JP6801821B2 - Urethane adhesive and adhesive sheet - Google Patents

Description

The present invention relates to urethane pressure-sensitive adhesives and pressure-sensitive adhesive sheets.

A surface protective film is used for the purpose of preventing the surface of various base materials from being soiled or scratched. The surface protective film is attached to, for example, an optical member or the like in the manufacturing process of a display device, and is peeled off from the optical member or the like when the surface protection becomes unnecessary.
As such a surface protective film, a urethane prepolymer (molecular weight dispersion degree) obtained by reacting a polyol containing a polyether polyol having 3 or more hydroxyl groups with a polyisocyanate at a molar ratio of NCO / OH ratio of 0.5 to 0.9. Adhesives containing 4 to 12) are known (see, for example, Patent Document 1). Further, there is known an adhesive sheet containing a urethane polymer and a vinyl polymer and having an intermediate layer having a reduced content of a component having a molecular weight of 10,000 or less (see, for example, Patent Document 2).

Japanese Patent No. 6014926 Japanese Patent No. 6123145

However, when the conventionally known adhesives described in Patent Documents 1 and 2 are used for the surface protective film, the surface properties of the optical member, various base materials, and the like may change before and after the peeling. The present invention has been made in view of the above circumstances, and provides an adhesive composition capable of forming a surface protective film in which changes in surface characteristics of an optical member, various substrates, etc. are suppressed before and after peeling. With the goal.

The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing a urethane resin (A) and a curing agent (B), and the urethane resin (A) is a compound having two or more groups having active hydrogen atoms. The compound (a1), which is a reaction product of (a1) and polyisocyanate (a2) and has two or more groups having active hydrogen atoms, contains 10% by mass or more of oxyalkylene units having 4 or more carbon atoms. The proportion of the component which contains the polyether polyol having a ratio and has a maximum value in the range of the weight average molecular weight of 2,000 or more and 6,000 or less is 5% by mass or less in 100% by mass of the urethane resin (A). It is characterized by being.

The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention can suppress changes in surface characteristics of optical members, various substrates, etc. before and after peeling.

The pressure-sensitive adhesive composition of the present invention contains a urethane resin (A) and a curing agent (B), and the urethane resin (A) contains a compound (a1) having two or more active hydrogen atoms and a polyisocyanate (a 1). It is a reaction product of a2).

In the compound (a1) having two or more groups having an active hydrogen atom (hereinafter, may be simply referred to as "compound (a1)"), the groups having the active hydrogen atom include -OH group and -NH. _Two groups, -NH- group and the like can be mentioned. The compound (a1) contains a polyether polyol. The polyether polyol is a compound obtained by addition polymerization of alkylene oxide using one or more of compounds having two or more active hydrogen atoms (for example, a molecular weight of 50 or more and less than 500) as an initiator, or the active hydrogen. Examples thereof include ring-opening polymerization of cyclic ether using one or more compounds having two or more atoms (for example, a molecular weight of 50 or more and less than 500) as an initiator, if necessary.

As the compound having two or more active hydrogen atoms, one type or two or more types can be used, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, and the like. Examples thereof include 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, bisphenol A, glycerin, trimethylolethane, and trimethylolpropane.

As the alkylene oxide, one kind or two or more kinds can be used, and examples thereof include ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin and the like. Examples of the cyclic ether include tetrahydrofuran, alkyl-substituted tetrahydrofuran and the like.

Examples of the polyether polyol include polypropylene glycol, polytetramethylene glycol, a polytetramethylene glycol derivative obtained by reacting tetrahydrofuran with alkyl-substituted tetrahydrofuran, and polytetramethylene glycol obtained by copolymerizing neopentyl glycol and tetrahydrofuran. Derivatives and the like can be used. Of these, polypropylene glycol, polytetramethylene glycol (PTMG), and polytetramethylene glycol derivative (PTXG) are preferable as the polyether polyol.

The polyether polyol includes at least a polyether polyol having an oxyalkylene unit having 4 or more carbon atoms in a proportion of 10% by mass or more. By containing an oxyalkylene unit having 4 or more carbon atoms, it becomes easy to suppress changes in surface characteristics.

