JP2019014813A - Adhesive and adhesive sheet - Google Patents

Abstract

To provide an adhesive that can form an adhesive layer that has excellent wettability, re-peelability, and low temperature stability, and does not impair an electric resistance value of a conductive film as an adherend.SOLUTION: An adhesive has a polyurethane resin (A), an isocyanate curing agent (B), and an ester (C) that is a reactant between a polyol (c1) and a monobasic acid. The ester (C) has two or more ester bonds, and a linking group that links the ester bonds together, and the linking group has a branched structure.SELECTED DRAWING: None

Description

  The present invention relates to an adhesive.

  Conventionally, pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer formed on a substrate have been widely used as surface protective sheets for various members. The pressure-sensitive adhesive used for forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet has various types such as acrylic, urethane, and silicone, and the urethane pressure-sensitive adhesive has good wettability with respect to the adherend, for example. Re-peelability. Therefore, pressure-sensitive adhesive sheets using urethane pressure-sensitive adhesives are widely used for surface protection applications such as ITO (indium tin oxide) films and glass in production lines such as touch panels.

  Flat panel displays such as liquid crystal displays (LCDs) and organic electroluminescence displays (OLEDs), and touch panel displays that combine such flat panel displays and touch panels include televisions (TVs), personal computers (PCs), mobile phones, and Widely used in electronic devices such as portable information terminals. The surface protection sheet is used for protecting these surfaces. The surface protection sheet is also used for protecting in-vehicle display devices such as a car navigation system (hereinafter referred to as car navigation system) for in-vehicle use.

  As a urethane pressure-sensitive adhesive, Patent Document 1 discloses one or more esters selected from the group consisting of polyurethane resins, polyisocyanate crosslinking agents, ester compounds having an epoxy group, diisononyl adipate and bis (2-ethylhexyl) adipate. A pressure-sensitive adhesive containing is disclosed.

  Patent Document 2 discloses a pressure-sensitive adhesive containing a polyurethane resin, a polyisocyanate crosslinking agent, and a carboxylic acid ester.

International Publication No. 2015/098270 JP, 2015-151429, A

  However, since the ester compound used in the pressure-sensitive adhesives of Patent Documents 1 and 2 has a linear molecular chain between two ester bonds, it is easy to gather together due to the affinity of linear chains having close polarities. Among them, ester compounds tend to form large clusters. Therefore, for example, when a surface protection sheet is used for in-vehicle use, the surface of the adherend is made of an ester compound after peeling off the surface protection sheet due to the occurrence of bleeding due to the enlargement of the ester compound cluster in winter or in cold regions. When the display is viewed through the surface protective sheet, there is a problem that the low-temperature aptitude is inferior, such as a problem in which an appearance defect such as haze or a stain occurs due to the cluster.

  An object of this invention is to provide the adhesive which can suppress the contamination to a to-be-adhered body, and can form the adhesive sheet with favorable low temperature suitability, and an adhesive sheet.

The pressure-sensitive adhesive of the present invention includes a polyurethane resin (A), an isocyanate curing agent (B), and an ester (C) that is a reaction product of a polyol (c1) and a monobasic acid,
The ester (C) has two or more ester bonds and a linking group that connects the ester bonds, and the linking group has a branched structure.

  According to the said invention, the adhesive which suppresses the contamination to a to-be-adhered body and can form an adhesive sheet with favorable low-temperature aptitude, and an adhesive sheet can be provided.

  First, terms are defined herein. In this specification, a linking group is a molecular chain that connects ester bonds. In this specification, a sheet, a film, and a tape are synonymous. In this specification, the adherend is a counterpart to which the adhesive sheet is bonded.

  In the present specification, unless otherwise specified, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are polystyrene conversion values determined by gel permeation chromatography (GPC) measurement, and are the methods described in “Examples”. Can be measured.

The pressure-sensitive adhesive of the present invention includes a polyurethane resin (A), an isocyanate curing agent (B), and an ester (C) that is a reaction product of a polyol (c1) and a monobasic acid,
The ester (C) has two or more ester bonds and a linking group that connects the ester bonds, and the linking group has a branched structure.
The pressure-sensitive adhesive of the present invention is preferably used as a pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer by forming a pressure-sensitive adhesive layer by coating.
The pressure-sensitive adhesive sheet of the present invention can be used in the form of a tape, a label, a seal, a double-sided tape and the like. The pressure-sensitive adhesive sheet of the present invention can be suitably used as a surface protective sheet, a cosmetic sheet, a non-slip sheet, and the like.

The pressure-sensitive adhesive sheet of the present invention is preferably used for the purpose of protecting the surface of the adherend.
As the adherend, a flat panel display such as a liquid crystal display (LCD) and an organic electroluminescence display (OLED), and a touch panel display in which the flat panel display and the touch panel are combined include a television (TV), a personal computer ( PC), mobile phones, and portable information terminals are preferred. Further, the present invention is not limited to the adherend, and can be used for surface protection of all materials such as windows for buildings, vehicles, ships, and aircraft.

  Among these adherends, the pressure-sensitive adhesive sheet of the present invention includes a flat panel display and a touch panel display (collectively referred to simply as “display”), and a substrate (glass substrate) manufactured or used in these manufacturing processes. And an ITO / glass substrate having an ITO (indium tin oxide) film formed on a glass substrate) and an optical member or the like as a surface protective sheet.

  In the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive of the present invention, the ester (C) has two or more ester bonds and a linking group that connects the ester bonds, and the linking group has a branched structure. including. Since ester (C) has a branched structure between ester bonds, the molecules of ester (C) are less likely to be compatible with each other due to the steric hindrance of the branched structure compared to an ester having no branched structure. Easy to take distance. Therefore, the inventor speculates that the cluster formed by the ester (C) is small and forms a loose aggregate (low density). As a result, when the pressure-sensitive adhesive sheet is used in a low temperature environment, the ester having no branched structure is likely to be incompatible with the polyurethane resin due to enlargement of the cluster, and contamination and poor appearance are likely to occur. However, when the ester (C) is used, the cluster is difficult to enlarge to a level where contamination and poor appearance occur. Thereby, when the pressure-sensitive adhesive of the present invention is used, good low temperature aptitude is obtained.

"Adhesive"
(Polyurethane resin (A))
The polyurethane resin (A) is a reaction product of one or more polyols (x) and one or more polyisocyanates (y) and has a hydroxyl group. One or more polyurethane resins (A) can be used. The copolymerization reaction can be performed in the presence of a catalyst, if necessary. A solvent can be used in the copolymerization reaction as necessary.

<Polyol (x)>
The polyol (x) contains at least one or more trifunctional or higher functional polyols (x2). Preferably, the polyol (x) includes one or more bifunctional polyols (x1) and one or more trifunctional or higher functional polyols (x2).

