JP6597727B2 - Surface protective adhesive and adhesive sheet - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive for surface protection and a pressure-sensitive adhesive sheet.

  Conventionally, surface protective sheets have been used to prevent various members from being damaged. In forming the adhesive layer of the surface protective sheet, an adhesive containing an acrylic resin or a urethane resin is often used. Among them, the adhesive containing urethane resin (hereinafter referred to as urethane adhesive) is used for surface protection of displays such as liquid crystal displays because it has moderate adhesive strength and removability to glass. Has been.

  For example, Patent Document 1 discloses a pressure-sensitive adhesive containing a urethane resin, an isocyanate curing agent, and at least one compound selected from a polyalkylene glycol compound, an epoxy compound, and a phosphate ester compound. Yes.

  As a pressure-sensitive adhesive using a urethane urea resin having high adhesive strength, Patent Document 2 discloses a pressure-sensitive adhesive containing a urethane urea resin obtained by reacting a trivalent or higher polyol, polyisocyanate, and monoamino polyol, and an isocyanate curing agent. Is disclosed.

  Patent Document 3 discloses a pressure-sensitive adhesive containing an isocyanate group-terminated prepolymer obtained by reacting a polyol and a polyisocyanate compound, a urethane urea resin obtained by reacting a chain extender and a terminal terminator, and an isocyanate curing agent. Has been.

Japanese Patent Laying-Open No. 2015-7226 JP 2007-023117 A JP 2006-124692 A

However, since the adhesive of Patent Document 1 has low adhesive strength, for example, when protecting the surface of a display having a curved surface portion, there is a problem that the adhesive sheet floats or peels from the curved surface portion.
Moreover, since the adhesive of patent document 2 has many branches of urethane urea resin and is a three-dimensional structure, when this adhesive was processed into the surface protection sheet, the cohesion force of the adhesion layer was excessive. For this reason, there is a problem that floating occurs when the surface protection sheet is attached to the curved surface portion.
Moreover, since the hydroxyl group formed from the reaction of the isocyanate group-terminated prepolymer and the chain extender has a secondary hydroxyl group, the pressure-sensitive adhesive of Patent Document 3 takes a long time to cure with the isocyanate curing agent, and protects the pressure-sensitive adhesive sheet. There was a productivity problem that took a long time to use for the purpose.

  The present invention provides surface protection for producing a pressure-sensitive adhesive sheet that has good wettability to an adherend, hardly floats and peels off when attached to a curved surface, can be re-peeled, and has good productivity. The purpose is to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet.

  The pressure-sensitive adhesive for surface protection of the present invention comprises an isocyanate curing agent (B) with respect to 100 parts by mass of a urethane urea resin (A) that is a reaction product of an isocyanate group-containing urethane prepolymer (a) and an amine compound (b). More than 3 parts by mass and 20 parts by mass or less, and the urethane urea resin (A) has a molecular weight dispersity of 1.5-6.

  According to the present invention, the wettability with respect to the adherend is good, the sticking to the curved surface portion is unlikely to be lifted and peeled off, re-peeling is possible, and the productivity is good for producing a pressure-sensitive adhesive sheet. A pressure-sensitive adhesive for surface protection and a pressure-sensitive adhesive sheet can be provided.

Before describing the present invention, terms will be defined. In this specification, the adherend refers to a partner to which an adhesive tape is attached. In the present specification, the molecular weight dispersity is a numerical value obtained by dividing the weight average molecular weight by the number average molecular weight, and is a measure of the molecular weight distribution.
In this specification, productivity refers to the pressure-sensitive adhesive layer, since the cohesive force of the pressure-sensitive adhesive layer is rapidly expressed when the pressure-sensitive adhesive is applied (because crosslinking proceeds with a small amount of heat). It means that the productivity of.
In this specification, the pressure-sensitive adhesive sheet includes a base material and a pressure-sensitive adhesive layer made of a cured product of the pressure-sensitive adhesive of the present invention.
In this specification, “tape”, “film”, and “sheet” have the same meaning.
In the present specification, the main component refers to a component having the largest blending amount among a plurality of blended components.

  In the present specification, unless otherwise specified, “molecular weight” means number average molecular weight (Mn). “Mn” is the number average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) measurement.

The pressure-sensitive adhesive of the present invention is based on 100 parts by mass of a urethane urea resin (A) that is a reaction product of an isocyanate group-containing urethane prepolymer (a) and an amine compound (b).
More than 3 parts by mass and 20 parts by mass or less of the isocyanate curing agent (B) are included, the urethane urea resin (A) has a molecular weight dispersity of 1.5 to 6, and is preferably used for surface protection.
The pressure-sensitive adhesive for surface protection of the present invention contains an appropriate amount of an isocyanate curing agent (B) with respect to the urethane urea resin (A) having a relatively narrow molecular weight dispersion. Since the surface protective sheet using this surface protective adhesive has an appropriate adhesive force and cohesive force, the flat part is sufficiently adhered to the curved surface part from the beginning, so that it does not easily float or peel off. Can be peeled off (also called re-peeling).
The pressure-sensitive adhesive for surface protection of the present invention can be used for, for example, a liquid crystal display (LCD) having a flat portion or a curved surface portion, a display such as an organic electroluminescence display (ELD), or a touch panel using such a display. In addition, it can be widely used for surface protection of electronic devices such as mobile phones, smart phones, tablet terminals, computers, etc. equipped with such a display or touch panel.
The surface protection is not limited to glass and can be used to protect easily damaged materials such as polyolefin, gold, silver, copper, and ITO.
Further, the surface protection application is not limited to a display, and can be used to protect all surfaces such as window glass, LED, vehicle, wiring and the like. Further, the surface protection can be used for protection during the production process of the member as well as surface protection after the production. In addition, it cannot be overemphasized that the adhesive for surface protection of this invention can be used for purposes other than surface protection.

(Urethane urea resin (A))
The urethane urea resin (A) is a reaction product in which one or more isocyanate group-containing urethane prepolymers and one or more amine compounds are subjected to a urea reaction (a urea bond is formed). The urea reaction can be performed in the presence of a catalyst, if necessary. A solvent can be used in the copolymerization reaction as necessary. The urethane urea resin (A) can be used alone or in combination of two or more.

<Isocyanate group-containing urethane prepolymer (a)>
The isocyanate group-containing urethane prepolymer (a) is preferably a compound synthesized by subjecting polyisocyanate (x) and polyol (y) to a urethane reaction (a urethane bond is formed). The polyisocyanate (x) is preferably a bifunctional isocyanate (x1) having two isocyanate groups in one molecule. The polyol (y) is preferably a bifunctional polyol (y1) having two hydroxyl groups in one molecule. The isocyanate group of the polyisocyanate (x) is used in a molar ratio so as to be in excess of the hydroxyl group of the polyol (y).
In the urethane reaction, it is preferable to use a catalyst for promoting the reaction.

