Adhesive composition, adhesive layer, and protective film

Abstract

To provide an adhesive composition suitable for a protection film that has excellent laser processability, prevents the occurrence of debris, and has excellent inspectability in the production process, an adhesive layer formed from such an adhesive composition, and a protection film having such an adhesive layer.SOLUTION: An adhesive composition contains a base polymer, the adhesive composition containing metal oxide particles with an average primary particle size of 1 nm-300 nm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an adhesive composition. The present invention relates to an adhesive layer formed from such an adhesive composition. The present invention relates to a protective film having such an adhesive layer.

Background Art

[0002] In the division of optical members and electronic members such as manufacturing semiconductor chips by cutting and dividing semiconductor wafers, laser dicing is adopted in which a laser beam is irradiated for processing.

[0003] However, when laser dicing is performed, since the laser irradiation point becomes extremely hot, the material of the object to be processed vaporizes or the like to generate debris (condensate), and the debris adheres to the surface of the object to be processed. When such debris adheres to the object to be processed, problems such as a decrease in the quality of the manufactured product, contamination of the manufacturing line, and a decrease in the inspectability in the manufacturing process occur.

[0004] In order to solve the above problems, a method has been proposed in which a protective film made of a water-soluble resin is formed on the processing surface of the object to be processed, laser dicing is performed through the protective film, and after processing, the adhered debris is washed away together with the protective film by water washing (for example, Patent Documents 1 and 2). However, when the object to be processed is a member such as a polarizing plate or an FPC that cannot be washed with water, this method cannot be applied. In addition, pollution caused by drainage generated during water washing also becomes a problem. Furthermore, the generation of debris itself cannot be suppressed.

[0005] In addition, a method has been proposed in which a protective film containing a (meth)acrylate copolymer and a radiation-polymerizable (meth)acrylate having an unsaturated bond is formed on the processed surface of an object to be processed, laser dicing is performed through the protective film, and the protective film is cured by irradiating with ultraviolet rays after processing to remove the protective film to which debris has adhered (Patent Document 3). However, it is necessary to irradiate the object to be processed with ultraviolet rays, and there is a problem that it is difficult to apply this method to an object to be processed that is vulnerable to ultraviolet ray irradiation (such as optical members such as polarizing plates). In addition, since the protective film used in this method does not have a sufficiently low haze, problems such as a decrease in inspection performance in the manufacturing process still occur. Furthermore, the generation of debris itself cannot be suppressed.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide an adhesive composition useful for a protective film that is excellent in laser processability, suppresses the generation of debris, and is excellent in inspection performance in the manufacturing process, an adhesive layer formed from such an adhesive composition, and a protective film having such an adhesive layer.

Means for Solving the Problems

[0008] The adhesive composition of the present invention is an adhesive composition containing a base polymer, and containing metal oxide particles having an average primary particle diameter of 1 nm to 300 nm.

[0009] In one embodiment, the content ratio of the metal oxide particles with respect to 100 parts by weight of the base polymer is 0.1% by weight to 50% by weight.

[0010] In one embodiment, the metal oxide particles are silica (silicon oxide).

[0011] In one embodiment, the base polymer is at least one selected from a urethane prepolymer, a polyol, an acrylic resin, a rubber resin, and a silicone resin.

[0012] The pressure-sensitive adhesive layer of the present invention is formed from the pressure-sensitive adhesive composition of the present invention.

[0013] The protective film of the present invention has the pressure-sensitive adhesive layer of the present invention.

[0014] In one embodiment, the protective film of the present invention has a Haze of 50% or less.

Advantages of the Invention

[0015] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition useful for a protective film that is excellent in laser processability, suppresses the generation of debris, and is excellent in inspectability in the manufacturing process. Further, it is possible to provide a pressure-sensitive adhesive layer formed from such a pressure-sensitive adhesive composition. Further, it is possible to provide a protective film having such a pressure-sensitive adhesive layer.

Brief Description of the Drawings

[0016]

Figure 1

Embodiments for Carrying Out the Invention

[0017] ≪≪A. Pressure-Sensitive Adhesive Composition≫≫ The pressure-sensitive adhesive composition of the present invention contains a base polymer. The base polymer may be one kind or two or more kinds.

[0018] The pressure-sensitive adhesive composition of the present invention contains metal oxide particles having an average primary particle diameter of 1 nm to 300 nm. The metal oxide particles having an average primary particle diameter of 1 nm to 300 nm may be of one kind or two or more kinds.

[0019] As long as the pressure-sensitive adhesive composition of the present invention contains metal oxide particles having an average primary particle diameter of 1 nm to 300 nm, it may contain metal oxide particles other than the metal oxide particles within a range that does not impair the effects of the present invention. However, the content ratio of the metal oxide particles having an average primary particle diameter of 1 nm to 300 nm in all the metal oxide particles contained in the pressure-sensitive adhesive composition of the present invention is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, still more preferably 90% by weight to 100% by weight, particularly preferably 95% by weight to 100% by weight, and most preferably substantially 100% by weight.

[0020] By containing a base polymer and metal oxide particles having an average primary particle diameter of 1 nm to 300 nm, the pressure-sensitive adhesive composition of the present invention can provide a pressure-sensitive adhesive composition useful for a protective film that is excellent in laser processability, suppresses the generation of debris, and is excellent in inspectability in the manufacturing process.

[0021] In the pressure-sensitive adhesive composition of the present invention, the content of metal oxide particles relative to 100 parts by weight of the base polymer is preferably 0.1 part by weight to 50 parts by weight, more preferably 5 parts by weight to 45 parts by weight, still more preferably 10 parts by weight to 40 parts by weight, particularly preferably 15 parts by weight to 35 parts by weight, and most preferably 20 parts by weight to 35 parts by weight. If the content ratio of the metal oxide particles to the base polymer is within the above range, a pressure-sensitive adhesive composition useful for a protective film with excellent laser processability, more suppressed generation of debris, and excellent inspectability in the manufacturing process can be provided. If the content ratio of the metal oxide particles to the base polymer is too low outside the above range, there is a risk that the laser processability is insufficient and the generation of debris cannot be suppressed. If the content ratio of the metal oxide particles to the base polymer is too high outside the above range, there is a risk of an increase in the Haze value, secondary aggregation of the metal oxide particles, and large irregularities on the surface of the pressure-sensitive adhesive layer, resulting in poor adhesion.

[0022] The content ratio of the base polymer in the pressure-sensitive adhesive composition of the present invention is preferably 50% by weight to 99% by weight, more preferably 55% by weight to 90% by weight, still more preferably 60% by weight to 90% by weight, particularly preferably 65% by weight to 85% by weight, and most preferably 65% by weight to 80% by weight. If the content ratio of the base polymer in the pressure-sensitive adhesive composition of the present invention is within the above range, a pressure-sensitive adhesive composition useful for a protective film with excellent laser processability, more suppressed generation of debris, and excellent inspectability in the manufacturing process can be provided. If the content ratio of the base polymer in the pressure-sensitive adhesive composition of the present invention is too low outside the above range, there is a risk of insufficient adhesive strength and rough adhesive surface, resulting in the entrapment of air bubbles during the lamination of the protective film. If the content ratio of the base polymer in the pressure-sensitive adhesive composition of the present invention is too high outside the above range, there is a risk of insufficient laser processability.

[0023] ≪A-1. Metal Oxide Particles≫ The average primary particle diameter of the metal oxide particles is from 1 nm to 300 nm, preferably from 1 nm to 250 nm, more preferably from 1 nm to 200 nm, still more preferably from 1 nm to 175 nm, still more preferably from 1 nm to 150 nm, still more preferably from 1 nm to 100 nm, particularly preferably from 5 nm to 75 nm, and most preferably from 5 nm to 50 nm. If the average primary particle diameter of the metal oxide particles is within the above range, an adhesive composition useful for a protective film with excellent laser processability, more suppressed generation of debris, and excellent inspectability in the manufacturing process can be provided. If the average primary particle diameter of the metal oxide particles is too small outside the above range, the apparent particle size becomes coarse due to aggregation of the primary particles, and there is a risk of an increase in the Haze value and roughness of the adhesive surface, causing air bubbles to be trapped during the bonding of the protective film. If the average primary particle diameter of the metal oxide particles is too large outside the above range, there is a risk of an increase in the Haze value and roughness of the adhesive surface, causing air bubbles to be trapped during the bonding of the protective film.