  The kind of polyol (x) is not particularly limited, and examples thereof include polyester polyol, polyether polyol, polyacryl polyol, polycaprolactone polyol, polycarbonate polyol, and castor oil-based polyol. Of these, polyester polyols, polyether polyols, and combinations thereof are preferred.

  The polyester polyol includes a compound (esterified product) obtained by an esterification reaction of one or more polyol components and one or more acid components.

  The starting polyol component is, for example, 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 hexane And triols.

  The acid component of the raw material is, for example, 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, 4,4′-biphenyl dicarboxylic acid Examples thereof include acids and acid anhydrides thereof.

  As the polyether polyol, a known one can be used, and a compound 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. (Addition polymer).

  Examples of the initiator include a hydroxyl group-containing compound and an amine. Specifically, ethylene glycol (EG), propylene glycol (PG), 1,4-butanediol, neopentyl glycol, butylethylpentanediol, N-aminoethylethanolamine, isophoronediamine, xylylenediamine, and the like 2 Functional initiators; trifunctional initiators such as glycerin, trimethylolpropane, and triethanolamine; tetrafunctional initiators such as pentaerythritol, ethylenediamine, and aromatic diamine; and pentafunctional initiators 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 is preferably an alkylene oxide adduct (also referred to as polyoxyalkylene polyol) of an active hydrogen-containing compound. Among these, bifunctional polyether polyols such as polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetramethylene glycol; trifunctional polyether polyols such as an alkylene oxide adduct of glycerin are preferable.

The number average molecular weight (Mn) of the polyol (x) is not particularly limited, and is preferably 200 to 10,000. When Mn is 200 or more, gelation of the polyurethane resin (A) is effectively suppressed. When Mn is 10,000 or less, the cohesive force of the polyurethane resin (A) is suitable.
When the polyol (x) is selected from polyester polyols and polyether polyols, the preferred number average molecular weight (Mn) is as follows.
The number average molecular weight (Mn) of the polyester polyol is preferably 500 to 5,000, more preferably 600 to 4,000, and particularly preferably 800 to 3,000. When Mn is 500 or more, gelation of the polyurethane resin (A) is effectively suppressed. When Mn is 5,000 or less, the cohesive force of the polyurethane resin (A) is further improved.
The number average molecular weight (Mn) of the polyether polyol is preferably 500 to 5,000, more preferably 600 to 4,000, and particularly preferably 800 to 3,000. When Mn is 500 or more, gelation of the polyurethane resin (A) is effectively suppressed. When Mn is 5,000 or less, the cohesive force of the polyurethane resin (A) is further improved.

As the polyol (x), it is preferable to use one or more trifunctional or higher functional polyols (x2).
Preferably, one or more bifunctional polyols (x1) and one or more trifunctional or higher functional polyols (x2) are used in combination. In general, the bifunctional polyol (x1) has a two-dimensional crosslinkability, and an appropriate flexibility is obtained in the pressure-sensitive adhesive layer. The trifunctional or higher polyol (x2) has a three-dimensional crosslinkability, and Appropriate hardness can be obtained. By using these together, an adhesive layer having suitable cohesive strength and adhesive strength can be obtained.

  The bifunctional polyol (x1) is preferably at least one polyol selected from the group consisting of a bifunctional polyether polyol, a bifunctional polyester polyol, and a bifunctional polycarbonate polyol.

  A tri- or more functional polyether polyol is a glycerin PO adduct (also referred to as “glycerin polypropylene glycol”) obtained by addition polymerization of one or more propylene oxides (PO) to glycerin, or one or more propylene per glycerin. Examples include glycerin PO · EO adducts (also referred to as “glycerin polypropylene glycol-terminated ethylene glycol-modified”) obtained by addition polymerization of oxide (PO) and one or more ethylene oxides (EO) in this order.

  In the present invention, the ratio of the bifunctional polyol (x1) to the trifunctional or higher functional polyol (x2) is not particularly limited, and any ratio can be taken.

<Polyisocyanate (y)>
A well-known thing can be used for the polyisocyanate compound (y), and aromatic polyisocyanate, aliphatic polyisocyanate, araliphatic polyisocyanate, alicyclic polyisocyanate, etc. are mentioned.

  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.

In addition, as the polyisocyanate, an isocyanate prepolymer may be used. The isocyanate prepolymer is obtained by dipolymerizing diisocyanate as a raw material so that the monomer content is 1% or less. Examples of the isocyanate prepolymer include adduct bodies, burette bodies, and isocyanurate bodies.
An adduct is an adduct of diisocyanate and trimethylolpropane (CH ₃ —CH ₂ —C (CH ₂ —OH) ₃ ). The burette body is a reaction product of diisocyanate and water or a tertiary alcohol. The isocyanurate is a diisocyanate trimer (this trimer contains an isocyanurate ring).

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

  In the polymerization of the urethane prepolymer (A), the blending ratio of the polyol (x) and the polyisocyanate (y) is preferably set so that the number of moles of hydroxyl groups exceeds the number of moles of isocyanate groups. The ratio of the number of moles of hydroxyl groups in the polyol (x) to the number of moles of isocyanate groups in the polyisocyanate (y) (NCO / OH ratio) is preferably 0.30 to 0.95, more preferably 0.5 to 0.90. When the hydroxyl group and the isocyanate group are reacted at an appropriate ratio, cohesion and adhesion can be achieved at a high level.

In the present invention, the polyisocyanate (y) contains one or more bifunctional isocyanate compounds (y1).
As the polyisocyanate (y), it is preferable to use only the bifunctional isocyanate compound (y1). As for polyisocyanate (y), polyisocyanate (y) can contain 1 or more types of trifunctional or more than trifunctional isocyanate compounds as needed.
When only a trifunctional or higher functional polyol having high crosslinkability and only a trifunctional or higher polyisocyanate are used as the raw material polyol of the polyurethane resin, the molecular structure of the polyurethane resin becomes rigid and the cohesive force of the adhesive layer becomes higher than the preferred range. There is a fear.
In the pressure-sensitive adhesive of the present invention using a trifunctional or higher functional polyol as a raw material polyol for a polyurethane resin, one or more polyisocyanates containing a bifunctional isocyanate compound (y1) as the polyisocyanate (y), preferably a bifunctional isocyanate compound (y1). ) Only, it is possible to obtain an adhesive layer having suitable cohesive force and adhesive force while suppressing excessive crosslinking.

<Catalyst>
Examples of the catalyst include tertiary amine compounds and organometallic compounds.