<Polyisocyanate (x)>
As the polyisocyanate compound (x), for example, known compounds such as aromatic polyisocyanate, aliphatic polyisocyanate, araliphatic polyisocyanate, and alicyclic polyisocyanate can be used.

  Aromatic polyisocyanates include, for example, 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 etc. are mentioned.

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

  Examples of the araliphatic polyisocyanate include ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene, Examples include 1,4-tetramethylxylylene diisocyanate and 1,3-tetramethylxylylene diisocyanate.

  Examples of the alicyclic polyisocyanate include 3-isocyanate methyl-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 (isocyanatemethyl) cyclohexane, 1,4-bis (isocyanatemethyl) cyclohexane and the like It is done.

  The polyisocyanate is a diisocyanate, but a triisocyanate obtained by modifying the diisocyanate can also be used. Examples of the triisocyanate include trimethylolpropane adducts, burettes, and trimers of the diisocyanate (this trimer includes an isocyanurate ring).

  The polyisocyanate (x) is preferably 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), or the like.

  Polyisocyanate (x) can be used alone or in combination of two or more.

<Polyol (y)>
The polyol (y) is a compound having two or more hydroxyl groups. The polyol (y) is preferably a known compound such as polyether polyol, polyester polyol, and polycarbonate polyol.
The polyol (y) used in the present invention is preferably composed mainly of a polyol having two hydroxyl groups in order to realize an appropriate cohesive force and adhesive force of the adhesive layer. Moreover, when using together the polyol which has 3 or more of hydroxyl groups, it is preferable to use it with less mass than the polyol which has 2 hydroxyl groups.

  Examples of the polyether polyol include a reaction product obtained by addition polymerization of one or more oxirane compounds using an active hydrogen-containing compound having two or more active hydrogens in one molecule as an initiator.

The active hydrogen-containing compound is preferably a hydroxyl group-containing compound or an amine.
Examples of the hydroxyl group-containing compound include bifunctional active hydrogen-containing compounds such as ethylene glycol (EG), propylene glycol (PG), 1,4-butanediol, neopentyl glycol, and butylethylpentanediol; 3 such as glycerin and trimethylolpropane. Functional active hydrogen-containing compounds; tetrafunctional active hydrogen-containing compounds such as pentaerythritol.
The amine is, for example, a bifunctional active hydrogen-containing compound such as N-aminoethylethanolamine, isophoronediamine, and xylylenediamine; a trifunctional active hydrogen-containing compound such as triethanolamine; a tetrafunctional activity such as ethylenediamine and aromatic diamine. Hydrogen-containing compounds; pentafunctional active hydrogen-containing compounds such as diethylenetriamine.

  Examples of the oxirane compound include alkylene oxide (AO) such as ethylene oxide (EO), propylene oxide (PO), and butylene oxide (BO); tetrahydrofuran (THF) and the like.

  The polyether polyol preferably has an alkyleneoxy group derived from the active hydrogen-containing compound in the molecule (this polyol is also referred to as “polyoxyalkylene polyol”). The polyalkylene polyol is preferably a bifunctional polyether polyol such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and particularly preferably polypropylene glycol having low crystallinity and giving flexibility. Since the bifunctional polyether polyol has a two-dimensional crosslinkability, appropriate adhesive force and cohesive force can be obtained in the adhesive layer.

  The number average molecular weight (Mn) of the polyether polyol is not particularly limited, and is preferably 200 to 6,000, more preferably 400 to 4,000, and more preferably 600 to 4 because transparency and flexibility are effectively expressed. Is more preferred. By making Mn 200 or more, it is easy to control the reaction during synthesis of the isocyanate group-containing urethane prepolymer. Moreover, it is easy to adjust the cohesion force to a urethane urea resin to an appropriate range by making Mn 6,000 or less.

  The polyester polyol is, for example, a compound (esterified product) obtained by esterifying one or more polyol components and one or more acid components, or a compound synthesized by ring-opening polymerization of a lactone (ring-opening polymer). preferable.

  Examples of the lactone include polycaprolactone, poly (β-methyl-γ-valerolactone), and polyvalerolactone.

  Examples of the polyol component include ethylene glycol (EG), propylene glycol (PG), 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, 2-ethyl-1,3- Hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, glycerin, trimethylolpropane, pentaerythritol, and hexanetriol Etc.

  Examples of the acid component include succinic acid, methyl succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, dimer acid, 2-methyl-1, 4-cyclohexanedicarboxylic acid, 2-ethyl-1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, and 4,4′-biphenyldicarboxylic acid Examples thereof include acids and acid anhydrides thereof.

  The number average molecular weight (Mn) of the polyester polyol is preferably from 200 to 8,000, more preferably from 500 to 6,000, further preferably from 500 to 4,000, particularly preferably from 500 to 3,000. By making Mn 200 or more, it is easy to control the reaction during synthesis of the isocyanate group-containing urethane prepolymer. Moreover, it is easy to adjust the cohesive force of urethane urea resin to an appropriate range by setting Mn to 8,000 or less.

Examples of other polyols other than the above include polycarbonate polyols, butadiene-based polyols, and castor oil polyols. Other polyols are preferably used in combination with polyether polyols or polyester polyols.
The number average molecular weight (Mn) of other polyols is about 200 to 8,000.

  Polyol (y) is preferably a polyether polyol.

  In addition, when polyol (y) contains acidic functional groups, such as a carboxyl group and a sulfo group, an adherend may be corroded. Therefore, when applying the surface-protective pressure-sensitive adhesive of the present application that makes an adherend that easily corrodes, it is preferable to use a polyol having no acidic functional group.

  The polyol (y) can be used alone or in combination of two or more.

<Catalyst>
As the catalyst, for example, a tertiary amine compound and an organometallic compound are preferable.

Examples of the tertiary amine compound include triethylamine, triethylenediamine, and 1,8-diazabicyclo (5,4,0) -undecene-7 (DBU).
The organometallic compound is preferably a tin compound or a non-tin compound.
Examples of the tin compound include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin Examples include acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, and tin 2-ethylhexanoate.
Non-tin compounds are, for example, titanium compounds such as dibutyltitanium dichloride, tetrabutyltitanate, and butoxytitanium trichloride; lead oleate, lead 2-ethylhexanoate, lead benzoate, lead naphthenate, etc. Lead compounds; iron compounds such as iron 2-ethylhexanoate and iron acetylacetonate; cobalt compounds such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc such as zinc naphthenate and zinc 2-ethylhexanoate Zirconium compounds such as zirconium compounds such as zirconium naphthenate.