[0024] As the metal oxide particles, any suitable metal oxide particles can be adopted as long as the effects of the present invention are not impaired. Examples of such metal oxide particles include silica (SiO2) particles, titanium oxide (TiO2) particles, alumina (Al2O3) particles, zirconium oxide (ZrO2) particles, cryolite (Na3AlF6) particles, ATO particles, ITO particles, bismuth oxide (Bi2O3), etc. Preferably, silica particles, titanium oxide particles, and ATO particles are mentioned, more preferably silica particles, and considering the average primary particle diameter, even more preferably silica particles.

[0025] If silica is adopted as the metal oxide particles with an average primary particle diameter of 1 nm to 300 nm, an adhesive composition useful for a protective film with excellent laser processability, more suppressed generation of debris, and excellent inspectability in the manufacturing process can be provided.

[0026] ≪A-2. Base Polymer≫ The base polymer is preferably at least one selected from urethane prepolymers, polyols, acrylic resins, rubber resins, and silicone resins. If the base polymer is at least one selected from urethane prepolymers, polyols, acrylic resins, rubber resins, and silicone resins, by incorporating it into the pressure-sensitive adhesive composition in combination with metal oxide particles having an average primary particle diameter of 1 nm to 300 nm, a pressure-sensitive adhesive composition useful for a protective film that is excellent in laser processability, further suppresses the generation of debris, and is excellent in inspectability in the manufacturing process can be provided.

[0027] <A-2-1. Urethane prepolymer> The urethane prepolymer is preferably a polyurethane polyol, more preferably a polyester polyol (a1) or a polyether polyol (a2), either alone or as a mixture of (a1) and (a2), and is reacted with an organic polyisocyanate compound (a3) in the presence or absence of a catalyst.

[0028] As the polyester polyol (a1), any suitable polyester polyol can be used. Examples of such polyester polyols (a1) include polyester polyols obtained by reacting an acid component and a glycol component. Examples of the acid component include terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, trimellitic acid, and the like. Examples of the glycol component include ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 3,3'-dimethyloleptane, polyoxyethylene glycol, polyoxypropylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, and polyol components such as glycerin, trimethylolpropane, pentaerythritol, and the like. Other examples of the polyester polyol (a1) include polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, poly(β-methyl-γ-valerolactone), and polyvalerolactone.

[0029] As for the molecular weight of the polyester polyol (a1), it can be used from low molecular weight to high molecular weight. The number average molecular weight of the polyester polyol (a1) is preferably 100 to 100,000. If the number average molecular weight is less than 100, the reactivity becomes high and there is a risk of easy gelation. If the number average molecular weight exceeds 100,000, the reactivity decreases, and furthermore, the cohesive force of the polyurethane polyol itself may become small. The amount of the polyester polyol (a1) used is preferably 0 mol% to 90 mol% among the polyols constituting the polyurethane polyol.

[0030] As the polyether polyol (a2), any suitable polyether polyol can be used. Examples of such polyether polyols (a2) include polyether polyols obtained by polymerizing oxirane compounds such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran using low molecular weight polyols such as water, propylene glycol, ethylene glycol, glycerin, and trimethylolpropane as initiators. Specific examples of such polyether polyols (a2) include polyether polyols having a functionality of 2 or more, such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol.

[0031] The molecular weight of the polyether polyol (a2) can be used from low molecular weight to high molecular weight. The molecular weight of the polyether polyol (a2) preferably has a number average molecular weight of 100 to 100,000. If the number average molecular weight is less than 100, the reactivity increases and there is a risk of gelation. If the number average molecular weight exceeds 100,000, the reactivity decreases and furthermore, the cohesive force of the polyurethane polyol itself may decrease. The amount of the polyether polyol (a2) used is preferably 0 mol% to 90 mol% in the polyols constituting the polyurethane polyol.

[0032] A part of the polyether polyol (a2) can be replaced, if necessary, with glycols such as ethylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, glycerin, trimethylolpropane, and pentaerythritol, and polyvalent amines such as ethylenediamine, N-aminoethylethanolamine, isophoronediamine, and xylylenediamine, and used in combination.

[0033] As the polyether polyol (a2), only a bifunctional polyether polyol may be used, or a polyether polyol having a number average molecular weight of 100 to 100,000 and having at least 3 or more hydroxyl groups in one molecule may be partially or entirely used. When a polyether polyol having a number average molecular weight of 100 to 100,000 and having at least 3 or more hydroxyl groups in one molecule is partially or entirely used as the polyether polyol (a2), the balance between adhesiveness and peelability can be good. In such a polyether polyol, if the number average molecular weight is less than 100, the reactivity becomes high and there is a risk of easy gelation. Also, in such a polyether polyol, if the number average molecular weight exceeds 100,000, the reactivity becomes low, and furthermore, the cohesive force of the polyurethane polyol itself may become small. The number average molecular weight of such a polyether polyol is more preferably 100 to 10,000.

[0034] As the organic polyisocyanate compound (a3), any suitable organic polyisocyanate compound can be used. Examples of such an organic polyisocyanate compound (a3) include aromatic polyisocyanates, aliphatic polyisocyanates, araliphatic polyisocyanates, alicyclic polyisocyanates, and the like.

[0035] Examples of aromatic polyisocyanates include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4',4''-triphenylmethane triisocyanate, and the like.

[0036] Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and the like.

[0037] Examples of the araliphatic polyisocyanate include ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate, and the like.

[0038] Examples of the alicyclic polyisocyanate include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, and the like.

[0039] As the organic polyisocyanate compound (a3), a trimethylolpropane adduct, a biuret obtained by reacting with water, a trimer having an isocyanurate ring, and the like can be used in combination.

[0040] As the catalyst that can be used when obtaining the polyurethane polyol, any suitable catalyst can be used. Examples of such a catalyst include tertiary amine compounds, organometallic compounds, and the like.

[0041] Examples of the tertiary amine compounds include triethylamine, triethylenediamine, 1,8-diazabicyclo(5,4,0)-undecene-7 (DBU), and the like.

[0042] Examples of the organometallic compounds include tin-based compounds and non-tin-based compounds.

[0043] Examples of the tin-based compounds include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, tin 2-ethylhexanoate, and the like.

[0044] Examples of the non-tin-based compounds include titanium-based compounds such as dibutyltitanium dichloride, tetrabutyl titanate, and butoxytitanium trichloride; lead-based compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; iron-based compounds such as iron 2-ethylhexanoate and iron acetylacetonate; cobalt-based compounds such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc-based compounds such as zinc naphthenate and zinc 2-ethylhexanoate; zirconium-based compounds such as zirconium naphthenate; and the like.

[0045] When a catalyst is used to obtain a polyurethane polyol, in a system where there are two types of polyols, namely polyester polyol and polyether polyol, due to the difference in their reactivity, in a system with a single catalyst, problems such as gelation or turbidity of the reaction solution are likely to occur. Therefore, by using two types of catalysts when obtaining a polyurethane polyol, it becomes easier to control the reaction rate, catalyst selectivity, etc., and these problems can be solved. Examples of such combinations of two types of catalysts include, for example, tertiary amine / organometallic system, tin-based / non-tin-based, tin-based / tin-based, preferably tin-based / tin-based, and more preferably a combination of dibutyltin dilaurate and tin 2-ethylhexanoate. The mixing ratio is, by weight, tin 2-ethylhexanoate / dibutyltin dilaurate is preferably less than 1, and more preferably 0.2 to 0.6. If the mixing ratio is 1 or more, there is a risk of gelation due to the balance of catalyst activity.

[0046] When a catalyst is used to obtain a polyurethane polyol, the amount of catalyst used is preferably 0.01% by weight to 1.0% by weight based on the total amount of polyester polyol (a1), polyether polyol (a2), and organic polyisocyanate compound (a3).

[0047] When a catalyst is used to obtain a polyurethane polyol, the reaction temperature is preferably less than 100 °C, and more preferably 85 °C to 95 °C. When it exceeds 100 °C, there is a risk that the reaction rate and control of the crosslinked structure will become difficult, and it may be difficult to obtain a polyurethane polyol having a predetermined molecular weight.

[0048] When obtaining a polyurethane polyol, a catalyst may not be used. In that case, the reaction temperature is preferably 100 °C or higher, and more preferably 110 °C or higher. Also, when obtaining a polyurethane polyol without a catalyst, it is preferably reacted for 3 hours or more.

[0049] As methods for obtaining a polyurethane polyol, for example, 1) a method of charging a polyester polyol, a polyether polyol, a catalyst, and an organic polyisocyanate into a flask in their total amounts, and 2) a method of charging a polyester polyol, a polyether polyol, and a catalyst into a flask and adding or dropping an organic polyisocyanate are exemplified. As a method for obtaining a polyurethane polyol, the method of 2) is preferable in terms of controlling the reaction.