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

Examples of organometallic compounds include tin compounds and non-tin compounds.
Examples of tin compounds include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin Examples include acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, dioctyltin dilaurate, tributyltin chloride, tributyltin trichloroacetate, and tin 2-ethylhexanoate.
Non-tin compounds include, for example, titanium series such as dibutyltitanium dichloride, tetrabutyltitanate, and butoxytitanium trichloride; lead series such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; Iron systems such as iron 2-ethylhexanoate and iron acetylacetonate; cobalt systems such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc systems such as zinc naphthenate and zinc 2-ethylhexanoate; zirconium naphthenate Zirconium type

One or more catalysts can be used. When the reactivity of each of the plural kinds of polyols (x) used in combination as required is different, the difference in reactivity may cause gelation or white turbidity of the reaction solution in a single catalyst system. In this case, by using two types of catalysts, it is easy to control the reaction (for example, reaction rate and the like), and the above problem can be solved. A combination of two kinds of catalysts is not particularly limited, and examples thereof include tertiary amine / organometallic, tin / non-tin, and tin / tin. Preferred are tin / tin, more preferably dibutyltin dilaurate and tin 2-ethylhexanoate.
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. If the mass ratio is less than 1, the catalyst activity is well balanced, gelling and clouding of the reaction solution are effectively suppressed, and the polymerization stability is further improved.

  The usage-amount in particular of 1 or more types of catalyst is not restrict | limited, Preferably it is 0.01-1 mass% with respect to the total amount of polyol (x) and polyisocyanate (y).

<Solvent>
A solvent can be used as needed for the synthesis of the polyurethane resin (A). Examples of the solvent include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone. From the viewpoints of the solubility of the polyurethane resin (A) and the boiling point of the solvent, ethyl acetate and toluene are particularly preferable.

<Polymerization method>
The polymerization method of the polyurethane resin (A) is not particularly limited, and known polymerization methods such as a bulk polymerization method and a solution polymerization method can be applied.
The polymerization procedure is not particularly limited,
Procedure 1) Procedure for charging polyol (x), polyisocyanate (y), a catalyst as required, and a solvent as needed into a flask at once;
Procedure 2) A procedure in which polyol (x), a catalyst as necessary, and a solvent as needed are charged into a flask and polyisocyanate (y) is added dropwise thereto.
Procedure 2) is preferred because the reaction is easy to control.

The reaction temperature when using the catalyst is preferably less than 100 ° C, more preferably 80 to 90 ° C. If reaction temperature is less than 100 degreeC, it is easy to control reaction rate, a crosslinked structure, etc., and will produce | generate the polyurethane resin (A) which has a desired molecular weight easily.
When no catalyst is used, the reaction temperature is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, and the reaction time is preferably 3 hours or longer.

  The weight average molecular weight (Mw) of the polyurethane resin (A) is preferably 10,000 to 500,000, more preferably 20,000 to 400,000, and particularly preferably 30,000 to 350,000. Good coatability is easily obtained when the Mw of the polyurethane resin (A) is in an appropriate range.

(Isocyanate curing agent (B))
The isocyanate curing agent (B) is a compound exemplified by the polyisocyanate (y) that is the raw material of the polyurethane resin (A) (specifically, aromatic polyisocyanate, aliphatic polyisocyanate, araliphatic polyisocyanate, alicyclic ring). Group polyisocyanates and their trimethylolpropane adducts / burettes / trimers).

  The amount of the isocyanate curing agent (B) with respect to 100 parts by mass of the polyurethane resin (A) is preferably 1 to 50 parts by mass, more preferably 1 to 20 parts by mass, and particularly preferably 2 to 15 parts by mass. If the amount of the polyfunctional isocyanate (B) is 1 part by mass or more, the cohesive force of the adhesive layer is good, and if it is 50 parts by mass or less, the adhesive force of the adhesive layer is good.

<Ester (C)>
The ester (C) has two or more ester bonds and a linking group that connects the ester bonds, and the linking group is a compound having a branched structure, and is a reaction product of a polyol (c1) and a monobasic acid. is there. The pressure-sensitive adhesive containing the ester (C) has an effect of improving the low temperature suitability in addition to the improvement in removability and wettability. As a reason for this effect, the inventor found that the ester (C) has a lower density of clusters formed by the esters (C) due to the steric hindrance of the branched structure than the ester having no branched structure, or Since the size is small, it is difficult for clusters to increase in a low-temperature environment, and moderate compatibility can be maintained in the adhesive layer. Therefore, it is assumed that the ester (C) is difficult to bleed from the adhesive layer.

  The molecular weight (formula) of the ester (C) is preferably 1000 or less, more preferably 850 or less, further preferably 700 or less, and particularly preferably 600 or less from the viewpoint of further improving the low temperature environment. The lower limit of the molecular weight (formula weight) is not limited as long as it is a compound part having a branched structure and an average of two or more ester bonds. If a lower limit is given, 300 or more is preferable, and 350 or more is more preferable. In the present specification, the molecular weight (formula) is used when the molecular structure of the ester (C) can be specified by a chemical formula. When the ester (C) has a molecular weight distribution instead of a single structure, the number average molecular weight is used.

2-4 are preferable and, as for the number of ester bonds which ester (C) has, 2-3 are more preferable.
The branched structure of the ester (C) means that, for example, a linking group that connects two ester bonds has a branched structure, and can have one or two or more branches. Further, the branched chain of the linking group may have an ester bond such as 2-ethylhexanoic acid triglyceride.

The polyol (c1) preferably has two or more branched structures and hydroxyl groups. The number of hydroxyl groups in the polyol (c1) is not limited as long as it can form two or more ester bonds, but is preferably 4 or less and more preferably 3 or less.
Examples of the polyol (c1) include an aliphatic polyol having a branched structure and an aromatic polyol having a branched structure. Among these, an aliphatic polyol having a branched structure is preferable.

The aliphatic polyol having a branched structure is preferably an alkylene polyol having a branched structure.
Examples of the alkylene polyol include bifunctional polyols and trifunctional or higher polyols. In the present specification, the bifunctional polyol means a polyol having two hydroxyl groups.

Examples of the bifunctional polyol of the alkylene polyol having a branched structure include 1,2-propylene glycol, ethylene-propylene glycol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol, and 1,3-butane. Diol, 3-methyl-1,5-pentanediol, butylethylpentanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 2-methyl-1,8-octanediol, 1 , 8-decanediol.
Examples of the trifunctional or higher functional polyol of the alkylene polyol having a branched structure include glycerin, trimethylolpropane, pentaerythritol and the like.

