JP7708530B2 - Pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, and protective film - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition. The present invention relates to a pressure-sensitive adhesive layer formed from such a pressure-sensitive adhesive composition. The present invention relates to a protective film having such a pressure-sensitive adhesive layer.

Laser dicing, which uses a laser beam to process the parts, is used to cut and divide semiconductor wafers to produce semiconductor chips, and to divide optical and electronic components.

However, when laser dicing is performed, the laser irradiation point becomes extremely hot, causing the material of the workpiece to vaporize, generating debris (condensate), which then adheres to the surface of the workpiece. When such debris adheres to the workpiece, problems arise, such as a decrease in the quality of the product, contamination of the production line, and a decrease in inspectability during the manufacturing process.

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 workpiece, laser dicing is performed through the protective film, and the workpiece is washed with water after processing, thereby washing away any attached debris together with the protective film (e.g., Patent Documents 1 and 2). However, this method cannot be applied when the workpiece is a material that cannot be washed with water, such as a polarizing plate or FPC. In addition, contamination by wastewater generated during washing is also a problem. Furthermore, the generation of debris itself cannot be suppressed.

A method has also been proposed in which a protective film containing a (meth)acrylic acid ester copolymer and a radiation-polymerizable (meth)acrylate having an unsaturated bond is formed on the processing surface of an object to be processed, laser dicing is performed through the protective film, and the protective film is hardened by irradiating it with ultraviolet light after processing, thereby removing the protective film to which debris has adhered (Patent Document 3). However, this method requires irradiating the object to be processed with ultraviolet light, and there is a problem that it is difficult to apply this method to objects that are sensitive to ultraviolet light irradiation (for example, many optical components such as polarizing plates). In addition, the protective film used in this method does not have a sufficiently low haze, so problems such as reduced inspectability in the manufacturing process still occur. Furthermore, the generation of debris itself cannot be suppressed.

JP 2006-140311 A JP 2015-134373 A JP 2009-155625 A

The object of the present invention is to provide an adhesive composition useful for a protective film that has excellent laser processability, suppresses the generation of debris, and has excellent inspectability during the manufacturing process, an adhesive layer formed from such an adhesive composition, and a protective film having such an adhesive layer.

The pressure-sensitive adhesive composition of the present invention comprises
A pressure-sensitive adhesive composition comprising a base polymer,
The metal oxide particles have an average primary particle size of 1 nm to 300 nm.

In one embodiment, the content of the metal oxide particles is 0.1% by weight to 50% by weight per 100 parts by weight of the base polymer.

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

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.

The adhesive layer of the present invention is formed from the adhesive composition of the present invention.

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

In one embodiment, the protective film of the present invention has a haze of 50% or less.

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

1 is a schematic cross-sectional view of a protective film according to one embodiment of the present invention.

A. Pressure-sensitive adhesive composition
The pressure-sensitive adhesive composition of the present invention contains a base polymer. The base polymer may be one type or two or more types.

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 type or two or more types.

The adhesive composition of the present invention may contain metal oxide particles other than the metal oxide particles having an average primary particle diameter of 1 nm to 300 nm, as long as the effect of the present invention is not impaired. However, the content of metal oxide particles having an average primary particle diameter of 1 nm to 300 nm in the total metal oxide particles contained in the adhesive composition of the present invention is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, even 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.

The adhesive composition of the present invention contains a base polymer and metal oxide particles with an average primary particle size of 1 nm to 300 nm, and therefore can provide an adhesive composition that is useful for protective films that have excellent laser processability, suppress the generation of debris, and excellent inspectability during the manufacturing process.

In the adhesive composition of the present invention, the content of the metal oxide particles relative to 100 parts by weight of the base polymer is preferably 0.1 to 50 parts by weight, more preferably 5 to 45 parts by weight, even more preferably 10 to 40 parts by weight, particularly preferably 15 to 35 parts by weight, and most preferably 20 to 35 parts by weight. If the content ratio of the metal oxide particles relative to the base polymer is within the above range, it is possible to provide an adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability in the manufacturing process. If the content ratio of the metal oxide particles relative to the base polymer is too low outside the above range, the laser processability may be insufficient and the generation of debris may not be suppressed. If the content ratio of the metal oxide particles relative to the base polymer is too high outside the above range, there is a risk that the haze value will increase, secondary aggregation of the metal oxide particles will occur, or large unevenness will occur on the surface of the adhesive layer, making it difficult to adhere.

The content of the base polymer in the adhesive composition of the present invention is preferably 50% by weight to 99% by weight, more preferably 55% by weight to 90% by weight, even 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 of the base polymer in the adhesive composition of the present invention is within the above range, it is possible to provide an adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability in the manufacturing process. If the content of the base polymer in the adhesive composition of the present invention is too low outside the above range, there is a risk of insufficient adhesive strength or a rough adhesive surface that may trap air bubbles when the protective film is attached. If the content of the base polymer in the adhesive composition of the present invention is too high outside the above range, there is a risk of insufficient laser processability.

≪A-1. Metal oxide particles≫
The average primary particle diameter of the metal oxide particles is 1 nm to 300 nm, preferably 1 nm to 250 nm, more preferably 1 nm to 200 nm, even more preferably 1 nm to 175 nm, even more preferably 1 nm to 150 nm, even more preferably 1 nm to 100 nm, particularly preferably 5 nm to 75 nm, and most preferably 5 nm to 50 nm. If the average primary particle diameter of the metal oxide particles is within the above range, it is possible to provide a pressure-sensitive adhesive composition useful for a protective film that has excellent laser processability, more suppresses the generation of debris, and has excellent inspectability in the manufacturing process. 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 average primary particles, and there is a risk of an increase in the haze value or a rough adhesive surface, which may cause air bubbles to be trapped when the protective film is attached. 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 or a rough adhesive surface, which may cause air bubbles to be trapped when the protective film is attached.

As the metal oxide particles, any suitable metal oxide particles can be adopted within the scope that does not impair the effects of the present invention. Examples of such metal oxide particles include silica (SiO ₂ ) particles, titanium oxide (TiO ₂ ) particles, alumina (Al ₂ O ₃ ) particles, zirconium oxide (ZrO ₂ ) particles, cryolite (Na ₃ AlF ₆ ) particles, ATO particles, ITO particles, bismuth oxide (Bi ₂ O ₃ ) particles, etc., and preferably silica particles, titanium oxide particles, and ATO particles are included, and more preferably silica particles are included, taking into account the average primary particle size.

By using silica as metal oxide particles with an average primary particle size of 1 nm to 300 nm, it is possible to provide a pressure-sensitive adhesive composition that is useful for protective films that have excellent laser processability, further suppress the generation of debris, and excellent inspectability during the manufacturing process.