[0050] When obtaining a polyurethane polyol, any suitable solvent can be used. Examples of such solvents include methyl ethyl ketone, ethyl acetate, toluene, xylene, acetone, etc. Among these solvents, toluene is preferable.

[0051] <A-2-2. Polyol> Examples of the polyol preferably include a polyester polyol, a polyether polyol, a polycaprolactone polyol, a polycarbonate polyol, and a castor oil-based polyol. More preferably, the polyol is a polyether polyol.

[0052] The polyester polyol can be obtained, for example, by an esterification reaction between a polyol component and an acid component.

[0053] Examples of the polyol component include ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, glycerin, trimethylolpropane, pentaerythritol, hexanetriol, polypropylene glycol, and the like. Examples of the acid component include succinic acid, methyl succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, dimer acid, 2-methyl-1,4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and acid anhydrides thereof.

[0054] Examples of the polyether polyol include polyether polyols obtained by addition polymerization of an alkylene oxide such as ethylene oxide, propylene oxide, or butylene oxide using water, a low molecular weight polyol (such as propylene glycol, ethylene glycol, glycerin, trimethylolpropane, pentaerythritol, etc.), bisphenols (such as bisphenol A, etc.), dihydroxybenzene (such as catechol, resorcinol, hydroquinone, etc.) as an initiator. Specifically, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like can be mentioned.

[0055] Examples of the polycaprolactone polyol include caprolactone-based polyester diols obtained by ring-opening polymerization of a cyclic ester monomer such as ε-caprolactone or σ-valerolactone.

[0056] Examples of the polycarbonate polyol include a polycarbonate polyol obtained by subjecting the above polyol component and phosgene to a polycondensation reaction; a polycarbonate polyol obtained by subjecting the above polyol component and a carbonic acid diester such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, ethyl butyl carbonate, ethylene carbonate, propylene carbonate, diphenyl carbonate, or dibenzyl carbonate to a transesterification condensation reaction; a copolymer polycarbonate polyol obtained by using two or more of the above polyol components in combination; a polycarbonate polyol obtained by subjecting the above various polycarbonate polyols and a carboxyl group-containing compound to an esterification reaction; a polycarbonate polyol obtained by subjecting the above various polycarbonate polyols and a hydroxyl group-containing compound to an etherification reaction; a polycarbonate polyol obtained by subjecting the above various polycarbonate polyols and an ester compound to a transesterification reaction; a polycarbonate polyol obtained by subjecting the above various polycarbonate polyols and a hydroxyl group-containing compound to a transesterification reaction; a polyester-based polycarbonate polyol obtained by subjecting the above various polycarbonate polyols and a dicarboxylic acid compound to a polycondensation reaction; a copolymer polyether-based polycarbonate polyol obtained by copolymerizing the above various polycarbonate polyols and an alkylene oxide; and the like.

[0057] Examples of the castor oil-based polyol include a castor oil-based polyol obtained by reacting a castor oil fatty acid with the above polyol component. Specifically, for example, a castor oil-based polyol obtained by reacting a castor oil fatty acid with polypropylene glycol can be mentioned.

[0058] The number average molecular weight Mn of the polyol is preferably from 300 to 100,000, more preferably from 400 to 75,000, still more preferably from 450 to 50,000, and particularly preferably from 500 to 30,000. When the number average molecular weight Mn of the polyol is within the above range, by combining such a base polymer with metal oxide particles having an average primary particle diameter of 1 nm to 300 nm and including them in the pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition useful for a protective film with excellent laser processability, more suppressed debris generation, and excellent inspectability in the manufacturing process can be provided. Further, the protective film of the present invention can suppress delamination over time.

[0059] As the polyol, preferably, a polyol (A1) having 3 OH groups and a number average molecular weight Mn of 300 to 100,000 is contained. The polyol (A1) may be only one kind or two or more kinds.

[0060] The content ratio of the polyol (A1) in the polyol is preferably 5% by weight or more, more preferably 25% by weight to 100% by weight, and still more preferably 50% by weight to 100% by weight. When the content ratio of the polyol (A1) in the polyol is within the above range, by combining such a base polymer with metal oxide particles having an average primary particle diameter of 1 nm to 300 nm and including them in the pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition useful for a protective film with excellent laser processability, more suppressed debris generation, and excellent inspectability in the manufacturing process can be provided. Further, the protective film of the present invention can suppress delamination over time.

[0061] The number average molecular weight Mn of the polyol (A1) is preferably from 1,000 to 100,000, more preferably from 1,200 to 80,000, still more preferably from 1,500 to 70,000, still more preferably from 1,750 to 50,000, particularly preferably from 1,500 to 40,000, and most preferably from 2,000 to 30,000. When the number average molecular weight Mn of the polyol (A1) is within the above range, by combining such a base polymer with metal oxide particles having an average primary particle diameter of 1 nm to 300 nm and including them in the pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition useful for a protective film with excellent laser processability, more suppressed debris generation, and excellent inspectability in the manufacturing process can be provided. Further, the protective film of the present invention can suppress delamination over time.

[0062] The polyol may contain a polyol (A2) having a number average molecular weight Mn of 20,000 or less and having three or more OH groups. The polyol (A2) may be only one kind or two or more kinds. The number average molecular weight Mn of the polyol (A2) is preferably from 100 to 20,000, more preferably from 150 to 10,000, still more preferably from 200 to 7,500, particularly preferably from 300 to 6,000, and most preferably from 300 to 5,000. When the number average molecular weight Mn of the polyol (A2) is out of the above range, in particular, there is a possibility that the increase in peel strength of the protective film of the present invention over time becomes high. Examples of the polyol (A2) preferably include a polyol having three OH groups (triol), a polyol having four OH groups (tetraol), a polyol having five OH groups (pentaol), and a polyol having six OH groups (hexaol).

[0063] The total amount of polyols having 4 OH groups (tetraols), polyols having 5 OH groups (pentaols), and polyols having 6 OH groups (hexaols) as the polyol (A2) is preferably 70% by weight or less, more preferably 60% by weight or less, still more preferably 40% by weight or less, and particularly preferably 30% by weight or less, as the content ratio in the polyol. If the content ratio of the total amount of polyols having 4 OH groups (tetraols), polyols having 5 OH groups (pentaols), and polyols having 6 OH groups (hexaols) as the polyol (A2) in the polyol is within the above range, an adhesive layer excellent in transparency can be provided, and the protective film of the present invention can further suppress peeling over time.

[0064] The content ratio of the polyol (A2) in the polyol is preferably 95% by weight or less, and more preferably 0% to 75% by weight. If the content ratio of the polyol (A2) in the polyol is within the above range, by combining such a base polymer with metal oxide particles having an average primary particle diameter of 1 nm to 300 nm and including them in the adhesive composition, an adhesive composition useful for a protective film that is more excellent in laser processability, further suppresses the generation of debris, and is more excellent in inspectability in the manufacturing process can be provided. Also, the protective film of the present invention can suppress peeling over time.

[0065] The content ratio of the polyol having 4 or more OH groups and a number average molecular weight Mn of 20,000 or less as the polyol (A2) is preferably less than 70% by weight, more preferably 60% by weight or less, still more preferably 50% by weight or less, particularly preferably 40% by weight or less, and most preferably 30% by weight or less, based on the whole polyol. If the content ratio of the polyol having 4 or more OH groups and a number average molecular weight Mn of 20,000 or less as the polyol (A2) is within the above range based on the whole polyol, an adhesive layer excellent in transparency can be provided, and the protective film of the present invention can further suppress peeling over time.

[0066] <A-2-3. Acrylic resin> As the acrylic resin, any appropriate acrylic adhesive such as a known acrylic adhesive described in, for example, JP-A-2013-241606 can be employed as long as the effects of the present invention are not impaired.

[0067] The acrylic resin may contain any appropriate components as long as the effects of the present invention are not impaired. Examples of such components include resin components other than acrylic resins, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foils, softeners, anti-aging agents, conductive agents, ultraviolet absorbers, antioxidants, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, catalysts, and the like.

[0068] <A-2-4. Rubber-based resin> As the rubber-based resin, any appropriate rubber-based adhesive such as a known rubber-based adhesive described in, for example, JP-A-2015-074771 can be employed as long as the effects of the present invention are not impaired. These may be only one kind or two or more kinds.

[0069] The rubber-based resin may contain any appropriate components as long as the effects of the present invention are not impaired. Examples of such components include resin components other than rubber-based resins, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foils, softeners, anti-aging agents, conductive agents, ultraviolet absorbers, antioxidants, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, catalysts, and the like.