Examples of the aromatic polyol having a branched structure include bifunctional polyols and polyols of trifunctional polyols or more.
Examples of the bifunctional polyol of the aromatic polyol having a branched structure include bisphenol compounds such as bisphenol A, bisphenol B, and bisphenol C.
Examples of the trifunctional or higher functional polyol of the aromatic polyol having a branched structure include trisphenol compounds such as leucaulin.

  A monobasic acid is a compound having one carboxyl group, and a fatty acid is preferred. 4-24 are preferable, as for carbon number of a fatty acid, 4-18 are more preferable, 6-18 are more preferable, and 6-12 are especially preferable. When the carbon number is 4 or more, the wettability is further improved, and when the carbon number is 24 or less, the low temperature aptitude is further improved.

Fatty acids include, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, ethyl caproate, pelargonic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, stearic acid Oleic acid, linoleic acid, linolenic acid, arachidic acid, arachidonic acid, behenic acid, lignoceric acid, nervonic acid and the like.
Esters (C) can be used alone or in combination of two or more.

  Examples of commercially available esters (C) include Toyo Chemical Industry Co., Ltd., Highsolve MMPOM (propylene glycol dimethyl ether), Highsolve MDPOM (propylene glycol dimethyl ether), Highsolve MTPOM (tripropylene glycol dimethyl ether), etc .; Nisshin Oilio Co., Ltd. Are Saracos PR-85 (di (caprylic / capric acid) propanediol), Saracos PR-17 (diisostearic acid propanediol), Estemol N-01 (dipentyl glycol di-2-ethylhexanoate), T.I. I. O (glyceryl tri-2-ethylhexanoate), O.I. D. O (tri (capryl / capric acid) glyceryl), Saracos 6318V (trimethylolpropane triisostearate), Saracos 5408 (pentaerythrityl tetra-2-ethylhexanoate), Saracos 5418V (pentaerythrityl tetraisostearate), etc .; RIKEN Vitamin Co., Ltd. has after M-1 (medium chain fatty acid triglyceride C8 / C10 = 60/40), after M-2 (medium chain fatty acid triglyceride C8 = 100), after M-4 (medium chain fatty acid triglyceride C8 / C10 = 85/15), Riquemar O-71-D (diglycerin oleate); manufactured by Kao Corporation, Exepearl BP-DL (polyoxyethylene bisphenol A laurate), Exepearl PE-TP (pentaerythritol tetrapalmitate), etc. Be mentioned

  Moreover, it is preferable that ester (C) does not have a hydroxyl group in a coupling group. This is because when the ester (C) has a hydroxyl group, the crosslinking reactivity between the polyurethane resin (A) and the isocyanate curing agent (B) is lowered, and the removability may be lowered.

  The ester (C) is preferably blended in an amount of 0.5 to 80 parts by mass, more preferably 2 to 70 parts by mass, and further preferably 5 to 60 parts by mass with respect to 100 parts by mass of the polyurethane resin (A). 10-55 mass parts is especially preferable, and 15-50 mass parts is the most preferable. When an appropriate amount of the ester (C) is used, in addition to the improvement in removability and wettability, the low temperature suitability is further improved.

(solvent)
The pressure-sensitive adhesive of the present invention can contain a solvent, if necessary. A known compound can be used as the solvent. 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 polyurethane resin (A) and the boiling point of the solvent.

(Anti-alteration agent (D))
The pressure-sensitive adhesive of the present invention may contain one or more alteration preventing agents (D) as necessary. Thereby, the fall of the various characteristics by long-term use of the adhesion layer can be suppressed. Examples of the alteration inhibitor (D) include a hydrolysis resistance agent, an antioxidant, an ultraviolet absorber, and a light stabilizer.

<Hydrolysis-resistant agent>
When a hydrolysis reaction occurs in the adhesive layer in a high temperature and high humidity environment and a carboxy group is generated, a hydrolysis-resistant agent can be used to block the carboxy group.
Examples include a hydrolysis-resistant agent, a carbodiimide type, an isocyanate type, an oxazoline type, and an epoxy type. Among these, a carbodiimide type is preferable from the viewpoint of hydrolysis inhibiting effect.

A carbodiimide-based hydrolysis inhibitor is a compound having one or more carbodiimide groups in one molecule.
Examples of the monocarbodiimide compound include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, diphenylcarbodiimide, and naphthylcarbodiimide.
The polycarbodiimide compound can be produced by decarboxylation condensation reaction of diisocyanate in the presence of a carbodiimidization catalyst. Examples of the diisocyanate include 4,4′-diphenylmethane diisocyanate, 3,3′-dimethoxy-4,4′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, and 4,4′-diphenyl ether diisocyanate. 3,3′-dimethyl-4,4′-diphenyl ether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4 ′ -Dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, etc. are mentioned. Examples of the carbodiimidization catalyst include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 1-ethyl- Examples include 2-phospholene-1-oxide and phospholene oxides such as 3-phospholene isomers.

  Isocyanate-based hydrolysis inhibitors include, for example, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane. Diisocyanate, 2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4 '-Biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate Nate, trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4'- Examples include dicyclohexylmethane diisocyanate and 3,3′-dimethyl-4,4′-dicyclohexylmethane diisocyanate.

  Examples of the oxazoline-based hydrolysis inhibitor include 2,2′-o-phenylenebis (2-oxazoline), 2,2′-m-phenylenebis (2-oxazoline), 2,2′-p-phenylenebis ( 2-oxazoline), 2,2'-p-phenylenebis (4-methyl-2-oxazoline), 2,2'-m-phenylenebis (4-methyl-2-oxazoline), 2,2'-p- Phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′-m-phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′-ethylenebis (2-oxazoline), 2,2'-tetramethylene bis (2-oxazoline), 2,2'-hexamethylene bis (2-oxazoline), 2,2'-octamethylene bis (2-oxazoline), 2,2'-ethylene Bis (4-methyl-2-oxazoline), and 2,2'-diphenylenebis (2-oxazoline).

  Epoxy hydrolyzing agents include, for example, diglycidyl ethers of aliphatic diols such as 1,6-hexanediol, neopentyl glycol, and polyalkylene glycol; sorbitol, sorbitan, polyglycerol, pentaerythritol, diglycerol, glycerol, and Polyglycidyl ethers of aliphatic polyols such as trimethylolpropane; Polyglycidyl ethers of alicyclic polyols such as cyclohexanedimethanol; Fats such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, trimellitic acid, adipic acid, and sebacic acid Diglycidyl or polyglycidyl esters of aromatic or aromatic polycarboxylic acids; resorcinol, bis- (p-hydroxyphenyl) methane, 2,2-bis- (p-hydroxy) Diglycidyl or polyglycidyl ethers of polyhydric phenols such as phenyl) propane, tris- (p-hydroxyphenyl) methane, and 1,1,2,2-tetrakis (p-hydroxyphenyl) ethane; N, N-di N-glycidyl derivatives of amines such as glycidyl aniline, N, N-diglycidyl toluidine, and N, N, N ′, N′-tetraglycidyl-bis- (p-aminophenyl) methane; triglycidyl derivatives of aminofail; Examples include triglycidyl tris (2-hydroxyethyl) isocyanurate and triglycidyl isocyanurate; epoxy resins such as orthocresol type epoxy resin and phenol novolac type epoxy resin.

