend. However, there is no description or suggestion of selecting and adopting a specific surfactant (A) used in the embodiments of the present invention in order to exhibit stable peelability even with changes in time from application to peeling, temperature and humidity, and to reduce contamination of the adherend.

[0075] Furthermore, Japanese Patent Publication No. 2019-194330 describes a surface protection film that allows for easy peeling from the adherend, enables light peeling, and has a high detection rate for scratches and foreign matter contamination. The adhesive layer of the surface protection film is described as an acrylic adhesive containing an acrylic polymer. Japanese Patent Publication No. 2019-194330 states that a surfactant may be included from the viewpoint of further improving the wettability of the surface protection film, and that anionic surfactants are preferred. However, there is no description or suggestion regarding the problems of the present invention, such as exhibiting stable peelability even with changes in time from application to peeling, temperature, and humidity, and reducing the contamination of the adherend. There is also no description or suggestion of selecting and adopting a specific surfactant (A) to be used in the embodiments of the present invention. In the examples, polyoxyethylene nonylpropenylphenyl ether sulfate ammonium (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon HS-10) having an aromatic ring is used.

[0076] If surfactant (A) has an aromatic ring, the effects of the present invention may not be exhibited.

[0077] Surfactant (A) is -(CH2CH2O) n-(However, if it does not have a polyethylene oxide skeleton represented by 5≦n<20, the effects of the present invention may not be exhibited. When the surfactant (A) has a polyethylene oxide skeleton represented by -(CH2CH2O) n - even if it has a polyethylene oxide skeleton represented by, for example, in the case of n<5 or 20≦n, the effects of the present invention may not be exhibited.

[0078] The surfactant (A) may have n in the polyethylene oxide skeleton such that 5≦n<15, 5≦n<13, 5≦n≦12, 5<n≦12, or 8≦n≦12.

[0079] The surfactant (A) may have an alkyl group having 5 or more carbon atoms. The number of carbon atoms of such an alkyl group may be 5 to 30, 6 to 20, 7 to 15, or 8 to 12.

[0080] Examples of the surfactant (A) include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. Anionic surfactants are preferred in terms of being able to more effectively exhibit the effects of the present invention.

[0081] When the surfactant (A) is an anionic surfactant, the surfactant (A) has an anionic hydrophilic group -X. Examples of the anionic hydrophilic group -X include, for example, -SO3M 1 (M 1 represents a hydrogen atom, an alkali metal, an ammonium group, or an alkanolammonium group.), -P(O)(OM 2 )(OM 3 )(M 2 , M 3 each independently represents a hydrogen atom, an alkali metal, an ammonium group, or an alkanolammonium group.).

[0082] The surfactant (A) may be a reactive surfactant. Examples of the reactive surfactant include surfactants having a vinyl group (CH2=CH-).

[0083] In terms of being able to better demonstrate the effects of the present invention, one preferred embodiment of the surfactant (A) is: (1) It does not have an aromatic ring, (2)-(CH2CH2O) n - (where 5≦n<20) has a polyethylene oxide skeleton, (3) An anionic surfactant, (4) It is a reactive surfactant.

[0084] The surfactant (A) may be, for example, a surfactant represented by general formula (1). [ka]

[0085] In general formula (1), R is a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms, and X is -SO3M 1 (M 1 ) represents a hydrogen atom, alkali metal, ammonium group, or alkanolammonium group. ), -P(O)(OM 2 )(OM 3 )(M 2 M 3 Each of these independently represents a hydrogen atom, an alkali metal, an ammonium group, or an alkanolammonium group. where n is 5 ≤ ​​n < 20.

[0086] In general formula (1), R may be a monovalent aliphatic hydrocarbon group having 2 to 18 carbon atoms, a monovalent aliphatic hydrocarbon group having 4 to 16 carbon atoms, a monovalent aliphatic hydrocarbon group having 6 to 14 carbon atoms, or a monovalent aliphatic hydrocarbon group having 8 to 12 carbon atoms.

[0087] The amount of surfactant (A) in the acrylic adhesive composition is preferably 0.001 to 10 parts by weight per 100 parts by weight of acrylic polymer, but may also be 0.01 to 5 parts by weight, 0.05 to 1 part by weight, 0.05 to 0.50 parts by weight, 0.05 to 0.40 parts by weight, 0.05 to 0.30 parts by weight, 0.05 to 0.25 parts by weight, 0.05 to 0.20 parts by weight, or 0.05 parts by weight or more but less than 0.20 parts by weight, in order to better exhibit the effects of the present invention.