[0070] <A-2-5. Silicone-based resin> As the silicone-based adhesive, any appropriate silicone-based adhesive such as a known silicone-based adhesive described in, for example, JP-A-2014-047280 can be employed as long as the effects of the present invention are not impaired. These may be only one kind or two or more kinds.

[0071] The silicone-based resin may contain any suitable components as long as the effects of the present invention are not impaired. Such components include, for example, resin components other than silicone-based resins, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foils, softeners, anti-aging agents, conductive agents, ultraviolet absorbers, antioxidants, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, catalysts, and the like.

[0072] <<A-3. Crosslinking agent>> The adhesive composition of the present invention may contain a crosslinking agent. The crosslinking agent may be only one kind or two or more kinds.

[0073] As the crosslinking agent, any suitable crosslinking agent may be employed as long as the effects of the present invention are not impaired. Such crosslinking agents include, for example, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, amine-based crosslinking agents, and the like. Preferably, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are mentioned.

[0074] Examples of isocyanate crosslinking agents typically include polyfunctional isocyanate compounds, such as lower aliphatic polyisocyanates like 1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, 1,6-hexamethylene diisocyanate; alicyclic polyisocyanates like cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate; aromatic polyisocyanates like 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate; and the like. Examples of polyfunctional isocyanate compounds also include commercially available products such as trimethylolpropane / tolylene diisocyanate adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HL"), trade name "Coronate HX" (manufactured by Nippon Polyurethane Industry Co., Ltd.), trimethylolpropane / xylylene diisocyanate adduct (manufactured by Mitsui Chemicals, Inc., trade name "Takenate 110N").

[0075] Examples of epoxy crosslinking agents typically include polyfunctional epoxy compounds, such as N,N,N’,N’-tetraglycidyl-m-xylenediamine, 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, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcin diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Commercially available products such as the product named "Tetrad C" (manufactured by Mitsubishi Gas Chemical Company, Inc.) are also included as polyfunctional epoxy compounds.

[0076] ≪A-4. Components of the Composition for Forming Urethane Resin≫ The urethane prepolymer and polyol as base polymers can each be combined with a polyfunctional isocyanate compound to be components of a composition for forming a urethane resin. By adopting the above-mentioned components as components of a composition for forming a urethane resin, such a base polymer can be combined with metal oxide particles having an average primary particle diameter of 1 nm to 300 nm and included in an adhesive composition, thereby providing an adhesive composition useful for a protective film that is excellent in laser processability, more suppresses the generation of debris, and is excellent in inspectability in the manufacturing process.

[0077] When forming a urethane-based resin, the pressure-sensitive adhesive composition of the present invention may contain, for example, resin components other than urethane-based resins, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foils, softeners, anti-aging agents, conductive agents, ultraviolet absorbers, antioxidants, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, catalysts, and other components. Such other components may be only one type or two or more types.

[0078] When forming a urethane-based resin, the pressure-sensitive adhesive composition of the present invention preferably contains deterioration inhibitors such as antioxidants, ultraviolet absorbers, and light stabilizers. By including a deterioration inhibitor in the pressure-sensitive adhesive composition of the present invention, it becomes possible to be excellent in anti-tack residue properties, such as being less likely to cause tack residue on the adherend even when stored in a heated state after the formed pressure-sensitive adhesive layer is attached to the adherend. The deterioration inhibitor may be only one type or two or more types. Particularly preferably, the deterioration inhibitor is an antioxidant.

[0079] Examples of the antioxidant include radical chain inhibitors and peroxide decomposers.

[0080] Examples of the radical chain inhibitor include phenolic antioxidants and amine antioxidants.

[0081] Examples of the peroxide decomposer include sulfur-based antioxidants and phosphorus-based antioxidants.

[0082] Examples of the phenolic antioxidant include monophenolic antioxidants, bisphenolic antioxidants, and polymer-type phenolic antioxidants.

[0083] Examples of the monophenolic antioxidant include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl) propionate, and the like.

[0084] Examples of bisphenol antioxidants include 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane, and the like.

[0085] Examples of polymeric phenolic antioxidants include 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, tocopherol, and the like.

[0086] Examples of sulfur antioxidants include dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, and the like.

[0087] Examples of phosphorus antioxidants include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, and the like.

[0088] Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, oxalic acid anilide-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, triazine-based ultraviolet absorbers, and the like.

[0089] Examples of the benzophenone-based ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4-dimethoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis(2-methoxy-4-hydroxy-5-benzoylphenyl)methane, and the like.

[0090] Examples of the benzotriazole-based ultraviolet absorber include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole, 2-[2'-hydroxy-3'-(3'',4'',5'',6''-tetrahydrophthalimidomethyl)-5'-methylphenyl]benzotriazole, 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(2'-hydroxy-5'-methacryloxyphenyl)-2H-benzotriazole, and the like.

[0091] Examples of salicylic acid-based ultraviolet absorbers include phenyl salicylate, p-tert-butylphenyl salicylate, p-octylphenyl salicylate, and the like.

[0092] Examples of cyanoacrylate-based ultraviolet absorbers include 2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate, ethyl-2-cyano-3,3'-diphenyl acrylate, and the like.

[0093] Examples of light stabilizers include hindered amine light stabilizers, ultraviolet stabilizers, and the like.

[0094] Examples of hindered amine light stabilizers include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, methyl-1,2,2,6,6-pentamethyl-4-piperidyl sebacate, and the like.

[0095] Examples of ultraviolet stabilizers include nickel bis(octylphenyl) sulfide, [2,2'-thiobis(4-tert-octylphenolate)]-n-butylamine nickel, nickel complex-3,5-di-tert-butyl-4-hydroxybenzyl-phosphoric acid monoethyl ester, nickel-dibutyldithiocarbamate, benzoate type quencher, nickel-dibutyldithiocarbamate, and the like.

[0096] Examples of urethane resins formed from a composition containing a urethane prepolymer and a polyfunctional isocyanate compound include urethane resins formed from a composition containing a polyurethane polyol as the urethane prepolymer and a polyfunctional isocyanate compound.

[0097] The urethane prepolymer may be only one kind or two or more kinds.

[0098] The polyfunctional isocyanate compound may be only one kind, or may be two or more kinds.

[0099] As the polyfunctional isocyanate compound, any suitable polyfunctional isocyanate compound that can be used in the urethanization reaction can be adopted. Examples of such polyfunctional isocyanate compounds include polyfunctional aliphatic isocyanate compounds, polyfunctional alicyclic isocyanates, polyfunctional aromatic isocyanate compounds, and the like.

[0100] Examples of the polyfunctional aliphatic isocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and the like.

[0101] Examples of the polyfunctional alicyclic isocyanate compound include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated tetramethylxylylene diisocyanate, and the like.

[0102] Examples of the polyfunctional aromatic diisocyanate compound include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, and the like.

[0103] Examples of the polyfunctional isocyanate compound include trimethylolpropane adducts of various polyfunctional isocyanate compounds as described above, biuret compounds reacted with water, and trimers having an isocyanurate ring. These may also be used in combination.

[0104] As a method for forming a polyurethane-based resin from a composition containing a urethane prepolymer and a polyfunctional isocyanate compound, any suitable production method can be adopted as long as it is a method for producing a polyurethane-based resin using the so-called "urethane prepolymer" as a raw material.

[0105] The number average molecular weight Mn of the urethane prepolymer is preferably from 3000 to 1,000,000.

[0106] In the urethane prepolymer and the polyfunctional isocyanate compound, the equivalent ratio of the NCO group to the OH group, as NCO group / OH group, is preferably 5.0 or less, more preferably from 0.01 to 4.75, still more preferably from 0.02 to 4.5, particularly preferably from 0.03 to 4.25, and most preferably from 0.05 to 4.0. When the equivalent ratio of NCO group / OH group is within the above range, by combining such a polyfunctional isocyanate compound with a base polymer and metal oxide particles having an average primary particle diameter of 1 nm to 300 nm and including them in the adhesive composition, an adhesive composition useful for a protective film with excellent laser processability, more suppressed generation of debris, and excellent inspectability in the manufacturing process can be provided.

[0107] The content ratio of the polyfunctional isocyanate compound is preferably 0.01% to 30% by weight, more preferably 0.05% to 25% by weight, still more preferably 0.1% to 20% by weight, particularly preferably 0.5% to 17.5% by weight, and most preferably 1% to 15% by weight, based on the urethane prepolymer. If the content ratio of the polyfunctional isocyanate compound is within the above range, by incorporating such an amount of the polyfunctional isocyanate in combination with a base polymer and metal oxide particles having an average primary particle diameter of 1 nm to 300 nm into the pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition useful for a protective film with excellent laser processability, more suppressed debris generation, and excellent inspectability in the manufacturing process can be provided.

