JP6922488B2 - Adhesives and adhesive sheets - Google Patents

Description

The present invention relates to adhesives.

Conventionally, an adhesive sheet having an adhesive layer formed on a base material has been widely used as a surface protective sheet for various members. There are various types of pressure-sensitive adhesives used for forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, such as acrylic type, urethane type, and silicone type. Has excellent removability. Therefore, adhesive sheets using urethane 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), as well as 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 mobile information terminals. Surface protection sheets are used to protect these surfaces. The surface protection sheet is also used for in-vehicle use to protect an in-vehicle display device such as a car navigation system (hereinafter referred to as a car navigation system).

As the urethane pressure-sensitive adhesive, Patent Document 1 describes one or more esters selected from the group consisting of polyurethane resins, polyisocyanate cross-linking agents, ester compounds having an epoxy group, diisononyl adipate and bis (2-ethylhexyl) adipate. Adhesives containing the above are disclosed.

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

International Publication No. 2015/098270 Japanese Unexamined Patent Publication No. 2015-151429

However, since the ester compounds used in the pressure-sensitive adhesives of Patent Documents 1 and 2 have a straight-chain molecular chain between the two ester bonds, they tend to gather together due to the affinity between the straight-chains having similar polarities, and the pressure-sensitive adhesive layer. Among them, the ester compound tends to form a large cluster. Therefore, for example, when the surface protective sheet is used for automobiles, in winter or in cold regions, the surface of the adherend is made of the ester compound after the surface protective sheet is peeled off due to the occurrence of bleeding due to the enlargement of the ester compound clusters. There was a problem of inferior low temperature suitability such as a problem of contamination and a problem of poor appearance such as haze or stain due to the cluster when the display was viewed through the surface protective sheet.

An object of the present invention is to provide a pressure-sensitive adhesive capable of suppressing contamination of an adherend and forming a pressure-sensitive adhesive sheet having good low-temperature suitability, and a pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive of the present invention contains a polyurethane resin (A), an isocyanate curing agent (B), and an ester (C) which 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 to each other, and the linking group has a branched structure.

According to the present invention, it is possible to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet that can suppress contamination of an adherend and form a pressure-sensitive adhesive sheet having good low-temperature suitability.

First, terms are defined herein. As used herein, a linking group is a molecular chain that connects ester bonds to each other. Sheets, films and tapes are synonymous herein. In the present specification, the adherend is the other party to which the adhesive sheet is attached.

In the present specification, unless otherwise specified, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are polystyrene-equivalent values obtained by gel permeation chromatography (GPC) measurement, and are the methods described in "Examples". Can be measured with.

The pressure-sensitive adhesive of the present invention contains a polyurethane resin (A), an isocyanate curing agent (B), and an ester (C) which 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 to each other, and the linking group has a branched structure.
The pressure-sensitive adhesive of the present invention preferably forms a pressure-sensitive adhesive layer by coating and is used as a base material and a pressure-sensitive adhesive sheet provided with the pressure-sensitive adhesive layer.
The pressure-sensitive adhesive sheet of the present invention can be used in the form of tapes, labels, stickers, double-sided tapes and the like. The 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 a touch panel are combined are used as a television (TV) or a personal computer. Electronic devices such as PCs), mobile phones, and mobile information terminals are preferred. Further, it can be used not only for the adherend but also for surface protection of all materials such as windows of buildings, vehicles, ships, and windows of aircraft.

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

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 connecting the ester bonds to each other, and the linking group is an ester (C) having a branched structure. including. Since the ester (C) has a branched structure between the ester bonds, the molecules of the ester (C) are less likely to have an affinity with each other due to steric hindrance of the branched structure as compared with an ester having no branched structure. Easy to take a distance. Therefore, the inventor speculates that the clusters formed by the ester (C) are small and form loose aggregates (low density). As a result, when the pressure-sensitive adhesive sheet is used in a low-temperature environment, the ester having no branched structure tends to have enlarged clusters and become incompatible with the polyurethane resin, which tends to cause contamination and poor appearance. However, with the ester (C), the clusters are less likely to grow to levels that cause contamination and poor appearance. As a result, good low temperature suitability can be obtained by using the pressure-sensitive adhesive of the present invention.

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

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

The type of the polyol (x) is not particularly limited, and examples thereof include polyester polyols, polyether polyols, polyacrylic polyols, polycaprolactone polyols, polycarbonate polyols, and castor oil-based polyols. Among these, polyester polyols, polyether polyols, and combinations thereof are preferable.

Examples of the polyester polyol include compounds (esterified products) obtained by an esterification reaction between one or more polyol components and one or more acid components.

The polyol component of the raw material 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 Triol and the like can be mentioned.

The acid components of the raw material are, for example, succinic acid, methylsuccinic acid, adipic acid, piceric 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'-biphenyldicarboxylic acid Examples thereof include acids and their acid anhydrides.

As the polyether polyol, known ones can be used, and a compound obtained by addition polymerization of one or more kinds of oxylan compounds using an active hydrogen-containing compound having two or more active hydrogens in one molecule as an initiator. (Additional polymer) can be mentioned.