In a polyether polyol having an oxyalkylene unit having 4 or more carbon atoms in a proportion of 10% by mass or more, the carbon atom number of the oxyalkylene unit is preferably 4 or more and 6 or less, more preferably 4 or more. It is 5 or less, particularly preferably 4. The content of the oxyalkylene unit is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more, still more preferably 90% by mass or more, and the upper limit is 100% by mass. Is.

The number of groups having an active hydrogen atom contained in the polyether polyol having an oxyalkylene unit having 4 or more carbon atoms in a proportion of 10% by mass or more is preferably 2 or more and 4 or less, particularly preferably 2. ..

The number average molecular weight of the polyether polyol having an oxyalkylene unit having 4 or more carbon atoms in a proportion of 10% by mass or more is preferably 500 or more, more preferably 800 or more, still more preferably 900 or more, and preferably 900 or more. Is 2,500 or less, more preferably 1,800 or less, still more preferably 1,500 or less, and particularly preferably 1,200 or less.
In the present specification, the number average molecular weight and the weight average molecular weight represent values measured by gel permeation chromatography in terms of polystyrene.

The content of the polyether polyol having an oxyalkylene unit having 4 or more carbon atoms in a proportion of 10% by mass or more is preferably 50% by mass or more, more preferably 70% by mass or more, and further, among the polyether polyols. It is preferably 90% by mass or more, and the upper limit is 100% by mass.
The content of the polyether polyol is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and preferably 100% by mass or less, more preferably 100% by mass or more, in the compound (a1). Is 99% by mass or less.

The compound (a1) having two or more groups having an active hydrogen atom preferably further contains a low molecular weight polyol (preferably a low molecular weight diol). The number average molecular weight of the low molecular weight polyol is preferably 50 or more and less than 500, more preferably 50 or more and 400 or less, and further preferably 50 or more and 300 or less.

Examples of the low molecular weight polyol include aliphatic alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, and 1,3-butanediol; cyclohexanedimethanol and the like. The alicyclic glycol and the like can be mentioned.

The content of the low molecular weight polyol is preferably 0.1% by mass or more, more preferably 1% by mass or more, still more preferably 3% by mass or more, and preferably 20% by mass or less in the compound (a1). It is more preferably 10% by mass or less, still more preferably 7% by mass or less.

The total content of the polyether polyol having an oxyalkylene unit having 4 or more carbon atoms in a proportion of 10% by mass or more and the low molecular weight polyol is a compound having two or more groups having the active hydrogen atom. In (a1), it is preferably 70% by mass or more, more preferably 85% by mass or more, still more preferably 95% by mass or more, and preferably 100% by mass or less.

The compound (a1) having two or more groups having an active hydrogen atom may further contain a polycarbonate polyol and a polyester polyol.

As the polycarbonate polyol, for example, one obtained by reacting a carbonic acid ester and / or phosgene with a low molecular weight polyol described later can be used.
As the carbonic acid ester, for example, methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonate, diphenyl carbonate and the like can be used.

Examples of the low molecular weight polyol that can react with the carbonate ester and phosgen include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, and tri. Propropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexane Diol, 2,5-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol , 2-Methyl-1,3-propanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3- Examples thereof include hexanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanedimethanol, hydroquinone, resorcin, bisphenol A, bisphenol F, and 4,4'-biphenol.

Examples of the polycarbonate polyol include dialkyl carbonate, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol and the like. Aliphatic polycarbonate polyol; alicyclic polycarbonate polyol and the like can be mentioned.

Examples of the polyester polyol include an esterification reaction product of the low molecular weight polyol and a polycarboxylic acid; a ring-opening polymer of a cyclic ester compound such as ε-caprolactone; and a copolymerized polyester of the esterification reaction product and the ring-opening polymer. Etc. can be used.

Examples of the polycarboxylic acid include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and dodecanedicarboxylic acid, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid, and Examples thereof include anhydrides or esterified products thereof.

As the polyisocyanate (a2), one type or two or more types can be used, for example, diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, phenylenediisocyanate, trienediisocyanate, naphthalene. Aromatic polyisocyanates such as diisocyanate, xylylene diisocyanate and tetramethylxylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate and lysine diisocyanate; isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 4,4' −Dicyclohexylmethane diisocyanate, 2,4- and / or 2,6-methylcyclohexanediisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis (2-isocyanatoethyl) -4-cyclohexylene-1,2-dicarboxylate And 2,5- and / or 2,6-norbornandiisocyanate, diisocyanate dimerate, bicycloheptanetriisocyanate, alicyclic polyisocyanate such as hydrogenated xylylene diisocyanate and the like. Of these, aliphatic polyisocyanates and alicyclic polyisocyanates are preferable.