[0108] <A-4-2. Urethane resin formed from a composition containing a polyol and a polyfunctional isocyanate compound> The urethane resin formed from a composition containing a polyol and a polyfunctional isocyanate compound is specifically preferably a urethane resin obtained by curing a composition containing a polyol and a polyfunctional isocyanate compound.

[0109] The polyol may be only one kind or two or more kinds.

[0110] The polyfunctional isocyanate compound may be only one kind or two or more kinds.

[0111] As the polyfunctional isocyanate compound, those described above can be cited.

[0112] In the polyol and polyfunctional isocyanate compound, the equivalent ratio of the NCO group to the OH group, expressed as NCO group / OH group, is preferably 5.0 or less, more preferably 0.1 to 3.0, still more preferably 0.2 to 2.5, particularly preferably 0.3 to 2.25, and most preferably 0.5 to 2.0. If the equivalent ratio of the NCO group / OH group is within the above range, by incorporating such a polyfunctional isocyanate compound, a base polymer, and metal oxide particles with an average primary particle diameter of 1 nm to 300 nm into the pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition useful for a protective film with excellent laser processability, more suppressed debris generation, and excellent inspectability in the manufacturing process can be provided.

[0113] The content ratio of the polyfunctional isocyanate compound is preferably 1.0% by weight to 30% by weight, more preferably 1.5% by weight to 27% by weight, still more preferably 2.0% by weight to 25% by weight, particularly preferably 2.3% by weight to 23% by weight, and most preferably 2.5% by weight to 20% by weight with respect to the polyol. If the content ratio of the polyfunctional isocyanate compound is within the above range, by incorporating such an amount of the polyfunctional isocyanate in combination with a base polymer and metal oxide particles with an average primary particle diameter of 1 nm to 300 nm into the pressure-sensitive adhesive composition, a pressure-sensitive adhesive composition useful for a protective film with excellent laser processability, more suppressed debris generation, and excellent inspectability in the manufacturing process can be provided.

[0114] The polyurethane-based resin is specifically preferably formed by curing a composition containing a polyol and a polyfunctional isocyanate compound. As a method for curing a composition containing a polyol and a polyfunctional isocyanate compound to form a urethane-based resin, any appropriate method can be adopted within the range that does not impair the effects of the present invention, such as a urethanization reaction method using bulk polymerization or solution polymerization.

[0115] In order to cure a composition containing a polyol and a polyfunctional isocyanate compound, a catalyst is preferably used. Examples of such catalysts include organometallic compounds and tertiary amine compounds.

[0116] Examples of organometallic compounds include iron-based compounds, tin-based compounds, titanium-based compounds, zirconium-based compounds, lead-based compounds, cobalt-based compounds, zinc-based compounds, etc. Among these, iron-based compounds and tin-based compounds are preferred in terms of reaction rate and pot life of the adhesive layer.

[0117] Examples of iron-based compounds include iron acetylacetonate, iron 2-ethylhexanoate, etc.

[0118] Examples of tin-based compounds include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin maleate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, tributyltin methoxide, tributyltin acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, dioctyltin dilaurate, tributyltin chloride, tributyltin trichloroacetate, tin 2-ethylhexanoate, etc.

[0119] Examples of titanium-based compounds include dibutyltitanium dichloride, tetrabutyl titanate, butoxytitanium trichloride, etc.

[0120] Examples of zirconium-based compounds include zirconium naphthenate, zirconium acetylacetonate, etc.

[0121] Examples of lead-based compounds include lead oleate, lead 2-ethylhexanoate, lead benzoate, lead naphthenate, etc.

[0122] Examples of cobalt-based compounds include cobalt 2-ethylhexanoate, cobalt benzoate, etc.

[0123] Examples of the zinc compound include zinc naphthenate and zinc 2-ethylhexanoate.

[0124] Examples of the tertiary amine compound include triethylamine, triethylenediamine, 1,8-diazabicyclo-(5,4,0)-undecene-7, and the like.

[0125] The catalyst may be only one kind or two or more kinds. Further, the catalyst and a crosslinking retarder may be used in combination. The amount of the catalyst is preferably 0.005% by weight to 1.00% by weight, more preferably 0.01% by weight to 0.75% by weight, still more preferably 0.01% by weight to 0.50% by weight, and particularly preferably 0.01% by weight to 0.20% by weight with respect to the polyol. When the amount of the catalyst is within the above range, it is possible to provide a pressure-sensitive adhesive composition useful for a protective film that is excellent in laser processability, further suppresses the generation of debris, and is excellent in inspectability in the manufacturing process.

[0126] ≪A-5. Fatty Acid Ester≫ The pressure-sensitive adhesive composition of the present invention may contain a fatty acid ester. The fatty acid ester may be only one kind or two or more kinds. By the pressure-sensitive adhesive composition of the present invention containing a fatty acid ester, it is possible to provide a pressure-sensitive adhesive composition useful for a protective film that is excellent in laser processability, further suppresses the generation of debris, and is excellent in inspectability in the manufacturing process.

[0127] The number average molecular weight Mn of the fatty acid ester is preferably 100 to 800, more preferably 150 to 750, still more preferably 200 to 700, particularly preferably 200 to 650, and most preferably 200 to 600. When the number average molecular weight Mn of the fatty acid ester is within the above range, it is possible to provide a pressure-sensitive adhesive composition useful for a protective film that is excellent in laser processability, further suppresses the generation of debris, and is excellent in inspectability in the manufacturing process.

[0128] As the fatty acid ester, any appropriate fatty acid ester can be adopted as long as the effects of the present invention are not impaired. Examples of such fatty acid esters include polyoxyethylene bisphenol A laurate, butyl stearate, 2-ethylhexyl palmitate, 2-ethylhexyl stearate, behenic acid monoglyceride, cetyl 2-ethylhexanoate, isopropyl myristate, isopropyl palmitate, cholesteryl isostearate, lauryl methacrylate, methyl coconut fatty acid, methyl laurate, methyl oleate, methyl stearate, myristyl myristate, octyldodecyl myristate, pentaerythritol monooleate, pentaerythritol monostearate, pentaerythritol tetrapalmitate, stearyl stearate, isotridecyl stearate, triglyceride 2-ethylhexanoate, butyl laurate, octyl oleate, and the like.

[0129] When the pressure-sensitive adhesive composition of the present invention contains a fatty acid ester, the content ratio of the fatty acid ester is preferably 0.01 part by weight to 50 parts by weight, more preferably 0.05 part by weight to 45 parts by weight, still more preferably 0.1 part by weight to 40 parts by weight, still more preferably 0.3 part by weight to 35 parts by weight, still more preferably 0.5 part by weight to 30 parts by weight, particularly preferably 0.5 part by weight to 25 parts by weight, and most preferably 0.5 part by weight to 20 parts by weight, based on 100 parts by weight of the base polymer. If the content ratio of the fatty acid ester is within the above range based on 100 parts by weight of the base polymer, a pressure-sensitive adhesive composition excellent in laser processability, more suppressing the generation of debris, and excellent in inspectability in the manufacturing process can be provided.

[0130] ≪A-6. Ionic liquid≫ The pressure-sensitive adhesive composition of the present invention may contain an ionic liquid containing a fluoro organic anion. By including an ionic liquid containing a fluoro organic anion in the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive composition having extremely excellent antistatic properties can be provided. Such an ionic liquid may be only one kind or two or more kinds.

[0131] If the pressure-sensitive adhesive composition of the present invention contains an ionic liquid containing a fluoro organic anion, a pressure-sensitive adhesive composition with extremely excellent antistatic properties can be provided. For example, the adhesion of generated debris can be effectively suppressed.

[0132] In the present invention, the ionic liquid means a molten salt (ionic compound) that is liquid at 25°C.

[0133] As the ionic liquid, any appropriate ionic liquid can be adopted as long as it does not impair the effects of the present invention as long as it is an ionic liquid containing a fluoro organic anion. Such an ionic liquid is preferably an ionic liquid composed of a fluoro organic anion and an onium cation. By adopting an ionic liquid composed of a fluoro organic anion and an onium cation as the ionic liquid, a pressure-sensitive adhesive composition with extremely excellent antistatic properties can be provided.

[0134] As the onium cation that can constitute the ionic liquid, any appropriate onium cation can be adopted as long as it does not impair the effects of the present invention. Such an onium cation is preferably at least one selected from a nitrogen-containing onium cation, a sulfur-containing onium cation, and a phosphorus-containing onium cation. By selecting these onium cations, a pressure-sensitive adhesive composition with extremely excellent antistatic properties can be provided.