  The catalyst can be used alone or in combination of two or more.

  The catalyst is preferably used in an amount of 0.01 to 1.0 part by mass with respect to 100 parts by mass in total of the polyisocyanate (x) and the polyol (y).

  When a plurality of polyols (y) are used in the synthesis of the isocyanate group-containing urethane prepolymer (a) and the respective reactivity is different, the reaction control fails when one type of catalyst is used, and the synthesis proceeds with each polyol alone. The reaction solution may become cloudy. In this case, when two types of catalysts are used, the reaction (for example, reaction rate or the like) can be easily controlled, and the above problem can be solved. That is, in this invention, when using several polyol (y), it is preferable to use 2 or more types of catalysts. The combination of the two types of catalysts is not particularly limited, and examples thereof include tertiary amine / organometallic, tin / non-tin, and tin / tin. Among these, tin-based / tin-based are preferable, and dibutyltin dilaurate and tin 2-ethylhexanoate are more preferable.

  The mass ratio of tin 2-ethylhexanoate and dibutyltin dilaurate (tin 2-ethylhexanoate / dibutyltin dilaurate) is not particularly limited, preferably more than 0 and less than 1, more preferably 0.2 to 0.6. is there. When the mass ratio is used within an appropriate range, the reaction control becomes easy.

<Solvent>
In synthesizing the isocyanate group-containing urethane prepolymer (a), one or more solvents can be used as necessary. Examples of the solvent include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone. Among these, ethyl acetate, toluene and the like are preferable from the viewpoint of the solubility of the isocyanate group-containing urethane prepolymer (a) and the boiling point of the solvent.

<Polymerization method>
The polymerization method of the isocyanate group-containing urethane prepolymer (a) is not particularly limited, and known polymerization methods such as a bulk polymerization method and a solution polymerization method can be used.
The polymerization procedure is, for example,
Procedure 1) Procedure for charging one or more polyisocyanates (x), one or more polyols (y), one or more catalysts as required, and one or more solvents as needed into a flask in a lump. ;
Procedure 2) One or more polyols (y), one or more catalysts as required, and one or more solvents as needed are charged into a flask, and one or more polyisocyanates (x) are added dropwise thereto. The procedure of adding is mentioned.
Among these, the low molecular component in the raw material is preferentially reacted, the molecular weight dispersity is narrowed, and the reaction control is easy, so that the procedure 2) is preferable.

When using a catalyst, the reaction temperature is preferably less than 100 ° C, more preferably 85 to 95 ° C. When the reaction temperature is less than 100 ° C., side reactions other than the urethane reaction can be suppressed, so that a desired resin can be easily obtained.
When no catalyst is used, the reaction temperature is preferably 100 ° C or higher, more preferably 110 ° C or higher.

  The time for the urethane reaction often takes about one hour or more when a catalyst is used. When no catalyst is used, it often takes about 3 hours or more.

  When synthesizing the isocyanate group-containing urethane prepolymer (a), the isocyanate group (NCO) of the polyisocyanate (x) and the hydroxyl group (OH) of the polyol (y) are 1.1 to 1.1 in terms of the NCO / OH molar ratio. 2 is preferable, 1.1 to 1.8 is more preferable, and 1.2 to 1.6 is more preferable. Since the urethane prepolymer having an appropriate molecular chain can be formed when the NCO / OH ratio is in an appropriate range, wettability and productivity are further improved.

<Amine compound (b)>
The urethane urea resin (A) is a reaction product obtained by urea reaction of one or more isocyanate group-containing urethane prepolymers (a) and one or more amine compounds (b).
The amine compound (b) is preferably a monoamine, a diamine, or a trifunctional or higher amine, more preferably a diamine or a trifunctional or higher amine, more preferably a diamine having a hydroxyl group or a trifunctional or higher amine, and two or more amino groups. Or a compound having one or more amino groups and one or more hydroxyl groups is particularly preferred. By using the amine compound (b), the cohesive force can be improved by the urea bond regardless of the molecular weight of the urethane urea resin (A). In particular, when the urethane urea resin (A) has a primary hydroxyl group, since the reaction rate is fast, the time until the completion of curing is short, and the productivity is further improved.

  The amine compound (b) includes, for example, ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, triethylenetetramine, diethylenetriamine, triaminopropane, 2,2,4-trimethylhexamethylenediamine, 2- Hydroxyethylethylenediamine, diethanolamine, diisopropanolamine, 1-methylamino-2,3-propanediol, N- (2-hydroxyethyl) propylenediamine, N- (3-hydroxypropyl) ethylenediamine, (2-hydroxyethylpropylene) Diamine, (di-2-hydroxyethylethylene) diamine, (di-2-hydroxyethylpropylene) diamine, (2-hydroxypropylethylene) diamine, (di- Aliphatic amine compounds such as -hydroxypropylethylene) diamine and piperazine; Cycloaliphatic amine compounds such as isophorone diamine and dicyclohexylmethane-4,4'-diamine; phenylenediamine, xylylenediamine, 2,4-tolylenediamine, Aromatic diamines such as 2,6-tolylenediamine, diethyltoluenediamine, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 4,4′-bis- (sec-butyl) diphenylmethane; and dimer acid Examples thereof include dimer diamine obtained by converting a carboxyl group into an amino group; a dendrimer having a primary or secondary amino group at the terminal.

In addition, as the amine compound (b), polyoxyalkylene glycol diamine having propoxyamine at both ends of the molecule and represented by the following general formula [2] can be used.
General formula [2]:
H ₂ N—CH ₂ —CH ₂ —CH ₂ —O— (C _m H _2m —O) _n —CH ₂ —CH ₂ —CH ₂ —NH ₂
(In the formula, m represents an arbitrary integer of 2 to 4, and n represents an arbitrary integer of 2 to 50.)

Among these amine compounds (b), compounds having two or more secondary amino groups and one primary hydroxyl group are preferred from the viewpoint of controlling the urea reaction. As the compound, known compounds can be used without limitation.
An example of a method for synthesizing a compound having two or more secondary amino groups and one primary hydroxyl group will be described. The compound having two or more primary amino groups has at least one hydroxyl group and (meth) acryloyl group. A compound obtained by Michael addition reaction of an individual compound is preferable. The hydroxyl group of the compound is preferably a primary hydroxyl group. As a result, the time until the curing of the urethane urea resin and the isocyanate curing agent is completed is short, and the coating speed can be increased, so that productivity is further improved.