  The addition amount of the hydrolysis-resistant agent is not particularly limited, and is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 4.5 parts by mass, particularly preferably 100 parts by mass of the polyurethane resin (A). Is 0.5-3 parts by mass.

<Antioxidant>
Examples of the antioxidant include a radical scavenger and a peroxide decomposer. Examples of the radical scavenger include phenolic compounds and amine compounds. Examples of the peroxide decomposing agent include sulfur compounds and phosphorus compounds.

  Examples of the phenol compound include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearin-β- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 4 , 4′-thiobis (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 3,9-bis [1,1-dimethyl-2- [ β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro [5,5] undecane, benzo Zenpropanoic acid, 3,5-bis (1,1-dimethylethyl) -4-hydroxy-, C7-C9 side chain alkyl ester, 1,1,3-tris (2-methyl-4-hydroxy-5-t- 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, 1, 3,5-tris (3 ′, 5′-di-t-butyl-4′-hydroxybenzyl) -S-triazine-2,4,6- (1H, 3H, 5H) trione, tocophenol, etc. It is.

  Phosphorus compounds include, for example, triphenyl phosphite, diphenylisodecyl phosphite, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenylditridecyl) phosphite, cyclic neopentanetetrayl bis (Octadecyl phosphite), tris (nonylphenyl) phosphite, tris (monononylphenyl) phosphite, tris (dinonylphenyl) phosphite, diisodecylpentaerythritol diphosphite, 9,10-dihydro-9-oxa-10 -Phosphaphenanthrene-10-oxide, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10- Decyloxy-9,1 -Dihydro-9-oxa-10-phosphaphenanthrene, tris (2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) phosphite Cyclic neopentanetetraylbis (2,6-di-tert-butyl-4-methylphenyl) phosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite, etc. Can be mentioned.

By using an antioxidant, it is possible to prevent thermal degradation of the polyurethane resin (A) and more effectively suppress bleed out of the ester (C) from the adhesive layer.
The addition amount of the antioxidant is not particularly limited, and is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, and particularly preferably 0.1 to 0.1 parts by mass with respect to 100 parts by mass of the polyurethane resin (A). 2 to 2 parts by mass.

  From the viewpoint of stability and antioxidant effect, the antioxidant is preferably one or more phenolic compounds that are radical scavengers, and includes one or more phenolic compounds that are radical scavengers and a peroxide decomposer. It is more preferable to use one or more phosphorus compounds in combination. Further, it is particularly preferable to use a phenolic compound that is a radical scavenger and a phosphorus compound that is a peroxide decomposing agent in combination as an antioxidant, and to use these antioxidants in combination with the aforementioned hydrolysis-resistant agent. .

<Ultraviolet absorber>
Examples of the ultraviolet absorber include benzophenone compounds, benzotriazole compounds, salicylic acid compounds, oxalic acid anilide compounds, cyanoacrylate compounds, and triazine compounds.
The addition amount of the ultraviolet absorber is not particularly limited, and is preferably 0.01 to 3 parts by mass, more preferably 0.1 to 2.5 parts by mass, particularly preferably 100 parts by mass of the polyurethane resin (A). 0.2 to 2 parts by mass.

<Light stabilizer>
Examples of the light stabilizer include hindered amine compounds and hindered piperidine compounds. The addition amount of the light stabilizer is not particularly limited, and is preferably 0.01 to 2 parts by mass, more preferably 0.1 to 1.5 parts by mass, particularly preferably 100 parts by mass of the polyurethane resin (A). 0.2 to 1 part by mass.

(Antistatic agent (E))
The pressure-sensitive adhesive of the present invention can contain one or more antistatic agents (E) as required.
Examples of the antistatic agent include inorganic salts, polyhydric alcohol compounds, ionic liquids, surfactants, and the like, and among these, ionic liquids are preferable. The “ionic liquid” is also called a room temperature molten salt, and is a salt that has fluidity 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.

  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 ion 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, commercially available ionic liquids such as pyrrolidinium salts, phosphonium salts, and sulfonium salts can be used as appropriate.

  Surfactants are classified into low molecular surfactants and high molecular surfactants. In any type, there are nonionic, anionic, cationic and amphoteric types.

Nonionic low molecular surfactants include glycerin fatty acid esters, polyoxyalkylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, and fatty acid diethanolamides. .
Examples of the anionic low molecular surfactant include alkyl sulfonate, alkyl benzene sulfonate, and alkyl phosphate.
Examples of the cationic low molecular surfactant include tetraalkylammonium salts and trialkylbenzylammonium salts.
Examples of amphoteric low molecular surfactants include alkylbetaines and alkylimidazolium betaines.

Nonionic polymer surfactants include polyether ester amide type, ethylene oxide-epichlorohydrin type, and polyether ester type.
Examples of the anionic polymer surfactant include polystyrene sulfonic acid type.
Examples of the cationic polymer surfactant include a quaternary ammonium base-containing acrylate polymer type.
Examples of the amphoteric polymer surfactant include amino acid-type amphoteric surfactants such as higher alkylaminopropionate, betaine-type amphoteric surfactants such as higher alkyldimethylbetaine, and higher alkyldihydroxyethylbetaine.

  The addition amount of the antistatic agent (E) is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass with respect to 100 parts by mass of the polyurethane resin (A).

(Leveling agent)
The pressure-sensitive adhesive of the present invention can contain a leveling agent as required. By adding a leveling agent, when the adhesive is applied, the surface tension of the coating film is lowered, and an adhesive layer having a smooth surface is easily obtained. Examples of the leveling agent include acrylic leveling agents, fluorine leveling agents, and silicone leveling agents. From the viewpoint of suppressing adherend contamination after re-peeling the pressure-sensitive adhesive sheet, acrylic leveling agents and the like are preferable.

  The weight average molecular weight (Mw) of the leveling agent is not particularly limited, and is preferably 500 to 20,000, more preferably 1,000 to 15,000, and particularly preferably 2,000 to 10,000. When Mw is 500 or more, the amount of vaporization from the coating layer is sufficiently small when the coating layer is heated and dried, and surrounding contamination is suppressed. If Mw is 20,000 or less, the improvement effect of the leveling property of an adhesion layer will express effectively.