<A-2. Base polymer>
The base polymer is preferably at least one selected from urethane prepolymers, polyols, acrylic resins, rubber resins, and silicone resins. When the base polymer is at least one selected from urethane prepolymers, polyols, acrylic resins, rubber resins, and silicone resins, by incorporating the base polymer in combination with metal oxide particles having an average primary particle size of 1 nm to 300 nm into the pressure-sensitive adhesive composition, it is possible to provide a pressure-sensitive adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability in the manufacturing process.

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

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

The molecular weight of the polyester polyol (a1) can range from low to high. 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 may be high and the polyurethane polyol may be prone to gelation. If the number average molecular weight exceeds 100,000, the reactivity may be low and the cohesive force of the polyurethane polyol itself may be low. The amount of polyester polyol (a1) used is preferably 0 mol % to 90 mol % of the polyols constituting the polyurethane polyol.

Any suitable polyether polyol may be used as the polyether polyol (a2). 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 a low molecular weight polyol such as water, propylene glycol, ethylene glycol, glycerin, and trimethylolpropane as an initiator. Specific examples of such polyether polyols (a2) include polyether polyols having two or more functional groups, such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol.

The molecular weight of the polyether polyol (a2) can range from low to high. The number average molecular weight of the polyether polyol (a2) is preferably 100 to 100,000. If the number average molecular weight is less than 100, the reactivity may be high and the polyurethane polyol may be prone to gelation. If the number average molecular weight exceeds 100,000, the reactivity may be low and the cohesive force of the polyurethane polyol itself may be low. The amount of polyether polyol (a2) used is preferably 0 mol % to 90 mol % of the polyol constituting the polyurethane polyol.

If necessary, polyether polyol (a2) can be used in combination with a glycol such as ethylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, glycerin, trimethylolpropane, or pentaerythritol, or a polyamine such as ethylenediamine, N-aminoethylethanolamine, isophoronediamine, or xylylenediamine.

As the polyether polyol (a2), only bifunctional polyether polyols may be used, or a polyether polyol having a number average molecular weight of 100 to 100,000 and at least three or more hydroxyl groups in one molecule may be used in part or in whole. If a polyether polyol having a number average molecular weight of 100 to 100,000 and at least three or more hydroxyl groups in one molecule is used in part or in whole as the polyether polyol (a2), the balance between adhesive strength and removability can be improved. If the number average molecular weight of such a polyether polyol is less than 100, the reactivity may be high and the polyether polyol may be easily gelled. If the number average molecular weight of such a polyether polyol is more than 100,000, the reactivity may be low and the cohesive force of the polyurethane polyol itself may be small. The number average molecular weight of such a polyether polyol is more preferably 100 to 10,000.

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

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, and 4,4',4"-triphenylmethane triisocyanate.

Examples of aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

Examples of aromatic aliphatic polyisocyanates include ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate.

Examples of alicyclic polyisocyanates 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, and 1,4-bis(isocyanatomethyl)cyclohexane.

As the organic polyisocyanate compound (a3), a trimethylolpropane adduct, a biuret reacted with water, a trimer having an isocyanurate ring, etc. can be used in combination.

Any suitable catalyst can be used to obtain the polyurethane polyol. Examples of such catalysts include tertiary amine compounds and organometallic compounds.

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

Examples of organometallic compounds include tin-based compounds and non-tin-based compounds.

Examples of tin 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, and tin 2-ethylhexanoate.

Non-tin compounds include, for example, titanium compounds such as dibutyltitanium dichloride, tetrabutyltitanium trichloride, and butoxytitanium trichloride; lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; iron compounds such as iron 2-ethylhexanoate and iron acetylacetonate; cobalt compounds such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc compounds such as zinc naphthenate and zinc 2-ethylhexanoate; and zirconium compounds such as zirconium naphthenate.

When using a catalyst to obtain polyurethane polyol, in a system in which two types of polyols, polyester polyol and polyether polyol, are present, problems such as gelation or clouding of the reaction solution are likely to occur in a system using a single catalyst due to the difference in reactivity between the two polyols. Therefore, by using two types of catalysts to obtain polyurethane polyol, it becomes easier to control the reaction rate and catalyst selectivity, and these problems can be solved. Examples of such combinations of two types of catalysts include tertiary amine/organic metal system, tin/non-tin system, and tin/tin system, and preferably tin/tin system, and more preferably a combination of dibutyltin dilaurate and tin 2-ethylhexanoate. The blending ratio of tin 2-ethylhexanoate/dibutyltin dilaurate is preferably less than 1, more preferably 0.2 to 0.6, by weight. If the blending ratio is 1 or more, gelation may occur easily due to the balance of catalyst activity.

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

When a catalyst is used to obtain polyurethane polyol, the reaction temperature is preferably less than 100°C, and more preferably 85°C to 95°C. If the temperature is above 100°C, it may become difficult to control the reaction rate and crosslinking structure, and it may become difficult to obtain a polyurethane polyol with the specified molecular weight.

When obtaining polyurethane polyol, it is not necessary to use a catalyst. In that case, the reaction temperature is preferably 100°C or higher, and more preferably 110°C or higher. In addition, when obtaining polyurethane polyol without a catalyst, it is preferable to carry out the reaction for 3 hours or more.

Methods for obtaining polyurethane polyol include, for example, 1) a method in which polyester polyol, polyether polyol, catalyst, and organic polyisocyanate are all charged into a flask, and 2) a method in which polyester polyol, polyether polyol, and catalyst are charged into a flask and organic polyisocyanate is added dropwise. Method 2) is preferred as a method for obtaining polyurethane polyol in terms of controlling the reaction.

When obtaining the polyurethane polyol, any suitable solvent may be used. Examples of such solvents include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone. Of these solvents, toluene is preferred.

<A-2-2. Polyol>
The polyol preferably includes, for example, polyester polyol, polyether polyol, polycaprolactone polyol, polycarbonate polyol, and castor oil polyol. The polyol is more preferably polyether polyol.

Polyester polyols can be obtained, for example, by an esterification reaction between a polyol component and an acid component.

Examples of polyol components 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, and polypropylene glycol. Examples of acid components include succinic acid, methylsuccinic 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 anhydrides of these acids.

Examples of polyether polyols include polyether polyols obtained by addition polymerization of alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide using water, low molecular weight polyols (propylene glycol, ethylene glycol, glycerin, trimethylolpropane, pentaerythritol, etc.), bisphenols (bisphenol A, etc.), and dihydroxybenzenes (catechol, resorcin, hydroquinone, etc.) as initiators. Specific examples include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

Examples of polycaprolactone polyols include caprolactone-based polyester diols obtained by ring-opening polymerization of cyclic ester monomers such as ε-caprolactone and σ-valerolactone.