  Examples of the compound having two or more primary amino groups include the compounds exemplified for the amine compound (b). Among these, isophoronediamine, 2,2,4-trimethylhexamethylenediamine, and hexamethylenediamine are preferable because the Michael addition reaction can be easily controlled.

  The polymerization method of the urethane urea resin (A) is not particularly limited, and a known polymerization method can be applied. From the viewpoint of reaction control of the urea reaction, a catalyst is used when synthesizing the isocyanate group-containing urethane prepolymer (a). The catalyst is preferably deactivated. For the inactivation, for example, acetylacetone may be added.

  The polymerization procedure of the urethane urea resin (A) is carried out by charging an isocyanate group-containing urethane prepolymer (a) and, if necessary, one or more solvents into a flask, and adding the amine compound (b) to the flask at a relatively low temperature. The procedure of dripping over is preferable. Thereby, low molecular components are preferentially reacted and the molecular weight dispersity can be narrowed, so that various aptitudes to the curved surface portion are further improved.

Moreover, an unreacted isocyanate group can be lose | disappeared by making a reaction terminator react after making an amine compound (b) react with an isocyanate group containing urethane prepolymer (a). Thereby, the temporal stability of the main ingredient of the pressure-sensitive adhesive before blending of the isocyanate curing agent (B) is further improved. In addition, a main ingredient means the composition remove | excluding the hardening | curing agent from the adhesive.
The reaction terminator is preferably a monoamine. Moreover, it is preferable that a monoamine has a hydroxyl group used as a crosslinking point with an isocyanate hardening | curing agent (B).
Examples of the monoamine include 2-amino-2-methyl-1-propanol.

  The reaction terminator can be used alone or in combination of two or more.

  The weight average molecular weight (Mw) of the urethane urea resin (A) is preferably from 30,000 to 250,000, more preferably from 30,000 to 200,000, and even more preferably from 50,000 to 200,000. When the weight average molecular weight (Mw) is within the above range, various suitability for the curved surface portion is further improved.

  1.5-6 are preferable, as for the molecular weight dispersion degree of a urethane urea resin (A), 2-5 are more preferable, and 2.5-4 are more preferable. When the molecular weight dispersity is less than 1.5, the difficulty of synthesis is high. Moreover, since a low molecular weight component can be suppressed by making molecular weight dispersion | distribution degree 6 or less, various suitability to a curved-surface part improves more.

(Isocyanate curing agent (B))
The isocyanate curing agent (B) is a known compound having a plurality of isocyanate groups. The isocyanate curing agent (B) is preferably the polyisocyanate (x) already described. Among them, aromatic polyisocyanates, aliphatic polyisocyanates, araliphatic polyisocyanates, and alicyclic polyisocyanates, and trimethylolpropane thereof. Adduct bodies, these burette bodies, and trifunctional isocyanates such as these trimers are more preferred.

  The isocyanate curing agent (B) can be used alone or in combination of two or more.

  The compounding amount of the isocyanate curing agent (B) is more than 3 parts by mass and preferably 20 parts by mass or less, more preferably 5 to 15 parts by mass with respect to 100 parts by mass of the urethane urea resin (A). When an appropriate amount of the isocyanate curing agent (B) is blended, appropriate adhesive strength and cohesive strength are easily obtained.

(Plasticizer (C))
The pressure-sensitive adhesive for surface protection of the present invention can further contain a plasticizer (C). When the plasticizer (C) is contained, the wettability of the adhesive layer to the adherend is further improved. The plasticizer (C) is preferably a fatty acid ester or phosphate ester having 8 to 30 carbon atoms from the viewpoint of compatibility with other components.

  The fatty acid ester having 8 to 30 carbon atoms is, for example, an ester of a monobasic acid or polybasic acid having 6 to 18 carbon atoms and a branched alcohol having 18 or less carbon atoms, an unsaturated fatty acid having 14 to 18 carbon atoms or a branched acid. Examples include esters with tetravalent or lower alcohols, esters of monobasic acids or polybasic acids with 6 to 18 carbon atoms and polyalkylene glycols, and fatty acid esters obtained by epoxidizing unsaturated sites with peroxides.

  Esters of monobasic acids or polybasic acids having 6 to 18 carbon atoms and branched alcohols having 18 or less carbon atoms include, for example, isostearyl laurate, isopropyl myristate, isocetyl myristate, octyldodecyl myristate, isostearyl palmitate , Isocetyl stearate, octyldodecyl oleate, diisostearyl adipate, diisocetyl sebacate, trioleyl trimellitic acid, triisocetyl trimellitic acid, and the like.

  Examples of the unsaturated fatty acid or branched acid having 14 to 18 carbon atoms include myristoleic acid, oleic acid, linoleic acid, linolenic acid, isopalmitic acid, and isostearic acid. Examples of the tetravalent or lower alcohol include ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, and sorbitan.

  Examples of the ester of monobasic acid or polybasic acid having 6 to 18 carbon atoms and polyalkylene glycol include polyethylene glycol dihexylate, polyethylene glycol di-2-ethylhexylate, polyethylene glycol dilaurate, polyethylene glycol dioleate, and adipic acid Examples include dipolyethylene glycol methyl ether.

  Fatty acid esters obtained by epoxidizing unsaturated sites with peroxides, for example, epoxidized epoxidized fats and oils such as epoxidized soybean oil, epoxidized linseed oil, and epoxidized cottonseed oil, and unsaturated fatty acids having 8 to 18 carbon atoms Examples thereof include ester compounds of a compound and a linear or branched alcohol having 1 to 6 carbon atoms.

  Examples of the phosphoric acid ester include phosphoric acid or an ester compound of phosphoric acid and a linear or branched alcohol having 2 to 18 carbon atoms.

  The plasticizer (C) can be used alone or in combination of two or more.

  The number average molecular weight (Mn) of the plasticizer (C) is preferably 300 to 1000, more preferably 300 to 900, and still more preferably 350 to 850, from the viewpoint of improving the wetting rate.

  0.1-100 mass parts is preferable with respect to 100 mass parts of urethane urea resins (A), and, as for the compounding quantity of a plasticizer (C), 1-80 mass parts is more preferable, and 10-50 mass parts is more preferable. When an appropriate amount of the plasticizer (C) is blended, the wettability is further improved.

(Antioxidant (D))
The pressure-sensitive adhesive for surface protection of the present invention can further contain an antioxidant (D). If the antioxidant (D) is contained, thermal deterioration of the urethane urea resin (A) can be suppressed.
The antioxidant is preferably a radical chain inhibitor such as a phenol-based antioxidant and an amine-based antioxidant, and a sulfur-based antioxidant or a phosphorus-based antioxidant.