  The addition amount of the leveling agent is not particularly limited, and preferably 0.001 with respect to 100 parts by mass of the polyurethane resin (A) from the viewpoint of suppressing contamination of the adherend after re-peeling the adhesive sheet and improving the leveling property of the adhesive layer. To 2 parts by mass, more preferably 0.01 to 1.5 parts by mass, and particularly preferably 0.1 to 1 part by mass.

(Other optional ingredients)
If the adhesive of this invention is a range which can solve the subject of this invention, it can contain another arbitrary component. Other optional components include catalysts, resins other than urethane resins, fillers (talc, calcium carbonate, titanium oxide, etc.), metal powders, colorants (pigments, etc.), foils, softeners, conductive agents , Silane coupling agents, lubricants, corrosion inhibitors, heat stabilizers, weathering stabilizers, polymerization inhibitors, and antifoaming agents.

"Adhesive sheet"
The pressure-sensitive adhesive sheet of the present invention includes a base material and a pressure-sensitive adhesive layer made of a cured product of the pressure-sensitive adhesive of the present invention. The adhesive layer can be formed on one side or both sides of the substrate. If necessary, the exposed surface of the adhesive layer can be covered with a release sheet. The release sheet is peeled off when the pressure-sensitive adhesive sheet is attached to the adherend. The substrate is preferably a sheet.

In FIG. 1, the schematic cross section of the adhesive sheet of 1st Embodiment which concerns on this invention is shown. In FIG. 1, reference numeral 10 is an adhesive sheet, reference numeral 11 is a base material, reference numeral 12 is an adhesive layer, and reference numeral 13 is a release sheet. The pressure-sensitive adhesive sheet 10 is a single-sided pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on one side of a base material.
In FIG. 2, the schematic cross section of the adhesive sheet of 2nd Embodiment which concerns on this invention is shown. In FIG. 2, reference numeral 20 is an adhesive sheet, reference numeral 21 is a base material, reference numerals 22A and 22B are adhesive layers, and reference numerals 23A and 23B are release sheets. The pressure-sensitive adhesive sheet 20 is a double-sided pressure-sensitive adhesive sheet in which pressure-sensitive adhesive layers are formed on both surfaces of a base material.

  A base material in particular is not restrict | limited, A resin sheet, paper, metal foil, etc. are mentioned. The substrate may be a laminated sheet in which any one or more layers are laminated on at least one surface of these substrates. The surface on the side of the base material on which the adhesive layer is formed may be subjected to easy adhesion treatment such as corona discharge treatment and anchor coating agent coating, if necessary.

The constituent resin of the resin sheet is not particularly limited. For example, ester resins such as polyethylene terephthalate (PET); olefin resins such as polyethylene (PE) and polypropylene (PP); vinyl resins such as polyvinyl chloride; nylon 66 and the like Amide resins; urethane resins (including foams); and combinations thereof.
The thickness of the resin sheet excluding the polyurethane sheet is not particularly limited, and is preferably 15 to 300 μm. The thickness of the polyurethane sheet (including foam) is not particularly limited, and is preferably 20 to 50,000 μm.
The paper is not particularly limited, and examples thereof include plain paper, coated paper, and art paper.
The constituent metal of the metal foil is not particularly limited, and examples thereof include aluminum, copper, and combinations thereof.
As described above, since the pressure-sensitive adhesive of the present invention has excellent substrate adhesion, the pressure-sensitive adhesive sheet of the present invention is preferable because it has a high degree of freedom in selecting the substrate to be used.

  The release sheet is not particularly limited, and a known release sheet in which a known release treatment such as application of a release agent is performed on the surface of a resin sheet or paper can be used.

An adhesive sheet can be manufactured by a well-known method.
First, the pressure-sensitive adhesive of the present invention is applied to the surface of a substrate to form a coating layer made of the pressure-sensitive adhesive of the present invention. A known method can be applied as the coating method, and examples thereof include 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.
Next, the coating layer is dried and cured to form an adhesive layer made of a cured product of the adhesive of the present invention. The heat drying temperature is not particularly limited, and is preferably about 60 to 150 ° C.
The thickness of the pressure-sensitive adhesive layer can be appropriately designed depending on the use of the pressure-sensitive adhesive sheet, and is, for example, about 5 to 300 μm. In the present specification, “thickness of the adhesive layer” is a thickness after drying unless otherwise specified.
Next, if necessary, a release sheet is attached to the exposed surface of the adhesive layer by a known method.
A single-sided adhesive sheet can be manufactured as described above.
A double-sided PSA sheet can be produced by performing the above operations on both sides.

  Contrary to the above method, the pressure-sensitive adhesive of the present invention is applied to the surface of the release sheet to form a coating layer made of the pressure-sensitive adhesive of the present invention, and then the coating layer is dried and cured to produce the pressure-sensitive adhesive of the present invention. An adhesive layer made of a cured product of the agent may be formed, and finally a substrate may be laminated on the exposed surface of the adhesive layer.

The pressure-sensitive adhesive sheet of the present invention is preferably used by being attached to the surface of a display device.
Examples of the display device include a television (TV), a personal computer (PC), a mobile phone, a portable information terminal, a display mounted on a vehicle, that is, a CID (Center Information Display), and a car navigation system. In addition, CID means the information display arrange | positioned in the driver's seat front surface of a motor vehicle. Conventionally, it has been installed mainly for car navigation map display, but in recent years it has become a multi-function display that displays a parking assist function and air conditioning operation / fuel consumption information by installing an in-vehicle camera. Suitability is required.

  Examples of the material of the surface (adhered body) to which the adhesive sheet of the display device is attached include glass, an acrylic plate, polycarbonate, and polyolefin.

  The thickness of the adherend is about 10 μm to 5 mm.

  Hereinafter, although the embodiment of the present invention is described, the present invention is not limited to the following embodiment. Unless otherwise specified, “part” means “part by mass” and “%” means “% by mass”. The compounding quantity in a table | surface is a mass part.

[Measurement of molecular weight]
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.
Apparatus: SHIMADZU Prominence (manufactured by Shimadzu Corporation),
Column: Three SHODEX LF-804 (Showa Denko Co., Ltd.) connected in series,
Detector: differential refractive index detector,
Solvent: tetrahydrofuran (THF),
Flow rate: 0.5 mL / min,
Solvent temperature: 40 ° C.
Sample concentration: 0.02%
Sample injection volume: 200 μL.