Examples of the initiator include hydroxyl group-containing compounds and amines. Specifically, 2 such as ethylene glycol (EG), propylene glycol (PG), 1,4-butanediol, neopentyl glycol, butylethylpentanediol, N-aminoethylethanolamine, isophoronediamine, and xylylenediamine. Functional initiators; trifunctional initiators such as glycerin, trimethylolpropane, and triethanolamine; tetrafunctional initiators such as pentaerythritol, ethylenediamine, and aromatic diamines; pentafunctional initiators such as diethylenetriamine and the like.

Examples of the oxylan compound include alkylene oxides (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 a polyoxyalkylene polyol) of an active hydrogen-containing compound. Of these, bifunctional polyether polyols such as polyethylene glycol (PEG), polypropylene glycol (PPG), and polytetramethylene glycol; trifunctional polyether polyols such as alkylene oxide adducts of glycerin, and the like 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) becomes suitable.
When selected from polyester polyol and polyether polyol as the polyol (x), 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 polyols (x2).
Preferably, one or more bifunctional polyols (x1) and one or more trifunctional or higher polyols (x2) are used in combination. In general, a bifunctional polyol (x1) has a two-dimensional crosslinkability, and an appropriate flexibility is obtained in the adhesive layer, and a trifunctional or higher functional polyol (x2) has a three-dimensional crosslinkability, and the adhesive layer has an appropriate flexibility. Appropriate hardness can be obtained. By using these in combination, an adhesive layer having suitable cohesive force and adhesive force can be obtained.

The bifunctional polyol (x1) is preferably one or more polyols selected from the group consisting of bifunctional polyether polyols, bifunctional polyester polyols and bifunctional polycarbonate polyols.

The trifunctional or higher functional polyether polyol is a glycerin PO adduct (also referred to as "glycerin polypropylene glycol") obtained by addition-polymerizing one or more propylene oxides (PO) to glycerin, or one or more propylene to glycerin. Examples thereof include a glycerin PO / EO adduct (also referred to as “glycerin polypropylene glycol-terminated ethylene glycol modification”) obtained by addition-polymerizing an 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 can be any ratio.

<Polyisocyanate (y)>
Known polyisocyanate compounds (y) can be used, and examples thereof include aromatic polyisocyanates, aliphatic polyisocyanates, aromatic aliphatic polyisocyanates, and alicyclic polyisocyanates.

The aromatic polyisocyanate is, for example, 1,3-phenylenediocyanate, 4,4'-diphenyldiisocyanate, 1,4-phenylenediocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6- Tolylene diisocyanate, 4,4'-toluene diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, and 4,4', Examples thereof include 4 "-triphenylmethane triisocyanate.

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 thereof include 2,4,4-trimethylhexamethylene diisocyanate.

The aromatic aliphatic polyisocyanate is, for example, ω, ω'-diisocyanate-1,3-dimethylbenzene, ω, ω'-diisocyanate-1,4-dimethylbenzene, ω, ω'-diisocyanate-1,4-diethylbenzene, Examples thereof include 1,4-tetramethylxylylene diisocyanate and 1,3-tetramethylxylylene diisocyanate.

The alicyclic polyisocyanate includes, for example, 3-isocyanate methyl-3,5,5-trimethylcyclohexylisocyanate, 1,3-cyclopentanediisocyanate, 1,3-cyclohexanediisocyanate, 1,4-cyclohexanediisocyanate, methyl-2, Examples include 4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, 4,4'-methylenebis (cyclohexylisocyanate), 1,4-bis (isocyanatemethyl) cyclohexane, and 1,4-bis (isocyanatemethyl) cyclohexane. Be done.

In addition, an isocyanate prepolymer may be used as the polyisocyanate. The isocyanate prepolymer is made from diisocyanate as a raw material and prepolymerized so that the content of the monomer is 1% or less. Isocyanate prepolymers include adducts, biurets, and isocyanurates.
The adduct is an adduct of diisocyanate and trimethylolpropane (CH _3- CH _2- C (CH _2- OH) ₃ ). The biuret is a reaction of diisocyanate with water or a tertiary alcohol. The isocyanurate form is a trimer of diisocyanate (this trimer contains an isocyanurate ring).

As the polyisocyanate (y), 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexylisocyanate (isophorone diisocyanate) and the like are preferable.

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 the hydroxyl group exceeds the number of moles of the isocyanate group. The ratio (NCO / OH 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) is preferably 0.30 to 0.95, more preferably 0.5 to 0.5 to 0.95. It is 0.90. When the hydroxyl group and the isocyanate group are reacted at an appropriate ratio, both cohesive force and adhesive force can be highly compatible.

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). The polyisocyanate (y) may contain one or more trifunctional or higher functional isocyanate compounds, if necessary.
When only a trifunctional or higher functional polyol having high crosslinkability and only a trifunctional or higher functional 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 preferable range. There is a risk.
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 suppress excessive cross-linking and obtain an adhesive layer having suitable cohesive force and adhesive force.