Examples of phenolic 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 and other monophenolic antioxidants;
2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 4,4′-thiobis (3-methyl-6-t) -Butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), and 3,9-bis [1,1-dimethyl-2- [β- (3-tert-butyl-4-hydroxy) Bisphenol antioxidants such as -5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro [5,5] undecane;
1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-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, and 1,3,5-tris (3 ', 5'-di-t-butyl-4'-hydroxybenzyl) -S-triazine- Examples thereof include polymeric phenolic antioxidants such as 2,4,6- (1H, 3H, 5H) trione and tocophenol.

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

  Examples of the phosphorus antioxidant include triphenyl phosphite, diphenylisodecyl phosphite, and phenyl diisodecyl phosphite.

  The antioxidant (D) can be used alone or in combination of two or more.

  0.01-10 mass parts is preferable with respect to 100 mass parts of urethane urea resins (A), and, as for the compounding quantity of antioxidant (D), 0.1-5 mass parts is more preferable.

(Antistatic agent (E))
The pressure-sensitive adhesive for surface protection of the present invention can further contain an antistatic agent (E). When the antistatic agent (E) is contained, electrostatic discharge when the pressure-sensitive adhesive sheet is peeled off is suppressed, and for example, damage to components incorporated in a display or the like is easily prevented.
Examples of the antistatic agent include inorganic salts, polyhydric alcohol compounds, ionic liquids, surfactants, and the like. Among these, an ionic liquid is preferable. The “ionic liquid” is also called a room temperature molten salt, and exhibits liquid properties at 25 ° C.

  Inorganic salts include, for example, sodium chloride, potassium chloride, lithium chloride, lithium perchlorate, ammonium chloride, potassium chlorate, aluminum chloride, copper chloride, ferrous chloride, ferric chloride, ammonium sulfate, potassium nitrate, sodium nitrate, Examples thereof include sodium carbonate and sodium thiocyanate.

  Examples of the polyhydric alcohol compound include propanediol, butanediol, hexanediol, polyethylene glycol, trimethylolpropane, and pentaerythritol.

  The ionic liquid is a salt of a cation and an anion, and the cation is preferably, for example, an imidazolium ion, a pyridinium ion, or an ammonium ion.

  Ionic liquids containing imidazolium ions include, for example, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide, and 1-butyl- Examples include 3-methylimidazolium bis (trifluoromethylsulfonyl) imide.

  Examples of ionic liquids containing pyridinium ions include 1-methylpyridinium bis (trifluoromethylsulfonyl) imide, 1-butylpyridinium bis (trifluoromethylsulfonyl) imide, 1-hexylpyridinium bis (trifluoromethylsulfonyl) imide, -Octylpyridinium bis (trifluoromethylsulfonyl) imide, 1-hexyl-4-methylpyridinium bis (trifluoromethylsulfonyl) imide, 1-hexyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methyl Pyridinium bis (trifluoromethylsulfonyl) imide, 1-octyl-4-methylpyridinium bis (fluorosulfonyl) imide, 1-methylpyridinium bis (perfluoroethylsulfonyl) imi , And 1-methyl-pyridinium bis (perfluorobutylsulfonyl) imide, and the like.

  Examples of the ionic liquid containing ammonium ions include trimethylheptylammonium bis (trifluoromethanesulfonyl) imide, N, N-diethyl-N-methyl-N-propylammonium bis (trifluoromethanesulfonyl) imide, N, N-diethyl-N. -Methyl-N-pentylammonium bis (trifluoromethanesulfonyl) imide, N, N-diethyl-N-methyl-N-heptylammonium bis (trifluoromethanesulfonyl) imide, and tri-n-butylmethylammonium bistrifluoromethanesulfonimide Etc.

  In addition, known ionic liquids whose cations are pyrrolidinium salts, phosphonium salts, sulfonium salts, and the like can be used as appropriate.

  Surfactants can be classified into nonionic, anionic, cationic, and amphoteric types.

Nonionic types include, for example, glycerin fatty acid ester, polyoxyalkylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamine fatty acid ester, fatty acid diethanolamide, polyetheresteramide type , Ethylene oxide-epichlorohydrin type, and polyether ester type.
Examples of the anionic type include alkyl sulfonate, alkyl benzene sulfonate, alkyl phosphate, and polystyrene sulfonate type.
Examples of the cationic type include tetraalkylammonium salts, trialkylbenzylammonium salts, and quaternary ammonium base-containing acrylate polymer types.
Amphoteric types include, for example, alkylbetaines and alkylimidazolium betaines, amino acid-type amphoteric surfactants such as higher alkylaminopropionates, betaine-type amphoteric surfactants such as higher alkyldimethylbetaines, and higher alkyldihydroxyethylbetaines. Is mentioned.

  The antistatic agent (E) can be used alone or in combination of two or more.

  0.01-10 mass parts is preferable with respect to 100 mass parts of urethane urea resins (A), and, as for the compounding quantity of an antistatic agent (E), 0.03-5 mass parts is more preferable.

(solvent)
The surface-protective pressure-sensitive adhesive of the present invention can contain a solvent, if necessary. Examples of the solvent include known compounds such as methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone. Among these, ethyl acetate and toluene are preferable from the viewpoint of compatibility with the urethane urea resin (A) and the boiling point of the solvent.

  The solvent can be used alone or in combination of two or more.

(Optional component)
The surface-protective pressure-sensitive adhesive of the present invention can contain an optional component as necessary as long as it is within a range that can solve the problem. Optional components include resins other than urethane resins, fillers, metal powders, pigments, foils, softeners, UV absorbers, light stabilizers, surface lubricants, leveling agents, corrosion inhibitors, heat stabilizers , Polymerization inhibitors, antifoaming agents, lubricants and the like.

  Examples of the filler include talc, calcium carbonate, titanium oxide and the like.

  Examples of the UV absorber include benzophenone UV absorbers, benzotriazole UV absorbers, salicylic acid UV absorbers, oxalic anilide UV absorbers, cyanoacrylate UV absorbers, and triazine UV absorbers. It is done.

  Examples of the benzophenone ultraviolet absorber include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2′- Dihydroxy-4-dimethoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, and bis (2-methoxy-4-hydroxy-5-benzoylphenyl) ) Methane and the like.

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

  Examples of the salicylic acid ultraviolet absorber include phenyl salicylate, p-tert-butylphenyl salicylate, and p-octylphenyl salicylate.