[material]
The materials used are as follows.
<Bifunctional polyol (x1)>
(X1-1): Kuraray polyol P-1010 (polyester polyol, number average molecular weight Mn1000, hydroxyl number 2, manufactured by Kuraray Co., Ltd.)
(X1-2): Kuraray polyol C-1090 (polycarbonate polyol, number average molecular weight Mn1000, hydroxyl number 2, manufactured by Kuraray Co., Ltd.)
(X1-3): PEG-1000 (polyether polyol, number average molecular weight Mn1000, hydroxyl number 2, manufactured by Toho Chemical Industry Co., Ltd.)

<Trifunctional or higher polyol (x2)>
(X2-1): Sanniks GP-3000 (polyether polyol, number average molecular weight Mn3000, hydroxyl number 3, Sanyo Chemical Industries, Ltd.),
(X2-2): Sanniks GL-3000 (polyether polyol, number average molecular weight Mn3000, hydroxyl number 3, Sanyo Chemical Industries, Ltd.),

<Polyisocyanate (y)>
(Y-1): Desmodur H (hexamethylene diisocyanate, manufactured by Sumika Covestro Urethane Co., Ltd.)
(Y-2): Desmodur I (isophorone diisocyanate, manufactured by Sumika Covestrourethane Co., Ltd.)
(Y-3): Coronate T-65 (tolylene diisocyanate, manufactured by Tosoh Corporation),

<Polyfunctional isocyanate compound (B)>
(B-1): Sumidur HT (trimethylolpropane adduct of hexamethylene diisocyanate, non-volatile content 75%, manufactured by Sumika Covestro Urethane Co., Ltd.)
(B-2): Death module N3200 (a burette of hexamethylene diisocyanate, non-volatile content 100%, manufactured by Sumika Covestro Urethane Co., Ltd.)
(B-3): Death module L75 (trimethylolpropane adduct of tolylene diisocyanate, non-volatile content 75%, manufactured by Sumika Covestro Urethane Co., Ltd.).

<Ester (C)>
(C-1): Estemol N-01 (di-2-ethylhexanoic acid neopentyl glycol), molecular weight 356, monobasic acid carbon number 8, ester bond number 2, linking group is branched structure / aliphatic, Nissin Made by Eulio),
(C-2): T. I. O (glyceryl tri-2-ethylhexanoate, molecular weight 470, carbon number of monobasic acid 8, ester bond number 3, branched structure / aliphatic to linking group, manufactured by Nisshin Oilio Co., Ltd.),
(C-3): Actor M-1 (medium chain fatty acid triglyceride C8 / C10 = 60/40, number average molecular weight 504, average carbon number of monobasic acid 8.8, ester bond number 3, linking group is branched structure. Aliphatic, manufactured by Riken Vitamin Co.,
(C-4): Riquemar O-71-D (diglycerin oleate, molecular weight 620, carbon number 18 of fatty acid, ester bond number 2, linking group is branched structure / aliphatic, Nisshin Oilio Co., Ltd.),
(C-5): Exepearl BP-DL (polyoxyethylene bisphenol A lauric acid ester, molecular weight 678, carbon number of monobasic acid 12, ester bond number 2, linking group is branched structure / aromatic, manufactured by Kao Corporation),
(C'-1): Sansosizer DINA (diisononyl adipate, ester molecular weight 398 of dibasic acid and monoalcohol, number of ester bonds 2, linking group is linear structure / aliphatic, manufactured by Shin Nippon Rika Co., Ltd.)
(C′-2): TOTM (trimellitic acid tris (2-ethylhexyl), ester of tribasic acid and monoalcohol, molecular weight 547, ester bond number 3, linking group is branched structure / aromatic, manufactured by Mitsubishi Chemical Corporation) ,
(C′-3): Sansosizer E-6000 (epoxidized fatty acid 2-ethylhexyl, molecular weight about 400, ester bond number 1, linking group is a straight chain structure / aliphatic, manufactured by Shin Nippon Rika Co., Ltd.).

<Anti-alteration agent (D)>
(D-1): IRGANOX 1010 (manufactured by BASF), hindered phenol antioxidant.

<Antistatic agent (E)>
(E-1): Ionic liquid, tri-n-butylmethylammonium bistrifluoromethanesulfonimide.

(Synthesis Example 1)
In a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel, 25 parts of bifunctional polyol (x1-1), 75 parts of trifunctional polyol (x2-1), and bifunctional 7.4 parts of polyisocyanate (y-1) (amount in which NCO / OH is 0.7) was charged. To this, 72 parts of toluene, 0.03 part of dibutyltin dilaurate and 0.01 part of tin 2-ethylhexanoate were added as catalysts, the temperature was gradually raised to 90 ° C., and the reaction was carried out at 90 ° C. for 2 hours. 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. As described above, a solution (nonvolatile content: 60%) of the polyurethane resin (A-1) was obtained. Mw of the obtained polyurethane resin (A-1) was 226,000. Table 1-1 shows the blending composition and Mw of the obtained polyurethane resin (A-1).
In addition, the calculation method of the part amount of bifunctional polyisocyanate (y-1) is as follows.
(Part of (y-1)) [part] =
(NCO / OH ratio) × (molecular weight of (y−1)) / (number of NCO groups of (y−1)) ×
[(Partial amount of (x1-1)) / (Molecular weight of (x1-1)) × (Number of hydroxyl groups of (x1-1))
+ (Part of (x2-1)) / (molecular weight of (x2-1)) × (number of hydroxyl groups of (x2-1))]]
= 0.7 × 168/2 × (2/1000 × 2 + 98/10000 × 3)
≒ 7.4 parts

(Synthesis Examples 2 to 8)
Synthesis Examples 2 to 8 were obtained in the same manner as in Synthesis Example 1 except that the composition was changed to the formulation shown in Table 1-1 to obtain solutions of polyurethane resins (A-2) to (A-8). In each synthesis example, Mw of the obtained polyurethane resin is shown in Table 1.

Example 1
With respect to 100 parts of the polyurethane resin (A-1) in the polyurethane resin (A-1) solution obtained in Synthesis Example 1, 10 parts of the isocyanate compound (B-1) and an antioxidant (non-volatile ratio) 1.0 part of D-1) was blended, 100 parts of ethyl acetate was blended as a solvent, and stirred with a disper to obtain a urethane-based pressure-sensitive adhesive.
A 50 μm-thick polyethylene terephthalate film (PET film, Lumirror T-60: manufactured by Toray Industries, Inc.) was prepared as a base material. The pressure-sensitive adhesive obtained was applied to one side of the substrate so that the thickness of the pressure-sensitive adhesive layer after drying was 12 μm, and dried at 100 ° C. for 2 minutes to form a pressure-sensitive adhesive layer. On this adhesive layer, a 38 μm-thick release sheet (Super Stick SP-PET38: manufactured by Lintec Corporation) was attached to obtain an adhesive sheet. After curing at 23 ° C.-50% RH for 1 week, it was subjected to various evaluations.