<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 the organometallic compound include tin-based compounds and non-tin-based compounds.
Examples of tin compounds include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimalate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, and tributyltin. Examples thereof include acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, dioctyltin dilaurate, tributyltin chloride, tributyltin trichloroacetate, tin 2-ethylhexanoate and the like.
Non-tin compounds are titanium-based compounds such as, for example, dibutyltitanium dichloride, tetrabutyl titanate, and butoxytitanium trichloride; lead-based compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; Iron-based substances such as iron 2-ethylhexanoate and iron acetylacetonate; cobalt-based substances such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc-based substances such as zinc naphthenate and zinc 2-ethylhexanoate; zirconium naphthenate and the like. Zirconium system can be mentioned.

One or more catalysts can be used. When the reactivity of each of the plurality of types of polyols (x) used in combination as necessary is different, gelation or clouding of the reaction solution may easily occur in a single catalyst system due to the difference in these reactivity. In this case, by using two types of catalysts, the reaction (for example, reaction rate) can be easily controlled, and the above problem can be solved. The combination of the two types of catalysts is not particularly limited, and examples thereof include tertiary amine / organometallic, tin-based / non-tin-based, and tin-based / tin-based. It is preferably tin-based / tin-based, more preferably dibutyltin dilaurate and tin 2-ethylhexanoate.
The mass ratio of tin 2-ethylhexanoate to dibutyltin dilaurate (tin 2-ethylhexanoate / dibutyltin dilaurate) is not particularly limited, and is preferably more than 0 and less than 1, more preferably 0.2 to 0.6. be. When the mass ratio is less than 1, the catalytic activity is well-balanced, gelation and white turbidity of the reaction solution are effectively suppressed, and the polymerization stability is further improved.

The amount of one or more catalysts used is not particularly limited, and is preferably 0.01 to 1% by mass with respect to the total amount of the polyol (x) and the polyisocyanate (y).

<Solvent>
If necessary, a solvent can be used for the synthesis of the polyurethane resin (A). Examples of the solvent include methyl ethyl ketone, ethyl acetate, toluene, xylene, acetone and the like. Ethyl acetate, toluene and the like are particularly preferable from the viewpoint of the solubility of the polyurethane resin (A) and the boiling point of the solvent.

<Polymerization method>
The polymerization method of the polyurethane resin (A) is not particularly limited, and known polymerization methods such as a massive polymerization method and a solution polymerization method can be applied.
The polymerization procedure is not particularly limited.
Step 1) A procedure in which the polyol (x), the polyisocyanate (y), the catalyst if necessary, and the solvent as needed are collectively charged into the flask;
Step 2) Examples thereof include a procedure in which the polyol (x), a catalyst if necessary, and a solvent if necessary are charged into a flask, and polyisocyanate (y) is added dropwise thereto.
Procedure 2) is preferable because the reaction can be easily controlled.

When a catalyst is used, the reaction temperature is preferably less than 100 ° C, more preferably 80 to 90 ° C. When the reaction temperature is less than 100 ° C., the reaction rate, the crosslinked structure and the like can be easily controlled, and the polyurethane resin (A) having a desired molecular weight can be easily produced.
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 higher.

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. When the Mw of the polyurethane resin (A) is in an appropriate range, good coatability can be easily obtained.

(Isocyanate curing agent (B))
The isocyanate curing agent (B) is a compound exemplified by the polyisocyanate (y) which is a raw material of the polyurethane resin (A) (specifically, aromatic polyisocyanate, aliphatic polyisocyanate, aromatic aliphatic polyisocyanate, alicyclic). Group polyisocyanates and their trimethylol propanadduct / burette / trimeric) can be used.

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. When the amount of the polyfunctional isocyanate (B) is 1 part by mass or more, the cohesive force of the adhesive layer is good, and when 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 to each other, and the linking group is a compound having a branched structure, which is a reaction product of the polyol (c1) and a monobasic acid. be. The pressure-sensitive adhesive containing the ester (C) has an effect of improving low temperature suitability in addition to improving removability and wettability. The reason for this effect is that the ester (C) has a lower density of clusters formed between the esters (C) due to steric hindrance of the branched structure, or the clusters of the ester (C) are lower than those of the ester having no branched structure. It is presumed that because the size is small, clusters are unlikely to grow in a low temperature environment, and an appropriate compatibility can be maintained in the adhesive layer, so 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 has a branched structure and an ester bond having an average of 2 or more. If the lower limit is forced, 300 or more is preferable, and 350 or more is more preferable. In the present specification, the molecular weight (formula weight) is the formula weight when the molecular structure of the ester (C) can be specified by a chemical formula. When the ester (C) does not have a single structure and has a molecular weight distribution, the number average molecular weight is used.

The number of ester bonds contained in the ester (C) is preferably 2 to 4, more preferably 2 to 3.
The branched structure of the ester (C) means, for example, that the linking group connecting the two ester bonds has a branched structure, and can have one 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 a branched structure and two or more hydroxyl groups. The number of hydroxyl groups of the polyol (c1) is not limited as long as two or more ester bonds can be formed, and 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 functional polyols. In the present specification, the bifunctional polyol means a polyol having two hydroxyl groups.

Bifunctional polyols of alkylene polyols having a branched structure include, for example, 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-Decandiol.
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 polyols having a bifunctional polyol or a trifunctional polyol 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 leucauline.