  Examples of the cyanoacrylate ultraviolet absorber include 2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate and ethyl-2-cyano-3,3'-diphenyl acrylate.

  Examples of the light stabilizer include a hindered amine light stabilizer and an ultraviolet light stabilizer.

  Examples of the hindered amine light stabilizer 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-piperidyl sebacate and the like.

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

  Examples of the leveling agent include an acrylic leveling agent, a fluorine leveling agent, and a silicon leveling agent. A commercially available leveling agent includes acrylic leveling agents such as Polyflow No. 36, Polyflow No. 56, Polyflow No. 85HF, Polyflow No. 99C (Isure is also Kyoeisha Chemical Co., Ltd.). Examples of the fluorine leveling agent include Megafac F470N and Megafac F556 (both manufactured by DIC). Examples of the silicon leveling agent include Grandic PC4100 (manufactured by DIC).

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention includes a base material and a pressure-sensitive adhesive layer that is a cured product of the surface-protecting pressure-sensitive adhesive. The adhesive layer can be formed on one side or both sides of the substrate. The surface of the adhesive layer that is not in contact with the base material is usually protected with a release sheet until just before use in order to prevent the adhesion of foreign substances.

As the base material, a flexible sheet and plate material can be used without limitation. Examples of the substrate include plastic, paper, metal foil, and a laminate thereof.
In order to improve adhesion, the surface of the substrate that contacts the adhesive layer can be subjected in advance to an easy adhesion process such as a dry process such as a corona discharge process or a wet process such as application of an anchor coat agent.

  Examples of the base plastic include ester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); olefin resins such as polyethylene (PE), polypropylene (PP) and cycloolefin polymer (COP); Vinyl resins such as vinyl; amide resins such as nylon 66; urethane resins (including foams); and the like.

The thickness of a base material is about 10-300 micrometers normally except a polyurethane sheet. Moreover, the thickness in the case of using a polyurethane sheet (a foam is included) for a base material is about 20-50,000 micrometers normally.
Examples of the paper include plain paper, coated paper, and art paper.
Examples of the metal foil include aluminum foil and copper foil.

  As the release sheet, a known release sheet in which a known release treatment such as a silicone-based release agent is performed on the surface of plastic or paper can be used.

  Examples of the method for producing a pressure-sensitive adhesive sheet include a method in which a pressure-sensitive adhesive is applied to the surface of a substrate to form a coating layer, and then the coating layer is dried and cured to form a pressure-sensitive adhesive layer. The heating and drying temperature is usually about 60 to 150 ° C. The thickness of the pressure-sensitive adhesive layer is usually about 0.1 to 200 μm.

  Examples of the coating method include known methods such as a roll coater method, a comma coater method, a die coater method, a reverse coater method, a silk screen method, and a gravure coater method.

  In contrast to the above method, a pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive to the surface of the release sheet to form a coating layer, and then drying and curing the coating layer. Is formed, and finally the substrate is bonded to the exposed surface of the adhesive layer. When a release sheet is bonded in place of the substrate by the above method, a cast adhesive sheet of release sheet / adhesive layer / release sheet is obtained.

  Hereinafter, embodiments of the present invention will be described with reference to Examples. In addition, it cannot be overemphasized that the embodiment of this invention is not limited to an Example. Hereinafter, “part” means “part by mass”, and “%” means “% by mass”.

[Measurement of weight average molecular weight (Mw) and number average molecular weight (Mn)]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured by gel permeation chromatography (GPC) method. The measurement conditions are as follows. Mw and Mn are both polystyrene equivalent values.
<Measurement conditions>
Apparatus: SHIMADZU Prominence (manufactured by Shimadzu Corporation),
Column: Three SHODEX LF-804 (Showa Denko) are connected in series.
Detector: differential refractive index detector,
Solvent: tetrahydrofuran (THF),
Flow rate: 0.5 mL / min,
Solvent temperature: 40 ° C.
Sample concentration: 0.1%
Sample injection volume: 100 μL.

[material]
The materials used are as follows.
<Polyisocyanate (x)>
(X1): HDI (hexamethylene diisocyanate, “Desmodur H” manufactured by Sumika Covestrourethane Co., Ltd.),
(X2): IPDI (isophorone diisocyanate, “Desmodur I” manufactured by Sumika Covestrourethane Co., Ltd.),
(X3): XDI (xylylene diisocyanate, “Takenate 500” manufactured by Mitsui Chemicals, Inc.).

<Polyol (y)>
(Y1): PPG600 (“SANNICS PP-600”, polyoxypropylene glycol, Mn600, hydroxyl number 2, Sanyo Chemical Industries, Ltd.)
(Y2): PPG1000 (“Sanix PP-1000”, polyoxypropylene glycol, Mn1000, hydroxyl number 2, Sanyo Chemical Industries, Ltd.)
(Y3): PPG2000 (“Sanix PP-2000”, polyoxypropylene glycol, Mn2000, hydroxyl number 2, Sanyo Chemical Industries, Ltd.),
(Y4): PPG 4000 (“Sanix PP-4000”, polyoxypropylene glycol, Mn 4000, hydroxyl number 2, manufactured by Sanyo Chemical Industries, Ltd.)
(Y5): PX1000 ("Prime ball PX-1000", terminal primary modified polyoxypropylene glycol, Mn1000, number of hydroxyl groups 2, manufactured by Sanyo Chemical Industries)
(Y6): P1010 ("Kuraray polyol P-1010", polyester polyol, Mn1000, number of hydroxyl groups 2, manufactured by Kuraray Co., Ltd.)
(Y7): GI1000 (“NISSO-PB GI-1000”, hydroxylated hydrogenated polybutadiene at both ends, Mn1000, number of hydroxyl groups 2, manufactured by Nippon Soda Co., Ltd.)
(Y8): C1090 ("Kuraray polyol C-1090", polycarbonate polyol, Mn1000, hydroxyl number 2, manufactured by Kuraray Co., Ltd.)
(Y9): AM302 ("Adeka polyether AM-302", glycerin PO / EO polyol, Mn3000, hydroxyl number 3, manufactured by ADEKA)
(Y10): T-500 ("Polyhardener T-500", polyoxypropylene glyceryl ether, Mn5000, hydroxyl number 3, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
(Y11): D-660 ("Hi-Lube D-660", polypropylene glycol, Mn 3000, hydroxyl number 2, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.),
(Y12): BPEF (“Bisphenoxyethanol fluorene”, 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene, formula weight 438.5, hydroxyl number 2, manufactured by JFE Chemical Co., Ltd.)