[0088] <2-2-3. Crosslinking Agents> The acrylic adhesive composition may contain a crosslinking agent. By using a crosslinking agent, the cohesive force of the acrylic adhesive can be improved, and the effects of the present invention can be further exhibited. There may be only one type of crosslinking agent, or there may be two or more types.

[0089] Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, metal chelate-based crosslinking agents, and peroxides. Preferably, at least one isocyanate-based crosslinking agent selected from the group consisting of isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and peroxides, as this can better express the effects of the present invention.

[0090] Isocyanate-based crosslinking agents can be compounds having two or more isocyanate groups (including isocyanate-regenerating polar groups in which isocyanate groups are temporarily protected by a blocking agent or quantification, etc.) in one molecule. Examples of isocyanate-based crosslinking agents include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate.

[0091] Examples of isocyanate crosslinking agents include: lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and polymethylene polyphenyl isocyanate; isocyanate adducts such as trimethylolpropane / tolylene diisocyanate trimer adduct (e.g., manufactured by Tosoh Corporation, trade name: Coronate L), trimethylolpropane / hexamethylene diisocyanate trimer adduct (e.g., manufactured by Tosoh Corporation, trade name: Coronate HL), and isocyanurate derivatives of hexamethylene diisocyanate (e.g., manufactured by Tosoh Corporation, trade name: Coronate HX); xyl Examples include trimethylolpropane adducts of reylene diisocyanate (e.g., Mitsui Chemicals, trade name: Takenate D110N), trimethylolpropane adducts of xylylene diisocyanate (e.g., Mitsui Chemicals, trade name: Takenate D120N), trimethylolpropane adducts of isophorone diisocyanate (e.g., Mitsui Chemicals, trade name: Takenate D140N), trimethylolpropane adducts of hexamethylene diisocyanate (e.g., Mitsui Chemicals, trade name: Takenate D160N), trimethylolpropane adducts of tolylene diisocyanate (e.g., Mitsui Chemicals, trade name: Takenate D101E); polyether polyisocyanates, polyester polyisocyanates, and adducts thereof with various polyols; and polyfunctionalized polyisocyanates with isocyanurate bonds, biuret bonds, allophanate bonds, etc. Among these, aromatic isocyanates and alicyclic isocyanates are preferred because they can achieve a good balance between deformability and cohesiveness.

[0092] As epoxy crosslinking agents, polyfunctional epoxy compounds having two or more epoxy groups in one molecule can be used. Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylenediline, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and sorbitol polyglycidyl ether. Examples of epoxy crosslinking agents include tel, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate ester, diglycidyl o-phthalate ester, triglycidyl-tris(2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Examples of commercially available epoxy crosslinking agents include the trade names "Tetrad C" and "Tetrad X" manufactured by Mitsubishi Gas Chemical Company.

[0093] Examples of peroxides include dibenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, di-t-butylperoxy-3,3,5-trimethylcyclohexane, t-butyl hydroperoxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexine-3, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-mono(t-butylperoxy)hexane, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, and t-butylperoxy Examples include neodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, di(4-methylbenzoyl) peroxide, t-butyl peroxyisobutyrate, 1,1-di(t-hexyl peroxy)cyclohexane, 1,1-di(t-butyl peroxy)cyclohexane, t-butyl peroxy-2-ethylhexyl carbonate, t-amyl peroxyisopropyl carbonate, 3,5,5-trimethylhexanoyl peroxide, t-butyl peroxy-2-hexanoate, t-butyl peroxypivalate, and t-hexyl peroxypivalate. Examples of commercially available peroxides include the "Nipper BMT" series and "Nipper BW" series manufactured by Nippon Oil & Fats Co., Ltd.

[0094] The amount of crosslinking agent in the acrylic adhesive composition can be any appropriate amount, as long as it does not impair the effects of the present invention. Such an amount, which allows the effects of the present invention to be more fully expressed, is preferably 0.01 to 20 parts by weight, but may also be 0.01 to 18 parts by weight, 0.01 to 15 parts by weight, or 0.05 to 10 parts by weight per 100 parts by weight of the acrylic polymer.