Examples of polycarbonate polyols include polycarbonate polyols obtained by polycondensation reaction of the above polyol components with phosgene; polycarbonate polyols obtained by transesterification condensation of the above polyol components with carbonate diesters such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, ethyl butyl carbonate, ethylene carbonate, propylene carbonate, diphenyl carbonate, and dibenzyl carbonate; copolymer polycarbonate polyols obtained by using two or more of the above polyol components in combination; polycarbonate polyols obtained by esterification reaction of the above various polycarbonate polyols with carboxyl group-containing compounds; Polycarbonate polyols obtained by etherification reaction of recarbonate polyols with hydroxyl group-containing compounds; polycarbonate polyols obtained by transesterification reaction of the above-mentioned various polycarbonate polyols with ester compounds; polycarbonate polyols obtained by transesterification reaction of the above-mentioned various polycarbonate polyols with hydroxyl group-containing compounds; polyester-based polycarbonate polyols obtained by polycondensation reaction of the above-mentioned various polycarbonate polyols with dicarboxylic acid compounds; copolymerized polyether-based polycarbonate polyols obtained by copolymerizing the above-mentioned various polycarbonate polyols with alkylene oxides; and the like.

Examples of castor oil-based polyols include castor oil-based polyols obtained by reacting castor oil fatty acids with the above-mentioned polyol components. Specific examples include castor oil-based polyols obtained by reacting castor oil fatty acids with polypropylene glycol.

The number average molecular weight Mn of the polyol is preferably 300 to 100,000, more preferably 400 to 75,000, even more preferably 450 to 50,000, and particularly preferably 500 to 30,000. If 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 size of 1 nm to 300 nm and incorporating it into an adhesive composition, it is possible to provide an adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability in the manufacturing process. In addition, the protective film of the present invention can be suppressed from peeling heavily over time.

The polyol preferably contains a polyol (A1) having three OH groups and a number average molecular weight Mn of 300 to 100,000. The polyol (A1) may be one type or two or more types.

The content of polyol (A1) in the polyol is preferably 5% by weight or more, more preferably 25% by weight to 100% by weight, and even more preferably 50% by weight to 100% by weight. If the content of 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 size of 1 nm to 300 nm and incorporating it into an adhesive composition, it is possible to provide an adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability in the manufacturing process. In addition, the protective film of the present invention can be suppressed from peeling heavily over time.

The number average molecular weight Mn of the polyol (A1) is preferably 1000 to 100000, more preferably 1200 to 80000, even more preferably 1500 to 70000, even more preferably 1750 to 50000, particularly preferably 1500 to 40000, and most preferably 2000 to 30000. If 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 size of 1 nm to 300 nm and incorporating it into an adhesive composition, it is possible to provide an adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability in the manufacturing process. In addition, the protective film of the present invention can be suppressed from peeling heavily over time.

The polyol may contain a polyol (A2) having three or more OH groups and a number average molecular weight Mn of 20,000 or less. The polyol (A2) may be of only one type, or of two or more types. The number average molecular weight Mn of the polyol (A2) is preferably 100 to 20,000, more preferably 150 to 10,000, even more preferably 200 to 7,500, particularly preferably 300 to 6,000, and most preferably 300 to 5,000. If the number average molecular weight Mn of the polyol (A2) is outside the above range, there is a risk that the peel strength of the protective film of the present invention may increase over time. As the polyol (A2), preferably, a polyol (triol) having three OH groups, a polyol (tetraol) having four OH groups, a polyol (pentaol) having five OH groups, or a polyol (hexaol) having six OH groups may be mentioned.

The total amount of polyol (A2) having 4 OH groups (tetraol), polyol (pentaol) having 5 OH groups, and polyol (hexaol) having 6 OH groups is preferably 70% by weight or less, more preferably 60% by weight or less, even more preferably 40% by weight or less, and particularly preferably 30% by weight or less, as the content ratio in the polyol. If the total amount of polyol (A2) having 4 OH groups (tetraol), polyol (pentaol) having 5 OH groups, and polyol (hexaol) having 6 OH groups is within the above range in the polyol, a pressure-sensitive adhesive layer with excellent transparency can be provided, and the protective film of the present invention can be further suppressed from peeling heavily over time.

The content of polyol (A2) in the polyol is preferably 95% by weight or less, and more preferably 0% by weight to 75% by weight. If the content of polyol (A2) in the polyol is within the above range, then by combining such a base polymer with metal oxide particles having an average primary particle size of 1 nm to 300 nm and incorporating them into an adhesive composition, it is possible to provide an adhesive composition that is useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability during the manufacturing process. In addition, the protective film of the present invention can be prevented from peeling off heavily over time.

The content of polyols having 4 or more OH groups and a number average molecular weight Mn of 20,000 or less as polyol (A2) is preferably less than 70% by weight, more preferably 60% by weight or less, even 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 total polyol. If the content of polyols having 4 or more OH groups and a number average molecular weight Mn of 20,000 or less as polyol (A2) is within the above range based on the total polyol, a pressure-sensitive adhesive layer with excellent transparency can be provided, and the protective film of the present invention can be further prevented from peeling heavily over time.

<A-2-3. Acrylic resin>
As the acrylic resin, any appropriate acrylic pressure-sensitive adhesive may be adopted, for example, a known acrylic pressure-sensitive adhesive described in JP-A-2013-241606, as long as the effects of the present invention are not impaired.

The acrylic resin may contain any suitable component within the scope of the present invention, so long as the effect of the present invention is not impaired. Examples of such components include resin components other than acrylic resins, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foil-like materials, softeners, antioxidants, conductive agents, UV absorbers, antioxidants, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, catalysts, etc.

<A-2-4. Rubber-based resin>
As the rubber-based resin, any appropriate rubber-based adhesive may be used, for example, a known rubber-based adhesive described in JP-A-2015-074771, etc., within the scope of not impairing the effects of the present invention. These may be used alone or in combination of two or more kinds.

The rubber-based resin may contain any appropriate component within a range that does not impair the effects of the present invention. Examples of such components include resin components other than rubber-based resins, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foil-like materials, softeners, antioxidants, conductive agents, UV absorbers, antioxidants, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, catalysts, etc.

<A-2-5. Silicone resin>
As the silicone-based adhesive, any appropriate silicone-based adhesive may be used, as long as it does not impair the effects of the present invention, such as known silicone-based adhesives described in JP-A-2014-047280, etc. These may be used alone or in combination of two or more types.

The silicone resin may contain any suitable component within the scope of the present invention, so long as the effect of the present invention is not impaired. Examples of such components include resin components other than silicone resins, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foil-like materials, softeners, antioxidants, conductive agents, UV absorbers, antioxidants, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, catalysts, etc.