(Examples 2 to 22, Comparative Examples 1 to 3)
In each of Examples 2 to 22 and Comparative Examples 1 to 3, a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that the composition was changed as shown in Tables 2 to 5. It was.

[Evaluation items and methods]
Evaluation items and evaluation methods 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. Next, the release sheet was peeled from the measurement sample in an atmosphere of 23 ° C.-50% RH, the exposed adhesive layer was attached to a caustic soda glass plate, and pressure-bonded using a 2 kg roll. Then, it was left for 72 hours under 60 ° C.-90% RH condition. Air-cooled in an atmosphere of 23 ° C.-50% RH for 30 minutes, and then adhered in accordance with JISZ0237 using a tensile tester (Tensilon: manufactured by Orientec Co., Ltd.) at a peeling speed of 300 mm / min and a peeling angle of 180 °. The force 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 50 mN / 25 mm, good.
Δ: 50 mN / 25 mm or more and 200 mN / 25 mm, practical use is possible.
X: Over 200 mN / 25 mm, impractical.

(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.
○: Less than 3 seconds until adhesion, good.
Δ: 3 seconds or more and less than 5 seconds until adhesion, practical use possible.
X: 5 seconds or more until contact, impractical.

(Resistance value stability)
The obtained pressure-sensitive adhesive sheet was prepared to have a width of 40 mm and a width of 100 mm. Next, the peelable film was peeled off in a 23 ° C.-50% RH atmosphere, and a PET film having a width of 40 mm and a length of 160 mm on which a 5 μm thick ITO transparent conductive film was formed was bonded and fixed. A test piece having a laminated structure of PET film / adhesive layer / ITO film was obtained by holding a pressure of 5 MPa for 20 minutes. Electrodes were connected to both ends of the test piece, and the initial electrical resistance value was measured [Laresta-GP MCP-T600, manufactured by Mitsubishi Chemical Corporation]. Furthermore, after leaving the test piece to stand at 60 ° C.-90% RH for 72 hours, the electrical resistance value after aging was measured in the same manner as described above, and the resistance value stability was measured as the rate of change in electrical resistance (the electrical resistance value after aging / initial value). Electrical resistance value). The evaluation criteria are as follows. A: Electric resistance change rate is less than 1.2, excellent.
○: The rate of change in electrical resistance is 1.2 or more and less than 1.5, which is good.
(Triangle | delta): Electric resistance change rate is 1.5 or more and less than 2, and is practical.
X: The rate of change in electrical resistance is 2 or more, impractical.

(Low temperature stability)
The obtained pressure-sensitive adhesive sheet was prepared in a size of 70 mm in width and 100 mm in length, and used as a measurement sample. Next, the release sheet was peeled from this measurement sample in an atmosphere of 23 ° C.-50% RH, and the exposed adhesive layer was attached to a caustic soda glass plate. Then, it was left to stand at −15 ° C. for 2 weeks. After air cooling in an atmosphere of 23 ° C.-50% RH for 3 hours, the measurement sample is peeled from the glass plate, and the LED lamp is placed under a fluorescent lamp or in a dark room with respect to the place where the measurement sample is adhered to the glass surface. Light was irradiated and the bleed condition of the wetting agent was visually evaluated. The evaluation criteria are as follows.
○: No change is observed on the glass surface.
Δ: Slight oil stain-like change is observed in the dark on the glass surface.
X: A rainbow-colored pattern is visually observed on the glass surface under a fluorescent lamp, impractical.

[Evaluation results]
The evaluation results are shown in Tables 2 to 5.

  Examples 1-22 from the results of Tables 2 to 5 include polyurethane resin (A), isocyanate curing agent (B), and ester (C) that is a reaction product of polyol (c1) and a monobasic acid, The ester (C) produced a pressure-sensitive adhesive which is a compound having two or more ester bonds and a linking group having a branched structure.

  The pressure-sensitive adhesive sheets obtained in Examples 1 to 22 all have re-peelability after storage at 60 ° C.-90% RH, wettability to glass, and 60 ° C.-90% when used for transparent conductive films. Evaluation results of resistance value stability after storage under RH conditions and low temperature stability after storage under −15 ° C. conditions were good.

  When using an adhesive sheet for the surface protection use of a transparent conductive film, for example, if the adhesive layer contains an acid component, the resistance value may deteriorate. Therefore, by using the ester (C) starting from polyol as a linking group, it was possible to suppress the inclusion of unreacted acid components as impurities and to maintain the resistance value of the transparent conductive film.

  In Comparative Example 1, a pressure-sensitive adhesive was produced using an ester (C ′) having a central structure as a linking group. The pressure-sensitive adhesive sheet obtained in Comparative Example 1 had poor resistance value stability after storage under conditions of 60 ° C.-90% RH and low-temperature stability after storage under conditions of −15 ° C. It was.

  In Comparative Example 2, a pressure-sensitive adhesive was produced using an aromatic ester (C ′). The pressure-sensitive adhesive sheet obtained in Comparative Example 2 had poor resistance value stability after storage at 60 ° C.-90% RH and low-temperature stability evaluation results after storage at −15 ° C. It was.

In Comparative Example 3, a pressure-sensitive adhesive was produced using an ester (C ′) having an ester bond number of 1. The pressure-sensitive adhesive sheet obtained in Comparative Example 3 had poor evaluation results for removability after storage at 60 ° C.-90% RH and low-temperature stability after storage at −15 ° C. .

Claims (8)

Polyurethane ester (A), isocyanate curing agent (B), and ester (C) which is a reaction product of polyol (c1) and a monobasic acid,
The ester (C) has two or more ester bonds and a linking group that connects the ester bonds, and the linking group has a branched structure.   The pressure-sensitive adhesive according to claim 1, comprising 0.5 to 80 parts by mass of the ester (C) with respect to 100 parts by mass of the polyurethane resin (A).   The pressure-sensitive adhesive according to claim 1 or 2, wherein the monobasic acid is a fatty acid.   The pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the polyol (c1) is an aliphatic polyol having a branched structure.   The pressure-sensitive adhesive according to any one of claims 1 to 4, comprising 1 to 30 parts by mass of the isocyanate curing agent (B) with respect to 100 parts by mass of the polyurethane resin.   The pressure-sensitive adhesive according to any one of claims 3 to 5, wherein the fatty acid has 4 to 24 carbon atoms.   The pressure-sensitive adhesive according to any one of claims 1 to 6, wherein the ester (C) has a molecular weight of 300 to 800.   The adhesive sheet provided with the adhesive layer which is a base material and the hardened | cured material of the adhesive of any one of Claims 1-7.