[0095] <2-2-4. Crosslinking catalysts> The acrylic adhesive composition may contain a crosslinking catalyst. The crosslinking catalyst may be one type or two or more types. Examples of crosslinking catalysts include metal-based crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, ferric narcem, butyltin oxide, and dioctyltin dilaurate. Among these, dioctyltin dilaurate is preferred because it can fully exhibit the effects of the present invention.

[0096] The amount of crosslinking catalyst in the acrylic adhesive composition can be any appropriate amount, as long as it does not impair the effects of the present invention. Such an amount is preferably 0.001 to 0.1 parts by weight per 100 parts by weight of acrylic polymer, but may also be 0.003 to 0.07 parts by weight, or 0.005 to 0.05 parts by weight, in order to better exhibit the effects of the present invention.

[0097] <2-2-5. Crosslinking retarders> The acrylic adhesive composition may contain a crosslinking retarder. The crosslinking retarder may be one type or two or more types. Examples of crosslinking retarders include β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate, as well as β-diketones such as acetylacetone, 2,4-hexanedione, and benzoylacetone. Among these, acetylacetone is preferred because it can fully exhibit the effects of the present invention.

[0098] The amount of crosslinking retarder in the acrylic adhesive composition can be any appropriate amount, as long as it does not impair the effects of the present invention. Such an amount is preferably 0.01 to 10 parts by weight per 100 parts by weight of the acrylic polymer, but may also be 0.05 to 5 parts by weight, or 0.1 to 3 parts by weight, in order to better exhibit the effects of the present invention.

[0099] <2-2-6. Other Ingredients> The acrylic adhesive composition may contain any other suitable components as long as they do not impair the effects of the present invention. Examples of such other components include polymer components other than acrylic polymers, acrylic oligomers, crosslinking accelerators, silane coupling agents, tackifying resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), anti-aging agents, inorganic fillers, organic fillers, metal powders, colorants (pigments, dyes, etc.), foils, UV absorbers, antioxidants, light stabilizers, nucleating agents, chain transfer agents, plasticizers, softeners, antistatic agents (ionic compounds, etc.), conductive agents, stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, and the like.

[0100] The content of other components in the acrylic adhesive composition can be any appropriate amount depending on the purpose, as long as it does not impair the effects of the present invention. For example, the content of other components in the acrylic adhesive composition may be 0 to 30 parts by weight, 0 to 20 parts by weight, or 0 to 10 parts by weight.

[0101] 3. Optical and Electronic Devices The surface protection film according to the embodiment of the present invention can be suitably used for surface protection of optical and electronic devices, for example, in the manufacturing process of optical and electronic devices, by being bonded to the exposed surface of optical or electronic components during processing, assembly, inspection, transportation, etc., to prevent scratches on the surface of optical or electronic components and to provide impact resistance. The optical device according to the embodiment of the present invention includes the surface protection film according to the embodiment of the present invention. The electronic device according to the embodiment of the present invention includes the surface protection film according to the embodiment of the present invention. [Examples]

[0102] 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.

[0103] <Measurement of peeling force on acrylic sheets and calculation of coefficient of variation> The surface protection film to be evaluated was cut to a size of 25 mm in width and 100 mm in length. The release liner was peeled off from the adhesive layer, and the film was roll-pressed onto an acrylic plate (Mitsubishi Chemical Corporation, product name "Acrylite", 2 mm thick, 70 mm wide, 100 mm long) with the length aligned, at a pressure of 0.25 MPa and a feed rate of 0.3 m / min, to be used as a measurement sample. The peel forces (a1) to (a4) below were measured for the obtained sample. The peel force was measured by performing a peel test at a peel angle of 180 degrees and a tensile speed of 300 mm / min using a precision universal testing machine (Shimadzu Corporation, AUTOGRAPH AG-X plus) as the measuring device. Peeling force (a1): After being stored for one day in an environment of 23°C and 50% relative humidity, the peeling force was measured after being left to stand for 30 minutes in an environment of 23°C and 50% relative humidity, and then measured again in an environment of 23°C and 50% relative humidity. Peeling force (a2): After being stored for 5 days at a temperature of 23°C and a relative humidity of 50%, the peeling force was measured after being left to stand for 30 minutes at a temperature of 23°C and a relative humidity of 50%, and then again at a temperature of 23°C and a relative humidity of 50%. Peeling force (a3): After being stored for 5 days in an environment of 50°C and 17% relative humidity, the peeling force was measured after being left to stand for 30 minutes in an environment of 23°C and 50% relative humidity, and then again in an environment of 23°C and 50% relative humidity. Peeling force (a4): After being stored for 5 days at a temperature of 40°C and a relative humidity of 92%, the peeling force was measured after being left to stand for 30 minutes at a temperature of 23°C and a relative humidity of 50%, and then again at a temperature of 23°C and a relative humidity of 50%. The mean and standard deviation of the obtained peeling forces (a1) to (a4) were calculated, and the coefficient of variation = (standard deviation / mean) was determined.