The molar ratio (isocyanate group / active hydrogen atom) of the isocyanate group contained in the polyisocyanate (a2) to the group having an active hydrogen atom contained in the compound (a1) having two or more groups having an active hydrogen atom. The number of groups) is 0.5 or more, preferably 0.7 or more, more preferably 0.8 or more, still more preferably 0.85 or more, less than 1, preferably 1 or less, and more preferably 0. It is 95 or less.

The urethane resin (A) may be a reaction product of a compound (a1) having two or more groups having an active hydrogen atom and a polyisocyanate (a2), to which a chain extender is further added.

As the chain extender, one kind or two or more kinds can be used, and compounds having two or more active hydrogen atoms can be used, and examples thereof include ethylene glycol, 1,2-propanediol, and 1,3-butanediol. , 1,4-Butanediol, 2,3-Butanediol, 3-Methyl-1,5-Pentanediol, 1,6-Hexanediol, 3,3'-Dimethylol heptan, Neopentyl glycol, 3,3- Alibo chain extenders such as bis (hydroxymethyl) heptane, diethylene glycol, dipropylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, glycerin, trimethylolpropane; 1,2-cyclobutanediol, 1,3-cyclopentane Diol, 1,4-cyclohexanediol, cycloheptanediol, cyclooctanediol, 1,4-cyclohexanedimethanol, hydroxypropylcyclohexanol, tricyclo [5.2.1.0 ^2,6 ] decan-dimethanol, bicyclo [ 4.3.0] -Nonandiol, Dicyclohexanediol, Bicyclo [4.3.0] Nonandimethanol, Spiro [3.4] Octanediol, Butylcyclohexanediol, 1,1'-bicyclohexylidenediol, Alicyclic chain extenders such as cyclohexanetriol, hydrogenated bisphenyl A, and 1,3-adamantandiol; alkanolamine compounds such as alkanolamine and alkanoldiamine can be mentioned.

Above all, the chain extender preferably contains the alkanolamine compound. The molecular weight of the alkanolamine compound is preferably 50 or more and less than 500, more preferably 50 or more and 400 or less, and further preferably 50 or more and 300 or less.

The alkanolamine compound is preferably represented by the following formula (1).

［式（１）中、Ｒ¹及びＲ²は、それぞれ独立に、炭素原子数１以上１０以下の２価の炭化水素基を表す。］

[In formula (1), R ¹ and R ² independently represent divalent hydrocarbon groups having 1 or more and 10 or less carbon atoms. ]

The divalent hydrocarbon group represented by R ¹ or R ² includes a methylene group, an ethylene group, a propylene group, a butylene group, a pentandiyl group, a hexanediyl group, a heptandiyl group, an octanediyl group, a nonandiyl group and a decandyl group. Such as an alkandiyl group.
The number of carbon atoms of the divalent hydrocarbon group represented by R ¹ or R ² is preferably 2 or more, preferably 7 or less, more preferably 5 or less, and further preferably 4 or less.

The content of the alkanolamine compound is preferably 80% by mass or more, more preferably 90% by mass or more, and the upper limit is 100% by mass in the chain extender.

When the chain extender is contained, the content thereof is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, based on the compound (a1). It is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less.

The urethane resin (A) is prepared by adding a chain extender to a reaction product of a compound (a1) having two or more groups having active hydrogen atoms and a polyisocyanate (a2), if necessary, and further adding a terminal terminator. It may be a reaction. By using a terminal terminator, the isocyanate group can be inactivated.

The terminal terminator is preferably an alcohol, and examples thereof include monofunctional alcohols such as methanol, ethanol, propanol and butanol; and bifunctional alcohols such as 1,2-propylene glycol and 1,3-butylene glycol.

When the terminal terminator is used, the molar ratio of the group having an active hydrogen atom contained in the terminator to the isocyanate group contained in the polyisocyanate (a2) is preferably 0.01 or more, more preferably 0. It is 0.03 or more, more preferably 0.04 or more, preferably 0.5 or less, more preferably 0.2 or less, still more preferably 0.1 or less.