[0135] Commercially available ionic liquids may be used, but they can also be synthesized as follows. The synthesis method of the ionic liquid is not particularly limited as long as the target ionic liquid can be obtained. Generally, methods such as the halide method, hydroxide method, acid ester method, complex formation method, and neutralization method as described in the literature "Ionic Liquids - The Forefront and Future of Development -" (published by CMC Publishing Co., Ltd.) are used.

[0136] The blending amount of the ionic liquid cannot be generally defined as it varies depending on the compatibility between the polymer to be used and the ionic liquid. Generally, however, it is preferably 0.001 to 50 parts by weight, more preferably 0.01 to 40 parts by weight, still more preferably 0.01 to 30 parts by weight, particularly preferably 0.01 to 20 parts by weight, and most preferably 0.01 to 10 parts by weight, based on 100 parts by weight of the base polymer. By adjusting the blending amount of the ionic liquid within the above range, an adhesive composition with extremely excellent antistatic properties can be provided. If the blending amount of the ionic liquid is less than 0.01 part by weight, sufficient antistatic properties may not be obtained. If the blending amount of the ionic liquid exceeds 50 parts by weight, the contamination of the adherend tends to increase.

[0137] ≪A-7. Fluorine-based Additive≫ The adhesive composition of the present invention may contain a fluorine-based additive. The fluorine-based additive may be only one kind or two or more kinds.

[0138] As the fluorine-based additive, any suitable fluorine-based additive can be employed as long as the effects of the present invention are not impaired. Examples of such fluorine-based additives preferably include at least one selected from fluorine-containing compounds, hydroxyl group-containing fluorine-based compounds, and crosslinkable functional group-containing fluorine-based compounds.

[0139] Examples of the fluorine-containing compound include a compound having a fluoroaliphatic hydrocarbon skeleton, a fluorine-containing organic compound obtained by copolymerizing an organic compound and a fluorine compound, and a fluorine-containing compound containing an organic compound. Examples of the fluoroaliphatic hydrocarbon skeleton include fluoro C1-C10 alkanes such as fluoromethane, fluoroethane, fluoropropane, fluoroisopropane, fluorobutane, fluoroisobutane, fluorot-butane, fluoropentane, and fluorohexane.Examples of such fluorine-containing compounds include commercially available leveling agents such as those in the Surflon series manufactured by AGC Seimi Chemical Co., Ltd. (such as "S-242", "S-243", "S-420", "S-611", "S-651", "S-386", etc.), those in the BYK series manufactured by BYK Chemie Japan Co., Ltd. (such as "BYK-340", etc.), those in the AC series manufactured by Algin Chemie (such as "AC 110a", "AC 100a", etc.), those in the Megafac series manufactured by DIC Corporation (such as "Megafac F-114", "Megafac F-410", "Megafac F-444", "Megafac EXP TP-2066", "Megafac F-430", "Megafac F-472SF", "Megafac F-477", "Megafac F-552", "Megafac F-553", "Megafac F-554", "Megafac F-555", "Megafac R-94", "Megafac RS-72-K", "Megafac RS-75", "Megafac F-556", "Megafac EXP TF-1367", "Megafac EXP TF-1437", "Megafac F-558", "Megafac EXP TF-1537", etc.), those in the FC series manufactured by Sumitomo 3M Limited (such as "FC-4430", "FC-4432", etc.), those in the Ftergent series manufactured by Neos Co., Ltd. (such as "Ftergent 100", "Ftergent 100C", "Ftergent 110", "Ftergent 150", "Ftergent 150CH", "Ftergent A-K", "Ftergent 501", "Ftergent 250", "Ftergent 251", "Ftergent 222F", "Ftergent 208G", "Ftergent 300", "Ftergent 310", "Ftergent 400SW", etc.), and those in the PF series manufactured by Kitamura Chemical Industry Co., Ltd. (such as "PF-136A", "PF-156A", "PF-151N", "PF-636", "PF-6320", "PF-656", "PF-6520", "PF-651", "PF-652", "PF-3320", etc.).

[0140] As the hydroxyl group-containing fluorine compound, for example, conventionally known resins can be used. For example, hydroxyl group-containing fluorine resins described in International Publication No. 94 / 06870 pamphlet, JP-A-8-12921, JP-A-10-72569, JP-A-4-275379, International Publication No. 97 / 11130 pamphlet, International Publication No. 96 / 26254 pamphlet, etc. can be mentioned. Other hydroxyl group-containing fluorine resins include, for example, fluoroolefin copolymers described in JP-A-8-231919, JP-A-10-265731, JP-A-10-204374, JP-A-8-12922, etc. In addition, copolymers of compounds having a fluorinated alkyl group in a hydroxyl group-containing compound, fluorine-containing organic compounds obtained by copolymerizing a fluorine-containing compound with a hydroxyl group-containing compound, fluorine-containing compounds containing a hydroxyl group-containing organic compound, etc. can be mentioned. As such hydroxyl group-containing fluorine compounds, as commercially available products, for example, trade names such as "Lumiflon" (manufactured by Asahi Glass Co., Ltd.), "Cefral Coat" (manufactured by Central Glass Co., Ltd.), "Zafron" (manufactured by Toagosei Co., Ltd.), "Zefflu" (manufactured by Daikin Industries, Ltd.), "MegaFac F-571", "Fluonate" (manufactured by DIC Corporation), etc. can be mentioned.

[0141] As the crosslinkable functional group-containing fluorine compound, for example, carboxylic acid compounds having a fluorinated alkyl group such as perfluorooctanoic acid, copolymers of compounds having a fluorinated alkyl group in a crosslinkable functional group-containing compound, fluorine-containing organic compounds obtained by copolymerizing a fluorine-containing compound with a crosslinkable functional group-containing compound, fluorine-containing compounds containing a crosslinkable functional group-containing compound, etc. can be mentioned. As such crosslinkable functional group-containing fluorine compounds, as commercially available products, for example, trade names such as "MegaFac F-570", "MegaFac RS-55", "MegaFac RS-56", "MegaFac RS-72-K", "MegaFac RS-75", "MegaFac RS-76-E", "MegaFac RS-76-NS", "MegaFac RS-78", "MegaFac RS-90" (manufactured by DIC Corporation), etc. can be mentioned.

[0142] ≪A-8. Other Components≫ The pressure-sensitive adhesive composition of the present invention may contain any suitable other components as long as the effects of the present invention are not impaired. Such other components may be only one kind or two or more kinds. Examples of such other components include other resin components, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foils, softeners, anti-aging agents, conductive agents, ultraviolet absorbers, antioxidants, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, catalysts, and the like.

[0143] ≪≪B. Pressure-sensitive adhesive layer≫≫ The pressure-sensitive adhesive layer of the present invention is formed from the pressure-sensitive adhesive composition of the present invention. The pressure-sensitive adhesive layer is composed of a pressure-sensitive adhesive.

[0144] The pressure-sensitive adhesive layer can be formed by any suitable method. Examples of such methods include a method of directly applying (typically coating) the pressure-sensitive adhesive composition of the present invention to a substrate and drying it to form a pressure-sensitive adhesive layer (direct method), a method of applying the pressure-sensitive adhesive composition of the present invention to a surface with good releasability (for example, the surface of a release liner, the back surface of a release-treated support substrate, etc.), drying it to form a pressure-sensitive adhesive layer on the surface, and transferring the pressure-sensitive adhesive layer to a substrate (transfer method).

[0145] Examples of the coating method include a roll coating method, a gravure coating method, a reverse coating method, a kiss coating method, a dip coating method, a bar coating method, a roll brush method, a spray coating method, an air knife coating method, an extrusion coating method using a die coater, and the like.

[0146] From the viewpoints of promoting cross-linking reaction and improving production efficiency, etc., the drying of the pressure-sensitive adhesive composition of the present invention when forming the pressure-sensitive adhesive layer is preferably carried out under heating. The temperature of such heating is preferably 40°C to 150°C, more preferably 40°C to 120°C, still more preferably 50°C to 120°C, and particularly preferably 70°C to 100°C.

[0147] When forming the adhesive layer, the drying time of the adhesive composition of the present invention may be, for example, about several tens of seconds to several minutes (for example, preferably within 5 minutes, more preferably 30 seconds to 2 minutes). Thereafter, an additional drying step may be provided as necessary.

[0148] The adhesive layer is typically formed continuously, but depending on the purpose and application, it may be formed in a regular or random pattern such as dots or stripes.