The monobasic acid is a compound having one carboxyl group, and a fatty acid is preferable. The number of carbon atoms of the fatty acid is preferably 4 to 24, more preferably 4 to 18, further preferably 6 to 18, and particularly preferably 6 to 12. When the number of carbon atoms is 4 or more, the wettability is further improved, and when the number of carbon atoms is 24 or less, the low temperature suitability is further improved.

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

Examples of commercially available esters (C) include Highsolve MMPOM (propylene glycol dimethyl ether), Highsolve MDPOM (propylene glycol dimethyl ether), Highsolve MTPOM (tripropylene glycol dimethyl ether) manufactured by Toho Chemical Industry Co., Ltd .; manufactured by Nisshin Oillio Co., Ltd. Saracos PR-85 (di (caprylic acid / capric acid) propanediol), Saracos PR-17 (propanediol diisostearate), Estemoll N-01 (neopentyl glycol di2-ethylhexanoate), T.I. I. O (glyceryl tri2-ethylhexanoate), O.D. D. O (tri (capryl / capric acid) glyceryl), Saracos 6318V (trimethylolpropane triisostearate), Saracos 5408 (pentaerythricyltetra2-ethylhexanoate), Saracos 5418V (pentaerythrityl tetraisostearate), etc.; RIKEN 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); Kao's products include Exepearl BP-DL (polyoxyethylene bisphenol A lauric acid ester), Exepearl PE-TP (pentaerythritol tetrapalmitate), etc. Can be mentioned.

Further, it is preferable that the ester (C) does not have a hydroxyl group in the linking group. This is because when the ester (C) has a hydroxyl group, the cross-linking reactivity between the polyurethane resin (A) and the isocyanate curing agent (B) may decrease, and the removability may decrease.

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, still more preferably 5 to 60 parts by mass, based on 100 parts by mass of the polyurethane resin (A). 10 to 55 parts by mass is particularly preferable, and 15 to 50 parts by mass is most preferable. When an appropriate amount of ester (C) is used, in addition to improving removability and wettability, low temperature suitability is further improved.

(solvent)
The pressure-sensitive adhesive of the present invention may 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, acetone and the like. 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 kinds of deterioration inhibitor (D), if necessary. As a result, deterioration of various properties due to long-term use of the adhesive layer can be suppressed. Examples of the alteration inhibitor (D) include a hydrolysis resistant agent, an antioxidant, an ultraviolet absorber, a light stabilizer and the like.

<Hydrolytic agent>
When a hydrolysis reaction occurs in the adhesive layer in a high temperature and high humidity environment to generate a carboxy group, a hydrolysis resistant agent can be used to block the carboxy group.
Examples thereof include hydrolysis resistant agents, carbodiimide-based, isocyanate-based, oxazoline-based, and epoxy-based. Among these, the carbodiimide type is preferable from the viewpoint of the hydrolysis inhibitory 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 decarboxylating and condensing diisocyanate in the presence of a carbodiimidization catalyst. The diisocyanate is, for example, 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate. , 3,3'-dimethyl-4,4'-diphenyl ether diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4' -Dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate and the like can be mentioned. Carbodiimide catalysts include, for example, 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 1-ethyl-. Examples thereof include 2-phospholen-1-oxide and phosphorene oxides such as these 3-phosphoren isomers.

Examples of the isocyanate-based hydrolysis inhibitor include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylenedi isocyanate, p-phenylenedi isocyanate, 4,4'-diphenylmethane diisocyanate, and 2,4'-diphenylmethane. Diisocyanate, 2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylenediocyanate, 3,3'-dimethoxy-4,4'-biphenylenediisocyanate, 3,3'-dichloro-4,4 '-Biphenylenediocyanate, 1,5-naphthalenediocyanate, 1,5-tetrahydronaphthalenediocyanate, tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1,3-cycloheximethylene diisocyanate, 1,3-cyclohexamethylene diisocyanate, 1 , 4-Cyclohexamethylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and 3,3'-dimethyl-4,4' − Dicyclohexamethylene diisocyanate and the like.

Examples of the oxazoline-based hydrolysis inhibitor include 2,2'-o-phenylenebis (2-oxazoline), 2,2'-m-phenylenebis (2-oxazoline), and 2,2'-p-phenylenebis (2,2'-p-phenylenebis (2-oxazoline). 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'-tetramethylenebis (2-oxazoline), 2,2'-hexamethylenebis (2-oxazoline), 2,2'-octamethylenebis (2-oxazoline), 2,2'-ethylenebis (2,2'-ethylenebis (2-oxazoline) 4-Methyl-2-oxazoline), 2,2'-diphenylenebis (2-oxazoline) and the like.

Epoxy hydrolysates include 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 group or aromatic polyvalent carboxylic acids; resorcinol, bis- (p-hydroxyphenyl) methane, 2,2-bis- (p-hydroxyphenyl) propane, tris- (p-hydroxy) Diglycidyl ethers or polyglycidyl ethers of polyhydric phenols such as phenyl) methane and 1,1,2,2-tetrakis (p-hydroxyphenyl) ethane; N, N-diglycidylaniline, N, N-diglycidyl toluidin. , And N-glycidyl derivatives of amines such as N, N, N', N'-tetraglycidyl-bis- (p-aminophenyl) methane; triglycidyl derivatives of aminoferrs; triglycidyltris (2-hydroxyethyl) isocia Nurate and triglycidyl isocyanurate; examples thereof include epoxy resins such as orthocresol type epoxy resins and phenol novolac type epoxy resins.