In the urethane resin (A), the proportion of components having a maximum value in the range of weight average molecular weight of 2,000 or more and 6,000 or less is 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass. % Or less, more preferably 0.5% by mass or less, and the lower limit is more than 0% by mass. By suppressing the proportion of the component having the maximum value in the range of the weight average molecular weight of 2,000 or more and 6,000 or less, the change in the surface characteristics of the adherend surface can be suppressed.

The number average molecular weight of the urethane resin (A) is preferably 7,000 or more, more preferably 9,000 or more, still more preferably 10,000 or more, preferably 50,000 or less, and more preferably 30,000. Below, it is more preferably 20,000 or less.
The weight average molecular weight of the urethane resin (A) is preferably 10,000 or more, more preferably 20,000 or more, still more preferably 30,000 or more, preferably 100,000 or less, and more preferably 70,000. Below, it is more preferably 50,000 or less.
The molecular weight dispersion of the urethane resin (A) is preferably 1.8 or more, more preferably 2 or more, still more preferably 2.3 or more, preferably 7 or less, and more preferably 5 or less.

The urethane resin (A) is reacted with a compound (a1) having two or more groups having active hydrogen atoms and a polyisocyanate (a2), and if necessary, a chain extender and / or a terminal terminator is further reacted. It can be manufactured by. The reaction may be carried out in the presence of an organic solvent or an aqueous medium, and a urethanization catalyst may be allowed to coexist in the reaction.

As the organic solvent, one kind or two or more kinds can be used, for example, alcohol solvents such as methanol, ethanol, n-propanol and 2-propanol; ketone solvents such as acetone and methyl ethyl ketone; ethylene glycol, diethylene glycol and propylene. Polyhydric alcohol solvents such as glycol, polyalkylene glycol and glycerin; ether solvents such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether and ethyl carbitol; N-methyl-2-pyrrolidone and the like Examples include the amide solvent of. Examples of the aqueous medium include a mixed solvent of the organic solvent and water.
Examples of the urethanization catalyst include nitrogen-containing compounds such as triethylamine, triethylenediamine and N-methylmorpholine, metal salts such as potassium acetate, zinc stearate and tin octylate, dibutyltin laurate, dioctyltin dineodecanate and zirconium tetraacetyl. Organic metal compounds such as acetonate can be used.

The curing agent (B) is a component that cross-links the hydroxyl group contained in the urethane resin (A), and a polyisocyanate curing agent is preferable. For example, tolylene diisocyanate, chlorophenylenediocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate. , Xylylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate and other polyisocyanates; these trimethylolpropane adducts; these isocyanurates; these bullets and the like can be used. Among these, it is preferable to use a trimethylolpropane adduct of polyisocyanate or an isocyanurate form of polyisocyanate from the viewpoint that changes in surface characteristics of optical members and the like can be further suppressed before and after peeling.

The content of the curing agent (B) is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and preferably 10 parts by mass with respect to 100 parts by mass of the urethane resin (A). Hereinafter, it is more preferably 7 parts by mass or less.

The total content of the urethane resin (A) and the curing agent (B) is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass, based on the solid content of the pressure-sensitive adhesive composition. % Or more, preferably 100% by mass or less.
In the present specification, the solid content of the pressure-sensitive adhesive composition means a portion of the pressure-sensitive adhesive composition excluding the solvent.

The pressure-sensitive adhesive composition may further contain a curing catalyst. Examples of the curing catalyst include compounds similar to the compounds exemplified as the urethanization catalyst. When the curing catalyst is contained, the content thereof is preferably 0.001 part by mass or more, more preferably 0.005 part by mass or more, and further preferably 0.01 with respect to 100 parts by mass of the urethane resin (A). It is more than parts by mass, preferably 1 part by mass or less, more preferably 0.1 part by mass or less, and further preferably 0.05 part by mass or less.

The pressure-sensitive adhesive composition may further contain a solvent. Examples of the solvent include compounds similar to the compounds exemplified as the organic solvent. When the organic solvent is contained, the content thereof in the pressure-sensitive adhesive composition is preferably 20% by mass or more, more preferably 30% by mass or more, preferably 80% by mass or less, and more preferably 70% by mass or less. Is.