<A-3. Crosslinking agent>
The pressure-sensitive adhesive composition of the present invention may contain a crosslinking agent. The crosslinking agent may be of only one type, or of two or more types.

As the crosslinking agent, any appropriate crosslinking agent may be used as long as it does not impair the effects of the present invention. Examples of such crosslinking agents include 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, and amine-based crosslinking agents, and preferably, isocyanate-based crosslinking agents and epoxy-based crosslinking agents.

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

Representative examples of epoxy crosslinking agents include polyfunctional epoxy compounds, such as N,N,N',N'-tetraglycidyl-m-xylylenediamine, 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. Examples of the epoxy resin include 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, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Examples of the polyfunctional epoxy compound include commercially available products such as "Tetrad C" (manufactured by Mitsubishi Gas Chemical Co., Ltd.).

<A-4. Components of the composition for forming the urethane resin>
The urethane prepolymer and polyol as the base polymer can be combined with a polyfunctional isocyanate compound to form a composition for forming a urethane resin. By adopting the above-mentioned as the components of the composition for forming a urethane resin, and by combining such a base polymer with metal oxide particles having an average primary particle size of 1 nm to 300 nm and incorporating them into a pressure-sensitive adhesive composition, it is possible to provide a pressure-sensitive adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability in the manufacturing process.

When forming a urethane resin, the adhesive composition of the present invention may contain other components such as, for example, resin components other than the urethane resin, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foil-like materials, softeners, antioxidants, conductive agents, UV absorbers, antioxidants, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, and catalysts. Such other components may be of only one type, or of two or more types.

When a urethane resin is formed, the pressure-sensitive adhesive composition of the present invention preferably contains a deterioration inhibitor such as an antioxidant, an ultraviolet absorber, or a light stabilizer. By containing an deterioration inhibitor in the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive layer formed is less likely to leave adhesive residue on the adherend even when the layer is applied to the adherend and then stored in a heated state, and the adhesive composition can have excellent adhesive residue prevention properties. The deterioration inhibitor may be of only one type, or of two or more types. An antioxidant is particularly preferred as the deterioration inhibitor.

Examples of antioxidants include radical chain inhibitors and peroxide decomposers.

Examples of radical chain inhibitors include phenol-based antioxidants and amine-based antioxidants.

Examples of peroxide decomposers include sulfur-based antioxidants and phosphorus-based antioxidants.

Examples of phenol-based antioxidants include monophenol-based antioxidants, bisphenol-based antioxidants, and polymeric phenol-based antioxidants.

Examples of monophenol-based antioxidants include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, and stearin-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate.

Examples of bisphenol-based 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.

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, and tocopherol.

Examples of sulfur-based antioxidants include dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, and distearyl 3,3'-thiodipropionate.

Examples of phosphorus-based antioxidants include triphenyl phosphite, diphenyl isodecyl phosphite, and phenyl diisodecyl phosphite.

Examples of ultraviolet absorbers include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, anilide oxalate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and triazine-based ultraviolet absorbers.

Examples of benzophenone-based UV absorbers 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, and bis(2-methoxy-4-hydroxy-5-benzoylphenyl)methane.

Examples of benzotriazole-based ultraviolet absorbers 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',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, -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, etc.

Examples of salicylic acid-based UV absorbers include phenyl salicylate, p-tert-butylphenyl salicylate, and p-octylphenyl salicylate.

Examples of cyanoacrylate-based UV absorbers include 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate and ethyl-2-cyano-3,3'-diphenylacrylate.

Examples of light stabilizers include hindered amine light stabilizers and UV stabilizers.

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, and methyl-1,2,2,6,6-pentamethyl-4-piperidylsebacate.

Examples of UV stabilizers include nickel bis(octylphenyl)sulfide, [2,2'-thiobis(4-tert-octylphenolate)]-n-butylamine nickel, nickel complex-3,5-di-tert-butyl-4-hydroxybenzyl-phosphate monoethylate, nickel-dibutyldithiocarbamate, benzoate-type quenchers, and nickel-dibutyldithiocarbamate.

<A-4-1. Urethane resin formed from a composition containing a urethane prepolymer and a polyfunctional isocyanate compound>
Examples of the urethane-based resin formed from a composition containing a urethane prepolymer and a polyfunctional isocyanate compound include a urethane-based resin formed from a composition containing a polyurethane polyol as the urethane prepolymer and a polyfunctional isocyanate compound.

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

The polyfunctional isocyanate compound may be of one type or of two or more types.

As the polyfunctional isocyanate compound, any suitable polyfunctional isocyanate compound that can be used in a urethane reaction can be used. Examples of such polyfunctional isocyanate compounds include polyfunctional aliphatic isocyanate compounds, polyfunctional alicyclic isocyanates, and polyfunctional aromatic isocyanate compounds.

Examples of polyfunctional aliphatic isocyanate compounds include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

Examples of polyfunctional alicyclic isocyanate compounds include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

Examples of polyfunctional aromatic diisocyanate compounds 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'-diphenylether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and xylylene diisocyanate.

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

As a method for forming a polyurethane resin from a composition containing a urethane prepolymer and a polyfunctional isocyanate compound, any suitable manufacturing method can be used as long as it is a method for manufacturing a polyurethane resin using a so-called "urethane prepolymer" as a raw material.

The number average molecular weight Mn of the urethane prepolymer is preferably 3,000 to 1,000,000.

The equivalent ratio of NCO groups to OH groups in the urethane prepolymer and the polyfunctional isocyanate compound, expressed as NCO groups/OH groups, is preferably 5.0 or less, more preferably 0.01 to 4.75, even more preferably 0.02 to 4.5, particularly preferably 0.03 to 4.25, and most preferably 0.05 to 4.0. If the equivalent ratio of NCO groups/OH groups 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 size of 1 nm to 300 nm and incorporating them into an adhesive composition, it is possible to provide an adhesive composition useful for protective films that have excellent laser processability, further suppress the generation of debris, and excellent inspectability during the manufacturing process.

The content of the polyfunctional isocyanate compound is preferably 0.01% by weight to 30% by weight, more preferably 0.05% by weight to 25% by weight, even more preferably 0.1% by weight to 20% by weight, particularly preferably 0.5% by weight to 17.5% by weight, and most preferably 1% by weight to 15% by weight, relative to the urethane prepolymer. If the content of the polyfunctional isocyanate compound is within the above range, then by incorporating such an amount of polyfunctional isocyanate in combination with a base polymer and metal oxide particles having an average primary particle size of 1 nm to 300 nm into the adhesive composition, it is possible to provide an adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability during the manufacturing process.