[0149] The thickness of the adhesive layer is preferably 1 μm to 150 μm, more preferably 2 μm to 140 μm, still more preferably 3 μm to 130 μm, still more preferably 4 μm to 120 μm, still more preferably 5 μm to 100 μm, still more preferably 10 μm to 90 μm, particularly preferably 20 μm to 85 μm, and most preferably 30 μm to 80 μm.

[0150] Since the adhesive layer of the present invention is formed from the adhesive composition of the present invention, the Haze is preferably 50% or less, more preferably 30% or less, still more preferably 20%, particularly preferably 10% or less, and most preferably 5% or less. If the Haze of the adhesive layer of the present invention is within the above range, the protective film of the present invention can be excellent in inspectability in the manufacturing process.

[0151] ≪≪C. Protective Film≫≫ The protective film of the present invention has the adhesive layer of the present invention. The protective film of the present invention may be provided with any other suitable member as long as the effect of the present invention is not impaired as long as it has the adhesive layer of the present invention. Typically, the protective film of the present invention has a base material layer and an adhesive layer.

[0152] It is preferable that an optional appropriate release liner (sometimes referred to as a release sheet or a separator) provided for protection until use on the adhesive layer or its surface is the outermost layer on one side.

[0153] By adopting a specific adhesive layer, the protective film of the present invention can provide a protective film with excellent laser processability, suppressed debris generation, and excellent inspectability in the manufacturing process.

[0154] FIG. 1 is a schematic cross-sectional view of a protective film according to an embodiment of the present invention. In FIG. 1, the protective film 100 includes a base material layer 10 and an adhesive layer 20. In FIG. 1, the base material layer 10 and the adhesive layer 20 are directly laminated. Note that FIG. 1 is only a schematic cross-sectional view of a protective film according to an embodiment of the present invention, and for example, it may have any other appropriate layer as long as the effects of the present invention are not impaired.

[0155] In FIG. 1, on the surface of the adhesive layer 20 opposite to the base material layer 10, an arbitrary appropriate release liner (which may also be referred to as a release sheet or a separator) may be provided for protection until use (not shown). 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. 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, an ethylene-vinyl acetate copolymer film, and the like. The plastic film as the liner base material is preferably a polyethylene film.

[0156] The thickness of the release liner is preferably 1 μm to 500 μm, more preferably 3 μm to 450 μm, still more preferably 5 μm to 400 μm, and particularly preferably 10 μm to 300 μm.

[0157] The thickness of the protective film is preferably 5 μm to 500 μm, more preferably 10 μm to 450 μm, still more preferably 15 μm to 400 μm, and particularly preferably 20 μm to 300 μm.

[0158] The protective film of the present invention can be produced by any suitable method. Such production methods include, for example, (1) A method of applying a solution or a hot melt of a material for forming the adhesive layer onto the base material layer, (2) A method of transferring an adhesive layer formed by applying a solution or a hot melt of a material for forming the adhesive layer onto a separator onto the base material layer, (3) A method of extruding and forming and applying a material for forming the adhesive layer onto the base material layer, (4) A method of extruding the base material layer and the adhesive layer in two or more layers, (5) A method of single-layer laminating the adhesive layer onto the base material layer or a method of two-layer laminating the adhesive layer together with a laminate layer, (6) A method of two-layer or multi-layer laminating the adhesive layer and a base material layer forming material such as a film or a laminate layer, etc., and can be carried out according to any suitable production method.

[0159] Examples of the coating method include a roll coating method, a gravure coating method, a reverse coating method, a kiss coating method, a dip coating method, a bar coating method, a roll brush method, a spray coating method, an air knife coating method, an extrusion coating method using a die coater, etc.

[0160] Since the protective film of the present invention has the adhesive layer of the present invention formed from the adhesive composition of the present invention, by selecting an appropriate base material layer, the Haze is preferably 50% or less, more preferably 30% or less, still more preferably 20% or less, particularly preferably 10% or less, and most preferably 5% or less. If the Haze of the protective film of the present invention is within the above range, the protective film of the present invention can be excellent in inspection properties in the manufacturing process.

[0161] ≪C-1. Base material layer≫ The substrate layer may be only one layer or two or more layers. The substrate layer may be stretched.

[0162] The thickness of the substrate layer is preferably from 4 μm to 450 μm, more preferably from 8 μm to 400 μm, still more preferably from 12 μm to 350 μm, and particularly preferably from 16 μm to 250 μm.

[0163] For the surface of the substrate layer where the adhesive layer is not provided, for the purpose of forming a wound body that can be easily rewound, for example, fatty acid amide, polyethyleneimine, long-chain alkyl-based additives, etc. can be added to the substrate layer for release treatment, or a coating layer composed of any suitable release agent such as silicone-based, long-chain alkyl-based, fluorine-based, etc. can be provided.

[0164] As the material of the substrate layer, any suitable material can be adopted according to the application. For example, plastics, paper, metal films, non-woven fabrics, etc. may be mentioned. Preferably, it is plastics. That is, the substrate layer is preferably a plastic film. The substrate layer may be composed of one kind of material or two or more kinds of materials. For example, it may be composed of two or more kinds of plastics.

[0165] Examples of the plastic include polyester resins, polyamide resins, polyolefin resins, cycloolefin resins, etc. Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc. Examples of the polyolefin resin include homopolymers of olefin monomers, copolymers of olefin monomers, etc. Specifically, examples of the polyolefin resin include homopolypropylene; propylene copolymers such as block, random, and graft types having an ethylene component as a copolymer component; reactor TPO; ethylene polymers such as low density, high density, linear low density, and ultra-low density; ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ethylene-methyl acrylate copolymers, ethylene-ethyl acrylate copolymers, ethylene-butyl acrylate copolymers, ethylene-methacrylic acid copolymers, ethylene-methyl methacrylate copolymers, etc.; and the like.

[0166] By selecting an appropriate base material layer, the Haze of the protective film of the present invention is preferably 50% or less, more preferably 25%, still more preferably 10% or less, particularly preferably 7.5% or less, and most preferably 5% or less. If the Haze of the protective film of the present invention is within the above range, the protective film of the present invention can be excellent in inspection properties in the manufacturing process. Examples of the material of such a base material layer preferably include polyester resins and cycloolefin resins.

[0167] The base material layer may contain any appropriate additive as necessary. Examples of the additive that can be contained in the base material layer include antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, fillers, pigments, etc. The type, number, and amount of the additive that can be contained in the base material layer can be appropriately set according to the purpose. In particular, when the material of the base material layer is plastic, it is preferable to contain some of the above additives for the purpose of preventing deterioration and the like. From the viewpoint of improving weather resistance and the like, particularly preferable examples of the additive include antioxidants, ultraviolet absorbers, light stabilizers, and fillers.

[0168] As the antioxidant, any suitable antioxidant can be adopted. Examples of such antioxidants include phenolic antioxidants, phosphorus-based processing heat stabilizers, lactone-based processing heat stabilizers, sulfur-based heat stabilizers, phenol-phosphorus-based antioxidants, and the like. The content ratio of the antioxidant is preferably 1% by weight or less, more preferably 0.5% by weight or less, and still more preferably 0.01% to 0.2% by weight, based on the base resin of the base material layer (when the base material layer is a blend, the blend is the base resin).

[0169] As the ultraviolet absorber, any suitable ultraviolet absorber can be adopted. Examples of such ultraviolet absorbers include benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and the like. The content ratio of the ultraviolet absorber is preferably 2% by weight or less, more preferably 1% by weight or less, and still more preferably 0.01% to 0.5% by weight, based on the base resin forming the base material layer (when the base material layer is a blend, the blend is the base resin).

[0170] As the light stabilizer, any suitable light stabilizer can be adopted. Examples of such light stabilizers include hindered amine-based light stabilizers, benzoate-based light stabilizers, and the like. The content ratio of the light stabilizer is preferably 2% by weight or less, more preferably 1% by weight or less, and still more preferably 0.01% to 0.5% by weight, based on the base resin forming the base material layer (when the base material layer is a blend, the blend is the base resin).

[0171] As the filler, any suitable filler can be adopted. Examples of such fillers include inorganic fillers. Specific examples of the inorganic filler include carbon black, titanium oxide, zinc oxide, and the like. The content ratio of the filler is preferably 20% by weight or less, more preferably 10% by weight or less, and still more preferably 0.01% by weight to 10% by weight based on the base resin forming the base material layer (when the base material layer is a blend, the blend is the base resin).

[0172] Furthermore, as additives, for the purpose of imparting antistatic properties, surfactants, inorganic salts, polyhydric alcohols, metal compounds, inorganic-based, low molecular weight-based, and high molecular weight-based antistatic agents such as carbon are also preferably mentioned. In particular, from the viewpoints of contamination and maintaining adhesiveness, high molecular weight-based antistatic agents and carbon are preferable.