The pressure-sensitive adhesive composition further includes, as other additives, a silane coupling agent, an antioxidant, a light stabilizer, a rust preventive, a thixo-imparting agent, a sensitizer, a polymerization inhibitor, a leveling agent, and a pressure-imparting agent. It may contain an agent, an antistatic agent, a flame retardant and the like. The content of the other additive is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, and the lower limit is 0% by mass in the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition, can be formed by applying the pressure-sensitive adhesive composition to a base material, removing a solvent if necessary, and further aging if necessary. .. The thickness of the adhesive layer is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 30 μm or more, preferably 200 μm or less, more preferably 100 μm or less, still more preferably 80 μm or less.

When applying the pressure-sensitive adhesive composition to a substrate, an applicator, a roll coater, a knife coater, a gravure coater, or the like can be used.
As the base material, for example, a plastic base material, a flexible printed base material, a glass base material, a base material obtained by subjecting these base materials to a mold release treatment, a base material on which ITO (indium tin oxide) is vapor-deposited, or the like is used. Can be done. Examples of the plastic base material include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, diacetyl cellulose film, triacetyl cellulose film, acetyl cellulose butyrate film, and polyvinyl chloride film. Polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film, polymethylpentene film, polysulfone film, polyether ether ketone film, polyether sulfone film, polyetherimide film, polyimide film , Fluorine resin film, nylon film, acrylic resin film and the like can be used.

Examples of the glass member include tempered glass and the like. The tempered glass is glass having a compressive stress layer provided on its surface, and has higher strength than ordinary flat glass. Examples of the strengthening method include physical strengthening and chemical strengthening, and chemical strengthening is preferable. Examples of the chemical tempering method include a method of introducing cations (alkali metal ions, etc.) having a large ion radius into the surface by ion exchange below the melting point of the glass. Examples of the tempered glass strengthened by this method include. , Corning's gorilla glass and the like.
The surface hardness of the tempered glass is preferably 5H or more, more preferably 9H or more.

The thickness of the base material is preferably 0.1 mm or more, more preferably 0.2 mm or more, preferably 0.6 mm or less, and more preferably 0.5 mm or less.

The pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive composition, can suppress changes in the surface characteristics of the base material before and after its peeling, and can be used as a surface protective film, and in particular, a display device or the like. It is useful as a surface protective film for protecting the information display part of electronic devices.

Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples.

(Manufacturing Example 1: Production of Urethane Resin (I))
Polytetramethylene ether glycol (number average molecular weight: 1,016.4, hydroxyl value: 110.4) 595 in a four-necked flask equipped with a stirrer, a reflux cooling tube, a thermometer and a nitrogen blowing tube under a nitrogen stream. After adding .76 parts by mass, neopentyl glycol 32.42 parts by mass and methyl ethyl ketone 527.97 parts by mass and mixing uniformly, hexamethylene diisocyanate 163.77 parts by mass was added, and then 0.1 parts by mass of dibutyltin dilaurate was added. In addition, a methyl ethyl ketone solution of a urethane prepolymer having an isocyanate group at the molecular terminal (mass ratio of isocyanate group to the urethane prepolymer (isocyanate group content); 0.49% by mass) by reacting at 75 ° C. for about 11 hours. (Solid content 60%) was obtained.

Next, the methyl ethyl ketone solution of the urethane prepolymer obtained by the above method was cooled to 40 ° C., 1.99 parts by mass of 2- (2-aminoethylamino) ethanol was added as a chain extender, and the mixture was uniformly mixed and then 40. The reaction was carried out at ° C. When the NCO% became 0.36% or less, 12.03 parts by mass of diethanolamine, which is a terminal terminator, was added to confirm that the NCO had disappeared, and 129.67 parts by mass of methyl ethyl ketone was added, and then the temperature reached room temperature. The mixture was cooled to obtain a methyl ethyl ketone solution (solid content 55%) of the urethane resin (I). In the molecular weight distribution of this urethane resin (I) by GPC, only one peak having a maximum weight average molecular weight of 53,259 was detected, the number average molecular weight (Mn) was 11,026, and the weight average molecular weight (Mw). Was 53,259, and the molecular weight dispersion (Mw / Mn) was 4.83. The molar ratio (NCO / group having an active hydrogen atom) was 0.88.