<A-4-2. Urethane resin formed from a composition containing a polyol and a polyfunctional isocyanate compound>
Specifically, the urethane-based resin formed from a composition containing a polyol and a polyfunctional isocyanate compound is preferably a urethane-based resin obtained by curing a composition containing a polyol and a polyfunctional isocyanate compound.

The polyol may be one type or two or more types.

The polyfunctional isocyanate compound may be of one type or of two or more types.

As the polyfunctional isocyanate compound, those mentioned above can be used.

The equivalent ratio of NCO groups to OH groups in the polyol and polyfunctional isocyanate compound, expressed as NCO groups/OH groups, is preferably 5.0 or less, more preferably 0.1 to 3.0, even 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 NCO groups/OH groups 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 size of 1 nm to 300 nm and incorporating them into an adhesive composition, it is possible to provide an adhesive composition that is useful for protective films that have excellent laser processability, further suppress the generation of debris, and excellent inspectability during the manufacturing process.

The content 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, even 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, relative to the polyol. If the content of the polyfunctional isocyanate compound is within the above range, then by incorporating such an amount of polyfunctional isocyanate in combination with a base polymer and metal oxide particles having an average primary particle size of 1 nm to 300 nm into the adhesive composition, it is possible to provide an adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability during the manufacturing process.

Specifically, the polyurethane resin is 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 resin, any appropriate method may be used as long as it does not impair the effects of the present invention, such as a urethane reaction method using bulk polymerization or solution polymerization.

A catalyst is preferably used to cure the composition containing the polyol and the polyfunctional isocyanate compound. Examples of such catalysts include organometallic compounds and tertiary amine compounds.

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

Examples of iron-based compounds include iron acetylacetonate and iron 2-ethylhexanoate.

Examples of tin 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, and tin 2-ethylhexanoate.

Examples of titanium compounds include dibutyltitanium dichloride, tetrabutyltitanium, and butoxytitanium trichloride.

Examples of zirconium compounds include zirconium naphthenate and zirconium acetylacetonate.

Examples of lead-based compounds include lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate.

Examples of cobalt-based compounds include cobalt 2-ethylhexanoate and cobalt benzoate.

Examples of zinc-based compounds include zinc naphthenate and zinc 2-ethylhexanoate.

Examples of tertiary amine compounds include triethylamine, triethylenediamine, and 1,8-diazabic-(5,4,0)-undecene-7.

Only one type of catalyst may be used, or two or more types may be used. A catalyst may also be used in combination with a crosslinking retarder or the like. The amount of catalyst is preferably 0.005% by weight to 1.00% by weight, more preferably 0.01% by weight to 0.75% by weight, even more preferably 0.01% by weight to 0.50% by weight, and particularly preferably 0.01% by weight to 0.20% by weight, relative to the polyol. If the amount of catalyst is within the above range, a pressure-sensitive adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability during the manufacturing process can be provided.

<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 one type or two or more types. By containing a fatty acid ester, the pressure-sensitive adhesive composition of the present invention can provide a pressure-sensitive adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability in the manufacturing process.

The number average molecular weight Mn of the fatty acid ester is preferably 100 to 800, more preferably 150 to 750, even more preferably 200 to 700, particularly preferably 200 to 650, and most preferably 200 to 600. If 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 has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability during the manufacturing process.

As the fatty acid ester, any suitable fatty acid ester may be used as long as it does not impair the effects of the present invention. Examples of such fatty acid esters include polyoxyethylene bisphenol A laurate, butyl stearate, 2-ethylhexyl palmitate, 2-ethylhexyl stearate, behenic acid monoglyceride, 2-ethylhexanoate cetyl, isopropyl myristate, isopropyl palmitate, cholesteryl isostearate, lauryl methacrylate, coconut fatty acid methyl, methyl laurate, methyl oleate, methyl stearate, myristyl myristate, octyldodecyl myristate, pentaerythritol monooleate, pentaerythritol monostearate, pentaerythritol tetrapalmitate, stearyl stearate, isotridecyl stearate, 2-ethylhexanoic acid triglyceride, butyl laurate, and octyl oleate.

When the pressure-sensitive adhesive composition of the present invention contains a fatty acid ester, the content of the fatty acid ester is preferably 0.01 to 50 parts by weight, more preferably 0.05 to 45 parts by weight, even more preferably 0.1 to 40 parts by weight, even more preferably 0.3 to 35 parts by weight, even more preferably 0.5 to 30 parts by weight, particularly preferably 0.5 to 25 parts by weight, and most preferably 0.5 to 20 parts by weight, relative to 100 parts by weight of the base polymer. If the content of the fatty acid ester is within the above range relative to 100 parts by weight of the base polymer, a pressure-sensitive adhesive composition useful for a protective film that has excellent laser processability, further suppresses the generation of debris, and has excellent inspectability in the manufacturing process can be provided.

<A-6. Ionic liquid>
The pressure-sensitive adhesive composition of the present invention may contain an ionic liquid containing a fluoroorganic anion. By containing an ionic liquid containing a fluoroorganic anion in the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive composition having very excellent antistatic properties can be provided. Such an ionic liquid may be one type only, or may be two or more types.

If the adhesive composition of the present invention contains an ionic liquid containing a fluoroorganic anion, it is possible to provide an adhesive composition with excellent antistatic properties, and for example, it is possible to effectively suppress adhesion of generated debris.

In the present invention, an ionic liquid refers to a molten salt (ionic compound) that is liquid at 25°C.

As the ionic liquid, any appropriate ionic liquid may be used as long as it contains a fluoroorganic anion and does not impair the effects of the present invention. Such an ionic liquid is preferably an ionic liquid composed of a fluoroorganic anion and an onium cation. By using an ionic liquid composed of a fluoroorganic anion and an onium cation as the ionic liquid, a pressure-sensitive adhesive composition with extremely excellent antistatic properties can be provided.

As the onium cation that can constitute the ionic liquid, any appropriate onium cation can be used 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 one of these onium cations, it is possible to provide a pressure-sensitive adhesive composition with extremely excellent antistatic properties.

Commercially available ionic liquids may be used, but they can also be synthesized as described below. There are no particular limitations on the method for synthesizing ionic liquids as long as the desired ionic liquid is obtained, but generally, the halide method, hydroxide method, acid ester method, complex formation method, and neutralization method are used, as described in the literature "Ionic Liquids - The Frontline and Future of Development" (published by CMC Publishing Co., Ltd.).