The amount of the hydrolysis resistant agent added 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 0.2 to 4.5 parts by mass, based on 100 parts by mass of the polyurethane resin (A). Is 0.5 to 3 parts by mass.

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

The phenolic compounds include, for example, 2,6-di-t-butyl-p-cresol, butylated hydroxyanisol, 2,6-di-t-butyl-4-ethylphenol, stea-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-t-butylphenol), 4,4'-butylidenebis (3-methyl-6-t-butylphenol), 3,9-bis [1,1-dimethyl-2-[1,1-dimethyl-2- [ β- (3-t-Butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro [5,5] undecane, benzenepropanoic 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-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3', 5'-di-t-butyl-) 4'-Hydroxyphenyl) propionate] methane, bis [3,3'-bis- (4'-hydroxy-3'-t-butylphenyl) butyl acid] glycol ester, 1,3,5-tris (3' , 5'-di-t-butyl-4'-hydroxybenzyl) -S-triazine-2,4,6- (1H, 3H, 5H) trione, tocophenol and the like.

Phenyl compounds include, for example, triphenylphosphite, diphenylisodecylphosphite, 4,4'-butylidene-bis (3-methyl-6-tert-butylphenylditridecyl) phosphite, cyclic neopentanetetraylbis. (Octadecylphosphite), tris (nonylphenyl) phosphite, tris (monononylphenyl) phosphite, tris (dinonylphenyl) phosphite, diisodecylpentaerythritol diphosphite, 9,10-dihydro-9-oxa-10 -Phenylphenyl-10-oxide, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10- Desiroxy-9,10-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, and 2,2-methylenebis (4,6-di-tert-butylphenyl) Examples include octylphosphite.

By using an antioxidant, it is possible to prevent thermal deterioration of the polyurethane resin (A) and more effectively suppress bleeding out of the ester (C) from the adhesive layer.
The amount of the antioxidant added 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, with respect to 100 parts by mass of the polyurethane resin (A). It is 2 to 2 parts by mass.

From the viewpoint of stability and antioxidant effect, it is preferable to use one or more phenolic compounds which are radical catching agents, and one or more phenolic compounds which are radical catching agents and peroxide decomposing agents. It is more preferable to use one or more phosphorus compounds in combination. Further, as the antioxidant, it is particularly preferable to use a phenol-based compound as a radical supplement and a phosphorus-based compound as a peroxide decomposing agent in combination, and to use these antioxidants in combination with the above-mentioned hydrolysis resistant agent. ..

<UV absorber>
Examples of the ultraviolet absorber include benzophenone-based compounds, benzotriazole-based compounds, salicylic acid-based compounds, oxalic acid anilides-based compounds, cyanoacrylate-based compounds, and triazine-based compounds.
The amount of the ultraviolet absorber added is not particularly limited, and is preferably 0.01 to 3 parts by mass, more preferably 0.1 to 2.5 parts by mass, and particularly preferably 0.1 to 2.5 parts by mass with respect to 100 parts by mass of the polyurethane resin (A). It is 0.2 to 2 parts by mass.

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

(Antistatic agent (E))
The pressure-sensitive adhesive of the present invention may contain one or more antistatic agents (E), if necessary.
Examples of the antistatic agent include inorganic salts, polyhydric alcohol compounds, ionic liquids, surfactants and the like, and among them, ionic liquids are preferable. The "ionic liquid" is also called a room temperature molten salt, which is a salt having 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, pentaerythritol and the like.

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 thereof include 3-methylimidazolium bis (trifluoromethylsulfonyl) imide.

Ionic liquids containing pyridinium ions include, for example, 1-methylpyridinium bis (trifluoromethylsulfonyl) imide, 1-butylpyridinium bis (trifluoromethylsulfonyl) imide, 1-hexylpyridinium bis (trifluoromethylsulfonyl) imide, 1 − 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) imide, and 1-methylpyridinium bis (perfluorobutylsulfonyl) Examples include imide.

Ionic liquids containing ammonium ions include, for example, trimethylheptyl ammoniumbis (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 And so on.

In addition, commercially available ionic liquids such as pyrrolidinium salt, phosphonium salt, and sulfonium salt can be appropriately used.

Surfactants are classified into low molecular weight surfactants and high molecular weight surfactants. Both types include nonionic, anionic, cationic, and amphoteric types.

Nonionic low molecular weight surfactants include glycerin fatty acid ester, polyoxyalkylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl amine, polyoxyethylene alkyl amine fatty acid ester, fatty acid diethanolamide and the like. ..
Examples of the anionic small molecule surfactant include alkyl sulfonates, alkylbenzene sulfonates, alkyl phosphates and the like.
Examples of the cationic small molecule surfactant include tetraalkylammonium salts and trialkylbenzylammonium salts.
Examples of amphoteric small molecule surfactants include alkyl betaine and alkyl imidazolium betaine.