(Manufacturing example 2: Production of urethane resin (II))
Polytetramethylene ether glycol (number average molecular weight: 1,016.4, hydroxyl value: 110.4) 705 in a four-necked flask equipped with a stirrer, a reflux cooling tube, a thermometer and a nitrogen blowing tube under a nitrogen stream. .73 parts by mass, 1,4-butanediol 32.47 parts by mass, ethyl acetate 246.09 parts by mass were added and mixed uniformly, then isophorone diisocyanate 246.15 parts by mass was added, and then dibutyltin dilaurate 0.3. By adding a mass part and reacting at 75 ° C. for about 11 hours, a urethane prepolymer having an isocyanate group at the molecular terminal (mass ratio of isocyanate group to the urethane prepolymer (isocyanate group content); 0.25 mass%). An ethyl acetate solution (solid content 55%) was obtained.
Next, the ethyl acetate solution of the urethane prepolymer obtained by the above method was cooled to 40 ° C., 11.09 parts by mass of diethanolamine as a terminal terminator was added, and it was confirmed that NCO disappeared. Ethyl acetate 190. After adding 06 parts by mass, the mixture was cooled to room temperature to obtain an ethyl acetate solution (solid content 50%) of urethane resin (II). In the molecular weight distribution of this urethane resin (II) by GPC, only one peak having a maximum weight average molecular weight of 32,550 was detected, the number average molecular weight (Mn) was 12,549, and the weight average molecular weight (Mw). Was 32,550, and the molecular weight dispersion (Mw / Mn) was 1.83. The molar ratio (NCO / group having an active hydrogen atom) was 0.91.

(Manufacturing Example 3: Production of Urethane Resin (III))
Polypropylene glycol (number average molecular weight: 1,010.9, hydroxyl value: 111.0) 641.72 mass in a four-necked flask equipped with a stirrer, a reflux cooling tube, a thermometer and a nitrogen blower under a nitrogen stream. Parts, polypropylene glycol (number average molecular weight: 400.76, hydroxyl value: 280.0) 264.30 parts by mass and methyl ethyl ketone 486.26 parts by mass were added and mixed uniformly, and then hexamethylene diisocyanate 228.59 parts by mass was added. In addition, 0.1 part by mass of dibutyltin dilaurate is then added and reacted at 75 ° C. for about 11 hours to cause a urethane prepolymer having an isocyanate group at the molecular terminal (mass ratio of isocyanate group to the urethane prepolymer (containing isocyanate group). Amount); 0.29% by mass) of a methyl ethyl ketone solution (solid content 60%) was obtained.

Next, the methyl ethyl ketone solution of the urethane prepolymer obtained by the above method was cooled to 40 ° C., 1.69 parts by mass of 2- (2-aminoethylamino) ethanol was added as a chain extender, and the mixture was uniformly mixed and then 40. The reaction was carried out at ° C. When the NCO% became 0.22% or less, 10.21 parts by mass of diethanolamine, which is a terminal terminator, was added, and after confirming that the NCO had disappeared, the mixture was cooled to room temperature, and a methyl ethyl ketone solution of urethane resin (III) was used. (Solid content 60.2%) was obtained. In the molecular weight distribution of this urethane resin (III) by GPC, only one peak having a maximum weight average molecular weight of 51,631 was detected, the number average molecular weight (Mn) was 17,138, and the weight average molecular weight (Mw). Was 51,631, and the molecular weight dispersion (Mw / Mn) was 3.01. The molar ratio (NCO / group having an active hydrogen atom) was 0.93.