[0104] <Measurement of peeling force and calculation of coefficient of variation for acrylic films> The surface protection film to be evaluated was cut to a size of 25 mm in width and 100 mm in length. The release liner was peeled off from the adhesive layer, and the film was roll-pressed onto an acrylic film (product name "RV-20UB-1330", manufactured by Toyo Kohan Co., Ltd.) at a pressure of 0.25 MPa and a feed rate of 0.3 m / min to obtain the measurement sample. The peel forces (a1), (a2), (a5), and (a6) were measured for the obtained sample. The peel force was measured using a precision universal testing machine (Shimadzu Corporation, AUTOGRAPH AG-X plus) with a peel angle of 180 degrees and a tensile speed of 300 mm / min. Peeling force (a1): After being stored for one day in an environment of 23°C and 50% relative humidity, the peeling force was measured after being left to stand for 30 minutes in an environment of 23°C and 50% relative humidity, and then measured again in an environment of 23°C and 50% relative humidity. Peeling force (a2): After being stored for 5 days at a temperature of 23°C and a relative humidity of 50%, the peeling force was measured after being left to stand for 30 minutes at a temperature of 23°C and a relative humidity of 50%, and then again at a temperature of 23°C and a relative humidity of 50%. Peeling force (a5): After being stored for 5 days at a temperature of 60°C and a relative humidity of 11%, the peeling force was measured after being left to stand for 30 minutes at a temperature of 23°C and a relative humidity of 50%, and then again at a temperature of 23°C and a relative humidity of 50%. Peeling force (a6): After being stored for 5 days at a temperature of 60°C and a relative humidity of 90%, the peeling force was measured after being left to stand for 30 minutes at a temperature of 23°C and a relative humidity of 50%, and then again at a temperature of 23°C and a relative humidity of 50%. The mean and standard deviation of the obtained peeling forces (a1), (a2), (a5), and (a6) were calculated, and the coefficient of variation = (standard deviation / mean) was determined.

[0105] <Measurement of peeling force and calculation of coefficient of variation for reflective polarizing film> The surface protection film to be evaluated was cut to a size of 25 mm in width and 100 mm in length. The release liner was peeled off from the adhesive layer, and the film was roll-pressed onto a reflective polarizing film (3M product name "APF-V3" (polarization degree: 95%)) at a pressure of 0.25 MPa and a feed rate of 0.3 m / min to obtain the measurement sample. For the obtained measurement samples, the peel forces (a1), (a2), (a5), and (a6) were measured in the same manner as in <Measurement of peel force on acrylic film and calculation of coefficient of variation>. The mean and standard deviation of the obtained peel forces (a1), (a2), (a5), and (a6) were calculated, and the coefficient of variation = (standard deviation / mean) was determined.