The amount of ionic liquid to be added cannot be generally defined because it varies depending on the compatibility between the polymer and the ionic liquid used, but generally, it is preferably 0.001 to 50 parts by weight, more preferably 0.01 to 40 parts by weight, even 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, relative to 100 parts by weight of the base polymer. By adjusting the amount of ionic liquid to be added within the above range, a pressure-sensitive adhesive composition with extremely excellent antistatic properties can be provided. If the amount of ionic liquid is less than 0.01 parts by weight, sufficient antistatic properties may not be obtained. If the amount of ionic liquid to be added exceeds 50 parts by weight, contamination of the adherend tends to increase.

<A-7. Fluorine-based additives>
The pressure-sensitive adhesive composition of the present invention may contain a fluorine-based additive. The fluorine-based additive may be of only one type, or of two or more types.

Any appropriate fluorine-based additive may be used as long as it does not impair the effects of the present invention. Such a fluorine-based additive is preferably at least one selected from a fluorine-containing compound, a hydroxyl group-containing fluorine-based compound, and a crosslinkable functional group-containing fluorine-based compound.

Examples of fluorine-containing compounds include compounds having a fluoroaliphatic hydrocarbon skeleton, fluorine-containing organic compounds obtained by copolymerizing an organic compound with a fluorine compound, and fluorine-containing compounds containing an organic compound. Examples of fluoroaliphatic hydrocarbon skeletons include fluoro C1-C10 alkanes such as fluoromethane, fluoroethane, fluoropropane, fluoroisopropane, fluorobutane, fluoroisobutane, fluoro t-butane, fluoropentane, and fluorohexane. Commercially available examples of such fluorine-containing compounds include Surflon series leveling agents manufactured by AGC Seimi Chemical Co., Ltd. (such as "S-242", "S-243", "S-420", "S-611", "S-651", and "S-386"); BYK series leveling agents manufactured by BYK Japan Co., Ltd. (such as "BYK-340"); AC series leveling agents manufactured by Algin Chemie Co., Ltd. (such as "AC 110a" and "AC 100a"); and Megafac series leveling agents manufactured by DIC Corporation (such as "Megafac F-114", "Megafac F-410", "Megafac F-444", and "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.), FC series leveling agents manufactured by Sumitomo 3M Limited (FC-4430, FC-4432, etc.), Ftergent series leveling agents manufactured by NEOS Co., Ltd. (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 PF series leveling agents manufactured by Kitamura Chemical Industries Co., Ltd. ("PF-136A", "PF-156A", "PF-151N", "PF-636", "PF-6320", "PF-656", "PF-6520", "PF-651", "PF-652", "PF-3320", etc.).

As the hydroxyl group-containing fluorine-based compound, for example, a conventionally known resin can be used, and examples thereof include hydroxyl group-containing fluorine resins described in WO 94/06870, JP 8/12921 A, JP 10/72569 A, JP 4/275379 A, WO 97/11130 A, and WO 96/26254 A. Other hydroxyl group-containing fluorine resins include fluoroolefin copolymers described in JP 8/231919 A, JP 10/265731 A, JP 10/204374 A, and JP 8/12922 A. Other examples include copolymers of compounds having fluorinated alkyl groups in hydroxyl group-containing compounds, fluorine-containing organic compounds in which hydroxyl group-containing compounds are copolymerized with fluorine-containing compounds, and fluorine-containing compounds containing hydroxyl group-containing organic compounds. Examples of commercially available hydroxyl group-containing fluorine-based compounds include those sold under the trade name "Lumiflon" (manufactured by Asahi Glass Co., Ltd.), "Cefralcoat" (manufactured by Central Glass Co., Ltd.), "Zaflon" (manufactured by Toa Gosei Co., Ltd.), "Zeffle" (manufactured by Daikin Industries, Ltd.), "Megafac F-571" and "Fluonate" (manufactured by DIC Corporation).

Examples of crosslinkable functional group-containing fluorine-based compounds include carboxylic acid compounds having a fluorinated alkyl group such as perfluorooctanoic acid, copolymers of compounds having a fluorinated alkyl group with a crosslinkable functional group-containing compound, fluorine-containing organic compounds in which a crosslinkable functional group-containing compound is copolymerized with a fluorine-containing compound, and fluorine-containing compounds containing a crosslinkable functional group-containing compound. Commercially available examples of such crosslinkable functional group-containing fluorine-based compounds include those sold under the trade names "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", and "Megafac RS-90" (manufactured by DIC Corporation).

<A-8. Other ingredients>
The pressure-sensitive adhesive composition of the present invention may contain any other appropriate component within a range that does not impair the effects of the present invention. Such other components may be only one type or two or more types. Examples of such other components include other resin components, tackifiers, inorganic fillers, organic fillers, metal powders, pigments, foils, softeners, anti-aging agents, conductive agents, UV absorbers, antioxidants, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers, polymerization inhibitors, lubricants, solvents, catalysts, etc.

<<B. 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.

The adhesive layer may be formed by any suitable method. Examples of such methods include a method in which the adhesive composition of the present invention is directly applied (typically coated) to a substrate and dried to form an adhesive layer (direct method), and a method in which the adhesive composition of the present invention is coated on a surface with good releasability (e.g., the surface of a release liner, the back surface of a support substrate that has been subjected to a release treatment, etc.) and dried to form an adhesive layer on the surface, and then the adhesive layer is transferred to a substrate (transfer method).

Examples of coating methods include roll coating, gravure coating, reverse coating, kiss coating, dip coating, bar coating, roll brushing, spray coating, air knife coating, and extrusion coating using a die coater.

From the viewpoint of promoting the crosslinking reaction and improving production efficiency, the adhesive composition of the present invention is preferably dried under heating when forming the adhesive layer. The heating temperature is preferably 40°C to 150°C, more preferably 40°C to 120°C, even more preferably 50°C to 120°C, and particularly preferably 70°C to 100°C.

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

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

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

The adhesive layer of the present invention is formed from the adhesive composition of the present invention, and therefore the haze is preferably 50% or less, more preferably 30% or less, even 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 have excellent inspectability during the manufacturing process.

<<C. Protective film>>
The protective film of the present invention has the pressure-sensitive adhesive layer of the present invention. The protective film of the present invention may have any other appropriate member as long as it has the pressure-sensitive adhesive layer of the present invention, as long as the effect of the present invention is not impaired. Typically, the protective film of the present invention has a base layer and a pressure-sensitive adhesive layer.

In the protective film of the present invention, it is preferable that one of the outermost layers is an appropriate release liner (sometimes called a release sheet or separator) provided on the pressure-sensitive adhesive layer or its surface for protection until use.

By adopting a specific adhesive layer, the protective film of the present invention can provide a protective film that is excellent in laser processability, suppresses the generation of debris, and has excellent inspectability during the manufacturing process.