Examples of the nonionic polymer surfactant include a polyether ester amide type, an ethylene oxide-epichlorohydrin type, and a 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 amphoteric polymer surfactants include amino acid-type amphoteric surfactants such as higher alkylaminopropionate, higher alkyldimethylbetaine, and betaine-type amphoteric surfactants such as higher alkyldihydroxyethyl betaine.

The amount of the antistatic agent (E) added is preferably 0.01 to 10 parts by mass, and 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 may contain a leveling agent, if necessary. By adding the leveling agent, when the pressure-sensitive adhesive is applied, the surface tension of the coating film is lowered, and it becomes easy to obtain a pressure-sensitive adhesive layer having a smooth surface. Examples of the leveling agent include an acrylic leveling agent, a fluorine-based leveling agent, and a silicone-based leveling agent. From the viewpoint of suppressing adhesion contamination after re-peeling of the adhesive sheet, an acrylic-based leveling agent or the like is 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 contamination of the surroundings is suppressed. When Mw is 20,000 or less, the effect of improving the leveling property of the adhesive layer is effectively exhibited.

The amount of the leveling agent added is not particularly limited, and is preferably 0.001 with respect to 100 parts by mass of the polyurethane resin (A) from the viewpoint of suppressing adhesion contamination after re-peeling the pressure-sensitive adhesive sheet and improving the leveling property of the pressure-sensitive adhesive layer. It is ~ 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)
The pressure-sensitive adhesive of the present invention may contain other arbitrary components as long as the problems of the present invention can be solved. 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-resistant stabilizers, weather-resistant stabilizers, polymerization inhibitors, defoaming agents and the like.

"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 above-mentioned pressure-sensitive adhesive of the present invention. The adhesive layer can be formed on one side or both sides of the base material. If necessary, the exposed surface of the adhesive layer can be covered with a release sheet. The release sheet is peeled off when the adhesive sheet is attached to the adherend. The base material is preferably in the form of a sheet.

FIG. 1 shows a schematic cross-sectional view of the pressure-sensitive adhesive sheet according to the first embodiment of the present invention. 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 an pressure-sensitive adhesive layer is formed on one side of a base material.
FIG. 2 shows a schematic cross-sectional view of the pressure-sensitive adhesive sheet according to the second embodiment of the present invention. 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 sides of a base material.

The base material is not particularly limited, and examples thereof include a resin sheet, paper, and a metal foil. The base material may be a laminated sheet in which any one or more layers are laminated on at least one surface of these base materials. If necessary, the surface of the base material on the side where the adhesive layer is formed may be subjected to an easy-adhesion treatment such as a corona discharge treatment and an anchor coating agent application.

The constituent resin of the resin sheet is not particularly limited, and for example, an ester resin such as polyethylene terephthalate (PET); an olefin resin such as polyethylene (PE) and polypropylene (PP); a vinyl resin such as polyvinyl chloride; nylon 66 and the like. Amid resin; urethane resin (including foam); a combination thereof and the like can be mentioned.
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 the 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 metals of the metal foil are 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 has a high degree of freedom in selecting the base material to be used, which is preferable.

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

The pressure-sensitive adhesive sheet can be produced by a known method.
First, the pressure-sensitive adhesive of the present invention is applied to the surface of the base material 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 heating and drying temperature is not particularly limited, and is preferably about 60 to 150 ° C.
The thickness of the adhesive layer can be appropriately designed depending on the use of the adhesive sheet, and is, for example, about 5 to 300 μm. In the present specification, the "thickness of the adhesive layer" is the 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.
As described above, the single-sided adhesive sheet can be manufactured.
By performing the above operation on both sides, a double-sided adhesive sheet can be manufactured.

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 obtain 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 base material 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 personal digital assistant, and a display mounted on a vehicle, that is, a CID (Center Information Display) and a car navigation system. The CID refers to an information display arranged in front of the driver's seat of an automobile. In the past, it was installed mainly for car navigation map display, but in recent years it has become more sophisticated as a parking assist function by installing an in-vehicle camera and a multifunction display that displays air conditioning operation and fuel consumption information, so it can be used in any environment. The aptitude is required.

Examples of the material of the surface (adhesive 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, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass". The blending amount in the table is a mass part.

[Measurement of molecular weight]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured by the gel permeation chromatography (GPC) method. The measurement conditions are as follows. Both Mw and Mn are polystyrene-equivalent values.
Equipment: SHIMADZU Prominence (manufactured by Shimadzu Corporation),
Column: SHODEX LF-804 (manufactured by Showa Denko KK) connected in series,
Detector: Differential refractometer,
Solvent: tetrahydrofuran (THF),
Flow velocity: 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, number of hydroxyl groups 2, manufactured by Kuraray Co., Ltd.),
(X1-2): Kuraray polyol C-1090 (polycarbonate polyol, number average molecular weight Mn1000, number of hydroxyl groups 2, manufactured by Kuraray Co., Ltd.),
(X1-3): PEG-1000 (polyether polyol, number average molecular weight Mn1000, number of hydroxyl groups 2, manufactured by Toho Chemical Industry Co., Ltd.),