(Manufacturing Example 4: Production of Urethane Resin (IV))
Introducing a hydroxyl group into the urethane skeleton with a trifunctional polyol In a four-necked flask equipped with a stirrer, a reflux cooling tube, a thermometer and a nitrogen blower, polypropylene glycol (number average molecular weight: 3,108.3,) under a nitrogen stream. Hydroxyl group value: 36.1) 621.66 parts by mass and 292.18 parts by mass of ethyl acetate were added and mixed uniformly, then 60.55 parts by mass of hexamethylene diisocyanate was added, and then 0.02 parts by mass of dioctyltin dineodecaneate was added. In addition, by reacting at 75 ° C. for about 4 hours, ethyl acetate of a urethane prepolymer having an isocyanate group at the molecular terminal (mass ratio of isocyanate group to the urethane prepolymer (isocyanate group content); 1.38% by mass). A solution (solid content 70%) was obtained.
Next, the ethyl acetate solution of the urethane prepolymer obtained by the above method was cooled to 40 ° C., and polyoxyethylene polyoxypropylene triol (“Sannicks GL-3000” manufactured by Sanyo Kasei Co., Ltd., molar ratio [EO / PO]]. = 25/75, number average molecular weight; 3,077.1, hydroxyl value: 54.7) 574.38 parts by mass and ethyl acetate 126.49 parts by mass were added and mixed uniformly, and then at 65 ° C. for about 6 hours. After the reaction, the mixture was cooled to 60 ° C. when the NCO% became 0.01% or less, and 3.14 parts by mass of methanol as a terminal terminator was added to confirm that the NCO had disappeared, and the mixture was cooled to room temperature. Then, an ethyl acetate solution (solid content 75%) of urethane resin (IV) was obtained. In the molecular weight distribution of this urethane resin (IV) by GPC, two peaks, a peak A having a maximum weight average molecular weight of 77,428 and a peak B having a maximum weight average molecular weight of 3,011 were detected. The number average molecular weight (Mn) of peak A was 23,662, the weight average molecular weight (Mw) was 77,428, and the molecular weight dispersion (Mw / Mn) was 3.27. The proportion of the component having a maximum value in the range of weight average molecular weight of 2,000 or more and 6,000 or less was 7.98% in 100% by mass of the urethane resin (IV).
The molar ratio (NCO / group having an active hydrogen atom) was 0.93.

(Example 1: Urethane resin (I))
Immediately before producing a sheet, 100 parts by mass of the methyl ethyl ketone solution (solid content 55%) of the urethane resin (I) obtained in Production Example 1 was subjected to a hexamethylene diisocyanate nurate (Duranate TKA manufactured by Asahi Kasei Corporation) as a cross-linking agent. -100 ", hereinafter abbreviated as" TKA-100 ") is 4.70 parts by mass, 1.02 parts by mass of a 1% methylethylketone solution of dioctyltin dineodecaneate as a curing catalyst, 0.83 parts by mass of acetylacetone, and methylethylketone 42. 70 parts by mass was blended to obtain a pressure-sensitive adhesive composition (A) (solid content 40%).

(Example 2: Urethane resin (II))
Immediately before producing a sheet, in 100 parts by mass of the ethyl acetate solution (solid content 50%) of the urethane resin (II) obtained in Production Example 2, 3.62 parts by mass of "TKA-100" was cured as a cross-linking agent. As a catalyst, 0.93 parts by mass of a 1% ethyl acetate solution of dioctyltin dineodecaneate, 0.75 parts by mass of acetylacetone, and 13.86 parts by mass of ethyl acetate were blended to prepare a pressure-sensitive adhesive composition (B) (solid content 45%). Obtained.

(Comparative Example 1: Urethane Resin (III))
Immediately before producing the sheet, 2.65 parts by mass of "TKA-100" as a cross-linking agent was added to 100 parts by mass of the methyl ethyl ketone solution (solid content 60.2%) of the urethane resin (III) obtained in Production Example 3. 2.10 parts by mass of methyl ethyl ketone was blended to obtain a pressure-sensitive adhesive composition (C) (solid content 60%).

(Comparative Example 2: Urethane Resin (IV))
Just before producing the sheet, in 100 parts by mass of the ethyl acetate solution (solid content 75%) of the urethane resin (IV) obtained in Production Example 4, 6.34 parts by mass of "TKA-100" as a cross-linking agent, acetate. 29.22 parts by mass of ethyl was blended to obtain a pressure-sensitive adhesive composition (D) (solid content 60%).