[0106] <Measurement of peeling force and calculation of coefficient of variation for hard coat film> (Manufacturing of hard coat film) A resin solution (DIC Corporation, trade name "UNIDIC 17-806", solids content 80%) in which a UV-curable resin monomer or oligomer mainly composed of urethane acrylate was dissolved in butyl acetate was prepared. To this solution, 5 parts by weight of a photopolymerization initiator (BASF Corporation, product name "IRGACURE 906") and 0.01 parts by weight of a leveling agent (DIC Corporation, product name "GRANDIC PC4100") were added per 100 parts by weight of solids in the solution. Cyclopentanone and propylene glycol monomethyl ether were added in a ratio of 45:55 to achieve a solids content of 36% in the resulting solution. A hard coat layer forming material was prepared in this manner. The obtained hard coat layer forming material was coated onto a transparent plastic film substrate (cellulose triacetate film, manufactured by Konica Minolta Advanced Layers, trade name "KC4UY", thickness 40 μm, refractive index 1.48), and a coating film was formed so that the hard coat layer thickness obtained after curing was 7.8 μm. Next, it was dried at 90°C for 1 minute, and then exposed to a high-pressure mercury lamp with an integrated light intensity of 300 mJ / cm². 2 The coating was cured by irradiating it with ultraviolet light to produce a hard coat film. Alternatively, as a hard film with a hard coat layer, you may use products manufactured by Nitto Denko Corporation, such as "REGQS1298DUHC3" or "REGQ1698GDUHC3+H2-BW". (Measurement of peeling force and calculation of coefficient of variation) The surface protection film to be evaluated was cut to a size of 25 mm in width and 100 mm in length. The release liner was peeled off from the adhesive layer, and the resulting hard coat film was roll-pressed onto the hard coat layer side at a pressure of 0.25 MPa and a feed rate of 0.3 m / min to obtain the measurement sample. For the obtained measurement samples, the peel forces (a1), (a2), (a5), and (a6) were measured in the same manner as in <Measurement of peel force on acrylic film and calculation of coefficient of variation>. The mean and standard deviation of the obtained peel forces (a1), (a2), (a5), and (a6) were calculated, and the coefficient of variation = (standard deviation / mean) was determined.

[0107] <Measurement of water contact angle of glass plate> The release liner was peeled off the surface protective film under evaluation to expose the adhesive layer. The exposed adhesive layer was attached to a glass plate (slide glass, product name "Preclean Water-Edged Polished t1.0", manufactured by Matsunami Glass Industry Co., Ltd., with a non-tin surface) at a temperature of 23°C and a relative humidity of 40%. After standing for 1 hour in an atmosphere of 70°C and a relative humidity of 7%, it was left to stand for 2 hours in an atmosphere of 23°C and a relative humidity of 40% before being peeled off. Subsequently, using a water contact angle measuring device (product name "DM700", manufactured by Kyowa Interface Chemical Co., Ltd.), approximately 1 μL of water droplet was dropped onto the surface of the glass plate to which the surface protective film had been attached (adhesion surface) at a temperature of 23°C and a relative humidity of 40%. The angle between the adhesion surface and the tangent to the edge of the dropped water droplet 1 second after dropping was measured and defined as the "water contact angle (°)". The surface protective film was attached to the non-tin surface of the glass plate.

[0108] <Evaluation of the appearance of the adherend> The four types of substrates used in the examples and comparative examples (acrylic plate, acrylic film, reflective polarizing film, and hard coat film) were cut into 4cm x 4cm pieces, and these were designated as substrates A1 (acrylic plate), A2 (acrylic film), A3 (reflective polarizing film), and A4 (hard coat film). The release liner was peeled off the surface protective film under evaluation, and the adhesive layer side was bonded to one side of each of the four types of substrates used in the examples and comparative examples (acrylic plate, acrylic film, reflective polarizing film, and hard coat film). The resulting laminates were cut into 4cm x 4cm pieces, and these were designated as laminates B1 (acrylic plate + surface protective film), B2 (acrylic film + surface protective film), B3 (reflective polarizing film + surface protective film), and B4 (hard coat film + surface protective film). Furthermore, the side of the reflective polarizing film to which the surface protective film is laminated was the side with the lower hexadecane contact angle, and the side of the hard coat film to which the surface protective film is laminated was the hard coat layer side. The hexadecane contact angle was measured using the following method. The release liner was peeled off the surface protective film under evaluation to expose the adhesive layer. The exposed adhesive layer was attached to a reflective polarizing film (3M, product name "APF-V3" (polarization degree: 95%)) at a temperature of 23°C and a relative humidity of 40%. After standing for 2 hours in an atmosphere of 23°C and 40% relative humidity, it was peeled off. Subsequently, using a water contact angle measuring device (product name "DM700", Kyowa Interface Chemical Co., Ltd.), approximately 4 μL of hexadecane was dropped onto the surface of the reflective polarizing film to which the surface protective film had been attached (the substrate surface) in an atmosphere of 23°C and 40% relative humidity using the liquid application method. The angle between the substrate surface and the tangent to the edge of the dropped hexadecane was measured 1 second after dropping and defined as the "hexadecane contact angle (°)". The adherends A1-A4 and laminates B1-B4 were each stored for 120 hours in an atmosphere of 60°C and 11% relative humidity, and then left to stand for 1 hour in an atmosphere of 23°C and 50% relative humidity. Subsequently, for substrates A1 to A4, a 5cm x 5cm piece of black acrylic sheet (manufactured by Nitto Resin Industry Co., Ltd., product name "CLAREX") was attached to the side opposite to the side to which the surface protective film was applied, and the resulting laminates were designated as laminates C1 to C4. Furthermore, for laminates B1 to B4, a 5cm x 5cm black acrylic sheet (manufactured by Nitto Resin Industry Co., Ltd., product name "CLAREX") was bonded to the side opposite to the side to which the surface protective film was bonded. The surface protective film was then peeled off from the resulting laminates to obtain laminates D1 to D4. For the obtained laminates D1-D4 and C1-C4, a fluorescent lamp was shone in a darkroom on the side where the surface protective film was attached, and the reflection was observed. The two corresponding appearances of the same substrate were then compared and evaluated according to the following criteria. ○: No whitening or hue change was observed in laminates D1-D4 compared to laminates C1-C4. ×: Laminates D1-D4 showed whitening and hue changes compared to laminates C1-C4.