Figure 1 is a schematic cross-sectional view of a protective film according to one embodiment of the present invention. In Figure 1, the protective film 100 comprises a base layer 10 and an adhesive layer 20. In Figure 1, the base layer 10 and the adhesive layer 20 are directly laminated together. Note that Figure 1 is merely a schematic cross-sectional view of a protective film according to one embodiment of the present invention, and may, for example, have any other appropriate layers within a range that does not impair the effects of the present invention.

In FIG. 1, the surface of the adhesive layer 20 opposite the substrate layer 10 may be provided with any suitable release liner (sometimes called a release sheet or separator) for protection until use (not shown). Examples of release liners include release liners in which the surface of a substrate (liner substrate) such as paper or plastic film is silicone-treated, and release liners in which the surface of a substrate (liner substrate) such as paper or plastic film is laminated with a polyolefin resin. Examples of plastic films as liner substrates include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, and ethylene-vinyl acetate copolymer films. The plastic film as the liner substrate is preferably a polyethylene film.

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

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

The protective film of the present invention can be produced by any suitable method. Examples of such a production method include
(1) A method of applying a solution or a hot melt of a material for forming the adhesive layer onto a base layer,
(2) A method of applying a solution or a hot melt of a material for forming an adhesive layer onto a separator to form an adhesive layer, and then transferring the adhesive layer onto a base layer;
(3) A method of forming and coating a material for forming a pressure-sensitive adhesive layer on a base material layer by extrusion;
(4) A method of extruding a substrate layer and a pressure-sensitive adhesive layer in two layers or multiple layers,
(5) A method of laminating a single layer of a pressure-sensitive adhesive layer on a substrate layer, or a method of laminating a double layer of a pressure-sensitive adhesive layer together with a laminate layer,
(6) A method of laminating a pressure-sensitive adhesive layer and a base layer-forming material such as a film or a laminate layer in a two-layer or multi-layer manner,
The above-mentioned manufacturing method can be used in accordance with any suitable manufacturing method.

Examples of coating methods include roll coating, gravure coating, reverse coating, kiss coating, dip coating, bar coating, roll brushing, spray coating, air knife coating, and extrusion coating using a die coater.

The protective film of the present invention has the pressure-sensitive adhesive layer of the present invention formed from the pressure-sensitive adhesive composition of the present invention, and by selecting an appropriate base layer, the haze is preferably 50% or less, more preferably 30% or less, even 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 have excellent inspectability in the manufacturing process.

≪C-1. Base material layer≫
The base material layer may be a single layer or may be two or more layers. The base material layer may be a stretched layer.

The thickness of the substrate layer is preferably 4 μm to 450 μm, more preferably 8 μm to 400 μm, even more preferably 12 μm to 350 μm, and particularly preferably 16 μm to 250 μm.

For the surface of the base layer on which the adhesive layer is not applied, a release treatment can be performed by adding, for example, fatty acid amide, polyethyleneimine, long-chain alkyl additives, etc. to the base layer in order to form a roll that is easy to unwind, or a coating layer made of any suitable release agent, such as a silicone-based, long-chain alkyl-based, or fluorine-based release agent, can be provided.

The material of the substrate layer may be any appropriate material depending on the application. Examples include plastic, paper, metal film, nonwoven fabric, etc. Plastic is preferable. That is, the substrate layer is preferably a plastic film. The substrate layer may be made of one type of material, or may be made of two or more types of materials. For example, it may be made of two or more types of plastic.

Examples of the above plastics include polyester resins, polyamide resins, polyolefin resins, and cycloolefin 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. Specific examples of polyolefin resins include homopolypropylene; propylene copolymers such as block, random, and graft copolymers with ethylene as a copolymerization 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; and the like.

By selecting an appropriate substrate layer, the haze of the protective film of the present invention is preferably 50% or less, more preferably 25%, even 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 have excellent inspectability during the manufacturing process. As the material for such a substrate layer, preferably, a polyester resin or a cycloolefin resin is used.

The substrate layer may contain any suitable additive as necessary. Examples of additives that may be contained in the substrate layer include antioxidants, UV absorbers, light stabilizers, antistatic agents, fillers, and pigments. The type, number, and amount of additives that may be contained in the substrate layer may be appropriately set depending on the purpose. In particular, when the material of the substrate layer is plastic, it is preferable to contain some of the above additives for the purpose of preventing deterioration, etc. From the viewpoint of improving weather resistance, etc., particularly preferred additives include antioxidants, UV absorbers, light stabilizers, and fillers.

Any suitable antioxidant may be used as the antioxidant. Examples of such antioxidants include phenol-based antioxidants, phosphorus-based processing heat stabilizers, lactone-based processing heat stabilizers, sulfur-based heat stabilizers, and phenol-phosphorus-based antioxidants. The content of the antioxidant is preferably 1% by weight or less, more preferably 0.5% by weight or less, and even more preferably 0.01% by weight to 0.2% by weight, based on the base resin of the substrate layer (if the substrate layer is a blend, the blend is the base resin).

Any suitable ultraviolet absorber may be used as the ultraviolet absorber. Examples of such ultraviolet absorbers include benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, and benzophenone-based ultraviolet absorbers. The content of the ultraviolet absorber is preferably 2% by weight or less, more preferably 1% by weight or less, and even more preferably 0.01% by weight to 0.5% by weight, based on the base resin forming the substrate layer (if the substrate layer is a blend, the blend is the base resin).

Any suitable light stabilizer may be used as the light stabilizer. Examples of such light stabilizers include hindered amine light stabilizers and benzoate light stabilizers. The content of the light stabilizer is preferably 2% by weight or less, more preferably 1% by weight or less, and even more preferably 0.01% by weight to 0.5% by weight, based on the base resin forming the substrate layer (if the substrate layer is a blend, the blend is the base resin).

Any suitable filler may be used as the filler. Examples of such fillers include inorganic fillers. Specific examples of inorganic fillers include carbon black, titanium oxide, and zinc oxide. The filler content is preferably 20% by weight or less, more preferably 10% by weight or less, and even more preferably 0.01% by weight to 10% by weight, based on the base resin forming the substrate layer (when the substrate layer is a blend, the blend is the base resin).

Furthermore, as additives, preferred for the purpose of imparting antistatic properties are inorganic, low molecular weight and high molecular weight antistatic agents such as surfactants, inorganic salts, polyhydric alcohols, metal compounds and carbon. In particular, high molecular weight antistatic agents and carbon are preferred from the viewpoints of preventing contamination and maintaining adhesion.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples. The test and evaluation methods in the examples are as follows. Note that "parts" means "parts by weight" unless otherwise specified, and "%" means "% by weight" unless otherwise specified.