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

<Polyisocyanate (y)>
(Y-1): Death module H (hexamethylene diisocyanate, manufactured by Sumika Cobestrolethane),
(Y-2): Death Module I (isophorone diisocyanate, manufactured by Sumika Cobestrolethane),
(Y-3): Coronate T-65 (Tosoh isocyanate, manufactured by Tosoh Corporation),

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

<Ester (C)>
(C-1): Estemoll N-01 (neopentyl glycol di2-ethylhexanoate), molecular weight 356, monobasic acid carbon number 8, ester bond number 2, linking group is branched structure / aliphatic, Nisshin Made by Oillio),
(C-2): T.I. I. O (glyceryl tri2-ethylhexanoate, molecular weight 470, carbon number 8 of monobasic acid, number of ester bonds 3, branched structure / aliphatic as linking group, manufactured by Nisshin Oillio 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, number of ester bonds 3, linking group has a branched structure. Aliphatic, manufactured by Riken Vitamin Co., Ltd.),
(C-4): Riquemar O-71-D (diglycerin oleate, molecular weight 620, fatty acid carbon number 18, ester bond number 2, linking group is branched structure / aliphatic, manufactured by Nisshin Oillio Co., Ltd.),
(C-5): Exepearl BP-DL (polyoxyethylene bisphenol A lauric acid ester, molecular weight 678, monobasic acid having 12 carbon atoms, ester bond number 2, linking group having a branched structure / aromatic, manufactured by Kao Co., Ltd.),
(C'-1): Sansosizer DINA (diisononyl adipate, ester molecular weight of dibasic acid and monoalcohol 398, number of ester bonds 2, linking group is linear structure / aliphatic, manufactured by Shin Nihon Rika Co., Ltd.)
(C'-2): TOTM (trimellitic acid (2-ethylhexyl), ester of tribasic acid and monoalcohol, molecular weight 547, number of ester bonds 3, linking group is branched structure / aromatic, manufactured by Mitsubishi Chemical Co., Ltd.) ,
(C'-3): Sansosizer E-6000 (epoxidized fatty acid 2-ethylhexyl, molecular weight about 400, number of ester bonds 1, linking group is linear structure / aliphatic, manufactured by Shin Nihon Rika Co., Ltd.).

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

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

(Synthesis Example 1)
25 parts of bifunctional polyol (x1-1), 75 parts of trifunctional polyol (x2-1), and bifunctional in a 4-port flask equipped with a stirrer, reflux condenser, nitrogen introduction tube, thermometer, and dropping funnel. 7.4 parts of polyisocyanate (y-1) (amount of NCO / OH of 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 a catalyst, the temperature was gradually raised to 90 ° C., and the reaction was carried out at 90 ° C. for 2 hours. Sampling was performed as needed, and after confirming the disappearance of the residual isocyanate group on the infrared absorption (IR) spectrum, the reaction solution was cooled to terminate the reaction. As described above, a solution of the polyurethane resin (A-1) (nonvolatile content: 60%) was obtained. The Mw of the obtained polyurethane resin (A-1) was 226,000. The compounding composition and the Mw of the obtained polyurethane resin (A-1) are shown in Table 1-1.
The method for calculating the amount of the 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)) ×
[(Part of (x1-1)) / (Molecular weight of (x1-1)) x (Number of hydroxyl groups of (x1-1))
+ (Part of (x2-1)) / (Molecular weight of (x2-1)) x (Number of hydroxyl groups of (x2-1))]]
= 0.7 × 168/2 × (2/1000 × 2 + 98/10000 × 3)
≒ 7.4 copies

(Synthesis Examples 2-8)
Solutions of polyurethane resins (A-2) to (A-8) were obtained in Synthesis Examples 2 to 8 in the same manner as in Synthesis Example 1 except that the composition was changed to the composition shown in Table 1-1. Table 1 shows the Mw of the obtained polyurethane resin in each synthetic example.

(Example 1)
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 (antioxidant) A urethane-based pressure-sensitive adhesive was obtained by blending 1.0 part of D-1), further blending 100 parts of ethyl acetate as a solvent, and stirring with a disper.
As a base material, a 50 μm-thick polyethylene terephthalate film (PET film, Lumirer T-60: manufactured by Toray Industries, Inc.) was prepared. The obtained pressure-sensitive adhesive was applied to one side of this base material 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. A release sheet having a thickness of 38 μm (Super Stick SP-PET38: manufactured by Lintec Corporation) was attached onto this adhesive layer 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, the pressure-sensitive adhesive and the pressure-sensitive adhesive sheet were obtained in the same manner as in Example 1 except that the compounding composition was changed as shown in Tables 2 to 5. rice field.

[Evaluation items and evaluation methods]
The evaluation items and evaluation methods are as follows.
(Removability)
The obtained adhesive sheet was prepared to a size of 25 mm in width and 100 mm in length, and used as a measurement sample. Then, in an atmosphere of 23 ° C.-50% RH, the release sheet was peeled off from the measurement sample, 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 the condition of 60 degreeC-90% RH. After air-cooling in an atmosphere of 23 ° C.-50% RH for 30 minutes, it adheres under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180 ° using a tensile tester (Tencilon: manufactured by Orientec) in accordance with JISZ0237. The force was measured. The lower the adhesive strength, the easier it is to peel off again. The evaluation criteria are as follows.
◯: Less than 50 mN / 25 mm, good.
Δ: 50 mN / 25 mm or more, 200 mN / 25 mm, practically possible.
X: Over 200 mN / 25 mm, not practical.