[0109] <Surfactants used in the examples and comparative examples> • Polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt (product name "Aqualon KH-5", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): Does not have an aromatic ring, -(CH2CH2O) n It has a polyethylene oxide skeleton represented by -(n=5). • Polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt (product name "Aqualon KH-10", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): Does not have an aromatic ring, -(CH2CH2O) n It has a polyethylene oxide skeleton represented by -(n=10). • Polyoxyethylene nonylpropenylphenyl ether sulfate ammonium salt (product name "Aqualon HS-10", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): Contains an aromatic ring, -(CH2CH2O) n It has a polyethylene oxide skeleton represented by -(n=10). • Polyoxyethylene styrene-propenylphenyl ether sulfate ammonium salt (product name "Aqualon AR-10", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): Contains an aromatic ring, -(CH2CH2O) n It has a polyethylene oxide skeleton represented by -(n=10). • Polyoxyethylene styrene-propenylphenyl ether sulfate ammonium salt (product name "Aqualon AR-20", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): Contains an aromatic ring, -(CH2CH2O) n It has a polyethylene oxide skeleton represented by -(n=20). • Polyoxyethylene-1-(allyloxymethyl)alkoxyalkyl ether sulfate ammonium salt (product name "Adekaria Soap SR-20", manufactured by ADEKA): Does not have an aromatic ring, -(CH2CH2O) n It has a polyethylene oxide skeleton represented by -(n=20). • Sodium polyoxyethylene alkyl ether sulfate (product name "Latemul E-118B", manufactured by Kao Corporation): Does not have an aromatic ring, -(CH2CH2O) n It has a polyethylene oxide skeleton represented by -(n=20).

[0110] [Manufacturing Example 1]: Acrylic polymer In a reaction vessel equipped with a thermometer, stirrer, condenser, and nitrogen gas inlet tube, 96.2 parts by weight of 2-ethylhexyl acrylate (2EHA), 3.8 parts by weight of 2-hydroxyethyl acrylate (2HEA), and 0.2 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as monomer components, along with 150 parts by weight of ethyl acetate, were charged together. Nitrogen gas was introduced and the mixture was purged with nitrogen while gently stirring at 23°C. Subsequently, the polymerization reaction was carried out for 6 hours while maintaining the liquid temperature at around 65°C to produce an acrylic polymer solution (concentration 40% by weight). The weight-average molecular weight of the acrylic polymer was 540,000. The Tg of the acrylic polymer, calculated using the FOX formula, was (-70°C × 0.962) + (-15°C × 0.038) = (-67.34°C) + (-0.57°C) = -67.91°C.

[0111] [Example 1] The acrylic polymer solution obtained in Production Example 1 was diluted to a concentration of 20% by weight by adding ethyl acetate. To 100 parts by weight of solids in this solution, 0.300 parts by weight of the product name "Aqualon KH-5" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added as a surfactant, 5 parts by weight of the isocyanurate form of hexamethylene diisocyanate (product name "Coronate HX", manufactured by Tosoh Corporation) was added as a crosslinking agent, and 0.03 parts by weight of dibutyltin dilaurate (product name "OL-1", manufactured by Tokyo Fine Chemical Co., Ltd.) was added as a crosslinking catalyst. Furthermore, 3 parts by weight of acetylacetone was added as a crosslinking retarder relative to the total amount of solvent. The mixture was then stirred to prepare acrylic adhesive composition (1). The prepared acrylic adhesive composition (1) was applied to a polyethylene terephthalate film (38 μm thick) as a base material and heated at 130°C for 20 seconds to form an adhesive layer with a thickness of 10 μm. Next, a release liner (25 μm thick, polyethylene terephthalate film with silicone treatment on one side) was laminated to the surface of the adhesive layer to obtain a surface protection film (1) in which the surface of the adhesive layer was protected by the release liner. The results are shown in Table 1.