<Synthesis of amine compound (b)>
(B1): 25.0 parts of isophoronediamine (IPDA) and 25.0 parts of toluene were charged into a four-necked flask equipped with a stirrer, a reflux condenser, a nitrogen inlet pipe, a thermometer, and a dropping funnel. A mixture of 21.1 parts of 4-hydroxybutyl acrylate and 18.8 parts of butyl acrylate was dropped from the dropping funnel at room temperature. After completion of the dropwise addition, the internal temperature was gradually raised to 80 ° C. and reacted for 2 hours while maintaining 80 ° C., then 39.9 parts of toluene was added, and two secondary amino groups and two primary hydroxyl groups were added. A compound (1) solution having one was obtained.

(B2): 40.0 parts of isophoronediamine (IPDA) and 40.0 parts of toluene were charged into a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel. 67.7 parts of 4-hydroxybutyl acrylate was added dropwise at room temperature from a dropping funnel. After completion of the dropwise addition, the internal temperature was gradually raised to 80 ° C. and reacted at 80 ° C. for 2 hours while maintaining 80 ° C., then 67.7 parts of toluene was added, and two secondary amino groups were added. A compound (2) solution having two secondary hydroxyl groups was obtained.

(B3): HPEA; N- (3-hydroxypropyl) ethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.)
(B4): DEA; diethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.)
(B5): DIPA; diisopropanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.)
(B6): MAPD; 1-methylamino-2,3-propanediol (manufactured by Daicel)
(B7): AMP; 2-amino-2-methyl-1-propanol (manufactured by Dow Chemical Company)

<Isocyanate curing agent (B)>
(B1): HDI adduct (“Sumijour HT”, trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by Sumika Covestro Urethane Co., Ltd.)
(B2): HDI nurate (“Sumijour N3300”, nurate of hexamethylene diisocyanate, manufactured by Sumika Covestro Urethane Co., Ltd.)
(B3): HDI biuret (“Sumijour N3200”, hexamethylene diisocyanate burette body, manufactured by Sumika Covestro Urethane Co., Ltd.)

<Plasticizer (C)>
(C1): M182A (“Unistar M182A”, methyl oleate, manufactured by NOF Corporation)
(C2): W262 ("Monocizer W262", ether ester plasticizer, manufactured by DIC Corporation)
(C3): E-6000 ("Sansosizer E-6000", epoxidized fatty acid 2-ethylhexyl, manufactured by Shin Nippon Rika Co., Ltd.)
(C4): TOP (“TOP”, tris (2-ethylhexyl) phosphate, manufactured by Daihachi Industrial Chemical Co., Ltd.)

(D1): Irg1010 ("Irganox 1010", pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], manufactured by BASF)

<Antistatic agent (E)>
(E1): FSI-ammonium salt (tri-n-butylmethylammonium bistrifluoromethanesulfonimide)
(E2): FSI-lithium salt (lithium bistrifluoromethanesulfonimide)

[Synthesis example of polyurethane urea resin (A)]
(Synthesis Example 1)
In a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, Sanix PPG600 (bifunctional polypropylene glycol, Sanyo Chemical Industries, Ltd.) 628 parts, isophorone diisocyanate 372 parts, toluene 250 parts, As a catalyst, 0.1 part of dioctyltin dilaurate was charged, the temperature was gradually raised to 100 ° C., and the reaction was performed for 2 hours. After cooling to 25 ° C. and adding 750 parts of ethyl acetate and 3 parts of acetylacetone, 65220 parts of Compound (1) was added dropwise over 2 hours, and the reaction was continued for 1 hour while maintaining 25 ° C. After confirming the remaining amount of isocyanate groups by titration, 23 parts of 2-amino-2-methyl-propanol was added to confirm that the NCO characteristic absorption (2,270 cm- ¹ ) of the IR chart had disappeared and the reaction was carried out. finished. The urethane urea resin (A-1) had a weight average molecular weight Mw of 143,000 and a molecular weight dispersity of 5.8.

  Table 1 shows the types of raw materials used, the mixing ratio thereof, and the Mw and molecular weight dispersity of the obtained polyurethane urea resin (A1). In addition, the compounding quantity of the raw material in a table | surface is non-volatile content conversion, and a unit is [part].

(Synthesis Examples 2 to 16)
Resins of Synthesis Examples 2 to 16 were obtained in the same manner as in Synthesis Example 1 except that the materials and blending ratios of Example 1 were changed as shown in Table 1.

(Synthesis Example 17)
A 4-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel was charged with 40 parts of P1010 and 160 parts of AM302. To this, 200 parts of toluene, 0.03 part of dibutyltin dilaurate and 0.01 part of tin 2-ethylhexanoate were added as catalysts, and the temperature was gradually raised to 90 ° C. What mixed 13 parts of HDI and 13 parts of toluene was dripped over 1 hour, and reaction was performed after dripping for 1 hour. Sampling was performed at any time, and the disappearance of the remaining isocyanate group was confirmed by infrared absorption (IR) spectrum, and then the reaction solution was cooled to complete the reaction. The urethane resin had a weight average molecular weight Mw of 141,000 and a molecular weight dispersity of 6.1.

(Synthesis Example 18)
In a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, 799 parts Sanix PPG1000 (bifunctional polypropylene glycol, Sanyo Chemical Industries), 146 parts hexamethylene diisocyanate, 250 parts toluene Then, 0.1 part of dioctyltin dilaurate was charged as a catalyst, the temperature was gradually raised to 100 ° C., and the reaction was performed for 2 hours. After cooling to 70 ° C. and adding 750 parts of toluene and 3 parts of acetylacetone, 27 parts of compound (1) were added dropwise over 30 minutes, and the reaction was continued for 1 hour while maintaining 70 ° C. After confirming the remaining isocyanate group by titration, add 0.8 part of 2-amino-2-methyl-propanol and confirm that the NCO characteristic absorption (2,270 cm- ¹ ) of the IR chart has disappeared. The reaction was terminated. The urethane urea resin (A-19) had a weight average molecular weight Mw of 230,000 and a molecular weight dispersity of 6.9.

Example 1
100 parts of the polyurethane urea resin (A1) obtained in Synthesis Example 1, 3.5 parts of the isocyanate curing agent (B1), 0.5 part of the antioxidant (D1), and 100 parts of ethyl acetate as a solvent were blended together. To obtain a pressure-sensitive adhesive. In addition, the usage-amount of each material except a solvent shows a non-volatile content conversion value.