[GPC measurement method]
Measuring device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series and used.
"TSKgel G5000" (7.8 mm I.D. x 30 cm) x 1 "TSKgel G4000" (7.8 mm I.D. x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 This "TSKgel G2000" (7.8 mm ID x 30 cm) x 1 Detector: RI (Differential Refractometer)
Column temperature: 40 ° C
Eluent: tetrahydrofuran (THF)
Flow rate: 1.0 mL / min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4% by mass)
Standard sample: A calibration curve was prepared using the following standard polystyrene.
(Standard polystyrene)
"TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

[Adhesive sheet processing method]
The obtained pressure-sensitive adhesive composition was applied to the surface of a polyethylene terephthalate film having a thickness of 50 μm so that the film thickness after drying was 65 μm, and dried at 60 ° C. for 3 minutes and further at 100 ° C. for 4 minutes. .. A 38 μm-thick polyethylene terephthalate film whose surface was mold-released was attached to this and cured at 40 ° C. for 3 days to obtain an adhesive sheet.

[Evaluation method of surface properties]
The surface protective film obtained in Examples and Comparative Examples was cut into 20 mm × 60 mm and used as a test piece. The release film was peeled off from the test piece and attached to the glass plate by reciprocating twice with a 2 kg roll. After the pasting, the mixture was left to stand for 1 hour under the condition of 80 ° C., then left for 1 hour in an environment of 23 ° C., the test piece was peeled off, and the water contact angle B of the glass plate was measured. Further, the water contact angle A of the glass plate to which the test piece was not attached was measured.
The absolute value of the difference between the water contact angles A and B was calculated and evaluated as follows.
◯; 0.0 to 2.0
Δ; 2.0 to 4.0
×; 4.0 or more

[Measurement method of adhesive strength]
The surface protective film obtained in Examples and Comparative Examples was cut into a width of 20 mm and used as a test piece. The release film was peeled off from the test piece and attached to the glass plate by reciprocating twice with a 2 kg roll so that the adhesive area was 20 mm × 60 mm. Twenty-four hours after the application, the peel strength was 180 degrees in an atmosphere of 23 ° C. and 50% humidity to obtain an initial adhesive strength (N / 25 mm) A. Further, after the above-mentioned attachment, the mixture was left to stand for 1 hour under the condition of 80 ° C., then left for 1 hour in an environment of 23 ° C., and then peeled at 180 ° C. ..
The rate of increase between the adhesive strengths A and B (%, "adhesive strength B" / [adhesive strength A]) was calculated and evaluated as follows.
⊚; 100% or more and less than 300% ○; 300% or more and less than 500% Δ; 500% or more and less than 1700% ×; 1700% or more

The above evaluation results are shown in Table 1.

Examples 1 and 2 are examples of the present invention, and it was possible to suppress changes in the surface characteristics of the base material before and after peeling. On the other hand, in Comparative Examples 1 and 2, the proportion of the oxyalkylene unit having 4 or more carbon atoms was less than 10% by mass, and the water contact angle of the base material decreased before and after the peeling.

Claims (7)

A pressure-sensitive adhesive composition containing a urethane resin (A) and a curing agent (B), wherein the urethane resin (A) has two or more groups having an active hydrogen atom (a1) and a polyisocyanate (a2). The compound (a1) having two or more groups having active hydrogen atoms is a low molecular weight polyol having a number average molecular weight of 3 to 20% by mass of 50 or more and 300 or less, and having 4 or more carbon atoms. The urethane resin contains a polyether polyol having an oxyalkylene unit of 10% by mass or more, and has a maximum value in the range of a weight average molecular weight of 2,000 or more and 6,000 or less. A) A pressure-sensitive adhesive composition, which is 5% by mass or less in 100% by mass. It has a molar ratio (having an isocyanate group / active hydrogen atom) of an isocyanate group contained in the polyisocyanate (a2) and a group having an active hydrogen atom contained in the compound (a1) having two or more groups having an active hydrogen atom. The pressure-sensitive adhesive composition according to claim 1, wherein the group) is 0.5 or more and less than 1. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the urethane resin (A) has a weight average molecular weight of 100,000 or less. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the degree of molecular weight dispersion (weight average molecular weight / number average molecular weight) of the urethane resin (A) is 5 or less. Claim 1 in which the urethane resin (A) is a reaction product of the compound (a1) having two or more groups having active hydrogen atoms and a polyisocyanate (a2), to which a chain extender is further added. The pressure-sensitive adhesive composition according to any one of Items to 4. An adhesive layer which is a cured product of the adhesive composition according to claim 5. A surface protective film having a base material and the adhesive layer according to claim 6.