[0112] [Example 2] Except for using 0.075 parts by weight of the product name "Aqualon KH-10" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant, the procedure was carried out in the same manner as in Example 1 to obtain an acrylic adhesive composition (2) and a surface protective film (2). The results are shown in Table 1.

[0113] [Example 3] Except for changing the amount of "Aqualon KH-10" used to 0.100 parts by weight, the procedure was carried out in the same manner as in Example 2 to obtain an acrylic adhesive composition (3) and a surface protective film (3). The results are shown in Table 1.

[0114] [Example 4] Except for changing the amount of "Aqualon KH-10" used to 0.125 parts by weight, the procedure was carried out in the same manner as in Example 2 to obtain an acrylic adhesive composition (4) and a surface protective film (4). The results are shown in Table 1.

[0115] [Example 5] Except for changing the amount of "Aqualon KH-10" used to 0.150 parts by weight, the procedure was carried out in the same manner as in Example 2 to obtain an acrylic adhesive composition (5) and a surface protective film (5). The results are shown in Table 1.

[0116] [Example 6] Except for changing the amount of "Aqualon KH-10" used to 0.175 parts by weight, the procedure was carried out in the same manner as in Example 2 to obtain an acrylic adhesive composition (6) and a surface protective film (6). The results are shown in Table 1.

[0117] [Example 7] Except for changing the amount of "Aqualon KH-10" used to 0.200 parts by weight, the procedure was carried out in the same manner as in Example 2 to obtain an acrylic adhesive composition (7) and a surface protective film (7). The results are shown in Table 1.

[0118] [Example 8] Except for changing the amount of "Aqualon KH-10" used to 0.250 parts by weight, the procedure was carried out in the same manner as in Example 2 to obtain an acrylic adhesive composition (8) and a surface protective film (8). The results are shown in Table 1.

[0119] [Example 9] Except for changing the amount of "Aqualon KH-10" used to 0.300 parts by weight, the procedure was carried out in the same manner as in Example 2 to obtain an acrylic adhesive composition (8) and a surface protective film (8). The results are shown in Table 1.

[0120] [Example 10] Except for changing the amount of "Aqualon KH-10" used to 0.350 parts by weight, the procedure was carried out in the same manner as in Example 2 to obtain an acrylic adhesive composition (10) and a surface protective film (10). The results are shown in Table 1.

[0121] [Example 11] The acrylic polymer solution obtained in Production Example 1 was diluted to a concentration of 29% by weight by adding ethyl acetate. To 100 parts by weight of solids in this solution, 0.125 parts by weight of the product name "Aqualon KH-10" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added as a surfactant, 4 parts by weight of isocyanurate of hexamethylene diisocyanate (product name "Coronate HX", manufactured by Tosoh Corporation) was added as a crosslinking agent, and 0.03 parts by weight of dibutyltin dilaurate (product name "OL-1", manufactured by Tokyo Fine Chemical Co., Ltd.) was added as a crosslinking catalyst. Furthermore, 3 parts by weight of acetylacetone was added as a crosslinking retarder relative to the total amount of solvent. The mixture was then mixed and stirred to prepare the acrylic adhesive composition (11). The prepared acrylic adhesive composition (11) was applied onto a polyethylene terephthalate film (38 μm thick) as a base material and heated at 130°C for 20 seconds to form an adhesive layer with a thickness of 20 μm. Next, a release liner (25 μm thick, polyethylene terephthalate film with silicone treatment on one side) was laminated to the surface of the adhesive layer to obtain a surface protection film (11) in which the surface of the adhesive layer was protected by the release liner. The results are shown in Table 1.

[0122] [Example 12] Except for changing the amount of "Aqualon KH-10" used to 0.150 parts by weight, the procedure was carried out in the same manner as in Example 11 to obtain an acrylic adhesive composition (12) and a surface protective film (12). The results are shown in Table 1.