Examples

[0173] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples in any way. The test and evaluation methods in the examples and the like are as follows. In addition, when "parts" are described, it means "parts by weight" unless otherwise specified, and when "%" is described, it means "% by weight" unless otherwise specified.

[0174] <Evaluation of Processability> (Irradiation conditions of laser light) The laser light irradiation apparatus used is as follows. Laser light source: Carbon dioxide laser Laser wavelength: 10.6 μm Spot diameter: 150 μm Scanning speed: 400 mm / sec Power: 55 W (Evaluation) A protective film was laminated on polyimide (Kapton 200H, manufactured by Toray DuPont), cut into a 25 mm × 35 mm square under the above laser light irradiation conditions, the cut cross-section of the processed sample was pressed against glass, and it was regarded as defective when the tack was large and good when no tack was felt.

[0175] <Evaluation of debris generation suppression effect> The processed sample described above was observed from the laser incident side with a laser microscope (VK-9500, manufactured by Keyence Corporation) at a magnification of 50 times to observe the surface of the laser incident side of the processed end. At this time, the brightness of the image was set to 12 dB, and a range of 280 μm × 150 μm from the processed end was photographed. The photographed image was binarized using "Matrox inspector 9.0" (manufactured by Canon IT Solutions Inc.), and the area occupied by black dots (debris) was calculated in the threshold range of 0 to 135, and the debris generation suppression effect was judged according to the following evaluation criteria. Ratio of black dot (debris) area is 3.00% or less: Suppression effect is ○ Ratio of black dot (debris) area exceeds 3.00% and is 4.20% or less: Suppression effect is △ Ratio of black dot (debris) area exceeds 4.20%: Suppression effect is ×

[0176] <Measurement of total light transmittance and haze> The total light transmittance and haze were measured at room temperature (23°C) by attaching the protective film to blue plate glass (manufactured by Matsunami Glass Industry Co., Ltd.) and using a haze measuring device (HM-150N, manufactured by Murakami Color Research Laboratory). The measurement was repeated 3 times, and the average value was used as the measured value.

[0177] 〔Production Example 1〕 An experimental apparatus for polymerization equipped with a 1L round-bottom separable flask, a separable cover, a separatory funnel, a thermometer, a nitrogen inlet tube, a Liebig condenser, a vacuum seal, a stir bar, and stirring blades was charged with 150 g of polypropylene glycol (product name "Sunnex PP-2000", manufactured by Sanyo Chemical Industries, Ltd.), 150 g of polyester polyol (product name "Kuraray Polyol P-2010", manufactured by Kuraray Co., Ltd.), 110 g of toluene (manufactured by Tosoh Corporation) as a solvent, and 0.041 g of dibutyltin(IV) dilaurate (manufactured by Wako Pure Chemical Industries, Ltd.) as a catalyst. While stirring, nitrogen substitution was carried out at room temperature for 1 hour. Then, while stirring under a nitrogen flow, 22.4 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added. While controlling the solution temperature in the experimental apparatus to be 90 ± 2 °C with a water bath, it was held for 4 hours. Then, 48.9 g of polypropylene glycol (product name "GP1000", manufactured by Sanyo Chemical Industries, Ltd.) was added. While controlling the solution temperature in the experimental apparatus to be 90 ± 2 °C with a water bath, it was held for 2 hours. Then, 3.1 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added. While controlling the solution temperature in the experimental apparatus to be 90 ± 2 °C with a water bath, it was held for 2 hours to obtain a urethane prepolymer solution A. During the polymerization, toluene was appropriately added dropwise to prevent a decrease in stirrability due to temperature control during polymerization and an increase in viscosity. The total amount of added dropwise toluene was 376 g. The solid content concentration of the urethane prepolymer solution A was 50% by weight.

[0178] 〔Example 1〕 100 parts by weight of the urethane prepolymer solution A obtained in Production Example 1 in terms of polymer solid content, 3.4 parts by weight of an isocyanate-based crosslinking agent (trade name "Coronate HX", manufactured by Tosoh Corporation) in terms of solid content, 0.5 parts by weight of a heat stabilizer (trade name "Irganox 1010", manufactured by BASF) in terms of solid content, and 10 parts by weight of a silica dispersion (trade name "MEK-EC-2130Y", manufactured by Nissan Chemical Industries, Ltd.) in terms of solid content were blended and diluted with ethyl acetate so that the total solid content was 45% by weight to obtain an adhesive composition (1). The obtained pressure-sensitive adhesive composition (1) was applied to a base material made of a polyester resin (trade name "T100-75S", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) so that the thickness after drying would be 75 μm, and cured and dried under the conditions of a drying temperature of 130°C and a drying time of 3 minutes. In this way, a pressure-sensitive adhesive layer (1) formed from the pressure-sensitive adhesive composition (1) was produced on the base material. Next, the silicone-treated surface of a separator made of a 25-μm-thick polyester resin (trade name "MRF25", thickness 25 μm, manufactured by Mitsubishi Chemical Corporation) with silicone treatment on one surface was bonded to the surface of the obtained pressure-sensitive adhesive layer (1) to obtain a protective film (1). The obtained protective film (1) was aged at room temperature for 7 days and evaluated. The release sheet was peeled off immediately before the evaluation. The results are shown in Table 1.

[0179] 〔Examples 2 to 6〕 Using the pressure-sensitive adhesive compositions (2) to (6) prepared by the same method as in Example 1 with the types and blending parts of the silica dispersion liquid as described in Table 1, a protective film was obtained using the same method as in Example 1. Further, evaluation was carried out in the same method as in Example 1. The results are shown in Table 1.

[0180] 〔Example 7〕 100 parts by weight of the urethane prepolymer solution A obtained in Production Example 1 in terms of polymer solid content was blended with 4.4 parts of silica powder (trade name "HM-30S", manufactured by Tokuyama), stirred at 1500 rpm for 15 minutes with a disper, and the stirred urethane prepolymer solution was filtered through a SUS400 mesh. To the filtered solution, 3.4 parts by weight of an isocyanate-based crosslinking agent (trade name "Coronate HX", manufactured by Tosoh Corporation) in terms of solid content, 0.5 part by weight of a heat-resistant stabilizer (trade name "Irganox 1010", manufactured by BASF) in terms of solid content, and 10 parts by weight of a silica dispersion liquid (trade name "MEK-EC―2130Y", manufactured by Nissan Chemical Industries, Ltd.) in terms of solid content were blended, and diluted with ethyl acetate so that the total solid content would be 45% by weight to obtain a pressure-sensitive adhesive composition (7). Using the obtained pressure-sensitive adhesive composition (7), a protective film was obtained in the same manner as in Example 1. Further evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

[0181] 〔Examples 8 - 26〕 In the same manner as in Example 1, the silica dispersion was replaced with the metal oxide dispersions described in Table 1, and pressure-sensitive adhesive compositions (8) - (26) were prepared with the types and blending amounts as described in Table 1. Using these pressure-sensitive adhesive compositions, a protective film was obtained in the same manner as in Example 1. Further evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

[0182] 〔Comparative Example 1〕 A pressure-sensitive adhesive composition (C1) was prepared in the same manner as in Example 1 except that no silica dispersion was blended. Using the prepared pressure-sensitive adhesive composition (C1), a protective film was obtained in the same manner as in Example 1. Further evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

[0183]

Table 1

Industrial Applicability

[0184] The protective film of the present invention can be used for any suitable application. Preferably, the protective film of the present invention is preferably used in the fields of optical members and electronic members.

Explanation of Reference Numerals

[0185] 10 Substrate layer 20 Pressure-sensitive adhesive layer 100 Protective film

Claims

A protective film having an adhesive layer formed from an adhesive composition, wherein: the haze of the protective film is 2.10% or less; the adhesive composition is an adhesive composition containing a base polymer, the base polymer is a urethane prepolymer, contains silica particles having an average primary particle diameter of 1 nm to 300 nm, and the content of the silica particles relative to 100 parts by weight of the base polymer is 14.4 parts by weight to 50 parts by weight. Protective film. **Claim 2** An adhesive composition containing a base polymer, wherein: the base polymer is a urethane prepolymer. Na with an average primary particle diameter of 5 nm to 50 nm 3 AlF 6 containing particles Adhesive composition. **Claim 3** An adhesive layer formed from the adhesive composition according to claim 2. **Claim 4** A protective film having the adhesive layer according to claim 3. **Claim 5** The protective film according to claim 4, wherein the haze is 5% or less.

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