Polyethylene terephthalate (PET) (“Lumirror T-60”, manufactured by Toray Industries, Inc.) having a thickness of 25 μm was prepared as a substrate. Using a comma coater (registered trademark), the obtained pressure-sensitive adhesive was applied onto the substrate at a coating speed of 3 m / min so that the thickness after drying was 12 μm.
Next, the formed coating layer was dried using a drying oven at 100 ° C. for 2 minutes to form an adhesive layer. A commercially available release sheet having a thickness of 38 μm was bonded onto the adhesive layer, and the adhesive sheet was obtained by curing for 1 week under the condition of 23 ° C.-50% RH.

(Examples 2-36, Comparative Examples 1-4)
Except having changed the material and compounding ratio of Example 1 as shown in Table 2, it carried out similarly to Example 1, and obtained the adhesive and adhesive sheet of Examples 2-36 and Comparative Examples 1-4, respectively. .
However, Examples 34, 35 and 36 are reference examples.

[Evaluation items and methods]
Evaluation items and evaluation methods of the obtained pressure-sensitive adhesive and pressure-sensitive adhesive sheet are as follows.

(Removability)
The obtained pressure-sensitive adhesive sheet was prepared in a size of 25 mm in width and 100 mm in length, and used as a measurement sample. Subsequently, in an atmosphere of 23 ° C.-50% RH, the release sheet was peeled from the measurement sample, the exposed adhesive layer was attached to a caustic soda glass plate, and a 2 kg roll was reciprocated once for pressure bonding. Then, it was left for 24 hours under 60 ° C.-90% RH condition. Next, after air-cooling in an atmosphere of 23 ° C.-50% RH for 30 minutes, in accordance with JISZ0237, using a tensile tester (Tensilon: manufactured by Orientec Co., Ltd.) under conditions of a peeling speed of 300 mm / min and a peeling angle of 180 ° The adhesive strength was measured. In addition, the one where adhesive strength is low is easy to peel again. The evaluation criteria are as follows.
A: Less than 200 mN / 25 mm. Excellent.
A: 200 mN / 25 mm or more and less than 500 mN / 25 mm. Good.
Δ: 500 mN / 25 mm or more and 1000 mN / 25 mm. Can be used practically.
X: More than 1000 mN / 25 mm. Not practical.

(Wettability)
The obtained adhesive tape was prepared to have a width of 50 mm and a length of 100 mm, and used as a measurement sample. Subsequently, after leaving for 30 minutes in 23 degreeC-50% RH atmosphere, the peeling sheet was peeled from the measurement sample. The center part of the exposed adhesive layer was brought into contact with the glass plate while holding both ends of the adhesive tape with both hands, and then both hands were released. The wettability of the pressure-sensitive adhesive was evaluated by measuring the time until the entire pressure-sensitive adhesive layer adhered to the glass plate by its own weight. Since the wettability (affinity) with respect to glass is so favorable that time until it adhere | attaches with a glass plate, glass can be favorably protected in the manufacturing process using glass. The evaluation criteria are as follows.
A: Less than 3 seconds until adhesion. Excellent.
○: 3 seconds or more and less than 5 seconds until adhesion. Good.
Δ: 5 seconds or more and less than 8 seconds until adhesion. Can be used practically.
X: 8 seconds or more until adhesion. Not practical.

(Adaptability of curved surface part)
The obtained adhesive tape was prepared to have a width of 25 mm and a length of 40 mm, and used as a measurement sample. Next, the release liner was peeled off in an atmosphere of 23 ° C. and 50% RH, and an adhesive tape sample was attached to the exposed adhesive layer along the circumference of a polypropylene cylinder (diameter 30 mm). Three days later, the degree of adhesion of the measurement sample to the cylinder was visually observed. The evaluation criteria are as follows. (Double-circle): There is no floating in the edge part of a measurement sample. Excellent.
○: The edge of the measurement sample floated 1 mm or less. Good.
(Triangle | delta): The edge part of the measurement sample floated exceeding 1 mm and 3 mm or less. Can be used practically.
X: The edge part of the measurement sample floated exceeding 3 mm. Not practical.

(productivity)
Except having changed the coating speed of Example 1 into 30 m / min, it carried out similarly to the Example and produced the adhesive sheet, and evaluated the sclerosis | hardenability in high-speed coating. Evaluation was made by touching the adhesive layer after completion of the drying step with a finger and evaluating the degree of curing with a sticky feeling.
A: Almost no stickiness. Excellent.
○: Although it is slightly sticky, it does not collapse even if the coating film is pushed in with a finger. Good.
Δ: Although it is sticky, it feels slightly moving when the coating film is pushed in with a finger. Can be used practically.
X: Stickiness is intense, and the coating film collapses when touched. Not practical.

  From the description of the synthesis examples, an urethane compound having a narrow molecular weight dispersity could be synthesized by gradually increasing the reaction solution after adding the amine compound dropwise over a relatively low temperature over time. The surface-protective pressure-sensitive adhesive of the present application using this urethane urea resin has wettability and removability from the results in Tables 2 and 3, and was able to produce a pressure-sensitive adhesive sheet with good suitability for curved surfaces and high productivity. .

Claims (7)

Including 100 parts by mass of urethane urea resin (A) which is a reaction product of the isocyanate group-containing urethane prepolymer (a) and amine compound (b), the isocyanate curing agent (B) is contained in an amount exceeding 3 parts by mass and not more than 20 parts by mass. ,
The isocyanate group-containing urethane prepolymer (a) is a compound synthesized by urethane reaction of polyisocyanate (x) and polyol (y),
The polyol (y) includes a polyether polyol,
The amine compound (b) is a trifunctional or higher functional compound having two or more amino groups and 1 to 2 hydroxyl groups, or a trifunctional or higher functional compound having one amino group and two hydroxyl groups. A compound,
The urethane urea resin (A) has a molecular weight dispersity of 1.5 to 6 and a primary hydroxyl group,
The adhesive strength after 24 hours at 60 ° C.-90% RH is 1000 mN / 25 mm or less.
Surface protective adhesive.   The pressure-sensitive adhesive for surface protection according to claim 1, wherein the urethane urea resin (A) has a weight average molecular weight of 30,000 to 250,000.   Furthermore, the adhesive for surface protection of Claim 1 or 2 containing a plasticizer (C).   The pressure-sensitive adhesive for surface protection according to any one of claims 1 to 3, comprising 0.1 to 100 parts by mass of the plasticizer (C) with respect to 100 parts by mass of the urethane urea resin (A).   Furthermore, the adhesive for surface protection of any one of Claims 1-4 containing antioxidant (D).   Furthermore, the adhesive for surface protection of any one of Claims 1-5 containing an antistatic agent (E). The adhesive sheet provided with the adhesion layer which is a hardened | cured material of the base material and the adhesive agent for surface protection of any one of Claims 1-6.