[0123] [Example 13] Except for changing the amount of "Aqualon KH-10" used to 0.175 parts by weight, the procedure was carried out in the same manner as in Example 11 to obtain an acrylic adhesive composition (13) and a surface protective film (13). The results are shown in Table 1.

[0124] [Comparative Example 1] Except for using 0.300 parts by weight of the product name "Aqualon HS-10" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant, the procedure was carried out in the same manner as in Example 1 to obtain an acrylic adhesive composition (C1) and a surface protective film (C1). The results are shown in Table 1.

[0125] [Comparative Example 2] Except for using 0.300 parts by weight of the product name "Aqualon AR-20" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant, the procedure was carried out in the same manner as in Example 1 to obtain an acrylic adhesive composition (C2) and a surface protective film (C2). The results are shown in Table 1.

[0126] [Comparative Example 3] Except for using 0.300 parts by weight of the product name "ADEKA AREA SOAP SR-20" (manufactured by ADEKA Corporation) as the surfactant, the procedure was carried out in the same manner as in Example 1 to obtain an acrylic adhesive composition (C3) and a surface protective film (C3). The results are shown in Table 1.

[0127] [Comparative Example 4] Except for using 0.300 parts by weight of the product name "Latemul E-118B" (manufactured by Kao Corporation) as a surfactant, the procedure was carried out in the same manner as in Example 1 to obtain an acrylic adhesive composition (C4) and a surface protective film (C4). The results are shown in Table 1.

[0128] [Comparative Example 5] Except for using 0.200 parts by weight of the product name "Aqualon HS-10" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant, the procedure was carried out in the same manner as in Example 11 to obtain an acrylic adhesive composition (C5) and a surface protective film (C5). The results are shown in Table 1.

[0129] [Comparative Example 6] Except for using 0.200 parts by weight of the product name "Aqualon AR-10" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant, the procedure was carried out in the same manner as in Example 11 to obtain an acrylic adhesive composition (C6) and a surface protective film (C6). The results are shown in Table 1.

[0130] [Comparative Example 7] Except for using 0.200 parts by weight of the product name "Aqualon AR-20" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant, the procedure was carried out in the same manner as in Example 11 to obtain an acrylic adhesive composition (C7) and a surface protective film (C7). The results are shown in Table 1.

[0131] [Comparative Example 8] Except for using 0.200 parts by weight of the product name "ADEKA AREA SOAP SR-20" (manufactured by ADEKA Corporation) as a surfactant, the procedure was carried out in the same manner as in Example 11 to obtain an acrylic adhesive composition (C8) and a surface protective film (C8). The results are shown in Table 1.

[0132] [Comparative Example 9] Except for using 0.200 parts by weight of the product name "Latemul E-118B" (manufactured by Kao Corporation) as a surfactant, the procedure was carried out in the same manner as in Example 11 to obtain an acrylic adhesive composition (C9) and a surface protective film (C9). The results are shown in Table 1.

[0133] [Table 1]

[0134] [Examples 14-26] For each of the surface protective films (1) to (13) obtained in Examples 1 to 13, 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 optical devices (14) to (26).

[0135] [Examples 27-39] For each of the surface protective films (1) to (13) obtained in Examples 1 to 13, 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 electronic devices (27) to (39). [Industrial applicability]

[0136] The surface protection film of the present invention can be used in any suitable application, such as in the manufacturing process of optical devices and electronic devices to prevent scratches on the surface of optical components and electronic components during processing, assembly, inspection, and transportation. [Explanation of Symbols]

[0137] 1 Base material 2. Adhesive layer 3. Peel-off liner 10 Surface protective film

Claims

1. A surface protective film having a base material and an adhesive layer, The adhesive layer is composed of an acrylic adhesive, and the acrylic adhesive is formed from an acrylic adhesive composition. The acrylic adhesive composition comprises an acrylic polymer and a surfactant (A). Surface protective film. Here, surfactant (A) is (1) It does not have an aromatic ring, (2) - (CH 2 CH 2 O) n It has a polyethylene oxide skeleton represented by - (where 5 ≤ n < 20).

2. The surface protective film according to claim 1, wherein the amount of surfactant (A) per 100 parts by weight of the acrylic polymer is 0.001 parts by weight to 10 parts by weight.

3. An optical device comprising a surface protective film according to claim 1 or 2.

4. An electronic device comprising the surface protective film according to claim 1 or 2.

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