(Wetness)
The obtained adhesive tape was prepared to a size of 50 mm in width and 100 mm in length, and used as a measurement sample. Then, after leaving it for 30 minutes in a 23 ° C.-50% RH atmosphere, the release sheet was peeled off from the measurement sample. While holding both ends of the adhesive tape with both hands, the central portion of the exposed adhesive layer was brought into contact with the glass plate, and then both hands were released. The wettability of the adhesive was evaluated by measuring the time until the entire adhesive layer adhered to the glass plate by the weight of the measurement sample. The shorter the time required for the glass to come into close contact with the glass plate, the better the wettability (affinity) with respect to the glass. Therefore, the glass can be well protected in the manufacturing process using the glass. The evaluation criteria are as follows.
◯: Good contact in less than 3 seconds.
Δ: 3 seconds or more and less than 5 seconds until close contact, practical use is possible.
X: Not practical for 5 seconds or more until close contact.

(Resistance stability)
The obtained 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 in which an ITO transparent conductive film having a thickness of 5 μm was formed was bonded and fixed. A test piece having a laminated structure of PET film / adhesive layer / ITO film was obtained by applying a pressure of 5 MPa and holding 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]. Further, after the test piece is left to stand for 72 hours under the condition of 60 ° C.-90% RH, the electric resistance value after aging is measured in the same manner as described above, and the resistance value stability is determined by the electric resistance change rate (electrical resistance value after aging / initial stage). (Electrical resistance value) was evaluated. The evaluation criteria are as follows. ⊚: The rate of change in electrical resistance is less than 1.2, which is excellent.
◯: The rate of change in electrical resistance is 1.2 or more and less than 1.5, which is good.
Δ: The rate of change in electrical resistance is 1.5 or more and less than 2, practically possible.
X: The rate of change in electrical resistance is 2 or more, which is not practical.

(Low temperature stability)
The obtained adhesive sheet was prepared to a size of 70 mm in width and 100 mm in length and used as a measurement sample. Then, in an atmosphere of 23 ° C.-50% RH, the release sheet was peeled off from this measurement sample, and the exposed adhesive layer was attached to a caustic soda glass plate. Then, it was left for 2 weeks under the condition of -15 ° C. After air-cooling in an atmosphere of 23 ° C.-50% RH for 3 hours, the measurement sample is peeled off from the glass plate, and the LED lamp is placed under a fluorescent lamp or in a dark room on the part where the measurement sample is attached to the glass surface. The bleeding condition of the wetting agent was visually evaluated by irradiating with light. The evaluation criteria are as follows.
◯: Good, with no change on the glass surface.
Δ: A slight change like oil stain is observed on the glass surface in a dark room, which is practical.
X: A rainbow-colored pattern is visually observed on the glass surface under a fluorescent lamp, which is not practical.

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

From the results of Tables 2 to 5, Examples 1 to 22 contain a polyurethane resin (A), an isocyanate curing agent (B), and an ester (C) which is a reaction product of a 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.

All of the adhesive sheets obtained in Examples 1 to 22 have removability after storage under 60 ° C.-90% RH conditions, wettability to glass, and 60 ° C.-90% when used for a transparent conductive film. The evaluation results of the resistance value stability after storage under RH conditions and the low temperature stability after storage under -15 ° C. conditions were good.

When the pressure-sensitive adhesive sheet is used, for example, for surface protection of a transparent conductive film, the resistance value may deteriorate if the pressure-sensitive adhesive layer contains an acid component. Therefore, by using an ester (C) using a polyol as a starting material as a linking group, it was possible to suppress the content of an unreacted acid component which is an impurity and 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 evaluation results of resistance value stability after storage under 60 ° C.-90% RH conditions and low-temperature stability after storage under -15 ° C. conditions. rice field.

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 evaluation results of resistance value stability after storage under 60 ° C.-90% RH conditions and low-temperature stability after storage under -15 ° C. conditions. rice field.

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

Claims (6)

The ester (C) contains a polyurethane resin (A), an isocyanate curing agent (B), and an ester (C) which is a reaction product of a polyol (c1) and a monobasic acid, and the ester (C) has a molecular weight of 300 to 600. The ester (C) has two or more ester bonds and a linking group that connects the ester bonds to each other, the linking group has a branched structure, and the monobasic acid is a fatty acid. Agent. The pressure-sensitive adhesive according to claim 1, wherein the ester (C) is contained in an amount of 0.5 to 80 parts by mass with respect to 100 parts by mass of the polyurethane resin (A). The pressure-sensitive adhesive according to claim 1 or 2, wherein the polyol (c1) is an aliphatic polyol having a branched structure. The pressure-sensitive adhesive according to any one of claims 1 to 3, which contains 1 to 30 parts by mass of the isocyanate curing agent (B) with respect to 100 parts by mass of the polyurethane resin (A). The pressure-sensitive adhesive according to any one of claims 1 to 4 , further comprising an antistatic agent (E). A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer which is a cured product of the pressure-sensitive adhesive according to any one of claims 1 to 5.