<Evaluation of processability>
(Laser light irradiation conditions)
The laser light irradiation device used is as follows.
Laser light source: Carbon dioxide laser Laser wavelength: 10.6m
Spot diameter: 150 μm
Scanning speed: 400 mm/sec
Power: 55W
(evaluation)
A protective film was laminated to polyimide (Kapton 200H, manufactured by Toray DuPont) and cut into a 25 mm x 35 mm square under the above-mentioned laser light irradiation conditions. The cut surface of the processed sample was pressed against glass, and a significant amount of tack was rated as poor, and no noticeable tack was rated as good.

<Evaluation of debris generation suppression effect>
The surface of the processed end on the laser incidence side of the sample after the above processing was observed from the laser incidence side with a laser microscope (VK-9500, manufactured by Keyence Corporation) at a magnification of 50 times. At this time, the brightness of the image was set to 12 dB, and an image was taken of an area of 280 μm × 150 μm from the processed end. The image after the processing was binarized using "Matrox inspector 9.0" (manufactured by Canon IT Solutions Inc.), the area occupied by black spots (debris) was calculated within a threshold range of 0 to 135, and the effect of suppressing debris generation was judged according to the following evaluation criteria.
Black spot (debris) area ratio is 3.00% or less: Suppression effect is good
Black spot (debris) area ratio is over 3.00% and 4.20% or less: Inhibition effect is △
Black spot (debris) area ratio exceeds 4.20%: Inhibition effect is poor

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

[Production Example 1]
Into a polymerization experimental apparatus equipped with a 1 L round-bottom separable flask, a separable cover, a separating funnel, a thermometer, a nitrogen inlet tube, a Liebig condenser, a vacuum seal, a stirring rod, and a stirring blade, 150 g of polypropylene glycol (product name "Sannyx 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 were charged, and nitrogen replacement was carried out at room temperature for 1 hour with stirring. Thereafter, under nitrogen flow and stirring, 22.4 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and the solution temperature in the experimental apparatus was controlled to 90 ± 2 ° C. in a water bath while being held for 4 hours, after which 48.9 g of polypropylene glycol (product name "GP1000", manufactured by Sanyo Chemical Industries, Ltd.) was added, and the solution temperature in the experimental apparatus was controlled to 90 ± 2 ° C. in a water bath while being held for 2 hours, after which 3.1 g of hexamethylene diisocyanate (product name "HDI", manufactured by Tosoh Corporation) was added, and the solution temperature in the experimental apparatus was controlled to 90 ± 2 ° C. in a water bath while being held for 2 hours to obtain a urethane prepolymer solution A. In addition, toluene was appropriately added dropwise during the polymerization to control the temperature during polymerization and to prevent a decrease in stirrability due to an increase in viscosity. The total amount of toluene added was 376 g. The solid content concentration of the urethane prepolymer solution A was 50% by weight.

Example 1
The urethane prepolymer solution A obtained in Production Example 1 was mixed with 100 parts by weight (in terms of polymer solid content), an isocyanate-based crosslinking agent (product name "Coronate HX", manufactured by Tosoh Corporation) in terms of solid content of 3.4 parts by weight, a heat resistance stabilizer (product name "Irganox 1010", manufactured by BASF) in terms of solid content of 0.5 parts by weight, and a silica dispersion (product name "MEK-EC-2130Y", manufactured by Nissan Chemical Industries, Ltd.) in terms of solid content of 10 parts by weight, and the mixture was diluted with ethyl acetate to a total solid content of 45% by weight, thereby obtaining a pressure-sensitive adhesive composition (1).
The obtained pressure-sensitive adhesive composition (1) was applied to a substrate made of polyester resin (product name "T100-75S", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) so as to give a thickness of 75 μm after drying, and cured and dried under conditions of a drying temperature of 130° C. and a drying time of 3 minutes. In this manner, a pressure-sensitive adhesive layer (1) formed from the pressure-sensitive adhesive composition (1) was produced on the substrate.
Next, the silicone-treated surface of a separator made of a polyester resin having a thickness of 25 μm and one side of which was silicone-treated (product name "MRF25", thickness 25 μm, manufactured by Mitsubishi Chemical Corporation) 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 then evaluated. The release sheet was peeled off immediately before the evaluation. The results are shown in Table 1.

[Examples 2 to 6]
Protective films were obtained in the same manner as in Example 1 using pressure-sensitive adhesive compositions (2) to (6) prepared in the same manner as in Example 1, except that the type and amount of silica dispersion were set forth in Table 1. Evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

Example 7
The urethane prepolymer solution A obtained in Production Example 1 was mixed with 100 parts by weight in terms of polymer solid content and 4.4 parts of silica powder (trade name "HM-30S", manufactured by Tokuyama Co., Ltd.), and stirred with a disperser at 1500 rpm for 15 minutes. The urethane prepolymer solution after stirring was filtered through a SUS400 mesh. The filtered solution was mixed with 3.4 parts by weight of an isocyanate 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 Co., Ltd.) in terms of solid content, and 10 parts by weight of a silica dispersion (trade name "MEK-EC-2130Y", manufactured by Nissan Chemical Industries Co., Ltd.) in terms of solid content, and diluted with ethyl acetate so that the total solid content was 45% by weight to obtain a pressure-sensitive adhesive composition (7).
The obtained pressure-sensitive adhesive composition (7) was used to obtain a protective film in the same manner as in Example 1. Furthermore, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

[Examples 8 to 26]
Protective films were obtained in the same manner as in Example 1 using pressure-sensitive adhesive compositions (8) to (26) prepared in the same manner as in Example 1, replacing the silica dispersion with a metal oxide dispersion shown in Table 1, and changing the type and amount of each to those shown in Table 1. Evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1
A pressure-sensitive adhesive composition (C1) was prepared in the same manner as in Example 1, except that the silica dispersion was not added. A protective film was obtained using the prepared pressure-sensitive adhesive composition (C1) in the same manner as in Example 1. Furthermore, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

The protective film of the present invention can be used for any suitable application. Preferably, the protective film of the present invention is used in the fields of optical components and electronic components.

10: Base layer 20: Pressure-sensitive adhesive layer 100: Protective film

Claims (5)

A protective film having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition,
The haze of the protective film is 2.10% or less,
The pressure-sensitive adhesive composition comprises:
A pressure-sensitive adhesive composition comprising a base polymer,
the base polymer is a urethane prepolymer,
Contains silica particles having an average primary particle size of 1 nm to 300 nm;
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 . A pressure-sensitive adhesive composition comprising a base polymer,
the base polymer is a urethane prepolymer,
Contains Na ₃ AlF ₆ particles having an average primary particle size of 5 nm to 50 nm;
Adhesive composition. A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to claim 2 . A protective film having the adhesive layer according to claim 3. The protective film according to claim 4, having a haze of 5% or less.